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Contents

1 Asking scientific questions 2 4 Analysing patterns 82 Planning investigations 4 5 Evaluating data 10 3 Recording data 6

Enquiry processes

1.1.1 Introduction to forces 14 1.2.1 Gravity 221.1.2 Balanced and unbalanced 16 Part 1 Summary and Questions 241.1.3 Speed 181.1.4 Distance–time graphs 20

1.1 Speed 1.2 Gravity

1: Forces Part 1 Opener 12

2.1.1 Potential difference 28 2.2.1 Current 342.1.2 Resistance 30 2.2.2 Charging up 362.1.3 Series and parallel circuits 32 Part 1 Summary and Questions 38

2.1 Potential difference and resistance 2.2 Current

2: Electromagnets Part 1 Opener 26

3.1.1 Food and fuels 42 3.2.1 Energy adds up 483.1.2 Energy resources 44 3.2.2 Energy dissipation 503.1.3 Energy and power 46 Part 1 Summary and Questions 52

3.1 Energy costs 3.2 Energy transfer

3: Energy Part 1 Opener 40

4.1.1 Sound waves and speed 56 4.2.1 Light 644.1.2 Loudness and amplitude 58 4.2.2 Reflection 664.1.3 Frequency and pitch 60 4.2.3 Refraction 684.1.4 The ear and hearing 62 4.2.4 The eye and vision 70 4.2.5 Colour 72 Part 1 Summary and Questions 74

4.1 Sound 4.2 Light

4: Waves Part 1 Opener 54

5.1.1 The particle model 78 5.2.1 Pure substances and mixtures 945.1.2 States of matter 80 5.2.2 Solutions 965.1.3 Melting and freezing 82 5.2.3 Solubility 985.1.4 Boiling 84 5.2.4 Filtration 1005.1.5 More changes of state 86 5.2.5 Evaporation and distillation 1025.1.6 Diffusion 88 5.2.6 Chromatography 1045.1.7 Gas pressure 90 Part 1 Summary and Questions 1065.1.8 Inside particles 92

5.1 Particle model 5.2 Separating mixtures

5: Matter Part 1 Opener 76

iiiGlossary 218Index 228

6.1.1 Chemical reactions 110 6.2.1 More about elements 1226.1.2 Acids and alkalis 112 6.2.2 Chemical reactions of metals and non-metals 1246.1.3 Indicators and pH 114 6.2.3 Metals and acids 1266.1.4 Acid strength 116 6.2.4 Metals and oxygen 1286.1.5 Neutralisation 118 6.2.5 Metals and water 1306.1.6 Making salts 120 6.2.6 Metal displacement reactions 132 Part 1 Summary and Questions 134

6.1 Acids and alkalis 6.2 Metals and non-metals

6: Reactions Part 1 Opener 108

7.1.1 The structure of the Earth 138 7.2.1 The night sky 1487.1.2 Sedimentary rocks 140 7.2.2 The Solar System 1507.1.3 Igneous and metamorphic rocks 142 7.2.3 The Earth 1527.1.4 The rock cycle 144 7.2.4 The Moon and changing ideas 1547.1.5 Ceramics 146 Part 1 Summary and Questions 156

7.1 Earth structure 7.2 Universe

7: Earth Part 1 Opener 136

8.1.1 Levels of organisation 160 8.2.1 Observing cells 1688.1.2 The skeleton 162 8.2.2 Plant and animal cells 1708.1.3 Movement: joints 164 8.2.3 Specialised cells 1728.1.4 Movement: muscles 166 8.2.4 Movement of substances 174 8.2.5 Uni-cellular organisms 176 Part 1 Summary and Questions 178

8.1 Movement 8.2 Cells

8: Organisms Part 1 Opener 158

9.1.1 Food chains and webs 182 9.2.1 Flowers and pollination 1909.1.2 Disruption to food chains and webs 184 9.2.2 Fertilisation and germination 1929.1.3 Ecosystems 186 9.2.3 Seed dispersal 1949.1.4 Competition 188 Part 1 Summary and Questions 196

