Skills Experiments Carol Andrews Satya Naidu Greg Laidler

Book 1

OXFORD UNIVERSITY PRESS AUSTRALIA & NEW ZEALAND

OXFORD UNIVERSITY PRESS AUSTRALIA & NEW ZFAlAND

253 Normanby Road, South Melbourne, Victoria 3205, Australia Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Sao Paulo Shanghai Taipei Tokyo Toronto OXFORD is a trade mark of Oxford University Press in the UK and in certain other countries © Greg Laidler, Carol Andrews, Satya Naidu 2002 First published 2002 Reprinted 2004,2007,2008,2009 This book is copyright. Apart from any fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act, no part may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior written permission. Enquiries to be made to Oxford University Press.

Copying for educational purposes Where copies of part or the whole of the book are made under Part VB of the Copyright Act, the law requires that prescribed procedures be followed. For information, the Copyright Agency Limited. National Library of Australia Cataloguing-in-Publication data: Andrews, Carol, 1958Active science: skills and experiments. Includes index. For teachers of and year 7 students. ISBN 9780195514407 (bk. 1: Student workbook). ISBN 0195514408 (bk. 1: Student workbook). ISBN 9780195514469 (bk. 1: Teacher's answer book). ISBN 019 551446 7 (bk. 1: Teacher's answer book). 1.Science-Problems, exercises, etc.-Juvenile literature. I. Laidler, Greg. II. Naidu, Satya. III. Title. 500 Typeset by Kae Sato Goodsell and OUPANZ Printed in China by Golden Cup Printing Co. Ltd

Risk Assessment Theexperimentsanddemonstrationsinthisbookwerewrittenwiththesafetyofthestudentsinmind.Ineverycasetheleast harmful substances available have been used. However, normal precautions should betaken. The RiskAssessmentsheets (provided on the teacher's CD) are a guide only and teachers and schools are advised to conducttheir own assessment on therisksinvolvedin these activities. Neitherthepublishernortheauthors acceptresponsibliltyfor anyinjurysustained when conducting experiments and demonstrations.

Contents Acknowledgments

iv

Biological Science

Preface

1

Chapter 5: Cells

Skills, Processes and Procedures Chapter 1: Starting Science 1.1 What is science? 1.2 Playing it safe 1.3 Working in the laboratory 1.4 Laboratory equipment 1.5 Keeping records 1.6 Dissolving and filtering 1.7 Investigations 1.8 Measurements 1.9 Mind maps Review and research

2 4 6 8 10 12 14 16 18 20

Chapter 2: Investigating 2.1 Being observant 2.2 Showing data: tables and histograms 2.3 Showing data: graphs 2.4 Observation, inference and hypothesis 2.5 How to do a fair experiment Review and research

24 26 28 30 32 34

Chapter 3: The Particle Theory 36 38 40 42 44 46 48 50

Chapter 6: Classification of Living Things 88 90 92 94 96 98 100 102 105

6.1 Living things 6.2 Sorting into groups 6.3 Using keys 6.4 Kingdoms of living things 6.5 The plant kingdom 6.6 The animal kingdom 6.7 Vertebrates 6.8 Invertebrates Review and research

Physical Science 108 110 112 114 116 118 120 122 124 .

7.1 Why objects move 7.2 Friction 7.3 More about forces 7.4 Magnets and magnetic force 7.5 Magnetic fields 7.6 Types and uses of magnets 7.7 Static electricity 7.8 Sparks and lightning Review and research

Chapter 8: Heat, Light and Sound Energy

Chapter 4: Separating Mixtures 4.1 Why separate? 4.2 Filtering and sieving 4.3 Magnetic separation 4.4 Sedimentation and flotation 4.5 Chromatography 4.6 Adsorption 4.7 Electrostatic separation 4.8 Distillation 4.9 Physical and chemical changes Review and research

72

74 76 78 80 82 84 86

Chapter 7: Forces-Pushes and Pulls

Chemical Science 3.1 States of matter 3.2 The particle theory 3.3 Properties of matter 3.4 More about the particle theory 3.5 Energy in particles 3.6 Particles and pressure 3.7 Effects of heat Review and research

70

5.1 Spontalfeous generation 5.2 What are cells? 5.3 Cell organisation 5.4 Microscopes 5.5 Using a compound microscope 5.6 Looking into cells 5.7 Unicellular organisms 5.8 Cancer Review and research

52 53 54 56 58 60 62 64 66 68

126 128 132 135 138

8.1 Energy forms 8.2 Heat energy 8.3 Light energy 8.4 Sound energy Review and research

(continued ... )

Contents

I

iii

Earth and Space Science Chapter 9: Wearing Away the Earth 9.1 Wearing away rocks 9.2 The effects of weathering 9.3 Landscapes caused by erosion 9.4 Rocks made by erosion 9.5 Preventing erosion; soil composition Review and research

140 142 144 146 148 150

Chapter 10: Our Neighbours in Space 10.1 Ancient astronomy 10.2 Our solar system 10.3 How the Earth moves in space 10.4 Time 10.5 The Moon 10.6 Solar and lunar eclipses 10.7 Constellations Review and research

152 154 160 162 164 166 168 170

Glossary

172

Index

186

Acknowledgments The authors would like to acknowledge the of their families and the input of their colleagues Sylvia Zula, Neelam Berera and Pam Robinson. Thanks also to Ian Harding and Emma Holder for their invaluable input and during the development of Active Science. The authors and publishers wish to thank copyright holders for granting permission to reproduce illustrative material. Sources are as follows: Age Photo Library, p. 22 (top centre & bottom); Agricultural Research Service (US Department of Agriculture), p. 76 (Figs 5.4.1B & C); Andrew Gleadow, p. 55 (Fig 4.3.3), p. 123 (Fig 7.8.3); Bruce Fuhrer, p. 95 (Figs 6.4.2A & C); Coo-ee Picture Library, p. 22 (top left); Corel Corporation, p. 61 (Fig 4.6.3), p. 162 (Fig 10.4.2); David Meagher, p. 95 (Fig 6.4.2B); Greg Laidler, p. 43 (Fig 3.4.2), p. 48 (Fig 3.7.1), p.142 (Fig 9.2.2), p. 146 (Figs 9.4.1A-D), p. 164 (Fig 10.5.2); NASA, p. 154 (Fig 10.2.1), p. 155 (Figs 10.2.2 & 10.2.3), p. 156 (Figs 10.2.4 & 10.2.5), p. 157 (Figs 10.2.6-8); Lyn Beazley, p. 22 (top right); Photo disk, p. 2 (Fig 1.1.2), p. 76 (Fig 5.4.1A) The Picture Source, p. 2 (Fig 1.1.3), p. 81 (Fig 5.6.2). Every effort has been made to trace the original source of the copyright material contained in this book. The publisher would be pleased to hear from copyright holders to rectify any errors or omissions.

iv

I

Contents

Preface Active Science: Skills and Experiments is an activity-driven approach to junior science. Book 1 offers a complete course for the first year of secondary school. Topics within each chapter are presented in a double page format. Topics offer a concise summary of the theory, clear diagrams, science facts, write-in activities, fill-in questions, and demonstrations and practical experiments with scientific reports to fill in. Review and research activities at the end of each chapter consolidate the topics taught and encourage further research. The glossary includes the key words listed at the end of each chapter. Active Science: Skills and Experiments Book 1 is organised into five strands: • Skills, Processes and Procedures • Chemical Science • Biological Science • Physical Science • Earth and Space Science Active Science: Skills and Experiments Teacher's Answer Book and CD includes the complete student's text with answers provided in a second colour. To assist teachers in the implementation of this material, state syllabus references have been provided on the bottom of each page, as a guide only, for Victoria (CSFII), NSW and Queenslalld. The CD includes: 30 extension activity sheets with separate answer sheets, Risk Assessment sheets for each experiment and demonstration, blackline ma~ters to the practical experiments and Internet sites to the topics cO'1ered in the book. The extension activity sheets and Risk Assessment sheets are provided in MS Word and can be changed to the teacher's requirements. Active Science: Skills and Experiments has been trialled in the classroom. The authors and publisher would like to thank the following teachers and schools:

Paul Mackinnon Charon Joubert Lily Papadopoulis Nancy Fiore Pam Hacking Duncan Robertson Jackie Yacoub and Rosemay Joslyn

N orlane High School Eltham College Mount Waverly Secondary College Koonung Secondary College Catholic Regional College-Geelong Karingal Park Secondary College

Bayside Secondary College

Preface

I

1

CHAPTER 1: STARTING SCIENCE

What is science? Science is an exciting subject, where you can do experiments and work in a laboratory. But what is science? 1 Science is doing experiments. Experiments are a way of finding answers to problems. 2 Science is knowledge. People whose career is studying science are called scientists. Areas of special study in science have special names. • Biology is the study of living things. A person who specialises in this study is called a biologist.

Activity With the help of your teacher, state which pictures include the following: A

B

• Chemistry is the study of chemicals and how to change them, and is studied by a chemist. • Physics is the study of energy, matter and movement and is studied by a physicist. • Geology is the study of rocks and the earth, and is studied by a geologist. • Ecology is the study of how plants and animals interact together in the environment, and is studied by an ecologist. • Astronomy is the study of the planets, stars and the universe, and is investigated by an astronomer.

o

c

stereo microscope Petri dish telescope forceps an astronomer science laboratory biologist Figure 1.1.1

Figure 1.1.2

2

I

Active Science: Skills & Experiments 1

Figure 1.1.3

Science fact

Australia has a long tradition of producing talented scientists such as Adrienne Clarke and Andy Thomas. Many of our scientists have been awarded the Nobel Prize, the highest science honour in the world.

Science and technology Often people confuse science and technology. Science deals with 'understanding' while technology deals with' doing'.

ADRIENNE CLARKE is a botanist who specialises in the development of new plants. By transferring genes, she can make plants that grow more food, do not get eaten by insects and grow on land currently unsuited to farming.

List 5 examples of science and tech~ nology used at home and at school

Which branch of biology includes the study of genes?

ANDY THOMAS has orbited the earth 2250 tiines, and has travelled almost 100 million kilometres. As an astronaut he has spent 141 days in space: Andy went to school in Adelaide and trained to be an astronaut in the USA and Russia.

2 :3 4

5

Which branches of science might an astronaut need to know?

Complete the following: Science is doing

. Experiments are a way of find ing

to problems.

Science is are called

People whose career is studying study in

have

. Areas of names.

Questions Complete the table below. Part of e;cience

Name of e;cientie;t

What ie; e;tudied or learnt

biologist study of chemicals and how to change them physics geologist i

ecology study of planets, stars and the universe )'

2 Some parts of science are combinations of different branches of scientific study. Can you guess what is studied in: geophysics biochemistry

astrophysics

:3 What is a meteorologist? What is the name of the meteorologist on a TV channel that you watch? Libraryllnt ernet Ree;earch: Research the life and times of Albert Eine;tein. Describe when and where he lived, and why he is ed today.

Starting Science

I

3

Playing it safe In the laboratory there are gas taps and burners, glass beakers and flasks, water taps, and electrical power points. The laboratory could be a dangerous place if there were no safety rules. There are safety rules that apply to everyone in all laboratories. They are commonsense rules. It is important that everyone re these rules and obeys them.

Laboratory safety rules 1 No running or pushing. The floor is slippery and hard. Remove anything that might cause someone to trip. Leave your school bag in a safe and secure place, away from places where people walk. 2 Keep your notebook neat and tidy, and away from where you are doing experiments. 3 Do not taste any chemicals, or lick anything in the laboratory. Always wash your hands after working in a laboratory, and especially before eating food. Cover cuts with a dressing in case you spill something on them. 4 If you cut or bum yourself, or don't feel well, tell your teacher. Your teacher has a first-aid kit nearby. If you spill any chemicals, or break any glassware, tell your teacher. Your teacher can tell you how to quickly, easily and safely clean the mess. 5 When heating or mixing substances, never look inside the flask or beaker. Don't point these experiments at anybody. 6 Never eat food or lollies or chew gum in the laboratory, or drink from laboratory glassware. 7 Rinse and dry the glassware that you use, and return it to the correct cupboard. Leave your bench clean and dry. Don't put rubbish in the drain or sink. 8 Follow the correct procedure for lighting a Bunsen burner, handling hot equipment, dealing with chemical spills, and disposing of unwanted chemicals and rubbish. 9 Never mix chemicals at random. Always follow your teacher's instructions.

4

I


Other safety tips • If you have long hair, keep it tied back and away from flames and chemicals. • Always wear closed shoes in the laboratory, never thongs or sandals. • Place a heat mat under hot beakers. Don't scorch the bench, or bum your fingers. • It is important that you obey your teacher's instructions and the laboratory rules. • If you have ever suffered from health problems such as asthma, epilepsy, blackouts or diabetes, you should tell your teacher. Your teacher can then help you if you get sick. (You can tell your teacher in private if you like.)

Fire! What should you do in case of a fire at your school? Three things: 1 Tell a teacher there is a fire. 2 Evacuate the area. 3 Check that everyone is safe.

Science fact Safety labels Hazardous chem icals must be labelled to alert people to their dangerous properties.

Figure 1.2.1

Question: Check where these labels are displayed in your science laboratory, and write the meanings of the in your notebook.

Activity: Observation skills Aim: To identify the types of misbehaviour in the

Conclu6ion: List the safety rules that must be followed in a science laboratory.

laboratory. Material6: Figure 1.2.2, paper and pen. Method: 1 Look at figure 1.2.2. On your own, list all the wrong things that you can find . 2 with others to make groups of four, and compare lists. :3 Select one person from your group to report to the class how many things your group found wrong in the picture. Re6ult6: List all the wrong things your group found. Di6cu66ion:

"".....,, . 'ME"']

How many wrong things did you find on your own? S04

I

2 How many wrong things did your group of four find?

:3 Did other groups in your class find any more wrong things?

Figure 1.2.2 Misbehaving in the laboratory

Complete the following: place if there were no

could be a

The If you have long

Always wear

back and -away from

, keep it

-,."---

shoes in the

It is important that you

c never point experiments d never eat or drink

e cut or burn yourself f

clean up the mess

g wash your hands

and the h notebooks neat and tidy

Some notes about safety are written below. Which Laboratory Safety Rule do they relate to? Write the number of the rule (1 to 9).

b tell your teacher

and

, never

your teacher's _

Questions

a walk, don't run

rules.

lighting a Bunsen burner

j

leave your bench tidy

k don't put rubbish in sink I

or drain handling hot equipment m spill any chemicals Answer questions 2 and 3 in your notebook. 2 . Design and produce a poster that illustrates one safety rule. :3 What is the evacuation route from your science laboratory?

Starting Science

I

5

Working in the laboratory Bunsen burners were invented by a German chemist, Robert Bunsen, in 1855. They are still essential pieces of laboratory equipment today. Rules for lighting a Bunsen burner: 1 Push the rubber tube onto the gas outlet. 2 Close the air hole. You do this by turning the collar. 3 Light the match or taper. Hold match or taper over the top of the barrel (see figure 1.3.1). 4 Turn on the gas. Always turn on the gas last. Hold your hand below the flame. When the air hole is closed, no air gets in, and the colour of the flame is bright yellow. This flame is called the safety flame. It is not very hot and not good for heating. 5 Open the air hole, so that air mixes with the gas to produce a hotter, pale blue flame. This flame is used for heating.

Match held to one side of top of burner Barrel

Air hole closed Collar Figure 1.3.1 The right way to light a Bunsen burner

6 When the Bunsen burner is not being used for heating, the yellow safety flame should be used.

Activity can be rotated, which changes the size of the

1 The

, air gets in and mixes with the colour of the flame is pale

hot as the

. This makes the gas burn

. When the air hole is

colour of the flame is bright

hole. When·the air hole is

, no

. This yellow flame is called the

, and the gets in, and the flame. It is not as

flame, and it is very sooty. This means that it is not good for

But it can still burn you! 2 Write the colour for each flame. Colour the flames.

Safety flame

6

I

Heating flame

Active Science: Skills &Experiments 1

3 How to set up a bunsen burner. Label the parts.

Experiment: Lighting a Bunsen burner Aim: To learn · how to light and use a Bunsen burner safely. Materials: A Bunsen burner, a heat mat, a gauze mat, an evaporating basin, metal tongs and matches. Method: 1 Place the heat mat on the work bench and put the Bunsen burner on top. Attach the rubber tubing of the Bunsen burner to the gas tap. 2 Close the air hole on the Bunsen burner. Light a match, open the gas tap and light the burner. :3 Open the air hole and observe the change in colour of the flame. 4 The blue flame is very hot and hollow. You can observe this by heating a gauze mat over a blue flame. Hold the gauze mat carefully -with metal tongs. 5 The yellow flame is very bright, but very sooty. Hold an evaporating basin with the tongs over the yellow flame and observe the soot collecting on the dish . The yellow flame is not very hot.

Questions

Use of

Bunsen burner

Discussion:

Why should you open the gas tap only after lighting the match?

2 What happens when the air hole is closed?

:3 What happens when the air hole is opened?

c The safety flame is not good for heating.

When using a Bunsen burner, the air hole is sometimes open and sometimes closed . Complete the table below.

2

6 When you want to heat something always use the blue flame because it is hot. When you are not heating anything use the yellow flame so that you can see it. 7 To switch off the burner turn the tap off, take the rubber tubing off and place the burner in a specified place. Don't touch a hot burner with your hand.

Should air hole be open or closed?

Give two reasons why.

d Which is the best flame to use for heating?

lighting it using it for heating turned on but not heating

:3 Complete the following: Feature

Air hole Air hole closed open

colour of the flame

Answer these questions about flames.

sound made

a Why is a safety flame important? ~

easy to see sootiness of the

b How can you make a safety flame using your Bunsen burner?

flame shape of flame

Starting Science

I

7

laboratory equipment In a science laboratory you will be using different equipment. Equipment is the name given to the beakers, burners, flasks and stands you use in the laboratory to do experiments.

The diagrams below show the names of commonly used equipment. When you put together the equipment for an experiment, it is called an apparatus.

Activity 1 Beaker 2 Tripod stands

9 Crucible and lid 10 Bosshead

25 Conical flask

18· Pipe-clay triangle

26 Round bottom

3 Bunsen burner

11 Ring clamp

19 Safety glasses

4 Gauze mat

12 Filter funnel

20 Test tube rack

5 Thermometer

13 Clamp

21 Types of spatulas

6 Test tube holder

14 Heat mat

22 Gas jar and lid

7 Crucible tongs

15 Test tube

23 Pestle and mortar

8 Retort stand

16 Evaporating basin

24 Measuring cylinder

§

o

-v

C===?

8

17 Watchglass

I


G

or Florence flask

27 Stirring rod 28 Test tube brush

Experiment: Boiling water Aim: To boil water using a Bunsen burner and measure the boiling point of water. Material6: A §unsen burner. a tripod, a gauze mat, a heat mat, a retort stand with a bosshead and a clamp, a Celsius thermometer, a 250 mL beaker and matches. Method: 1 Half fill the beaker with tap water and place it on the gauze mat over the tripod stand. 2 Attach ~ thermometer to the clamp of the retort stand making sure that the tip of the thermometer is below the water level. Re6ult6: Label the equipment used in the diagram below and complete the table.

:3 Take the temperature of water before 4 5 6 7 8

heating and record it in the results table. Ught.the Bunsen burner and heat the water using the blue flame until it starts to boil. Note the temperature of the water when it starts to boil and record it in the table. Keep the water boiling for a while and take the temperature again. Record it in the table. Note what happens to the level of water in the beaker. Don't boil the water dry. After the experiment is over, switch off the Bunsen burner. Leave the beaker with hot water on the tripod until it cools and then pack it away.

State of water

Temperature of water ("C)

Temperature of water before heating Temperature of water when it starts to boil Temperature of water after it continues to boil

Di6CU66ion: 1 What precautions do you have to take when you boil the water with a Bunsen burner'?

:3 What happens to the amount of water in the beaker, if you continue to boil the water for a while'?

Conclu6ion: What is the boiling point of

2 Does the temperature change as the water

water'?

is boiled longer'?

Questions For each piece of equipment write what it Is used for and the number of the correct diagram (from page 8):

~quipment

What it i6 u6ed for

Diagram number

.

Evaporating basin ......... "" """"""==_....",""""""'-~=:==== Test tube Crucible tongs TraiPuOzdesmtaantd G Retort stand

~,." , - "= =............... """""""'_ .. ,~"""""=.......,:"""""-=:: : i ____

;u: :=: ==

j

:="""""""""""""=om"""'...."""*"""".... ' ..... ="""""".. ___.........:_: ....:"""...=-:-=_==~d

C:

:=~*:=:

_=

Starting Science

I

9

Keeping records Everyone keeps records. At school you keep records of your lessons in your notebooks for each subject. Make notes in your science notebook. Keep your book neat and tidy. Put a waterproof cover on it.

There are two parts to keeping records in science experiments. One is a record of the equipment you have used in an experiment. This is drawn in a diagram. The other part is a written story of what you did. This is called the report. This activity looks at both of these parts.

Drawing diagrams A 1 2 3 4

diagram is a simple line drawing, looking from the side. Draw diagram neatly in' pencil. Lines are drawn with a ruler. Labels are neatly printed, and connected to the diagram with lines. Diagrams should be between 6 and 10 cm high. Drawing

Diagram

Drawing

Diagram

o Activity Draw a diagram of each drawing: Drawing

Diagram

Writing reports A report is a written story of what you did in an experiment. Each report you write should consist of the following parts: 1 Title-the name of the experiment, e.g. Observing and recording information. 2 Date-when you did the experiment. 3 Group -names of the students who were in your group to do the experiment. 4 Aim, question or problem-what you are trying to find out or why you are doing the experiment. S Hypothesis-an idea that can be tested.

10

I


6 Materials-list the equipment/apparatus and chemicals used in the experiment. 7 Method-describe how you did the experiment. Always include a diagram of the apparatus you used. 8 Results-an explanation of what happened or what you measured. Include tables and graphs when relevant. 9 Discussion-discuss what you have found out or what you have learnt. 10 Conclusion-does your experiment answer the aim and does it the hypothesis?

Activity: Checking a report Read this rep.ort of a filtration experiment.

eeeeeeeeeeeeeeeeeeeeeee

Experiment

30 Feb

Filtration Aim: To find a good way to separate chalk from water. Method: A solution of chalk and water was made. which we filtered using filter paper. ~_"-I+-- funnel

2 with a friend, and compare your lists.

retort -+---tt---

beaker

3 Then j oin with another group of two, and Results: The chal k stayed in the filler paper and the water went into the beaker. Conclusion: chalk and water can be separated by filtering. The chalk stays in the filter paper and the water goes through.

compare your lists.

4 Select one person from your group of four to report to the class on the incorrect th ings

Figure 1.5.1

your group found . On your own find as many wrong things as , you can in the report.

Complete the following: There are

Questions What is the difference between 'a drawing

parts to keeping

records in science. One is record the

and a diagram'? .

you have used in an experiment. This is drawn in a The other part is a written

of

what you did. This is called the Each report has the following parts: title, date, group

, aim, hypothesis, , method,

2 What should a conclusion include'?

discussion and A diagram is a simple line looking from the should be between

. Diagrams and

cm high .

Starting Science

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11

Dissolving and filtering If you add sugar to a hot drink and stir it, the sugar dissolves. A substance which dissolves, like sugar, is said to be soluble. The opposite is insoluble. Sand is insoluble because it does not dissolve. When sugar has dissolved in hot water, we cannot see it. We know it is there because we can taste it. The water with sugar in it is called a solution. A solution is a liquid with something dissolved in it. If you put chalk in a beaker of water and stir it, the chalk will not dissolve. Chalk is insoluble. The water turns murky, but clears as the chalk settles

to the bottom. Water with an insoluble chemical floating in it is called a suspension. In our experiments we will use copper sulfate as a soluble chemical. It is blue, and we can see when it is dissolved. Filtration is the process which removes an insoluble substance from a suspension. Special paper, called filter paper, is used. Crystallisation occurs when the water is removed from a solution. The water evaporates and crystals are left behind. It is the reverse process of dissolving.

Activity Number the steps in the correct order: Filter funnel

Filter paper folded cone

Tear off corner

Fold over again

Open out into a cone, tom comer on the outside Fold over

Figure 1.6.1 How to fold filter paper

Experiment: Filtering suspensions and solutions Aim: To filter a suspension and a solution.

Materials: Chalk, copper sulfate, mortar and pestle, water, two 150 mL .beakers, filter paper, funnel, retort stand, ring clamp, stirring rod and spatula. Method: 1 Chalk is insoluble in water and can be used to make a suspension. Crush some white chaikin a mortar and pestle. Grind the chalk in a circular motion.

Mortar

Pestle

Figure 1.6:2 Using a mortar and pestle

12

I

Filter funnel

2 Scrape the chalk out of the mortar and tip it into a 150 mL beaker. Add 100 mL water and stir with the stirring rod to make a suspension . :3 Set up the apparatus as shown in the drawing and filter the suspension. Observe what is left in the filter paper and what has col lected in the beaker


Bottom of funnel should touch inside of beaker, to prevent splashing

4 Copper sulfate is soluble and can be used to make a solution. Dissolve 2 spatulas of copper sulfate in 100 mL water. Stir with the stirring rod until it dissolves.

:3 Does it settle if it is left standing? 4 Can you see through a solution? 5 Can you f ilter it? 6 Does it settle after standing? Conclusion:

7 Where did the chalk and copper sulfate end up? Chalk suspension

Copper sulfate solution

Figure 1.6.4 Filtration apparatus

5 Fi lter the copper sulfate solution and observe what is left in the filter paper and what has collected in the beaker. Results: -State if the following substances were left in the filter paper or collected in the beaker. Chalk suspension: Copper sulfate solution: 8 Which one is soluble and which one is not

Discussion:

soluble in water? soluble:

Can you see through a suspension?

not soluble:

2 Can you filter the suspension?

Complete the following: A substance which dissolves, like

A

, is said to be

is a liquid with something

. The opposite is in it. Water with an

chemical floating in it is called a Filtration is the process which removes an

substance from a

Questions Complete the table below. Write the substances into t he correct columns.

soluble 5ub5tance5

in50luble 5ub5tance5

sand, salt, sugar, glass, steel, instant coffee, copper sulfate, plastic

2 Write one sentence which explains the meaning of each pair of words.

a soluble and insoluble b soluble and solution c

insoluble and suspension

:3 Cut open a tea bag and examine the paper. Feel it and look closely at it. Do you think that it contains small holes? How is a tea bag like filter paper?

Slarting Science

I

13

Investigations Science is about finding answers to questions and problems. A hypothesis is a guess that predicts what will happen in an experiment. If your hypothesis cannot explain what happens in the experiment, formulate a new hypothesis and test it. An explanation of a hypothesis is called a theory. Theories try to explain why and how things in the world happen.

Experiment: Ping pong bounce Aim: To find out the method to make a ping pong ball travel the furthest after it bounces. Hypothesis: Write your own hypothesis here after you have read the method (but before you do the experiment).

Some important theories are the oxygen theory of burning, the germ theory of. diseases and the theory that all substances are made up of small particles called atoms. Scientists find answers to their questions by doing experiments. The results are reported at meetings and published in scientific journals or magazines.

3 Repeat the experiment with the ping pong ball with holes in it. 4 Use a different brand of ping pong ball. 5 Change the amount of spin on the ball. 6 Bounce the ball on different floor coverings such as carpet and a vinyl floor covering.

Materials: 1 white ping pong ball, a white ping pong ball with holes, a white ping pong ball of a different brand, a coloured ping pong ball, a cardboard tube, a sloping shelf, a metre ruler, and a thermometer.

Method: 1 Drop the ping pong ball from a height of 1.5 metres above the ground. Only drop the ball, or roll it out of a tube. Do not throw or flick it. You can spin the ball, as long as it does not go forward while it is falling. Ask your partner to measure the distance the ball travels between its f irst and second bounce. Figure 1.7.1 Ping pong bouce

White ball dropped from a height of 1.5 m White ball dropped on a sloping shelf

j '. ,'------,

Different brand of white ball dropped from a height of 1.5 cm

1.5m "

~

,,'

1st '.,' bounce'.i,.. :

"\ " " _-"' ..

'. -' 2nd " .. './ bounce'. I

\

Measure this distance

2 Drop the ball onto a sloping shelf and again measure the distance the ball travels between its first and second bounce.

I

Experimental method

White ball with holes dropped from a height of 1.5 m

1'\~

14

Figure 1.7.2 Different bouncing methods Results:


Coloured ball dropped from a height of 1.5 m White ball spun at a greater speed and dropped from 1.5 m White ball dropped from 1.5 m onto carpet White ball dropped from 1.5 m onto a vinyl floor covering

Distance of bounce (cm)

Discussion and conclusion:

2 Was your hypothesis ed by the

Under which conditions did the ping pong ball travel the greatest distance'?

Demonstration: Tea bag rockets Your teacher will demonstrate this activity. Do not attempt it yourself at home. Aim: To make a tea bag rocket. Materials: Tea bags, toilet roll, 200 mL and 100 mL beakers, paper, matches, scissors, heat mat. Method: Get a tea bag (not the round type) and cut the ends off. Tip the tea out and make the bag into a tube shape. When your teacher sets fire to the top of the tea bag, the flame burns the paper and when nearly all the paper has been burnt, the rocket lifts off. Further investigations: Here are some other questions to investigate (answer them in your notebook): 1 What happens if we cut the rocket in half, to make two shorter rockets'? 2 Can we use other paper, or a toi let roll, to make a rocket'? :3 What is the shortest rocket we can make that will still fly'? 4 Will the rocket lift off if it is inside a beaker'?

results of the experiment,?

:3 How would you modify your hypothesis'?

5 Does the size of the beaker (i n question 4) make any difference'? Ta lk with your teacher about some theories to explain why the tea bag rocket lifts off the bench. Write your theories in your notebook.

OJ Cut the ends off

Open the bag into a cylinder

Figure 1.7.3 Making a tea bag rocket

Questions

:3 Name some science magazines.

What is the difference between a hypothesis and a theory'? 4

How would you f ind background information for an investigation'? List at least three places where you could look.

2 Why do scientists do experiments'?

Starting Science

I

15

Measurements We use measurements every day. To make sure measurements are consistent, we use standard measuring amounts, called units of measurements. The system of units we use in Australia for measuring is called the metric system. Another system that some other countries use is called the imperial system.

Length • Length is measured in the unit called metres (m).

• For long distances, kilometres (km) are used. • For short distances, centimetres (em) or millimetres (mm) are used. • Trundle wheel, metre rule and tape measure are used to measure length.

Writing measurements Every measurement has two parts: the number and the unit. Five metres is written as 5 m. Writing 5 ms is wrong, because s means seconds, and 5 ms means five milliseconds. Prefixes are added to the units when very large or small things are being measured. You would measure a large mass in kilograms, or a very short length in millimetres. The prefixes that are used in measurements are shown in the table below.

Mass • Mass is how much matter is in an object. • It is measured in the units called grams (g) or kilograms (kg). • Tiny masses are measured in milligrams (mg). • Beam balances, spring balances and electronic scales are used to measure mass.

Time • Time is measured in the unit called seconds

Prefix

Symbol

Multiply by

mega

M

1000 000

kilo

k

1000

hecto

h

100

deca

da

10

Temperature

deci

d

lila

centi

c

1/100

milli

m

1/1000

micro

j.1

1/1000 000

• Temperature is measured in the unit called degrees Celsius (QC). • It is measured with a thermometer or a thermistor.

Volume • Volume is how much space something takes up. • It is measured in the units called Htres (L) and millilitres (mL). • Beakers and measuring cylinders are used to measure the volume of liquids. • In a glass container, water is pulled up where it touches the glass. This is called the meniscus. When you measure volume, always read the scale from the bottom of the meniscus.

16

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(s).

• Other units of time are minutes and hours. • It is measured with a watch or a clock. • A stopwatch measures time in seconds.

Place the measuring cylinder on a level surface. Look in line with the top of the water. - - -- - -- - -- ~

Meniscus

level here

Read the water level at the bottom of the meniscus. (Here the correct measurement is mL.) Figure 1.8.1 Reading from a meniscus-fill in the measurement

Experiment: Measuring objects Aim: To measure the mass, volume, thickness, distance and time in metric units. Materials: A 100 mL measuring cylinder, a cup, water, film canister filled wit;h sand, beam balance, metre ruler or a measuring tape, a 100 cm ruler, a clock or a stopwatch and a tennis ball.

Method: 1 Fill a cup with water and pour the water in a measuring cylinder. Note the volume of water in mL. 2 Weigh the empty film canister with a beam ~alance and find out its mass in grams. Fill the canister with sand and weigh it again. Note the mass of the canister with sand. Subtract the mass of the empty canister from the mass of the canister with sand to find out the mass of sand in grams. 3 Measure the distance, in metres, from your seat in class to the blackboard with a tape measure. 4 Measure the thickness of your science textbook, in centimetres, with a ruler.

5 Throw a tennis ball into the air and note how long it stays in the air, in seconds, using a stopwatch. 6 Record your results in the table and compare your results with other of the class to see if your measurements are similar or different. Results:

Object measured

What is measured

Measurement taken

Cupful of water

mL

Film canister filled with sand

g

Distance from your seat to th e black board

m cm

Science textbook Tennis ball

s

Discussion:

What is the advantage of comparing your results with class results'?

Conclusion : List the metric un its you used to

measure the following: volume mass

, length

2 Why might some of your results be different from other people's results in the class'?

time

Questions

3 What would happen if units were not the

What do the following units mean'? a

~-------

~~------~

same everywhere in Australia'?

---=-...".,..,j

millisecond ·

4 Which instruments are used to measure the b

kilolitre

c

centigram

2 Which system of measurement is used in

following'? a

volume

b

mass

d

time

Australia'?

Starling Science

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17

Mind maps A mind map is a way of linking all the ideas you have learnt in a topic. It's a summary, a study guide and a revision sheet all in one. Sometimes mind maps are called concept maps. Here is an example of how to make a mind map: • A class was given some sheets of cardboard. On the first piece the teacher wrote 'Science is'. • She then asked two students to write what science is. One wrote 'knowledge' and the other wrote 'finding answers'. • Some students were interested in what scientists study, so they wrote the names of types of science: 'Biology', 'Geology', 'Physics' etc. • Other students were interested in what scientists do in their work, such as 'proposing' and 'discovering'. Other students wrote about what scientists do in our society. Their cards

Figure 1.9.1 Mind map cards

18

I


had words like 'satellites', 'cure diseases' and 'endangered species' written on them. The class and their cards are shown in the drawing below. • A mind map is made when cards with similar ideas are placed near each other. Then the idea boxes which are similar, or ideas which depend on each other, with an arrow. An explanation is written along the arrow. A mind map of 'Science is'is drawn on the next page. You can draw your own mind map by writing important words that are relevant to the topic in boxes. A mind map is best if it has about 20-30 ideas, but it can be bigger. Each idea should be ed by arrows. Writing on the arrows explains the connection between the ideas. Mind maps can be drawn for any topics. They can be drawn in your notebook or on a whiteboard for the whole class to see.

is

is

SCIENCE

by doing

Figure 1.9.2 A mind map for 'Science is'

Questions

2

What is a mind map'? What does it show'?

Draw a mind map for the idea 'laboratory equipment'. The words 'laboratory equipment' are in a box at the top. Now list equipment such as Bunsen burner, beaker, gauze mat, filter funnel etc. Add more equipment until you have about 15 items. Connect them with arrows and write explanations on the arrows.

LABORATORY EQUIPMENT

Slarling Science

19

Review and research True or False?

True

a You should light the Bunsen burner with the air hole closed. b Beakers are made from heat-resistant glass.

c Always use a gauze mat when you are heating a beaker with a Bunsen burner. d Running is allowed in the laboratory.

e You are not allowed to eat food in the laboratory. f

When lighting a Bunsen burner, always turn on the gas before lighting the match.

g The safest flame for a Bunsen burner is yellow. 2 Which of these statements about heating a test tube are correct? a Always fill the test tube to the top. b Never point the test tube at people.

c Have the test tube holder away from the flame. d Move the test tube around in the flame.

e Use the Bunsen burner on the yellow flame to avoid too much heat. d

e

9

:3 Here is a list of areas of scientific study. What is the name given to each area of study? Choose from these answers: astronomy, chemie;try, biology, phye;ice;, geology, ecology. a The study of rocks and the earth. b The study of movement, energy and machines.

c The study of living things. d The study of chemicals and how to change them.

e The study of stars, space and planets. f

20

The study of the environment and how it works.

I


False

4

Here are some pictures of the apparatus used in some experiments. Redraw them as diagrams, label each item of equipment, and state what the apparatus is used for.

a

b

5 Why is there a laboratory rule against running? __

~~~~==~=:~~mm=-~_'&R=-&M_&&&~

____

~~~~~

6 What should you do if you break a beaker? 7 What is the correct way to boil water in a test tube?

=

=

8 What is the advantage of drawing a mind map for each topic of work?

Starting Science

I

21

Cameo profiles

SIR MARK OLIPHANT, a physicist, studied microwaves in relation to radar and telecommunications. His discoveries led to the development of microwave ovens.

HELEN CALDICOTT believes that people are not careful enough with their environment. She has campaigned against nuclear testing and against the destruction of the environment. She writes on health and environment issues, and speaks at conferences all around the world.

LYN BEAZLEY is a zoologist and is fascinated with animals. Her main interest is in finding out how eyes develop and work, with a view to curing eye disease.

KARL KRUSZELNICKI is a science broadcaster and writer. He talks on the radio, on television, and at lectures and museums, as well as writing books. Listen to him on ABC Radio or read one of his books.

Research project

Research question

Research a notable Australian scientist, and record details of their life and achievements. Write it in cameo form, like the ones above. Some ideas are: Jerry Adams, Suzanne Cory, Michael Archer, Lucy Bryce, Macfarlane Burnet, Jean Macnamara, Howard Florey, John Tebbutt, Joseph Bosisto, Catherine Hamlin, Lawrence Hargrave, Dorothy Hill, Fred Hollows, Douglas Mawson, Gustav Nossal, John Eccles, William McBride, Nancy Millis, John Cornforth .

Collect four articles in newspapers concerning scientists and other people doing research. This could be medical research, wildlife research, or the development of a new chemical. Paste the articles in your notebook and summarise the information in your own words.

22

I


Puzzle Match the descriptions on the left with the equipment on the right. Each number will then correspond to a letter. Write the letters in the grid below, using the numbers as a guide. What is the message?

1 2 3 4

5 6 7 8 9

10

th ree-Iegged stand gas burner used in laboratory protects your eyes in experiments equipment used with a pestle clamp to hold filter funnel used to hold hot objects spreads out heat from Bunsen burner double clamp attaches to retort stand tall metal stand measures temperature

A B E F I

0 P

S T Y

mortar clamp retort stand thermometer tripod stand gauze mat safety glasses tongs Bunsen burner ring clamp

Crossword Across 3 4 7 8

10 11 12 13 14 19 21 22

Glassware used to hold and heat solutions (6 letters) What you aim for in sport and school life (4) Abbreviation of laboratory (3) Used to cut paper (8) Means to tip a liquid into something else (4) Do not do this in the laboratory (3) Type of glass tube (4) Opposite of light (4) Spreads out the heat between a flame and glass (5,3) Wrapped around a person to smother the flames on their clothes (4,7) Footwear not to wear in the laboratory (6) Grainy insoluble substance in a fire bucket (4)

Down 1 Curved surface of water, measure at the bottom of it (8 letters) 2 Happens to water at 100°C (4) 3 Holds the clamp to the retort stand (8) 5 Place where you do experiments (10) 6 Essential part of a filtration (6,5) 9 Used to remove chemicals from their containers (7) 15 Name shared by a small animal and a mark meaning correct (4) 16 To do well, you need to make this (6) 17 Beakers are made from heat resistant (5) 18 Retort and tripod (5) 20 Used with bolts (4)

Starting Science

I

23

CHAPTER 2:' INVESTIGATING

Being observant To be good at investigating and solving problems, you need to be observant. This means noticing things around you by using all your sensesseeing, tasting, smelling, hearing and feeling. these safety tips: • you should never taste anything in the laboratory • when smelling, waft the fumes towards your nose. Breathe gently so you don't inhale fumes into your lungs.

following note. Compare the handwriting to determine who wrote the note. Write who you think the catnapper is and include the reasons why you selected your suspect:

E;-m~;

I the DNA code to my Pc by 7 pm. It not, you;" c~t w; II be deleted\

Figure 2.1.1 Waft fumes to your nose

Ransom note Professor Jill Catlove is a genetic scientist and a cat lover. She has discovered the code for DNA in the genes of a cat which causes them to grow floppy ears. Her own cat has been kidnapped and. is being held to ransom. Jill received the

Experiment A fruity problem Aim: To identify fruits using senses of touch and smell. Materials: Blindfold, thick gloves, oranges, pears, apples, peaches and plums Method: 1 Divide the class into groups. Each group should consist of three students. 2 Blindfold one student and ask them to identify the fruits in any order by touching and smelling the fruit. :3 Blindfold the second student and get them to wear thick gloves so that he/she cannot feel the skin of the fruit. This student is allowed to identify the fruits by smell only. 4 Ask the third student to wear thick gloves and identify the fruits without smelling the fruits. Record your results in the table.

24

I


SUSPECT

WRITING SAMPLES

Gill T. Uronner Your .::....t Ivor Confeshin '( C1ol1: c....\ Kate Napper Your cat Freda Matlast Your cat Betty Diddit Your GAl

My PC

7p~

""" 'i'C

'(>'M.

~PC

My PC /'1.

Pc.

7t>IVo. 7pm. 7,.",

Figure 2.1.2 Who wrote the ransom 110te?

Results: Student identifying fruit Number of fruits correctly identified out of 5 fruits

1 With blindfold only, allowed to feel and smell 2 With blindfold and thick gloves, allowed to smell

:3 With blindfold and thick gloves, not allowed to smell Discussion: 1 Which student was the most observant?

2 Does having more senses available to you help in making more accurate decisions?

:3 How important is it to use all your senses? Conclusion:

Out of the two senses used which sense was 4 Would the results of the experiment be

more useful in identifying the fruits?

different if you wore earmuffs? Explain. 2 Which other sense would help to identify the fruits more accurately? 5 What would have happened if you were allowed to taste the fruit?

