Gay-Lussac's Law

Gay-Lussac's Law applies to a fixed amount of gas kept at constant volume: if the temperature increases, the pressure rises in direct proportion because gas molecules move faster and hit the container walls more forcefully and more often. The relationship works with absolute temperature, so values must be in kelvin rather than Celsius. It is one of the gas laws that follows from the ideal gas law when volume and amount of gas do not change.

Use this law for sealed, rigid containers such as aerosol cans, pressure cookers, gas cylinders, or laboratory vessels where the volume stays constant. It is also useful in chemistry and physics problems asking how pressure changes when a gas is heated or cooled without changing its container size.

• Using Celsius instead of kelvin
• Applying the law when the container volume changes
• Cross-multiplying incorrectly or solving for the wrong pressure value