National and global energy resources – GCSE Physics exam questions with mark scheme

1Grade 1–3Foundation3 marks

(a) Name two renewable energy resources other than wind. [2]

(b) Give one reason why wind turbines cannot be relied on to meet demand for electricity at all times. [1]

(a) any one from: solar / the Sun; hydroelectric; tidal; (water) waves; geothermal; bio-fuel allow biomass / wood; do not accept 'water' alone; reject nuclear, coal, oil, gas(1)
(a) a second, different resource from the list tidal and wave are different resources(1)
(b) the wind does not always blow / wind speed varies allow not available when wind speed is too low or too high; allow output cannot be increased when demand rises(1)
Answer: (a) e.g. solar, tidal (b) wind does not always blow
Examiner tip: Nuclear is not renewable — it is a common wrong answer in (a).

2Grade 4–54 marks

A town's electricity could be generated by a gas-fired power station or by a wind farm.

Compare the advantages and disadvantages of using a gas-fired power station rather than a wind farm. [4]

gas is non-renewable / will run out, whereas wind is renewable(1)
burning gas releases carbon dioxide (contributing to global warming / climate change); wind farms do not produce CO₂ when generating(1)
a gas power station is reliable / can be started quickly to meet demand; wind farms depend on the weather(1)
any one further valid comparison, e.g. wind farms cause visual / noise pollution (or harm birds) but a gas power station does not; gas has ongoing fuel costs whereas the wind is free; a wind farm needs a much larger area of land for the same output; burning gas releases other pollutants (e.g. nitrogen oxides) whereas wind does not if any of the three points above is not made, further valid comparisons from this list can be credited in its place (max 4 overall). Do not award this mark again for a second reliability or CO₂ point already credited above. A comparison may be made with comparative wording instead of naming both sides (e.g. 'gas is more reliable than wind', 'a wind farm needs more land'). An answer that only describes one resource scores max 2. For 4 marks there must be at least one advantage and one disadvantage of gas.(1)
Answer: Gas: reliable, fast start-up, but non-renewable and emits CO₂. Wind: renewable, no CO₂ when operating, but unreliable and visual/noise impact.
Examiner tip: 'Compare' needs both sides of each point — a list about gas only caps you at 2 marks.

3Grade 1–3Foundation3 marks

(a) Complete the sentence.

A renewable energy resource is one that ____________________________ . [1]

(b) Which two of the following are non-renewable energy resources?

Tick (✓) two boxes.

geothermal	☐
nuclear fuel	☐
oil	☐
tides	☐

[2]

(a) is (being) replenished as it is used allow can be replaced / renewed as fast as it is used; allow will not run out; ignore 'can be reused' / 'can be recycled'; do not accept 'is natural' or 'is clean' alone(1)
(b) nuclear fuel ticked(1)
(b) oil ticked if more than two boxes are ticked, deduct one mark for each extra box ticked (minimum 0)(1)
Answer: (a) can be replenished as it is used; (b) nuclear fuel and oil
Examiner tip: Nuclear fuel is the classic trap: it releases no CO₂ when generating, but uranium is mined and will run out, so it is non-renewable.

4Grade 1–3Foundation3 marks

Energy resources are used for transport, for heating and for generating electricity.

(a) Which energy resource provides most of the energy used for transport by cars, lorries and aircraft?

Tick (✓) one box.

coal	☐
geothermal	☐
nuclear fuel	☐
oil	☐

[1]

(b) Some cars can run on bio-fuel made from crops instead of petrol.

