Introduction: If you have ever taken a football outside on a cold day after inflating it inside, you might have noticed that the football shrinks slightly in colder weather. This idea of changes in the volume of a gas with changes in the temperature of a gas is known as Charles' Law. The equation for Charles' Law is shown below:

[math]V_1/T_1 = V_2/T_2[/math], where V=volume and T= temperature

It is important to note that Charles' Law is a consequence of changes in the properties of the temperature and volume of a gas at a given pressure. That is, the pressure is constant. This equation takes into consideration the average kinetic energy of the particles, since temperature is included, as well as the space between the particles of the gas, also known as a volume.

According to Charles' Law, as volume increases, temperature also increases. Conversely, as volume decreases, temperature also decreases. Based on this relationship between the variables in the equation, since increasing one variable leads to an increase in the other variable, Charles' Law is known as a direct relationship. Charles' Law can be represented using a line with a positive slope. However, it is worth noting that Charles' Law generally does not have negative values, since volume is not negative.