Key Stage 3 Science - Cambridge University Press & Assessment

[Pages:7]Key Stage 3 Science

Andy Cooke Jean Martin

Series editors

Consultant Authors

Andy Cooke Jean Martin

Sam Ellis

Andy Cooke Sam Ellis David Glover Jean Martin Janet McKechnie Chris Ram Nicky Thomas

PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge, United Kingdom

CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK 40 West 20th Street, New York, NY 10011-4211, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia Ruiz de Alarc?n 13, 28014 Madrid, Spain Dock House, The Waterfront, Cape Town 8001, South Africa

? Cambridge University Press 2004

First published 2004

Printed in Dubai by Oriental Press

Typeface Delima MT System QuarkXPress?

A catalogue record for this book is available from the British Library

ISBN 0 521 54923 X paperback

Material in this book was previously published in Spectrum Year 7 Class Book (pp. 105?162), Spectrum Year 8 Class Book (pp. 97?146) and Spectrum Year 9 Class Book (pp. 107?158).

Cover design by Blue Pig Design Co Page make-up and illustration by Hardlines Ltd, Charlbury, Oxford

NOTICE TO TEACHERS It is illegal to reproduce any part of this work in material form (including photocopying and electronic storage) except under the following circumstances: (i) where you are abiding by a licence granted to your school or institution by the Copyright Licensing Agency; (ii) where no such licence exists, or where you wish to exceed the terms of a licence, and you have gained the written permission of Cambridge University Press; (iii) where you are allowed to reproduce without permission under the provisions of Chapter 3 of the Copyright, Designs and Patents Act 1988.

Contents

Introduction

Unit 7I Energy resources

7I.1 Energy and fuels 7I.2 Fossil fuels 7I.3 Renewable energy resources 7I.4 Living things and energy

Unit 7J Electrical circuits

7J.1 How electrical circuits work 7J.2 Inside a circuit 7J.3 Energy for the circuit 7J.4 Parallel circuits 7J.5 Using electricity safely 7J.6 Discovering electricity

Unit 7K Forces and their effects

7K.1 Where we come across forces 7K.2 Weight 7K.3 Stretching materials 7K.4 Floating and sinking 7K.5 Friction 7K.6 Moving and stopping

Unit 7L The Solar System and beyond

7L.1 The Earth in space 7L.2 The four seasons 7L.3 Lights in space 7L.4 The Sun and the Moon 7L.5 The Solar System 7L.6 Beyond the Solar System

Unit 8I Heating and cooling

8I.1 Measuring how hot things are 8I.2 Changing the temperature 8I.3 Hot to cold 8I.4 Moving the heat energy in liquids and gases 8I.5 How energy travels through space 8I.6 Keeping warm 8I.7 Changing between solid, liquid and gas

Unit 8J Magnets and electromagnets

8J.1 Magnetic forces 8J.2 Magnetic fields 8J.3 Making and using magnets 8J.4 Making and using electromagnets

Page v

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1 5 8 12

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30

30 32 34 36 39 42

45

45 48 50 52 54 56

59

59 61 62 64 66 67 68

72

72 75 76 78

iii

Unit 8K Light

8K.1 Where light comes from and how it travels 8K.2 Light hitting objects 8K.3 Mirrors 8K.4 Bending light 8K.5 The spectrum 8K.6 Colours

Unit 8L Sound and hearing

8L.1 Making sound 8L.2 Travelling sound 8L.3 Hearing sound 8L.4 Dangerous sound

Unit 9I Energy and electricity

9I.1 How is energy involved in doing useful things? 9I.2 How does electricity transfer energy? 9I.3 Paying for and reducing the waste of electricty 9I.4 Where do we get electrical energy from?

Unit 9J Gravity and space

9J.1 What is gravity? 9J.2 How have our ideas about the Solar System changed? 9J.3 What keeps the planets and satelites in orbit?

Unit 9K Speeding up

9K.1 Describing how fast something moves 9K.2 Working out speed 9K.3 Force and speed 9K.4 Slowing things down 9K.5 Streamlining 9K.6 Skydiving and parachutes

Unit 9L Pressure and moments

9L.1 What is pressure? 9L.2 Gases under pressure 9L.3 Liquids under pressure 9L.4 Turning forces 9L.5 Balance and levers

Scientific investigations

Glossary/Index Acknowledgements

82

82 85 87 89 91 93

97

97 101 103 105

109

109 111 113 116

119

119 122 125

131

131 133 136 139 141 144

147

147 150 152 154 157

161

169 178

iv

7I

Energy resources

In this unit we shall be studying what energy is and how we use it.

7I.1 Energy and fuels

Energy is one of the big ideas in science. It is so important that it has its own unit, joules. We measure energy in joules.

What energy is

Anything that involves energy change can be called work. Nothing can happen without energy making it happen.

The microwave oven needs energy to cook.

The rocket needs energy to take off.

To do work energy must change in some way. It can:

? move from one place to another ? this is called energy transfer;

? change from one type of energy to another ? this is called transformation.

The cheetah needs energy to run.

The plant needs energy to grow.

KEY WORDS

energy joules gravitational potential chemical kinetic heat light elastic potential electrical sound engine Bunsen burner fossil fuel coal mineral oil natural gas non-renewable renewable wind tidal solar wave hydro-electric geothermal biomass

1 What is meant by energy? 2 What must energy do to make things happen?

3 Make a list of six things that you think need energy to make them happen or work.

Unit 7I 1

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