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Boyle's Law

What happens to a gas when you squeeze it?

Try it

Drag the piston down and watch the numbers.

Interactive Simulation

Drag the piston

Drag the piston up or down to change the gas volume, or use the arrow, page up, page down, home and end keys.

Pressure

100kPa

Volume

100cm³

Temperature300 KConstant

What changed

Watch the pressure and volume as you move the piston.

See the relationship

As volume decreases, pressure increases. The point stays on the curve because P × V never changes.

Pressure-volume graphVolume on the horizontal axis from 40 to 160 cubic centimetres. Pressure on the vertical axis from 50 to 250 kilopascals. The curve falls steeply and then flattens, so pressure drops as volume rises. Current state: volume 100 cubic centimetres, pressure 100 kilopascals.

Current100 kPa · 100 cm³

Why does this happen?

Squeezing the gas gives the particles less room, so they reach the walls sooner and hit them more often. More collisions on the same walls means more pressure.

Boyle's Law

At constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume.

Formula

P₁V₁ = P₂V₂

P = pressure · V = volume · T = temperature (constant)

Let's try one

A gas has a volume of 100 cm³ at a pressure of 100 kPa.

The volume is reduced to 50 cm³. What is the new pressure?