Pressure from particle collisions
In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
GCSE Physics resources
AQA GCSE Particle model of matter
Gas Pressure and Temperature
In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
Start here
The revision snapshot
In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
By the end, you should be able to:
- Explain pressure from particle collisions.
- Apply the particle model of matter model, evidence or method to an unfamiliar exam context.
- Recognise and correct this wrong turn: Saying pressure comes from particles touching each other.
Before you revise
Diagnostic question
Choose an answer from memory. Your result tells you what to watch for in the guide.
Core revision guide
Learn the model, then use it
Gas Pressure and Temperature questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.
Build the physics picture
Gas pressure is caused by particles colliding with the container walls. Heating gives particles more kinetic energy, so collisions are more frequent and harder. Reducing volume makes the same particles strike the walls more often, increasing force per unit area.
The relationship for this guide
Constant-temperature gas relationship: pV = constant (Pa, m³). Choose each relationship from the physical change described, convert quantities into compatible units and keep the unit beside the final answer.
Misconception clinic
Replace the tempting answer
Read each belief, say what is wrong with it, then compare your correction.
Tempting idea: Saying pressure comes from particles touching each other.
Use instead: In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
Tempting idea: Forgetting this is Separate Physics Higher content.
Use instead: Gas pressure is caused by particles colliding with the container walls. Heating gives particles more kinetic energy, so collisions are more frequent and harder. Reducing volume makes the same particles strike the walls more often, increasing force per unit area.
Tempting idea: Saying temperature adds particles.
Use instead: Use a particle-level chain: temperature/volume change → particle motion or spacing → collisions → force per area → pressure.
Retrieval practice
Quick checks
Explore the relationship
Gas pressure collision model
Use absolute temperature and volume to compare pressure with a gas at 20 °C and its starting volume.
What to notice: use the readout to describe how one variable changes when the other is controlled.
Worked examples
See the method being built
These examples expose the difference between a secure pressure from particle collisions method and the common error “Saying pressure comes from particles touching each other.”.
Example 1 · Heat a sealed can
Explain why pressure rises when a sealed rigid gas container is heated.
- Temperature raises average kinetic energy.
- Particles move faster.
- Collisions are more frequent and harder.
Show the answer
Faster particles collide with the walls more often and with greater force, so force per area and pressure increase.
Example 2 · Compress a syringe
Explain why pressure rises when a syringe is compressed at constant temperature.
- Number of particles stays the same.
- Volume decreases.
- Wall collisions become more frequent.
Show the answer
In the smaller volume, particles hit the walls more often, increasing force per area and pressure.
Example 3 · Cooling a balloon
A balloon becomes smaller in a cold room. Explain using particles.
- Cooling slows particles.
- Internal pressure falls relative to outside pressure.
- The flexible balloon contracts.
Show the answer
Slower particles collide less often/less forcefully, so internal pressure falls and the balloon contracts until pressures balance.
Exam precision
Exam technique: Pressure from particle collisions
Do this: Use a particle-level chain: temperature/volume change → particle motion or spacing → collisions → force per area → pressure.
Independent practice
Exam-style questions
Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.
1. State the cause of gas pressure.
[1 mark]Show marking guidance and model answer
Marking guidance: Award one mark for the precise statement shown in the model answer.
Model answer: Collisions of gas particles with the container walls.
2. Explain why a tyre’s pressure increases after driving.
[3 marks]Show marking guidance and model answer
Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.
Model answer: The air warms, particles move faster and collide more frequently/forcefully with the tyre walls.
3. Explain why gas pressure increases when volume decreases at constant temperature.
[3 marks]Show marking guidance and model answer
Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.
Model answer: The same particles have less space and collide with walls more often.
4. State what happens to average kinetic energy when gas temperature rises.
[1 mark]Show marking guidance and model answer
Marking guidance: Award one mark for the precise statement shown in the model answer.
Model answer: It increases.
5. Why should an aerosol can not be heated?
[2 marks]Show marking guidance and model answer
Marking guidance: 2 marks are available for relevant, linked physics points that match the model answer.
Model answer: Heating increases gas pressure, which can make the can rupture.
6. Describe one variable to keep constant when investigating pressure against temperature.
[2 marks]Show marking guidance and model answer
Marking guidance: 2 marks are available for relevant, linked physics points that match the model answer.
Model answer: Keep the gas volume and amount of gas constant using a sealed rigid container.
Questions pupils ask
Gas Pressure and Temperature FAQs
What is the main idea in Gas Pressure and Temperature?
In a sealed rigid container, heating increases particle speed and collision force/frequency, so pressure rises. Compressing a gas increases collision frequency with the walls when temperature is constant.
What mistake should I avoid in Gas Pressure and Temperature?
Saying pressure comes from particles touching each other. Gas pressure is caused by particles colliding with the container walls. Heating gives particles more kinetic energy, so collisions are more frequent and harder. Reducing volume makes the same particles strike the walls more often, increasing force per unit area.
Useful next steps
Connect this guide to your next task
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