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GCSE Physics · GCSEChapter 4 · Energy resources and the global energy supply
GCSE · Chapter 4

Energy resources and the global energy supply

By the end of this chapter you will be able to

  • Say whether a resource is renewable or non-renewable, and give an example
  • Explain how a power station or renewable device makes electricity
  • Compare two resources in a table, using reliability, cost and environmental impact
  • Use a percentage energy mix to calculate the energy from each source
  • Evaluate a choice of energy resource for a town, and say why conserving energy matters

You should already know

  • Energy stores and transfers (Chapter 1)
  • Efficiency and percentages (Chapter 2)

Where this leads

  • Nuclear fission and fusion (Chapter 12)
  • Electromagnetic induction and generators (Chapter 20)

GCSE Physics. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Distinguish renewable and non-renewable energy resources, Describe fossil fuels, nuclear fission and biofuels as energy resources, Describe wind, hydroelectric, solar, geothermal, tidal and wave energy and how each produces electricity, Compare energy resources on reliability, cost and environmental impact, Read and calculate from the energy mix of a town or a country, and discuss energy security and conservation.

Exercise P  Do you remember?

1
FWhat is 40% of 5000? Write the number.
2
FWhich store holds energy in the food we eat? Write the word.
3
FName the transfer when a solar panel gives out electricity to a lamp. Write the word.
4
FA machine has 200 J in and 150 J useful. What is its efficiency as a percentage? Write the number.
5
FWhat word means a resource that can be replaced in a human lifetime? Write the word.
4.1

Renewable and non-renewable resources

GCSE
Distinguish renewable and non-renewable energy resources
Video lesson: Renewable and non-renewable resourcesComing soon
Context. Priya’s school is discussing where the town’s electricity should come from in ten years. “Some sources will run out,” says her teacher. “Others will not.” To decide, we need to know the difference between a renewable and a non-renewable energy resource.

An energy resource is a source of energy that we can use. A non-renewable resource is used up faster than it is made, so it will run out. A renewable resource is replaced naturally and will not run out in a human lifetime, such as sunlight, wind and water. Renewable resources do not run out, but they may not be available all the time.

ResourceRenewable?How it makes energy (short)Main drawback
coalnoburn coal to heat water and make steamreleases carbon dioxide and pollutes the air
oil and gasnoburn fuel to heat water or to power enginesreleases carbon dioxide; supplies can run out
nuclear fissionnofission of uranium heats water to make steamradioactive waste; high build cost
biofuelsyesburn or process plant materialuses land; can compete with food crops
windyesturbines turn wind energy into electricitydepends on the weather; visual impact
hydroelectricyesfalling water turns turbinesneeds suitable sites; can harm habitats
solaryespanels turn light or heat into electricity or hot wateronly works in daylight; panels are costly
geothermalyesheat from hot rocks warms wateronly in places with hot rocks near the surface
tidalyestides turn turbinesfew suitable sites; affects wildlife
waveyeswaves move machines that make electricityrough sea damages devices; few sites
Some energy resources, whether they are renewable, and their main drawback

Key ideas

  • Non-renewable: coal, oil, gas, nuclear fuel (uranium). They will run out.
  • Renewable: wind, water, solar, geothermal, tides, waves and biofuels. They are replaced naturally.
  • A renewable resource is not always reliable, even though it does not run out.
  • Biofuels come from plants, which are grown again, so they count as renewable.
Worked example 4.1.1
Which of these is a non-renewable resource: wind, coal or solar? Write the word.

Method. Check each resource against the definition.

  1. Wind. Wind is replaced by the weather, so it is renewable.
    renewable
  2. Coal. Coal takes millions of years to form, so it is used faster than it is made.
    non-renewable
  3. Solar. Sunlight is replaced every day, so it is renewable.
    renewable
  4. Write the answer.
    coal

Check. Only coal is non-renewable of the three. ✓

Worked example 4.1.2
Is a hydroelectric dam powered by a renewable resource? Write yes or no.

