GCSE Physics revision

Nuclear fusion

Nuclear fission and fusion (physics only)

AQA 4.4.4.2

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AQA student objectives

Learning pathway

ALL 🎯

Nuclear fusion is the joining of two light nuclei to form a heavier nucleus.

MOST 🎯🎯

Apply the specified scientific knowledge of nuclear fusion to a relevant example.

SOME 🎯🎯🎯

Analyse an unfamiliar example of nuclear fusion using the specified scientific ideas.

Revision summary

Read on screen, then print for Cornell-style active revision.

Nuclear fusion occurs when two lighter nuclei join together to form a single, larger nucleus — for example, hydrogen-1 and hydrogen-2 fusing to form helium-3.
Fusion is the process that fuels stars and is responsible for the creation of all elements heavier than hydrogen in the universe.
During fusion, some of the original mass is converted into energy rather than being transferred to the new nucleus, meaning the product nucleus is very slightly lighter than the combined mass of the original nuclei.

1. What is Nuclear Fusion?AQA

Nuclear fusion occurs when two lighter nuclei join together to form a single, larger nucleus — for example, hydrogen-1 and hydrogen-2 fusing to form helium-3.
Fusion is the process that fuels stars and is responsible for the creation of all elements heavier than hydrogen in the universe.
During fusion, some of the original mass is converted into energy rather than being transferred to the new nucleus, meaning the product nucleus is very slightly lighter than the combined mass of the original nuclei.

The mass lost during fusion is converted into a tremendous amount of energy, which is why fusion releases far more energy than other nuclear reactions.
Einstein's famous equation E = mc2 describes this conversion, where the lost mass is multiplied by the speed of light squared to calculate the energy released.
Since the speed of light squared is approximately 9 × 1016 , even a tiny loss of mass results in an enormous release of energy.

2. Energy Released in FusionAQA

The mass lost during fusion is converted into a tremendous amount of energy, which is why fusion releases far more energy than other nuclear reactions.
Einstein's famous equation E = mc2 describes this conversion, where the lost mass is multiplied by the speed of light squared to calculate the energy released.
Since the speed of light squared is approximately 9 × 1016 , even a tiny loss of mass results in an enormous release of energy.

Unlike nuclear fission, fusion does not produce radioactive waste, making it a much cleaner energy source.
Hydrogen, the fuel needed for fusion, can be produced relatively easily, meaning fuel supply is not a major concern.
If harnessed on Earth, fusion could provide a virtually limitless and environmentally friendly source of energy.

3. Advantages of Nuclear FusionAQA

Unlike nuclear fission, fusion does not produce radioactive waste, making it a much cleaner energy source.
Hydrogen, the fuel needed for fusion, can be produced relatively easily, meaning fuel supply is not a major concern.
If harnessed on Earth, fusion could provide a virtually limitless and environmentally friendly source of energy.

Fusion requires extremely high temperatures and pressures — around 10 million degrees — which currently makes it impossible to sustain in a controlled environment on Earth.
These extreme conditions are naturally present inside stars, which is why fusion occurs there but not yet here on Earth.
There is significant ongoing experimental research aimed at finding ways to achieve and sustain nuclear fusion as a practical energy source in the future.

4. Challenges of Achieving Fusion on EarthAQA

Fusion requires extremely high temperatures and pressures — around 10 million degrees — which currently makes it impossible to sustain in a controlled environment on Earth.
These extreme conditions are naturally present inside stars, which is why fusion occurs there but not yet here on Earth.
There is significant ongoing experimental research aimed at finding ways to achieve and sustain nuclear fusion as a practical energy source in the future.

Nuclear fusion involves fusing light nuclei together to form heavier nuclei, whereas nuclear fission involves splitting large, unstable nuclei into two smaller nuclei.
Both processes release large amounts of energy, but fusion releases significantly more energy than fission.
Nuclear fission is the process currently used in nuclear power stations on Earth to generate electricity, while fusion remains experimental.

5. Nuclear Fusion vs Nuclear FissionAQA

Nuclear fusion involves fusing light nuclei together to form heavier nuclei, whereas nuclear fission involves splitting large, unstable nuclei into two smaller nuclei.
Both processes release large amounts of energy, but fusion releases significantly more energy than fission.
Nuclear fission is the process currently used in nuclear power stations on Earth to generate electricity, while fusion remains experimental.