A sealed metal container holds a fixed quantity of gas. The container is placed in a furnace and its temperature rises. Explain how the behaviour of the gas particles inside the container accounts for the increase in pressure on the container walls.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Higher temperature gives the gas particles greater kinetic energy, so they move faster.
The faster particles collide with the container walls more often.
Each collision exerts a larger force because the particles have more momentum.
Pressure is the perpendicular force per unit area on the walls, so the increased force from more frequent and harder collisions raises the pressure.
The faster particles collide with the container walls more often.
Each collision exerts a larger force because the particles have more momentum.
Pressure is the perpendicular force per unit area on the walls, so the increased force from more frequent and harder collisions raises the pressure.
Examiner tips
- Use the word ‘exert’ to show force; link temperature to kinetic energy. Mention both frequency and force of collisions. Define pressure as force per unit area. Keep the answer concise and use correct terminology.
Common mistakes
- Saying the particles simply ‘push harder’ without linking to kinetic energy. Forgetting to mention the increased collision frequency. Using vague terms like ‘more pressure’ without explaining the mechanism.
Mark scheme (4 marks)
- Higher temperature means the gas particles have greater kinetic energy / move faster
- The faster-moving particles collide with the container walls more frequently
- Each collision exerts a greater force on the walls because the particles are moving faster / have more momentum
- Pressure is the perpendicular force per unit area on the container walls, so greater force from more frequent/harder collisions means higher pressure
Key terms in this question
pressure · temperature · gas particles
Related
- All WJEC GCSE Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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