Gas Pressure and Volume [H]

This lesson covers the relationship between gas pressure and volume as required by the AQA GCSE Physics specification (4.3.3). This is Higher Tier only content, labelled [H]. You need to understand how changing the volume of a gas affects its pressure, and be able to use the equation linking pressure and volume (Boyle's Law) in calculations.

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Boyle's Law: Pressure and Volume

Boyle's Law states that for a fixed mass of gas at constant temperature:

The pressure of a gas is inversely proportional to its volume.

This means:

• If you decrease the volume (compress the gas), the pressure increases.
• If you increase the volume (expand the gas), the pressure decreases.

The mathematical relationship is:

p x V = constant (at constant temperature for a fixed mass of gas)

or equivalently:

p1 x V1 = p2 x V2

Where:

• p1 = initial pressure (Pa)
• V1 = initial volume (m3)
• p2 = final pressure (Pa)
• V2 = final volume (m3)