Practise 27 exam-style questions on The life cycle of a star for AQA GCSE Physics. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
27 questions
1–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
A star much more massive than the Sun ends its life in a supernova.
Name the two types of object that can be left behind after a supernova.
Model answer
A neutron star or a black hole.
Explanation
The core left after a supernova becomes a neutron star; if the remaining mass is large enough, it collapses further to form a black hole. White dwarfs and black dwarfs come from stars with about the same mass as the Sun.
Mark scheme
1 mark
neutron star
1 mark
black hole
do not accept white dwarf or black dwarf
Question 2
2 marks
In a red giant, helium-4 nuclei (⁴₂He) fuse to form carbon-12 nuclei (¹²₆C).
Determine how many helium-4 nuclei fuse to form one carbon-12 nucleus. Show how you worked out your answer.
Model answer
Each helium-4 nucleus has mass number 4 and atomic number 2. Mass number: 12 ÷ 4 = 3 Atomic number: 6 ÷ 2 = 3 So 3 helium-4 nuclei fuse to form one carbon-12 nucleus: 3 ⁴₂He → ¹²₆C
Explanation
In fusion, both the mass numbers and the atomic numbers must add up on each side of the equation. Three helium nuclei give a mass number of 12 and an atomic number of 6, which is carbon.
allow either calculation; an answer of 3 with working scores 2 marks
1 mark
3 (helium nuclei)
Question 3
3 marks
Astronomers predict that white dwarfs eventually become black dwarfs. However, no black dwarfs have ever been observed.
Suggest why no black dwarfs have been observed.
Model answer
White dwarfs cool down extremely slowly, and astronomers calculate that a white dwarf would take longer than the present age of the universe to cool into a black dwarf, so none has had time to form yet. Even if one existed, it would give out almost no light, so it would be very difficult to detect.
Explanation
The black dwarf stage comes from the theory of how stars cool, not from observations. Scientific models can predict things that have not yet been seen, as long as they are consistent with the evidence.
Mark scheme
1 mark
white dwarfs cool down very slowly
1 mark
it takes longer than the age of the universe for a white dwarf to cool to a black dwarf
allow the universe is not old enough
1 mark
black dwarfs would give out (almost) no light, so would be very hard to detect
Question 4
4 marks
Explain how fusion processes in stars lead to the formation of new elements. Include the role of supernovae.
Model answer
In a main sequence star, hydrogen nuclei fuse to form helium. When the hydrogen in the core runs out, helium nuclei fuse to form heavier elements such as carbon and oxygen. In stars much more massive than the Sun, fusion continues, building up heavier and heavier elements as far as iron. Elements heavier than iron are produced in a supernova, when a massive star explodes.
Explanation
Each stage of fusion joins lighter nuclei to make heavier ones. Fusion in stars produces all the naturally occurring elements up to iron, and supernovae produce the rest and spread them through the universe.
Mark scheme
1 mark
in main sequence stars, hydrogen nuclei fuse to form helium
1 mark
later (e.g. in red giants), helium fuses to form heavier elements such as carbon and oxygen
allow heavier elements are formed by fusing lighter nuclei
1 mark
in the most massive stars, fusion continues to form elements up to iron
1 mark
elements heavier than iron are produced in a supernova
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