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Practice questions · Gas pressure

Every push is an impact.

Six original Cambridge-style questions on where gas pressure comes from, what heating does at fixed volume, what squeezing does at fixed temperature, and an everyday example.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Always argue from the collisions

More often, or harder, means more pressure.

01
[2 marks]

Explain, in terms of particles, how a gas exerts a pressure on the walls of its container.

  • The gas particles move and collide with the walls of the container. ✓
  • Each collision exerts a small force on the wall; many collisions per unit area give the pressure. ✓
02
Analysis
[3 marks]

A fixed mass of gas is sealed in a rigid container and then heated. Explain, in terms of the particles, why the pressure increases.

  • Heating increases the temperature, so the particles move faster. ✓
  • They strike the walls harder and more often (more collisions per second). ✓
  • The greater force per unit area means a higher pressure. ✓
03
Analysis
[2 marks]

A gas is slowly compressed into a smaller volume while its temperature is kept constant. Explain why the pressure increases.

  • In the smaller volume the particles have a shorter distance to travel before hitting a wall. ✓
  • So they hit the walls more often, and the pressure increases. ✓

The temperature is constant, so the speed of the particles does not change, only how often they hit.

04
Analysis
[2 marks]

A student says that when a gas is heated at constant volume, the pressure rises because the particles get bigger and there are more of them. Explain what is wrong with this.

  • The particles do not change size and their number does not change. ✓
  • The pressure rises only because the particles move faster, so they hit the walls harder and more often. ✓
05
[2 marks]

More gas is pumped into a sealed container of fixed volume, keeping the temperature the same. State and explain what happens to the pressure.

  • The pressure increases. ✓
  • There are now more particles, so there are more collisions with the walls each second. ✓
06
Analysis
[2 marks]

The pressure in a car tyre is found to be higher after a long, fast drive on a hot day than it was at the start. Explain why, in terms of the gas particles.

  • The air in the tyre has warmed up, so its particles move faster. ✓
  • They hit the inside walls of the tyre harder and more often, raising the pressure. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.