Fusion & Fission
Fusion and fission look opposite: one joins light nuclei and the other splits a heavy nucleus. Learn the exact process words before explaining their energy changes.
Fusion joins; fission splits
Definition
2 marksWhat is meant by nuclear fusion?
Model answer: Nuclear fusion is the joining of two light nuclei to form one heavier nucleus.
Definition
2 marksWhat is meant by nuclear fission?
Model answer: Nuclear fission is the splitting of one heavy nucleus into two or more lighter nuclei.
(9702/41/O/N/23 Q9(a); 9702/42/O/N/24 Q10(b)(i))
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| Process | Starting nuclei | Products | Direction on the curve | Typical condition |
|---|---|---|---|---|
| Fusion | Two light nuclei | One heavier nucleus | Moves right towards the maximum | Very high temperature lets the nuclei approach closely |
| Fission | One heavy nucleus | Two or more intermediate nuclei | Moves left towards the maximum | Often initiated when a heavy nucleus absorbs a neutron |
Your turn9702/42/O/N/24 Q10(b)(i)
State three differences between nuclear fusion and nuclear fission. [3]
Show worked answer
- Fusion joins two light nuclei; fission splits one heavy nucleus.
- Fusion forms one heavier nucleus; fission forms two or more lighter nuclei.
- Fusion usually needs very high temperature; fission is often initiated by neutron absorption.