9.1 Interdependence 9.2 Plant reproduction

9: Ecosystems Part 1 Opener 180

10.1.1 Variation 200 10.2.1 Adolescence 20610.1.2 Continuous and discontinuous 202 10.2.2 Reproductive systems 20810.1.3 Adapting to change 204 10.2.3 Fertilisation and implantation 210 10.2.4 Development of a fetus 212 10.2.5 The menstrual cycle 214 Part 1 Summary and Questions 216

10.1 Variation 10.2 Human reproduction

10: Genes Part 1 Opener 198

Some microwaves cook popcorn faster than others. Why is there a difference?

Microwave ovens have a power rating in watts (W). The power rating tells you how much energy is transferred per second–the rate of transfer of energy.

You can calculate power using this formula:

power (W) = energy (J) time (s)

The power of a microwave oven is about 800 W. A traditional oven has a power of about 2500 W, or 2.5 kilowatts.

Most of the heating appliances in your house will have a rating in kilowatts. Light bulbs have a rating in watts.Fantastic Fact

When you make popcorn you are boiling water. The water inside the popcorn kernel turns to steam and it explodes.

Kilowatts and kilojoules12 000 W is the same as 12 kilowatts, or 12 kW. There are 1000 W in 1 kW. You divide by 1000 to convert watts to kilowatts.

An oven with a rating of 2.5 kW transfers energy at a rate of 2500 J per second. This is the same as 12 kilojoules per second. There are 1000 J in 1 kJ.

A State the unit of power.

Keeping the temperature the sameAll hot objects cool down. To keep a house at the same temperature you need to transfer energy to it at the same rate as energy is being transferred from it.

What are you paying for?When you pay an electricity bill, you are usually paying for a fuel such as coal to be burnt in a power station. The power station generates the potential difference that we call ‘mains electricity’. You are charged for the number of hours that you use each appliance and for the power of the appliance.

You can calculate energy use in kilowatt hours (kWh) or joules. This is the unit that electricity companies use to calculate your bill.

The power rating of this appliance is 2000 W.

Some houses transfer more energy to the surroundings than others.

Learning objectivesAfter this section you will be able to:

● describe what you pay for when you pay your electricity bill

● calculate the cost for home energy usage

● compare the energy usage and cost of running different home devices.

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Energy and power3.1.3

You can calculate the cost of using appliances at home using the formula:

cost = power (kW) × time (hours) × price (per kWh)

Suppose you use a 2.5 kW oven for 2 hours. Each kWh costs 10p.

cost = 2.5 kW × 2 hours × 10 p/kWh = 50 p

B State the unit of energy that electricity companies use.

To reduce your energy bills you could use fewer appliances or appliances that require less power to produce the same output. You can also use appliances for fewer hours. Insulation reduces the rate at which energy is transferred to the surroundings, so it reduces the rate at which you need to supply energy to heat the house.

Governments can raise awareness about energy use to try to make fossil fuels last longer. This would also benefit the environment.

What’s the cost?A shower has a power of 10 kW. A family uses the shower for 1 hour per day.

a Calculate how much energy, in kilowatt hours, they would have to pay for each week for using the shower.

b An electricity company charges 10p for each kWh. Calculate the cost in pounds.

The bulbs are the same brightness but the one on the right has a much lower power.

watt, power, kilowatt, kilowatt hour

Key Words

Summary Questions1 Copy and complete the

sentences below.

Energy is measured in and power is measured in . Power is the energy transferred per

. You pay for the number of that are transferred to your

house by electricity. You could save money by using appliances with a power rating or by using them for time.

(6 marks)

2 Compare the cost of using a kettle with a power rating of 2 kW and a kettle rated 1.2 kW.

(6 marks)

3

a Suggest a measure that a government can take to reduce a country’s energy use. (1 mark)

b Suggest reasons why the campaign may be successful. (1 mark)

The electricity meter shows how much energy you have used in kWh.