Science fact Forensic science If you enjoy solving mysteries, a career in . fQrensic scienee may be right for you . Forensic scientists use science to .solve crimes. They might use their observation skills to analyse handwriting, or fingerprints, or teeth marks. They could use their knowledge of chemistry to analyse fibres or poison found at the scene of a crime. A forensic scientist might use their

Questions What does observant mean?

knowledge of biology and genetics to analyse blood or tissue samplt;s found at a crime scene, or perhaps use their knowledge of physics to determine exactly where someone was standing when they committed a crime. Question: To have a career as a forensic

scientist, which branches of science would you be required to study?

Using your knowledge, state which drop (1, 2 or 3) would be found: a on the floor where it fell b on the floor where it was flung

2 List your senses. Which sense should not be used in the laboratory?

c on the blackboard 4 There is a word message hidden in the drawing shown below. What is the message?

I I I- I

III II •

:3 Two students in your class had a water fight and the teacher caught them. There are drops of water splashed in different places, including the blackboard, floor and bench.

--

-

l-

I-

.1 Figure 2.1.4

•• n

.1 I

• II

Figure 2.1.3

Investigating

I

25

Showing data: tables and histograms Data is information that has been collected. It can be presented in the form of a table or a graph so that it is easy to see. Sometimes the information we have needs to be sorted. A table lets you sort data quickly.

Drawing graphs A histogram is a type of column graph. It shows the information in the table in a visual form, like a picture and it is easy to understand.

Creating tables

Time Ken spent on homework

3r---------------------------

Ken recorded the time he spent on homework each day in his diary. He wanted to draw a table and a column graph of the time he spent on homework. Time Ken spent on homework

Day

Time (hours)

Monday

1.5

Tuesday

2

Wednesday

1

Thursday

2.5

Friday

1

o Days of the week

Figure 2.2.1 Ken's histogram

Note that: • the table has a title or heading • the time spent is all in the same unit (hours) • the units used are written at the top of the column • the table has neat lines drawn with a ruler and the numbers are in a vertical line • if Ken had not done any homework, a zero would be recorded in the time column. • if he had forgotten to record his time and no result was available, then a dash (-) would be written in. No blanks should be left in the table.

Questi ons

Note that: • the graph has a heading, or a title • each axis has a title and units • the scale on each axis is even. There is the same distance between the days on the horizontal (bottom) axis and between the numbers of hours on the vertical (side) axis • the graph is neatly drawn, using a ruler • the columns are the same thickness and same distance apart.

Science test results

What is the advantage of a histogram over a table?

2 On the right are the marks scored in a science test by a class. The test was out of 20 marks. There were 30 students in the class. The highest mark was 20 and the lowest was 11 .

26

I


20

14

19

14

18

16

19

18

20

18

13

18

15

17

14

16

19

14

18

16

19

11

18

17

17

19

15

18

16

18

Figure 2.2.2

a Record the data from f igure 2.2.2 in the table below. Te9t 9core

Number of 9tudent9

Te9t 9core

20

15

19

14

18

13

17

12

16

11

Number of 9tudent9

Science test results b Draw a column graph of the data. The test score should go across the horizontal axis. The number of students should go on the vertical axis.

4 Refer to the histogram below to answer the following questions: Weight of students in class

10

a;

.0

E

~

4 2

o 3 Marie had an assignment on the amount of glass recycled in different countries. While she was researching, Marie made notes, as shown. Recycling a95ignment: Gla55 recycling in 1985 Canada = 12% US = 8% England = 12% Japan = 47% New Zealand = 5310 Australia = 17%

Complete the table below with Marie's data and then draw it in a histogram.

Figure 2.2 .3

a How many students weigh between 56 and 60 kg'? b What is the most common weight of students in this class'?

c What cou ld be the smallest weight in this class'? d What could be the weight of the heaviest student in this class'?

Glass recycling in 1985 Percentage of gla99 recycled (%)

51-60 41-50

Number of countrie9

41-45 46-50 51-55 56-60 61 -65 66-70 71-75 Weight of students (kg)

e How many students are in the class'?

f

List two pieces of information that this column graph does not tell you.

31-40 21-30 11-20 0-10

Investigating

27

Showing data: graphs Bar graphs A bar graph is used to show parts or fractions. For example, we can graph the amounts of the main gases in clean air. Amount of gases in air

Gas

Percentage %

Nitrogen

78

Oxygen

21

Other gases

1

Figure 2.3.2 A column graph and double line graph

Double graphs

A bar graph shows these amounts as different colours or patterns in a bar. Key:

i

Nitrogen Oxygen Other Gases

You don't have to draw two graphs to show two sets of data.You can use the same graph with two different lines or two different sets of columns. Using the same graph is important if you want to compare data.

Figure 2.3.1 A bar graph

Pie graphs

• Make your bar graph 10 cm long-that makes 1 mm equal to 1 %. • Include a key that shows which parts of the graph stand for the different gases.

Pie graphs present information using a circle that has been divided into sections. Each section represents a fraction of a whole circle or pie. Earth's water supply

Column and line graphs A column graph shows the data in a series of columns. A line graph has a line ing the points where the middle of the tops of the column would be. These points are called data points. Most graphs used in science are line graphs.

• Glacial ice

o Fresh water Glacial ice 2% Figure 2.3.3 A pie graph

Questions What points should you include in your checkl ist when drawing a line graph?

*l

~

'-' ~

.0

.!:

.el

'2:

2Q)

E

ro

<:: Q)

cti '-'

Cf)

Figure 2.3.4 Hints for drawing line graphs

28

I


~ Oceans

Oceans 97%

Fresh water 1%

Title: what the graph shows 70 65 60 Your graflh 55 Scales start at shoula fi I zero in the most of the 50 corner (origin) graph paper 45 if you can 40 Plot the data pOints 35 ~ clearly, and with a ruler 30 25 Start graph at 0 on vertical axis 20 v:~orizonl1!l axis as well if it is part of data) 15 10 Scale should be regular-each increase should be the same 5 0 12 15 18 3 6 9 Scale name (units in brackets)

Key: In shade In sun

3 Draw a line graph to show the following data:

Number of sparrows counted on 15th day of each month

Month

Sparrowe

Month

Sparrowe

January

23

July

10

February

29

August

9

March

33

September 8

April

24

October

14

May

17

November

16

June

12

December

20 5 Show the following information in a double column graph, with the co lumns for Perth and Canberra drawn beside each other for each place where water is used.

4 Draw a double line graph using the two sets of data below.

Time

In eun tC)

In ehade tC)

8a.m.

19

18

9 a.m. '

21

20

10 a.m.

23

22

11 a.m .

26

23

12 noon

29

25

1 p.m.

31

26

2 p.m.

32

27

3 p.m .

30

4 p.m.

27

5 p.m.

25

Where water Percentage ie 'ueed ueage in Perth (%)

Percentage ueagein Canberra (%)

Bathroom

22

16

Toilet

19

14

Laundry

13

10

Kitchen

4

5

Garden

38

52

Pool

4

3

Key: Canberra Perth

26 .

23 21

Investigating

29

Observation. inference and hypothesis An observation is something that you notice using any of your senses. Being observant means using all your senses to notice things around you. It is important to be accurate in your observations. Some observations are: • Smelling onions in the kitchen. • Finding that a fabric feels like satin. • Seeing a man running down the street. • Hearing an electronic alarm. • Finding that lemon juice tastes sour. An inference is a likely explanation of what you observed. It is how you explain the observation. The explanation mayor may not be true. Here are some inferences you might have made about the observations above: • You will have onions with your dinner. • Mum bought the fabric for the concert. • The man is scared of dogs. • A cat caused the alarm to sound. • Lemons contain an acid.

A hypothesis is a guess at an answer, which you can test by doing an experiment. Some things cannot be tested by experiment, such as personal likes and dislikes. Some hypotheses you might make about the observations above: • Onions smell more on a hot day than on a cold day. • The fabric feels smooth because the fibres are close together. • The man running from the dog was bitten last year. • Cats climb onto cars, and the movement activates the car alarm. • Lemons are sour because they contain citric acid. Before starting any experiment, it is important that you plan what you are going to do. Write it in your note book. It is important to check with your teacher, so that you don't waste materials and your time.

Experiment: Testing a hypothesis

Aim:

You may know that some cand les burn faster than other candles. Why does this happen'? The hypothesis you will test in this experiment is 'Thin candles burn faster than thick candles

Hypothesis:

because there is less wax to burn'. • • •

• • •

30

Plan an experiment with your partner, then discuss your plans in groups. The experiment should find out whether the hypothesis is correct. .. Your method should include a way of measuring the height of the ca ndle as well as its mass. Suggestion: use candles that are approximately 4 cm long Write an experiment plan in your notebook, and check with your teacher before you start. Wr ite down you r hypothesis, aim, the materials you need and the method you are going to fol low in point form. Put your results in a table. Conclude whether your res ults ed your hypothesis.

I


Method:

Resu lts'

Inference:

What is measured

Thin candle

Thick candle

Height of the candles (cm)

Conclusion:

Weight of candles (g)

l

Time taken to burn down completely (min)

Activity: Observations and inferences

Observations

Inferences

How good are you at Flame: making observations? - blue at base Do you confuse - -- yellow around edge observations with - does not touch wick - flicker in a breeze inferences? Did you Wick: know that you can - is white make over 100 - braided observations of a -1 .2 cm long - glowing red on top burning candle? Observe Candle: the burning candle in - is greasy figure 2.4.1 and record - is white six observations and -15 cm tall - 1.5 cm diameter inferences about it in the table. Figure 2.4.1

Complete the following An inference is a likely . It is how you

b I measured the temperature today at

the

observation. A hypothesis is a

37"C.

of what you

c It is so hot that the temperature must be 37OC. d There is a person in a Santa suit. It must

at an answer,

which can be tested by doing an

Questions What is the correct order of hypothesis, observation, planning an experiment and inference?

be Christmas.

e This candle has a greasy feel. 3 Match the hypothesis, observation or inference with the different meanings below: a something you notice b an explanation c

a guess to an answer

d tested by experiment 2 State which of the following are observations and which are inferences.

e a quiet sound that you hear f

I think they are for the party next week

a Coffee stays hotter if you add the milk before the hot water.

Investigating

I

31

How to do a fair experiment All experiments have to be fair and valid, so that someone else can repeat them and get the same answer. In some experiments you must use a control. A control is a comparison that is used to make sure a fair test is carried out. Each experiment must have two parts. One part is what you test-the variable-and the other is the control that you will compare it with. A series of steps that have to be followed is called the scientific method. The steps are: • Observing-note as much as you can about a situation.

Experiment: Keeping liquids hot Imagine you have made yourself a cup of hot chocolate. Before you can add the milk, the phone rings. 1 If you want the drink to stay as hot as possible, should you add the milk before answering the phone or wait until after the phone call and then add the milk? 2 Some people place a saucer or other covering over their cup to keep the drink warm. Does this work? :3 Does leaving a metal spoon in a hot drink make it cool faster? In this experiment, hot water can be used instead of hot chocolate and cold water can be used instead of cold milk. Fill in the spaces below. Aim:

• Inferring-think of an explanation of what you observed. • Hypothesis-make a guess at the answer that you can test by an experiment. • Design a fair experiment, with a control, to test the hypothesis. • Do the experiment, and study the results. • Form a conclusion-say if your results agree with (prove) or disagree with (disprove) your hypothesis. A good conclusion must answer the hypothesis.

Materials: Three 250 mL beakers, a 500 mL beaker, a 100 mL measuring cylinder, a Bunsen burner, a tripod, a gauze mat, a heat mat, a watch glass, a metal spoon, two Celsius thermometers and a clock. Method:

Adding cold liquid to a hot liquid 1 Pour 300 mL water into 500 mL beaker. 2

:3 4

5

Hypothesis:

Heat the water until it starts to boil. Pour 100 mL of boiling water into each of the three 250 mL beakers. (Caution : don't burn yourself-use tongs.) Add 10 mL of cold water to one beaker and leave the other two beakers as they are. Take the tef1'1perature of each beaker at twominute intervals for 10 minutes and record the temperatures in the table. Just before you take the last measurement add 10 mL of cold water to one of the beakers that had no cold water added and stir it in.

1

Putting a lid on a hot liquid

2

6 Boil 200 mL of water in the 500 mL beaker. 7 Pour 100 mL boiling water into each of two 250 mL beakers. Place the watch glass on one of the beakers and leave the other open. 8 Take the temperature of both beakers at two-minute intervals for 10 minutes and record the temperatures in the table.

:3

Putting a spoon in a hot liquid 9 Boil 200 mL of water in the 500 mL beaker.

32

I


10 Pour 100 mL boi ling water into each of two 250 mL beakers. Put a metal spoon in one beaker and leave the other one without a spoon.

11 Take the temperature of both beakers at two-minute intervals for 10 minutes and record the t emperatu re in the table.

Re6ult6:

Putting a lid on

Adding cold liquid Time e;ince e;tart (min)

Temperature of water with cold water added fire;t

Temperature of water with cold water added at end

Temperature Temperature of water with of water no cold water with the lid added

Putting a

e;p~on

Temperature Temperature of water with of water with no lid a e;poon

in

Temperature of water with no e;poon

0

2 4

6 8 10 Di6CU66ion: Wh ich beakers were used as the cont rols'?

ConclU6ion: Write a conclusion for the experiment.

Complete the following All experiments have to be

and

....=!!=~

. A control is a

In some experiments you must use a

test is carried

to make sure a what you test-the

ou~.

so that someone else can get the same

Each experiment must have two

===---:.,

that is used . One part is

that you wil l compare it with.

- and the other is the -~---

Questions

2 What is a conclusion'? Why is it written at

What are the steps in writing a scientific method'?

-

,

~

the end of an experiment,?

-

c: : =-=

~~ .

.

!

r ~

Investigating

I

33

Review and research Review questions Rosemary recorded the following information in her diary. It concerns the time she spent doing her science assignment, and the time she spent on homework for other subjects. On Monday, I worked for 2 hours on science and then had time for half an hour for other homework before watching television. On Tuesday, I went to hockey and did some maths homework. This took 1.5 hours, and I copied up some notes for my science for 30 minutes. On Wednesday I spent 1.5 hours on both homework and the science assignment, a total of 3 hours. The next day was a disaster. I was sick and did no science and only 1 hour of homework. Friday is the end of the school week, but I copied up some notes for the science assignment for 1 hour. On Saturday I did some English and maths homework but I forget how much, and I spent 2 hours finishing the science assignment.

Record this information in the table below.

2 Draw a line graph of this data. to follow the hints given in section 2.3.

Temperature during the day

Time of day

Temperature ("C)

7.00 a.m.

13

8.00 a.m.

15

9.00 a.m .

18

10.00 a.m.

22

11.00 a.m.

27

12.00 noon

30

1.00 p.m .

31

2.00 p.m .

32

3.00 p.m.

30

4.00 p.m.

25

5.00 p.m.

22

6.00 p.m .

21

Time Rosemary spent on science and other homework

Day

Tin:e spent on sCIence assignment (hours)

Time s~ent on other omework (hours)

Monday Tuesday Wednesday Thursday Friday Saturday Now complete the histogram:

3

:3 A Year 7 science class has students with the following ha ir co lour: 40% brown, 28% black, 24% blonde and 8"/0 red . Draw this information in a bar graph below.

2

OL----------------------------Man

Tue Key

Wed

Thu

-

Fri

Hair colour by percentage in Year 7 science class

Sat

IZZZl

34


Key:

Brown

Black

Blonde

Red

4

Match each word with its meaning.

Word

Meaning

A hypothesis

1 something you notice with your senses

B observation

2 a comparison so that a fair experiment is done

C control

:3 a project or experiment you do to answer a question

D graph

4 an explanation of what you observed

E data

5 a guess at an answer you can check by experiment

F investigation

6 another name for information

G inference

7 a way of showing information in a visual form

H table

8 a way of showing information in columns and rows

Answer

5 List as many faults with this histogram as you can.

200 160 120 100 80 60 40 20 0

Thinking question (This is a big question that has many answers.) How can you make a beaker of hot water go cold as quickly as possible'? List your ideas and test them by experiment. Use a control in your experiment. Write up your experiment properly in your notebook.

Magpies graph

Ideas:

Grassy

City

National

Suburb

Beach

Research questions 6 List as many faults with this line graph as you can .

E'9 .£ -E 8 '" 7 0..

§ ~ 6 '0

Who was M.e. Escher'? Find one of this drawings and explain what is unusual about it. 2 When researchers test new medicines, they use a control. Some people are given the new drug and some people are given a placebo. What is a . placebo, and why don't all the people in the experiment get the drug to see how it works'?

Word check

:§,5 'CD

::c

2

3

4

6

8

10

Day after planting

15

20

Write the meanings of these words in your notebook. histogram bar graph line graph hypothesis column graph observant control inference observation data information prediction double graphs investigation table

Mind map Draw a mind map in your notebook using all the ideas about investigating in this chapter.

Investigating

I

35

CHAPTER 3: THE PARTICLE THEORY

States of matter States of matter Matter is everything around you. Anything that takes up space, has mass and can be touched is called matter. Matter exists in four states: 1 Solids-possess particles held together by strong forces. Solids have definite shape and definite volume. Solids cannot be compressed (squashed). 2 Liquids-possess particles held together by weaker forces than in solids. Liquids have definite volume but no shape-they take the shape of the container they are in. Liquids are hard to compress. Some solids are heavy and some are light. Some solids can .~=-=", and others will if you bend

3 Gases-possess particles that are free to move about with no forces holding them together. Gases have no definite shape and no definite volume. Gases can be compressed easily. 4 Plasma-exists only at very high temperatures. When gases are heated to over 6000°C, they change to plasma state. When electricity es through a fluorescent tube, it charges the gas inside the tube and creates glowing plasma. The inside of the Sun, lightning bolts and auroras contain plasma.

Liquids have no shape of their own. All liquids can be poured. Some liquids are thicker than others.

Gases have no shape. Birds and kites fly through gases we call air.

~-

Liquids and solids

Smells are gases which have moved through spread out

Figure 3.1.1 Features of solids, liquids and gases

Changes of state Matter can change from one state to another when the temperature is changed. The different changes of state are: 1 Melting-a change from a solid to liquid. When ice melts it forms water. 2 Vaporisation-the change from a liquid to gas. When water boils it forms water vapour, which is a gas. Not all liquids have to be boiled before they vaporise. Spilt petrol vaporises quickly. Vaporisation without boiling is called evaporation. 3 Condensation-the change from a gas into a liquid.

4 Solidification-when a liquid is cooled it changes to solid state. When water turns into a solid (ice) it is called freezing. 5 Sublimation- the change from solid to gas, without melting. A brick of dry ice (frozen carbon dioxide) changes to carbon dioxide gas without melting. Mothballs also sublime. water vapour escapes out the spout, but condenses in the cool air boiling water bubbles are made of water vapour Figure 3.1.2 Steam from a kettle is really tiny drops of liquid water

36

I


Complete the following:

Science fact

Matter exists as solids, liquids, and

Is glass a solid or liquid?

There is a fourth state called

Some people refer to glass as a 'supercooled liquid'. But when you touch a window or a mirror, glass feels solid. Is glass a solid or a liquid? Glass is a noncrystalline material that has no regular arrangement in its molecular structure. At room temperature, glass is a solid but when heated to high temperature it changes to a thick liquid.

Solids have definite

. and definite

Liquids have definite :

but no definite

Gases have no definite

. and no definite

All substances can

their

can be compressed easily but

and

. cannot.

Questions Fill in the missing labels for the names of the changes of state.

2 Name the change of state and the process taking place in the following examples: Example

(or freezing) Figure 3.1 .3

Change of 5tate

Proce55

A block of ice left in the Sun Wet clothes drying in the Sun Drops of water collecting outside of a cold glass of drink Spilt petrol drying up Making ice in the refrigerator Dry ice turning into carbon dioxide gas

:3 Look at figure 3.1.1, which has features of solids, liquids and gases, and find the relevant example: Feature

Example

A liquid that is hard to pour A liquid that has a solid dissolved in it A gas that smells A solid that is made up of little grains Solid that is light Substance that can be squashed

The Particle Theory

I

37

The particle theory Solids, liquids and gases are made up of tiny particles. The idea of particles is used to explain the features of solids, liquids and gases. The particle idea is a scientific model, which is a way of letting us imagine what is happening when we cannot see it. The particle model is sometimes called the particle theory of matter.

Solid-particles vibrate but cannot move away because they are held tightly by other particles. Solids keep their shape.

Crystals are unusually shaped solids. The shape of crystals can be explained by the pattern of particles inside them. Different crystals have different particle arrangements and have different shapes and colours. For example, copper (II) sulfate crystals are blue and diamond shaped.

Liquid- particles move about but stay held to other particles. Liquid is a state of matter that takes the shape of the container it is in.

Gas- particles move freely and are not held by other particles. Gas is a state of matter that has no shape.

Figure 3.2.1 Particle models of a solid, a liquid and a gas

Experi ment: Growing crysta ls Aim : To grow crystals from table salt and copper (II) sulfate. Mat erials: Black construction paper, scissors, two Petri dishes, warm water, two 100 mL beakers, table salt, copper (II) sulfate, a glass rod and a stereomicroscope. Meth od :

Results: After a few days, observe both types of crystals under a stereomicroscope and draw their shapes.

Cut the black paper into two circles so that they will fit the bottom of two Petri dishes. 2 Add one tablespoon of table salt to a beaker filled with 25 mL of warm water. Stir until

Table salt crystals

Copper sulfate crystals


the salt is dissolved. Add some more table

What is the colour and shape of table salt

salt until there is some salt left in the

crystals'?

solution that won't dissolve. You have prepared a saturated solution. 3 Pour the salty water onto the black paper in a Petri dish. 4

sulfate crystals'?

Put the dish in open air for a few days and observe what happens to the solution.

5 Repeat steps 2 to 4 with copper (II) sulfate.

38

2 What is the shape and colour of copper (II)

I


3 How did their shape and size change from day 1 to day4'?

Complete the following: Solids, liquids and gases are made up of tiny The idea of particles is used to explain the

of solids, liquids and gases. theory of

The particle model is sometimes called the Crystals are unusually shaped

. The shape of crystals can be explained by the pattern of

inside them . Different crystals have different particle

and have different shapes and

Questions 1 Which of the three main states of matter best matches each description'?

Dee;cription

State of matter

a Has no shape of its own but the particles stay together. b Has no shape of its own and the particles move away from each other.

c Has particles which vibrate but do not change position. d Is also called vapour.

e Formed by the evaporation of the liqUid. f

Forms when a gas is cooled.

2 Fill in the missing labels in the diagram below. • A, Band C are the three states of matter • D, E, F and G are changes of state • H and I relate to the change in the amount of energy

H

•

[~J Figure 3.2.2

c

B

A

>

~;

•

0° 0

0 ))

~

..:

3 Some substances are a combination of states. What states of matter are in: a honeycomb in a bee hive?

b lemonade'?

The Particle Theory

I

39

Properties of matter The particle theory of matter states that everything is made up of particles which are in constant motion. The theory can be used to explain different properties of maUer. Mass is the amount of matter, or particles, in a substance or an object. It depends on two things: • The number of particles. Materials with a lot of particles have a large mass. • The heaviness of each particle. Materials with heavy particles have a large mass. Compressibility means squashiness. In solids there is hardly any space between the

Gas in bike pump \\\

0

tz\' 'i'

e:::

0 \~ e 0= C::: e-:::. t'i

/'i

--

particles, so they cannot be compressed. Liquids are also hard to compress because their particles don't have much space between them. Gases can be compressed easily because there is space between the particles. The concentration of a solution is a measure of how much of a substance (solute) is present in a certain amount of liquid (solvent). A concentrated dye solution has many dye particles mixed with the water particles. If you add more water to the dye solution, you dilute it, decreasing its concentration.

Liquid in bike pump

--

Gas can be compressed (squashed) because there is space between the particles. The particles are pushed closer together.

Liquids cannot be compressed (squashed) because there is no space between the particles. The particles do not squash.

Figure 3.3.1 Explaining compressibility

Experiment: A dilution series Aim: fo make dilute solutions from a concentrated solution and investigate how the number of particles differs in these solut;ions by observing the co lour changes in the liqu ids. Materials: 10 mL measuring cylinder, 100 mL measuring cylinder, two 200 mL beakers, food dye in a bottle with a dropper, six test tubes, a test tube rack and tap water. Method: 1 Place 6 test tubes in a test tube stand and label them A to E. 2 Put 10 drops of food dye into the 100 mL cyl inder. Fill the cylinder with water to make 100 mL solution .

40

I


:3 Pour 10 mL of this solution into test tube A and keep another 1.0 mL in the 10 mL cylinder. Pour the rest of the solution int o the sink and wash the large measuring cylinder. 4 Pour the solution from the 10 mL cylinder into the large measuring cylinder, and add 90 mL . of tap water. Rinse the 10 mL cylinder. 5 Pour 10 mL of the new solution into test tube B and keep 10 mL in tho; 10 mL cylinder. Aga in, pour the rest of the solution into the sink and wash the measuring cylinder. fhis new solution is not as concentrated or coloured as solution A. 6 Repeat this procedure four more times, diluting the solutions more and more each time, and placing solution samples in test tubes C to F.

90 mL water

90 mL water

90 mL water

90 mL water

10 mL pale red solution

90 mL water

10 mL pale pink solution

~ "

~

sample in test tube F

Figure 3.3.2

Results: Compare the colours in each test tube in the dilution series shown below, and rate the solutions using the following scale: rate the solution 1 if it is very concentrated and 6 if it is very diluted.

2 Why is there less colour in dilute solutions compared with the concentrated solution? Expla in using your knowledge of the particle . theory.

Figure 3.3.3 C

D

E

Conclusion : What conclus ion can be drawn from this experiment about the number of particles in dilute and concentrated solutions?

F

Discussion:

What happened to the colour of the solution as it was diluted? Explain .

Questions Match the following to the definitions below: particle theory of matter; mass,

3 The drawing below shows the particles in foam

compressibility, concentration.

rubber. Use the drawing to explain:

a It is a measure of how much of a substance is present in 'a certain amount

a why foam can be compressed .

.~',~""",,-~'

l.

of water.

b It mea ns the squashiness. Solids anld liquids ,cannot be compressed but gases b why foam is not heavy. ,

can be compressed.

c It is the amount of matter, or particles, in a substance. d Everything that we know about solids, liquids and gases can be explained using this idea. 2 Give two reasons why a piece of lead is heavier that a piece of ice the sa me size.

......."""""-...-:

Figure 3.3.4

The Particle Theory

I

41

More about the particle theory In this section we will look at three more properties of matter and how they relate to the particle theory. Diffusion is the name for the spreading out of the substance. Diffusion is: • fast in gases-the particles move quickly and can travel a great distance • slower in liquids-the particles do not move very far before colliding with another particle • much slower in solids-the particles do not move. Hardness-a hard substance will scratch a soft substance. In hard substances, the particles are held

together very tightly, so they cannot be scratched or pulled off. In a soft substance the particles are held loosely, and they can be pushed off easily.

Science fact Diamond is the hardest known mineral. It is often used in industry for cutting. Density is the mass of a substance per unit of volume . It depends on the number and heaviness of particles in a given space or volume. To find density of any object, first find the mass, find the volume, then divide the mass by the volume. density = mass/volume

Explain the movement of particles in the following diagrams. Gas ~o

Liquid

1/

c)=:;

1:'

~~

'20

'20

••• e

:::.\"\<

0::: e~

Solid ~---~

• •• <» 0 • • • •" • •• 0

G

0 0

Figure 3.4.1 Explaining diffusion

Experiment: Measuring density Aim: To determine the density of some rectangu lar objects. Material5: A brick, a book, a piece of foam rubber and a piece of wood, a ruler and a' beam balance Method : 1 Measure the mass of each object in grams and measure its length, width and height in centimetres. 2 Calculate the volume of each object by using the formula : I x w x h = v. The volume will be in cubic cent.imetres. :3 Calculate the density of each object by using the formula : density = mass/volume.

42

I


Re5ult5: Object

Oimen5ion5 I, w, h (cm)

Ma66 (g)

Brick Book Foam rubber Wood Di5CU56ion: Which object has the following: a the greatest density'? b the lowest density'?

Volume Ix w xh (cm 3)

=

=

Oen6ity ma66/vo/ (g/cm3)

Concl usion :

2 Did all the solid objects that you measured -

How is the density of a solid rectangular

have the same density? Explain.

object calculated? .

\

i

;-

=

•

L

Activity: Observing diffusion in liquid Fill a large beaker with water. Let the water settle for about 5 minutes, without disturbing it. Add two drops of red food dye and observe how the food dye diffuses into the water. Describe your observations.

Figure 3.4.2 Dye diffusing through water

Questions Match the following with the definitions by placing the number agajnst the letter:

Definitione;

A Hardness

1 It's the name of the spreading of a substance

B Diffusion

2 It compares the mass of objects that have the same size

C Density

3 When particles are held together tightly and cannot be pulled off easily.

Ane;wer

2 Rank these states of matter in order of speed of diffusion (1 liquid

Solid

=fastest, 3 = slowest):

Gas

3 Use.the particle theory to compare how strongly the particles are held together in concrete and chalk. How particlee; are held together

Object

Concrete Chalk 4 Use the particle theory to compare the density of lead and foam rubber. Consider the heaviness and closeness of the particles. Object

I

Den.;ty

Lead Foam rubber

The Particle Theory

I

43

Energy in particles Particles need energy to be able to move. When energy is added to a substance, the particles in the substance move faster. Moving energy is called kinetic energy. When a substance is heated, heat energy is added, which is changed to kinetic energy and makes the particles move faster. Which beaker in Figure 3.5.1 contains cold water and which contains hot water?

Figure 3.5.2 An energy ladder

• To change from a solid to a liquid, or from a liquid to gas, energy has to be available. This is like going up the energy ladder. • With the change from gas to liquid; or from liquid to solid, energy is released. This is like going down the ladder. Every time there is a change in state, there is a change in energy. In the diagram below, the energy ladder goes sideways.

water

Figure 3.5.1 Hot and cold liquids

The difference in the speed of the particles can be seen by the diffusion of dye in water. The faster the particles move, the faster the diffusion. Particles in gases have more energy than particles in liquids, and particles in liquids have more energy than particles in solids. This is shown in the energy ladder. Complete the labels in figure 3.5.2.

more heat energy

~

liquid boils, vaporises or evaporates solid liquid heattaken away, gets colder, liquid freezes, or solidifies ~

low temperatures

gas

high temperatures

~

Figure 3.5.3 The energy in changes of state

Experiment: Change of state Aim: 1 To investigate heat energy in boiling water. 2 To observe how water changes its state, from liquid water to water vapour. Materiala: Bunsen burner, tripod, ga uze mat, 500 mL beaker, Celsius thermometer, a retort st and with a clamp, heat mat, stopwatch or wal l clock, felt-tip pen and safety glasses. Method: 1 Set up the experiment as shown in the diagram. Pour 350 mL of tap water into the beaker and clamp t he t hermometer securely

44

I


to the retort stand. Remembe r to wea r safety glasses. 2 Mark on the outside of the beaker with a felt-tip pen where the water level co mes up t o. :3 Heat water from room temperature until it is boiling, and continue heating fo r furthe r ten minutes. When the water starts bo il ing, record the temperatu re of the water every minute for 10 minutes. 4 When the 10 mi nutes are up, mark on the outside of the beaker where the wat er level is.

<

;

Results: Complete the table. "

Time from when water starts boiling (min)

Complete the missing labels:

Water temperature ("C)

0 1 stand

2 3

4 C::::::~~~~:::,- -

gauze

5

tripod

6 7

burner

8 9 10 Discussion and conclusion:

What is the highest temperature reached by the boiling water?

4 Wh<:lt happens to the water level as the

2 Does it change while you heat for a further ten minutes?

water boils? 5 What happens to the water when it is heated?

3 What happens to the heat energy after the

Does it change its state?

water boils?

Complete the following When you heat

water, you add

The

energy in the

To

from a solid to

energy the ;

and make

has gone into the

. The change from gas to

water. energy of the

has to be available. This is like going releases

the

. This is like going

ladder.

Questions When a substance is heated, where does the energy go?

2 How are the particles different in hot water compared to cold water?

3 Which state, solid or liquid, has the most energy inside it? 4 Which has the most energy in it : boiling water at 100°C or water vapour at 100°C?

5 Why is diffusion faster in hot water than in cold water?

The Particle Theory

I

45

Particles and pressure Each particle in a gas has energy and can push against anything that it hits. In a gas the particles are very tiny, so their energy is very small. But there can be billions of particles in just 1 mL of gas. The total push of these particles is very big. It is called gas pressure. In air it is called air pressure.

Gas pressure depends on: • the number of gas particles-the more particles there are, the more they push and the greater the pressure • the speed (energy) of the particles-fast particles are at a higher temperature and push harder than slow particles.

Teacher demonstrations: Pressure Blowing up a balloon Take a balloon and blow it up until it is fully inflated. Tie up with a string and notice the shape and size of the balloon. Take another balloon and blow it up until it is about half full. Figure 3.6.2 Flask and balloon experiment

Balloon 1

Balloon 2

Questions:

When the gas in the flask was heated, the gas particles started to move and take up

space, so the balloon

got 2 When the flask was cooled, the gas particles Figure 3.6.1 The more particles there are in the balloon, the bigger it gets

Balloon 1 has

gas particles inside

it, and there is more

inside

the balloon pressing on the balloon skin . . 2 Balloon 2 has

gas particles and . air pressure inside the

balloon pressing on the balloon

so

it is smaller.

Pressure and temperature Obtain two flasks and fit a balloon over the top of each flask. Each flask contains only air. Place the first flask into a beaker of warm water. This warms the gas and the gas particles move faster, Notice the shape and size of the balloon . Put the second flask into a refrigerator orfreezer. After ten minutes observe the shape and size of this balloon.

46

I

ard took up less space.

Water pressure

Questions:

there is

moved


Take an empty drink bottle and puhch three holes in a line down one side of the bottle. Place your fingers on the holes and fill the bottle with coloured water. Take your fingers off the holes and observe whether the water comes out of each hole with the same force. Questions: 1 Draw how the water comes out of each hole in Figure 3.6.3. 2 Water comes out with greater force from hole because the pressure with depth . Figure 3.6.3 Coloured water experiment

When a tyre goes flat, it has lost most of its air. There are no longer enough air particles inside the tyre to push it outwards. An aerosol can contains gas at high pressure. There is a lot of gas compressed in the can. The valve on top is like a gate that lets the particles out. When you release the valve, some gas particles are pushed out by the other particles.

The constant fast motion of the gas particles causes the pressure in an aerosol can compressed gas particles Figure 3.6.4 Gas particles in an aerosol can

Complete the following: Each particle in a gas has There can be The total

and can

of

in just 1 mL of gas.

of all these

called

against anything that it

is very big. It is called gas

. Gas pressure depends on the

. In air it is

of gas particles and the

or energy of the gas particles. When a tyre goes flat, it has lost most of its

. There are no longer enough

to push An aerosol can contains

at

pressure. There is a lot of gas

in

the can.

Questions 1 What causes gas pressure'?

2 Gas pressure depends on two features of the gas particles. What are these'?

:3 An inflated balloon is larger on a hot day than a cold day. But it has the same mass. Explain the reason for this. ~ -=="""""--"""""""""'~

4 What happens when a tyre goes flat'? How Gould you fix a flat tyre'?

5 Why is a jumping castle so soft to fall onto'?

The Particle Theory

I

47

Effects of heat All substances expand when they are heated and take up more volume. Gases expand the most, then liquids, and solids expand by the least amount. The expansion happens because the particles vibrate harder or move faster and need more space to move in. This pushes the particles further apart from each other. Expansion with temperature has some important applications. Allowance has to be made for expansion and contraction in building bridges, buildings and other structures. • If a metal bar is heated it gets longer, wider and thicker. • A 30 m steel bridge can be 10 mm longer on a hot day than on a cold day. • A thermometer works because the liquid inside it expands as it gets hotter. • Road bridges have fingerplates, which has parts that come close together on a hot day (because the metal expands) and move apart on a cold day (because the metal contracts). This prevents the road surface from cracking.

Figure 3.7.1 A fingerplate on a road bridge

Teacher demonstrations: Expansion and contraction

glass tube bored cork

Expansion in a liquid Fill a flask with cold tap water. Add 10 drops of food colour to the water. Close the flask with the rubber stopper and insert the glass tube into the hole in the rubber stopper. 2 Note the level of water in the glass tubing before heating. Heat the water until it starts to boil and note the level of water. . :3 Cool the water for 10 minutes and observe the level of water again.

flask Figure 3.7.2

Questions:

What happened when the water was heated and cooled?

48

I


2 What happens to the particles, as the water gets hotter?

Expansion in a solid Your teacher will set up the experiment with the metal bar as shown in f igure 3 .7.3. Observe the position of the pointer before heating. 2 Heat the rod for 5 minutes and note the position of the pointer. 3 Cool the rod for 5 minutes and note the position of the pointer again.

the metal bar is secured at one end, and the other end pushes against a pOinter

L

metal bar

screw to stop this end of bar moving Figure 3.7.3

Questions!

What happened when the metal rod was heated and coo led?

Questions Exp lain, using t he idea of particles, why substances expand as they get hotter.

2 A ball and ring apparatus is used to show expansion of a metal with heat.

~======~=~ Figure 3.7.4

The ball is made so that it just fits through the hole in t he ring. The ball and ring are made of t he same met al. Explain what happens in the following cases:

2 What happened to the particles in the metal rod as it was heated and cooled?

3 Use the concepts of expansion and contraction to expla in the reasons for the fol lowing: Example

Reason

Overhead cables are hung loosely, so that they droop down a little Railway tracks were once laid with a gap between the ends of rails

I

Concrete paths sometimes have black strips between the sections Road bridges have fingerplates

a the ball is heated but-not the ring.

b The ring is heated but not the ball.

The Particle Theory

I

49

Review and research Review questions

e is made by the process of condensation

Identify the state of matter that has the following properties.

f

a diffuses the fastest

g has no shape but the particles are held

. b maintains its shape

forms when a solid sublimes

together tightly

c contains the most energy in the particles

h vaporises to form a gas requires energy so it can change to liquid

d is made of slowly vibrating particles 2 Match the word with the correct meaning by placing the number against the letter. Word

Meaning

A Sublimation

1 Spreading out without stirring

B Diffusion

2 An increase in size

C Mass

:3 How easily something is scratched

D Compressibility

4 Ability to be squashed

E Hardness

5 The amount of matter

F Gas pressure

6 Change from solid to gas without melting

G Expansion

7 Caused by the force of gas particles as they collide

Am;wer

Thinking questions Sometimes a metal lid can stick tightly onto a glass jar. The lid can be loosened by running it under hot water. Explain why this happens.

2 Why does warm honey pour from a jar more easily than cold honey?

:3 A bag filled with carbon dioxide is heavier than the same bag f illed with helium gas. Both gases have the same number of particles in the same sized bag. Why is the bag of carbon dioxide heavier than the bag of helium?

4 Why do ice blocks melt faster on a hot day than on a co ld day?

5 Why does water evaporate more quickly from a flask with a wide top than from a flask with a small narrow neck?

50

I


Extension experiment: Make your own thermometer Ai m: To make a water thermometer and calibrate it (= put a scale on it). Materials: A large test tube, a test tube rack, an airtight cork with a hole, co loured water, a 100 mL beaker, ice, Bunsen burner, tripod, gauze mat, heat mat, waterproof coloured pen, matches and a laboratory thermometer. Method: 1 Half fill the test tube with coloured water and place the cork in the top. Insert the glass tube inside the cork so that some coloured water is in the glass tube. 2 Mark on the glass tube where the water comes up to. Label the mark with the current room temperature in °C. (Check the laboratory thermometer.) :3 Place the test tube in iced water in a beaker. 4 Note the level of the water in the glass tube and put a mark on the glass tube-label it O°C. 5 Then place a beaker with tap water on the tripod and heat the water until it boils. Place the test tube inside the beaker. 6 When the water boils, mark the level of water in the glass tube and label it 100°C. Compare your markings with a laboratory thermometer. Results: Draw and label a diagram of your water thermometer and include your calibrations (the scale you marked on the tube) for room temperature, freezing water and boiling water.

Water thermometer


What happened to the level of water in the glass tube when the test tube was placed in iced water? 2 What happened to the level of water in the glass tube when the water.was heated?

:3 Does your calibration (scale) resemble the calibration on the laboratory thermometer? If not, explain why it could be different.

=

Research question

Mind map

The particle theory of matter can explain how

Draw a mind map of the important ideas in this chapter in your notebook.

microwave ovens heat food . Research and report (in your notebook) on how microwave ovens work.

Word check Write the meanings aerosol compressibil ity concentration condensation

of these worrs crystals diffusion density evaporation

in your notebook. expand freezing gas gas pressure

hardness kinetic energy liquid mass melting

particles plasma pressure scientific model solid

solidification states of matter sublimation vaporisation

The Particle Theory

I

51

CHAPTER 4: SEPARATING MIXTURES

Why separate? Most substances we find on Earth are mixtures. Separating mixtures is important because there are many uses for the new substances that are produced, for example, petrol is separated from crude oil and used widely in our society. A pure substance consists of only one type of particle. A pure substance becomes impure when it has at least a small amount of another substance mixed in with it. This other substance is called an impurity. Mixtures are made of two or more substances mixed together.

[~••-:]

Special techniques such as filtering and crystallising are used to separate mixtures. Sometimes we need to make mixtures instead of separating them. Glass, paint, concrete and food are examples of useful mixtures. In figure 4.1.1, two different particles are represented by the symbols 0 and D. Identify which of the substances below are pure, mixtures or impure substances.

lCif

m

Figure 4.1.1

Complete the following: consists of only one type of

A pure

. A pure substance becomes substance mixed in with it. This

when it has a small amount of

are made of .

other substance is called an

or

mixed together.

more

4 Why is hydrogen a pure substance'?

Questions

~

Write the definitions of the following :

e

I

e~Ddi)

a Pure substance:

Ii

~

Hydrogen gas

b Impure substance: __..._""===..."""'~-=="""""~

5 The diagram represents a mixture of two c Impurity:

.-----=

liquids. How would you separate them if the ""'......,"""""=~

. 2 Why is separat ing substances useful to our society'? Provide an example.

3 Name some useful mixtures. .

52

I


black balls boil at 50"C and t he white ba lls boil at 150°C'?