Method. Think about where the energy comes from.

  1. Source. The energy comes from water flowing downhill, which is replenished by rain.
    water replenished
  2. Decide. Water is replaced naturally, so the resource is renewable.
    renewable
  3. Write the answer.
    yes

Check. The rain comes from the Sun’s energy. ✓

Worked example 4.1.3
Name one renewable resource that depends on the Sun, and one that depends on the Moon. Write two words.

Method. Think about what each resource depends on.

  1. Sun. Solar energy depends on the Sun, and wind depends on the Sun heating the air.
    solar
  2. Moon. Tidal energy depends mainly on the pull of the Moon.
    tidal, Moon
  3. Write the answer.
    solar, tidal

Check. Other answers are possible, such as wind for the Sun. ✓

Watch out

Watch out: “renewable” does not mean “always available”. Wind and solar are renewable, but they depend on the weather and the time of day.

Exam tip

Exam tip. When asked to define renewable, use the words “replaced naturally” or “will not run out”.

Exercise 4A  Renewable and non-renewable

1
FName a non-renewable fossil fuel. Write the word.
2
FName a renewable resource that uses flowing water. Write the word.
3
FName a non-renewable resource that releases energy by fission. Write the word.
4
FIs solar energy renewable? Write yes or no.
5
FIs coal renewable? Write yes or no.
6
FWhich resource is replenished by the water cycle? Write the word.
7
PSWrite two renewable resources in the table that do not depend on the weather. Write two names.
8
RExplain why biofuels are called renewable, in one sentence. Accept any sentence that says plants are grown again, so the fuel is replaced.
9
RA pupil says “all renewable energy is always available.” Explain why this is wrong. Accept any answer that says renewable energy depends on weather or time of day, so it is not always available.
10
PSSort these into renewable and non-renewable: wind, gas, tidal, uranium. Write the two lists as words separated by commas: renewable first, then non-renewable.
11
PSHow many of the ten resources in the table are renewable? Write the number. (Count the rows marked yes.)
12
RIn one sentence, explain why a country should use a mix of renewable and non-renewable resources. Accept any sentence that says a mix gives security of supply and lets renewables cover gaps when the weather is poor.
13
PSWhich non-renewable fossil fuel is commonly burned in power stations to heat water to make steam? Write the word.
14
RExplain why uranium is said to be non-renewable, in one sentence. Accept any sentence that says uranium is mined from the Earth and cannot be replaced at the rate it is used.
4.2

Fossil fuels, nuclear fission and biofuels

GCSE
Describe fossil fuels, nuclear fission and biofuels as energy resources
Video lesson: Fossil fuels, nuclear fission and biofuelsComing soon
Context. Tom visits a power station with a cooling tower. “What is the fuel?” he asks. The guide explains that the fuel heats water to make steam, and the steam turns a turbine. The fuel may be a fossil fuel, a nuclear fuel or a biofuel, but the basic process of turning a turbine is the same.

Fossil fuels (coal, oil and natural gas) formed from the remains of ancient plants and animals over millions of years. When they burn, they release energy, and carbon dioxide, which adds to global warming. Nuclear fission splits large uranium nuclei and releases energy as heat; it produces very little carbon dioxide but leaves radioactive waste. Biofuels come from plant or animal material, which can be grown again.

Key ideas

  • A power station heats water to make steam; the steam turns a turbine, which turns a generator.
  • Fossil fuels release carbon dioxide when burned, which adds to global warming.
  • Nuclear fission releases heat with very little carbon dioxide, but produces radioactive waste.
  • Biofuels are renewable, but growing them can use land needed for food.
Worked example 4.2.1
A coal power station uses coal to heat water. Name the energy transfer from the coal to the water. Write the word.

Method. Think about how the coal heats the water.

