# Describe the process of nuclear fission and explain why it releases a large amount of energy.

> Eduqas A-Level Physics — 3.6 Nuclear energy · Describe and Explain · 5 marks

> Nuclear fission is used in power stations as an alternative to burning fossil fuels. In a fission reaction, a large unstable nucleus splits into smaller nuclei after absorbing a neutron.

## Mark scheme (5 marks)

1. A large unstable nucleus (e.g. uranium-235) absorbs a neutron
2. The nucleus splits into two smaller (daughter/fragment) nuclei
3. Two or three neutrons are released / emitted during the split
4. These released neutrons can trigger further fission reactions, causing a chain reaction
5. The energy released is large because the products have less mass than the original nucleus and neutron / mass is converted into energy

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-process-of-nuclear-fission-b2590c64) · Published by Druglandscape Ltd.