Describe the products released during nuclear fission and explain why these products are important for sustaining a chain reaction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Fission of a heavy nucleus produces two smaller, more stable nuclei and releases two or three neutrons (plus gamma‑ray energy). The free neutrons are absorbed by other large, unstable nuclei, causing further fission events. This self‑sustaining sequence of reactions is the chain reaction.
Examiner tips
- Use the exact phrase "two or three neutrons" and mention gamma‑ray energy
- Explain that the neutrons are absorbed by other nuclei to continue the reaction
- Show the link between neutron release and self‑sustaining chain reaction
Common mistakes
- Confusing the products with the original nucleus; forgetting the neutrons
- Not mentioning that the neutrons are absorbed by other nuclei
- Omitting the gamma‑ray energy or the idea of self‑sustaining chain reaction
Mark scheme (4 marks)
- Fission produces two smaller (more stable) nuclei
- Fission also releases two or three neutrons (and gamma rays / energy)
- The released neutrons can be absorbed by other large unstable nuclei
- This induces further fission reactions, so the chain reaction is self-sustaining
Key terms in this question
nuclear fission · chain reaction
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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