Pearson Edexcel International GCSE (9–1) · PHYSICS · Section
Nuclear reactions as a source of energy
19 practice questions
Practice questions
1–3 of 3 · 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.