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Big Idea: Energy 3

Topic 3.1 Energy costs

Do you have some money in your pocket? If you know how much you left home with and you didn’t spend any on the way, then you know how much you have now.

Conservation of energyEnergy cannot just disappear, and you cannot end up with more than you had at the start. Energy cannot be created or destroyed, only transferred. This is the law of conservation of energy.

A State the law of conservation of energy.

Energy storesThere is energy associated with food and fuels (and oxygen). You can think of that energy as being in a chemical energy store. Energy is transferred from the store when you burn the fuel or respire. There are other types of energy store:

Energy to do with… Type of energy store

food, fuels, batteries chemical energy store

hot objects thermal energy store

moving objects kinetic energy store

position in a gravitational field gravitational potential energy store

changing shape, stretching, or squashing elastic energy store

Before and afterA camping stove burns gas, which is a fuel.

Before: After:

What we have

unburnt fuel, more oxygen

cold soup

less fuel, more carbon dioxide and waterhot soup (and slightly hotter air)

Thinking about energy

more energy in the chemical energy storeless energy in the thermal energy store

less energy in the chemical energy storemore energy in the thermal energy store

If you could measure the energy in the chemical and thermal energy stores you would see that:

total energy before = total energy after

B Name five types of energy store. Camping gas is a chemical store.

Energy is a bit like money.

Learning objectivesAfter this section you will be able to:

● use a model of energy transfer between stores to describe how jobs get done

● describe how the energy of an object depends on its speed, temperature, height, or whether it is stretched or compressed

● show how energy is transferred between energy stores in a range of real-life examples.

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Energy adds up3.2.1

Fantastic FactIf all the energy in the food that you eat was converted to energy in a thermal energy store, you would glow like a light bulb.

Summary Questions1 Copy and complete the

sentences below, choosing the correct bold words.

The law of conservation of energy says that energy cannot be created/transferred or destroyed/transferred. When you burn coal, you transfer energy from a chemical/thermal energy store to a chemical/thermal energy store. You can/cannot explain why things happen using energy. (5 marks)

2 Describe in terms of energy stores and transfers what happens when you:

a use a torch

b generate electricity using coal to run a cooker

c generate electricity using wind to run a motor. (6 marks)

3 Describe how the energy store of an object is linked to its speed, temperature, height, and compression. (1 mark)

4 Use the ideas on these two pages to explain in detail what energy transfers happen when you cook sausages on a camp fire burning wood. (6 marks)

Transferring energyElectric current, radiation (like light), waves (like sound), and heating are ways of transferring energy between stores. After you use your phone, there is less energy in the chemical energy store and more energy in the thermal energy store of the surroundings.

C State three ways that energy is transferred between stores.

Driving at a steady speedWhen you are driving along the motorway at 70 m.p.h. you might think that there is energy going into a kinetic energy store. If your speed is not changing, then the energy in the kinetic store is not changing either. Here is an analysis:

Before After

What we have

colder car and surroundings, more petrol and oxygen, less carbon dioxide and water

warmer car and surroundings, less petrol and oxygen, more carbon dioxide and water

Thinking about energy

more energy in the chemical energy store of the petrol and oxygenless energy in the thermal energy stores of the car and surroundings

less energy in the chemical energy store of the petrol and oxygenmore energy in the thermal energy stores of the car and surroundings

Bouncing a ballWhen you bounce a ball it doesn't bounce as high. What is happening in terms of energy?

Before After

What we have

ball lifted up, cooler ball and surroundings

ball at the top of the first bounce, warmer ball and surroundings

Thinking about energy

more energy in the gravitational potential energy store of the ballless energy in the thermal energy stores of the ball and surroundings

less energy in the gravitational potential energy store of the ballmore energy in the thermal energy stores of the ball and surroundings

law of conservation of energy, chemical energy store, thermal energy store, kinetic energy store, gravitational potential energy store, elastic energy store

Key Words

Remember those stores!Use the first letter of each of the stores in the table above to write a mnemonic to help you to remember them.

Cars on a motorway are heating the surroundings.