  1. Fuel. The coal is burned, releasing energy from its chemical store.
    chemical store
  2. Look. The burning coal transfers energy to the water, which becomes hot.
    heating
  3. Name. Energy moving by heating is heating.
    heating
  4. Write the answer.
    heating

Check. The steam then moves the turbine by a mechanical transfer. ✓

Worked example 4.2.2
Which of these releases carbon dioxide when burned: coal, nuclear fuel or wood from a managed forest? Write the two words that release carbon dioxide, separated by a comma: fossil fuel first, then the biofuel.

Method. Think about which resources release carbon dioxide on burning.

  1. Fossil. Coal releases carbon dioxide when burned.
    coal: CO2
  2. Biofuel. Wood from a managed forest also releases carbon dioxide, but the trees are grown again.
    wood: CO2 but replaced
  3. Write the answer.
    coal, wood

Check. Nuclear fission produces very little carbon dioxide. ✓

Worked example 4.2.3
Name the process in a nuclear power station that releases heat, when a large uranium nucleus splits. Write the word.

Method. Recall the name of the process.

  1. Look. A large uranium nucleus is hit by a neutron and splits into smaller nuclei.
    splits
  2. Recall. When a large nucleus splits into smaller nuclei, it is called fission.
    fission
  3. Write the answer.
    fission

Check. Fusion is the joining of small nuclei, and is not used in power stations yet. ✓

Watch out

Watch out: a nuclear power station does not burn uranium. It splits uranium atoms by fission, and the heat is used to make steam.

Exam tip

Exam tip. When you compare fossil fuels and nuclear, mention carbon dioxide and radioactive waste. These are the two key points.

Exercise 4B  Fossil fuels, nuclear fission and biofuels

1
FWhich fossil fuel is a gas? Write the word.
2
FWhat is released when a fossil fuel burns that adds to global warming? Write the name of the gas.
3
FWhat is left over from nuclear power that is dangerous for many years? Write the word.
4
FWhat do nuclear power stations use to heat water to make steam? Write the word.
5
FName a renewable fuel made from plant material. Write the word.
6
RExplain why fossil fuels are described as non-renewable, in one sentence. Accept any sentence that says they took millions of years to form and are used much faster than they are made.
7
PSIn a coal power station the steam turns a turbine. Name the device that the turbine turns to make electricity. Write the word.
8
PSA power station uses fossil fuels. Give the chain of energy transfers from the chemical store of the fuel to the electricity. Write the transfers in order, as words separated by commas.
9
RExplain why burning wood from a managed forest is often said to be carbon neutral. Accept any answer that says the trees take in carbon dioxide as they grow, to replace the carbon dioxide released.
10
RGive one disadvantage of using biofuels, in one sentence. Accept any sentence that says biofuels can use land that is needed to grow food.
11
PSWhich two resources produce carbon dioxide when they are burned? Write two words, separated by a comma: a fossil fuel and a biofuel.
12
RA nuclear power station produces 1000 MWh of electricity, and a coal power station produces the same amount, but the coal station gives out 800 tonnes of carbon dioxide. Explain why the nuclear station is considered to give less carbon dioxide. Accept any answer that says nuclear fission releases very little carbon dioxide.
4.3

Renewable sources that make electricity

GCSE
Describe wind, hydroelectric, solar, geothermal, tidal and wave energy and how each produces electricity
Video lesson: Renewable sources that make electricityComing soon
Context. On a windy day, a field of turbines turns steadily. Next to it, a hydroelectric dam holds back a lake. Both make electricity, but they use very different energy sources.

Each renewable source turns a turbine or drives a generator: wind turbines are turned by moving air; hydroelectric stations are turned by falling water; tidal turbines are turned by moving tides; wave devices are moved by waves. Solar panels turn light into electricity (photovoltaic), or heat water (solar thermal). Geothermal systems pump water into hot rock, and use the steam or hot water to make electricity or heat buildings.

Share of electricity: example figures051015202530windsolarhydrootherrenewable sourcepercent
Example figures for the share of electricity from renewable sources

Key ideas

  • Wind: kinetic energy of moving air turns turbines.
  • Hydroelectric: the gravitational potential store of water turns turbines.
  • Solar: light (photovoltaic) or heat (solar thermal) from the Sun.
  • Geothermal: thermal energy from hot rocks inside the Earth.
  • Tidal and wave: the movement of the sea is converted to electricity.
Worked example 4.3.1
In a hydroelectric station, water is stored high in a reservoir. Name the energy store of the water before it flows. Write the word.

