The properties of gases and how they behave are described by a number of different laws. Charles’s Law relates the behavior of gases according to temperature. Boyle’s Law relates the pressure of a gas to its volume. Avogadro’s Principle explains how doubling the number of moles will double a gases volume. Gay-Lussac’s Law gives the relationship between pressure and temperature at a constant volume. Since all of these laws describe gases, they were combined to create the Combined Gas Law.