# Explain why the energy released per kilogram of fuel in a nuclear fission reaction is many millions of times greater than the energy released per kilogram of fuel in a typical chemical combustion reaction.

> IB DP Physics Standard Level (2023 syllabus) — E.4 Fission · Explain · 4 marks

## Mark scheme (4 marks)

1. Chemical reactions involve rearrangement of electrons / breaking and forming of chemical bonds between atoms
2. Nuclear fission involves changes within the nucleus itself, specifically the splitting of a heavy nucleus
3. The nuclear force (strong force) binding nucleons together is far stronger than the electromagnetic force binding electrons to atoms, so much more energy is stored per particle in nuclear bonds
4. In fission, a small amount of mass is converted directly into energy via E = mc²; because c² is very large, even a tiny mass defect yields enormous energy

## Key terms

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

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-energy-released-per-96c17377) · Published by Druglandscape Ltd.