Boyle's law
2 marks · NormalA bicycle pump gets warm after inflating a tyre quickly. Using the particle model, explain briefly why this happens.
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Compressing the gas increases the speed and kinetic energy of the particles, which increases the temperature and causes the pump to get warm.
Common mistakes: Assumes friction alone is responsible; Mentions molecules 'rubbing together'
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Marking points
B1 · 1 mark · States that compression increases speed/kinetic energy of particles.
B1 · 1 mark · Links increase in kinetic energy to increase in temperature/warmth.
Worked solution
When you compress air quickly, you do work on the gas, increasing the kinetic energy of its particles. This causes the temperature to rise, making the pump feel warm.