AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Nuclear fission and fusion
Nuclear fission and fusion · Atomic structure · Lesson 10 of 10 · 15 marks · 16 minutes
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Instructions
• Answer all the questions.
• Write your answers in the spaces provided.
• The marks for each question are shown in brackets - use this as a guide to how much to write.
• The answers are on separate pages at the back. Attempt every question before you look at them.
• Answer all questions. Use the mark allocation as a guide to how much to write.
Question 1 STATE (2 marks)
What is meant by nuclear fission?
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(Total for Question 1 = 2 marks)
Question 2 COMPLETE THE DIAGRAM (3 marks)
The diagram shows part of a fission chain reaction. (a) Name the particle labelled X. (b) Explain how the diagram shows that a chain reaction can happen.
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(Total for Question 2 = 3 marks)
Question 3 EXPLAIN (3 marks)
Explain how the chain reaction is controlled in a nuclear reactor.
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(Total for Question 3 = 3 marks)
Question 4 DESCRIBE (3 marks)
Describe what happens in nuclear fusion, and state one condition needed for it to happen.
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(Total for Question 4 = 3 marks)
Question 5 COMPARE (4 marks)
Compare nuclear fission and nuclear fusion.
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(Total for Question 5 = 4 marks)
TOTAL FOR PAPER = 15 MARKS
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Answers and mark scheme
Check your answer only once you have written one.
Question 1 (2 marks)
The splitting of a large and unstable nucleus (such as uranium or plutonium) into two smaller nuclei.
• Splitting of a large unstable nucleus 1 mark
• Into two smaller nuclei 1 mark
Question 2 (3 marks)
(a) A neutron. (b) Each fission releases two or three neutrons, which cause further nuclei to split, so the reaction continues.
• X is a neutron 1 mark
• Each fission releases more than one neutron 1 mark
• These cause more nuclei to split 1 mark
Question 3 (3 marks)
Control rods absorb some of the neutrons produced. This means on average only one neutron from each fission causes another fission, so the reaction continues steadily without getting out of control.
• Control rods absorb neutrons 1 mark
• Only one neutron from each fission goes on to cause fission 1 mark
• So the rate of energy release is steady 1 mark
Question 4 (3 marks)
Two light nuclei join to form a heavier nucleus, and some of the mass is converted to energy. Very high temperature (and pressure) is needed to overcome the repulsion between the nuclei.
• Two light nuclei join 1 mark
• Energy released 1 mark
• Very high temperature or pressure needed 1 mark
Question 5 (4 marks)
Fission is the splitting of a large unstable nucleus into two smaller nuclei; fusion is the joining of two light nuclei to make a heavier one. Both release energy. Fission releases neutrons that cause a chain reaction; fusion needs very high temperature and pressure.
• Fission: splitting 1 mark
• Fusion: joining 1 mark
• Both release energy 1 mark
• A difference in conditions or products 1 mark