Method. Think about the height of the water.

  1. Where. The water is held in a reservoir high above the turbine.
    reservoir
  2. Look. The water is high above the turbine, so it has energy from its height.
    height
  3. Name. Energy stored because of height is the gravitational potential store.
    gravitational potential
  4. Write the answer.
    gravitational potential

Check. As it falls, the store becomes kinetic. ✓

Worked example 4.3.2
Name the energy store that a wind turbine takes its energy from. Write the word.

Method. Think about what the wind does.

  1. Look. Moving air has energy because it is moving.
    moving air
  2. Name. Energy in a moving object is the kinetic store.
    kinetic
  3. Write the answer.
    kinetic

Check. The turbine transfers the kinetic energy mechanically. ✓

Worked example 4.3.3
Which renewable resource uses the heat from rocks deep underground? Write the word.

Method. Recall the renewable source that uses the Earth’s heat.

  1. Look. The heat is stored in hot rocks below the ground, not at the surface.
    below ground
  2. Recall. Geothermal energy uses heat from hot rocks below the ground.
    geothermal
  3. Write the answer.
    geothermal

Check. Geothermal heat comes from radioactive decay and the Earth’s original heat. ✓

Watch out

Watch out: solar panels do not turn heat into electricity directly in a photovoltaic panel; they turn light into electricity. Solar thermal panels heat water, not electricity.

Exam tip

Exam tip. For each renewable source, name the store it comes from (kinetic, gravitational potential, light, thermal) and the device that turns it into electricity.

Exercise 4C  How renewable sources make electricity

1
FWhich renewable source uses moving air to turn a turbine? Write the word.
2
FWhich renewable source uses water stored in a reservoir? Write the word.
3
FWhich renewable source uses the rise and fall of the sea to make electricity? Write the word.
4
FWhich renewable source uses light to make electricity? Write the word.
5
FWhich renewable source uses hot water or steam from underground? Write the word.
6
FName the energy store of the water in a reservoir, before it flows through a turbine. Write the word.
7
RIn a wave device, the energy transfer to the device is mechanical. Explain why, in one sentence. Accept any sentence that says the waves push and move the device, which is a force doing work.
8
PSA solar thermal panel warms water. Name the transfer from the Sun to the water. Write the word.
9
RGive one reason why geothermal energy is not used everywhere. Accept any answer that says hot rocks are needed close to the surface, which is only in some places.
10
PSA hydroelectric dam holds water 40 m above the turbine. Using E = m g h for 1 kg of water, calculate the gravitational potential energy of 1 kg of water. Write the number of joules.
11
RA wind turbine turns the kinetic energy of the air into electricity. Describe the energy transfers from moving air to the electricity, in order. Accept any answer that says the air transfers energy mechanically to the blades, which turn a generator, which makes electricity.
12
PSWhich source in this list depends mainly on the pull of the Moon: wind, tidal, geothermal or hydroelectric? Write the word.
13
RExplain why a wave energy device needs to be strong, in one sentence. Accept any sentence that says the sea can damage the device, so it must be strong to survive.
4.4

Comparing resources and calculating the energy mix

GCSE
Compare energy resources on reliability, cost and environmental impact, Read and calculate from the energy mix of a town or a country
Video lesson: Comparing resources and calculating the energy mixComing soon
Context. Mr Hughes is on the town council. The council must choose how to make the town’s electricity. He has a table of options and a pie chart of the current mix. To decide, he compares reliability, cost and environmental impact, and he calculates how much electricity each source gives.

When we compare energy resources, we consider: reliability (can it supply energy when needed?), cost (to build and run), and environmental impact (carbon dioxide, waste, land and habitats). An energy mix uses several sources, so that a shortage of one can be made up by another.

