Whose law describes how a gas volume changes with temperature?

Charles law states that, at constant pressure, the volume of a fixed amount of gas is directly proportional to its absolute temperature, so heating a gas makes it expand and cooling it makes it shrink. The relationship is credited to Jacques Charles, who studied it in the 1780s, and it was later published and refined by Joseph Gay-Lussac. This is why a balloon expands in warm air and contracts in the cold. The law is one of several gas laws that together describe how pressure, volume, and temperature are linked. It uses the absolute, or Kelvin, temperature scale.