Which statement correctly describes Charles' Law?

Which statement correctly describes Charles' Law?

• A. At constant pressure, volume is directly proportional to absolute temperature
• B. At constant volume, pressure is directly proportional to temperature
• C. At constant temperature, volume is proportional to pressure
• D. At constant temperature, volume is inversely proportional to temperature

Answer: (A)

Charles' Law describes how the volume of a gas changes with temperature when pressure is kept constant. It states that the volume is directly proportional to the absolute temperature (measured in Kelvin). Using the Kelvin scale matters because it starts at zero, so increasing temperature truly corresponds to increasing volume; if the gas could expand freely, doubling the Kelvin temperature would double the volume. Therefore, the best statement is the one that says: at constant pressure, volume is directly proportional to absolute temperature. The other options describe different relationships: constant-volume with temperature affecting pressure (Gay-Lussac’s law), constant-temperature behavior where volume would be inversely related to pressure (Boyle’s law), or an incorrect link between volume and temperature when temperature is held constant.

Charles' Law describes how the volume of a gas changes with temperature when pressure is kept constant. It states that the volume is directly proportional to the absolute temperature (measured in Kelvin). Using the Kelvin scale matters because it starts at zero, so increasing temperature truly corresponds to increasing volume; if the gas could expand freely, doubling the Kelvin temperature would double the volume.

Therefore, the best statement is the one that says: at constant pressure, volume is directly proportional to absolute temperature. The other options describe different relationships: constant-volume with temperature affecting pressure (Gay-Lussac’s law), constant-temperature behavior where volume would be inversely related to pressure (Boyle’s law), or an incorrect link between volume and temperature when temperature is held constant.