AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Nuclear fusion is the joining of two light nuclei to form a heavier…
Full specification wording
Nuclear fusion: Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation.
Nuclear fusion is the joining of two light nuclei to form a heavier one.
Checked against the AQA 8463 specification (opens in a new tab) on .
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Nuclear fusion is the joining of two light nuclei to form a heavier one. In the Sun and in experimental reactors, hydrogen isotopes fuse to form helium. Getting them to fuse is hard because both nuclei are positively charged and repel strongly, so extremely high temperatures and pressures are needed to bring them close enough; lasers or magnetic confinement are used to reach those conditions. When they do fuse, the heavier nucleus has slightly less mass than the two that formed it, and some of the mass is converted into the energy of radiation. This is the energy source of every main sequence star, where the outward effect of fusion balances the inward gravitational collapse.
What earns the marks
- Two light or lighter nuclei, such as hydrogen nuclei, fusing together.
- Forming a heavier nucleus or a heavier element, for example helium.
- Some of the mass of the nuclei being converted into the energy of radiation.
- The very high temperature and pressure needed to overcome the repulsion between positively charged nuclei.
Common mistakes and how to put them right
Describing fusion as the splitting of a nucleus.
Writing that the nuclei bond or collide and stick, which examiners ignore without the mass conversion point.
Saying fusion takes place at ordinary temperatures.
Confusing nuclear fusion with the melting or fusing of solids.
Claiming mass is destroyed rather than converted into the energy of radiation.
Exam tips
- Use the phrase 'some of the mass is converted into energy', because that exact idea carries its own mark.
- Name helium as the product if hydrogen is named in the question; it is explicitly allowed.
- Avoid the words 'bonding' and 'colliding' as your main verb; 'fuse' or 'join' is what is credited.
Try the lesson
The start of the Nuclear fusion: Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation. lesson, made from checked teaching notes for this specification point.
Have a go first
Which process describes nuclear fusion?
Listen
Nuclear fusion is the joining of two light nuclei to form a heavier one. In the Sun and in experimental reactors, hydrogen isotopes fuse to form helium. Getting them to fuse is hard because both nuclei are positively charged and repel strongly, so extremely high temperatures and pressures are needed to bring them close enough; lasers or magnetic confinement are used to reach those conditions. When they do fuse, the heavier nucleus has slightly less mass than the two that formed it, and some of the mass is converted into the energy of radiation. This is the energy source of every main sequence star, where the outward effect of fusion balances the inward gravitational collapse. A strong answer earns marks for these points. two light or lighter nuclei, such as hydrogen nuclei, fusing together. forming a heavier nucleus or a heavier element, for example helium. some of the mass of the nuclei being converted into the energy of radiation. the very high temperature and pressure needed to overcome the repulsion between positively charged nuclei. Exam tip: Use the phrase 'some of the mass is converted into energy', because that exact idea carries its own mark.
See it
Put it in order
Put these steps in the order they happen.
- 1. Overcome repulsion between positively charged nuclei
- 2. Very high temperature and pressure needed
- 3. Two light nuclei, e.g. hydrogen
- 4. Some of the mass is converted into the energy of radiation
- 5. Heavier nucleus has slightly less mass
- 6. Nuclei fuse to form a heavier nucleus, e.g. helium
Key words
Say what each word means before you turn the card.
nuclear fusion
Try answering aloud or in your head before turning the card.
mass converted to energy
Try answering aloud or in your head before turning the card.
high temperature and pressure
Try answering aloud or in your head before turning the card.
energy source of stars
Try answering aloud or in your head before turning the card.
See every definition
- nuclear fusion
- The joining of two light nuclei to form a heavier nucleus.
- mass converted to energy
- In fusion, some of the mass may be converted into the energy of radiation.
- high temperature and pressure
- Extremely high temperatures and pressures are needed to bring positively charged nuclei close enough to fuse.
- energy source of stars
- Fusion is the energy source of every main sequence star, where its outward effect balances the inward gravitational collapse.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Nuclear fusion: Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge