AQA GCSE Physics (8463), Higher tier · Particle model of matter › Particle model and pressure
Practise Increasing the pressure of a gas. 12 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Complete the sentence. Work is the transfer of energy by a ................ .
force
State whether compressing a gas quickly increases, decreases, or has no effect on its temperature.
It increases.
State the two ways that the internal energy of a gas can be increased.
By heating it, or by doing work on it (e.g. compressing it).
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) Complete the sentence. Work is the transfer of energy by a ................ .[1]
(b) The air in a sealed syringe is compressed quickly. Work is done on the air. What happens to the internal energy of the air? Tick (✓) one box.[1]
It decreases.
It stays the same.
It increases.
(c) What happens to the temperature of the air?[1]
(d) Name one device in which doing work on a gas increases the temperature of the gas.[1]
Show the answer and mark scheme
(a)Answer: force
force
(b)Answer: It increases.
(c)Answer: It increases.
it increases
(d)Answer: A bicycle pump
bicycle pump / tyre pump / diesel engine / air compressor
Question 2Medium7 marks
A cyclist uses a bicycle pump to inflate a tyre. After many quick strokes, the barrel of the pump feels warm.
(a) Explain why the temperature of the air in the pump increases when the piston is pushed in quickly.[3]
(b) The average force on the piston during one stroke is 90 N. The piston moves 0.20 m during each stroke. Calculate the work done on the air in one stroke.[2]
(c) Explain why the air becomes hotter when the strokes are quick than when they are slow.[2]
Show the answer and mark scheme
(a)Answer: The force on the piston moves through a distance, so work is done on the air. This increases the internal energy of the air: its molecules gain kinetic energy, so its temperature rises.
the cyclist exerts a force on the piston, which moves through a distance, so work is done on the air
the work done transfers energy to the air / increases the internal energy of the air
the (average) kinetic energy of the air molecules increases, so the temperature increases
air molecules that hit the moving piston bounce off it faster
(b)Answer: 18 J
W = 90 × 0.20
18 (J)
(c)Answer: With quick strokes there is little time for energy to be transferred away by heating, so more of the work done stays in the air and its temperature rises more.
with quick strokes there is less time for energy to be transferred from the air to the pump / surroundings (by heating)
so more of the energy transferred by doing work stays in the air as internal energy, and the temperature rises more
Question 3Hard8 marks
A student sealed the nozzle of a syringe containing air. The student pushed the plunger in very quickly. The average force on the plunger was 60 N and the plunger moved 5.0 cm.
(a) Calculate the work done on the air.[2]
(b) mass of air in the syringe = 6.0 × 10−5 kg For this situation, the specific heat capacity of air is 720 J/kg °C. Calculate the maximum possible increase in the temperature of the air. Give your answer to 2 significant figures. Use the Physics Equations Sheet.[3]
(c) Suggest two reasons why the actual increase in the temperature of the air would be less than this.[2]
(d) The student then pushed the plunger in very slowly to the same position. The temperature of the air hardly changed. Explain why.[1]
Show the answer and mark scheme
(a)Answer: 3.0 J
W = 60 × 0.050
3.0 (J)
(b)Answer: 69 °C
3.0 = 6.0 × 10−5 × 720 × Δθ
Δθ = 3.0 ÷ 0.0432
69 (°C)
(c)Answer: Some energy is transferred from the air to the syringe and the surroundings, and some work is done against friction instead of on the air.
some energy is transferred (by heating) from the air to the syringe / plunger / surroundings
some of the work done is against friction between the plunger and the syringe (heating them rather than the air)
some air leaks out past the plunger / through the seal
(d)Answer: When it is compressed slowly, energy transferred to the air is transferred to the surroundings as fast as it is gained.
the energy transferred to the air by doing work is transferred to the surroundings (by heating) at about the same rate / there is time for energy to be transferred away