Fossil fuels and nuclear power Cambridge IGCSE Environmental Management revision
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In plain words
Most of the world's electricity still comes from heating water until it turns to steam. The only question is what makes the heat. For two centuries the answer has been the buried remains of ancient swamps and seas.
10 things to know
- Coal formed from plants that grew in swamps millions of years ago. When they died they were buried in mud with very little oxygen, so they did not fully decay. More layers piled on top, and heat and pressure slowly turned the remains into coal.
- Petroleum (oil) and natural gas (methane) formed from tiny sea organisms. They died, sank to the sea bed and were buried under sediment with very little oxygen. Heat and pressure over millions of years turned them into oil and gas.
- Oil and gas moved up through permeable rock until they were trapped under a layer of impermeable rock.
- Fossil fuels are non-renewable, or finite: they are used far faster than they form. Nuclear power is also non-renewable, because its fuel is uranium, which comes from an ore.
- In a fossil fuel power station the fuel is burned to heat water and make steam. The steam turns a turbine. The turbine turns a generator, which produces electricity.
- A nuclear power station works in the same way, except for the source of heat. Uranium atoms are split, which releases heat. Nothing is burned.
- Fossil fuels: benefits. They give a lot of energy, the supply is reliable, the output can be raised and lowered to match demand, and the power stations already exist.
- Fossil fuels: limitations. Burning them releases carbon dioxide, a greenhouse gas, and gases that cause acid rain. They will run out. Mining and drilling damage the land and the sea.
- Nuclear power: benefits. No carbon dioxide is released while it generates, a small mass of fuel gives a very large amount of energy, and the supply is reliable.
- Nuclear power: limitations. The waste is radioactive and stays dangerous for thousands of years. Accidents are rare but very serious. Power stations are costly to build and to take apart safely.
Worked example
Describe how the energy in coal is used to generate electricity.
- The coal is burned, and the heat released boils water to make steam.
- The steam, at high pressure, turns a turbine.
- The turbine turns a generator, and the generator produces electricity.
Tips and tricks
- The chain is always heat, steam, turbine, generator. Learn it once and it works for coal, oil, gas, nuclear, biofuels and geothermal power.
- Nuclear power is non-renewable, but it is not a fossil fuel, and it releases no carbon dioxide when generating.
It lands in your notebook with its questions as flashcards.
Fossil fuels and nuclear power: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What did coal form from?
Dead plants were buried with little oxygen and compressed.
Why did the dead organisms not decay completely?
Without oxygen, decay is very slow.
In a power station, what does the steam turn?
The turbine then turns the generator.
What is the fuel in a nuclear power station?
Uranium atoms are split to release heat.
Which is a benefit of nuclear power?
Nothing is burned, so no carbon dioxide is made.
Why are oil and gas found beneath impermeable rock?Stretch
The impermeable layer acts as a lid.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
Fossil fuels and nuclear power
Cambridge IGCSE Environmental Management 0680 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Describe how petroleum was formed.[4]
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Tiny sea organisms died and sank to the sea bed. They were buried by layers of sediment, with little oxygen, so they did not decay fully. Heat and pressure acted on them over millions of years and turned them into petroleum.
Explain why fossil fuels are described as non-renewable.[2]
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They take millions of years to form. They are being used much faster than they are replaced, so they will run out.
State two limitations of nuclear power.[2]
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Any two: radioactive waste stays dangerous for a very long time; an accident can release radiation; power stations are expensive to build and to take apart; uranium is finite.
Answers: Fossil fuels and nuclear power
- 1. Tiny sea organisms died and sank to the sea bed. They were buried by layers of sediment, with little oxygen, so they did not decay fully. Heat and pressure acted on them over millions of years and turned them into petroleum.
- 2. They take millions of years to form. They are being used much faster than they are replaced, so they will run out.
- 3. Any two: radioactive waste stays dangerous for a very long time; an accident can release radiation; power stations are expensive to build and to take apart; uranium is finite.