Whose law says gas volume increases with temperature if pressure stays constant?

Charles’s law is named after Jacques Charles, whose gas experiments in the late 18th century showed that gases expand when heated. If pressure is kept constant, a gas occupies more volume at higher temperature and less volume when cooled. The law is one of the classic gas laws and is used in understanding balloons, engines, and atmospheric behavior. Like other gas laws, it uses kelvin temperature for the direct proportionality.