Filtering and sieving filter paper residue

• •i- filtrate Figure 4.2.1

Filtration is like sieving and straining. You can use filtering to separate soluble and insoluble substances, such as sugar and chalk. Filter paper is like a sieve with tiny holes. Chalk (insoluble) will stay on the filter paper-it is called the residue. Sugar solution es through the

Experiment: Sieving two solids Aim: To separate a mixture of sand and beanbag beads by using a sieve. Materials: 1 large and 1 small beaker, fly screen mesh, a mixture of sand and beanbag beads. Method: 1 Using a flyscreen mesh make a sieve as shown in the figure below. 2 Place the sieve on the large beaker and pour the mixture of sand and beanbag beads through the sieve.

filter paper-it is called the filtrate. There are many filters around us, such as tea strainers and lint filters in clothes dryers.

\

\

/

.

. . : e---,t- residue

\<.• : •.• i '" filter paper \" • . • ..f- filtrate

-

. \ holes in paper

\. \ •• /

V Figure 4.2.2

:3 Observe what is left on the sieve and what collects in the beaker. Results: Label the diagram (figure 4.2.3) to show what collected in the large beaker and what was left in the sieve. Discussion: What difference between the beads and sand enabled you to separate them with a sieve'?

2 What is the best way to make the sand through the sieve as quickly

a~

possible'?

Conclusion: Explain why a flyscreen could be

used as a sieve to separate the mixture of sand and bean bag beads. staple or paper Figure 4.2.3

Science fact

Question

Colloids

State what is left in the filter/strainer as residue and what es through as filtrate.

Sometimes solutions can't be filtered because the. particles in them are too. small and through the holes in the filter paper. These solutions are called colloids. Particles in colloids are very tiny, evenly distributed in the mixture, and do not settle to the bottom of a container. Muddy water is an example of a colloid.

Filter/strainer

Residue

Filtrate

tea strainer lemon squeezer filter bag in a vacuum cleaner

Separating Mixtures

I

53

Magnetic separation Magnetic substances are attracted to a magnet. They are made of iron or a mixture containing iron. Magnetism can be used to separate magnetic and non-magnetic objects. Some examples are: • iron paper clips from brass ones • iron hooks from plastic pegs. Magnetic separators are used in factories. Some beach sands contain magnetic grains that are useful minerals-they are separated from the other grains with a magnetic roller.

roller with magnets in it

r \

. Figure 4.3.1 How the minerals in beach sands are separated

Experiment: Separating iron filings Aim: To separate a mixture of iron filings and powdery chalk. Materials: a large test tube, a bar magnet, mixture of chalk and iron filings Method: Fill in the gaps. 1

Place iron filings and

' powder

mixture in a test tube. 2 Hold the

below the test

Figure 4.3.2

tube and move the magnet across the test tube and observe which substance the magnet

and which

substance is left behind. Results: Label the diagram (figure 4.3.2) of the test tube after separation. Discussion: Which is the magnetic substance and which is the non-magnetic substance in this mixture'? How do you know'?

ConclU!~ ion:

What is the advantage of using a magnet in separating magnetic and nonmagnetic substances'?

F

It!!!'!

iL

. -..

Activity: Magnetise a nail , Magnetise and demagnetise a large nail by stroking it with a permanent magnet. Test the magnetism using paper clips or pins. Then drop it or hit it to destroy the magnetism.

54

I


Copy and complete: Magnetic substances are attracted to a

. They are made of

or a mixture

containing can be used to separate magnetic and Magnetic grains that are useful

objects.

are separated from other grains with a

Science fact

Question: What is the advantage of using an

Magnetic separation in industry

electromagnet instead of a permanent magnet?

..

Wrapping a coil of wire around iron makes an electromagnet. When electricity flows through the wire, magnetism is produced and this magnetises the iron. When the electricity is turned off the magnetism disappears. Electromagnets can be used to separate scrap iron from non-magnetic materials. Huge electromagnets are used in scrap yards and other industries.

Figure 4.3.3 A scrapyard electromagnet

Questions

3 Sand and salt are separated by filtration.

Which of these substances would be attracted to a magnet?

What steps, and in what order, would you use to separate a mixture of iron filings, sand and salt?

Substances

Attracted by magnet

Brass drawing pin A plastic sieve Filter paper Nails used in building Filter funnel Retort stand Tripod stand Beaker 2 If you owned a large factory and had to separate thousands of tonnes of iron

i

-= :-=: ':::l

:::::: :=: ::~ ;s;G.1§i

c

WiIiP:!i;,;a;;;;p!l."'jINO

AW..,

nails from matchsticks, explain how you could do it.

Separating Mixtures

I

55

~

Sedimentation and flotation Sedimentation When you mix chalk with water it does not dissolve-it forms a suspension. When it is left undisturbed the chalk settles to the bottom of the container. This process of letting an insoluble substance settle is called sedimentation. Large, heavy particles settle more quickly than small, light particles. Question: Identify the st ages of sedimentation in these diagrams

~

EJ

example of a centrifuge. Dairy farmers use a centrifuge to separate cream from milk.

Flotation When a lighter substance floats on water, it is called flotation. For example, sawdust will float on water because it is lighter than water, but sand, which is heavier, will sink. Oil is lighter than water so it floats on top of water. Two liquids that do not mix can be separated by decanting or by using a separating funnel. The tap at the bottom can be opened to allow the heavier liqu~d to flow out. separating funnel

Figure 4.4.1

Decanting means pouring off a liquid to leave a sediment of insoluble substance behind in the container. Centrifuging speeds up the process of sedimentation. A laboratory centrifuge contains test tubes, which spin quickly. The heavier substances settle at the bottom of the test tubes. The spin dryer in a washing machine is an

Experiment:. Separating four substances Aim: To separate a mixture of sand, iron filings, sawdust and salt by using different tech niques of separating mixtures. . Materials: Sand, salt, sawdust, iron filings, water, magnet, a large beaker and a pa per towel.

Method: 1 Your task is to decide t he best method for separating the fou r substances. Use the properti es of the subst ances li sted in the ta bl e to help you . Plan t he method of separation and write it out in point form. Check the order of separation with your teac her before yo u start.

J - I--- oil -+--- water

'- sand Figure 4.4.2 Ways of separating by flotation

Properties of 6ub6tance6 Sub6tance Soluble in Float6 in water water

Magnetic

sand

no

no

no

salt

yes

no

no

sawd ust

no

yes

no

iron fil ings

no

no

yes

2 After you have separated the subst ances, show your teac her small pieces of paper towel with sand, iron fil ings and sawdust in them, and a sol ut ion of sa lt in a be
Tips • •

56

Sawdust soaks up water, then sinks. Do not leave the sawdust in the water for too long. Iron filings will rust if they get wet. Keep them dry.

I


Results: Complete the table.

Substance

4 Is it possible to separate salt from water?

How it was separated

sand

Conclusion: Explain your reasons for the order you chose for separating the substances.

salt sawdust iron filings

2

Discussion: What method was used to separate iron f il ings from the mixture'?

:3

2 What method was used to separate sand from sawdust?

:3 How was salt separated from sand?

Questions

4

Science fact

Write t he mea ni ngs of the fo llowing words:

Froth flotation

a suspension :

Froth flotation separates valuable metal ores from sand and rock. When kerosene is added, the ore is adsorbed onto kerosene. When kerosene is shaken or bubbles are blown through it, air bubbles with the Figure 4.4.3 kerosene and ore float to the top. The froth water can be skimmed metal ore off and recycled. and sand / This method is .f5i:G; ;"'; '..::~ :. ;;}: used to separate lead, zinc and air bubbles with kerosene copper ores from and metal ore sand and clay.

b sedimentation:

c decanting: 2 Give an example of the use of centrifuges.

:3 What is a separating funne l? Give.an --+- .water

example of something that it can be used to separate.

\WII!!.I!!!!!!!.~ sand

Question: Why does the kerosene float?

Separating Mixtures

I

57

Chromatography Chromatography is the separation of coloured chemicals such as dyes and inks. It works because some are more soluble than others. Paper chromatography uses paper to separate different dyes in a mixture. The most soluble dyes end up higher on the paper than the less soluble dyes. A special paper is used in paper chromatography, but filter paper can be used as well. The way to do paper chromatography is shown in figure 4.5.1.

your name and details Go:~e. in pencil --+- P eo

GoRee. Red

Peo

spot of ink or dye (watersoluble) solvent (e.g. water) Figure 4.5.1 Paper chromatography

Activity: Separating dyes with paper chromatography filter paper

Your teacher will set up two chromatography demonstrations, as shown in the diagrams, using ink or food dyes.. Draw on the filter paper in the diagrams how the colours in the dyes separated.

filter paper

spot of water soluble ink or dye

spot of water soluble ink or dye

Question: Which method was faster? Method A Paper strip cut to fit into test tube

Explain why.

Method B Strip folded from filter paper circle over a beaker or jar

Figure 4.5.2 Two paper chromatography methods

Experiment: Chromatography of food dyes Aim: To separate water-soluble dyes in smarties. Materials: Red, brown, yellow, green and blue smarties, 10 test tubes, a test tube rack, strips of filter paper. Method: 1 Place one smartie in a test tube and add enough water to cover it. Gently shake the test tube unti l the water is coloured . 2 Place one drop of the coloured water near the bot tom of a strip of filter paper as shown in figure 4 .5.1 . :3 Repeat steps 1-2 with 4 other coloured smarties.

58

I


4

Fill 5 test tubes with 1 cm water ana place the f ilt er paper strips so that the coloured dots are just above the water line. Results: Observe and record which food colours are used to make the outside of these smarties in the table. Colour of smarties

Red Brown Yellow Green Blue

Dyes in each smartie

Discussion: Describe what happened to the

Conclusion: What property of the colours

food colour on the filter paper when it was

caused them to separate?

-*--"."..,--...".=:

placed in water.

Complete the following: Chromatography is the separation of

chemicals such as

.. It works because some are more . Paper ' soluble dyes end up

and

than others. in a mixture. The most

uses paper to separate different

on the paper than the

Questions

solu ble dyes.

:3 When you write your name on the paper strips you use for chromatography, you

1 What is the meaning of chromatography?

should not use a biro or felt tip pen. Pencil is the best. Explain why. 2 Why are soluble dyes used in this method?

Science fact: Disposal of dyes and other hazardous substances Many substances, such as dyes, inks, detergents and other toxic chemicals should not be put in sinks or drains. The water from sinks goes to a waste treatment facility. When the water has been treated, it eventually reaches the sea or is used to irrigate land, and any remaining pollutants cause contamination. Toxic substances poison living organisms or damage their life processes. They not only kill the fish and aquatic life in water, but can also build up in.the tissues of organisms and can be harmful to humans or animals that eat them.

Question: Which substances should you avoid

putting in sinks at home and the science laboratory? Why?

'as

,. ~~==:-=-.

.:: :

= .... 'fi(;if

-=-,-"". - : : - -

=

:j I

Separating Mixtures

I

59

Adsorption Adsorption is the name given when something sticks on the outside of something else. (This is different from absorption, where the liquid soaks in, for example, when water soaks into a sponge.) Honey, glue and paint are sticky substances. Some substances are not sticky to us, but are sticky to dyes and many other chemicals. The chemicals stick to the outside of the tiny grains of the substances. For example, magnesium oxide is a white powder that is sticky to some types of food dye. The smaller the grains, the more chemicals that can stick to them. Charcoal that has been steamed or heated in a special way is called activated charcoal or

activated carbon. It is used in many factories to remove impurities. The impurities stick onto the outside of the tiny grains of carbon. Carbon removes brown colour from brown sugar when it is being converted into white sugar. Some water purifiers contain canisters of carbon, which the water es through. These purifiers both filter and adsorb to remove impurities. ; - The same grai~,

Large grain

magneSiU~ .. .. @@ @.~.. 0 ~ when ma~y crushed smaller mtp

of oXide

OIl>. GIl>. GIl>.'bifI ~ '!.!'

v

@~C'&P'@

O'@ @

grams, can absorb much more dye. Only a fraction of the grains are shown.

Figure 4.6.1 The surface area of grains depends on their size

Experiment: Taking colour out of water The colour or impurities in water sticks to magnesium oxide or activated charcoal. This is called adsorption. Aim: To remove red food dye and blue litmus dye from water by adsorption . Materials: Red food dye, a dropper, two 500 mL beakers, water, 100 mL measuring cylinder, magnesium oxide, a spatula, two filter papers, two funnels, blue litmus dye, activated carbon, Bunsen burner, tripod stand, gauze mat, heat mat, tongs.

:3 Add 5 drops of blue litmus solution to 50 mL water in a beaker. Add one level teaspoon of activated carbon. Stir the mixture and warm it gently, then filter it. 4 Observe the colour of the filtrate in the beaker and the residue 'on the filter paper. Results: Draw on the diagrams to show the colours of the residues in the filter paper and the colours of the filtrates. Complete- the labels. 1

filtrate:

Method: 1

Pour 200 mL of water in the beaker and add five drops of red food dye. Add a level teaspoon of white magnesium oxide powder to the water. Warm and stir the mixture for a few minutes, then filter it. 2 Observe the colour of the magnesium oxide in the filter paper and the colour of the filtrate in the beaker.

colour: 2

Figure 4.6.2


oxide colour:

filter

act;"ted colour:

colour:

60

o o

residue:

4

Discussion:

Did magnesium oxide adsorb the food dye

How effective is the adsorption process? Is the water colourless or tainted with colour?

colour? How do you know?

Conclusion: Summarise how colours or

2 Did the activated charcoal remove the blue colour from the water?

impurities can be removed from water by adsorption.

3 What was the colour of the f iltrate (water) after f ilteri ng?

Complete the following: is the name given when something Some substances are not

on the outside of something else.

to us, but are sticky to

Magnesiu m oxide is a

powder that is

Charcoal that has been

and many other

to some types of

or heated in a special way is called

dye. charcoal. It is

used in factories to remove

Questions: What are the meanings of adsorb and absorb?

5 The photog raph shows a firefighter wearing a gas mask. It works by filt~ation and d. '.

adsorption. Expla in how.

2 Do paper towels and charcoal adsorb or absorb?

3 How is act ivated charcoal different from normal charcoal?

4 One cure for an upset stomach is to stir some activated carbon in water and then drink it. What would this do in your stomach?

Figure 4.6.3 Firefighters wear gas masks so they don't inhale dangerous particles and gases

Separating Mixtures

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61

Ele ctrostati c se pa rati 0n When some types of objects are rubbed together, they produce static electricity. You can experience static electricity when you rub your feet on nylon carpet or run a comb through dry hair. Objects that have lots of static electricity can attract bits of paper, hair and grains of chemicals. This is another method of separation, called electrostatic separation. Electrostatic separators separate minerals of different electrical properties. This method is based on the fact that like charges repel and unlike charges attract. Some particles have positive charges, some have negative charges, and some particles have no charge. Particles with no charge are attracted to charged objects. Uncharged particles are not attracted to, or repelled from, other uncharged particles.

Electrostatic separators are used to separate valuable minerals, such as zircon, from beach sands. Zircon is used for making abrasives, paints, glass and rubber. Fill in the missing labels and arrows. positive +

.....

~

positive +

.....

positive +

repel negative

L...-_---JI

~

negative

negative

I no charge

I

I positive

I

+

Figure 4.7.1

Experiment: Electrostatic separation Aim: To separate paper and cardboard pieces, salt and pepper mixture by using electrostatic separation. Materials: A perspex rod, a piece of wool, tiny pieces of paper and cardboard mixture, table salt and whole peppercorns mixture, a watch glass and a spatula.

Methoa: 1

Rub the perspex rod with a piece of wool. Take this electrostatically ch8lrged rod near the paper and cardboard pieces and note wh ich ones are attracted by the charged rod. 2 Place a teaspoon of salt and pepper mixture in a watch glass and take the charged perspex rod near the mixture and observe which substance the charged rod attracts. 3 Hold the uncharged rod near the two mixtures and observe what happens.

62

I


Figure 4.7.2 Using a charged rod

Results: Write in the table what each rod attracted.

Mixturel3 l3eparated

Attracted by Attracted by charged rod uncharged rod

Pieces of paper and cardboard Salt and pepper mixture Discussion: Wh ich substances did the charged rod attract? Explain.

2 Which substances were not attracted to the

4 What happened when the uncharged rod was used?

charged rod? Explain.

Conclusion: How effective is electrostatics as a method of separation? '

3 How did you produce static electricity?

Complete the following: When some objects are rubbed together they produce Objects that have lots of

electricity can attract bits of

hair and

of chemicals. This is another method of Like

. It is called

repel and

separation .

charges attract. Particles with no charge are

attracted to charged objects.

Questions Which method can you use to separate tiny pieces of paper and cardboard?

3 Explain what happens in the following examples, by answering 'attract', 'repel' or 'nothing'. Examplel5 of chargel5

2 How does this method work?

What happens

positive and positive negative and negative negative and positive negative and uncharged uncharged and uncharged =

Science fact Electrostatic separators in chimneys In chimney smoke, some of the particles are charged, and are attracted to a charged grate or grill. When the particles touch the grate they fall downwards. This reduces the amount of smoke and ash going up the chimney. An electrostatic separator in a chimney has a charged grate that is connected to a battery so it does not lose its charge. Another method of removing particles from chimney smoke is filtration.

~"

.

Questions: 1 Why are the grates in electrostatic separators connected to a battery?

2 What would happen if they weren't?

3 What are two ways to remove smoke from a factory chimney?

Separating Mixtures

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63

Distillation Distillation is a process used to purify liquids. In distillation, a solution is boiled and the vapour is collected. The vapour is then cooled and condensed into a liquid, which is called the distillate. The simplest way of distilling a mixture is to a . flask connected to a test tube by a glass tube. The glass tube acts as a condenser. It is cooler than the vapour, so it condenses the vapour into a liquid.

points. The lower the boiling point, the higher in the column the vapours travel. The black circles represent tar and waxes, which melt but do not boil. In a real fractionating column, liquids are taken from the column at more than three places. ~_ _ _

o

~~ Tempe~at~re

0-

-

0-0

o

1000C

o 200°C

_

0

oQ

3000C o .

Lo.

0

.

0

0

0

L ()

~ 0 o. o.

o ... ~ 0

~r.>dLJ 400°C o

Another way of doing distillation in the laboratory is to use a Liebig condenser. This relies on tap water to cool the vapour back into a liquid. Distilling sea water to obtain pure drinking water is important on cruise ships. Removing the salt from sea water to obtain pure water is called desalination.

()

0

~_

00 oG

. 0 0

Figure 4.8.1 A distillation flask

0

-; -;;0 _

r& Gases, including ~

bottled gas, natural gas.

0

inSide _ _ 500C 0 0

liate

0

GG

Liq~ids w~th low bOiling pOint, such as petrol. .

Liquids such as

,&.. kerosene, used for ~

aviation fuel, plastics, other chemicals

....

Liquids with high boiling point, such as oil used for lubrication and fuel in furnaces.

• .....

o-!

... ••• •.

. ooo g Go

'~~~ ~o~ 0 .o I~ v• o.o ~o~

--.

'-_--:::- .... Solids, such as '--_....:.'--._ ..... asphalt, wax, grease. (These are molten in the fractionating Figure 4.8.2 Fractional column.) Crude oil is heated to 350°C

distillation of crude oil

Que6tion6! Which gases are recovered from crude oil'?

Fractional distillation Fractional distillation is a type of distillation that separates two or more liquids that are mixed together. Crude oil is oil that comes out of the ground. It is a mixture of chemicals such as petrol, tar, oil, dissolved gases and kerosene. Each liquid in the crude oil mixture has a different boiling point, which is used to separate the chemicals. The separation occurs in a fractionating column. In an oil refinery the fractionating column can be 40 m high. In figure 4.8.2, the gases in crude oil are shown as white circles. The different liquids rise to different heights, depending on their boiling

64

I


2 Which liquid has a low boiling point,?

3 Which liquids have a high boiling point,?

4 Which solids are recovered'?

5 What temperatures are used inside the column'?

Demonstration: Distillation Aim: To use distillation to extract

pure water from salt solution. Material5: Round bottomed flask with tube, rubber stopper, Bunsen burner, tripod, gauze mat, heat mat, two retort stands, two boss heads and clamp, Liebig condenser, 250 mL beaker, thermometer, prepared salt stand and solution and matches. Method: 1 Set up the apparatus as shown in figure 4 .8.3 ensuring that the Liebig condenser is connected to Figure 4.8.3 the tap. 2 Gently heat the salt solution without boil ing the flask dry. :3 Co llect the condensed liquid in the beaker. Re5ult5: Label the diagram (figure 4.8.3) . Di5cu55ion and conclu5ion:

for cooling water

2 Name the substance that collected in the beaker.

:3 What substance remained in the round bottomed flask?

What happened when the salt solution was heated'?

Complete the following: Di5tiliation is a process used to purify

. In distillation a solution is

is collected. The vapour is then cooled and Fractional

and the

into a liquid called distillate.

is a type of distillation that separates two or more

that are

mixed together

Questions

vaporisation. The words may be used more than once.

What is meant by distilled water'?

- 2 What is desalination?

4 What are some products that you have used recently which were separated from crude oil

:3 What are the changes in state that happen

by fractional distillation'?

during distillation'? Complete the diagram to show what happens. In the diagram, use the words condensation, liquid, vapour and

Separating Mixtures

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65

Physical and chemical changes Chemical changes

Properties are features of substances. Physical properties can be used to work out ~ow to separate different substances. The separatIOns we have studied in this section have relied on physical properties such as solubility, magnetism, flotation, adsorption onto carbon and electrostatics. Some separations change the substances. A new chemical is made. These changes are called chemical changes.

• New substances are formed and the process is often difficult to reverse. • Different types of particles regroup or rearrange themselves to form new substances. A new solid or liquid may be formed . Sometimes bubbles of gas are given off. • Colour and texture of the substance may change.

o

f) 0 ~(j O Q

Physical changes

O~O

• No new substances are formed. Particles do not change apart from gaining or losing energy. • Changes of state such as melting or boiling are physical changes and are easy to reverse. • The end product may not always look the same as the starting material. For example, when ice melts it forms water in a liquid form .

0000 0 000 00

G~D

00~Q~Q -- ~ Q{)~ ~ Cl [) (J [) () O . ~~()~ ~ :. PHYSICAL ~ SEPARATION

CHEMICAL ., ~ ~ SEPARATION _ , .

the chem ica l substances rema in the

the chem ica l substances are

,~

Figure 4.9.1 Physical and chemical changes

Experiment: Physical and chemical changes

:3 Test tube 2: place a small piece of wet steel wool and observe in a couple of days. 4 Test tube 3 : place a small piece of magnesium r ibbon and add 1 cm of hydrochloric acid . 5 Test t ube 4: add one· spatu la of sugar in 1 cm of water and st ir with a glass rod . 6 Test tube 5 : add 1 spatula of sugar and heat fo r 1 minute. 7 Test tube 6 : add 1 spatula of baking powder and 1 cm of vinegar. 8 Record all of your observations in the table, note if the reactions are reversible or irreversible. Identify the reactions as physical or chemica l changes.

Aim: To identify which of the following changes are physical changes or chemical changes. Materials: Ice cube, water, steel wool, magnesium, dilute hydrochloric acid, sugar, vinegar, baking powder, Bunsen burner, metal tongs, test tube rack, 6 test tubes, felt pen, spat ula, glass rod and matches. Method: 1 Place 6 test tubes in the test tube rack and label the m 1 to 6 with a felt pen . 2 Test tube 1: place crushed ice in test tube and observe in half an hour.

2

Figure 4.9.2

66

I


3

4

5

6

t.

Results:

Experimente

Obeervation

Change revereible or not

Type of changepnyeical or chemical

1 Crushed ice 2 Wet steel wool

:3 Add hydrochloric acid to magnesium 4 Sugar in water 5 Heat sugar 6 Add vinegar to baking powder Discussion and conclusion: Summa rise in your own words the difference between physical and chemical changes. .

Questions Complete the table to show the differences between physical and chemica l changes.

Propertiee

Phyeical changee

Chemical changee

Formation of a new substance Change in particles Reversibility of reaction "

2 Identify the fol lowing reactions as physica l or chemica l changes and give reasons for your choice.

Reactione

Type of change

Reaeon

Boiling water Boiling an egg Melting wax Baking a cake

:3 The rate of chemical reactions varies. Give an example of a fast and a slow chemical reaction . Fast reaction: . Slow reaction:

Separating Mixtures

I

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Research question

Choose the method ot separating the fo llowing mixtures: Mixture

Method of

An~wer

~eparation

Desalination is the process of removing sa lt from a salt solution, usua lly sea water. This process is a solution to the world's shortage of fresh water. The Midd le East produces half of the world's desalted water. Use Internet resources to investigate the operation of a large-scale desa lination plant. Discuss in detail the process used .

A Iron filings from dry sand

1 Chromatography

B Salt from sea water

2 Use a magnet

C Coloured dye from water

:3 Use a sieve

D Sawdust from sand

4 Centrifuging

In hospitals, blood ce ll s are sepa rated from blood serum using a centrifuge.

E Colours in biro ink

5 Distillation

a

F Cream from milk

6 Flotation

b Where in the centrifuge tubes wou ld you find the heavy parts of the blood?

GStones from sand

7 Crystallisation or evaporation

Thinking questions

H Pure water from 8 Adsorption sea water 2 Write the of the following meanings: Meaning

How does a centrif uge work?

2 You have purchased lawn fertiliser, and you think that there may be some sand in it. How could you quickly check for sand in the fertiliser? (Hint: lawn fertiliser is very soluble.)

Term

Dissolves in a liquid Does not dissolve in a liquid A solid dissolved in a liquid Fine, insoluble solid floats in the liquid Heavy, insoluble solid settles down in a liquid A solid that dissolves in a liquid A liquid in which the solute dissolves

:3 Rescue workers often wear gas masks when working in dangerous areas. The air they breathe is ed through a carbon -filled cartridge. The cartridges are replaced freque nt ly. a What is the purpose of the carbon cartridges?

A substance which is attracted by a magnet When a paper soaks up water

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b Why are they replaced?

"

4

State which one of the diagrams A, B, C and

d used to sepa rate chalk from water

D (below) is:

e used to crystallise copper sulfate from

a used to obtain salt from sea water,

water

b used to obtain fresh water from

f

sea water c

called decanting

h called distillation

used to separate sand from water

called filtration

1

o

o

c

B

A

D

5 Complete the table of properties of the fo llowing objects. Design a method you could use to separate them if they were all mixed together.

Object

Soluble Magnetic Floats in Method of water separation

Steel ball bearings glass marble (15 mm)

steel ball bearing (1 5 mm) o

bean bag bead (5 mm)

sugar grain (1 mm)

•

lead pellet (3 mm)

Glass marble Bean bag beads Sugar grains Lead pellets

Word check

Mind map

Write the meanings of these words in your notebook.

Draw a mind map in your notebook using all the used in separating mixtures.

absor ption

fi ltrate

particles

adsorption

flotation

sedimentation

activated charcoal

fractional distillation

sieve

centrifuge

froth flotation

solubility

chemical changes

impurity

solution

ch romatog ra phy

impure substance

suspension

colloids

insoluble

plasma

decantation

magnetic substances

pure substance

density

melting

vaporisation

electrostatic separation

mixture

filtering

physical properties

Separating Mixtures

I

69

CHAPTER 5: CELLS

Spontaneous generation Spontaneous generation means making living plants and animals from non -living objects. For thousands of years people believed that this happened. At the time, air was believed to contain a 'vital force' necessary to generate life spontaneously. • In the 1600s Jean-Baptiste van Helmont, a famous biologist, believed that if wheat seeds were wrapped in a smelly shirt and kept in the dark for a week, mice would come out of the seeds. It was also believed that maggots grew from rotting meat. • In 1668 sco Redi placed some meat in three jars. One jar was left open to the air, and the other two jars were covered with types of cloth. Redi watched flies walking on the meat in the open jar, and later maggots developed. On the other jars there had been no flies and no maggots grew. But the meat in the covered jars went bad, and the people who believed in spontaneous generation said that his experiment was a failure. • In 1767 Lazzaro Spallanzani discovered that if he boiled meat broth (soup) in a flask and then sealed it, the broth did not go bad. However, if the neck of the flask was broken, the broth went bad very quickly. He said that the life could not have come from the broth but from outside. • In 1862, the French chemist Louis Pasteur started the experiments that finally disproved

spontaneous generation. Pasteur lwpoth esised that reproductive cells called' spore were carried on dust particles in the air. The' developed into active microorganisms whe~ nutrients were available.

Pasteur's experiment Pasteur set up several flasks of meat broth. H boiled them until they were sterile (free frorr bacteria). One flask had its top drawn out into ar S shape. Although this flask was open to the ai so that the 'vital force' could get into it, the brott in it did not go bad. The dust and spores wen trapped in the S-bend. This experiment completed in 1864, finally disproved the idea 0 spontaneous generation. Pasteur showed that WE are surrounded by microscopic life. Pasteur'~ flasks are on display at the Pasteur Institute ir Paris. The broth is still sterile to this day.

Figure 5.1.1 Pasteur's flask

Science fact Pasteurisation Pasteurisation is the process of heating (milk, wine, etc.) to a high temperature, followed by rapid cooling, to destroy harmful bacteria. Without the process of pasteurisation, milk, wine, canned food and many other foods would quickly spoil. The pasteurisation process was developed by Louis Pasteur (1822-95). Question: Research the process of milk pasteurisation. Why is this process

important to consumers'?

------------------------~ Figure 5.1.2 Paste uri sed milk

70

[


Experiment: Pasteur's experiment Aim: To inves-tiga-te Pas-teur's-hypo-thesis abou-t spon-taneous genera-tion. Hypothesis: Microbes do not arise by spontaneous generation. Materials: sugar, sal-t, s-tock cube, 300 mL wa-ter, 500 mL measuring cylinder, 500 mL beaker, Bunsen b.urner, tripod, gauze ma-t, heat ma-t, spatula, 3 round bottomed flasks, 3 one holed rubber corks and 3 glass tubes of different shapes as shown in figure 5.1.3.

9~~

Results: Flask

Colour of the broth

Flask wi-th s-traight glass -tube Flask wi-th singlebend glass -tube Flask wi-th doublebend glass -tube Discussion:

Wha-t me-thods were used to ki ll the microbes in the broth and on the co rk'? '

Figure 5.1.3 The 3 tubes used in Pasteur's experiment

Method:

1 Pour 300 mL water into a beaker. Add 2 spoons of sugar, a pinch of salt and 1 s-tock cube and s-tir. Hea-t -the broth until the solids have dissolved. The solu-tion will be pale brown bu-t transparen-t (see--through). 2 Pour 100 mL of -the broth in-to each of -three flasks and boil -the broth to kill -the microbes in the broth. 3 Seal each flask wi-th a cork fitted with differen-t shaped glass tubing. Before put-ting the cork in the flask, hea-t -the bottom of the cork in the Bunsen burner flame for abou-t two seconds, to kill any microbes that could fall into the bro-th . This is called flaming . 4 Pu-t your name on each flask and put them in a warm place. After 24 hours, observe the colour of the bro-th. If it is cloudy there are bac-teria presen-t, if it is clear there are no bac-teria present.

Questions Explain wha-t is mean-t by spontaneous genera-tion .

2 Explain why maggo-ts appear in rotting mea-t,

2 In which flask(s) did -the bro-th stay clear'? Why'?

3 In which flask(s) did the bro-th -turn cloudy,? Why?

Conclusion: Did your experiment the

hypo-thesis'? Why'? tr

=

!!:

!I!~

3 Complete -the following -table.

Obe;ervat;ons Date Sc;ent;e;t 1600 Jean Baptiste van Helmont 1668 sco Redi

1862 Louis Pas-teur

according -to -the spontaneous generation -theory.

Cells

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71

What are cells? Cells are the smallest living part of a plant or animal. They are considered living because they take in nutrients, expel wastes, grow, reproduce themselves and respond to changes in their surroundings.

The discovery of cells Cells were not discovered until the invention of the microscope. The first double lens (compound) microscope was produced by Hans and Zacharias Janssen, Dutch technicians, in 1590. • In 1665 Robert Hooke, an English scientist, observed a very thin slice of cork with a microscope that he had built. Hooke saw lines of little boxes which he called cells. They reminded him of the rows of small rooms in jails-cells. • In 1675 Anton van Leeuwenhoek, a Dutch draper, viewed murky lake water with the microscope he made using a bead of glass as a lens. He discovered plants and animals made of just one cell, which were too small to be seen without a microscope. He began the study of microbiology. Before long, many people were making and using microscopes. The branch of science called microscopy developed. A microscopist is a person who has been educated to use a microscope. • In 1838 Matthias Schleiden, a German botanist, studied plant structure and concluded that all plants are composed of cells and that cells are the basis of a plant's functions.

lO}O)

~.

skin cells protect inner layers

• In 1839 Theodor Schwann, a German physiologist, made the same conclusions about animals.' ;• In 1858 Rudolf Virchow, another German physiologist, stated that all cells come from other living cells. The discoveries of other scientists and the generalisations made by Schleiden, Schwann and Virchow came to form the basis of the cell theory.

The modern cell theory states: • All living things are composed of one or more cells or cell fragments. • The cell is the organism's basic unit of structure and function. • All cells arise from other cells.

How cells are arranged The human body is made of about one billion cells. We all started as one cell, called an ovum or egg, which was fertilised by a sperm. This cell (the fertilised egg) divided to make two cells, then four cells, and so on. Eventually a multicellular embryo formed. This process is called cell division. As embryos grow in size, the cells in them start to develop into different types and specialise, for example blood, stomach, muscle and nerve cells in humans. Different types of cells look different because they carry out different functions within an organism. The structure of a cell enables it to carry out its special function. This is called cell specialisation. ~

@ @@

~

white blood cells fight -disease

smooth muscle cells contract and bring about movement

~~

@§)

nUUCI messages

@) c::::::::::, @ liver, and stomach cells help obtain en~rgy from food

Figure 5.2.1 The different cells in the human body and their functions

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I


skeletal muscle cells provide and movement

Complete the following living ~art of a

Cells are the that all

or

. The modern cell theory states

things are composed of unit of

and

Different types of ce,lls look

or . All cells

cells. The cell is the organism's from

because they carry out different

organism. This is cal led cell

cells. within an 'j

Questions Who discovered cells and why did he call them that?

2 Refer to figure 5.1.1 and state the functions of the cells listed in the table. Typel5 of celll5

Functionl5

Skin cells Liver and stomach cells

Science fact

White blood cells

Size of cells Cells vary in size as well as shape, Bacteria

Nerve cells Smooth muscle cells

Skeletal muscle cells

:3 Draw the following cells: a a smooth muscle cell b a white blood cell .

are among the smallest cells. Twenty thousand bacterial cells, in a line or row, would measure approximately one centimetre. A human egg cell is large by comparison, measuring nearly a millimetre in diameter. Ten egg cells in a row or line would measure approximately one centimetre. Egg cells contain yolk, which 'provides nutrients for a growing foetus, whereas bacterial cells need to obtain their nutrients from an outside source. Question: Why is an egg cell able to grow

c a nerve cel l

larger than other cel ls?

4 What is the difference between cel l division and cell specia lisation?

-.."..--======1

Cells

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73

Cell organisation Unicellular organisms such as bacteria and protozoans are made of one cell. Multicellular organisms such as plants, animals and humans are made of many cells. In unicellular organisms one cell carries out all the functions for the cell's survival, such as obtaining food, oxygen and removing waste. In multicellular organisms cells work together -in coordination to carry out these functions.

Levels of organisation The way cells work can be organised into levels from least to most complex, as listed below. cells ~ tissues ~ organs ~ systems ~ organism • Tissues are groups of similar cells with the same basic structure that perform the same function. For example, nerve tissue consists of bundles of nerve cells. • Organs are composed of different types of tissues assembled together to carry out a particular function. For example, the stomach is an organ that consists of muscle, blood and nerve tissue. CELL

TISSUE

ORGANS

• A system consists of a group of organs that work together to carry out a particular function. For example, the stomach is an organ that is part of the digestive system. " • All these systems work together for the survival of the whole organism.

Requirements of cells • Cells need energy, which comes from food and oxygen. The process of obtaining energy from food and oxygen is called respiration. Respiration is the process that keeps all cells alive. The food material that cells need for respiration is a sugar called glucose. Cells are supplied with glucose and oxygen by the circulation of blood. • The waste materials from respiration are carbon dioxide, water and some heat energy. These are removed by the respiratory and excretory systems. Heat and water in the form of sweat are lost from the skin.

SYSTEM

digestive system

red blood cell

.~ skin cell

Figure 5.3.1 The different levels of organisation in the body

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I


skeletal system

ORGANISM

DIGESTIVE SYSTEM

SKELETAL SYSTEM

RESPIRATORY SYSTEM lungs

EXCRETORY SYSTEM

Figure 5.3.2 The body's systems work together

Questions Rank in order of complexity, the ways the cells in our body are organised.

2 What is the difference between a multicellular and unicellular organism?

:3 Name three examples of each of the cell levels listed below. a cells: b tissues: c organs: d systems: 4 Our body is like a sporting team, because diff~rent tissues play different roles. Why is it important that different tissues in our body play different roles? ---=---------~--~~-~---~

I

-

5 Name the composition and function of the following systems in your body. System

Composition

Function

Skeletal system Digestive system Respiratory system

Excretory system

Cells

I

75

Microscopes A microscope is an instrument that magnifies very small objects that cannot be readily studied using the naked eye.

Types of microscopes • Simple microscopes were the first microscopes to be made, using only one magnifying glass (called a lens) in a tube. • Compound microscopes are used in schools. They have two lenses. Each lens is at the end of a tube that can be moved up and down. The lens at the top of the tube, where you put your eye, is called the eyepiece. The lens at the bottom of the tube is called the objective. Compound microscope use glass lenses that focus light ing through an object. These microscopes can magnify objects from about 40 to 1000 times, depending on the lenses you use. • Stereo or dissecting microscopes have a separate set of lenses for each eye, so you can see the object in three dimensions (3D). Light is reflected on the object. These microscopes magnify 4 to 100 times. They are also used to dissect (cut up) small objects. • Transmission electron microscopes (TEMs) use beams of electrons (particles with negative charge) focused by magnets instead of light focused by glass lenses. The electrons form an image that can be photographed or seen on a screen. Electron microscopes can magnify up to 500 000 times. The TEM has played an important role in the study of cell parts.

• Scanning electron microscopes (SEMs) have a lower magnification but produce a three dimensional image, permitting a view of surfaces not possible' with the TEM. Interactions of cells with one another can be studied using the SEM.

Magnification This is how many times larger the object looks, compared with its size in real life. The magnification is determined by multiplying the number on the objective lens by the number on the eyepiece lens. For example at low power: Eyepiece of 1Ox Objective of 4x Magnification is 40x (10 x 4)

As magnification increases, microscopes increase their resolution, or resolving power. Resolution is the amount of detail you can see.

Caring for a microscope • Carry the microscope with two hands: one hand under it and one hand holding it. • Store the microscope in its box or under a dustproof cover. • Do not try to clean the microscope. • Check that the microscope is working and has all its pieces attached.

A

Figure 5.4.1 A compound microscope B dissecting microscope C electron microscope

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I


Questions

6 Do you think the picture below is taken using

What is the difference between compound and dissecting microscope'? Complete the table.

Compound

Di66ecting

micro6cope

micro6cope

a TEM or an SEM'? Give a reason for your choice.

Number of eye pieces Mag nification

Object

Light

Science fact The development of the microscope ·

Type of image

Purpose

2 What is the difference between a compound microscope and an electron microscope'? Which type do you have at school'?

:3 What is meant by the following ,: a

magnification'? ~~=-~;

Assyrians knew the magnifying power of segments of glass spheres thousands of years ago. In the second century AD, Claudius Ptolemy discussed the phenomena of magnification and refraction in relation to lenses and glass spheres filled with water. In the early 1600s, Galileo used a telescope consisting of multiple lenses to observe stars and planets and discovered the rings of Saturn and four moons of Jupiter. He also developed the first simple microscope. Marcello Malpighi, Anton van Leeuwenhoek and Robert Hooke developed the modern compound light microscope . Que6tion: What are some similarities and differences between telescopes and microscopes'?

b resolution'?

4 What does 10x mean on the side of a lens'?

5 If a microscope has two lenses marked 10x and 10x, what is the total magnification'?

Cells

I

77

Using a compound microscope How to use a compound microscope

<;=;;;r--

• Place the microscope on a flat surface. • Check that it has all its pieces attached. • Adjust the mirror so that the light is reflected up into the tube of the microscope.

iit-;1__-

." "..-t-i__-

Caution: do not let direct sunlight strike the mirror. It will damage your eyes if you look at it. • Place the specimen (the object you wish to study) on a microscope slide and cover the specimen with a cover slip (see figure 5.5.2). • Place the microscope slide over the hole on the stage and use the clips to hold the slide in place. • Always start with lowest magnification objective lens. Look at the side of the microscope, and wind the body tube down using the coarse focus knob. Stop just before the objective lens touches the slide. Then look into the microscope and wind upwards until the image comes into focus. • Adjust the image with the fine focus knob. to always focus upwards.

Caution: Do not use 'live' biological samples like blood, saliva or cheek cells, because of the risk of infection by diseases such as hepatitis.


Objective lens

_ _"--Stage

Figure 5.5.1 A compound microscope

Figure 5.5.2 Carefully lower the cover slip

Place a drop of stain against the side of the cover slip. _-==;:2;'-

Draw the stain across the slide with absorbent paper.

Drawing what you see under the microscope

I

Fine focus Nose piece

",r.o..,--

Many parts of a cell are difficult when you see them through the microscope. To make them easier to see, dye or stain is often used. The technique for staining a slide is shown in figure 5.5.3.

78

Body tube Coarse focus

~rL.-L;==.~-

Staining cells

To make a sketch, observe the following tips. • Use a sharp pencil. • Draw clearly defined lines that show the shape of the cell. • Draw only one or two cells. Do not try to draw all that is visible. • Your drawing should be large and label the important features. • Record the name of the specimen, date and magnification beside each drawing.

Eyepiece lens

Figure 5.5.3 How to stain cells

cell ~ membrane

!

cytoplasm

Figure 5.5.4 A drawing of a cell

nucleus

vacuole

Experiment: Preparing microscopic slides Aim : 1 To prepare temporary and permanent microscopic slides of the letter 'e'. 2 To observe parts of stained and unstained onion cells. Materials: Compound light microscope, microscope lamp; 4 slides, 4 cover slips, onion cut into large cubes, methylene blue, water, two pipettes, 2 letters 'e' cut out of newspaper, scissors and glue. Method:

what you see. Your teacher will also show you how these cells look under high power objective. Results: Draw and label the following : Letter 'e'

Unstained onion cell

Stained onion cell

Part 1-Newspaper cuttings 1 Cut the letter 'e' from a newspaper cutting and place the letter right side up onto a slide. Add a drop of water with a pipette. Place a cover sli p on the letter. View the letter 'e' through low power objective.and draw what you see. 2 Place the other letter 'e' on the next sl ide the right way up. Put a drop of clear glue on it and then place the cover slip on top gently. Attach two labels containing your name and date. The second label should contain the description of the slide.


