IGCSE · 6 · structured
Space physics · Question 9
Space physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 8
- Topics
- 1
- Answer
- Complete
A star forms from a cloud of dust and gas that is pulled together by gravitational attraction. The Sun is a stable star roughly halfway through its life.
- (a)
Explain Explain why the Sun is stable at present, in terms of the forces acting within it.
2 marks - (b)
Describe Describe the process by which energy is released in the core of the Sun.
3 marks - (c)
Describe Describe what will happen to the Sun once the hydrogen in its core has been used up.
3 marks
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(a)
Explain Explain why the Sun is stable at present, in terms of the forces acting within it.
State the outcome first, then link cause to effect with the relevant physical principle. Each link in the reasoning should be explicit enough to earn its own marking point.
- 1
the inward gravitational attraction of the Sun's own mass
- 2
is balanced by the outward pressure produced by the energy released in the core, so the Sun neither collapses nor expands
(b)
Describe Describe the process by which energy is released in the core of the Sun.
Answer the command word directly and use precise physical vocabulary. Include only the distinct features or facts that earn marks, without burying them in unrelated background information.
- 1
hydrogen nuclei fuse together at the very high temperature and pressure of the core
- 2
The fusion products combine to form helium nuclei in the Sun's core.
- 3
the mass of the products is slightly less than that of the reactants, and the difference is released as energy
(c)
Describe Describe what will happen to the Sun once the hydrogen in its core has been used up.
Answer the command word directly and use precise physical vocabulary. Include only the distinct features or facts that earn marks, without burying them in unrelated background information.
- 1
the core contracts and the outer layers expand — the Sun becomes a red giant
- 2
helium and heavier nuclei fuse in the core, up to the mass of iron
- 3
the outer layers are then thrown off as a planetary nebula, leaving the hot dense core as a white dwarf
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