QualityWindSolar (panels)Gas power stationNuclear
reliable all the time?no (weather)no (night, cloud)yesyes
carbon dioxide while runningnonenonesomevery little
build costmediummediumlow to mediumvery high
radioactive wastenononoyes
can be switched on quicklynonoyesno
Comparing four ways of making electricity (general comparison)
SourceShare of the townEnergy in MWh (total 5000 MWh)
Wind40%2000 MWh
Solar10%500 MWh
Gas35%1750 MWh
Coal5%250 MWh
Nuclear10%500 MWh
Example energy mix for a town that uses 5000 MWh in a year: 1 MWh = 1 megawatt-hour

Key ideas

  • Energy from a source = percentage share x total energy / 100.
  • Reliability: can the source be switched on when needed?
  • Environmental impact includes carbon dioxide, waste, land use and habitats.
  • A good energy mix balances reliability, cost and impact.
Worked example 4.4.1
The town uses 5000 MWh. Wind provides 40%. Calculate the energy from wind. Write the number of MWh.

Method. Find 40% of 5000.

  1. Convert. 40% = 0.4.
    0.4
  2. Multiply. Energy = 0.4 x 5000 = 2000 MWh.
    0.4 x 5000 = 2000
  3. Write the answer.
    2000 MWh

Check. 2000 / 5000 = 0.4 = 40%. ✓

Worked example 4.4.2
The gas share of the town is 35%. Calculate the energy from gas. Write the number of MWh.

Method. Find 35% of 5000.

  1. Convert. 35% = 0.35.
    0.35
  2. Multiply. Energy = 0.35 x 5000 = 1750 MWh.
    0.35 x 5000 = 1750
  3. Write the answer.
    1750 MWh

Check. 1750 / 5000 = 0.35. ✓

Worked example 4.4.3
Which is more reliable: a wind farm or a gas power station? Write wind or gas.

Method. Think about when each can make electricity.

  1. Wind. A wind farm depends on the weather, so it is not always available.
    depends on weather
  2. Gas. A gas power station can be switched on when needed.
    switched on
  3. Write the answer.
    gas

Check. Reliability is about supply on demand. ✓

Watch out

Watch out: percentages must be applied to the total, not to another source. Use the total energy in the question each time.

Exam tip

Exam tip. When you compare two sources, use the three headings: reliability, cost and environmental impact. Use one sentence for each.

Exercise 4D  Comparing and calculating

1
FCalculate the energy from solar in the example town, which provides 10%. Write the number of MWh.
2
FCalculate the energy from coal in the example town, which provides 5%. Write the number of MWh.
3
FCalculate the energy from nuclear in the example town, which provides 10%. Write the number of MWh.
4
FAdd the percentages in the example town mix. Write the total as a number.
5
FIn the example mix, which source gives the largest share? Write the word.
6
PSIn the example mix, how much energy comes from renewable sources (wind and solar together)? Write the number of MWh.
7
PSIn the example mix, the town needs more electricity on a still, cloudy night. Which source in the mix is least affected by this? Write the word.
8
PSA town uses 800 MWh of electricity in a month and gets 25% of it from wind. How much does the wind provide? Write the number of MWh.
9
PSCompare wind and gas on carbon dioxide while they are running. Write which one gives out more carbon dioxide: wind or gas.
10
RNuclear is the most expensive to build in the table, but it gives out very little carbon dioxide. Explain why a council might still choose nuclear. Accept any answer that says it is reliable all the time and has low carbon dioxide emissions.
11
REvaluate the claim: “wind is the best choice for a town because it is free to run.” Give one point for and one against. Accept any answer that says wind has no fuel cost, but it depends on the weather so it is not reliable on its own.
12
RA town chooses an energy mix with a larger share of wind and a smaller share of gas. Give the environmental advantage in one sentence. Accept any sentence that says the mix gives out less carbon dioxide.
4.5

Energy security and conserving energy

GCSE
Read and calculate from the energy mix of a town or a country, and discuss energy security and conservation
Video lesson: Energy security and conserving energyComing soon
Context. A country buys most of its gas from another country. When prices rise, electricity bills go up. “Can we rely on that?” a pupil asks. This is a question about energy security: a country needs a reliable supply that it can afford.

