# Describe the differences between nuclear fission and nuclear fusion. In your answer, include what happens to the nuclei involved and the conditions needed for each process.

> WJEC A-Level Physics (Wales) — 3.6 Nuclear energy · Describe · 5 marks

## Mark scheme (5 marks)

1. Nuclear fission involves a large/heavy nucleus splitting into two smaller nuclei (and neutrons)
2. Nuclear fusion involves two small/light nuclei joining together to form a larger nucleus
3. Fission requires a neutron to be absorbed by (or fired at) the nucleus / fission is triggered by a neutron
4. Fusion requires extremely high temperatures (and pressure) to overcome the electrostatic repulsion between nuclei
5. Both processes release large amounts of energy / fusion releases more energy per kilogram of fuel than fission

## Key terms

- [nuclear fission](https://www.gradenine.co.uk/glossary/nuclear-fission)
- [nuclear fusion](https://www.gradenine.co.uk/glossary/nuclear-fusion)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-differences-between-nuclear-fission-c8d18eb4) · Published by Druglandscape Ltd.