How did the letter 'e' appear when viewed with low power objective of the microscope'?

2 What is the difference between a temporary slide and a permanent slide'?

your name and date

coverslip protects

Temporary slide:

Permanent slide: ,

specimen

descri ption of specimen

3 What was the shape of the onion cell'?

Figure 5.5.5 A permanent slide

Part 2-0nion cells 1 Between the fleshy layers of an onion are some thin transparent layers. These layers are one cell thick. Peel off a layer of this skin and place it on a microscope slide. 2 Add one drop of water and then lower the cover slip so that no air bubbles are trapped . View the slide through low power objective and draw what you see in the results section. 3 Prepare another slide of the onion skin. This time instead of water add a drop of methylene blue stain. View the stained onion cells through low power objective and draw

4 What is the advantage of staining the onion cell'?

Cells

I

79

Looking into cells Animal and plant cells

glucose + oxygen

~ carbon dioxide +

water + energy

All animals and plants are made up of cells. Each cell possesses small parts that carry out different functions. These parts are called cell organelles.

• Vacuoles are sac-like structures that store water, sap or food particles.

Cell organelles

Plant and animal cells: differences

• The cell wall is made of cellulose. It helps to and give shape to the cell. • The cell membrane surrounds and holds the cell contents together. It also controls the substances that enter and leave the cell. Food and oxygen enter the cell and waste products leave the cell. • Protoplasm consists of the nucleus and cytoplasm. • Cytoplasm is a jelly-like substance around the nucleus in which all the cell organelles float. Most of the chemical reactions in the cell occur here. • The nucleus controls cell activities and cell division. • Chloroplasts contain a green pigment called chlorophyll, which traps sunlight for photosynthesis. • Mitochondria produce energy by cellular respiration by combining glucose with oxygen.

A

The difference between plant and animal cells is usually due to their requirements. • Plants make their own food by the process called photosynthesis which is carried out by chloroplasts. water + carbon dioxide

~

oxygen + glucose

• Animal cells do not have chloroplasts because they do not make their own food. They need to take in food constantly. • Plant cells have large vacuoles whereas animal cells have either small vacuoles or no vacuoles. • Plant cells have a cell wall made of cellulose to protect them and give them a rigid shape. Animal cells have no cell walls.

Plant and animal cells: similarities Both possess cell membrane, nucleus, protoplasm, cytoplasm and mitochondria.

Complete the functions of t he cell organel les. Nucleus Cell membrane:

Cell membrane

Nucleus:

Cytoplasm Cell wall: Cytoplasm:

Figure 5.6 .1 Basic structures of animal and plant cells

80

I

Plant cell


Micrographs Micrographs are photographs taken of a microscope image. Figure 5.6.2 is a micrograph of a plant cell. Figure 5.6.3 shows what a micrograph of some human cheek cells would look like. Figure 5.6.2

Questions 1 Why are cells important?

__

4 What are the differences between plant and animal cells? Write in 'present' or 'absent' and the size if relevant.

~"""""'_c=::====:

Organelle

Animal cell

Plant cell

Cell wall

.....;..,----.......,-=j

2 What is a micrograph?

Chloroplast Vacuole

:3 . Complete the table: Cell organelle

5 Complete the table relating to plant and animal cells' requirements-fill in 'yes' if it's needed or 'no' if it is not needed.

Function

Nucleus

Requirement

Plant celie

Animal celie

Light Protoplasm

Oxygen Carbon dioxide Minerals from soil

Cytoplasm

Water Ready-made food 6 For animal celis, which of the products listed go into the cells and which go out? oxygen,

Cell membrane

wastes, glucose, water: carbon dioxide .

I '"

In Cell wall

Chloroplasts ,.

Mitochondria

Vacuole

Out

Cells

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81

Unicellular organisms Unicellular organisms are made up of only one cell. Bacteria and protists are unicellular organisms.

Plasmodium ('plaz-mode-ium') This is a parasitic protist that causes malaria. Mosquitoes act as carriers of these protists and infect people with malaria when they bite them.

Protists Most protists are too small to see without a microscope and are generally found in wet places such as the sea, ponds and damp ground. They can make their own food by using the energy in sunlight, and some eat other living things. Some protists can do both. Each protist cell contains a cell membrane, nucleus surrounded by a nuclear membrane, cytoplasm and some cell organelles.

Amoeba (say 'a-me-ba') An amoeba is a protist that lives in fresh water and does not have a fixed shape. It feeds by engulfing (swallowing) its prey and digests its food in a food vacuole. It reproduces by dividing into two parts by a process called fission.

Euglena ('you-gleen-a') A euglena is a protist that can eat food (like animals do) and can also make food (like plants do). Euglena live in fresh water, salt water and in the soil. When the water dries up, a euglena forms a thick protective wall around itself and lies dormant in the form of a spore until the environment improves. It reproduces by fission like amoeba.

euglena

amoeba

Bacteria Bacteria are very primitive unicellular microscopic organisms. Their cells are one thousand times smaller than protists. Bacterial cells lack many of the internal parts that are found in the cells of protists. They have a cell wall, a cell membrane, and cytoplasm. The nucleus has no membrane. Bacteria divide by fission. One bacterium can divide into two every 20 minutes if conditions are favourable. Bacteria can live in any environment on the Earth. Most bacteria are beneficial to people and help in decomposing waste, digesting food and making cheese and yoghurt. But some bacteria can cause diseases. Food poisoning is caused by bacteria that live in food. Antibiotics are chemicals that destroy bacteria.

Viruses Viruses are even smaller than bacteria. They are not made of cells. Instead they consist of a core of chemicals (DNA, found in the nucleus of cells), surrounded by a protein coat. Viruses can infect all types of living things and cause diseases. They cannot reproduce outside a living cell. They enter a healthy cell and take over the cell nucleus to make new viruses. This process is called replication.

bacteria

vacuole (to collect water and waste)

virus

flagella h"d{

-...L::""'"-J""

mil{ slime capsule cytoplasm chloroplast food vacuole Figure 5.7.1 Unicellular organisms

82

I

Active Science: Skills. & Experiments 1

nuclear area cytoplasm cell membrane

fibres

Experiment: Making hay infusion

Discussion:

Aim: To observe protists from a hay infusion. Materials: Compound light microscope,

1 Where did the animals come from?

microscope lamp, a slide, a cover slip, hay, beaker, water and a pipette. Method: 1 Pour 200 mL water into a beaker. Add some hay into the water and leave it for a week. The spores (or eggs) of protists that are in the hay hatch and come out. An entire community of plants and microscopic animals will be living in the rotting grass. 2 Set up the 'compound microscope on a bench. Place a few drops of. the hay infusion on a slide. Place the cover slip gently on the slide. :3 View the organisms with low power objective and draw what you see. Your teacher will, help you to identify the organisms you are seeing. Ree;u lts: Draw and label the organisms seen under the microscope.

Questions What is a protist? Give two examples of protists.

2 Why was the hay infusion left to rot for a week?

:3 Did the organisms arise by spontaneous generation? Explain.

4 Which organisms could you identify?

Conclusion: Expla in how protists were grown in a

4 Write the differences between protists, bacteria and viruses in the table below.

Structures

Protists

Bacteria

Viruses

Cell wall Cell membrane Nucleus with a membrane Cytoplasm 2 Which protist causes malaria and how is it transmitted?

Made of one cell Can be seen with light microscope

:3 Describe the structure of a bacterial cell.

r-

How they reproduce

v f:l'

Cells

I

83

Cancer Cancer is a group of diseases that result from uncontrolled cell division. Every cell has a nucleus, which contains chromosomes. Humans have 46 chromosomes. Each chromosome contains genes. Genes control individual characteristics of the organism. Sometimes genes are damaged or altered. These genes cause cancer and are called oncogenes. The damage can be caused by radiation, viruses, or chemicals. Cancer-causing chemicals are called carcinogens.

• poor diet-not eating enough cereals or vegetables, and eating too much fat can increase the risk of bowel cancer. • alcohol-excessive consumption of alcohol can cause cancer of mouth, throat and stomach. • asbestos-when fibres of asbestos are breathed into lungs, they can cause lung cancer and other diseases. • chemicals-many chemicals such as coal tars, some solvents and dyes attack the genes in cells and can cause cancer. • radiation-radiation from radioactive materials, the atmosphere, and medical procedures such as X-rays cause cancers. • gender and age-ovarian and breast cancer are more common in women who have babies at an older age, and who do not breast feed. Prostate cancer generally occurs in men who are over 65 years old.

Tumours When genes are damaged cell division gets out of control and too many cells grow. This growth is called a tumour. There are two types of tumours: • benign tumours do not spread to other tissue. They are not normally fatal (causing death) unless they grow in a vital organ such as the brain. • malignant tumours grow into surrounding tissue and can be fatal if their growth is not stopped. They can split off and spread throughout the body, causing secondary cancers.

Warning signs of cancer • A bad persistent cough or hoarseness. • A change in bowel habits or bleeding from the anus. • A sore that does not heal. • A mole or wart that changes. • Unusual bleeding or discharge. • A lump in the breast, neck, armpit or testicles. Unexplained weight loss. Indigestion or difficulty in swallowing. If someone experiences any of these, it doesn't necessarily mean they have cancer, but they should see a doctor about it.

Risk factors Many things that affect us can increase the chances of contracting cancer. These are called risk factors. They include: • sunlight-the ultraviolet light in sunlight causes skin cancer (melanoma). • smoking-tobacco tar contains 17 known carcinogens. Cancers can form in the lungs, throat, nose, bladder and pancreas.

Primary tumour

chemicals~ Cell with damaged cell division genes Viruses

~

1 - --

=c;::::>

"diatiO'

Chromosomes and genes Nucleus

Figure 5.8.1 How tumours form

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8- -

.....


r--..----."'-J'- J

--

Secondary tumour

\ Al
Questions

b Rank the 4 cancers in order of incidence for males and females.

What is cancer'?

Males:

2 Match the meaning of these words by' placing the relevant n.umber against the letter Worde;

Meaning 1 Chemicals that cause cancer B Risk factor 2 Uncontrolled cell growth C Oncogene :3 Things that can increase the chance of getting cancer D Carcinogen 4 Gene that causes cancer

Ane;wer

Females: 5 This graph shows the risk of contracting lung cancer. 25

A Tumour

Risk of contracting lung cancer 22.2

20

D ~Xale •

Female

5

-

:3 What is the difference between a malignant

o......_-.c=::l-.I.Non-smoker

and a benign tumour'?

Current smoker Fonner smoker (stopped smoking (heavy smoker, has smoked for 10 years ago) over 20 years)

a Which group of people have the greatest risk of contracting lung cancer'?

4 The table below shows the number of new cases of the four most common cancers contracted in Victoria in 1999. Type of cancer

Malee;

Femalee;

Prostate

2684

-

Breast

-

2795

Lung

1299

701

Melanoma (skin)

874

778 .

Bowel

1593

1444

b Overall, do males or females have the higher risk of contracting lung cancer'? Why might that be'?

d What is the chance of the following groups of males contracting cancer'? .i

ii

~

Current smoker: _

""'"",,,,,

j

Former smoker:

e Do you think there is a good reason for heavy smokers to quit smoking'?

a Draw a column graph of the data shown in the table. 6 Australia has the highest incidence of melanoma or skin cancer. What should you do to prevent the risk of contracting melanoma'?

Cells

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85


:3 Match words with phrases by placing the

State whether each of the following statements is true or false. a Plant and animal cells are the same as each other. b There are different types animal cells. c All living things are made of cells. d Nothing i.s smaller than a cell.

relevant number against the letter. Word

Phrae;e

A Carcinogen 1 What you prepare and look at under microscope

0/

B Dissecting

2 A group of organs

microscope

that work together

C Fission

:3 Microscope with two objectives and that

e Electron microscopes have greater magnification than light microscopes. f A group of like cells is called a tissue. g Only animal cells have a cell wall. h Vacuoles store water and dissolved food in cells. A cell wall gives shape and in plant cells. j Cancer is when cell division gets out of control. k Chloroplasts help animal cells to Qbtain energy. A group of similar tissues form an organ. 2 What are the functions of the following organelles?

produces 3D images D Cell

added to specimens to make cells easier to see E Micrograph 5 Organelle that controls the activities of the cell F Multicellular 6 A chemical that causes a tumour to grow G Nucleus

H Organelle

Nucleus

8 The thin layer which surrounds the animal cell

I Protoplasm

9 Small parts floating in cytoplasm

Chloroplast Cell membrane

7 Organism which is made of many cells

Cell organelles Functions

Cell wall

4 A coloured solution

J Stain or

10 Splitting into two

dye

parts

K System

11 Photograph taken with a microscope

L SpeCimen

12 The nucleus and the cytoplasm within a cell

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Answer

4 The following diagram shows a piece of human hair. Some human cells are superimposed on it. The scale across the top is in micrometres, which are written as f.lm . One micrometre is one millionth of a metre.

o

micrometres ().lm) 10 20 30 40 50 60 70 80 90100110

Thinking questions Bacteria reproduce mainly by dividing into

two. With good conditions, such as warmth, water and food, they can divide every 20 minutes. If you start with one bacterium, hollt many will you have after a 20 minutes:

i

=

b 40 minutes: 22 =

c 1hour: 2 3 = d 3 hours: 2 9 = 2 Why hasn't the Earth been over-run with bacteria?

Human egg cell (ovum) with nucleus

Extension activity: A model cell

What are the widths of the following? a

human hair

b nucleus of egg cell

c human egg cell d

human sperm

e white blood cell f

red blood cel l

!3 cheek cell

Research questions Research the skin cancer known as melanoma. Find out the cause, prevention and treatment for it. A good web site is: http://www.melanoma.com 2 Research how a lifestyle with the right food can reduce the chances of getting bowel cancer. Present your information in a poster form.

Make a three-dimensional model of a plant cell. You can use the following ingredients: • Cell-a clear bottle or a plastic ice-cream container • Cytoplasm- colourless jelly • Nucleus-white table tennis ball • Vacuole-very small yellow balloon filled with water • Chloroplasts- green pasta tubes • Mitochondria-dried beans Draw and label a diagram or your model in your notebook.

Word Check Write the meanings of these words in your notebook. Microbes Organs Cancer Mitochondria Photosynthesis Carcinogen Multicellular Protoplasm Cells Cell theory organisms Respiration Tissues Cell wall Nucleus Unicellular Chloroplasts Oncogenes Organelles organisms Cytoplasm Vacuoles Membrane Organism

Mind map Draw a mind map of the important ideas in this chapter in your notebook.

Cells

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87

~6nGLA~)SlflCA1~/ON OF LIVING

THINGS

living things Living things come in many shapes and sizes. All living things such as plants, animals, bacteria and other microbes (microscopic things) are known as organisms. An organism is anything capable of carrying on life processess. Scientists have identified more than two million kinds of organisms on our planet.

Features of living things • Are made of cells. Can be unicellular or multicellular. • Need nutrients to get energy and to survive. Animals eat food, while plants make their own food from water and carbon dioxide in the presence of sunlight. • Respire to obtain energy, by taking in oxygen and giving out carbon dioxide. • Dispose of wastes produced during cellular activities. • Respond to changes around them. • Animals move to obtain food, to escape predators and to find mates. Plants can move by growing towards the light. • Reproduce their own kind asexually (without a partner) and/or sexually. • Grow by cell division.

Non-living things There are some non-living things that can carry out certain activities of living things: • Robots respond and use energy, but they cannot grow and reproduce. • Crystals growing in solutions use chemicals to grow, but are not living. • Fire needs oxygen and produces carbon dioxide. It can grow bigger and reproduces by sparks. Yet it is not a living thing.

Dead objects Leather, fur, wool, wooden furniture, preserved animals and plants can be classified as dead objects because they come from dead plants and animals.

Are viruses living or non-living? • Viruses are not made of cells. Instead, they consist of the chemicals found in the nucleus of cells (nucleic acid). They display characteristics of living things only when they enter a living cell (host cell) where they reproduce by replication (making copies of themselves). • When a virus is outside a living cell it displays characteristics of non -living things, becoming crystallised (like chemical compounds) and remaining inert (not reacting to things).

Question: Fill in the spaces below with examples.

Objects Living (cellular)

Non-cellular .

Figure 6.1.1 Living, dead and non-living objects

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Non-living

I' Dead

Complete the following What features do living things have that means they are alive'? •

to get energy and to survive.

Need

•

by taking in oxygen and giving out

•

Dispose of

•

Anima ls by

dioxide .

produced during cellular activities.

......- ; ' - - - -

to obtain food, to escape predators and to find mates. Plants can move towards the light.

Reproduce the ir own kind asexually or

• •

into adu lt plants and animals by cell

•

to changes around them .

Questions

:3 How would you classify a virus'?

What is an organism'? Give three examples.

2 Write the differences between living and nonliving things in the table Characteri5tic Living thing5

Structure

Need food

4

A fire has some features of a living thin0. List three features.

Non-living thing5

5 Place ticks in the table to identify the following as living, non-living and dead objects. Object5

Living

Non-living

Dead

Bacteria Wooden objects Respire

Fern Sheep Wool

Excrete

Plastic objects Rocks and

Respond

minerals Leather Pressed

Grow and

plants

reproduce

Preserved insects

Classification of Living Things

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89

Sorting into groups How a domestic cat and human are classified

Biologists have sorted living things into groups. Sorting into groups is called classifying. Each group has been given a name, which tells us something about the group. It is useful to have organisms classified into named groups because it makes it easy for everyone in the world to identify unknown things, and to determine their uses and whether they are harmful to us.

Features used in classification Features such as colour, size and where the organism lives are not very important in classifying. The following features are used to classify animals: • type of cells • type of body covering • type of skeleton • method of reproduction • movement.

.... Phylum ....

....

Class

human

Kingdom

Animalia

Animalia

Phylum

Chordata

Chordata

Sub-phylum

Vertebrata

Vertebrata

Class

Mammalia

Mammalia

Order

Carnivora

Primate

Family

Felidae

Homonidae

Genus

Felis

Homo

Species

cattus

sapiens

Every living thing is given its own two-word name. This is called its binomial name or scientific name, which is in Latin. The first word is the name of the bigger group called genus. A genus is a group of closely related species. The genus name starts with a capital letter. The second word is the species name and it does not have a capital letter. The binomial name for the household cat is Felis cattus, and a dog is Canis jamiliaris, and a human is Homo sapiens. Notice the binomial name is always written in italics (sl@ping letters). Domestic cats belong to one species because they can interbreed. Within the domestic cats there are many types, called breeds, such as Burmese, Siamese, Manx and Chinchilla.

All living things are classified into five kingdoms: Monera, Protista, Fungi, Plants and Animals. Each of these kingdoms is subdivided into smaller and smaller groups called phylum, subphylum, class, order, family, genus and species. A species is the smallest group of organisms that look similar to each other and can interbreed to produce fertile offspring (i.e. offspring that can reproduce). Domestic cats belong to one species because they can interbreed and have kittens. When a tiger and lion interbreed a hybrid animal called a liger or a tigon is produced. Hybrid animals are infertile and cannot reproduce.

Kingdom

domestic cat

Binomial names

Levels of classification

Subphylum

Classification level

....

Order

....

Family

....

,

Genus

+-

Species

Fewer characteristics - - - - - - - - - - - - - - - - - - - -... More characteristics in common in common Figure 6.2.1 Levels of classification

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Activity: Make your own classification system . Aim: To classify the insects according to their external structures. Materials: A photocopy of the insect diagrams (your teacher will provide this) and scissors. Met hod: 1 Cut out the insect pictures and place them into groups based on some aspect of their appearance such as the presence or absence of wings, the number of wi~gs, shape of body, etc. Write a reason for your classification. 2 Then with a friend and compare your classifications. Can you think of other types of classification'? :3 Then with another pair to make a group of four, and compare your classifications again. One member of your group can report to the class. Results: Draw a flow chart on a piece of paper to show your group's classification system.

2 Can you identify an unknown insect using your classification'?

Conclusion: Which characteristics were used by

your class to classify the insects'?

Discussion: 1 Is one type of classification of insects better

than the other'? Explain.

Questions What is classifying'?

4 What is the difference between a species and a hybrid'?

I

2 What is meant by 'binomial name',?

, 5 What is t he relationship between a breed and

:3 What are the binomial names of: a

cat?

"

dog'?

c

human?

species in dogs'?

~----------------~

Science fact Taxonomy The science of classification is called taxonomy. Biologists classify organisms in categories called taxa (singular: taxon) . In the 18th century Carolus Linnaeus developed a classification system based on structural features . He introduced the two-part system called binomial nomenclature that is still used today.


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91

Using keys A key is a chart or table that allows us to identify and name living things. You could use a key to find the name of a strange plant or animal you had never seen before.

Learning about keys A school's mixed hockey team is shown in the picture below (figure 6.3.1). The key below that (figure 6.3.2) lets you identify each of the team . Mari, for example, is the girl with her hair tied in pony tails and wearing a short sleeved blouse. Can you identify the other team using the key?

Using a key Key to the hockey team 1 Boy player: go to step 2 Girl player: go to step 5

2 Short sleeve shirt: go to step 3 Long sleeves rolled up: go to step 4 3 Dark hair = Con Blond hair = Heinar 4 Black shoes = Hans Striped joggers = Leslie 5 Hair tied in pony tails: go to step 6 Hair not tied: go to step 7 6 Long sleeves = Kim Short sleeves = Mari 7 Wears glasses = Sze- Li No glasses = Suzie. This key only works for these students. If the team changes, the key must change as well. Look at the four new team in figure 6.3.3: Yan, Andrew, Nastassia and Matt. Using the key, both girls appear to be named Suzi and both boys are named Hans. A larger, newer key is needed to include these four .

Mari Figure 6.3.1 The hockey team-can you identify the other team ?

Kim

Mari

Sze-li

Figure 6.3.2 Key to mixed hockey team

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Suzie

Con

Heinar

Hans

leslie

Nikos Van

Andrew

Nastassia

Matt

Figure 6.3.3 Some new players

Activity: Make your own key

Stacey

ROChelle

John

Figure 6.3.4 More new players

Discussion:

Aim: To make a new key to identify the 16

How was your key different from the previous

players in the new, larger hockey team. Materials: Paper, pen and pictures of hockey players (figures 6.3.1, 6.3.3 and 6.3.4) . Method: 1 Look at figures 6.3.1, 6 .3 .3 and 6 .3 .4 and , determine some good features to include in your key for identifying all 16 hockey p.[ayers. 2 Use special or distinctive features~height differences or the difference between having dark blonde hair or light brown hair cou ld be confusing to other people using your key. 3 Use features that everyone agrees onsleeve length, ribbons in hair, type of shoes, glasses or no glasses, jumper or no jumper, and so on. 4 Compare your key with other of the class. Results: Write your key for the new hockey team in your notebook and show it to your teacher.

one with only 8 players'?

2 [s it possible to identify al [ the 16 players using the new key'? Conclusion:

What is the advantage of using keys in identifying of a hockey team'?

2 Which features did you use to .make your own key of hockey p[ay@rs'?

Questions 1 What is a key'?

2 Do you th ink it is a good idea to use keys to identify plants and animals'? Discuss.

3 Draw a key in your notebook showing items of laboratory equipment. Include these items of equipment: tripod stand, Bunsen burner, gauze mat, 50 mL beaker, 150 mL beaker, 100 mL measuring cylinder, 500 mL beaker, 500 mL measuring cylinder, retort stand, clamp and boss head.


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93

Kingdoms of living things Kingdoms are the largest groups of living things. All the living things on Earth are classified into five kingdoms. The classification is made based on the type of cell, and how the organisms obtain their food.

• Animals are multicellular heterotrophs and cannot make their own food. They feed on other animals and plants. They have advanced cell structure. They can reproduce asexually or sexually. e.g. vertebrates and invertebrates.

The five kindoms

Some unusual organisms

• Monera includes all the bacteria and cyanobacteria (also known as blue-green algae) that have chloroplasts. Their cells are very simple and they are microscopic in size. They have no membrane-bound nucleus. They reproduce by fission (dividing into two). • Protista are microscopic unicellular organisms. Their cells are more advanced and have more cell organelles. They live in stagnant water and damp places. A few of them cause diseases. They reproduce by fission. e.g. amoeba and plasmodium. • Fungi are multicellular plant-like organisms that do not make their own food because they lack chloroplasts. They are saprophytes (feed on dead things) and have an important role in recycling. They reproduce by forming spores. e.g. mushrooms. • Plants are autotrophs (make their own food) because they have chloroplasts in their leaves. Their cells are more advanced and contain many cell organelles. They reproduce asexually and sexually. e.g. ferns, mosses, roses, rice and grass.

Some organisms do not fit into one kingdom because they have characteristics of many groups. Biologists select the most important features and place the organism into the kingdom with those features. • A euglena ('you-gleen-ah') is a microscopic organism that can make its own food like a plant and eat food like an animal. It moves by using a flagellum (a whip-like structure). It fits into three kingdoms-plant, animal and protist. Since it is microscopic, biologists consider it to be a protist. • A lichen ('lie-ken') is two organisms living together. A lichen is an alga (a simple plant) growing with a fungus. They rely on each other. The alga makes the food and the fungus provides a place to live and some nutrients. Is lichen a plant, a fungus, or both?

Figure 6.4.2 Lichen

Living things

•

Monera kingdom Unicellular Chlorophyll in some Cell wall No nucleus e.g. bacteria

~ ~oD 0

•

Protista kingdom Unicellular Chloroplasts in some Cell wall in some Nucleus e.g. amoeba

~ ' . . ' .0 .·.· . ·0 ,"

•

Figure 6.4.1 Classification of living things

94

I


·0·. ',

~

Fungi kingdom Uni or multicellular No chloroplasts Cell wall Nucleus e.g. mushrooms

g

•

Plant kingdom Multicellular Chloroplasts Cell wall Nucleus e.g. flowering and non-flowering plants

+

Animal kingdom Multicellular No chloroplasts No cell wall Nucleus e.g. vertebrates invertebrates

• A slime mould is an unusual fungus-like organism. It can move around like a protista. It feeds on dead things like a fungus. Its cells are merged together and not separated as in fungi. It can fit into the fungi kingdom or the protista kingdom.

Figure 6.4.2 Slime moulds

Questions A green spider is classified as an animal, even though it is green like all plants. Why is a spider classified as an animal?

2 Bracket fungi grow on dead tree trunks. How do these fungi obtain their food?

6 Why is lichen difficult to classify?

7 If explorers from Earth ever visit distant planets where there is no light, is it likely that they will find green plants like on Earth? Explain.

:3 Some seaweed is brown. When you put it in hot water, the brown colour dissolves into the water and the seaweed becomes bright green. Which kingdom does brown seaweed belong to, and why? 8 Is it true that plants are solar-powered? What about animals and humans? Are they solar-powered as well? 4

Monera and protista are both microscopic. ' Why are they placed in different kingdoms? _

5 Biologists claSSify an alga as a plant, even though it is microscopic like a protist. Why is an alga considered to be a plant?

Research questions 1 Find out what cyanobacteria are and why they are placed in the monera kingdom. 2 Why are jellyfish placed in the animal kingdom?


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The plant kingdom Plants with conducting vessels

Plants are living organisms called autotrophs because they can make their own food. They contain a green chemical called chlorophyll. This enables them to use solar energy to make their food by a process called photosynthesis. Some plants have conducting vessels (special vessels to transport water and nutrients) and some don't. The plant kingdom is divided into different groups called divisions.

• Gymnosperms ('jim-no-sperms') are large trees and shrubs, reproduce by seeds in cones. e.g. pine trees (conifers). • Angiosperms ('anjee-o-sperms') vary from small to very large trees, reproduce by flowers, which produce fruits and seeds. e.g. all flowering plants, including grass, cacti, lillies, eucalypts.

Divisions of the plant kingdom

The importance of plants Plants are essential for our survival. They provide us with • food and oil • oxygen for respiration • fibres for making clothes and ropes • medicinal compounds • timber for fuel, furniture, paper and buildings • recreational faclities for relaxation and sport (e.g. parks and forests).

Plants with no conducting vessels • Algae (' al- gee') are usually small (but some are large), grow in water, have no roots, no stems, no leaves. e.g. seaweed, kelp, green slime. • Bryophytes ('bri-o-fites') grow on moist land, 1 mm to 30 em tall, flat leaves, no roots, simple stems, reproduce by spores in capsules. e.g. moss, liverwort, hornwort. • Ferns are medium-size plants, have stems, roots, leaves, reproduce by spores on the back of leaves. e.g. fishbone fern, bird's nest fern.

Plants 1

1

I

'I

I

No conducting vessels

t

+ Algae e.g. seaweed

Have conducting vessels

Bryophytes e.g. moss

1

1

1

Ferns e.g. bird's nest fern

•

Gymnosperms e.g. conifers, pines

I

•

Angiosperms e.g. grasses, roses, lillies

Figure 6.5.1 How plants are classified

Science fact Earth's oldest tree Methuselah (bristle cone pine) is the oldest known living tree in the world. It has been estimated to be over 4700 years old. It was a tiny seedling when the Egyptian pyramids were being built. It grows at an elevation of 3048 metres in the White Mountains in California. It has adapted to harsh living conditions,and as a result has been able to survive over thousands of years.

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I


Experiment: Classification of plants Aim: To classify plants into five major divisions by using their external characteristics. Materials: Seaweed, moss, liverwort, fern plant and a leaf with spores, pine cones and leaves, geranium with roots, grass with roots. Method: 1 Observe the plant specimens and note whether they have the following structures: stem, leaves, roots, spores, seeds, cones, flowers. 2 Complete the results table and identify the division to which the plants you observed belong. Refer to your textbook if you have difficulty or ask for your teacher's help. Results:

Cha racterietice

Stem

Roote

Lea vee

Sporee

Seede

Divieion of plant kingdom

Flowere Conee

Seaweed Moss Liverwort Fern Pine Geranium Grass Discussion:

Did you have any difficulty in classifying the plant specimens? Explain why.

2 What differences did you find between angiosperm and gymnosperm?

Conclusion: List the characteristics used in classifying the plants.

Questions Fill in the table to show the differences between the five major divisions of plants.

Characterietice Algae Bryophytee

Ferne

Gymnoeperme

Angioeperme

Stem

Roots Leaves Flowers Seeds Cones Spores 2 List some plants or parts of plants that provide food and/or oil.

---Classification of Living Things

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97

The animal kingdom The classification of animals The animal kingdom is classified into groups called phylum (plural: phyla). Animals with no backbone are called invertebrates and those that possess backbones are called vertebrates or chordates.

ANIMAL KINGDOM Vertebrates (backbone)

Ectothermic (changing body temperature)

Invertebrates (no backbone)

Endothermic (constant body temperature)

Arthropods • Body segmented • Many ted limbs • External skeleton Molluscs e.g. crab, flies • Soft bodied Amphibians Fish Mammals Reptiles Birds • Often covered • Scaly skin • Moist skin • Scaly skin • Lungs • Lungs with a shell • Lay eggs in • Most lay • Lay eggs • Feathers • Suckle eggs in and wings young with water • Head with • Most have eyes and/or 4 legs water, some • Eggs with milk from • Most have tentacles mammary e.g. lizards, 4 legs give birth to brittle shell e.g : snail e.g. frogs live fish e.g. duck glands snakes • Have fins Echinoderms e.g. goldfish • Hard spiny skin • 5 to 10 arms, sucker feet Marsupials Monotremes Placentals e.g. starfish • Give birth to • Lay eggs • Young are with underdevborn fully leathery eloped young developed that grow in Shells • Placenta a pouch provides • Young lick milk from attached to nourishment mother's fur the mother's and oxygen e.g. platypus nipples e.g. human e.g. kangaroo Figure 6.6.1 Classification of animals '------'

Worms • Smooth tube-like body with or without segments e.g. earthworm Poriferans • Body perforated by small pores • Usually fixed in 1 spot e.g. sponge Cnidarians • Hollow body with ' 1 opening (mouth) • Tentacles with stinging cells e.g. jellyfish, coral

t

Science fact Giants The blue whale is the largest living organism in the world. To date, the largest whale measured weighed 110 tonnes and was over 27 metres long. African elephants are the largest land animals. They weigh about 13.5 tonnes and can be approximately 6 metres long.

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Experiment: Classification of animals Aim: To classify animals into different phyla by using their externa l characteristics. Materials: Preserved or live specimens of sponge, jellyfish, earthworm, starfish, crab, snail, fish, bird and frog. Method: 1 Observe the following externa l characteristics of the specimens: body type, body covering, number of legs, shell, ske l eton~ tentacles, arms, wings and fins. 2 Identify the phylum to which they belong by referring to the information on the previous page. Results:

Sponge

Jel/y-

Earth-

Star-

fish

worm

fish

Crab

Snail

Fish

Bird

Frog

Body type Body covering Number of legs Shell Skeleton Backbone Tentacles Arms Wings Fins Phylum or group

Discussion:

What is the difference between invertebrates and vertebrates?

2 Which specimens were invertebrates and which were vertebrates'?

:3 What are the differences between a fish, frog and a bird? Fish: Frog : Bird: Conclusion: Which characteristics helped you to classify the animals into their phyla?


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99

Vertebrates Vertebrates are groups of animals that have a backbone, which is made of series of bones called vertebrae. Each vertebra is like a hollow bone that protects the spinal cord. Vertebrates are divided into five groups (classes).

Classification of vertebrates Fish Fish have the following characteristics: • streamlined body • body covered with scales .• usually swim using fins • breathe with gills • some lay eggs and others give birth to live young • are poikilothermic-have variable body temperature • live in water. There are two subgroups of fish. 1 Cartilaginous fish have a skeleton of soft bone called cartilage. e.g. sharks and rays. 2 Bony fish have a skeleton of bone. e.g. tuna, whiting, salmon.

Amphibians Include frogs, salamanders and toads. They have the following characteristics: • moist skin • 2 pairs of appendages with webbed feet, which help them to swim in water and hop on land • lay their eggs in water-the eggs hatch into tadpoles (larvae), which swim with tails and breathe with gills. Adults usually breathe with lungs on land and with skin in water • poikilothermic • live in water and land.

Reptiles Lizards, crocodiles, snakes, geckos and tortoises are reptiles. The extinct dinosaurs were also reptiles. Characteristics of reptiles: • tough, dry, scaly skin

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• most have 2 pairs of appendages (arms, legs or wings), except snakes and some lizards • breathe with lungs • lay eggs with tough, leathery shells • poikilothermic • live on land or water or both.

Birds Birds have the following characteristics: • have feathers • 2 pairs of appendages with 1 pair modified into wings, the other pair are legs • most fly but some are flightless • breathe with lungs • lay eggs that have a brittle and limy shell • homeothermic-have constant body temperature (high) • live on land and/or partially in water.

Mammals Mammals possess the following characteristics: • skin covered with hair or fur • usually have 2 pairs of appendages-armsllegs • breathe air with lungs • give birth to live young • females have mammary glands that secrete milk • have a well-developed brain • homeothermic • live on land and water There are three subgroups of mammals. 1 Monotremes lay eggs with leathery shells, the young lick milk oozing from milk patches. e.g. platypuses and echidnas. 2 Marsupials possess pouches, in which the immature young develop by attaching themselves to nipples in the pouches. e.g. koala, kangaroos, possums, wombats. 3 Placentals have a uterus where the young develop. Placenta transfers nourishment and oxygen from the mother to the foetus and removes wastes. Well-developed young are born after a long periods of gestation (= period of development). e.g. whales, dolphins, bats, rats and humans.

Experiment: Classification of vertebrates Aim: To classify the given specimens into different groups using external characteristics. Materials: Preserved specimens or photographs of: shark, bony fish, frog, snake, bird, echidna, kangaroo and monkey. Method: Observe the external characteristics and classify the vertebrates into their groups. Resu lts: Complete the table and classify the specimens. Shark

Bony fish Frog

Snake

Bird

Echidna

Kangaroo Monkey

Body covering Fins Wings Appendages (legs, arms) Mammary glands Pouch Group Subgroup


Which external characteristics helped you to classify vertebrates into their five groups?

2 Which characteristics helped you to identify the subgroups of mammals?

Questions What is the difference between a vertebra and vertebrate'?

2 Complete the table: Group

Body covering regulation

Temperature

Reproduction

Examples

Fish Amphibians Reptiles Birds Mammals

.Classification of Living Things

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101

Invertebrates Invertebrates are groups of animals that have no backbone and are divided into many subgroups as shown below. Approximately 90% of all animals are invertebrates.

PORIFERANS - colonies of animals living together. e.g. sponges 'por-if-er-an ' CNIDARIANS - water-living, have tentacles and one body opening. 'nee-dare-ians' e.g. coral, anemone, jellyfish PLATYHELMINTHS - flat worms. e.g. planarian in-th' liverfluke worm-like animals (three phyla)

NEMATODES - smooth tube-like body. Can be free-livin 'nem-a-toad' . or parasites. e.g. roundworm ~;'.J.::~ ANNELIDS - body in segments. e.g. 'an-a-lid ' beech worms

ECHINODERMS - hard spiky skin, with 5 to 1aarms, sucker feet. 'e-kino-derms' e.g. starfish, sea urchin, brittle stars

INSECTS - six legs, three body parts. Over 1000000 species. e.g. beetles, ants, flies, bugs

INVERTEBRATE

ARTHROPODS earth-raw-pods'

ARACHNIDS - eight legs, two body parts. Live 'a-rack-nid' on land. e.g. spiders, ticks, CRUSTACEANS - ten or more legs, most live on 'crust-aish -un' land. e.g. prawns, lobster, crab MYRIAPODS - lots of legs on worm-like 'mear-e ah pod' e.g. centipede, millipede

CHITONS - flat animals, covering of ~ch-eye -ton ' eight shells. e.g. chiton

MOLLUSCS 'mol-usk'

GASTROPODS - soft body with coiled shell. 'gast-ra-pod' e.g. snail, slug, cone BIVALVES - soft body between two shells. 'be-valve' e.g. oyster, mussel CEPHALOPODS - shell inside soft body. Live in sea. .., 'kefa-Io-pods' Intelligent. e.g. octopus, squid ~~1Io:; ""~"" '

Figure 6.B.1 Classification of invertebrates

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The study of an invertebrate The house fly belongs to phylum arthropoda and class insecta. Its binomial name is Musca

domestica.

Characteristics of a fly • Body is divided into three parts: head, thorax and abdomen. • Has 6 legs. Combs on feet are used to clean and groom. • Has 2 leathery wings, 2nd pair is reduced stumps which act as stabilisers. • Has external skeleton called exoskeleton. • No mouth and teeth. • Has a proboscis-a hollow tube-like structure to suck in food. • Has simple brain and the spinal cord runs on the lower part of the body. • Has tiny holes on either side of the body through which it breathes.

Wings Reduced wings Muscles controlling wings Heart Three smaller eyes Brain Compound eyes Antennae Salivary gland

• Reproductive organs are in the abdomen and eggs develop inside the body. • Has a simple heart. Blood is not contained in arteries and veins. • Has two large complex eyes and has three smaller eyes on top of the head. • Has antennae sensitive to vibrations in air. • Has no ears. • Cannot detect heat and cannot regulate its temperature (cold-blooded). • Has simple kidney to excrete waste. • Has stomach and intestine to digest food. • Has complex life cycle. Flies reproduce every week and lay 100 eggs at a time. egg

~

larva

~

pupa

~

adult fly

• The larvae are known as maggots, which eat rotting food and grow. They develop a cocoon around them and become pupae. This type of change in a life cycle is called metamorphosis.

Tiny holes Air tubes Ovary Kidney Anus

Stomach and intestine Exoskeleton Combs on feet

Proboscis End of proboscis

Nerves Pads on feet

Muscles controlling legs

Figure 6.B.2 The parts of a fly


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Questions Here is the binomial name of the fly: musca domest ica. But it is written Incorrectly. a

What is wrong with the way the name is

written?

b

What is the genus name and species name

of the fly?

Genus name: Species name:

, 2 What is meant by metamorphosis'?

4

Describe the life cycle of the fly and complete t he labels in figure 6 .8 .3 (right) by filli ng in the name of the life cycle stage: The life cycle of the f ly:

Figure 6.8.3 Life cycle of the fly

5 Complet e the table to show differences between a house f ly and a human: Featuree

Houeefly

Size Location of skeleton

Senses present Breathing Movement

Type of brain Type of heart Arteries and veins Reproduction What they eat Kidney Backbone Phylum, class

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Human

Review and research Review questions Use the chart t o class ify the arthropods drawn below into their subgroups. Label the diagrams wit h their classification.

2 Below is a key for the identification of insects and spiders that live in trees. Use the key to name the animals shown. INSECTS, SPIDERS which live in trees

CLASSIFICATION OF ARTHROPODS 3 pairs of legs, body has

Insects

3 parts 4 pairs of legs, body has

4

I

body in 2 parts

Arachnids

.----.L.----,

~

2 parts

5-8 pairs of legs, with other

Crustaceans

I

smaller limbs Many pairs of legs, long thin body

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pair~ of legs

.1

3 pairs of legs

I I

body in one part I legs longer than body

harve~tman

.

I legs shorter Uian body

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body striped

Myriapods

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back end of body pOinted

I W~SP I

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body not striped

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back end of body not pOinted ~

body round and spotted

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body long and not spotted

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r.-Ila--; dy-'-b c-:ird-:ll

~ wings narrow

wings wide

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I cranefly I

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feelers thicker at ends

feelers same thickness

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I butterfly I

5

.~

~ 6 :'

7 ~ 8~

12

9


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:3 These are the binomial names of some organisms. Pita incisa, Pita regia and Incisa regia . a

Which (if any) are in the same genus?

b

Wh ich (if any) are in the same species?

4 The drawing shows three animals that look similar. They are classified into three different -groups.

The shark belongs to the fish group, the ichthyosaur ('ick-thee-o-saw') to the reptile group, and the dolphin to the mammal group. Why are they classified into different groups?

