Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
6.38P Explain how the fission of U-235 produces two daughter nuclei and…
Full specification wording
Topic 6 – Radioactivity: 6.38P Explain how the fission of U-235 produces two daughter nuclei and the emission of two or more neutrons, accompanied by a release of energy
In fission, a slow neutron is absorbed by a uranium-235 nucleus, making it unstable.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 34 of 42
Study notes
From the checked teaching notes for this specification point.
The idea
In fission, a slow neutron is absorbed by a uranium-235 nucleus, making it unstable. The nucleus splits into two smaller daughter nuclei and releases two or more neutrons plus energy. The released neutrons can be absorbed by other U-235 nuclei, triggering further fissions in a chain reaction. The energy appears as kinetic energy of the fragments and neutrons, which becomes heat in a reactor. A good answer names the absorbed neutron, the two daughter nuclei, the two or more emitted neutrons and the energy release, and can explain that the extra neutrons sustain a chain reaction.
What earns the marks
- States that a neutron is absorbed by a U-235 nucleus before it splits.
- Identifies that fission produces two smaller daughter nuclei.
- States that two or more neutrons are emitted during fission.
- Explains that energy is released and that emitted neutrons can cause further fissions in a chain reaction.
Common mistakes and how to put them right
Says the nucleus splits into one fragment.
Put it right: State that two daughter nuclei form.
Omits the emitted neutrons.
Put it right: Include that two or more neutrons are released.
Claims energy is absorbed in fission.
Put it right: Explain that energy is released.
Exam tips
- Name the incoming neutron, the two daughter nuclei, the emitted neutrons and the energy release in order.
- Link emitted neutrons to a chain reaction to gain explanation credit.
- Use the term daughter nuclei rather than fragments alone.
Try the lesson
The start of the Topic 6 – Radioactivity: 6.38P Explain how the fission of U-235 produces two daughter nuclei and the emission of two or more neutrons, accompanied by a release of energy lesson, made from checked teaching notes for this specification point.
Have a go first
In nuclear fission, a uranium-235 nucleus absorbs a neutron and then splits. What is produced when a uranium-235 nucleus undergoes fission?
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