O-LevelPhysicsNuclear Physics5054/21 · Oct/Nov 2020 · Q77 Marks
Nuclear fusion is a reaction that occurs in the Sun and other stars.
- (a)Explain what is meant by nuclear fusion.[2]
- (b)Describe the nuclear fusion reaction that takes place in the Sun.[1]
- (c)(i)A star forms when the temperature of a large cloud of gas in space increases as the cloud collapses inwards. State the energy transfers that occur as the cloud collapses.[2]
- (c)(ii)The temperature increase starts a nuclear fusion reaction. Explain why the temperature of the star eventually reaches a steady value.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.
- [B1] joining together of (smaller) nuclei / hydrogen nuclei
- [B1] releasing (large amounts of) energy
- [B1] hydrogen reacts to produce helium
- [C1] gravitational potential energy to internal energy/kinetic energy
- [A1] gravitational potential energy to kinetic energy to internal energy / light
- [B1] energy emitted by (infrared / electromagnetic) radiation
- [B1] energy loss is equal to / balances energy from fusion reaction
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