Research questions Research one of the following living things and with the help of a diagram describe its structure, its way of life and type of reprod uction . • giant squid • sea horse • bristle cone pine • platypus • gastric brooding frog • hydra 2 There have been many famous people in the study of biology. Select one of the following and present a story of that person in a poster. • Carolus Linnaeus • Jane Goodall • Henry Walter Bates • Konrad Lorenz :3 What are the fo llowing, and where do they come from? Look up Internet sites and reference books. • ambergris • penicillin • spermaceti • atropine • citronella 4 What is unusual or useful about these plants and animals? • aloe vera • jojoba • Venus fly trap • sundew • pitcher plant • chameleon • mimosa • puffer fish

Mind map Draw a mind map of the classification system described in this chapter in your notebook.

Word check Write the meanings of the following words in your notebook. Algae Annelids Angiosperms Arachnids Backbone Binomial name

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Birds Bryophytes Chordates Classifying Crustaceans Echinoderm


Exoskeleton Fungi Fish Gastropods Genus Gymnosperms

Hybrid Insects Invertebrates Key Kingdom Lichen

Mammals Marsupials Metamorphosis Molluscs Monera Monotremes

Myriapods Nematodes Phylum Placentals Protista Reptiles

Crossword puzzle 1

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4

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10

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Across

Have shells and smooth bodies (8) 2 A worm that lives in the soil (9) 4 A large group in classification (7) 5 Animals with ted feet like crabs (10) 7 Dinosaurs and snakes belong to this group (8) 8 Animal that has scales and lives in water (4) 10 Bacteria belong to this kingdom (6) 12 Dividing into groups (14) 16 Animals that have pouches (10) 17 Animals that have mammary glands (7) 18 Non-flowering plants (11) 19 Amoeba belongs to this kingdom (8) 21 Flies belong to this group (7) 22 Animals with feathers (5)

Down 1 Changes in the life cycle of an insect (13) 3 Mushrooms belong to this kingdom (5) 6 A group consisting of many species (5) 9 A mammal that has a placenta that nourishes the developing foetus (9) 10 A mammal that lays eggs (9) 11 A scientist who studies living things (9) 12 Animals with backbones (9) 13 Flowering plants (11) 14 A simple plant (5) 15 Animals without backbones (13) 20 An example of an amphibian (10)


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CHAPTER 7: FORCES - PUSHES AND PULLS

Why objects move Nothing moves by itself. It must be pushed or pulled. A push or a pull that makes something move is called a force. There are two types of forcespush forces and pull forces. Forces can: • make an object move faster or slower, or in a different direction • change the shape of objects.

Measurement of forces • Push forces can be measured with bathroom scales or kitchen scales. • Pull forces can be measured with a spring balance or a rubber band. • Newton is the unit used to measure forces. The weight force of 100 g is one newton (1 N).

air swing

Forces: pushes and pulls

Qm~

movmg

..--

Can change the direction of moving objects

Figure 7..1.1 Different effects of forces

stick hits ball

Figure 7.1.2 The hockey stick pushes the ball. The stick exerts a force on the ball, causing it to move. If you miss, there is no force on the ball.

Experiment: Measuring forces Aim: 10 make and use a force meter usil1g a rubber band and masses. Materials: A thin strip of timber or a ruler, a mass carrier, masses and a pen. Method: 1 Take a 30 cm piece of thin timber and calibrate it as shown in figure 7.1.5. 2 Make a small groove on top of the timber. Attach the rubber band to the groove and hang 100 g mass to the rubber band. :3 Note how far the rubber band stretches when 100 g is attached-that amount of stretch shows the force (1 N) needed to pull an object weighing 100 g. 100 g = 1 N. Complete the scale up to 5 N.

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Can speed up or slow down moving objects


Figure 7.1.4 Your weight force pushes down on the mattress, causing it to change shape.

r

about 30 cm

1

metal top of mass carrier

Figure 7.1.5 Calibrating the force meter

4 Use the force meter to measure the size of the following forces: • force needed to pull the door open • force needed to drag a chair across the floor • force needed. to open a drawer in the laboratory • force needed to move your pencil case • force needed to pull up your sock.

b less force'?

2 Did you experience any problems during your experiment,?

Figure 7.1.6 Measuring the force needed to push a door

3 If so, explain how you would improve the construction of the force meter.

Results: Objects measured

Force required

(N)

Open the door to the room Drag a chair across the floor

Conclusion: Summarise how you constructed

Open a drawer in the laboratory

and used the force meter.

Move your pencil case Pull up your sock Discussion: 1 Which of the actions needed:

a more force'?

Questions

2 What are forces'? What do they do'?

State which of the following actions involve push force, pull force or no force. Actions

Opening a window Turning a screw a with a screw driver Smelling food cooking Moulding clay in an art lesson Hitting the enter key on a computer keyboard Standing on a diving board

Push, pull or no force

3 Rank these forces in order, from biggest to smallest: 1 to 5. a Truck hitting a pole b Rocket being launched c Typing a letter on a computer keyboard d Kicking a soccer ball e Pushing a car along the street 4 Which instruments are used to measure the following forces'?

a push forces

Watching a candle burn Throwing a ball Turning a page in a book

b pull forces

Forces - Pushes and Pulls

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109

Friction Every time something moves, there is a push force acting against it. This force is called friction. Friction slows and stops everything that is moving. The more friction, the sooner the movement stops. Friction happens because objects rub together. Without friction your feet would just slip over the ground. It would be like trying to walk on ice. Air resistance or drag is the friction between a moving object and the air it is moving through. Air resistance is used in parachutes but it is a problem in cars and trucks, because it slows them down. Streamlining (= making the surface smooth and sleek) helps overcome air resistance. For example, cars and planes have streamlined bodies to reduce air resistance. Decreasing friction-rollers or wheels, ball bearings, polished smooth surface and streamlined surface reduce friction. Lubrication also reduces friction by using lubricants such as oil and grease. Lubricants work by coating the surface, making them more slippery and reducing friction. Putting oil and grease on bicycle axles makes them spin more easily, with less friction.

Experiment: Measuring friction Aim: To measure friction of a block of wood using a force meter. Materials: Force meter, a block of wood, a book, 6 rollers and sand. Method: 1 Place a block of wood on the floor and push it as shown in figure 7.2.3. Measure the force needed to make it move.

Increasing friction-rough or irregular surface, treads on car tyres, running-shoe treads, and fingerprint ridges increase friction.

air resistance

Figure 7.2.1 Streamlining reduces friction

2 Place the block of wood on 6 rollers and repeat the procedure. 3 Place a book on the block of wood and repeat the procedure. 4 Spread some sand on the floor and place the block of wood on the sand and repeat the procedure. Results:

Object Block of wood on the floor Block of wood on 6 rollers Book on the block of wood Block of wood on sand

force meter Figure 7.2.2 Measuring the friction of blocks of wood

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Force needed to move block (N)

Discussion:

Conclusion:

1 Which object used less force to move'? Why'?

1 What is friction'?

2 What are some good ways to reduce friction'? 2 Which object required more force to move'? Why'?

:3 What effect did the sand have'? Why'?

Questions

c a car uses more petrol when it has a load on the roof

The racing cyclist

In the drawing above, find two' examples of a using friction:

d it is hard to run on ice (like at an ice skating rink)

b reducing friction:

:3 Ball bearings are uSt1d in roller blades and skate boards. How would these objects move 2 Use the idea of friction to explain why

without ball bearings'?

a surfers put wax on their board

b people driving cars on ice or snow put chains on the tyres

4 Think about how far a toy car and a marble would roll along a flat bench. Which rolls further'? Why'?


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More about forces The size and type of force are factors that affect the movement of an object.

Types of forces forces are when objects move because they are directly pushed or pulled by another object. The objects have to touch each other or be in , e.g. a hockey stick striking a ball. Non- forces are when objects exert a force without any between them. • Gravitational force: exerts a force on us all the time. The force of attraction between objects or masses is called gravitational force or gravity. Gravity holds you on the surface of the Earth. • Magnetic force: magnets exert force on other magnets by attracting or repelling. They also attract some metals without touching them. • Electrostatic force: a force produced when certain materials rub together and become charged. Electrostatic forces attract objects without touching them.

Activity: Forces on a toy car Look at figure 7.3.1 and answer the following questions. force pulling car pulley across table

force pulling masses downwards Figure 7.3.1 The toy car experiment

1 What makes the car move'?

2 Is it a push force or a pull force'? 3 What makes the masses move'?

4 What type of force is this'?

Experiment: Forces Aim:

1 Measure the forces used when pushing against a wall and against another person.

2 To investigate gravitational force usitJg parachutes. Materials: Two bathroom sca les, 4 freezer bags, 16 paper clips of the same size, cotton or nylon thread, scissors and stopwatch. Method:

Part 1-How hard can you push? 1 Place a bathroom scale on a wall and push

Part 2-lnvestigating gravitational force 1 Cut the plastic from the freezer bags

using your hands. Measure the amount of force in kilograms. Multiply the kilograms by 10 to convert it into newtons. 100 g = 1 N 2 With a partner, place two bathroom scales against each other. Push against each scale at the same time and note the force needed to push in each scale.

according to the following dimensions: 10 x 10 cm, 15 x 15 cm, 20 x 20 cm, 25 x 25 cm. 2 Tie the cotton strings to the four corners of each plastic square to make a canopy of a parachute.

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:3 Use 4 paper clips attached to each other in a line to represent the skydiver. 4 Attach the strings of the parachute canopies to the paperclips. 5 Drop each parachute from a height of 2 metres. Using a stopwatch, note the time taken for each parachute to fall down to the floor. 6 Repeat step 5 one more time and record your results in the table below. Calculate the average time taken in seconds. Results:

Figure 7.3 .3

Discussion:

How much force did you use to push the scales against the wall'?

Table 1-how hard can you push? Number of students puehing againet ecalee

Amount of force N kg

2 How much force did you and your partner use to push against the two bathroom scales'?

One student

Two students

:3 What type of force was used in part 2 of the experiment'?

Table 2-Parachutee and gravity Size of

Time taken for parachute to fall (e)

canopy

Trial 1

Trial 2

Average

10 x 10 cm

4 Which parachute took less time to fall down? Explain.

15 x 15 cm 20 x 20 cm 25 x 25 cm

Questions What is a force'? List three examples.

Conclusion: What is the difference between push force and gravitational force'?

:3 If the bathroom scales indicate you weigh 60 kg, how many newtons is this'? 4 If Sally can push with 150 N force, and Rod with 200 N force, what is the final force used if they pushed a in the same direction'? b in the opposite direction? 5 What forces act on a motor cyclist who is a stationary on the ground,?

2 How are gravitational and magnetic forces different from forces'?

b moving across the ground at a constant speed'?


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Magnets and magnetic force Magnets can attract materials containing iron, nickel and cobalt. Magnets can also attract steel, which is an alloy (= mixture of metals) of iron. A material that is attracted by magnets is called magnetic material. The force exerted by a magnet is called a magnetic force and it is a non- force.

Properties of magnets • A magnet can attract magnetic materials by turning them into temporary magnets. Temporary magnets are weak and lose their magnetism easily. • You can use steel to make a permanent magnet. Permanent magnets do not lose their magnetism easily. • All magnets have ends called poles. These ends are known as the north pole and the south pole. The north pole of a magnet is known as the north -seeking pole because

L!D I~~ Li~ -+

poles

Uolike poles

Figure 7.4.1 Magnets can exert forces on magnetic materials and other magnets without touching them

Experiment: Magnetic forces Aim: 1 To test which materials are magnetic and non-magnetic. 2 To test forces between two bar magnets. Materials: Copper, paper, lead, rubber, wood, steel, magnesium, aluminium, plastic, zinc, paperclip, iron nail, 2 bar magnets, string, retort stand and a clamp.

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Domain theory of magnetism • A magnet is made of millions of micromagnets or domains. A strong magnet (permanent magnet) has most of its domains lined up to reinforce each other. In weak magnets (temporary magnets) only some of the domains line up. The domains are not used to being in this new position and will soon go back to their old position. When this happens the magnetism is lost.

............................. ...... ... "" ......... "" ............................ strongly magnetic

.... "'!.. .... .,. .... ""'t.',""t .... "", ... ............................. .,.~""

.,. ................ t .... ,

... l't .......t"' or......... ''''' ...

It'

non-magnetic

weakly magnetic

one magnetec domain

S-+N

Figure 7.4.2 The magnetic domain theory

...

mJ II:]

when it is suspended it rotates to point to the north pole of the earth. • Like poles (= poles of the same kind) repel each other. Unlike poles (= poles that are different) attract each other.


• Some metals (e.g. iron) can be magnetised by stroking them with a permanent magnet. If you stroke the iron in the same direction, and with the same end of the magnet, the iron will become a temporary magnet. • You can destroy the magnetism in any magnet or magnetic object by hammering and banging on it. This knocks the domains out of their positions. You can also heat the magnet. This causes the domains to vibrate faster and they may lose their positions. Method:

Part 1-Magnetic or non-magnetic? 1 Place the materials given to you on a small tray. Take a bar magnet and test each material to see if it is attracted by both ends and the middle of the magnet. Part 2-Testing forces between magnets 1 Use a string to suspend a bar magnet from the retort stand. Take the north pole of the free magnet near the north pole of the suspended magnet and see what happens.

Table 2-Forces between magnets

2 Repeat this procedure with the south poles. 3 Repeat this procedure with two unlike poles. 4 Record your results in table 2.

Poles tested

Attracted or repelled

N-S S-N N-N S-S Figure 7.4.3

Discussion:

Which materials were magnetic'? Results:

Table 1-Magnetic and non-magnetic substances

2 Which materials were non-magnetic'?

Place a t ick in the relevant column.

Material

Attracted

Not attracted

Copper Magnesium

3 Which part of the magnet was strongest in

Paper

attracting materials'?

Zinc Lead Aluminium

Conclusion: Complete the following statements.

Rubber

1

Plastic

substances are attracted to a magnet and

Wood Paper clip Steel Iron nail

substances are not. 2 Like magnetic poles

each other and

unlike magnetic poles

Questions Why is one part of the magnet called a north pole'? 5 Use the domain theory to explain why magnets can be weak and strong. 2 What is the difference between a permanent magnet and a temporary magnet'?

3 What is a domain'?

6 List two ways in which magnetism in a magnet can be destroyed.

4

Describe how a temporary magnet can be made.


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Magnetic fields Magnets have an invisible magnetic field through space around them. • All magnetic fields are three-dimensional. • When another magnet or an iron object enters the field it experiences a force as either a push or a pull. • You cannot see, smell or hear a magnetic field but you can detect it using a plotting com or iron filings. Each iron filing becomes a temporary magnet and the magnetic force on it turns it in the direction of the field.

• The shape of the magnetic field between two magnets depends on the closest two poles of the magnets. • If the closest two poles are unlike, the magnetic fields of the magnets attract each other and are concentrated between them. • If the closest two poles are like poles, the magnetic fields repel each other. • A magnetic field is strongest around the magnet's poles. A strong magnet's magnetic field extends further than a weak magnet's magnetic field. a.

b. Which magnet is stronger?

Figure 7.5.1 The pattern of iron filings in a magnetic field-the pattern is less distinct the further the filings are from the magnet

Figure 7.5.2 a. The regular pattern or shape to the magnetic field between the magnets shows that they are equally strong.

Why?

Earth's magnetic field The Earth produces a magnetic field as though it has a giant bar magnet going through its centre. The Earth's magnetism is called geomagnetism. The Earth's magnetic field is produced by circulating electric currents in its outer liquid core. The Earth's magnetic field extends far into space beyond the atmosphere, where it is called the magnetosphere.

Figure 7.5.3 The Earth's magnetic field does not line up with the Earth's axis. A com will not point to true north and south, but instead points to magnetic north and south

Science fact Earth's magnetic field The Earth's magnetic field flips once every 200 000 000 years or so reversing the positions of the North magnetic pole and the South magnetic pole. The last reversal happened about 750000 years ago.

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Experiment: Magnetic field shapes

a

b

Aim: To map the magnetic fields around different shaped magnets using iron filings. Materials: Two bar magnets, one horseshoe magnet, a sheet of paper, pepper shaker containing iron filings, two science books and plastic wrap. Method: Wrap all magnets with plastic wrap before using them.

~

c

f{

Iron filings

d

Paper Book

Magnet ..~'''''~_ ~GentlY tap paper

-

~-::::===>.'.~~~I~~~~~ ~ I~

e

Figure 7.5 .4

Place a bar magnet in the middle of two books as shown in figure 7.5.4. Place a piece of paper on the books and sprinkle the iron filings above the magnet and shake the paper. 2 Find the shapes of the field lines for'the arrangement of magnets a to f shown in figure 7.5.5. Copy the general shape of the field lines on the diagrams. :3 Use a com to find out which way the arrows should go in your diagrams. Results: Draw the magnetic fields for the arrangements a-f in figure 7.5.5. Discussion: Does a magnetic field act through a nonmagnetic material such as paper? Explain.

Figure 7.5.5

2 Why does tapping the paper sheet help the iron filings to form the pattern of the field lines?

:3 What would be the effect on the field line patterns if you moved the magnets further apart? Conclusion: Do magnetic fields around bar

magnets and a horseshoe magnet have definite shapes?

Questions What is a magnetic field?

:3 Why should the magnets be wrapped in plastic wrap when plotting the magnetic fields?

2 By looking at the magnetic fields made by different magnets, can you decide which

4 What is meant by geomagnetism?

magnet is stronger?

Forces - Pushes and Pulis

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Types and uses of magnets Permanent magnets used at schools are made of a material containing iron. They ha~e a type of magnetism called ferromagnetism. Another group of important magnetic materials are called ferrites. They are made from iron, oxygen and other elements. These materials are light. Ferrites are used in audiocassettes, videotapes, floppy disks and computer hard disk drives. Magnetism is the main way information is stored in computers and CDs. Supermagnets are strong permanent magnets made from boron, iron and neodymium. They are small and used in electric motors, hi-fi speakers and computer printers. Electromagnets are made by coiling a wire around pure iron. When electricity flows through the wire, magnetism is produced and this magnetises the iron. When the electricity is turned off the magnetism disappears. Electromagnets are used in telephones and electric bells. Huge electromagnets are used in scrap yards.

Experiment: Temporary magnets Aim :

1 To make an electromagnet by ing electricity through a nail.

2 To make a temporary magnet by stroking an

Superconducting magnets are electromagnets with coils of wire that are superconductors. Normal wire slows the movement of electricity and it gets hot. A superconductor allows electricity to flow with no energy loss. All of the energy goes into the magnetism, not into heating the wires. They are large and expensive. They are mainly used in research laboratories and hospitals. MRI (magnetic resonance imaging) uses powerful magnets to obtain images of the insides of people. MRI scans are clearer than X-rays or CAT scans and can show tiny cancers that are too small to detect any other way.

Comes A com is a weak magnet that lines up with the Earth's magnetic field. The north pole on a com always points to the magnetic north pole of the Earth. The Chinese used the first comes in 300 BC Comes are useful for navigation. :3 Press the switch so

tha~

electricity can , through the iron nail. 4 Turn the electricity on and off and test if the electromagnet attracts iron pins and paper clips.

iron nail with a permanent magnet. Materials: 2 large iron nails, two pieces of insulated copper wire (one long and one short), a battery, a switch, 4 iron pins, 4 papercU_ps and a permanent bar magnet. Method:

coils of wire

Part 1-Making an electromagnet 1 Coil the long piece of copper wire around the large nail tightly. Attach one loose end of the wire to the switch and the other end to the positive terminal of the battery as shown in f igure 7.6.1. 2 Attach one end of the second copper wire to the negative terminal of the battery. Attach the other end to the second terminal of the switch.

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switch Figure 7.6.1 Setting up the electromagnet circuit

Part 2-Magnetieing a nail 1 Stroke the iron nail with a permanent magnet. Stroke the nail in the same direction and with the same end of the magnet. 2 Test the magnetism of your temporary magnet using iron pins and paper clips. 3 Demagnetise your temporary magnet by dropping it or hitting it to destroy the magnetism. 4 Test it again to see if it attracts the iron pins and paper clips. Results: Complete the table-put a tick if it is attracted and a cross if it is not attracted. Type of magnet

Paper clipe

Iron pine

=

t

Figure 7.6.2 Making a temporary magnet

2 Is an electromagnet a permanent magnet or a temporary magnet'?

3 What happened when a nail was stroked with a permanent magnet'?

4 What happened when the magnetised nail was dropped on the floor'?

Electricity on Electricity off Magnetised nail

Conclusion: What is the difference between a

Demagnetised nail

temporary magnet and an electromagnet'?

Discuesion:

What happened when electricity was ed through the nail'?

Questions

3 When and by whom were comes

Name two uses of the following magnets: Typee of magnete

developed'? What are they used for'?

Ueee

Ferrites

Super magnets

4 What is the advantage of an electromagnet compared with a permanent magnet'?

Superconducting magnets 2 What do the letters MRI stand for'? What is it used for'? 5 List 3 appliances at home where magnets are used.


119

Static electricity Static electricity is produced by friction when materials are rubbed together. The study of static electricity is called electrostatics.

Types of charges All matter is made up of small particles called atoms. Atoms are made of smaller particles called electrons, neutrons and protons. Protons and neutrons are found in the nucleus (centre) of the atom. Electrons are smaller in size and move around the nucleus at high speed. • Electrons have negative charge. • Protons have positive charge. • Neutrons have no charge. Neutral atoms have equal numbers of electrons and protons. Rubbing can tear electrons from certain atoms and they become positively charged. Other atoms gain electrons and become negatively charged. nucleus

electron

+ neutron

How to create static electricity Non-metals that are insulators can be used to produce static electricity. Insulators do not conduct electricity. When an insulator is rubbed, electrons are either removed or added and the object becomes charged.

Laws of electrostatics • Unlike charges attract-two charged objects will attract each other if they have opposite charges. • Like charges repel-if they have the same charge, they will repel. • A charged object attracts an uncharged object. A charged object has an electrical force field around it and other objects will be attracted or repelled. The electric field is much weaker than a magnetic field. Since static electricity can attract objects without touching them, it is an example of non- force. We cannot map the electric field easily. An electroscope is used to detect an electric charge.

proton

Figure 7.7.1 The parts of an atom

Experiment: Investigating electrostatic charges Aim: To produce static electricity; . Materials: A balloon, a perspex rod, pieces of wool and silk, small pieces of paper and running tap water. Method:

4 Take the charged balloon near running tap water and observe what happens. 5 Repeat the above steps with a perspex rod rubbed with wool.

Caution: do not put the charged rod near anyone's face or eyes. 1

Blow into the balloon and tie off the end when it is inflated with air. Rub the balloon with a piece of wool and release it near a wall. Observe what happens. 2 Rub the balloon over a friend's hair and observe what happens. 3 Take the charged balloon near small pieces of paper and observe what happens.

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Figure 7.7.2 Using charged rods

Results: Record your results in the table- put a tick if it is attracted.

Objects tested

Charged balloon

Charged perspex rod

3 What happened when a charged perspex rod

Wall

was taken near paper, hair and water?

Paper Hair Water

Conclusion: How did you create static electricity in this experiment?

Discussion:

Which objects did a charged balloon attract?

2 Why did the balloon stick to the wall?

Complete the following: Atoms are made of particles called

, neutrons and

are found in the around the

of the atom .

. Protons and are

in size and move

at high speed.

Electrons have

charge, protons have

A charged object has an

force

charge and neutrons have

charge.

around it and other objects will be attracted

or

Questions

3 State the laws of electro?tatics.

Match the words with the correct meaning by placing the number with the letter.

Word

Meaning

Answer

A Positive charge 1 More electrons than protons B Electrostatics 2 More protons than electrons C Static 3 Detects electric electricity charge D Negative 4 Made by rubbing insulators charge 5 The study of E Electroscope static electricity

-

2 a Explain what happens when an object is charged by rubbing.

• • •

Science fact Discovery of static electricity 'Electricity'is derived from the Greek word 'elektron', which means amber. In 600 Be ancient Greeks noticed that jewellery made of amber attracted small pieces of fluff. This was caused by static electricity. Question: Why was the fluff attracted to

the amber?

b What type of electricity is made?


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Sparks and lightning Benjamin Franklin's kite experiment In 1752, Benjamin Franklin flew a kite in a thunderstorm. When Franklin's hand was near a key he had attached to the string of the kite, a spark jumped between the key and his finger. This convinced him that lightning was a type of electricity. He was very lucky not to be killed.

Figure 7.B .l Benjamin Franklin's kite experiment

Thunderstorms and lightning A thunderstorm is a storm with lightning and thunder, produced by a cumulo-nimbus cloud (storm cloud). Storm clouds are a mass of swirling water drops and ice crystals. Lightning is the end result of ice crystals being charged in thunder clouds. Static electricity is produced when air rubs against the ice crystals as currents carry them up and down within the cloud. The top layer of the cloud becomes positively charged. Negative charges or electrons collect at the bottom of the cloud. The ground and buildings underneath the cloud become positively charged. Sparks, or lightning, occur as the electrons jump towards the positive charges. The lightning can go from a cloud to the ground, but it occurs most often within a cloud, producing flashes of light in the cloud. Its brightness is equivalent to 100 million light bulbs going on and off. The high temperature of the lightning spark causes the air through which it travels to expand very quickly. It is this rapid expansion of air that sets up the vibrations you hear as thunder. We see lightning first and then hear the sound of the thunder because light travels faster than

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sound. When lightning strikes, it travels to the gr~und along the shortest path. It may strike any object above the ground, including people.

Positive charges collect + + \ in highest clouds. + +

Figure 7.B.2 Lightning is caused by the positive and negative charges in clouds

What to do during thunderstorms • Telephone lines and metal pipes can conduct electricity. Unplug ,electrical appliances and avoid using the telephone. • Avoid bathtubs, and do not hold on to taps. • Draw blinds and and shades over windows. • Do not stand in the open or under a tree or under an umbrella. • Seek shelter in a building or a car. • If there is no shelter, lie on the ground till the storm es.

Science fact Lightning and thunder storms There are around 1500 to 2000 thunderstorms active around the world at any given time. Lightning flashes 100-125 times per second. Eight million lightning bolts hit the Earth each day. Lightning leaps between the clouds and the Earth at a remarkable speed of 120 000 km per second and carries 20 million volts of electricity. Each year approximately 100 Australians are hurt by lightning.

Demonstration: Van de Graaff generator

Caution: Students with heart trouble should not use the Van de Graaff machine. Write down your observations:

The Van de Graaff generator is also cal led

•

A student touches the large metal dome.

•

A wig is placed on the dome.

•

A fluorescent tube is taken near the dome.

•

Smaller dome is taken near the larger dome.

an electrostatic generator. It uses a rubber belt driven by an electric motor. The belt rubs against a brush and the electrons are removed from the dome and become positively

Figure 7.B.3 Using a Van de Graaff generator

charged. Large Van de Graaff generators are used to study the inside of atoms. Small machines are used in schools to demonstrate static electricity.

Complete the following: Lightning is the end result of

being charged in

electricity is produced when

rubs against the ice crystals. The

layer of the cloud becomes collect at the

clouds.

. Negative charges or

of the cloud.

Lightning occurs as t he

j ump towards the

charges.

Questions State whether the following statements are true or false.

Statements

True or false

There are more than 100 lightning

-

strikes on the Earth every second Lightning never strikes during rain There are no thunderstorms in Antarctica 2 Why do you see lightning before you hear the

4

Explain how a Van de Graaff generator works.

thunder'?

3 Explain what causes lightning and thunder.


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Review and research Review questions In Questions 1 to 10, select the best answer from the choices given. 1 The field around a bar magnet is: A electrical B gravitational C energy D magnetic 2 The field around a charged perspex rod is: A electrical B gravitational C energy D magnetic 3 The two types of static electricity are: A north and south B positive and negative C up and down D left and right 4 The two poles of a magnet are: A north and south B positive and negative C up and down D left and r ight 5 The stream of water is attracted towards the rod when it is brought near. Th is is because: A the rod is neutral B the rod is charged C the water is charged D the water is magnetic 6 A com needle always points north because: A of the spin of the Earth B it is like a gyroscope C it responds to the Earth's magnetic field D comes are made to do that 7 The strongest magnets belong to the group called: A ferrites B ferromagnets C supermagnets D superconducting magnets 8 Around the Earth are some f ields, which are: A magnetic and electric B electric and gravitational

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C gravitational and magnetic D gravitational, electric and magnetic 9 An electroscope is used to: A detect an electric charge B determine if there is magnetism C see if a charge is positive or negative D make an electric charge without rubbing 10 Lightning is: A caused by thunderstorms B the result of static electricity in storm clouds C always after the .thunder D seen in storm clouds after rain 11 Circle the odd one out and give a reason :

a copper, aluminium, zinc, iron b pole, friction, positive, magnetise

c electric, electronic, magnetic, gravitational

12 Match the word with its meaning : Word

Meaning

A Magnetosphere

1 Magnetism around the Earth

B Geomagnetism

2 Magnetism in and around a nail 3 Magnetism caused by

C Ferromagnetism

electricity D Electromagnetism 4 Magnetic field of the Earth

13 Define the following : a an electromagnet

Anewer

b a supermagnet

14 Describe how you could make an electromagnet.

Extension experiment Do some clothes or fabrics get static electricity more than other clothes? How could you find out? Design an experiment with a control and write your report in your notebook.

Research questions 15 The diagram below shows the pattern of iron filings over some bar magnets. Use the pattern of iron filings to label the poles as north and south .

Use the Internet or other resources to answer one of the following questions. 1 What are Van Allen belts? What do they do and why are they important? 2 What is meant by maglev ( magnetic levitation )? How is it used in launching trains and spacecraft? 3 A photocopier works by static electricity. Investigate how a photocopier uses static electricity. to create a photocopy.

Word check 16 A student takes a rod and hangs it from a loop of string. Her friend then brings another charged rod near it. The hanging rod moves away, as shown in the diagram. What can you deduce (infer) about the charges on the rods?

17 Why is it dangerous to stand in an open field during a lightn ing storm?

Write the meanings of the following words in your notebook. Air resistance Geomagnetism Super conducting magnets Law of electrQ- Permanent Domains statics magnet Positive charge Domain theory Lubrication Electron Pull forces Lightning Electroscope Magnetosphere Push forces Electrostatics Magnetic field Static electricity Electromagnet Magnetic force Streamlining Ferrites Magnetic Super material magnets Ferromag netism Magnetic poles Temporary magnet Force Negative charge Thunder Friction Newton

Mind map Draw a mind map of the concepts outlined in this chapter in your notebook.


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CHAPTER 8: HEAT, LIGHT AND SOUND ENERGY

Energy forms Energy is something that is needed to make things happen. Without energy there would be no change and no movement. Energy is the ability to do work. There are two main forms of

-

-

r-

Potential energy (stored energy)

;

-

I

Energy

~

"-

Kinetic energy (active energy)

energy: potential energy (stored energy) and kinetic energy (active energy), which have many forms, as shown in the flow chart (figure 8.1.1).

Gravitational energy: stored energy in raised objects. A person standing on a diving board has gravitational energy. The gravity of the Earth pulls them down.

Elastic energy: stored energy in stretched objects. When you bounce up and down on a trampoline the elastic energy in the trampoline pushes you upwards.

Nuclear energy: the centr~ of the nucleus of an atom has large amounts of stored energy, which can be released by fission (dividing the atom).

~

.+: .

,

,

&Y

Chemical energy: energy stored in fuels, food and batteries.

-

Magnetic energy: magnets have a magnetic field around them, which attracts magnetic material within the field.

-

Light (radiant) energy: energy produced by luminescent objects such as the Sun, stars and bulbs. Includes light, X-rays, microwaves, infrared waves.

-

Sound energy: energy made by vibrating objects. Speech and music are caused by vibrating objects.

)

-

-

_ Heat energy: increase in temperature causes tiny particles in substances to move more, Heat is transferred by conduction , convection and radiation,

Electrical energy: the flow of electrons in the conductors and circuits in appliances such as TV, radio and computer,

Figure 8.1.1 Different types of energy

Theory of conservation of energy Energy can be changed from one form into another. No energy is destroyed and no new energy is created in the change. The amount of energy is conserved. This is called conservation of energy. For example:

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• Chemical energy in a candle is changed to light and heat energy. • In a wheat field, solar energy is converted into chemical energy in food. • In a telephone, sound energy is converted into electrical energy, then into electromagnetic energy and finally back to sound energy.

Experiment: Energy changes Aim : To investigate changes in energy forms. Material5: A tuning fork, a shallow dish of water, one test tube, spatu la, vinegar and sodium

bicarbonate, zinc plate, copper plate, two wires, sa lt water, 200 mL beaker, ammeter, nichrome wire and copper wire, Bunsen burner, meta l tongs and matches. Method: Foll ow the procedures given in the table and write the type of energy changes you observed. Procedure

Energy change

Strike a tuning fork and place the end of the fork in a shallow dish containing water. In a test tube add one spatula of sodium bicarbonate to 5 mL of vinegar. Touch the test tube after the reaction and see if it is hot or cold. Connect a copper plate and zinc plate to an ammeter. Place these two metal plates in a beaker containing 100 mL salt water and observe the reading of the ammeter. Connect one end of a copper wire and a nichrome wire to an ammeter. Twist the other ends of the wires together and heat the t in the blue flame of a Bunsen burner. Note the reading in the ammeter. Di5cu55ion and conclu5ion:

What conclusions can you draw from conducting the experiment?

Questions Match the following with their definitions:

Definitions

Answers

A Potential energy

1 Active energy caused by movement

B Kinetic energy

2 Stored energy which can be released

C Radiant energy

3

It is the flow of electrons in the conductors

D Sound energy

4

When temperature increases the particles move faster

E Heat energy

5 Energy made by vibrating objects

F Magnetic energy

6 Energy produced by luminescent objects e.g. Sun

G Electrical energy

7 Energy possessed by magnetic objects

H Chemical energy

8 Energy stored in objects which are high up

I Elastic energy

9 Energy stored in fuels and food

J Gravitational energy

10 A change from one energy type to another

K Energy transformation

11 Energy possessed by stretched objects

2 Give 2 examples where energy is tra nsformed from one for m into another.

3 State in your own words the theory of conservation of energy.

Heat, Light and Sound Energy

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Heat energy Heat energy is a type of energy that moves from places of high temperature to those of lower temperature. Heat energy is measured in joules G). Heat and temperature are different but are related to each other. Temperature is a measure of the degree of hotness or coldness of something. Temperature is measured in degrees Celsius (0C) using a thermometer. Heat can be transferred in different ways through different materials. There are three types of heat transfer: conduction, convection and radiation.

Good conductors, such as metals, heat up and cool down more quickly than poor conductors. Poor conductors include all nonmetal solids, most liquids and all gases. Liquids and gases conduct heat more slowly than solids because their particles are widely spaced. Poor conductors of heat energy are called insulators. Insulators retain heat longer. Rubber, glass, wood, air, wool and cotton are good insulators.

wooden ruler

Conduction Conduction is energy transfer in a solid where heat energy is ed from particle to particle. When you heat a solid substance, its particles at the heated end absorb the heat energy. The heat energy changes into kinetic energy and particles vibrate more rapidly. Hot particles transfer this kinetic energy to colder particles in the solid. A solid conducts heat better than a gas or a liquid because in solids the particles are closer together.

Experiment: Heat transfer by conduction Aim: To investigate how heat travels by conduction in different metals. Materials: Bunsen burner, tripod stand, 3 bricks, aluminium and iron strips of equal length and width, candle wax and 6 toothpicks. Method: 1 Place two strips of alumin ium and iron as shown in figure 8.2.2. strip of iron ---7 topthpicks held . .. ______ ./ with wax striP of aluminium

hot water Figure 8.2.1 Which ruler is the best conductor?

3 Heat the ends of the' metal strips with a Bunsen burner and note the time taken for each toothpick to fall off. Results:

Metal strips

Time taken for the tooth(eiCkS to fall off after heating seconds) Toothpick 1 Toothpick 2 Toothpick :3

Aluminium Iron Discussion: From which metal did the toothpicks fall off quickly'? 2 Which of the metal strips conducted heat faster'? Conclusion: How did the heat energy move in metals'?

Figure 8.2.2 Conduction in metals experiment

2 Place three toothpicks on each metal strip with the help of melted wax.

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Convection Convection is the transfer of heat energy in liquids and gases caused by differences in temperature within them. Tiny currents called convection currents are the movements of heated particles in liquids and gases. Hot particles rise through the colder liquid and colder, denser liquid sinks to take their place. These colder particles are then heated and they rise, and the process continues.

Liquid

4t4t4t 4t4t .;.r---4t 4t 4t ® 4t 4t 0

0

4t ,4t 4t 4t

0

§

Convection currents

Gas

Hot particles rising Cooler particles sinking

§

Figure 8.2.3 Convection currents in heated liquids and gases

one drop of dye

Experiment: Heat transfer by convection Aim: To investigate how heat travels in liquids through convection currents. Materials: 2 Bunsen burners, 2 tripod stands, 2 gauze mats, 2 heat mats, potassium permanganate solution, pipette, two 500 mL beakers and water. Method: 1 Half fill two beakers with water and heat each beaker on a different Bunsen burner using a blue flame. 2 Add one potassium permanganate drop down the side of each beaker as shown in figure 8.2.4. 3 Heat for about half a minute to start convection currents and observe how they move in each beaker. Results: Draw the convection currents in the beakers after the dye was added in figure 8 .2.4.

' " gauze mat tripod stand 11.4.~,------'lc-

Figure 8.2.4 Setting up convection currents in water

Discussion: What happened in each beaker when the dye was added to the hot water?

Conclusion: How did the heat energy move in the water? Explain what happened to the water molecules as they were heated and then cooled .

Radiation Radiation is giving out heat. It takes place without any heat-transferring matter-it can even travel through space. Any hot object will emit radiant energy. The hotter the object, the more radiant heat it emits. Warm objects emit radiant energy in the form of invisible infrared radiation. As the temperature of metals increases, they emit visible light as well as infrared radiation. The filament of a glowing light bulb emits white light, which you can see. If you hold your hand below a glowing light bulb, you will feel heat energy as it absorbs the infrared radiation. Radiant energy can be absorbed, reflected or transmitted by objects.

Bunsen burner

@ Absorbed / / Reflected

r(/

Radiant energy \\ . \ : jTransmitted

!~P SUve~ T~:parent\ object

~

Large rise in temperature

opaque object -=:J

Medium rise in temperature

object

-=::J

Small rise in temperature

Figure 8.2.5 Absorbing, reflecting and transmitting

Heat, light and Sound Energy

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Experiment: Absorption and radiation of heat Aim: To investigate which colour absorbs and rad iates heat best. Materials: 2 aluminium drink cans, steel wool, black paint, two thermometers, plasticine, an electric heater. Method: 1 Paint one of the cans with black paint and make the other can shine using steel wool. 2 Place thermometers in each can through a hole and hold them in place with the help of plasticine. 3 Place the two cans either in bright hot sunlight or in front of an electric heater. 4 Record the temperature of each can every 2 minutes for 10 minutes. Record your results in table 1. 5 After 10 minutes, remove the. cans and place them in the shade or take away the heater. Record the temperature of each can every two minutes for 10 minutes. Record your results in table 2. 6 Graph the results for each can over the whole 20 minutes (use graph paper).

Results: Table 1-Absorbing heat

Time since Temp. of start (mins) black can (CO)

Temp: of shiny can (CO)

0 2 4

6 8 10 Table 2-Radiating heat

Time since Temp. of start (mins) black can (CO)

Temp: of shiny can (CO)

0 2

4 6 8 10

Discussion: How do the cans absorb or lose heat'?

2 Which can absorbed the most heat during the 10 minutes'? 3 Which can radiated the least heat during the 10 minutes'?

Conclusion: How does co lour affect heat absorption and radiation'?

Figure 8.2.6

shiny white can

dull black can

Vacuum flask (thermos flask) Vacuum flasks are used to keep hot liquids hot and cold liquids cold. They have been designed to prevent heat loss by conduction, convection and radiation. Flasks consists of: • two layers of glass or metal that have a vacuum between them-this means that most of the air has been pumped out and no heat can through by conduction or convection because there is no air • a bottle that is shiny on the inside and outside-this reduces the amount of heat lost by radiation. 130

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strong protective case

double glass shiny or metal walls surfaces

air pumped out

Figure 8.2.7 The inside of a vacuum flask

cork to stop flask from moving

Questions Complete the table by naming the type of heat transfer occurring. Medium re~uired for heat tram; er

Type of heat tran9fer

Transfer of heat by the

7 People suffering from hypothermia (extreme coldness) are wrapped in reflective silver blankets, which reflect their body heat back to their skin and thus increase their body temperature. What happens if people suffering from hypothermia are wrapped in normal woollen blankets?

movement of particles in tiny currents in liquids and gases Heat energy is ed from particle to particle in a solid No medium is required

8 Which car would get hotter more quickly on a sunny day? Why?

2 Which will cool more quickly from 9UC: a full cup of tea or a full teapot made of the same material as the cup? Why? Figure 8.2.8

3 Identify the following materials as good conductors, poor conductors or insulators:

a copper b glass c

plastic

d steel

e water f

9 Explain how cold water in a saucepan placed on a stove would heat up, using the idea of convection.

rubber

4 Why do you feel hot if you stand near a fire?

5 What is the difference between absorption and radiation?

6 In a thermos flask, what is the purpose of removing the air between two layers of glass or metal?

Science fact Radiation Heat radiating from the Sun takes just over 8 minutes to reach the Earth. Heat radiating from the sun travels at the same speed as the light from the Sun, about 300 000 kilometres per second.


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Ught energy What is light? Light is a form of electromagnetic energy that can be detected by our eyes. • Light can travel in the form of waves through air, water, solids, and even through a vacuum. • Light travels at 300 000 kilometres per second. It can orbit Earth 8 times in one second. • Light travels in a straight line in one medium, but if it es through another medium it refracts (it bends).

Types of objects • Luminous objects produce their own light, e.g. the Sun, stars, a lighted candle, fire, light bulb, glow worms etc. • Non-luminous objects do not produce their own light but can reflect light, e.g. mirrors and the Moon reflect light. • Transparent material transmits light (allows all light to through it), e.g. air, water, glass, clear plastic. • An opaque material does not allow light to through it, e.g. wood and paper but a shiny mirror can reflect light rays (bounce back).

Experiment: Pinhole camera Aim: To make a pinhole camera and observe the image formed. Materials: A cardboard tube, aluminium foil, waxed paper, 2 rubber bands, clear pl.astic food wrap, a candle and matches. Method: 1 Assemble a model of a pinhole camera as shown in figure 8.3.2. Make a small, regular pinhole in the aluminium foil.

f j ~~~h:::h1C ~. Lwrapped rubber bands

aluminium in it

cardboard tube

Figure 8.3.2 Assembling a pinhole camera

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paper

• A translucent object lets some light through it, e.g. tissue paper, frosted glass, oily paper.

