Which statement describes Charles' Law?

• A. At a constant temperature, the volume and pressure of a gas are inversely related.
• B. At a constant temperature, the volume and the temperature of a gas are directly related.
• C. At a constant pressure, the volume and temperature of a gas are directly related.
• D. At a constant volume, the pressure and temperature of a gas are inversely related.

Answer: (C)

Charles' Law says that when pressure is kept constant, a gas's volume changes directly with its temperature measured in Kelvin. In other words, V is proportional to T at fixed P, so V2 = V1 × (T2/T1). This happens because heating the gas makes the molecules move faster and push outward, so the volume expands while the pressure stays the same. That’s why the statement describing Charles' Law is the one where volume and temperature rise together at constant pressure.

For context, if temperature is held constant, pressure and volume relate inversely (as in Boyle’s behavior). And at a fixed volume, increasing temperature would increase pressure, not decrease it.