When a gas is heated at constant pressure, what happens to its volume according to Charles' Law?

When a gas is heated at constant pressure, its volume increases, which is in line with Charles' Law. This law states that the volume of a gas is directly proportional to its absolute temperature when pressure is held constant. As the temperature rises, the kinetic energy of the gas molecules increases, causing them to move more vigorously. This increased molecular motion leads to a greater volume as the gas expands to accommodate the increased energy.

In practical terms, when you heat a balloon filled with air, the air inside expands as the temperature increases, causing the balloon to enlarge. This relationship holds true for any gas as long as the pressure is not allowed to change. Therefore, when heated at a constant pressure, the volume of the gas must increase, confirming that the correct answer is indeed that it increases.