Formation of shadows Shadows are areas of darkness created by an opaque object blocking light. If the light comes from a single point, such as a tiny torch bulb, the shadow has a sharp, clear edge. This is called umbra. Light from a wide source such as a fluorescent tube will form a shadow with a fuzzy edge-this is called the penumbra. penumbra

opaque object

Figure 8.3.1

2 Light a candle and aim the aluminium foil end of the model towards the flame. :3 Adjust the position of the model until you can see a clear image on the waxed paper end of the model. 4 Move the candle closer and then further away and observe the size of the image. 5 Replace the waxed paper with plastic food wrap and observe the image. Results: Draw a diagram of the candle as seen through the pinhole camera.

Discussion: What happens to the size of the image when

2 How does the image appear when the clear plastic wrap is used?

the candle is moved closer? Conclusion: Describe the nature of the image formed in the pinhole camera .

Reflection of light Reflection is the process in which light travelling in one material bounces off the surface of a second material which is smooth. You can see yourself in a mirror when light reflects off the silvered surface of the mirror.

Normal Incident ray

Nature of images Your image in a flat mirror is right side up, of the same size but laterally inverted (left to right). It cannot be projected onto a screen. This type of image is called a virtual image.

Drawing diagrams of reflection When drawing diagrams of reflection you need to know the meanings of these : • incident ray-the incoming ray of light that hits the mirror • reflected ray-the outgoing ray of light leaving the mirror • normal-a perpendicular line drawn between the incident ray and reflected ray • angle of incidence-the angle between the normal and the incident ray • angle of reflection-the angle between the normal and the reflected ray.

laws of reflection • The angle of incidence is equal to the angle of reflection. • For a plane mirror the incident ray, the reflected ray and the normal are on the same plane.

Experiment: Reflections in mirrors Aim: To observe the reflection of rays of light: 1 by a plane mirror, and 2 by curved mirrors. Materials: Paper, pencil, plane mirror, concave mirror, convex mirror, light box, slide with one sl it, slide with three slits, protractor, 12 V power pack, paper and pencil.

Reflected ray

Plane or flat mirror Figure 8.3.4 Rays of light on a plane mirror

Types of mirrors Plane mirrors are flat in shape. The images are the same size as the object, right side up and laterally reversed. They are used at home (e.g. in bathrooms), and in periscopes. Concave mirrors are curved inwards. They are also known as mirror converging mirrors because the reflected rays meet at a focal point (converge) in front of the mirror. The image is enlarged, right side up and laterally reversed. They are used in Figure 8.3.5 makeup mirrors. Convex mirrors are curved outwards. They are called diverging convex mirrors because the reflected rays mirror move away from each other (diverge) and do. not meet. The image is smaller, the right side up and provides a wider view. It is used in rear-view mirrors of cars and at Figure 8.3.6 corners of roads. Method:

Part 1-Reflection in a plane mirror 1 Connect the light box to the power pack and place it on a sheet of paper. Put the slide with one slit in the light box so that a Single beam of light comes out.


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2 Mark the position of the mirror by drawing a horizontal line. Mark the incident ray and the reflected ray. :3 Remove the mirror, and the light box and draw a perpendicular or normal line between the reflected and incident rays. 4 Use a protractor to measure the incident angle and reflected angle. 5 Repeat this experiment by placing the light box at different angles two more times. 6 Measure the incident angle and reflected angle and record your results in the table. Results: Part 1 Label the diagram and complete the table.

light

box

Figure 8.3.8

light

box

Figure 8.3.7

Figure 8.3.9

Results: Part 2 Label the ray diagrams above (figures 8.3.8 and 8.3.9) for concave and convex mir rors. Discussion: What in general did you find about

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Angle of incidence

Angle of reflection

1 2

the angle of incidence and the angle of reflection?

3 Method: Part 2-Reflection in curved mirrorl3 1 Replace t he single slit plate wit h a three-slit plate to get three parallel rays of light coming out of the light box. 2 Place the concave mirror halfway along the incident light rays so that the rays strike its inside surface and focus the rays. :3 Mark the position of the mirror on the paper by tracing around it with a sharp Eencil. Trace the incident and reflected rays. 4 Repeat steps 2 and 3 with a convex mirror.

Questions How does light travel?

Conclusion: State the law of

2 Describe how· light rays are reflected from concave and convex mirrors.

c

opaque

d incident ray

e reflected ray 2 Define the following : a transparent b translucent

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refl~ction .

f

normal

Sound energy Sound is a form of energy that is produced by vibrating objects. The energy produced by the vibration is transferred to the air. Air particles start vibrating and the vibrations on to other air particles. The vibrations cause energy to travel as waves through the air away from the object.

Properties of sounds • Sound vibrations can travel through solids, liquids and gases. They cannot travel through a vacuum. • A sound wave is a back-and-forth motion of air particles as energy es through them. • When sound energy travels through air it creates alternating areas of high pressure and low pressure. Stretched apart (low p particles

Distance between 2 high-pressure areas= ~ wavelength II». ~

• Frequency of sound is the number of sound waves produced each second. It is measured in Hertz (Hz). Vibrations that have a high frequency produce high-pitched sounds. Vibrations that have a low frequency produce low-pitched sounds. • The decibel scale (dB) is used to measure sound levels. Above 120 dB can be painful and result in loss of hearing.

Echoes When sound waves strike hard surfaces they are reflected back and you hear an echo. • Ships and boats can use echo-sounding equipment to estimate the depth of water and the position of objects below them. • When bats produce sounds, the sound waves hit objects and echo back to them, so that they can locate the objects. • Echoes can be a nuisance in theatres or concert halls. Carpets, curtains and soundabsorbent wall s are used to absorb unwanted sounds.

Demonstration: Bell jar experiment Set up the bell jar equ ipment and Figure 8.4.1 The features of sound waves

• Amplitude is the distance air molecules move forwards and backwards. Louder sounds make air molecules vibrate with a greater amplitude. • The distance between two high-pressure areas is called the wavelength of a sound. Wavelength Movement of air particles from source of sound Figure 8.4.2 The air pressure changes caused by sound waves can be drawn as a wavy line

battery ...._____

pump out all air from the jar. Ring the electric be ll after the remova l of the air and note if you can hear the ringing. 2 Let some air back into the bell jar and again ring the bell. Note what happens this time. Figure 8.4.3

to a vacuum pump

Question: How d id the removal of a ir from the jar affect the sound of the ringing bell? Explain .

• Sound travels at 330 m per second, which is slower than the speed of light. The speed of sound increases as air temperature rises.


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The human ear When sound waves reach your ear, they are received by the outer ear and directed into your ear canal. sound waves

I

outer ear

I~I

Eustachian tube __ _ _ _ __ middle ear '--:inn-e-r-ea-r

• Outer ear-directs the sound waves through the ear canal. At the end of the ear canal is the eardrum, which vibrates when the sound waves strike it, transfering the energy to the middle ear. • Middle ear-has three bones (hammer, anvil ~nd stirrup) that vibrate and the energy mto the cochlea (a coiled tube) in the inner ear. • Inner ear-the movement of tiny hairs in the cochlea become nerve signals, which are transmitted via the auditory nerve to the auditory centre in the brain. Here the signals are interpreted as sounds.

~~

Figure 8.4.4 Parts of the human ear

Experiment: Pitch of sound Aim : To study factors that affect the pitch of sounds made by: 1 tuning forks, and 2 -test tubes containing different levels of water. Materials: 3 tuning forks of different lengths, a small hollow wooden block, 6 test tubes, a test tube rack, a piece of paper and 100 mL measuring cylinder with water.

Method: Part 1-Tuning forks 1 Strike each of the tuning forks on the wooden block. Hold the bottom of the fork on the block and hear the differences in the pitch . 2 Strike the forks harder and hear the change in the pitch. 3 Hold the Vibrating prongs of the tuning fork against a piece of paper and hear the change in the sound. Results: Part 1 Complete the table, saying what the pitch sounds like or what happens to it.

Method: Part 2-Test tubes 1

Place 6 test tubes in a test tube rack. Leave the first test tube empty and use it as a control. 2 Fill the other five test tubes with 5 mL, 10 mL, 15 mL, 20 mL and 25 mL water. 3 Blow across the tops of the test tubes and notice the change in the pitch as the level of the water increases. Results: Part 2 Rate each test tube according to the level of pitch, using the following scale: 1 if it is very high pitched and 6 if it is very low pitched .

Figure 8.4.5

Pitch Sound made by smaller tuning fork Sound made by medium-sized

Discussion: 1 What is the relationship between the length of the tuning fork and the pitch?

tuning fork Sound made by longer tuning fork Effect of hitting the tuning fork harder Effect of tuning fork on paper

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2 What is the effect of hitting the fork harder?

3 What is the effect of holding the ends of the vibrating prongs against a piece of paper?

4 What is the relationship between the pitch of the sound made by blowing over the test tube and the amount of water and air in the test tubes?

Conclusion: What is the similarity between the vibrating tuning forks and the test tubes with water?

2 Which factors affected the pitch : a in tuning forks?

More water and less air: b in test tubes with water?

Less water and more air:

Questions Questions 1-4 relate to the information in the t able. The speed of sound at sea level at different temperatures is given.

Speed of e;ound (m/e;)

330 336 342 348 354

6 Why are echoes greater in an empty hall than in one that contains an audience and curtains?

Air temperature ("G)

0 10 20 30 40

On graph paper, draw a graph of t he speed of sound against air temperature. Plot the speed of sound on the vertical axis. Start the vertical scale at 320 mls.

7

How do the musical instruments listed below produce sounds? a drum b guitar

c trumpet 8 Correctly place the following labels on the figure of the tuning fork: high pressure, low pressure,_air particle, wavelength.

2 What happens to the speed of sound as the temperature of air increases from O°C to 4UC?

3 What is the speed of sound at 20°C? Figure 8.4.6

4 What is the temperature of the air when the speed of sound is 350 m/s? 5

How could insect-eating bats use echoes to locate their food?

Science fact Dog whistles Dog whistles can be heard by dogs, but not humans. Humans can't hear sounds that are over 20 000 Hz. The sound made by dog whistles is above 20 000 Hz. Sounds with frequencies above the human range of hearing are called ultrasonic.


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137

Review and research Review questions Fill in the table to show the similarities and differences between heat, light and sound energy. Propertiee;

Heat energy

Light energy

Sound energy

Media required

Can be transmitted

Can be transmitted

Can be transmitted in

for transmission

through

through solids,

solids,

,

,

How it is

, gases

and vacuums

and

Conduction,

In the form of

transmitted

gases but not through

In the form of in a

and

,

waves

straight line

2 Why do potatoes cook more quickly in an oven if they have steel skewers pushed right

6 Why are concave mirrors also known as converging mirrors?

through them?

7 Why are convex mirrors also known as diverging mirrors?

3 State the laws of reflection for a plane

4

mirror.

8 State the theory of conservation of energy.

A ray of light has an angle of if1cide~_ce of

9 a Where is the elastic potentia l energy

60· and is reflected off a flat mirror. What is the angle of reflection?

5 a What is the nature of an image formed in a flat mirror?

b Why is this image called a virtual image?

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stored in this diagram? Explain .

b Where is the gravitational potential energy stored in this diagram'? Explain.

c

How many times louder is a noisy classroom than a quiet classroom'?

Project: Rubber band boat 10 Refer to the following table and answer the questions below.

Follow the diagram below to make a rubber band boat, Your teacher will give you a template to use. Use waterproof materials for your boat.

Sound levels of various sources Sound source

Sound level in decibels

US navy jet taking off from aircraft carrier

140

Domestic iet Elane at take off Jackhammer breaking reinforced concrete

120 110

Loud indoor rock concert Gravel truck carrying load Noisy vacuum cleaner

100

Interior of car moving at 90 km/h

75 70 65 60 50 40

Traffic in city Noisy classroom Ordinary conversation Quiet classroom Quiet suburban neighbourhood at night Soft whisper Rustle of tree leaves in a gentle breeze Normal breathing Threshold of hearing

place in this experiment,?

90 80

30 20 10 0

a What is the sound that' has a sound level ..... one-quarter the level of a noisy vacuum cleaner'?

For each 10 decibel (dB) increase of sound, loudness doubles, b How many times louder is a gravel truck than the traffic in a city'?

What types of energy transformations took

Research question Research how a kaleidoscope or a periscope works--use the library and Internet resources. Include a labelled diagram in your answer.

Word check Write the meanings of the following words in your notebook. Amplitude Kinetic energy Real image Conduction Law of Reflection reflection Convection Luminous Transparent objects Echoes Translucent Opaque Good conductor Pitch Vacuum Insulator Radiation Virtua l image

Mind map Re-draw the diagram (right) in your notebook, much larger. At the end of each line, write the name of one type of energy and two examples of where it is found. Elastic energy is done as an example.

Elastic energy 1. In a trampoline 2. In a rubber band


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139

CHAPTER 9: WEARING AWAY THE EARTH

Wearing away rocks Weathering The wearing away of rocks into smaller pieces is called weathering. There are three types of weathering: physical, chemical and biological.

times until part of the rock is split off. Clay-when soil particles are weathered they become very fine and form clay. As clay in the rocks gets wet, it expands and breaks the rocks apart.

Physical weathering

Chemical weathering

This is caused by non -living things such as water, wind and changes in temperature. Onion skin weathering (or spalling)-in desert areas the days are very hot and the nights are very cold. This daily heating and cooling affects the outside of rock and it can peel off like a layer of an onion. The rocks produced are round and are called tors. Ice wedging-when water freezes it takes up more space. When ice forms in a crack in a rock it pushes hard against the rock around it, makin~ the crack larger. This process is repeated many

Weathering caused by the action of chemicals. Natural acids-come from the decay of dead plants and animals, and gases such as carbon dioxide and sulfur dioxide. These dissolve in rain water and cause acid rain. These acids are weak acids and dissolve the rocks slowly. Limestone caves-when limestone rocks are dissolved by acids, caves form. Stalactites and stalagmites form when a solution containing limestone drips from the roof of the caves and evaporates. A stalactite grows down from the cave roof and a stalagmite grows up from the cave floor.

Biological weathering Water collects in a The ice forces the After many cycles crack in the rock and crack wider. The ice the crack is wider freezes at night. melts the next day. and deeper. Figure 9.1.1 How ice wedging cracks rocks

Experiment: Weathering Aim: To observe the effects of 1 heatin'g and cooling on a sandstone rock, and 2 acid s on limestone rocks. Materials: A 500 mL beaker, tap water, metal tongs, Bunsen burner, a small sandstone rock, safety glasses, a funnel, filter paper, a magnifYing glass, 4 test tubes, test tube stand, 4 pieces of limestone rock, vinegar, soda water, dilute hydrochloric acid and 10 mL measuring cylinder. Method:

Part 1-Physical weathering 1

140

Hold a small piece of a sandstone rock with metal tongs, and heat it in the blue flame of the Bunsen burner for about 30 seconds.

I


Weathering caused by living things. Tree roots-as tree roots grow, they exert a force that breaks rocks apart. Bacteria, fungi and worms-decompose dead organic matter, which becomes acidic and helps to break down rocks into soil. 2 Then dip the hot rock in a beaker of tap water. Repeat this process of heating and cooling at least three times. :3 Place a filter paper in a funnel and filter the water containing fragments of rocks. Remove the filter paper, allow it to dry and examine the fragments of rock using a magnifYing glass. Save the fragments for a later experiment.

~ ~-:r 1_ . ~pr--~~~~~-.

Figure 9.1 .2 Physical weathering of limestone

Resu lts: Part 1 Draw "the shape of "the rock before and after hea"ting.

Discussion: 1 What happened when a sandstone rock was heated and cooled suddenly?

2 What type of weathering is this? Explain . Method:

Part 2-Chemical weathering 1

Label 4 "tes"t "tubes A "to D and place "them in a "tes"t "tube s"tand. Place 4 pieces of limes"tone of similar size in"to "these "tes"t "tubes. 2 Pour 5 mL hydrochloric acid in"to "tes"t "tu be A. Pour 5 mL soda wa"ter in"to "tes"t "tu be B. Pour 5 mL vinegar Figure 9.1 .3 Chemica in"to "tes"t "tu be C. weathering of limestone Pour 5 mL "tap wa"ter in"to "tes"t "tube D. :3 Leave the limestone rocks for at least 10 minutes in "the tes"t tubes and observe the reaction. Record your results in the table. Results: Part 2 State whether there is a fast, a slow, or no reaction.

Test tube

Reaction with limestone

A Hydrochloric acid B Soda water

:3 Which test tube was used as a control? Why was it used?

4

How do you know that the limes"tone pieces reacted with acids?

Conclusion: 1 What type of weathering was caused when a rock was heated and cooled repeatedly?

2 What type of weathering resulted when the limestone rock was placed in different acids'?

C Vinegar D Water

Questions Wha"t causes the following types of weathering?

a physical

c

rocks changing into clay?

d stalactites and stalagmi"tes? e roots breaking rocks?

:3 Where do na"tural acids come from?

b chemical

c

biological

4 Why is ice-wedging not common in Queensland?

2 Which type of weathering causes:

a limes"tone caves? b round boulders called tors?

Wearing Away the Earth

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141

The effects of weathering Weathering affects buildings and roads in cities and towns as well as rocks.

Acid rain When gases such as carbon dioxide and sulfur dioxide that are released from factories dissolve in rain drops, acid rain is produced. It can dissolve limestone and marble statues and buildings. It can also hurt people's eyes, kill plants and make the water in lakes so acidic that fish and other aquatic organisms die.

Concrete cancer Many buildings, bridges and pavements are made of concrete, which is reinforced (made stronger) by steel inside it. When it is wet, the steel goes rusty and swells. This causes the outside of the concrete to peel off and weakens the strength of the concrete. This is called concrete cancer.

Erosion The carrying away of rock fragments is called erosion. The agents (causes) of erosion are wind, water, waves, ice and gravity. • Wind erosion-when the wind blows grains of sand and dust and deposits them great distances away. • Water erosion-when moving water washes away stones, sand and mud, and deposits them in rivers or in the sea. • Surf and ocean waves-remove sand from beaches and wash it along the coast or out to sea. • Ice erosion-occurs when ice in glaciers (frozen rivers) carves away earth and rocks and deposits them at the foot of mountains. • Gravity-causes landslides and soil creep, which happens when wet earth slips down a steep slope.

---.;;iiO-"~,--~_"1~+-- rusty steel reinforcement rust stai ns Figure 9.2.2 Landslips are common on steep farmland in wet areas

Deposition

Figure 9.2.1 Concrete cancer

Putting the rock fragments down in a different location is called deposition. The layers of rock fragments that have been deposited are called sediments.

Pollution

Sedimentation

The speed of weathering in buildings today is increasing because of pollution. Some famous buildings such as the Colosseum in Rome, the Parthenon in Athens and the Taj Mahal in Agra are all weathering faster now than ever before. The Pyramids built by the Egyptians have weathered due to wind-blown sand and changes in temperature, but acid rain and pollution are causing damage to these monuments as well.

As the flow of a river slows down, the river drops its sediments to the bottom. This process is called sedimentation. The bigger stones are dropped first, then gravel, pebbles, sand, and finally mud. The sediments that are dropped first would be at the bottom and form the oldest sediments. The newer sediments are deposited on top of these. When layers of sediments are compressed they form sedimentary rocks:

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Demonstration: Water erosion Aim: To simulate the role of water in caus ing erosion . Materials: Stream table, 500 mL beaker, stones, sand and water. Method: 1 Your teacher will set up the stream table near a sink. This is a large shallow tank, which is partly filled with sand and small stones. 2 Pour water from one end slowly and observe how it flows. The water simulates (copies) the action of a river.

Results: Draw the flow of the river as it goes down from its source.

Discussion: Wh ich moves furthe r: the large rocks or small grains'? 2 Does the river f low a straight path, or does it cu rve'? 3 Where does the most erosion take place'?

Conclusion: How does a river cause erosion'? Explain .

Figure 9.2.3 Using a stream table

Questions Explain what causes the following :

5 How do rock fragments settle as a river flows'?

a acid rain

b concrete cancer

6 Complete the table. Agents of erosion

Location of deposits'

Wind 2 Why are old build ings and monuments weathering faster than ever before'?

Water

Surf 3 What is erosion'? Ice 4 What are the agents of erosion'?

Gravity


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143

Landscapes caused by erosion River landscape

Coastal tract

Rivers produce their own landscapes. The movements of mud, water and stones create landforms which are only seen near rivers. The landscapes differ at the different stages, or tracts of a river. There are three types of river tract.

The river is slowest where the plain is flat. Here, only the mud and silt are carried by the river. The river is shallow and sandbanks form. As the river gets closer to the sea, the particles are smaller and more rounded, and finally they become mud and silt. This part of the river is said to be old, and is called the coastal tract.

Headwater tract When the slope is steep, the river flows quickly and carries big rock fragemnts. The rock fragments are freshly formed and have sharp corners and edges. This part of the river has Vshaped valleys. It is said to be young and is called the headwater tract.

Middle tract Where the slope is not steep, the river is slower. The river widens and erodes its banks. Because the water is moving slowly it deposits the large stones it is moving. These are deposited in gravel beds. This part of the river is said to be mature, and is called the middle tract.

Coastal landscape On the coast, erosion is caused by the surf and wind. It is the surf that erodes the beaches and sand dunes. In harbours and behind islands, wind blows loose sand into dunes, which may move inland to cover trees, roads and houses. Rocks that do not weather easily are harder than the surrounding rocks. Stacks, which are tiny islands left as the coast erodes, are often made of harder rock.

Figure 9.3.1 The three stages of a river

COASTAL TRACT old section of river

MIDDLE TRACT (Mature River)

HEADWATER TRACT (young River)

"'-/c::

ac

/V

~

\)'-V
J;gjJ ~~~ ~l:.J <7(j D.0

~_.A \/~ large angular - - - - - - - - - - + unsorted (all different sizes) - - - -

)JjUQ~

~9JYJO ~OR~J

j68Sg ~kg!

~~CAOc ~~~CC

Figure 9.3.2 Sizes and shapes of sediments in a river

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I


~C5~~(

----------+. small - - - - - - - - - - + . rounded - - - - - - - - - - + . sorted

Complete the following: Rivers produce their own When the slope is steep, the river flows valleys. It is said to be

. This part of the river forms

and is called the

tract.

When the slope is not steep, the river is is called the

. This part is said to be

and

tract.

Where the plain is called the

-shaped

, the river flows very slowly. This part is said to be

and is

tract.

On the coast, erosion is caused by the Stacks, which are tiny

and

left as the coast

, are made of

rocks.

Questions What is the main cause of erosion in river valleys'?

7 Can scooped up the rocks in the drawing from three places in the river. Which tract does each come from'?

2 Name the three main tracts of a flowing river and describe their features.

•

• Figure 9.3.3

• 3 What are the main agents of erosion in our

8 How is the size of a rock particle carried by a river related to the speed of the water'? Refer to figure 9.3.2. Headwater tract

coastal areas'?

4 Why do small sandy or muddy islands form

Middle tract

around the entrances of the river'?

Coastal tract 5 Which type of rocks are called stacks'? 9

How is the shape of rock particles in a river related to the distance they have travelled'?

6 Many people have built houses near the edge of beaches, but this is no longer allowed. Why'?


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145

Rocks made by erosion A river carries mud, tiny stones and gravel, as well as sand. These sediments are deposited at different places in the river, depending on the speed of the water.

Sedimentary rocks Fragments of rocks (sediments), which are cemented (glued) together naturally by chemicals in the ground, make rocks called sedimentary rocks. The process of making rocks is called lithification. The type of sedimentary rock formed depends on the size, origin and the shape of the sediment grains.

Clastic sedimentary rocks Most sedimentary rocks are from weathered rock fragments. These are called clastic rocks. Name of clastic rock

Sediment particle

Description of sediment

Conglomerate Breccia Sandstone Siltstone Mudstone Shale

Gravel Gravel Sand Silt Mud Clay

Rounded rock Angular rock Quartz sand Fine quartz sand Fine mud Splits into thin sheets

Chemical rocks Sedimentary rocks that are modified by some chemical changes are called chemical rocks. Examples include rock salt and gypsum. When shallow seas, bays or salt lakes dry up, the salt in the water crystallises and deposits of salt called halite or rock salt are formed.

Biological rocks Rocks made from the remains of living things are called biological rocks. Compacted shells and skeletons of marine organisms form limestone or chalk. • Shelly limestone is made from broken shells. • Coral limestone is made from corals. • Fossil rocks are made from the bodies of animals and plants that settle in the sediments. Fossils are the remains or impressions of living things that lived long ago and are preserved in sedimentary rocks. Usually only the hard parts of animals, such as the shells, bones and teeth, form into fossils. Fossils give us valuable clues about the evolution of organisms.

Figure 9.4.1 A A Conglomerate rock B Shale C Sandstone D Sun coral (limestone formed from dead coral)

D

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Experiment: Sedimentary rocks Aim: 1 to identify some sedimentary rocks and

2 to make a sedimentary rock. Materials: 4 samples of sedimentary rocks numbered but with no labels, a magnifying glass, protective eyewear, manila cardboard, masking tape, scissors, sodium th iosulfate, heat mat, Bunsen burner, a test tube, 200 mL beaker, water and tongs. Method: Part 1-ldentifying rocks 1 Observe the shape and consistency'of each rock with a magnifying glass. 2 Identify each rock and give a reason for your choice. Results: Part 1

Rock Name of the rock Reasons 1

5 The next day, peel the cardboard back from around the stone and note its appearance. 6 Place the rock in a beaker, pour some water on it and record what happens. Results: Part 2 Draw the shape of your sedimentary rock before and after pouring water on it.

Discussion:

Why are the rocks called sedimentary rocks?

2 Could you make a conglomerate rock using the method in part 2? If so, what materials

2

would you need?

3 4

Conclusion:

Method : Part 2-Making a sandstone 1

Make a small box using the shape shown as a template, from manila cardboard . Eaeh square should be 6 x 6 em. Seal the edges with masking tape. 2 Pour some damp or dry sand into the box. Figure 9.4.2 3 Place 10 cm depth of sodium thiosulfate (hypo) in a test tube. Gently heat it until the crystals dissolve, then heat for another 10 seconds on. low. heat. Do not boil the chemical. 4 Pour the chemical into the sand. Leave the box for at least a day to give the chemica l time to set properly.

Questions What are fossils? What can they tell us about evolution?

Summarise the differences between the four sedimentary rock samples.

2 Why was sodium thiosulfate used to make the sandstone?

3 What happened when you poured water over the sandstone? Explain.

2 Write a sentence that uses these words:

weathering, erosion, deposition, sedimentary rocks, sediments.


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Preventing erosion; soil composition Erosion costs many billions of dollars each year. It affects people in many ways and we need to take some preventive measures to control it. Causes of erosion Water and wind

Effects of erosion Water washes away valuable soil Sand dunes are blown away by wind

Overgrazing by cattle Cutting down trees

Removes ground covering and exposes soil Removes ground covering and increases salinity Animals cannot survive due to loss of habitat Dry top soil is blown away into ocean or cities Causes land degradation Crops cannot be grown due to lack of nutrients and salinity Farmers use more fertilisers to grow crops

Desertification Overfarming

Prevention of erosion Prevent run-off water by placing barriers and dams. Storm water drains and underground pipes must be used to carry waste water Restrict overgrazing and plant more grass Plant more trees, spray road cuttings with grass seeds and mulch

Plant more trees and ground cover Rotation of crops is needed Grow crops that introduce nitrates into the soil e.g. legumes have nitrogen fixing bacteria

Soil When rock fragments break down, they form soil, which provides the nutrients that plants need to grow, and holds them in the ground.

Soil profile Soil consists of many different layers. Each layer is called a soil horizon. A cross-section of the soil, with all the horizons, is called a soil profile. • Bottom layer-has unweathered rock and parent rock from which soil is formed. • Subsoil-consists of a layer of large rock pieces and a layer of small rock pieces. • Topsoil-consists of fine soil, humus and dead plant matter. • Humus-the remains of living things in the soil. • Ground water-lies in the tiny spaces between grains of sand and rock fragments. • Surface water lies above the ground in the form of pools, lakes and rivers. When the trees are cut down and removed, the ground water rises. The ground water has many salts dissolved in it, and when it evaporates, the salt remains behind and the soil becomes saline and no plants can grow.

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Figure 9.5.1 A soil profile, showing the different layers

Experiment: Soil composition Aim : To investigate how soil particles settle and form different layers of sedimentation. .Materials: soil mixture containing gravel, coarse sand, fine sand, clay and humus, 200 mL measuring cylinder, tap water and a ruler. Method: 1 Pour 100 mL water in the measuring cylinder. Add 20 mL of the soil mixture. 2 Mix the soil mixture thoroughly and set the cylinder undisturbed for 24 hours. 3 The next day, observe how different particles of the soil have settled down. 4 With a ruler measure the height of each layer and note in your results table. Results: Fill in the table and complete the diagram (with labels) to show the different layers. Soil profile Height Type of particles (cm)

Discussion: . Which type of particles settled at the bottom of the cylinder?

2 Which particles did not settle? Explain.

3 Which particles floated on top of the water?

4 Which particles settled on top of the pebbles?

5 What type of soil mixture did you test? Was it coarse, sandy or fine?

Humus Clay

Conclusion: What can you conclude from doing

Fine sand

this experiment?

Coarse sand Gravel Figure 9.5.2

Questions

2 a What causes the soil to become saline?

Write the preventive measures that can be taken to stop different types of erosion. .~ Cause of erosion Prevention

Desertification b Why is saline soil not desirable'?

Overgrazing

3 What is humus'?

4 What is the difference between a soil horizon Overfarming

and a soil profile?


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:3 Complete the table to compare and contrast the young river and the old river:

Match the following words with their meanings. Word

Meaning

Feature of river Answer

A Weathering

1 Carrying away of rock fragments 2 Ice freezing in B Spalling a crack in rock and forcing the crack larger C Ice wedging :3 Rock frag ments that have been deposited 4 Wearing away D Acid rain rocks 5 Saltiness E Erosion 6 Rain, snow, ice, F Sediments fog which is acidic 7 Onion skin G Salinity weathering, where the outside of rock peels off 2 Thea put a plastic bottle containing water in the freezer and later found that the bottle had split open.

Old river

Speed of water in river Size of stones in river Amount of saltiness Width of river valley 4 State which river tract the following groups of stones came from. Provide reasons for your answers. Group 1

Group 3

Reasons:

Group 1 stones

Group 2 stones

a Why did the bottle split open'?

Group 3 stones

b Explain how freezing water splitting a

5 The drawing below shows a natural rock formation. Explain (on the next page) the sequence of events from unweathered rocks to boulders.

bottle relates to freezing temperatures and the weathering of rocks.

150

Young river

I


:3 The following tombstones were found in a cemetery. Rank them in age from the oldest to the youngest (1 for the oldest, and 4 for the youngest) .

Thinking questions Ben and Mi-su have purchased a large block of land in the country that has a river flowing through it. They want to build a home near the river. Which location, A or B, is better'? Give an explanation.

Research questions Find out how stalactites and stalagmites are formed in limestone caves and submit your report on A4 paper. 2 Research what causes salinity of the soil and find out what can be done to prevent it.

Word check

2 Written in code below are the names of four common sedimentary roc~s. Each symbol stands for a different letter. Solve the code, then decode the message. It is a type of weathering. Four rocks

e*03$. TO_3$ . 0 _*.TO_3$ *o_ 71EeOO3$OOT 3$

~

Write the meanings of these words in your notebook. Acid rain Ground water Salinity Biological Humus Sediments weathering Chemical Ice wedging Sedimentary weathering rocks Concrete cancer Ice erosion Shale Soil horizon Conglomerate Limestone Coal Lithification Soil profile Coral limestone Mudstone Subsoi l Natural acids Topsoil Deposition Parent rock Desertification Water erosion Physica l Weathering Erosion weathering Rock salt Wind erosion Fossil

Mind map Draw a mind map in your notebook using the ideas in this chapter.

Secret Message

0 _ *0_. **_ . 3$0 T ~iE3$O*_,IE


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151

CHAPTER 10: OUR NEIGHBOURS IN SPACE

Ancient astronomy ~

Ancient astronomy

The Sun-centred model

People of many early civilisations, such as Egypt, Babylon, China and Greece, kept records of the positions of the Moon, Sun and planets. Australian Aborigines believed that the Milky Way was a river and the Sun was a woman who spread her warmth by wandering the sky. Astronomy (Astro = stars, nomy = arrangement) is the study of the Sun, Moon, planets and stars. Scientists who study astronomy are known as astronomers. The early astronomers had to make observations with the naked eye because telescopes were not available. A knowledge of astronomy was important for navigation, helping to predict the changing of the seasons, and determining the time to plant new crops.

• In 1512, Nicolaus Copernicus proposed thk Sun-centred model, which stated that the Earth and planets move around the Sun in fixed, circular paths called orbits. This model is also known as the heliocentric system (helio = sun). • In 1608, Hans Lippershey invented a simple telescope. In 1609, Galileo Galilei was the first person to use the telescope to observe the night sky. His observations ed the theory of Copernicus. He also discovered Jupiter's four largest moons. • In 1609, Johann Kepler ('Yo-ham Kep-ler') suggested that planets orbit the Sun in elliptical (oval shaped) orbits and not circular paths. • In 1667, Isaac Newton introduced the idea of gravity. He explained that the Sun, planets and their moons all attract each other with their gravity, and their speed stops them falling towards each other. This model is called the Newtonian model. • Uranus was discovered by William Herschel ('Her-shell') in 1782, Neptune was discovered by Johann Galle in 1846 and Pluto was discovered by Clyde Tombaugh in 1930. • Today the Sun-centred model of the solar system is accepted as true, along with Kepler's ideas that the planets orbit the Sun in elliptical paths and Newton's ideas about gravity.

The Earth-centred model • Ancient people believed that the Earth was flat, but in the fourth century BC Aristotle discovered that the Earth was round by watching the shape of the Earth's shadow as it ed over the Moon. • Ptolemy ('Tol-emmy') stated in 145 AD that the Earth is a sphere and that five planetsMercury, Venus, Mars, Jupiter and Saturnmove around it. This idea was called the Earth-centred model or Ptolemaic model. lnis iaea 'naa alreaay been suggestea by Pythagoras in 560 BC

Earth + Water Sun

Figure 10.1.1 Ptolemy's model of universe

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I


Figure 10.1.2 The Sun-centred model

Moves in elliptical, not round , orbit.

Complete the following: is the study of the Sun, Moon, planets and stars. Scientists who study astronomy are known as A knowledge of astronomy was important for changing of the

, helping to

, and determining the

the

to plant new

According to the Earth-centred model, the Sun,

and planets orbit around the

According to the Sun-centred model, the Earth, Moon and

orbit around the

was the first person to use a telescope in astronomy, and his observations ed the theory of

Questions

5 State the year and the astronomer who discovered the following planets.

Why was a knowledge of the night sky

a

important for the survival of early societies'?

Uranus:

b Neptune:

c Pluto: 6 a What attracts the Sun, the planets and their moons to each other'?

2 Who invented the telescope and who was the

b What stops them falling onto each other'?

first person to use it for astronomy,?

7 Name the model of the solar system in the diagram.

:3 Which model of the solar system is ed by modern astronomers'? *:

*:

*:

Stars

4 Complete the table to explain the various models of our solar system. Astronomical model

Explanation of the model

Ptolemaic model

Copernican model

Newtonian model

Our Neighbours in Space

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153

Our solar system Solar system

The planets are classified into two groups: the inner terrestrial planets and and outer gaseous

Our solar system consists of the Sun, nine planets and their moons, and millions of other objects such as asteroids, comets, meteors and meteorites. Our solar system lies in a spiral arm of the Milky Way galaxy. The diameter of our solar system is 12 billion km. The Sun is at the centre of our solar system and has enormous gravitational pull.

The four small rocky planets closest to the SunMercury, Venus, Earth and Mars-are the terrestrial planets. 'Terrestrial' means Earth-like. They orbit the Sun in almost circular orbits.

The Sun

Mercury

The Sun is a star (the closest star to Earth) and lies at the centre of the solar system. The Sun contains 99.8% of the total mass of the solar system. The more mass in an object, the greater the pull it has on other objects. Therefore all other objects in our solar system, including the Earth, orbit around the Sun. The Sun has a surface temperature of around 6000°C. The temperature at its core is 14 millionoC-so hot that nuclear explosions occur continuously, producing enormous amounts of energy. Without this energy, life could not exist on Earth.

• Distance from the Sun: 58 million km. It is the closest planet to the Sun. • Size: its diameter is 4880 km and it is 40% smaller than Earth. It is the second smallest planet. • One day: it takes 59 Earth days to rotate. • One year: it takes 88 Earth days to orbit the Sun. • Surface temperature: from 450°C on the side facing the Sun to -200°C on the night side. • Its surface is covered with mountains, craters, ridges and valleys. Meteorites do not burn up before they hit the surface because there is no atmosphere. • It is made mostly of iron and has a rocky layer. • It has no atmosphere. • Moons and rings: it has none.

/"\'~

__ Convection

/7~~1--

Radiation

::."~~~4 Nuclear reaction

planets.

Terrestrial planets or inner planets

Figure 10.2.1 The Sun's nuclear reactions provide the energy needed for life on Earth

What are planets? A planet is a body that orbits the Sun (or another star) and produces no light of its own. It reflects the light of the Sun or star. There are nine planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. None of the planets are perfect spheres-they all bulge at their equators, and are flattened at their north and south poles. Except for Earth, the planets are named after ancient Greek and Roman gods.

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Figure 10.2.2 Mercury, the closest planet to the Sun

Venus • Distance from the Sun: 108 million km. It is the second planet from the Sun, and Earth's closest neighbours. • Size: its diameter is 12104 km and it is slightly smaller than Earth. • One day: 243 Earth days. It rotates in the opposite direction to' that of Earth-the Sun rises in the west and sets in the east. • One year: 225 Earth days (its year is shorter than its day!) • Surface temperature: average is 482°C-the hottest planet. • Its surface is covered with volcanoes, large plains, mountains and craters. • Its closeness to the Sun means that water vapour is prevented from condensing into oceans. • It is the brightest object seen in the sky from Earth after the Sun and the Moon, and is referred to as the morning star or the evening star. The bright white light that can be seen is the reflection of sunlight off the clouds that cover the planet. • Its atmosphere is composed mostly of carbon dioxide-producing an enormous greenhouse effect. • Its air pressure is enough to crush many objects including spacecraft. • Moons and rings: it has none.

Figure 10.2.3 Venus was the first planet to be visited by a space probe

Earth • Distance from the Sun: 150 million km. It is the third planet from the Sun. • Size: its diameter is 12756 km wide and it is the fifth largest planet. • One day: 24 hours. • One year: 365 days. • Surface temperature: from -86°C to 60°C.

• 70% of its surface is covered with water. • Its atmosphere extends 80 km above its surface and consists of 78% nitroge~ oxygen, 1 % carbon dioxide and other gasesit has a stable greenhouse effect. • It is the only planet currently known to life. • Moons: one. Rings: none.

Figure 10.2.4 The Earth from space

Mars • Distance from the Sun: 228 million km. It is the fourth planet from the Sun. • Size: its diameter is 6794 km and it is half the size of Earth. • One day: 24 Earth hours and 40 minutes. • One year: 687 Earth days. • Surface temperature: from -73°C to 27°C. • It is commonly referred to as the 'red planet' because of iron in the soil forming a rusty dust. • It has the largest volcano in the solar system. It is called Olympus Mons. It is 3 times higher than Mt Everest. It is thought to be extinct. • It has weather with thin clouds, occasional dust storms and its polar ice caps consist of frozen carbon dioxide (dry ice). • It has a very thin atmosphere composed of around 95% carbon dioxide, and small traces of nitrogen, argon, oxygen and water. • Moons: two, called Phobos and Deimos. Rings: none.


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velocity winds that blow i opposite directions. • Its atmosphere is composed of 90% hy en and about 10% helium with traces of methane, water and ammonia. • Rings: has 3, measuring 29 km thick and 6400 km wide. • Moons: 28 discovered so far (16 are named plus 12 discovered recently but not yet named). The largest is Ganymede.

Figure 10.2.5 Mars, the 'Red Planet', has had several space probes lands on its surface

The asteroid belt Orbiting between Mars and Jupiter is the asteroid belt, composed mainly of asteroids that are rocky or metallic objects. The largest asteroid is Ceres, with a diameter of 914 km.

Outer planets Jupiter, Saturn, Uranus and Neptune are the outer planets and are composed of gases such as hydrogen and helium with solids (usually ice and rocks) at their core. These planets are referred to as the gas giants. All of the gas giants have rings. Pluto is the outermost planet and is composed of rock and ice.

Jupiter • Distance from the Sun: 778 million km. It is the fifth planet from the Sun. • Size: its diameter is 142 984 km and it is 11 times the size of Earth-the largest planet in the solar system. • One day: 10 Earth hours. • One year: 12 Earth years. • Cloud temperature: about -150°C. • Its surface is covered in violent storms with wind speeds of up to 600 km/h (because it rotates so fast). The Great Red Spot is a gigantic swirling, windy storm, over 40 000 km wide (3 times wider than Earth). • It has light and dark bands called the zones and belts. These bands are caused by high

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Figure 10.2.6 Jupiter, showing the Great Red Spot

Saturn • Distance from the Sun: 1430 million km. It is the sixth planet from the Sun. • Size: its diameter is 120 536 km and is the second largest planet in the solar system. • One day: 10 Earth hours and 40 minutes. • One year: 29.5 Earth years. • Cloud temperature: about -170°C. • About every 30 Earth years, following Saturn's summer, a massive storm occurs. It is known as the Great White Spot. • Its atmosphere consists of 97% hydrogen with helium, water, methane and ammonia making up the rest. • Rings: about 1.5 km thick and are divided into 3 main parts-the bright A and B rings and the dimmer C ring. The rings contain dust and large quantities of water frozen in various forms. • Moons: 21 (18 named, and 13 discovered recently but not yet named). Titan is Saturn's largest moon (it is larger than Mercury).

about the size of the Earth. It is the result of some of the fiercest winds in the solar system. Winds can reach 2000 km/h, more than 4 times faster than the fastest tornado on Earth. • Rings: has a set of 5 rings, which are narrow and very faint. They are composed of particles of dust and rock. • Moons: has 8-Triton is its largest. Figure 10.2.7 Saturn, showing its famous rings

Uranus • Distance from the Sun: 2871 million km. It is the seventh planet from the Sun. • Size: its diameter is 51800 km and is the third largest planet in the solar system. • One day: 15 Earth hours and 40 minutes. • One year: 84 Earth years. • Cloud temperature: on average -210°C. • Its pale blue-green colour is due to absorption of red light by methane in the upper atmosphere. • Its cloudy atmosphere is made of 83% hydrogen, 15% helium and small amounts of methane and hydrocarbons. • Rings: 11 known-they are very dark and composed of large particles of ice and dust. The brightest is known as the Epsilon ring. • Moons: 21.