When a ball bounces, it heats the air and the ground.

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Big Idea: Energy 3

Topic 3.2 Energy transfer

You will learn more about energy transfers in Book 2, 3.4.2 Energy transfer: particles and Book 2, 3.4.3 Energy transfer: radiation and insulation.

Link

What does it mean to ‘save energy’? If energy is conserved, how can it be saved?

Wasting energyWhen you travel in a car you want the fuel that you burn to produce an increase in energy in the store that you want (your accelerating car), not in the energy store that you don’t (a hot engine).

The useful energy is in a kinetic energy store, and the wasted energy is in a thermal energy store.

A car engine gets very hot.

Here are two situations where energy transfers to both useful and wasted energy stores.

Situation Energy in this store decreases

Useful energy in this store increases

Wasted energy in this store increases

car accelerating

chemical energy store of the fuel (petrol) and oxygen

kinetic energy store of the accelerating car

thermal energy store of the surroundings

using a toaster

chemical energy store of the fuel (coal at power station) and oxygen

thermal energy store of the toast

thermal energy store of the surroundings

When you are driving a car, energy is transferred to the thermal store of the surroundings. The air or ground heats up a bit. That is not useful. You cannot transfer that energy to another store that you want it to go to, so it is effectively ’wasted’. In that case, scientists say that energy is dissipated.

A What does ‘dissipation’ mean?

Why is energy dissipated, and how can you reduce dissipation?In a car, you want all the energy in the chemical energy store of the fuel and oxygen to end up in the kinetic energy store. This does not happen because of the contact forces acting on the car. Air resistance

dissipation

Key Word

Fantastic FactWhen it comes back to Earth, air resistance from the atmosphere heats up the outside of a space vehicle to several thousand degrees Celsius.

Engineers have improved car design to reduce energy transferred to the surroundings.

Learning objectivesAfter this section you will be able to:

● describe what dissipation means

● calculate the useful energy and the amount dissipated, given values of input and output energy

● explain how energy is dissipated in a range of situations.

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Energy dissipation3.2.2

When you buy an appliance a label should tell you how efficient the appliance is.

A ball loses energy each time it bounces.

We say things ‘burn up’ in the atmosphere. We mean that the force of air resistance has a large heating effect. When bits of rock hit the atmosphere we see a meteor shower.

acts on the car as it moves through the air. Friction acts between engine parts and between the car and the road. These processes transfer energy to the thermal energy store of the surroundings.

B Name two ways to reduce dissipation in a car.

Energy is not just dissipated by contact forces.

● Friction between surfaces can make them vibrate, producing sound.

● When a current flows in a wire, the wire gets hot. This transfers energy to the thermal energy store of the surroundings. You can reduce the energy dissipated by reducing the resistance of the wires.

● When objects get hot, they transfer energy to anything around them that is at a lower temperature. You can reduce dissipation by using insulation.

What is efficiency?You can show how much energy is transferred usefully, and how much is wasted, using the idea of efficiency.

efficiency=

useful energy output × 100(%) energy input

For example, if the energy transferred from the chemical energy store of the fuel and oxygen in a car is 100 J and only 40 J is transferred to the kinetic energy store of the car, then the engine is 40% efficient.

The wasted energy, or energy dissipated = energy input – useful energy output

= 100 J – 40 J = 60 J

Wasting energyYou may have heard people say that it is important to save energy. But if energy is conserved, how can you save it? You aren’t really saving energy. You are saving fuel. There is less wasted energy, so you need to use less fuel to do the job that you want.

Summary Questions1 Copy and complete the sentences

below by choosing the correct words:

Energy can be transferred to the surroundings or to other places that we do not want by

, such as air resistance or . When this happens we say

that energy is wasted, or .