Energy security means having a reliable supply of energy that the country can afford, without depending on a single source or a single country. A varied mix of sources, and home-grown renewables, help to improve energy security. Conserving energy means using less energy, for example by insulating houses, using efficient appliances and turning off lights, so that less energy needs to be supplied.

Key ideas

  • Energy security: a reliable, affordable supply.
  • A varied mix of sources reduces the risk if one source fails.
  • Conserving energy means using less, for example with insulation and efficient appliances.
  • Using less energy reduces the need for new power stations and reduces emissions.
Worked example 4.5.1
Give one way a household can conserve energy, in one sentence. Accept any sentence that names a method, such as insulating the loft or turning off lights.

Method. Think about a change in the home.

  1. Where. Most of the heat in a house is lost through the roof and walls.
    roof and walls
  2. Method. Loft insulation reduces the heat lost through the roof.
    insulation
  3. Write the answer.
    Accept any sentence that names a method, such as insulating the loft or turning off lights.

Check. Any method that reduces energy use is correct. ✓

Worked example 4.5.2
A country gets 60% of its electricity from one fuel. Explain why this is a risk to energy security, in one sentence. Accept any sentence that says the country would be badly affected if that fuel became expensive or hard to get.

Method. Think about a single source.

  1. Risk. If that fuel becomes expensive or the supply is cut, the electricity supply is affected.
    risk
  2. Link. A varied mix reduces this risk.
    varied mix
  3. Write the answer.
    Accept any sentence that says the country would be badly affected if that fuel became expensive or hard to get.

Check. ✓

Worked example 4.5.3
Give one reason why a range of energy sources improves a country’s energy security, in one sentence. Accept any sentence that says it reduces the risk if one supply is cut or its price rises.

Method. Think about what happens if one source fails.

  1. Risk. If one source fails, the others can keep supplying energy.
    others
  2. Security. So the range of sources reduces the risk to the country.
    reduces risk
  3. Write the answer.
    Accept any sentence that says it reduces the risk if one supply is cut or its price rises.

Check. ✓

Watch out

Watch out: conserving energy and energy security are not the same. Conservation means using less; security means a reliable supply. Both help a country.

Exam tip

Exam tip. For an evaluation question, give a benefit and a drawback, then a conclusion that says which is better and why.

Exercise 4E  Security, conservation and evaluation

1
FWhat word means having a reliable, affordable supply of energy? Write the phrase.
2
FName a way to conserve energy in the home. Write the word or phrase.
3
FWhich is a benefit of using a varied mix of energy sources? Write one word: reliable or expensive.
4
FName a device that uses less energy for the same job. Write the name.
5
RExplain why using less energy can reduce the need for new power stations, in one sentence. Accept any sentence that says less energy demand means less new capacity is needed.
6
PSA country uses 1000 units of energy. It reduces use by 15% through insulation. How many units does it save? Write the number.
7
PSA country has 1000 units of energy use and 60% comes from one fuel. How many units come from this fuel? Write the number.
8
PSTwo countries have the same total energy use. Country A gets 60% from one fuel. Country B gets 25% from one fuel. Which has the greater risk to energy security? Write A or B.
9
REvaluate: “a country should build only renewable power stations to be secure.” Give one reason for and one reason against. Accept any answer that gives a reason for, such as no emissions, and one against, such as the lack of reliability when the weather is poor.
10
RGive one reason why a country might import its energy, and one risk of doing so. Accept any answer that gives a reason such as cheaper fuel, and a risk such as prices or supply being controlled by others.
11
PSIn a town, the energy use falls from 5000 MWh to 4000 MWh after an insulation scheme. Calculate the percentage reduction. Write the number of percent.
12
RExplain in one sentence how a town can improve energy security and reduce emissions at the same time. Accept any sentence that says it can use renewables and conserve energy, which both reduce the need for fossil fuel.