Figure 10.2.8 Uranus appears as a fuzzy blue-green ball

Neptune • Distance from the Sun: 4504 million km. It is the eighth planet from the Sun. • Size: its diameter is 49 532 km and is the fourth largest planet in the solar system. • One day: 16 Earth hours. • One year: 164 Earth years. • Cloud temperature: on average -212°C. • Its blue colour is due to methane gas in its atmosphere. • It has several large dark spots-the largest is known as the Great Dark Spot, which is

Figure 10.2.9 Neptune appears blue flecked with white

Pluto • Distance from the Sun: 5914 million km-the furthest planet from the Sun. • Size: its diameter is 2274 km and is the smallest planet in the solar system. • One day: 6 Earth days. It rotates In the opposite direction to that of Earth. • One year: 250 Earth years. • Surface temperature: varies between -235°C and -210°C-the coldest planet. • Its composition is unknown, but its density indicates that it is probably a mixture of 70% rock and 30% water ice-similar to comets. • Its very thin atmosphere consists of nitrogen, carbon monoxide and methane. • It revolves around the Sun on a different plane to all the other planets. • Moons: one, called Charon. Rings: none.

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Figure 10.2.10 What Pluto might look like


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Activity: Modelling the solar system

Table 2

Aim: To model the solar system and simulate

Planet

Distance from model Sun

Mercury

0.58 m

Venus

1.08 m

Earth

1.50 m

Mars

2.28 m

Jupiter

7.78 m

Saturn

14.27 m

Uranus

28.70 m

Neptune

44.97 m

Pluto

59 m

the positions of the planets. Material6: Grains of white rice, 2 beads from a bean bag, black peppercorn, light bulb, billiard ball, 2 large glass marbles, sugar grains and a measuring tape. Method: 1 Table 1 shows the size of the planets when they are reduced in size by 200 million times. 2 Arrange the objects given to you in order of occurrence of the planets. Table 1

Planet

Model size

Object used

Mercury

2.1 mm

Half a grain of rice

Venus

5.3 mm

Bead from bean bag

Earth

5.5 mm

Bead from bean bag

Mars

3.0 mm

Small peppercorn

Jupiter

62.0 mm

Light bulb

Saturn

52.0 mm

Billiard ball

Uranus

24.2 mm

Large glass marble

Neptune

20.8 mm

Large glass marble

Pluto

1.0 mm

Grain of white sugar

3 Table 2 shows how far the planets are from the Sun when you shrink the solar system by 100 billion times. 4 Organise 10 students to be the Sun and the 9 planets and ask them to stand apart in the schoolyard at distances shown in table 2.

Re6ult6: Draw the planet models you used in order of their occurrence in the form of a chart. Or make a model using foam spheres of different sizes. Di6cu66ion: 1 Which planets are the smallest and largest?

2 Which planets are the closest and furthest from the Sun?

Conclu6ion: Summarise what the solar system

you modelled consisted of and name the planets in order of their occurrence from the Sun .

Figure 10.2.11

Questions

2 What is a planet?

1 What does our solar system consist of? 3 Which planets are known as: a terrestrial planets?

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b gas giants?

11 Complete the missing labels in the diagram below.

4 What is another name for Venus? Explain if it is an accurate name or not.

5 Which planet is known as the red planet? Why?

6 What is the red spot on Jupiter made of?

7 Arrange the planets from the smallest to the largest in size.

12 Fill in the table with the features of the planets.

Planet

8 Where is the asteroid belt? What is it composed of?

Distance from Sun (x million km)

Length of1 day (in Earth time)

Moons Rings Temperature

('G)

Mercury Venus Earth Mars

9 What is the name of the largest

Jupiter Saturn

asteroid? How big is it? Uranus Neptune

10 Name the planet that has a year that is shorter than its day.

Pluto


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How the Earth moves in space The Earth

Seasons

The Earth rotates (spins) as it orbits (revolves around) the Sun. One complete orbit takes 365.25 days or one year. As the Earth orbits the Sun, it spins like a top on its axis once every 23 hours and 56 minutes. The axis is an imaginary line running through the Earth from the north pole to the south pole. It revolves from west to east, in an elliptical orbit. This makes the Sun appear to rise in the east and set in the west.

The Earth also has an imaginary line around its middle, called the equator, which divides the Earth into the Northern and Southern hemispheres. The Earth is slightly tilted at 23.5 degrees as it orbits the Sun. The seasons are caused by this tilt. When the Southern hemisphere is tilted toward the Sun the sunlight is stronger because the sun is overhead, so it is warmer and experiences summer. At this time it Summer in Northern hemi is winter in the Northern uator hemisphere, because the sunlight is at an angle and is weaker. When the Northern hemisphere Winter in Southern has summer, the hemisphere Southern hemisphere has winter. Figure 10.3.1 The seasons

Day and night At any time, only half of the Earth is in sunlight. The other half is in shadow. The side facing the Sun has day while the side facing away from the Sun has night. For example when it is daytime in Australia it is nighttime in England.

result from the Earth's tilt

Activity: Simulating night and day and seasons Aim: fo simulate how night and day, one year and the seasons of the Earth occur. Materials: A globe of the Earth (or a balloon with the continents drawn on it with a felt pen), a torch, a lamp and a stool. Method:

Part 1-Day and night 1 Make your classroom as dark as possible, and shine a light from the torch onto the globe. fhis shows the Earth in night...and day. It is the daytime for the part of the Earth with the light sh ining on it, and it is night for the part of the Earth in shadow. 2 Rotate the globe so that dawn, then dusk, and then dawn again appear.

Figure 10.3.2 Simulating night and day

Walk around 'Sun'

Part 2-0ne year 1

Set a single lamp or a light bulb on a stool in the middle of the room to represent the Sun . 2 Hold the globe of the Earth, and walk around the lamp. fhis is the Earth going around the Sun . One circle or orbit is one year. fo be a reliable model, you should spin the Earth as it orbits the Sun . Count the number of spins the Earth makes for an orbit around the sun.

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Lamp on table

Figure 10.3.3 Simulating a year

Model Earth spinning on a string

Part 3 - The seasom!; 1

Since the Earth is tilted, hold your model Earth so that it is slightly tilted. Do not change th is tilt during the experiment. 2 Walk slowly in a circle around the lamp, moving the model Earth so that it always faces the lamp. Make sure the tilt always points in the same direction. :3 When you have walked half a circle around your Sun, stop and look at the model Earth. Notice the part of the Earth having summer.

Results: Draw the day and night model and the seasons model of the Earth on poster paper. Discussion: .

In which direction does the Earth spin'?

2 How many times does the Earth spin on its axis in one orbit'?

:3 How long does it take the Earth to orbit the Sun'? 4 When Australia has summer which part of the Earth is having winter'?

5 What causes the seasons'?

Conclusion: Explain what causes day and night Figure 10.3.4 Simulating seasons

Questions

and the seasons on Earth .

:3 Match the words with their explanations:

What are the mean ings of the words rotate

Word

Meaning

and orbit'?

A Length of day

1 Caused because the Sun can be overhead, or at an angle 2 The Earth

2 Use the motion of the Earth around the Sun

B Night

to explain why, for Austra lia, it is hotter in ,_ January than in July. C Season

. DYear

Am:; wer

spinning once every 24 hours. :3 Time for the earth to orbit the Sun once 4 On the part of of the Earth that is facing away from the Sun

4 What are the two imaginary lines used relating to the Earth spinning and Earth's hemispheres'?


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Time Historically, the regular motion of the Sun, the Earth and the Moon served as the basis for time keeping.

Sidereal time and solar time If a star is used as a reference point for time, it is termed sidereal time. If the Sun is used as a reference point, it is termed solar time. The solar day is about 4 minutes longer than the sidereal day.

Measurement of time • Sundials and water clocks-the earliest time measuring devices used the shadow cast by the Sun (sundials) or the rate of water running out of a vessel (water clocks). • Pendulum clocks-in 1665, Christian Huygens, a Dutch scientist, made the first pendulum clock. • Wind-up clocks and watches-some clocks and watches have a spring mechanism that is wound up to keep time. • Quartz crystal clocks-from the 1930s these replaced pendulum clocks. • Atomic clocks-in 1941 the first atomic clock was invented. Now time is measured in International atomic time.

Time zones • In the 1840s Greenwich standard time was established as the official time reference for the world. • In 1972 a new Coordinated universal time became effective. Coordinated universal time runs at the rate of the atomic clocks. • In 1884, the Earth was divided into time zones. The 24 standard meridians, lines every 15 degrees east and west of 0 degrees (at Greenwich, England) were designated the centres of the zones. • The international dateline was drawn to follow the 180 degree meridian in the Pacific Ocean.

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Active Science: .Skills & Experiments 1

Calendar A calendar is a way of recording time. Our calendar is made up of days, weeks, months and years. The day is the Earth's average rotational period (24 hours). The week consists of seven days. The month is linked to the period of the Moon's rotation around the Earth. Many ancient calendars were based on the lunar cycle. The lunar month is 29.530589 days. The most common scheme was to have 12 months of 30 days. The year is linked to the Earth's period of rotation around the Sun, which is 365.25 days. Our modern calendar is called the Gregorian calendar, after Pope Gregory XIII, who introduced it in 1582. Each year is given 365 days. Every fourth year, an extra day is added to the year, to accommodate the extra 0.25 days it takes for the Earth to orbit the Sun. A year with 366 days is called a leap year. In a leap year, February has 29 days. Dionysius Exiguus ('Di-on-ee-see-us Exidge-you-us') introduced the system of dating years. He called the year. that Jesus was born as year one Anno Domini (AD) or 'in the year of the Lord (Jesus)'. Any date before this was called Before Christ (BC).

Science Fact Stonehenge At Stonehenge in England over 4000 years ago, giant stone slabs were placed in a circle. Figure 10.4.1 Stonehenge The entrance stone aligns to the sunrise for the longest day in summer. Ancient people probably recorded the times and positions of the rising Sun and the Moon there. It was also thought to be a place of worship.

Activity: Making a sundial The sundial uses a shadow to show the time of the day. The most common sundial consists of a flat plate, which has the numbers for hours of the day written on it. The shadow stick or gnomon ('no-mon') casts a shadow on the plate. The time of the day is shown by the number that is closest to the edge of the shadow. Aim: To make a sundial. Materials: Stiff cardboard, thin cardboard, glue, scissors and a photocopy of the sundial template. Method: 1 Use the template given by your teacher to cut the baseplate of the sundial and glue it onto the stiff cardboard. 2 Cut out the gnomon and glue it onto the th inca rd boa rd. gnomon

3 Mount your sundial on a flat ground in a sunny position, pointing north- south as shown in figure 10.4.1. 4 Note where the shadow of gnomon falls at the following times: 10 am, 12 noon, 2 pm. Results: Draw the su ndial showing the shadow for 10 am, 12 noon and 2 pm.

'"

Discussion:

1 What is a gnomon?

plate

2 When would a sundial not be used for telling the time?

Conclusion: Explain how a sundial is used to

determine the time of the day.

Figure 10.4.2 The completed sundial

Questions Which calendar is currently used?

4 What is Greenwich standard time used for?

2 Why does our ca lendar have a leap year every 4th year?

5 What do the abbreviations BC and AD stand for?

6 What are 2 possible purposes of

:3 What is the difference between sidereal time

Stonehenge?

and solar time?


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The Moon Earth's moon

Phases of the Moon

• The Moon is the Earth's only natural satellite. A satellite is any object that moves in an orbit round a planet. • It is 384000 km from Earth and its diameter is 3476 km. It is one-quarter the width of Earth. • The Moon spins (rotates) once in exactly the time it takes to orbit the Earth (approximately 28 days), which means the same side of the Moon is always seen from Earth. This side is called the 'near side' and the opposite side is the 'far side'. • The Moon rises and sets, just like the Sun. It rises about 50 minutes later each day. The Moon is in the sky during the day as well as at night, but it is harder to see then. • The Moon has a weak gravity-one-sixth as strong as Earth's gravity. Gravity is the force of attraction an object has on another object. • Its mean temperature varies from -170°C to 130°e. The Moon has no atmosphere or weather, but may have some ice in craters near its north and south poles. • The Moon has been severely bombarded by meteorites, and its surface is scarred by about half a million craters. • The so-called ' Man in the Moon' is an illusion created by the appearance of the Moon's largest crater. • The Moon is covered with rocks, boulders and a layer of charcoal-coloured soil. Its crust is about 68 km thick. Below the crust is a mantle and a small core, about 340 km in radius.

The changes in the appearance of the Moon's shape are called the phases of the Moon. The Moon is always round and does not change its shape. What changes is the amount of the sunlit part of the Moon that we can see from the Earth. This depends on the positions of the Earth, Moon and Sun. Refer to figure 10.5.1 below for the phases of the Moon during one lunar month.

Tides

High tide

The oceans rise up and fall back again twice every day, due to the tide ~ tide Moon's gravitational pull. These water movements High are called the tides. As the tide Earth rotates it experiences Moon two cycles of high and low tides, roughly thirteen Figure 10.5.2 The bulges hours apart. of water on the Earth • High tides-the Moon's gravity causes a bulge of water on the side of the Earth closest to the Moon and another on the opposite side of the Earth. • Low tides-in between the bulges there is a lot less water and the tides are low. • Spring tides are extra large tides that occur twice a month when the Sun, Moon and Earth are lined up. The pull on the oceans due to gravity is stronger then. • Neap tides are small, weak tides that occur twice a month when the Sun, Moon and Earth are at right angles to one another. The Sun and Moon's gravity cancel each other out so the pull on the oceans is weaker.

LoW~lOW o

()O () New Moon start of lunar month

Crescent Moon (4 days)

First Quarter (7 days)

Gibbous Moon (10 days)

Figure 10.5.1 The phases of the Moon during one lunar month

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Full Moon (14 days)

Gibbous Moon (18 days)

Last Quarter (22 days)

Crescent Moon (26 days)

New Moon (29 days)

Activity: Modelling the phases of the moon Aim: To simulate the phases of the Moon. Materials: A table lamp, a stool, a basketball or a balloon representing the Moon.

Students holding basketball - - orballoon representing the Moon

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I

Method: , 1 Set up a table in the middle of the room as shown in figure Student Table lamp 10.5.3. Use a basketball or a representing as Sun the Earth balloon to represent the Moon. You are the Earth. Darken the Figure 10.5.3 Phases of Moon experiment room. 2 What is the order of the positions of the 2 Observe the part of the Moon that is in the Earth, Sun and Moon when it is light and the part of the Moon that is in shadow. a a Full Moon? :3 Observe what happens when the Moon is b a New Moon? between you and the Sun and the Earth is Conclusion: Summarise what causes the between the Moon and the Sun. Results: Draw the phases of the Moon from a different phases of the Moon . New Moon to a Full Moon and to the next New Moon on chart paper, including the pOSitions of the Earth, Moon and Sun. Discussion: What is the difference between a New Moon and a Full Moon?

Questions 1 What is a satellite?

2 What is meant by the phases of the Moon?

Science fact :3 How long does it take for the Moon to revolve and rotate around the Earth?

4 What causes high tides and low tides?

Man on the Moon Neil Armstrong and Edwin 'Buzz' Aldrin were the first humans to walk on the moon in July, 1969. In total 12 astronauts have now walked on the Moon. They have brought back about 200 samples of Moon rock.


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Solar and lunar eclipses How shadows are produced When you are out in the Sun, your body casts a shadow on the ground. When there are two lights, there will be two shadows. Where the shadows overlap and it is darkest it is called the umbra. Where there is a pale shadow it is called the penumbra, which is only a partial shadow.

totally dark. This can be seen only from a small part of the Earth, in a band 250 km wide. Outside this band, a partial solar eclipse is seen, where only part of the Sun is covered. The sky does not become completely dark, because that part of the Earth is only in penumbra. Caution: Do not look at the sun directly even

when it is blocked during solar eclipse, because it will seriously damage your eyes.

Lunar eclipse

Figure 10.6.1 How an umbra and a penumbra are formed

Eclipses An eclipse occurs when the Earth or Moon moves into a shadow and appears dark instead of being lit by the Sun. The shadow could be an umbra or a penumbra.

Solar eclipse Solar refers to the Sun. A solar eclipse is an eclipse of the Sun. This happens when the Sun is blocked by the Moon. A solar eclipse can be only seen in the daytime. A total solar eclipse happens when a section of the Earth is in the umbra and the sky becomes

Lunar refers to the Moon. A lunar eclipse is an eclipse of the Moon. It can only happen at Full Moon, when the Moon is in line with the Earth. The shadow of the Earth moves across the Moon so the Moon appears darker. Lunar eclipses usually happen once or twice a year. They can be easily seen, but only from the half of the Earth which is in darkness (night). The Moon might move into the Earth's umbra causing a total lunar eclipse or into its penumbra causing a partial lunar eclipse.

Beliefs about eClipses • The ancient Chinese thought that a dragon was trying to swallow the Sun. • The Vikings thought two wolves chased the Sun and Moon. • South American Indians thought a puma devoured the Sun. To frighten away the puma, children used to scream.

b! I

Figure 10.6.2 a. How a lunar eclipse occurs b. How a solar eclipse occurs

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Activity: Solar and lunar eclipses

Lunar eclipse:

Aim: To simulate and investigate solar and

lunar eclipses. Materials: A globe of the Earth on a stand, electric lamp, a small ball and a piece of string.

Method : Part 1-Solar eclipse 1 Tie a string around the ball to represent the Moon. 2 Place the lamp and globe in a line and hold the ball in between the two. The lamp represehts the Sun. 3 Darken the room and observe the shadow cast on the globe.

Part 2-Lunar eclipse 4 Place the globe between the lamp and the ball. Observe the shadow produced on the ball. This represents a total lunar eclipse. 5 Move the globe so that it covers the lamp partially to model a partial lunar eclipse. Results: Draw the solar and lunar eclipses you created.

Discussion and Conclusion:

What caused the solar eclipse in the activity?

2 What caused the lunar eclipse in the demonstration?

3 Did you observe umbra (dark) and penumbra (light) shadows?

Solar eclipse:

4 How was the partial lunar eclipse modelled?

Questions What do the words lunar and solar refer t S(? 4 What is the difference between a solar 2 What is an eclipse?

eclipse and a lunar eclipse?

.' 3 Explain the difference between an umbra and •

..-~

i

a penumbra.


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Constellations Constellations Constellations are names for groups of stars that appear to form shapes in the sky. Astron0mers recognise 88 constellations covering both the Northern and Southern hemispheres. The concept of the constellations of the zodiac originated in Mesopotamia, and the idea spread with few changes through Greece, Rome, the Islamic empire, and from Europe to India.

second. Once every 24 hours the Southern Cross and other constellations appear to move from east to west around a point in the night sky called the South Celestial Pole (S). This apparent movement is caused by the Earth's rotation on its axis, which extends out in an imaginary line to the S. The point on the horizon immediately underneath the S gives the direction to the Earth's south pole.

Zodiac constellations

Other famous constellations

The word zodiac comes from Greek, meaning figures of animals. The zodiac is the belt of stars in the path of the Sun. It is divided into twelve groups of stars, or constellations, imagined to represent animals and mythical figures. The twelve zodiac constellations are: Sagittarius, Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra and Scorpio.

The Southern Cross The Southern Cross or Crux Australis is a major constellation in the sky of the Southern hemisphere. It consists of 5 stars-Alpha Crucis is the brightest star among them. It is directly above the S, and there are two stars, known as the Pointers, that point to the Southern Cross. Australia and New Zealand have versions of the Southern Cross in their national flags.

Figure 10.7.1 The Earth moves around Sun against background of stars

Figure 10.7.2 The Southern Cross appears to move in a clockwise direction about the so

The Sun, Moon and planets were observed to move in relation to the fixed background of twelve zodiac constellations, which form an imaginary belt in the sky. At any given time of the year, the Sun is between Earth and one of these constellations. Your astronomical constellation (or star sign) is the constellation of the zodiac that is behind the Sun on your birthday.

Orion This constellation represents Orion-a hunter from Greek mythology-holding his club and shield, and with a sword dangling from his belt. The belt is three bright stars in a row. The two brightest stars in Orion are Betelgeuse (his shoulder) and Rigel (his foot).

Do constellations move?

Canis major Canis major represents one of Orion's hunting dogs. It is found near Orion and contains Sirius, the brightest star in the sky.

Stars and constellations are not fixed in their positions but move with speeds of many km per

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Activity: Model of tire zodiac constellations Aim: To simulate the position of the Earth against the constellations of the zodiac during different times of the year. Materials: A photocopy of two strips showing the constellations of the zodiac, glue, yellow plasticine, blue plasticine and 2 paper clips. Method: 1 Cut the two strips showing the constellations of the zodiac and glue them into a circle (make sure the correct ends are ed to each other-Scorpio and Sagittarius should be next to each other). The constellations should be on the inside of the circle as shown in the figure. 2 Using two paper clips and two pieces of plasticine, make models of the Sun and the Earth. Use yellow for the Sun and blue for Earth. 3 Move the Earth slowly around the Sun and notice which constellation it is facing. The section of the strip with the month shows the time of the year when the constellation is overhead in the middle of the night in Australia.

Results: Draw the diagram of the zodiac constellation on which your birthday falls. Discussion: 1 What is a constellation?

2 Explain why we can't see Virgo in March from Australia .

3 Explain why we are able to see different constellations at different times of the year.

4

How accurately does the model show the distance between the Sun and Earth?

5 Why can't you see the Southern Cross on this strip?

Conclusion: What is the zodiac?

Figure 10.7.3 The Sun and Earth with constellations of the

Gemini

Cancer

June

July

Virgo

Leo

August

Libra

~diac

Scorpio

Sagittarius Capricorn

Aquarius Pisces

September October November December January February

March

Aries Taurus

April

May

Figure 10.7.4 The zodiac

Questions

fixed in space?

1 What is a constellation?

2 Do stars and constellations move or are they


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Review and research Review questions Questions 1 to 9 are multiple choice questions. Circle the best alternative. The study of astronomy is a predicting the future. b dealing with the Earth. c studying extinct animals. d studying stars, planets and space. 2 Venus is sometimes called the evening star. This is misleading because a Venus is not a star. b Venus does not appear in the evening. c Mercury is the evening star. d Venus can only be seen with a telescope. D The correct date order for thyse famous astronomers, from earliest to latest, is: a Ptolemy, Galileo, Copernicus, Newton. b Ptolemy, Galileo, Newton, Copernicus. c Ptolemy, Copernicus, Galileo, Newton. d Newton, Galileo, Copernicus, Ptolemy. 4 Night and day is best explained by a the Moon blocking out the light from the Sun. b the Sun rotating on its axis. c the rotation of the Earth on its axis. d the tilting of the Earth as it spins. 5 The seasons are caused by a the extremely large size of the solar system. b the distance from the Earth to the Sun. c _the tilt of the Earth as it go~s around the Sun. d the spinning motion of the Earth. 6 The Earth's natural satellite is called: a Aussat. b the space shuttle. c the Moon . d a comet. 7 Eclipses are caused by a the Moon and the Earth moving into each other's shadow. b the large size of the Sun and Moon. c the enormous distances in space. d the very strong gravity of the Sun.

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8 The hottest planet is a Jupiter. b Venus. c Mars. d Saturn. 9 The purpose of a leap year is to a keep the calendars and seasons in sequence over the centuries. b ensure that the same event does not always fall on the same day. c allow enough time every year for the Earth to rotate around the Sun. d allow sundials to record accurate time year after yea r. 10 Each of the statements below is incorrect. Change the bolded word to make the sentence correct. a The Sun is at the centre of the universe

b Venus

is the closest planet

to the Sun. c The Earth orbits

once every

24 hours. d A solar

eclipse is when the

Moon is darkened.

e Jupiter

is the planet with

visible rings around it.

f

There are twelve

planets in our

solar system. 11 Name the planet that a is the second largest: b is the second smallest:

c is closest to Earth: d is furthest from Earth: e has the shortest day:

f

has the longest day:

g has the moon called Phobos: h has the Great White Spot:

11 Use this diagram to help you answer the questions below.

Thinking questions This illustration shows how the seasons occur. Answer A or B to each question. A

@] 9

B

a Which gives the more spread out light?

a Name the planets in alphabetical order.

b Which diagram represents summer? 2 The following diagram shows Australia on the side of Earth . In relation to Austra lia, a is it night or day?

b Name the planets in order of their number of moors (use the diagram as a guide). _

b is it summer or winter?

===:::::::-::>-

c Name the planets in order of their size (use the diagram as a guide).

Sun's rays

==:::::::::-::>-

Research question d How are Saturn and Ura nus different to each other?

Prepare a space travel tourist brochure advertising the attractions of a planet of your choice. Promote your travel brochure to the class in an oral presentation for 5 minutes.

e Which planet does not revolve in the same plane as the other planets?

12 If the Earth stopped spinning would there still be day and night? Explain.

Word check Write the meanings of the following your notebook. Astronomy Navigation Atmosphere Orbit Constellation Penumbra Gnomon Phase of the Gas giants moon Lunar eclipse Revolution Moon Rotation

words in Satellite Solar system Solar eclipse Sundial Terrestrial planets Umbra Zodiac

Mind map Draw a mind map of the solar system in your notebook.


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Glossary acid rain

assimilation

When gases such as sulfur dioxide and nitrogen dioxide dissolve in rainwater they form acids that can dissolve marble and limestone and affect plant growth.

Making use of digested and absorbed food materials for growth, repair and reproduction by a living organism.

activated charcoal

Between Mars and Jupiter, hundreds of large rocks are found in the asteroid belt. These are thought to have formed when a meteor hit a planet.

Charcoal that has been steamed or heated in a certain way will attract or adsorb certain substances. It is used in many factories to remove impurities. The impurities stick onto the outside of the tiny grains of carbon.

adsorption

asteroid

astrology The study of the influence of stars on our daily life.

astronaut

The temporary bonding of a chemical substance to the surface of another substance, such as activated charcoal, is called adsorption.

A space scientist who travels to different places in space.

astronomer

aerosol can

A scientist who studies astronomy.

A can containing gas at high pressure. There is a lot of gas compressed in the can. The valve on top is like a gate that lets the particles out. When you release the valve, some gas particles are pushed out by the other particles.

The scientific study of the stars, planets and their movement.

air pressure

The layer of gases surrounding the Earth or other pl?nets.

astronomy

atmosphere

Pressure exerted by air. Air pressure decreases as the altitude increases, as there is less air at higher altitudes.

auditory centre

air resistance

The centre in the brain that receives messages from the ear, via the auditory nerve.

The friction between a moving object and the air it is moving through. Air resistance is also called drag.

auditory nerve

amber

The nerve that carries impulses from the ear to the auditory centre in the brain.

A yellow-brown fossil resin made of the sticky liquid that comes out of certain plants. It is commonly used for jewellery. When rubbed against a material it acquires an electrical charge.

amplitude The distance air molecules move forwards and backwards. Louder sounds make air molecules vibrate with a greater amplitude.

angle of incidence The angle between the incident ray and the normal.

angle of reflection The angle between the reflected ray and the normal.

antibiotic A substance obtained from moulds that destroy the growth of disease causing bacteria and fungi. Penicillin and streptomycin are common antibiotics.

anvil

aurora The bright light seen in the night sky occurring most frequently near the Earth's geomagnetic poles. It is caused by the interaction of atoms of oxygen with charged particles streaming from the sun, attracted to the poles by the 'Earth's magnetic field.

autotrophs Organisms like plants that can make their own food by photosynthesis.

backbone A flexible column made up of vertebrae from the skull to the pelvis. The spinal cord runs inside the backbone. It is also called the spine, spinal column or vertebral column.

bacteria Unicellular, microscopic organisms that do not contain membrane bound nucleus. Some bacteria are useful and some cause disease.

One of the three bones in the middle ear.

bar graph

apparatus

A graph that is drawn with horizontal columns to show the relationship between two variables.

Any equipment instrument or machine used to carry out science experiments.

172


bel

cell division

The unit used to measure loudness of sound, named after the inventor Alexander Graham Bell. The unit usually used is decibel (dB) which is one tenth of a bel (B).

Splitting of a cell into two cells by a process called mitosis.

benign tumour A group of cells formed by the repeated division of normal cells. They do not spread to other tissues and are not normally fatal unless they grow in a vital organ such as the brain.

binomial name or nomenclature A two-part naming system developed by Carl Linnaeus. The first part of the name specifies the genus name and the second part specifies the species name-Homo sapiens is the binomial name for humans.

cell membrane The outer layer of a cell, which is made up of proteins and a phospholipid bilayer.

cell organelles Small membrane-bound organs, such as mitochondria and chloroplasts, found in cells.

cell specialisation The process where different groups of cells are specialised to perform different specific functions in multicellular organisms.

cell theory

biological rocks

Theory stating that all living things are composed of one or more cells or cell fragments; that the cell is an organism's' basic unit of structure and function; and that all cells arise from other cells.

Rocks made from the remains of living things. Compacted shells and skeletons of marine organisms form limestone or chalk.

A wall that s and protects a plant cell. It is made of cellulose.

biochemical weathering Erosion caused by chemicals produced by living organisms.

biological weathering The weathering of rocks caused by the action of living organisms, such as tree roots, bacteria and fungi.

biologist A scientist who studies Biology.

biology The scientific study of all living organisms, including plants, animals and microorganisms.

breeds Within the same species there are many types of organisms called breeds. For example many breeds of cats and dogs exist.

Bunsen burner

cell wall

cellular respiration When glucose is oxidised by oxygen to produce carbon dioxide, water and energy.

Celsius Temperature is measured in degrees Celsius (0C) using a thermometer.

centrifuge A machine or device that contains test tubes that spin quickly to separate particles of different densities. The heavier substances settle at the bottom of the test tubes.

centrifuging The process of separating solids and liquids using a centrifuge.

A gas burner used in a laboratory to heat substances.

chemical change

calendar

In this type of change, new substances are formed and the process is often difficult to reverse . Different types of particles regroup or rearrange themselves to form new substances.

A way of recording time. Our calendar is based on days, weeks, months and years.

cancer A disease caused by the multiplication of an abnormal cell. The cells continue to multiply, forming a ball of cells called a tumour that grows rapidly, invading and damaging vital organs.

carcinogen Substances, such as smoke in a cigarette, UV rays, and some chemicals, that produce cancer.

cavity slide A microscope slide that has a depression to hold organisms in a drop of water.

cell

chemical energy Energy stored in fuels, food and batteries.

chemical rocks Sedimentary rocks that are modified by chemical changes are called chemical rocks. Examples include rock salt and gypsum.

chemical weathering Erosion caused by pollutants in air and water. Acid rain can erode buildings constructed with limestone or marble.

chemist A scientist who studies chemistry.

The basic functional unit of all living organisms.

Glossary

173

chemistry

compound microscope

The scientific study of matter, its properties and how to change them.

A light microscope that has one eyepiece lens and one objective lens. Each lens is at the end of a tube that can be moved up and down. It can magnify an object approximately one thousand times.

chlorophyll A green pigment found in chloroplasts that is responsible for absorption of light energy in the process called photosynthesis.

chloroplasts Organelles in plant cells that contain chlorophyll and perform photosynthesis.

chordates A phylum of animals that have a hollow dorsal nerve cord and a flexible skeletal rod (notochord) . Vertebrates (animals with a back bone) belong to this phylum.

chromatography The separation of coloured substances or soluble dyes.

classification A method of sorting living things into different groups according to similarities in their characteristics.

clastic sedimentary rocks Sedimentary rocks that are composed of weathered rock fragments . Examples are sandstone and mudstone .

clay The finest particle of soil, which forms shale-a sedimentary rock.

coal Produced when organic matter such as wood is heated. It is used as a fuel.

coastal tract The area of a river close to the coastal region.

compressibility Squashiness-when the particles of a substance can be compressed (pushed closer together). Gases are more compressible than solids because their particles are further apart.

concave mirror A mirror that is curved inwards. Also known as converging mirrors because the reflected rays meet at a focal point (converge).

concentration The amount of solute (a solid) dissolved in a volume of solvent (a liquid) . If more solute is dissolved in the same volume of the solvent, the solution is said to be concentrated.

concrete cancer Many bridges, buildings and pavements are made of concrete, which is reinforced by steel inside it. Sometimes this steel goes rusty and swells, causing the outside of the concrete to peel off. This is called concrete cancer.

condensation A process where a gas or vapour changes back to a liquid state.

conducting vessels Special vessels that transport water and nutrients. For example, xylem vessels carry water and ions and phloem vessels carry nutrients. Flowering plants and gymnosperms have conducting vessels.

cochlea

conduction

A coiled tube in the inner ear filled with fluid that aids hearing.

Heat energy is ed from one particle to another in solids by conduction. Heat is conducted from a hotter object to a cooler object.

colloids Mixtures containing tiny particles, which are evenly distribut'e d and do not settle to the bottom of a container. The particles can through filter paper.

conglomerate A sedimentary rock made up of gravel and larger pieces of rock cemented together.

column graph

constellation

A type of histogram that shows information in the form of vertical columns.

A group of stars that appear to form a pattern of an animal or object. There are 12 constellations in the zodiac.

com

control

An instrument used to navigate one's way. Its north pole

always points to Earth's magnetic north pole.

The part of a scientific experiment that acts as a standard by which to compare experimental observations.

compound

controlled experiments

A substance that is formed during a chemical reaction between two or more elements. Its properties are different from the properties of the original elements and it cannot be separated by physical means.

Experiments where all conditions are kept constant, except the variable being tested.

174


convection The transfer of heat energy in liquids and gases caused by differences in temperature within them.

convection currents

desalination

Caused by the movements of heated particles in liquids and gases. Hot particles rise through the colder liquid and colder, denser liquid sinks to take their place. These colder particles are then heated and they rise, and the process continues.

Removal of salt from watCl ur soil.

converging mirror

desertification The gradual conversion of fertile land into a desert, usually as a result of human activities such as deforestation, overgrazing and bad management of farmland.

A concave mirror is also known as a converging mirror because the reflected rays meet (converge) at a point.

diagram

convex mirror

In science: a diagram is a simple line drawing of apparatus used in a laboratory.

A mirror that is curved outwards. Also called diverging mirrors because the reflected rays move away from each other (diverge).

diffusion The process of movement of particles from a region of higher concentration to a region of lower concentration.

coral limestone Limestone made from corals.

dilution

cover slip

When more water is added to a solution, it becomes diluted-it has less solute and more solvent.

A thin piece of glass used to cover a specimen on a slide.

crystal A crystal is a solid that has different particle arrangements, shapes and colours. Copper (II) sulfate crystals are blue and diamond shaped.

crystallisation The process of forming crystals from a liquid as it cools or evaporates.

cyanobacteria Also known as blue green algae. They are photosynthetic bacteria that possess a pigment called phycocyanin.

cytoplasm A jelly-like liquid found within the cell in which cell organelles are found.

data Information that has been collected during an experiment. It can be presented in the form of a table or a graph so that it is easy to understand.

data points The points on a line graph that are ed by a line.

decanting The process of separating a liquid from a settled solid suspension by carefully pouring it into a different container.

dissecting microscope A microscope that has a separate set of lenses for each eye, so you can see the object in three dimensions (3D). It can be used when dissecting small objects.

distillate The solution collected after the process of distillation.

distillation The process in which a solution is boiled, and the steam is collected. The steam is then cooled and turned back into liquid.

diverging mirror A convex mirror is also known as a diverging mirror because the reflected rays bend away from each other (diverge).

division In biology: the plant kingdom is divided into different groups called divisions: algae, bryophytes, ferns, gymnosperms and angiosperms.

DNA (Deoxyribonucleic acid) Chromosomes and genes in the cell nucleus contain a genetic material called DNA. It controls hereditary characteristics and protein synthesis. It is made up of two chains of nucleotides that wind to form a spiral shaped ladder.

decibel

domains

A unit used to measure the intensity or loudness of sound. It is one tenth of a bel. Symbol: dB

Tiny magnetic crystals inside magnets

density

When magnets are being made, the magnetic domains are all forced to face the same direction. When the metal solidifies, the magnetic domains are frozen in this position.

The mass of a substance per unit of volume. It depends on the number and heaviness of particles in a given space or volume.

deposition The laying down of materials transported by water, wind or glaciers.

domain theory

double graph When the same graph has two different lines or sets of columns, it is called a double graph. It is used to compare data.

Glossary

175

drag

electron microscope

The opposing force caused by air resistance.

A microscope that uses a beam of electrons instead of a beam of light to form a large image of a very small object.

ear canal Found in the middle ear. It receives sound waves from the outer ear and transports them to the inner ear.

eardrum A thin membrane that covers the ear canal. It vibrates when the sound waves hit it and these vibrations are conducted into the inner ear.

electroscope Is an instrument used to detect static electric charges on an object.

electrostatic separation A method of separating solids from a mixture by using electrostatically charged rods.

Earth-centred model

electrostatic separators

The model where Earth is the centre of the universe with the Sun and planets revolving around the Earth.

Electrostatic separators divide minerals of different electrical properties based on the fact that like charges repel and unlike charges attract. They are used to separate valuable minerals, such as zircon, from beach sands.

Earth's magnetic field The magnetic field exerted by the Earth is similar to the magnetic field exerted by a powerful magnet.

echinoderm Spiny skinned organisms such as starfish, sea urchins and sea cucumbers belong to the phylum Echinodermata.

echoes The effect produced by the reflection of sound from a solid surface.

electrostatics The study of electric charges at rest, the forces between them and the electric fields associated with them.

element A naturally occurring, pure substance that cannot be decomposed into Simpler substances. There are 92 naturally occurring elements.

emulsion

eclipse The total or partial obscuring of light from the Sun by either the Moon or the Earth.·A lunar eclipse occurs when the Earth comes between the Sun and the Moon, so that the shadow of the Earth falls on the Moon. A solar eclipse occurs when the shadow of the Moon falls on the Earth.

ecologist A scientist who studies ecology.

A creamy liquid in which particles of oil are evenly distributed.

endotherm An animal whose body temperature is constant and is independent of the temperature of its external environment. They produce heat by metabolic activity. Birds and mammals are known as endothermic or homeothermic.

energy

ecology The scientific study of how plants and animals interact with each other and their environment.

ectotherm An animal whose body temperature is not constant but fluctuates with its environmental temperature. Fish, amphibians and reptiles are ectothermic or poikilothermic animals.

The ability to do work. It is measured in joules (symbol: J).

energy change Energy exists mainly in two forms: potential energy and kinetic energy. Energy can change from one form to another.

energy transformation When one form of energy changes to another. For example, electrical energy can change into light or heat energy.

elastic energy

engulfing

Stored energy in stretched objects. When you bounce up and down on a trampoline the elastic energy in the trampoline pushes you upwards.

The process where an organism folds its cell membrane around another organism in order to feed on it.

electrical energy

The name given to commonly used apparatus, such as beakers and test tubes, in the laboratory.

The flow of electrons in the conductors and circuits in appliances such as TV, radio and computers.

electromagnet A temporary magnet created by wrapping an iron nail with a piece of wire and ing electricity through the wire. As long as the current es through the wire, the nail is magnetic.

electron Negatively charged particles found in all atoms and ions. They orbit around the nucleus of an atom in electron shells. 176


equipment or apparatus

erosion The wearing away of the land surface by natural agents such as water, ice, wind, organisms and gravity. The soil or the rock debris is moved and deposited in a different place.

euglena A unicellular organism that has both the characteristics of Autotrophs and Heterotrophs. It contains chlorophyll and can photosynthesise. It can also engulf other smaller organisms.

evaporation The change in state of a liquid into a vapour at a temperature below its boiling point. Spilt petrol evaporates quickly.

exoskeleton A skeleton outside the body. Insects have them-they are shed and new ones grown as the insect matures.

expand To become larger after being heated. Solids, liquids and gases expand after heating because their particles vibrate and move faster. When cooled they contract.

eye piece (ocular) The lens that is nearest to the eye. It magnifies the object on the slide many times.

fair test A test that is fair and can be answered by people belonging to any race or culture.

N). One newton is equal to the weight force of 100 grams.

fossil The remains or impressions of living things that lived long ago that are preserved in sedimentary rocks. Usually only the hard parts of animals, such as shells, bones and teeth, form fossils.

fractional distillation Fractional distillation is a type of distillation that separates liquids that are mixed together. Crude oil is a mixture of chemicals such as petrol, tar, oil, dissolved gases and kerosene. Each liquid in the crude oil mixture has a different boiling point, which is used to separate the chemicals. The separation occurs in a fractionating column.

free electrons Electrons that flow in a circuit.

freezing When a liquid is changed to a solid state by cooling.

ferrites

frequency

Magnetic materials that contain iron, oxygen and other elements.

Frequency can be the number of cycles of a sound wave, or the number of vibrations per second. It is measured in hertz (symbol: Hz).

ferromagnetism The magnetic property of materials containing iron is called ferromagnetism. Ferrum is the Latin name for iron.

fertile offspring A second generation of organisms that are able to reproduce. Organisms that belong to the same species produce fertile offspring.

filtrate The clear liquid obtained by filtration.

filtration The process of separating solid particles from a liquid or a gas.

fission In biology: the division of a cell into two or more parts. Bacteria divide into two by binary fission. In physics: when an atom is split and energy is released from the nucleus.

flagellum A long, fine, whip-like structure present on the surface of some cells, which helps the movement of the cell or the organism in a liquid medium. Sperms, bacteria and some Protozoans have flagella.

friction The force produced when objects rub together. It is a pushing force that slows or stops everything that is moving.

froth floatation A method of separating a mixture of solids when separating ores from unwanted impurities.

fungi This kingdom consists of organisms that look like plants but cannot make their own food. They can live in the dark and obtain nutrients from dead organic matter (decomposers). Some fungi cause diseases in plants and animals. Mushrooms and toadstools are examples of fungi.

gas A state of matter that possesses particles that that are free to move about with no forces holding them together. Gases have no definite shape and no definite volume. Gases can be compressed easily.

gas giants The outer, larger planets such as Uranus, Neptune and Jupiter are mainly made up of gases such as hydrogen and helium.

floatation

gas pressure

The process separation where light solids, like sawdust, float on a liquid.

