Nuclear Fission and Fusion

This lesson covers nuclear fission and nuclear fusion as required by the AQA GCSE Physics specification (4.4.3). You need to understand how energy is released from the nucleus, the differences between fission and fusion, and how these processes are used in nuclear power stations and stars.

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Energy from the Nucleus

The nucleus of an atom contains a huge amount of energy. This energy can be released in two ways:

1. Nuclear fission — splitting a large nucleus into two smaller nuclei.
2. Nuclear fusion — joining two small nuclei together to form a larger nucleus.

Both processes release enormous amounts of energy — far more than any chemical reaction. This is because the nuclear forces holding the nucleus together are much stronger than the chemical bonds holding molecules together.

Exam Tip: Both fission and fusion release energy, but they work in opposite ways. Fission splits large nuclei; fusion joins small nuclei. A common exam question asks you to compare the two processes — make sure you know the key differences.

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Nuclear Fission