If the pressure of a gas remains constant, which law indicates that its volume varies directly with absolute temperature?

The correct answer is grounded in Charles' Law, which states that if the pressure of a gas remains constant, the volume of the gas is directly proportional to its absolute temperature measured in Kelvin. This relationship can be expressed mathematically as V/T = k, where V is the volume, T is the absolute temperature, and k is a constant.

As the temperature increases, the kinetic energy of the gas molecules also increases, causing them to move more vigorously and occupy a larger volume, provided that the pressure does not change. Conversely, if the temperature decreases, the volume will decrease proportionally as long as the pressure remains constant.

The other laws mentioned do not pertain to the relationship between volume and temperature at constant pressure. Boyle's Law relates pressure and volume while keeping temperature constant; Avogadro's Law connects volume to the amount of gas at constant temperature and pressure; Dalton's Law deals with the partial pressures of gases in a mixture. Thus, Charles' Law is the one that specifically addresses the volume-temperature relationship under constant pressure conditions.