Charles's Law

Definition

At constant pressure, heating a gas makes it expand: volume is directly proportional to absolute temperature.

$\frac{V_1}{T_1} = \frac{V_2}{T_2}$

Technical definition

Charles's law states that for a fixed amount of gas at constant pressure, volume is directly proportional to absolute (Kelvin) temperature. It is the constant-pressure special case of the ideal gas law.

Example

A balloon filled at 20 C (293 K) and heated to 60 C (333 K) at constant pressure expands to about 1.14 times its original volume.

Common confusion

Temperature MUST be in Kelvin. Using Celsius gives wrong answers because the relationship passes through absolute zero, not 0 C.