AQA GCSE Physics
AQA GCSE Physics 4.4.4 Nuclear Fission and Fusion Exam Questions
Free AQA GCSE Physics exam questions for 4.4.4 Nuclear Fission and Fusion, with a mark scheme for every pack. Covers nuclear fission of uranium and plutonium, chain reactions, controlled reactors, nuclear weapons, and nuclear fusion of light nuclei.
4.4.4 Nuclear Fission and Fusion exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.4.4 Nuclear Fission and Fusion
Nuclear fission and fusion is a physics only section of AQA GCSE Physics, examined on Paper 1. Fission is the splitting of a large unstable nucleus such as uranium or plutonium, and it powers nuclear reactors. Fusion is the joining of two light nuclei to form a heavier one, and it releases energy in stars. You need to describe both processes, draw or interpret a diagram of a chain reaction and explain how a chain reaction is controlled. Examiners often ask for comparisons and for the role of neutrons.
What you need to know
- Nuclear fission Fission is the splitting of a large and unstable nucleus, such as uranium or plutonium. Spontaneous fission is rare; usually the nucleus must first absorb a neutron.
- Products of fission The nucleus splits into two smaller nuclei, roughly equal in size, and emits two or three neutrons plus gamma rays. Energy is released, and all the fission products have kinetic energy.
- Chain reaction The neutrons released may go on to cause more fission. Draw or interpret a diagram showing how this chain reaction occurs.
- Controlled and uncontrolled In a nuclear reactor the chain reaction is controlled so the energy released is steady (control rods absorb neutrons). The explosion caused by a nuclear weapon is an uncontrolled chain reaction.
- Nuclear fusion Fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation.
- Comparing the two Fission splits heavy nuclei and is used in power stations. Fusion joins light nuclei, powers stars, and is not yet a practical source of electricity on Earth.
Common mistakes in 4.4.4 Nuclear Fission and Fusion
- Mixing up fission and fusion. Fission splits a large nucleus; fusion joins small nuclei.
- Saying fission happens when a uranium nucleus is hit by any particle. It absorbs a neutron, becomes unstable and splits.
- Forgetting that fission releases neutrons as well as two smaller nuclei. The neutrons are what allow a chain reaction.
- Saying the reactor is controlled by slowing down the reaction with water only. The spec point is that the chain reaction is controlled; control rods absorb neutrons to limit further fission.
Try three 4.4.4 Nuclear Fission and Fusion exam-style questions
1. Describe the process of nuclear fission of uranium-235. (4 marks)
Show the mark scheme answer
A neutron is absorbed by a uranium-235 nucleus; the nucleus becomes unstable and splits into two smaller nuclei (roughly equal in size); two or three neutrons are released along with gamma rays; energy is released (the products have kinetic energy).
2. Explain how a chain reaction is controlled in a nuclear reactor. (2 marks)
Show the mark scheme answer
Control rods absorb some of the neutrons released; so on average only one neutron from each fission causes another fission, keeping the energy release steady.
3. State two differences between nuclear fission and nuclear fusion. (2 marks)
Show the mark scheme answer
Fission splits a large nucleus while fusion joins two small (light) nuclei; fission is used in nuclear power stations while fusion happens in stars (or fission needs a neutron to be absorbed while fusion needs very high temperature and pressure).
4.4.4 Nuclear Fission and Fusion FAQs
What does AQA GCSE Physics 4.4.4 Nuclear fission and fusion cover?
It covers nuclear fission of large nuclei, chain reactions in reactors and weapons, and nuclear fusion of light nuclei.
Is fission and fusion on Combined Science?
No, 4.4.4 is physics only, so it is only assessed in the separate AQA GCSE Physics course on Paper 1.
Which diagrams should I practise?
Practise drawing a chain reaction: a neutron hits a uranium nucleus, it splits into two daughter nuclei and releases two or three neutrons, which then hit further nuclei.
