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 quick 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 using precise physics language.
- Apply the relevant equations, diagrams or practical method to an exam-style situation.
- Use the mini quizzes and practice answers to identify and correct a misconception.
Core learning content
Learn the idea before you practise it
Start with this short teaching sequence for Gas Pressure and Temperature. Read the model, use the visual, then test your recall before moving into examples and exam practice.
Build the 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.
Use the right relationship
Choose a relationship because of the physical change in the question, not because it is familiar. Density: ρ = m ÷ V (kg/m³, kg, m³). Specific heat capacity: E = mcΔθ (J, kg, J/(kg °C), °C). Pressure: p = F ÷ A (Pa, N, m²). Keep the unit next to each value while you substitute.
What a strong answer does
Use a particle-level chain: temperature/volume change → particle motion or spacing → collisions → force per area → pressure. Before writing, underline the command word and identify the information that matters. Keep a calculation as equation, substitution and answer with unit; keep an explanation as a linked chain using because, so or therefore. Finish by checking that the final sentence answers the exact context in the question and that the number, direction or conclusion agrees with the evidence given.
Retrieval practice
Quick checks
Answer without looking back first. The feedback explains the model, so a wrong answer still helps you learn.
Mini quiz 1
Check the core idea
Mini quiz 2
Apply the model
Mini quiz 3
Use exam precision
Try it
Gas pressure collision model
How do temperature and volume change the collisions that produce pressure?
What to notice: the readout and written explanation remain available if you do not use the controls.
Worked examples
See the method being built
Cover the answer, attempt the method and then compare your physics language as well as the number.
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.
Misconception clinic
Common wrong turns
Each of these is tempting because it sounds almost right. Replace it with the precise physics before you meet it in a question.
- Saying pressure comes from particles touching each other.
- Forgetting this is Separate Physics Higher content.
- Saying temperature adds particles.
Independent practice
Exam-style questions
Use the working space first. Reveal the guidance only after you have committed to an answer, then improve the exact part that would gain the next mark.
1. State the cause of gas pressure.
[1 mark]Show answer and marking guidance
Collisions of gas particles with the container walls.
2. Explain why a tyre’s pressure increases after driving.
[3 marks]Show answer and marking guidance
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 answer and marking guidance
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 answer and marking guidance
It increases.
5. Why should an aerosol can not be heated?
[2 marks]Show answer and marking guidance
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 answer and marking guidance
Keep the gas volume and amount of gas constant using a sealed rigid container.
Questions pupils ask
GCSE Physics FAQs
What is the key idea in Gas Pressure and Temperature?
Use a particle model to explain density, changes of state, internal energy and gas pressure. Keep particle spacing, particle motion and energy separate.
How should I practise Gas Pressure and Temperature?
Read the snapshot, attempt the worked examples without looking, complete the mini quizzes and then use the practice questions to check your wording and method.
Next step
Keep your revision moving
Physics sticks when you move between explanation, retrieval and application.