A fixed amount of gas is trapped inside a rigid container. Explain, in terms of gas particles, why the pressure of the gas increases when the temperature of the gas is increased.

Eduqas GCSE Physics — 2.2 The kinetic theory and gas pressure · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Increasing the temperature raises the average kinetic energy of the gas particles, so they move faster.
The faster particles collide with the walls more often.
Each collision is harder, giving a larger force on the wall.
Because the volume is fixed, the greater force per unit area raises the pressure.

Examiner tips

  • Use the word "increase" and link temperature to kinetic energy. Show the chain: temperature → kinetic energy → collision frequency & force → pressure. Mention that volume is constant to justify pressure rise.
  • Use concise, exam‑style language and avoid unnecessary words.

Common mistakes

  • Failing to mention that volume is constant. Confusing force with pressure. Using vague terms like "more energy" without linking to speed or collisions.

Mark scheme (4 marks)

  1. Increasing temperature increases the average kinetic energy (or speed) of the gas particles
  2. Particles collide with the walls of the container more frequently
  3. Each collision exerts a greater force on the walls (particles hit the walls harder)
  4. Greater force per unit area on the walls means higher pressure (volume is constant so pressure increases)

Key terms in this question

pressure · temperature

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