Boyle's Law

In-depth explanation of Boyle's Law

Boyle's law states that at constant temperature and fixed amount of gas, the volume is inversely proportional to the pressure, so PV is constant. It follows from kinetic theory: when a gas is compressed, the same number of particles strike the walls more often in a smaller space, which raises the pressure. Mathematically P1V1 = P2V2, so a plot of P against V is a hyperbola while a plot of P against 1/V is a straight line. The law explains breathing, because the diaphragm enlarges the chest and lung volume, lowering the pressure inside so that air flows in. Gas syringes and pumps also rely on it.

Going deeper: Boyle's Law

Key ideas: Use P1V1 = P2V2 for a fixed amount of gas at constant temperature; any consistent pressure and volume units cancel, so no conversion to SI is needed. The product PV is constant along an isotherm, so isotherms are hyperbolas. Typical use: a diver's lung volume halves at about 2 atm in water at 10 m depth.

Common mistakes and connections: Students apply it when temperature or moles also change, which is invalid. Another error is mixing gauge and absolute pressures. A pressure doubling does not mean the volume halves if the gas leaks or is heated. Connects to the combined gas law, work of compression and breathing mechanics.

Visualization of Boyle's Law

At constant temperature pressure and volume are inversely proportional: halving the volume doubles the pressure, so PV stays constant. The interactive lesson shows this as a live animation or chart.

Worked example and use case

A 2.0 L sample of gas at 1.0 atm compressed to 0.5 L at the same temperature has a pressure of 4.0 atm.

Where Boyle's Law fits in States of Matter & Solutions

Boyle's Law is topic 8 of 109 in States of Matter & Solutions.

Related topics

• PressureBeginner
• BarometerBeginner
• Standard Temperature and PressureBeginner
• Charles's LawBeginner
• Gay-Lussac's LawBeginner
• Avogadro's LawBeginner

Browse all 109 topics in States of Matter & Solutions