Final answer:
Charles's law states that the volume of a gas is directly proportional to its absolute temperature at constant pressure.
Step-by-step explanation:
The relationship in which the volume of a given amount of gas is directly proportional to its absolute temperature at constant pressure is known as Charles's law. This law, named after the French scientist Jacques Alexandre César Charles, can be mathematically stated as V = const. T, where V represents the volume of the gas and T is the absolute temperature in kelvins. The direct proportionality means that as the temperature of a gas increases, its volume increases, provided the pressure remains unchanged.