Pearson Edexcel International GCSE (9–1) · PHYSICS · Chapter
Fission and Fusion
47 practice questions
Topics covered
Practice questions
1–7 of 7 · Hard
Question 1
5 marks · Hard
Answer and see the solution →A nuclear power plant uses uranium-235 as its fuel. The process of fission for a single uranium-235 nucleus is represented by the equation:
(a)[3 marks]Explain, step by step, how the products of this reaction lead to the release of energy. In your answer, refer to how the energy is distributed between the different products.
(b)[2 marks]Describe what happens to the neutrons that are produced in this reaction in a working nuclear reactor. Include the roles of the moderator and control rods in your answer.
Question 2
4 marks · Hard
Answer and see the solution →Nuclear fusion is the process that powers stars, while nuclear fission is used in reactor power plants on Earth.
Compare and explain, in detail, why it is much more difficult to start and sustain nuclear fusion reactions on Earth than nuclear fission. Your answer should refer to the forces involved and the conditions needed.
Question 3
5 marks · Hard
Answer and see the solution →A sample of uranium-235 is kept in a laboratory. It is observed that a chain reaction does not start when only a small amount is present.
(a)[2 marks]Explain why a chain reaction cannot be set up in a very small mass of uranium-235, using the concept of critical mass.
(b)[3 marks]Calculate and explain what happens to most of the neutrons that are produced during fission in a sub-critical sample. Suggest two different ways these neutrons are prevented from causing further fission.
Question 4
4 marks · Hard
Answer and see the solution →Nuclear fusion is being researched as a possible source of unlimited clean energy on Earth, but it has not yet been achieved on a large scale.
Explain, using scientific ideas, why achieving nuclear fusion on Earth is much more difficult than in the core of stars. Include at least two physical reasons in your answer.
Question 5
4 marks · Hard
Answer and see the solution →A student claims that nuclear fission and nuclear fusion are both potential sources of energy.
Explain the difference between fission and fusion in terms of the nuclei involved and the products formed. Then, describe why fusion produces energy only when light nuclei are used.
Question 6
5 marks · Hard
Answer and see the solution →Scientists want to develop fusion reactors as a future energy source, while fission reactors are already in use. The diagram represents a simplified nuclear reactor core.
A simple nuclear reactor core layout (a)[2 marks]Describe the function of: (i) the moderator (ii) the control rods in a nuclear fission reactor.
(b)[2 marks]Explain why a continuous chain reaction occurs in a fission reactor but not in a fusion reactor, even though both reactions can produce neutrons.
(c)[1 mark]Fusion occurs in stars. State two conditions required for fusion to occur and explain why these are necessary.
Question 7
7 marks · Hard
Answer and see the solution →Nuclear power stations rely on an understanding of both fission and fusion.
(a)[3 marks]Outline how a chain reaction is started and controlled in a fission reactor, and explain why this is necessary for safe operation.
(b)[3 marks]Explain why fusion is the main source of energy in stars but not in current nuclear power stations.
(c)[1 mark]Give one reason why some scientists prefer the idea of fusion over fission as a future energy source on Earth.