新综合科学 牛津原版 2PDF电子书下载

Unit 7　Living Things and AirCommon gases 2

Composition of the air 6

What is air? 10

Uses of the gases in air 10

Breathed and unbreathed air 11

What makes these differences? 14

Respiration 15

How air passes in and out of us 17

Breathing in and out 19

Different breathing systems 23

Do plants respire? 24

How do plants obtain energy? 27

Most plants contain starch 28

Photosynthesis　 31

Oxygen/carbon dioxide balance 33

Photosynthesis and food chains 34

Food webs　 34

The pollution of our air 36

Summary　 37

Difficult words　 40

Unit 8　ElectricityUse of electricity　 42

Conductors,insulators　 48

Electric current 49

Resistance　 50

Lighting and heating effects 53

Fuses and circuit breakers 58

Electricity at home 59

Magnetism　 72

Electromagnets 77

Electrochemistry　 82

Summary 85

Difficult words 87

Unit 9　Heat TransferHeat energy 92

Heat transfer in gases 93

Convection in liquids 96

Heat transfer in solids 99

Conduction in air and water 101

Radiation 103

Applications of heat transfer 108

How living creatures keep warm 112

Summary 115

Difficult words 117

Unit 10　Hydrogen,Acids and AlkalisProperties of hydrogen 120

Some uses of hydrogen 122

Breaking down water 123

Metals and water 126

Reactivity 134

Metals and acids 135

Reacting with sulphuric acid 137

Comparing reaction rates 138

Reactivity series 140

Acids and alkalis 141

The pH scale 145

Acid+Alkali=?　 147

Neutralization and concentration 150

Applications of neutralization 154

Summary 156

Difficult words 159

Unit 11 Detecting the environmentOur senses and sense organs 162

Light and eyes 164

How a pinhole camera works 166

Thick lens and thin lens 172

Making sharp images 174

How our eyes see objects 174

How cameras 'see' objects 175

Comparing the eye with the camera 176

Normal eye,long and short sight 176

Limitations of vision 180

The noisy world 183

Pitch 188

Transmission of sound 191

The range of hearing 197

Taste and smell 198

The sense of smell 203

Skin　 207

Into the brain　 209

Persistence of vision 212

Summary 214

Difficult words 217

Unit 12 Forces and MovementWhat is force? 220

Friction　 226

Weighing　 231

Levers 235

Using levers 237

Human lever systems 239

Work and energy 242

Pulleys 245

Action and reaction　 247

Summary 251

Difficult words　 254

Index　 255