Give one reason why bio-fuel is described as a renewable energy resource. [1]

Name one renewable energy resource that could be used to heat a home instead. [1]

(a) oil more than one box ticked scores 0(1)
(b) the crops / plants can be regrown (each year) allow it can be replenished / replaced as fast as it is used; allow it is made from plants that can be grown again; ignore 'it will not run out' unless linked to regrowing; do not accept 'it is better for the environment' or 'it does not produce carbon dioxide'(1)
(c) any one from: the Sun / solar (water heating); geothermal; bio-fuel / wood / biomass allow electricity generated from a named renewable resource, e.g. wind; do not accept 'electricity' alone; do not accept nuclear or any fossil fuel(1)
Answer: (a) oil; (b) the crops it is made from can be regrown; (c) e.g. solar water heating / geothermal / burning wood
Examiner tip: For (b), 'it doesn't release CO₂' is wrong and not the definition: renewable means the resource is replenished, e.g. the crops regrow.

5Grade 4–56 marks

The table shows the percentage of a country's electricity generated from different energy resources in three different years.

Energy resource	2005	2015	2025
coal	34	22	2
gas	38	32	35
nuclear fuel	20	21	15
wind	1	10	28
the Sun (solar)	0	2	6
hydro-electricity and bio-fuel	7	13	14

(a) Calculate the percentage of the country's electricity generated from renewable energy resources in 2025. [2]

(b) Describe the trend in the use of coal between 2005 and 2025. [1]

(d) In 2025 wind generated 28% of the country's electricity, but the percentage from gas was almost the same as in 2005.

Suggest why the country still needs gas-fired power stations. [1]

(a) wind, solar and hydro-electricity/bio-fuel values used: 28 + 6 + 14 do not award if nuclear (15) is included(1)
(a) 48 (%) an answer of 63 (nuclear included) scores 0; an answer of 34 (hydro-electricity and bio-fuel left out) scores 0(1)
(b) (the percentage generated from) coal decreased (from 34% to 2%) allow coal is used much less / is (almost) no longer used; allow 'went down by 32 (percentage points)'; a change of 32 with no direction stated does not score(1)
(c) any two from: burning coal releases (large amounts of) carbon dioxide, which contributes to global warming / climate change; burning coal releases sulfur dioxide, which causes acid rain (or other named pollutant, e.g. particulates); government targets / laws / taxes to reduce carbon emissions; replaced by renewable resources (e.g. wind) which have become cheaper / more available; coal reserves are running out / coal mines have closed first mark for one reason(1)
(c) second, different reason from the list two answers about CO₂ / global warming score 1 only(1)
(d) wind is unreliable / the wind does not always blow, so gas power stations are needed to meet demand allow gas power stations can be started up quickly / output can be increased quickly when demand rises; allow (wind and solar) supply varies with the weather; do not accept 'gas is cheaper' alone(1)
Answer: (a) 48%; (b) decreased from 34% to 2%; (c) e.g. CO₂ from burning coal causes global warming; renewables became cheaper; (d) wind is unreliable, gas can be started quickly to meet demand
Examiner tip: Nuclear fuel is low-carbon but NOT renewable, so it must be left out of the total in (a).

6Grade 4–54 marks

A tidal barrage is a dam built across a river estuary. It generates electricity as the tide flows in and out.

(a) Explain why a tidal barrage is a more reliable source of electricity than a wind farm. [2]

(b) Give one environmental impact of building a tidal barrage across an estuary. [1]

(a) tides happen (at least) twice every day / the times and heights of tides are predictable allow tides always happen; allow tides are caused by the Moon so are predictable(1)
(a) wind speed varies / the wind does not always blow (so output of a wind farm is unpredictable) a comparison is needed for 2 marks; 'tides are reliable' alone does not score(1)
(b) any one from: destroys / changes habitats (of wildlife / birds / fish) in the estuary; mud flats are covered so wading birds lose feeding grounds; blocks the movement of fish / boats; visual impact / spoils the view of the estuary ignore 'causes pollution' unqualified; do not accept 'releases carbon dioxide' when generating(1)
(c) any one from: only a few places have a suitable estuary / a large enough tidal range; very expensive to build (high initial cost); public / local opposition because of the impact on wildlife ignore 'tides are unreliable'(1)
Answer: (a) tides are predictable / happen twice a day, but wind speed varies; (b) e.g. destroys estuary habitats; (c) e.g. few suitable estuaries / very expensive to build
Examiner tip: 'Reliable' needs a comparison: say why tides are predictable AND why the wind is not, otherwise you score only one mark.

