A bicycle tyre is pumped up and left in a warm garage. Explain why the pressure inside the tyre increases as the temperature of the air inside rises, using ideas about particles.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A bicycle tyre contains a fixed mass of air. When the garage warms up on a sunny day, the pressure inside the tyre is noticed to be higher than it was in the morning.
Model answer (5 marks)
The air particles move faster and have greater kinetic energy when the temperature rises. They collide with the tyre walls more frequently and each collision transfers more force, because the particles hit the walls harder. The volume of the tyre remains (approximately) constant, so the same area of wall is struck more often and with greater force. Consequently, the pressure inside the tyre increases.
Examiner tips
- Use the word "kinetic energy" to link temperature and particle speed. Mention both increased collision frequency and increased force per collision. State that the tyre volume is essentially fixed. Show the logical chain: temperature ↑ → speed ↑ → collisions ↑ and force ↑ → pressure ↑.
Common mistakes
- Failing to mention that the tyre volume is constant. Using vague terms like "more air" instead of kinetic energy. Omitting the link between temperature and particle speed.
Mark scheme (5 marks)
- The air particles move faster / have greater kinetic energy when the temperature increases
- The particles collide with the walls of the tyre more frequently
- Each collision transfers more force / particles hit the walls harder
- The volume of the tyre stays (approximately) constant / the tyre does not expand significantly
- More frequent and more forceful collisions on the same area of wall means the pressure increases
Key terms in this question
pressure · temperature · particle
Related
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