Chapter summary

SkillMethod
Classify a resourceRenewable: replaced naturally; non-renewable: used up faster than made
Name how a source makes electricityTurbines turned by wind, water, tides, waves, steam from fuel or heat
Compare resourcesUse reliability, cost and environmental impact, one sentence each
Calculate the energy mixEnergy = percentage / 100 x total
Discuss security and conservationA varied mix improves security; conservation reduces demand

Can you…?

  • I can say whether a resource is renewable or non-renewable
  • I can describe how a source makes electricity
  • I can compare two resources using three headings
  • I can calculate a share of an energy mix
  • I can explain energy security and how conservation helps

Key terms

renewable
a resource that is replaced naturally and will not run out in a human lifetime
non-renewable
a resource that is used up faster than it is made
fossil fuel
coal, oil or natural gas, formed from ancient plants and animals
biofuel
a fuel made from plant or animal material
energy mix
the different sources used to supply the energy needed
energy security
a reliable and affordable supply of energy
reliability
whether a source can supply energy when it is needed

Exercise 4Z  Check-up

1
Name a renewable source that uses the heat of rocks underground. Write the word.
2
Name a non-renewable fuel that releases energy by fission. Write the word.
3
What gas is released when fossil fuels burn, adding to global warming? Write the name.
4
Which resource is renewable and uses the movement of the sea? Write the word.
5
Calculate 30% of 2000. Write the number.
6
A town uses 4000 MWh. Wind gives 25%. How much does the wind give? Write the number of MWh.
7
Name the energy store of water held high in a reservoir. Write the words.
8
Explain why wind is not always reliable. Write one reason in one sentence. Accept any sentence that says the wind changes with the weather.
9
Give one benefit of conserving energy. Accept any sentence that says it reduces the energy bill or the emissions or the need for new power stations.
10
Write the word that describes a resource replaced naturally in a human lifetime. Write the word.

Total 29 marks. Allow about 29 minutes.

Exercise 4X  Exam-style questions

1
FName one renewable source and one non-renewable source of electricity. Write two words, separated by a comma: renewable first.[2 marks]
2
FA town uses 5000 MWh. Solar gives 10%. Calculate the energy from solar. Write the number of MWh.[2 marks]
3
RExplain why hydroelectric power is renewable. Accept any answer that says rain replaces the water, which is replenished by the water cycle.[2 marks]
4
RGive two disadvantages of burning fossil fuels for electricity. Accept any two of: carbon dioxide emissions, global warming, air pollution, and fuel running out.[2 marks]
5
RDescribe how a tidal barrage makes electricity, in order. Accept any answer that says the tide fills and empties a basin, water flows through a turbine, and the turbine turns a generator.[3 marks]
6
PSA town uses 8000 MWh. The mix is 35% gas, 25% wind, 30% nuclear and 10% solar. Calculate the energy from nuclear and the energy from solar together. Write the number of MWh.[3 marks]
7
RCompare wind power and nuclear power on reliability, carbon dioxide and waste. Accept any answer that says wind is less reliable, gives no carbon dioxide while running, and produces no radioactive waste; nuclear is reliable, gives very little carbon dioxide and produces radioactive waste.[4 marks]
8
REvaluate the claim that a country should move all its electricity to solar power. Give one strength and one weakness, and a conclusion. Accept any answer that gives low emissions as a strength, and night-time and winter supply as a weakness, with a conclusion that backup or a mix is needed.[4 marks]
9
RA council wants to reduce its energy use by 25% and become more secure. Describe two actions it could take and explain how each helps. Accept any two sensible actions, such as insulation or efficient lighting, and renewable sources, each with a link to security or saving.[5 marks]
10
RDescribe one advantage and one disadvantage of geothermal energy. Accept any answer: advantage, it is renewable and needs no fuel; disadvantage, it only works where hot rocks are near the surface.[2 marks]
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