The pressure exerted by gas particles-it depends on the number of gas particles and the speed (energy) of the particles.

foraminiferans Microscopic protists that live in tiny shells. When they die, their shells pile up in the sea, get squashed and cemented together to form a rock called chalk.

force A push, pull or twist that makes something move. Push and pull forces are measured in a unit called newton (symbol:

genes A section of a chromosome that is made up of a chemical called DNA. Genes control protein synthesis and hereditary characteristics.

genus A category of classification made up of closely related species. Glossary

177

gestation

histogram

The time taken for an organism to develop from fertilisation to birth. The gestation period for humans is about 40 weeks.

A type of column graph that shows information from a table in the visual form of vertical columns.

glucose

homeothermic

A simple sugar that is used in cellular respiration to produce energy.

Organisms like mammals and birds that can maintain their body temperature within narrow limits. They are also known as endothermic.

gnomon A stick-like structure that casts a shadow on a sundial.

humus

good conductor

The dark-coloured material in soil that is made up of decomposed organic material. It improves soil fertility and s microorganisms.

Material that es on heat and electricity without resistance. Metals are good conductors of heat. They heat up and cool down more quickly than poor conductors.

gravitational energy Stored energy in raised objects. A person standing on a diving board has gravitational energy-the gravity of the Earth pulls them down.

ground water Water that is found below the ground.

halite or rock salt When shallow seas, bays or salt lakes dry up, the salt in the water crystallises and deposits of salt called halite or rock salt are formed.

hammer In biology: one of the three bones in the middle ear.

hybrid When two different species mate, the offspring is infertile and cannot breed. A horse and donkey mate to produce a mule, which is infertile.

hypothesis A guess or a prediction that can be tested by an experiment.

ice erosion Erosion caused by ice and glaciers.

ice wedging When ice forms in a crack in a rock it expands and pushes the surrounding rock. This makes the crack larger and splits the rock.

impure substance A substance that is not pure and contains other substances.

hardness

impurity

A hard substance will scratch a soft substance. In hard substances, the particles are held together very tightly, so they cannot be scratched or pulled off. In a soft substance the particles are held loosely, and can be scratched off easily.

A substance that makes another substance impure by being present in it.

hazardous chemical

A light ray that hits a mirror is called an incident ray.

incident ray

Chemicals that are poisonous and dangerous to our health.

inference

headwater tract The starting point of a river or a stream.

A likely explanation of what is observed in an experiment. The explanation mayor may not be true.

heat energy

information

A type of energy that moves from places of high temperature to those of lower temperature. Heat energy is measured in joules (J).

heat transfer

Data collected during an experiment or a survey.

inner ear The innermost section of the ear, which sends sound impulses to the brain via the auditory nerve.

Heat energy can be transferred by conduction, convection or radiation from hot to cooler objects.

insoluble

heavy metals

insulator

Metals that are poisonous and are dangerous to our health. Mercury and lead are some examples of heavy metals.

hertz The unit used to measure frequency, e.g. the frequency of sound waves. (Symbol: Hz)

heterotrophs Organisms that cannot make their own food by photosynthesis. They feed on other organisms. Animals are heterotrophs.

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Not soluble-a solid that does not dissolve in a solvent. Poor conductors of heat energy are called insulators. Insulators retain heat longer. Rubber, glass, wood, air, wool and cotton are good insulators.

invertebrates Organisms that do not have a backbone.

investigation Finding out the cause of an occurrence or a phenomenon.

joules

lithification

A unit for work and energy. It is equal to the work done when a force of one newton moves an object a distance of one metre. It is named after James Prescott Joule (1818-89). (Symbol: J)

The formation of rocks from sediments or lava.

key In biology: a chart or table that allows us to identify and name living things. You could use a key to find the name of a strange plant or animal you had never seen before.

kinetic energy Energy possessed by a moving object. A person on a diving board has potential energy but when they are diving they have kinetic energy.

kingdom In biology: kingdoms are the largest groups of living things. All living things on Earth are classified into five kingdoms. The classification is based on the type of cell, and how the organisms obtain their food.

laboratory

living things Organisms that can move, need food, oxygen, reproduce and excrete wastes. They also respond to stimuli such as heat and light.

lubrication The use of lubricants such as oil and grease to reduce friction.

luminous objects Objects that give off their own light. The Sun, stars, and candles are luminous.

lunar eclipse When the Earth comes between the Sun and the Moon, the Earth's shadow covers the Moon completely or partially.

magnetic energy Magnets have a magnetic field .around them, which attracts magnetic material within that field.

A place where·science experiments are carried out.

magnetic field

land. degradation

A force of attraction exerted by magnets, which attracts magnetic materials like iron filings.

Due to erosion and excessive agricultural practices, land becomes infertile and unsuitable to grow plants.

laws of reflection The angle of incidence is equal to the angle of reflection. The normal, incident and reflected rays are all on the same plane.

lichen A group of organisms like fungi and green algae live together and help each other by symbiotic association. The algae photosynthesise and on food to the fungi while the fungi provide a place to live and some of the nutrients.

life All living things possess life. They grow, reproduce and then die.

light energy Energy produced by luminescent objects such as the Sun, stars and light bulbs. Includes lights, X-rays, microwaves, infrared waves. It is also known as radiant energy.

magnetic poles The opposite ends of a magnet, which point to the north and south poles of the Earth.

MRI (magnetic resonance image) MRI scans are clearer than X-rays and CAT scans. MRI scans show tiny cancers that are too small to detect any other way.

magnetic separators These are used in factories to separate materials. Some beach sands contain magnetic grains that are useful minerals-they are separated from the other non-magnetic grains with a magnetic roller.

magnetic substances Substances that are attracted by a magnet. Iron is a magnetic substance.

magnetosphere The Earth's magnetic field extends far into space beyond the atmosphere, where it is called the magnetosphere.

limestone caves

magnification

Caves made of limestone that are formed due to erosion caused by chemical weathering.

How many times larger an object appears compared to its size in real life. The magnification of a microscope is determined by multiplying the number on the objective lens by the number on the eyepiece lens.

limestone or chalk A type of rock made from the shells of marine organisms.

line graph A graph with a line ing the data points.

liquid A state of matter that possesses particles held together by weaker forces than in solids. Liquids have definite volume but no shape-they take the shape of the container they are in. Liquids are hard to compress.

malignant tumour A group of cells that form a tumour due to repeated division of cancerous cells. They grow into surrounding tissues and spread to different parts of the body. They can be fatal if not successfully treated.

Glossary

179

mammals

mind map

A group of organisms that belong to the phylum Chordata. They reproduce sexually, give birth to live young and feed them with milk produced in mammary glands. Humans, dogs and monkeys are mammals.

A way of linking all of the ideas learnt in a topic.

marsupials A group of mammals that possess pouches in which their immature young develop. The young attach themselves to nipples in the pouches. Koalas, kangaroos, possums and wombats are marsupials.

mitochondria A cell organelle that converts glucose to energy by cellular respiration.

mixture Made up of two or more elements or compounds mixed together physically. They can be separated easily and do not change their properties.

molecule

mass The amount of matter or particles in a substance. It depends on the number of particles in a substance and also on the heaviness of each particle. It is measured in grams or kilograms (Symbols: g and kg).

matter Anything that takes up space, has mass and can be touched is called matter. Matter exists in four states: solids, liquids, gases and plasma.

Two or more atoms of the same or different elements combine to form a molecule. Oxygen (02) and water (H20) are examples of molecules.

moon A non-luminous natural satellite that revolves around a planet. Earth has one moon that revolves around it every 28 days.

mudstone

melting

A sedimentary rock that is made up of mud particles.

The change of state where a solid changes to liquid because it is heated.

multicellular organisms

membrane A sheet-like tissue that covers, connects or lines cells and their organelles. Some substances, e.g. water and fat-soluble substances, can through membranes, other substances cannot.

meniscus

Organisms that are made up of many cells. Humans, cats and dogs are some examples of multicellular organisms.

mythology Old tales containing ideas about ancient times, often involving supernatural beings.

natural acids

A concave or convex upper surface that forms on a liquid in a tube as a result of surface tension.

Formed from the decay of dead animals, plants and from the rain. These acids are not very strong but can dissolve limestone rocks.

metamorphosis

navigation

The rapid transformation from the larval stage to the adult stage that occurs in the life cycle of many invertebrates and amphibians.

Using the position of the stars, Sun and Earth's magnetic field etc. to find your way. Animals such as insects and birds use these things to navigate, as well as humans.

microbes

negative charge

Organisms that can only be seen with a microscope. Bacteria, fungi, algae, protozoans and viruses are examples of microbes.

When an atom gains an electron it becomes a negatively charged ion.

micrographs

The Sun, the planets and their moons all attract each other with their gravity, and their speed stops them from falling towards each other. This model is called the Newtonian model.

Photographs of microscope slides taken with a camera attached to the eyepiece of a microscope.

microscope slide A slide that a specimen is placed on for observing with a microscope.

middle ear

Newtonian model

non-biodegradable Substances that cannot be decomposed or destroyed by the action of microorganisms.

The middle part of the ear-including an ear canal and three interconnected bones, called ossicles.

non-living things

middle tract

non-luminous objects

The middle region where a stream or river flows. It is wider, flows more slowly and deposits large stones in gravel beds. The river is said to be mature here.

Objects that do not give off their own light but reflect light from a luminous object. The Moon in non-Iuminous-it reflects light from the Sun.

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Objects that do not possess life.

normal

paper chromatography

In physics (light): the normal ray is a line drawn at right angles

Uses paper to separate the parts of a mixture containing dyes of different solubility. The most soluble dye ends up higher on the paper than the less soluble dyes.

to a surface between the incident ray and a reflected ray.

nuclear energy The centre of the nucleus of an atom has large amounts of stored energy that can be released by fission (dividing the atom).

parent rock Large rocks that are found in the bottom layer of soil below the ground.

nucleus

partial eclipse

In biology: a cell organelle that contains chromosomes and genes. It controls cell division, protein synthesis and es on hereditary characteristics. In chemistry and physics: the positively charged central core of an atom.

An eclipse where the Sun or Moon is partially covered by the Earth.

nutrients All living things need nutrients, such as carbohydrates, proteins, fats and minerals, to survive, and reproduce.

objective lens A lens in a microscope that objects are viewed through.

observant Being observant means noticing things around you by using all of your senses-seeing, tasting, smelling, hearing and feeling. To be good at investigating and solving problems, you need to be observant.

particle theory of matter States that everything is made up of particles that are in constant motion. The theory can be used to explain different properties of matter.

particles In chemistry: one of the fundamental components of matter. Atoms and molecules are called particles.

pasteurisation A process in which microbes are killed by heating and chilling milk.

penumbra

oncogene

Light from a wide source such as a fluorescent tube will form a shadow with a fuzzy edge-this is called a penumbra.

A gene that is capable of transforming a normal cell into a cancerous cell. They result from the mutation of normal genes (proto-oncogenes).

A magnet that retains its magnetic property indefinitely.

opaque

phase

An object that does not allow light rays to through it. Cardboard is an opaque object.

orbit In astronomy: the path taken by a planet around the Sun. In physics: the path taken by an electron around the nucleus of an atom.

organelles A small structure within a plant or animal cell that has a particular function. Nuclei, mitochondria and chloroplasts are examples of organelles.

organism All living things such as plants, animals and microbes are called organisms because they are made up of organic substance such as carbohydrates, proteins and lipids.

organs A distinct part of an organism, made of similar cells or tissues, that performs a particular function. For example, eyes and hearts are organs in animals, and roots are organs in plants.

outer ear The outermost part of the ear that receives sound waves and transmits them to the middle and inner ear.

permanent magnet

In astronomy: the shapes of the illuminated surface of the Moon as seen from Earth. The shapes change as a result of the relative positions of the Earth, Sun and Moon.

photosynthesis A process carried out by plants to produce starch from carbon dioxide and water. It is a chemical reaction that occurs with the help of chlorophyll and the presence of sunlight.

phylum A category used in the classification of organisms of Similarly related classes. Phyla are grouped into kingdoms.

physical change In this type of change, no new substances are formed.

Particles do not change apart from gaining or losing energy. Changes of state such as melting or boiling are physical changes and are easy to reverse.

physical properties Properties of an object that can be detected by our senses. Colour, smell, shape and taste are examples of physical properties.

physical weathering Erosion caused by non-living things such as heat, wind, water and ice.

palaeontologist A scientist who studies fossils .

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181

physicist

protein coat

A scientist who studies physics.

In biology viruses contain a protein coat surrounding the nuclear material that could be DNA or RNA.

physics Study of matter, energy and movement.

pie graph Pie graphs present information using a circle that has been divided into sections. Each section represents a fraction of a whole circle or pie.

pitch In physics: the property of sound that makes it sound high or low. It is related to the frequency of the sound waves and can be affected by the loudness of a sound. Sounds can be high pitched or low pitched.

protoplasm Consists of cytoplasm and a nucleus in a living cell.

pure substance Consists of only one type of particle. A pure substance becomes impure when it has a small amount of another substance mixed in with it.

radiation Giving out heat. It takes place without any heat-transferring matter and can travel through space. Any object that is hot will emit radiant energy.

plane mirror

rays

Flat mirrors that reflect images that are the same size as the object, right side up and laterally reversed. They are used at home (in bathrooms for example) and in periscopes.

Narrow beams of light or radiation.

plasma In chemistry: plasma is the fourth state of matter-it exists only at very high temperatures. When gases are heated to over 6000°C, they change to a plasma state. The inside of the Sun, lightning bolts and auroras contain plasma.

poikilothermic Another name for endothermic animals that cannot maintain constant body heat. Their body temperature fluctuates with external temperature.

polar region The land near the south or north pole.

poor conductor A substance that does not conduct heat and electricity freely. Water is a poor conductor.

positive charge When an atom loses an electron it becomes a positively charged ion. When two objects are rubbed together, one loses electrons to the other and becomes positively charged.

potential energy Energy that an object has stored inside it because of its position or shape. Potential energy can be turned into kinetic energy. For example, if you hold a ball up in the air it has potential energy. When you release it, it has kinetic energy as it falls to the ground.

prediction A guess about what is going to happen in future.

pressure The force acting on a unit area of surface or the ratio of force to area.

proboscis A tube-like mouthpart that helps an organism to suck liquid food. Butterflies have proboscis to suck nectar.

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real image When rays of light through a slide, the image and can be projected onto a screen. This image is known as a real image.

reflected ray A ray that is reflected off a smooth surface such as a mirror.

reflection The process in which light travelling in one material bounces off the surface of a second material that is smooth. You can see yourself in a mirror when light reflects off the silvered surface of the mirror

refraction When light rays from air, to water or glass, they bend. This bending of light rays is called refraction.

replication Viruses reproduce by injecting their DNA into a host cell, making the cell's DNA produce copies of the viral DNA.

residue The substance left in the filter paper after filtration of a solution.

resolution In optics: the ability of an optical instrument to form separable images of close objects.

resolving power For microscopes, the resolving power is taken as the minimum distance between two points that can be separated. The smaller the resolving power, the better the resolution.

respiration The process of taking in oxygen and removing carbon dioxide. It is also known as breathing.

revolution In astronomy: when an object goes around another object it is said to be revolving around it. Planets revolve around the sun. Another word for revolve is orbit.

risk factors

sieve

Factors that can cause cancer and other diseases. Smoking, UV rays and some chemicals are risk factors that can cause cancer.

A piece of equipment that separates large particles from small particles.

rock salt or halite

A sedimentary rock formed by silt (fine particles of mud).

When shallow seas, bays or salt lakes dry up, the salt in the water crystallises and forms rock salt or halite.

rocky planets The inner planets that are composed mainly of rocky materials. Mercury, Earth, Venus and Mars are rocky planets. Pluto is also rocky.

rotation Spinning around on an axis. Different planets have different rotation periods. Earth rotates every 24 hours. This causes day and night.

salinity The amount of salt in water or soil.

saprophytes Organisms, like fungi, that feed on dead, organic material. They cannot make their own food by photosynthesis.

satellite A smaller object held in orbit around a bigger body due to its gravitational attraction. The Moon is the natural satellite of the Earth. Man-made satellites also are found in space.

scanning electron microscope (SEM) These microscopes have a lower magnification but produce a three dimensional image, permitting a view of surfaces not possible with a transmission electron microscope (rEM) . Interactions of cells with one another can be studied using the SEM.

scientific method A method used by scientists to study things systematically by doing experiments. A series of steps that has to be followed is called the scientific method.

scientific model A model that allows scientists to visualise or imagine a scientific process that cannot be seen.

scientist A person who studies different branches of science systematically.

sedimentary rocks

siltstone simple microscope The first microscopes to be made, using only one magnifying glass (lens) in a tube.

soil horizon Soil consists of different layers that are formed by water moving minerals. Each layer is called a horizon.

soil profile The complete soil, with all of the horizons, is a soil profile.

solar eclipse When the Sun is obscured from Earth by the Moon. If it is completely covered it is called a total solar eclipse and if it is partially covered it is called a partial solar eclipse.

solar system Consists of the nine planets plus many moons and asteroids orbitting around the Sun.

solids A state of matter that possesses particles held together by strong forces . Solids have a definite shape and volume. Solids cannot be compressed.

solidification The change of state when a liquid cools and becomes a solid.

soluble Able to be dissolved. A soluble substance (or solute) can dissolve in a liquid (or solvent) .

solution When a solute dissolves in a solvent, it forms a solution.

sound energy Energy made by vibrating objects. The sound of speech and music is caused by vibrating objects.

sound loudness The loudness of sound depends on the wavelength of the sound waves and vibrations. The decibel scale (symbol: dB) is used to measure sound levels.

sound vibrations

Rocks made of fragments of rocks (sediments) that are cemented together naturally by chemicals in the ground.

When an object vibrates, it produces sound by compressing the air particles.

sedimentation

sound waves

The process whereby sediments are deposited.

sediments Layers of rock fragments that have been deposited by water are called sediments.

shale A type of sedimentary rock that is made up of mud, silt and sand.

Caused by the back-and-forth motion of air particles as energy es through them.

spalling In deserts, the daily heating and cooling of rocks affects only the outside layer, because rocks are not good conductors of heat. The outside of the rocks can then peel off like the skin of an onion. This is called onionskin weathering, ot spalling.

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183

species

super conducting magnets

The smallest group of organisms that are similar in structure and can produce fertile offspring. Two horses belong to the same species.

Electromagnets that are made with coils of super conducting wires. These allow electricity to flow with no energy loss. All of the energy goes into the magnetism.

specimen

super magnets

A sample of an object or substance that is viewed through a microscope.

Strong, permanent magnets made from boron, iron and neodymium. They are small and are used in electric motors and computer printers.

speed of sound Sound travels through the air at 330 m/s.

spinal cord The extension of the brain that connects it to the external and internal organs via sensory and motor nerves that carry incoming and outgoing messages.

spinning

surface water Water found above the ground in pools, rivers and oceans.

suspension In chemistry: fine, solid particles suspended in a liquid or gas. Chalk powder forms a suspension in water.

system

spontaneous generation

In biology: a system is made up of number of organs performing a certain function. For example, a digestive system has a stomach and intestines.

Making living plants and animals from non-living objects. For thousands of years, people believed that this happened. Because air was thought to contain a 'vital force' necessary to spontaneously generate life.

A way of presenting data so that it is easy to understand. Information is set in columns and rows.

Turn around and around quickly.

table

taxonomy

stacks Tiny islands that are left as the coast erodes. They are often made of harder rock than the surrounding rock and do not weather as easily.

The science of classification. Biologists classify organisms in categories called taxa (singular: taxon).

stalactites

A measure of how hot or cold something is. Temperature tells us how much heat energy can flow between an object and its surroundings. It can be measured in degrees Celsius (eC), using a thermometer.

Tapering cones or pendants that hang from the roofs of limestone caves. They are created by the dripping and hardening of calcium hydrogen carbonate in water and can take thousands of years to grow.

temperature

temporary magnet

Upward projections from the floor of a cave. Sometimes they meet and with stalactites.

A magnet that cannot retain its magnetic property for a long time. Electromagnets are magnetic only when the current is ed.

states of matter

theory of conservation of energy

stalagmites

Matter exists in four states: solid, liquid, gas and plasma.

static electricity Electricity produced by the rubbing of certain objects. The charges created do not flow and are said to be static.

subsoil Consists of a layer of large rock pieces and a layer of small rock pieces.

sublimation When a solid changes directly to a gas state when heated, without first changing to a liquid state. Iodine changes to vapour state directly when heated.

Sun-centred model A model stating that the planets revolve around the Sun in fixed orbits.

sundial An object that indicates the time of day by forming shadows in different positions on a dial, depending on the position of the Sun in the sky.

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Energy can be changed from one form into another. No energy is destroyed and no new energy is created in the change. This is called conservation of energy.

thunder As lightning travels through the air, its energy heats the air. This hot air expands rapidly and moves outwards at an explosive speed, producing a loud noise.

tissues In biology: a number of similar cells make up a tissue, for example, skin tissue.

topsoil Consists of fine soil, humus and dead plant matter.

tors Rocks produced due to spalling or onionskin weatheringthey are round in shape.

total eclipse See eclipse.

translucent

viruses

An object that allows some light rays to through it. Tissue paper is translucent.

Viruses are smaller than bacteria and are not made of cells. They consist of a core of chemicals (DNA, found in the nucleus of cells), surrounded by a protein coat.Viruses cause disease and can infect all types of living things. They reproduce by replication inside a host cell.

transmission electron microscopes (TEM) Microscopes that use beams of electrons (particles with negative charge) focused by magnets instead of light focused by glass lenses. The electrons form an image that can be photographed or seen on a screen. Electron microscopes can magnify up to 500 000 times.

volume The space occupied by an object. Solids and liquids have definite and fixed volume.

transparent

waste materials

An object that allows all light rays to through it. Glass is a transparent object.

In biology: cells produce nitrogenous wastes during cellular metabolic activities and carbon dioxide during cellular respiration. These wasted are removed by our excretory and respiratory systems.

umbra A shadow with a sharp, clear edge. Shadows are areas of darkness created by an opaque object blocking the light. If the light comes from a single point, such as a tiny torch bulb, an umbra is formed.

unicellular organisms Organisms that are made up of one cell. Bacteria and amoeba are some examples of unicellular organisms.

vacuole A membrane-bound sac containing food and other chemicals in a watery solution. Plants have large vacuoles.

vacuum A space that has nothing at all in it-not even air particles.

water erosion Weathering caused by moving water.

water table The amount of water under the surface of soil.

wavelength The distance between two high-pressure areas of a wave, or between two crests of a wave.

weathering Wearing away of rocks into smaller pieces by the action of water, ice, wind and organisms. There are three types of weathering: phYSical, chemical and biological.

valid

wind erosion

If an experiment can be repeated by someone else and the same results are obtained, it is said to be valid.

Erosion caused by the action of wind. For example, topsoil is carried away by wind.

Van de Graaff generator

work

An instrument that produces static electricity by rubbing a rubber belt against a brush. The resulting electric charge is spread over a metal dome.

When a force moves or lifts an object, we say that work has been done.

vaporisation

This is the part of the sky that the Sun, Moon and planets seem to move through. It is a narrow band that contains twelve large constellations.

The change of state when a liquid is heated and becomes a gas.

zodiac

variable In an experiment, the part that is being tested is the variable. The variable is compared with the control.

vertebrae Vertebrae are the bones that make up the backbone of an animal. The vertebrae protect the spinal chord. (Singular = vertebra)

vertebrate An organism that has a backbone made up of vertebrae. Fish, amphibians, reptiles, birds and mammals are vertebrates.

virtual image An image that is formed in a mirror and cannot be projected onto a screen.

Glossary

185

Index absorption 60, 68, 69, 129, 130, 131, 137 acid and acid rain 30,140-3,150-1 activated charcoal (carbon) 60-1,66, 68,69 adsorption 57, 60-1, 66, 68, 69 air and air pressure 28,36,46-7, 70, 132, 134, 135 air resistance 11, 110-11, 113, 125 algae 94, 95, 96, 97, 106, 107 amoeba 82,94,107 amphibians 98, 99, 100, 101, 107 amplitude 135, 139 animals 2,3,22, 74,80,81,82,83,86, 88,89,90,94,95,98-9,104,107,170 apparatus 8 asteroids 154, 156, 158, 159 astronomy and astronomers 2, 3, 18, 19,20,152-3,168,170-1 atmosphere 84,116,155,156,164,171 atoms 120, 121 backbone 98-9,100-1,104,106,107 bacteria 70,73,74,82,87,88,89, 94, 107, 140, 148 balances 16,17, 19,30,42,109 beakers 4,6,8,9, 11, 12-13, 14, 16, 19, 20, 21, 23, 32, 38, 40, 43, 44, 45, 51, 53,55,56, 60, 65, 71,83, 93, 127, 129, 140, 143, 147 binomial name 90,91, 104, 106 biology and biolOgists 2,3, 18, 19, 20, 25, 90, 94, 95, 106, 107 birds 98, 99, 100, 101, 106, 107 boiling 9,21,32-3,36-7,44-5,51,64, 66,67 bosshead 8,9,23,65,93 Bunsen burners 4,6, 7, 8, 9, 19, 20, 21, 23, 32, 44, 45, 51, 60, 64, 65, 66, 71, 93,127, 128, 129, 140, 147 calendars 162,170 cancer and carcinogens. 84-5, 86, 87 carbon dioxide 36,37,50,74, 75, 80, 88,89, 140, 142, 155 cells division 72, 73, 84-5, 86, 88, 89 general 72-3, 78, 79, 80-1, 86, 87, 89, 90, 94, 95 membrane 80-1,82,83,87 organisation 74-5 specialisation 72-3 theory 72-3, 87 wall 79,80-1,82,83,86,87,94 Celsius (temperature) 9, 16, 128 centrifuge 56, 57, 68, 69 chalk 11,12-13,43,53,54,56,69,146 charges (electrical) 62-3, 112, 120-1, 124, 125 chemical change 66-7,69 energy 126, 127 186

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chemicals 2, 3, 4, 5, 20, 84, 88 chemistry and chemists 2,3,18,19,20, 25 chlorophyll and chloroplasts 80, 81, 86, 87, 94, 95, 96 chromatography 58-9, 68, 69 clamp 8,9, 12, 13, 20, 21, 23, 44, 45, 64, 65,93,114 classification 90-1,106,107 clocks 162 colloids 53, 69 cornets 154, 158 com 116, 11~ 118, 119, 124 compressibility 36,40,41,47,50,51 computers and computer parts 118, 119, 126 concentration 40-1,51 concrete and concrete cancer 43, 142, 143, 151 condensation 36-7,39,44,50,51,64 conduction 126, 127, 128, 130, 131, 138, 139 conglomerate 147, 151 conservation of energy 126, 127, 138 constellations 168-9, 171 contraction 48-9 convection 126, 128, 129, 130, 131, 138,139 copper 57,114,115,118,124,125,127, 131 copper sulfate 12-13, 38, 69 crucible and crucible tongs 8, 9, 20 crystals and crystallisation 12, 13, 38, 51, 52, 68, 69, 88 cytoplasm 80-1, 82, 83, 86, 87

data 26-~28-9,34-5,85 decanting 56,57,69 density 42-3, 51, 69 deposition 142, 147, 151 desalination 64, 65, 68 desertification 148, 149, 151 diagrams 10-11 diffusion 36, 42-3, 44-5, 50, 51 dilution 40-1 diseases 18,19,22,35,78,82,83,84-5, 94 dissolving and filtering 11-12, 38 distillation 64-5,68,69 DNA (deoxyribonucleic acid) 24, 82 domains (magnetic) 114,115, 125 dye 40,41,43,58-9,60,68,84,86 Earth 2, 3, 20, 28, 51, 87, 94, 95, 112, 114, 116, 118, 122, 124, 125, 126, 131, 132, 152, 153, 154, 155, 156, 157, 158, 159, 160-1, 162, 164-5, 166-~ 168-9, 170, 171 echoes 135, 13~ 139 eclipses 166-7,170,171 ecology and ecologists 2, 3, 20, 22

eggs 72, 73, 83, 87, 100, 101, 103, 104, 107 elastic energy 126, 127, 138, 139 electrical charge see charges energy 126, 127 field 120, 124 electricity 55,62-3,118,119,120-1 electromagnetic energy 126, 132 electrons 76, 77, 120, 121, 122. 123, 125, 126, 127 electroscope 120, 124, 125 electrostatic force 112,120-1,122-3, 125 separation 62-3, 66, 69 separators 62-3 emulsion 69 endangered species 18, 19 energy ~3,20,39,44-5,46-~50,66, 74,80,82,86,124,126-7,128-31, 138-9, equipment (general) 8, 19, 93 see also names of pieces of equipment erosion 142,143,144-5,146-7,148-9, 150, 151 euglena 82, 94 evaporating basin 7, 8, 9, 20 p evaporation 36, 39, 44, 50, 51, 57, 68, 149 expansion 48-9, 51 experiments controls in 32-3, 35 definition of 2,3,18,19,30-1

fair and valid 32-3, 35 safety in 4-5, 20, 21, 23, 24 variables in 32-3 ferrites 118,119,124, 125 ferromagnetism 118, 124, 125 filter funnel and paper 8,11,12,13,19, 2l, 23, 53, 55, 57, 58, 60, 140 filtration 11, 12, 13, 21, 23, 52, 53, 55, 57, 60, 63, 69 fish 99, 100, 101, 106, 107, 142 fission of cells 82, 83, 86, 94 of nucleus 126 flagellum 82, 94 flasks (all types) 8,19,46,48,50,64, 65,71 flotation 56-7,66,68,69 force 108-9, 110-11, 112-13, 125 fossils 146, 147, 151 fractional distillation 64-5, 69 freezing 36-7,44,51 frequency 135 friction 110-11, 113, 120, 121, 124, 125 fungi 90,94,95,106,107,140 funnels 8,11, 12, 13, 19, 2l, 23, 55, 56, 57,60,140 galaxy 154

gas (lab fuel) 4, 6, 7, 20 gases (matter) 28, 36-7, 38-9, 40-1, 42-3,44-5,46-7,48-9,50,51,52, 64,65,128,129,131,135,138 gauze mat 6,7,8,9,19,20,21,23,32, 44, 45, 51, 60, 64, 65, 71, 93, 129 genes and genetics 3, 24, 25, 84 genus 90, 106, 107 geology and geologists 2, 3, 18, 19, 20 geophysics and geomagnetism 3, 116, 117,124,125 glass equipment 4,23,37,48,51,64, 66, 114, 128, 131, 132 glucose 74,80,81 graphs 26-028-9,34-5,85,137 gravitational energy 126, 120 139 force 112,113, 124, 142, 143, 152, 153,154,164,170

hardness 42-3, 50, 51 heat energy 44-5,74,126,127,128-31, 138 heat mat 6, 7, 8, 9, 15, 19,32,44,51,60, 65, 71, 129, 147 histograms 26-7,34-5 humans 90,94,95,100,101,137 humus 149, 151 hybrids 90, 91, 106 hydrochloric acid 66,67, 140, 141 hydrogen 51, 156, 157 hypothesis 10,11,14,15,18,19,30-1, 32-3, 35, 70, 71 ice 36,41,66,67, 122, 123, 140, 142, 143, 150, 151, 164 imperial system 16 impure substance 51,60,61,68,69 inertia 111 inference 30-1, 32-3, 35 infertility 90, 91 infrared rays 126, 129 insects 90, 102, 103, 104, 105, 106, 107 insoluble 12, 13, 23, 53, 56, 57, 68, 69 insulators 120, 121, 128, 131, 139 invertebrates 98-9, 102-4, 106, 107 iron and iron filings 54,55,56,57,67, 68,114,115,116,117,118,119,124, 125, 128, 159

joules 128 Jupiter 77,152,154,156,158,159,170, 171 keys 92-4, 106 kinetic energy 44-5, 51, 126, 127, 128, 139 kingdom 90,94-5,96-0106,107 laboratory equipment see equipment picture of 2 safety in 4-5, 20, 21, 23, 24 working in 6-7 larvae 100, 103, 104 length 16, 17 lichen 94,95,106 Liebig condenser 64, 65 light energy 81,126,129,132-4,138 lightning 36, 122-3, 124, 125

limestone 140,141, 142, 146, 147, 151 liquids 36-7, 38-9, 40-1, 42-3, 44-5, 48-9, 50, 51, 52, 64, 65, 68, 128, 129, 131, 135, 138 lithification 146, 151 living things 88-9 lubrication 110, 125 luminous objects 132, 139

maggots 70,71,103,104 magnets and magnetism 54-5,56,57, 66,68,68,69,76,112,114-15, 116-10 118-19, 124, 125, 126 electro 55, 118, 119, 124, 125 permanent 114,115,118,119,125 super 118,119,124, 125 superconducting 118, 119, 124, 125 temporary 114, 115, 116, 118, 119, 125 magnetic domains 114,115 energy 126, 127 fields 116-10 120, 124, 125, 126 force 112,113,114-15,125 levitation 125 poles 114, 115, 116, 124, 125 roller 54, 55 resonance imaging (MRI) 118,119 separation 54-5, 57 substances 54-5,56,68,69,114, 115, 125, 126, 127 magnetosphere 116, 124, 125 magnification 76, 77, 78, 79, 86, 140 mammals 100, 101, 104, 106, 107 Mars 152,154, 155, 156, 158, 159, 170, 171 marsupials 100, 101, 106, 107 mass 16,17,40-1,42-3,47,50,51,108, 154 matter 2,3,16,36-7,38-9,40-1,120, 121 measuring cylinders 8,16,17,19,32, 40,60,71,93,136,140,149 measurements 16-17 melting 36-7,39,44,50,51,66,69 meniscus 16, 23 Mercury 152,154,155,158,159,170, 171 metamorphosis 103, 104, 106, 107 meteors and meteorites 154, 158, 164 meteorologist 3 method (scientific) 32-3 methylene blue 79 metric system 16, 17 microbes and microbiology 70, 71, 72, 87,88 micrographs 81, 86 microscopes compound 76-7,78-9,83 dissecting 76-7,86 electron 76-7,86 history of 77 general 2,28,72,73,76-7,78-9,81, 82 scanning electron 76 simple 76 stereo 2, 28, 76 transmission electron 76

microwaves 22, 51, 126 mind maps 18-19,21,35,51,69,87, 106,125, 139, 151, 171 mirrors 133-4, 138 mitochondria 80-1,87 mixtures 52, 56, 69 molluscs 98, 99, 106, 107 monera 90, 94, 95, 106, 107 monotremes 100, 101, 106, 107 Moon 152,153,155,162,164-5,166-7, 168,170,171 moons 154, 155, 156, 150 158, 159 mortar 8, 12, 13, 20, 23 mosses 94, 96, 97 movement (physics definition) 2, 3, 20 multicellular organisms 72, 73, 74, 75, 86, 87, 88, 94, 95

Neptune 152, 153, 154, 156, 157, 158, 159,170,171 neutrons 120, 121 newton (unit of force) 108, 112, 113, 125 Newtonian model 152,153 nitrogen 28,148,155 non-luminous objects 132 normal (in light) 133-4, 138 nuclear energy 22, 126, 154 nucleus of atom 120, 121, 126 of cell 79,80-1,82,83,86,87,94 nutrients 70, 72, 73, 88, 89, 95, 96 observation 24-5,30-1,32-3,35 oil 52, 56, 57, 64, 65, 96 oncogene 84,85,87 opaque 32, 134, 139 orbit (astronomy) 152, 160-1, 171 organelles (of cells) 80-1,82,86,87, 94,95 organisms 59, 70, 72-3, 74-5, 83, 87, 88,89,90-1,93,98 organs 74,75,86,87 ovary and ovum 72, 73, 84, 87, 103 oxygen 28, 74, 75, 80, 81, 88, 89, 96, 100, 155 particles and particle theory 38-9, 40-1,42-3,44-5,46-048-9,50,51, 52,53,56,62,66,67,69,120-1, 122-3, 126, 120 128, 131, 135, 137 pasteurisation 70-1 penumbra 132, 166, 160 171 perspex rod 62-3, 120-1, 124 pestle and mortar 8, 12, 13, 20 Petri dish 2,38,55,57 phases of Moon 164-5,171 photosynthesis 80, 81, 87, 96 phylum 90,98-9,102,104,106 physical change 66-7 physics and physicist 2,3,18, 19, 20, 22,25 pipe-clay triangle 8, 20 pipette 79, 83, 129 pitch (sound) 135-7, 139 placentals 100, 101, 104, 106, 107 planets 2,3,152,153,154-9,168,170, 171

Index

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187

plants 2,3,20,74,80,81,82,83,86,87, 88,89,90,94,95,96-7,104 plasma (matter) 36-7,51,69 plastics 64,65,88, 114, 115, 117, 131 Pluto 152, 153, 154, 155, 156, 157, 158, 159,170,171 pollution 142,143 potassium permanganate 129 potential energy 126, 127, 138, 139 pressure 46-7,50,51,137 properties of matter 40-1, 66, 69 protists or protista 82-3, 90, 94, 95, 106, 107 protons 120, 121 protoplasm 80-1, 86, 87 pupae 103, 104 pure substance 51, 69

radar and radio 22, 126 radiation and radiant energy 84, 126-31, 138-9 records and reports 10-11 reflection 129, 131, 132, 133-4, 139 refraction 77, 132 replication 82, 83, 88 reproduction 72, 88, 89, 90, 94, 96, 101, 103, 104, 106 reptiles 98, 100, lOt 106, 107 residue 53 respiration and respiratory system 74, 75, 80, 87, 88, 89, 96 retort stand 8, 9, 11, 12, 13, 20, 21, 23, 44,45,55,65,93, 114 revolution 171 risk factors 84, 85 rivers 142, 143, 144-5, 150, 151 rocks 2,3,20,88,89,140-1,142-3, 146-7,150-1 safety glasses 8,20,23,44,140 safety in laboratory 4-5, 20, 21, 23, 24 salinity 148,149, 150, 151 salt 38,55, 56, 57, 62, 65, 68, 69, 71 sandstone 140, 141, 146, 147, 151 satellites 18, 19, 164-5 saturated solution 38 Saturn 77, 152, 154, 156, 158, 159, 170, 171 scales biology 99, 100, 101, 106, 107 mass 16, 10 19, 109, 112 science and scientists 2, 3, 18, 19, 107 scientific journals and magazines 14,15;19 method 32-3 model 38,51 seasons 160-1, 170 sedimentation 56-7,68,69,142-3, 144-5, 140 150, 151 separation 52-3,56,57,62-3 shadows 132 shape 36-7 siderial time 162, 153 sieving 53, 55, 68, 69 skeleton 74, 75, 90, 98, 99, 100, 103, 104 soil composition 148-9 188

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horizon 148-9,151 profile 148-9, 151 solar energy 126 system 154-9,171 time 162, 163 solids 36-7,38-9,40-1,42-3,44-5, 48-9,50, 51, 68, 128, 131, 132, 135, 138 solubility and solutes 12, 13, 21, 38, 40-1,53,56,58,59,64,66,68,69,84 sound 135-7 energy 122, 123, 126, 127, 135-7, 138, 139 speed 135, 137 waves 135-6 space (astronomy) 20,170 sparks 122-3 spatulas 8, 20, 23, 60, 62, 66, 71, 127 species 18, 19, 90, 91, 106, 107 sperm 72,87 spontaneous generation 70-1, 83 spores 70, 82, 83, 94, 96, 97 stacks 144, 145 stalactites and stalagmites 140,141, 151 stars 2, 3, 20, 126, 132, 152, 153, 154, 159, 162, 168-9 states of matter 36-7, 44-5, 50, 51 static electricity 62-3, 120-1, 122, 124, 125 sterility 70 streamlining 110, 125 subsoil 148,151 sublimation 36-050,51 sugar 12, 13,53, 60, 66, 67, 71, 74 Sun 36, 126, 127, 131, 132, 152, 153, 154,155,156,157,158,159,160-1, 162,153,164, 165, 166-7, 168, 170, 171 sundial 162-3,170,171 sunlight 78, 80, 82, 84, 85, 88, 89, 95, 130,165 superconducters 118 suspension 12, 13, 21, 56, 57, 68, 69 systems 74,75,86

tables 26-7,34-5 taps 4, 6, 7, 20 taxonomy 91 technology 3 temperature 9, 16,21, 23, 31, 32-3, 34, 44-5,46, 48-9, 50, 64, 98, 103, 126, 127,128,129, 131, 137, 151, 154, 164 test tubes 8, 19,20,21,23,40,51,54, 58,64,66,68,127,136, 140, 141 theory (definition of) 14,15, 18, 19 thermometer 8,9,16,21,23,32,44,45, 50, 51, 65, 128, 130 thunder and thunderstorms 122, 123, 124, 125 tides 164, 165 time 16, 10 162-3 tissues 74,75,86,87 tongs 8,9,20,21,23,60,66,127, 147 translucency 132, 134, 139 transmission 129, 138

transparency 71, 132, 134, 139 trees 95,96,105,140,148-9 tripod stand 6,8,9, 19, 21, 23, 32, 44, 45,51,55,60,64,65,93,128,129 tumours 84, 85 tuning fork 136-7

umbra 132, 166, 160 171 unicellular organisms 74,75,82-3,87, 88,94 units of measurement 16 universe 2, 3 Uranus 152, 153, 154, 156, 157, 158, 159 vacuole 80,82,86,87 vacuum and vacuum flask 130,131, 132, 134, 135, 138, 139 Van Allen belts 125 Van de Graaff generator 123 vaporisation 36-7,39,44,50,51,64, 65,69 Venus 152,154-5,158,159,170,171 vertebrates 94,98-9,100-1 vinegar 66,67,140,141 viruses 82, 83, 84, 88, 89 volume 16,17,36-7,42-3 wastes 72, 74, 75, 80, 82, 88, 89, 100, 103 watchglass 8, 32, 62 water boiling point 9,44-5,51 clocks 162 conductor 131 erosion 142-3, 151 pressure 46 seawater 64, 65, 68, 69 supply 28 vapour 36,44,45,65,75,155 waste product 74, 75, 80, 81, 148 waves and wavelength 132, 134, 135, 137,138,142,143 weathering 140-1,142-3,147,150, 151 weight 108 ~nd 140, 141, 14~ 148, 151 X-rays 84, 118, 126 zodiac 168-9, 171 zoologist 22

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