7Grade 6–7Higher5 marks

A wind farm has 30 wind turbines. The maximum power output of each turbine is 2.5 MW.

In one year, the wind farm transferred $7.1 \times 10^{14}$ J of energy to the National Grid.

1 year = 365 days.

(a) Calculate the mean power output of the wind farm during the year. [3]

(b) Calculate the mean power output as a percentage of the maximum possible power output of the wind farm. [1]

(a) time = 365 × 24 × 3600 = 31 536 000 s allow 3.15 × 10⁷ s or 3.2 × 10⁷ s(1)
(a) $P = \dfrac{E}{t} = \dfrac{7.1 \times 10^{14}}{31\,536\,000}$ allow substitution of any time value, including an incorrect one (e.g. 3.2 × 10⁷ or 365)(1)
(a) $2.25 \times 10^{7}$ W allow 22.5 MW; allow 2.3 × 10⁷ W / 23 MW; allow 2.2 × 10⁷ W (from rounding); an answer of 2.25 × 10⁷ W with no working scores 3; using t = 365 (days) gives 1.9 × 10¹² W and scores 1 mark (substitution only)(1)
(b) 30 (%) maximum = 30 × 2.5 = 75 MW; allow ecf from (a), e.g. 23 MW → 31%; allow 29–31%(1)
(c) any one from: wind speed is not always high enough (some days there is little or no wind); turbines are shut down when the wind is too strong; turbines are switched off for maintenance / repair; demand is low so turbines are switched off ignore 'energy is wasted' / 'turbines are not efficient'(1)
Answer: (a) 2.25 × 10⁷ W (22.5 MW); (b) 30%; (c) the wind speed varies / is often too low
Examiner tip: Convert the year into seconds before using P = E/t: 365 × 24 × 60 × 60 — leaving time in days or hours gives a power that is wrong by a huge factor.

8Grade 6–76 marks

A country plans to close its coal-fired power stations. It is deciding whether to replace them with:

a nuclear power station, or
a large hydroelectric dam in a mountain valley.

Both would give about the same maximum power output.

Evaluate the use of each energy resource to replace the coal-fired power stations.

Your answer should include a conclusion. [6]

Nuclear: no carbon dioxide (or sulfur dioxide) released when generating electricity, so does not add to global warming / acid rain(1)
Nuclear: very reliable – generates electricity all the time / independent of the weather(1)
Nuclear: large amount of energy from a small mass of fuel / power station needs little land(1)
Nuclear: nuclear fuel is non-renewable / uranium will run out(1)
Nuclear: produces radioactive waste that is dangerous for a very long time and must be stored safely(1)
Nuclear: risk of a major accident releasing radioactive material; public may oppose it(1)
Nuclear: very expensive to build and to decommission; long time to start up / cannot quickly change output(1)
Hydroelectric: renewable – water is replenished by rain(1)
Hydroelectric: no carbon dioxide released when generating electricity(1)
Hydroelectric: can be started up quickly / output changed quickly to meet changes in demand(1)
Hydroelectric: reliable except in times of drought / depends on rainfall(1)
Hydroelectric: building the dam floods a large area of land, destroying habitats (and possibly homes / farmland, forcing people to move)(1)
Hydroelectric: rotting vegetation in flooded valley releases methane / carbon dioxide; expensive to build; only possible where there is a suitable valley(1)
Both: no fuel is burned, so no carbon dioxide or other air pollution from burning, compared with coal; both have high initial building costs(1)
Conclusion: any reasoned choice, e.g. hydroelectric because it is renewable and produces no long-lived waste, or nuclear because it does not flood land and is reliable in all weather(1)

Level	Marks	What it looks like
Level 3	5–6	A detailed and coherent evaluation that considers advantages and disadvantages of both the nuclear power station and the hydroelectric dam, covering reliability and environmental impact, with clear comparisons between them. A justified conclusion is given that follows from the points made.
Level 2	3–4	Some relevant advantages and/or disadvantages are given for both options, with at least one attempt to compare them. A conclusion may be given but is not fully supported, or one option is covered in much more detail than the other.
Level 1	1–2	Simple, relevant statements about one or both resources, e.g. 'nuclear waste is dangerous' or 'dams flood land'. Little or no comparison and no logical structure.
No relevant content	0	Nothing worthy of credit.

