Particle Motion and Pressure in Gases

This lesson covers how the particle model explains gas pressure, the relationship between temperature and pressure, and the relationship between pressure and volume ($pV = \text{constant}$pV=constant for a fixed mass at constant temperature). This is part of the AQA GCSE Combined Science Trilogy specification (8464, section 6.3.2).

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What Causes Gas Pressure?

Gas particles are in constant random motion, travelling at high speeds in all directions. When these particles collide with the walls of their container, they exert a force on the wall. The total force of many billions of collisions per second, spread over the area of the walls, creates pressure.

$\text{Pressure} = \frac{\text{Force}}{\text{Area}}$Pressure=AreaForce​

Exam Tip: When explaining gas pressure, always refer to particles colliding with the walls of the container. Do not say particles collide with each other — while they do, that is not what causes pressure on the container walls.

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Temperature and Gas Pressure (Constant Volume)

When the temperature of a gas in a sealed container (fixed volume) increases: