Key Stage 3 Science - Cambridge University Press & Assessment

Key Stage 3 Science

Series editors Consultant Authors

Andy Cooke Jean Martin

Sam Ellis Doug Wilford

David Acaster Derek Baron Trevor Bavage Andy Cooke David Fagg Kevin Frobisher Jean Martin Mick Mulligan Doug Wilford

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 54922 1 paperback

Material in this book was previously published in Spectrum Year 7 Class Book (pp. 53?104), Spectrum Year 8 Class Book (pp. 51?96) and Spectrum Year 9 Class Book (pp. 50?106).

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 7E Acids and alkalis

7E.1 What acids and alkalis are like 7E.2 Telling acids and alkalis apart 7E.3 Universal indicator and the pH scale 7E.4 Neutralisation and the rainbow experiment 7E.5 Where neutralisation is important

Unit 7F Simple chemical reactions

7F.1 Chemical reactions 7F.2 Reactions between acids and metals 7F.3 Reactions between acids and carbonates 7F.4 Reactions when substances burn 7F.5 Reactions when fuels burn 7F.6 Looking at a candle burning

Unit 7G Particle model: solids, liquids and gases

7G.1 Looking at and thinking about substances 7G.2 Thinking about theories 7G.3 A closer look at solids, liquids and gases 7G.4 Some evidence for the particle theory 7G.5 Using the particle model 7G.6 More uses of the particle model

Unit 7H Solutions

7H.1 Mixing solids and liquids 7H.2 Salt of the Earth 7H.3 The mystery of the disappearing solute! 7H.4 Separating solvents from solutes 7H.5 Chromatography 7H.6 Solubility

Unit 8E Atoms and elements

8E.1 Materials 8E.2 What the elements are like 8E.3 How we get all the other materials 8E.4 Representing the changes

Unit 8F Compounds and mixtures

8F.1 Elements and compounds 8F.2 Looking at compounds 8F.3 Compounds and some of their reactions 8F.4 What is a mixture?

Page vii

1

1 5 7 9 11

15

15 16 17 18 20 22

25

25 26 28 29 32 36

39

39 42 43 45 47 49

53

53 55 60 62

65

65 67 68 69

v

Unit 8G Rocks and weathering

77

8G.1 Rocks vary

77

8G.2 Rock and rain

78

8G.3 Rocks and temperature changes

81

8G.4 Moving weathered pieces of rock

83

8G.5 Why sediments form layers

84

Unit 8H The rock cycle

89

8H.1 How sedimentary rocks form

89

8H.2 Limestones are not all the same

91

8H.3 Rocks are sometimes changed

92

8H.4 Rocks formed from molten magma

94

8H.5 Recycling rocks

97

Unit 9E Reactions of metals and metal compounds 99

9E.1 Why are metals useful?

99

9E.2 Reacting metals with acids

102

9E.3 Reacting metal carbonates with acids

104

9E.4 Reacting metal oxides with acids

105

9E.5 More about salts

106

Unit 9F Patterns of reactivity

111

9F.1 What happens to metals?

111

9F.2 Metals and water

112

9F.3 Reactivity of metals with acids

114

9F.4 Metals and oxygen

115

9F.5 Displacement reactions

116

9F.6 Sources and uses of metals

119

9F.7 Investigating metals and acids further

123

Unit 9G Environmental chemistry

9G.1 Are soils different from each other? 9G.2 Acid rain 9G.3 What causes acid rain 9G.4 Can we reduce the amount of acid in the rain? 9G.5 Is global warming really happening?

126

126 128 131 132 137

Unit 9H Using chemistry

9H.1 What chemical reactions take place when fuels burn? 9H.2 Chemical reactions as energy resources 9H.3 What new materials can chemical reactions make? 9H.4 Atoms and molecules in new materials

141

141 146 149 151

Scientific investigations

156

Glossary/Index

164

Acknowledgements

174

vi

7E

Acids and alkalis

In this unit we shall be finding out about acids and alkalis and how to recognise them. We shall also look at some uses of acids and alkalis and at neutralisation reactions.

7E.1 What acids and alkalis are like

Acids are all around us

It is amazing how many things around us contain acids. Some acids are in the food we eat. We use acids to make things work properly and to make all sorts of useful items. Some acids are harmless, but others are very dangerous.

Fruit or drinks made from fruit often contain acids. They have a tangy, sharp taste. We say acids taste sour.

1 Look at the picture. Write down a list of substances that contain acids.

2 Write down:

Limes and lemons taste sour because they contain citric acid. Lemons and limes prevent scurvy because they contain vitamin C. Vitamin C is also an acid, but it is

a very weak acid.

a one word that best describes the acid taste of lemon juice;

b the name of the acid that gives lemon juice this taste.

3 a What is the name of the other acid in limes and lemons?

b What disorder does this acid help to prevent?

KEY WORDS

acid sour hydrochloric acid hazard corrosive dilute harmful irritant risk alkali sodium hydroxide extract indicator full-range universal

indicator pH scale neutral react neutralisation salt indigestion

Unit 7E 1

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