(3 marks)

2

a A kettle transfers 200 J of energy to the thermal energy store of the water in it for every 500 J of input energy. Calculate the wasted energy. (2 marks)

b Calculate the efficiency of the kettle. (2 marks)

3 Compare the conservation of energy and the dissipation of energy, and explain the link between the two. (6 marks) 51

Big Idea: Energy 3

Topic 3.2 Energy transfer

Energy costs ● There is energy associated with food and fuels. Energy is measured in

joules, J. ● Fossil fuels are non-renewable energy resources used for heating,

transportation, and generating electricity. ● Renewable energy resources can also be used to generate electricity. ● Power tells you how quickly energy is transferred by a device. You can

calculate power using the formula: power (W) = energy (J)time (s)

.

● You can work out the cost of the energy transferred by appliances in your home using the formula: cost = power (kW) x time (hours) x price (kWh). Energy companies use the unit of kilowatt hours.

Energy transfer ● Energy cannot be created or destroyed, it can only be transferred between stores. This is

the law of conservation of energy. An energy store is a way of keeping track of energy. ● Radiation (like light), heating, forces, and electricity are ways of transferring energy

between stores. ● Energy is dissipated in any energy transfer process because of friction, air resistance,

electrical resistance, and heating of the surroundings by hot objects. ● You can calculate the useful energy or the wasted energy from the energy input and energy

output.

Key Points

Energy campaign

You are a local councillor who wants to raise awareness of energy issues

in schools.

There are two parts to the campaign:

● raising awareness of the energy content of food and how that links to the energy

needed for activities that people do

● saving fossil fuels for the future.

Taska Design an energy diary that students could use to take a snapshot of their own

energy use over a day or a week.

b Write an article for the school newspaper that explains the link between closing

doors or insulating buildings, cost, and fossil fuel use.

BIG Write

energy, joules, kilojoules, energy resources, fossil fuels, non-renewable, renewable, watts, power, kilowatts, kilowatt hours, law of conservation of energy, chemical energy store, dissipated

Key Words

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3 Energy: Summary

1 Here are some energy resources. List the renewable energy resources.

wind solar oil coal geothermal gas(1 mark)

2

a Write the letter of the correct definition of power below. (1 mark)A the energy transferred per kilogramB the energy transferredC the energy transferred per secondD the force over a distance

b Select all the units of power from this list:

kW J watts kilojoules kilowatts W joules kJ(1 mark)

(2 marks)3

a Explain, in terms of energy, why a pendulum swings lower and lower when you let it go. (2 marks)

b Describe an everyday situation where energy is dissipated by friction. (1 mark)

(3 marks)4

a Name a fossil fuel that can be burned in a power station. (1 mark)

b Explain why it is called a ‘fossil’ fuel. (1 mark)c Use your answer to part b to explain why

fossil fuels are non-renewable. (2 marks)(4 marks)

5 A tablet charger has a power of 100 W.a Convert 100 W to kW. There are 1000 W in

1 kW. (1 mark)b Calculate the cost of using the charger for

3 hours if the cost of 1 kWh is 10 p. (2 marks)

c State and explain one way of reducing the costs on your home energy bill. (2 marks)

(5 marks)

6 You want to reduce your energy bills.a Calculate the power of a lightbulb that

transfers 6000 J every minute. (2 marks)b Two bulbs are equally bright. State and

explain which lightbulb you should use. (2 marks)

c State and explain one way of reducing the costs on your home energy bill. (2 marks)

(6 marks)

7 A tennis ball has 0.5 J of energy when it is 1 m above the floor.a Name the store associated with this

energy. (1 mark)b A student states that there will be 0.5 J of

energy in the kinetic store just before it hits the ground.i Explain why the student has made that

statement. (1 mark)ii Explain why the student might not be

correct. (1 mark)c Explain why the ball moves. (2 marks)

(5 marks)

8 Here are some data about two types of kettle.

Kettle Energy input(kJ)

Useful energy output

(kJ)

Wasted energy

(kJ)

BoilFast 600 540

KettlePro 800 80

a Copy and complete the table. (2 marks)b Calculate the efficiency of each kettle.

(4 marks)c A student says that the BoilFast kettle

must be more efficient because it wastes less energy. Explain why this is not correct. (2 marks)

(8 marks)

End-of-Big Idea questions

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