A2 Daily A Level Physics question
A sealed rigid steel can of air is warmed in sunlight from 20 °C to 60 °C. Assuming the gas behaves ideally and the can’s volume does not change, what happens to the pressure inside? Choose the closest option.
Answer
The correct answer is B.
Correct: B — Increases by about 14%. At fixed volume with a fixed amount of gas, pressure is proportional to absolute temperature: 333 K / 293 K ≈ 1.14, so about a 14% increase. A misuses the Celsius change (40 °C) as a percentage, ignoring that proportionality uses kelvin. B is correct because using kelvin gives 333/293 ≈ 1.14, i.e. ~14% increase. C wrongly assumes a doubling based on Celsius temperatures rather than absolute temperature. D ignores that increasing temperature increases the average molecular speed, so pressure must rise at constant volume.