Answer: Balanced evaluation of both, e.g. nuclear: no CO₂, very reliable, but non-renewable fuel and long-lived radioactive waste; hydro: renewable, no CO₂, quick start-up, but floods valleys and depends on rainfall; reasoned conclusion.
Examiner tip: Top-level answers compare both options AND finish with a conclusion that follows from the points made – listing facts about only one resource caps you at Level 1–2.

9Grade 6–74 marks

Scientists have shown that burning fossil fuels releases carbon dioxide, which contributes to global warming.

Despite this, some countries are still building new coal-fired power stations.

(a) Suggest three reasons why these countries continue to build coal-fired power stations. [3]

(b) Scientists can identify the problems caused by burning fossil fuels. Explain why scientists alone cannot decide whether a country stops using fossil fuels. [1]

(a) any three from: the country has its own large reserves of coal (so does not rely on imports / energy security); coal power stations are relatively cheap to build / coal is a cheap fuel; coal power stations are reliable / provide electricity at all times and can meet demand; demand for electricity is growing quickly (e.g. rising population / industry); many people's jobs depend on coal mining (so closing it is unpopular); building enough renewable generation is expensive / takes a long time; renewables such as wind and solar are unreliable / depend on the weather; the country may not have suitable sites for renewables (e.g. hydro / tidal / geothermal)(1)
(a) second, different reason(1)
(a) third, different reason reasons may be economic, social or political; two points that both only say 'it is cheap' score 1 mark(1)
(b) the decision also depends on economic / political / social / ethical factors (such as cost, jobs or what voters want), which science cannot answer allow governments / politicians make the decision, taking account of cost and public opinion; ignore 'scientists might be wrong'(1)
Answer: (a) e.g. own coal reserves / cheap; reliable to meet growing demand; jobs depend on coal mining; (b) the decision also involves economic, political, social and ethical factors
Examiner tip: Good answers give reasons from different categories – money, reliability, jobs, politics – rather than three ways of saying 'it is cheap'.

10Grade 6–7Higher6 marks

The graph shows how the total demand for electricity in a country and the power generated by solar cells changed during one day in summer.

(a) Determine the power that must be generated by energy resources other than solar cells at 12:00 (12 hours). [2]

(b) Determine the increase in the power that must be generated by these other resources between 12:00 and 18:00. [2]

Explain why. [2]

(a) readings of 34 (GW) for demand and 10 (GW) for solar at 12 hours allow 33–35 GW for demand and 9–11 GW for solar(1)
(a) 24 GW allow 23–25 GW(1)
(b) power from other resources at 18:00 = 38 − 1 = 37 (GW) allow 36–38 GW(1)
(b) increase = 37 − 24 = 13 GW allow ecf from (a); allow 12–14 GW(1)
(c) gas-fired power stations have a short start-up time / their output can be increased quickly allow can be switched on quickly when demand rises(1)
(c) nuclear power stations have a long start-up time / cannot change their output quickly (so they are used to supply the constant base demand) a comparison is needed for 2 marks; ignore references to carbon dioxide or cost(1)
Answer: (a) 24 GW; (b) 13 GW; (c) gas power stations start up / change output quickly; nuclear power stations have long start-up times so cannot respond to the evening rise in demand
Examiner tip: At 18:00 solar is not zero (about 1 GW), so subtract it from the demand – and remember the question asks for the increase, not the 18:00 value.

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