Charles' law and Boyle's law are both examples of "empirical gas laws." What this means is that they wre originally discovered by doing careful measurements of a gas' pressure P, temperature T and volume V. By holding the temperature of the gas fixed and varying its volume, Boyle observed that the larger the volume got, the lower the pressure of the gas became. This inverse relations ship, P = K/V, is Boyle's law. Similarly, by holding P fixed and varying V, Charles found that the larger the volume got, the higher the temperature became: this direct relationship, V = bT, is Charles' law. in creasing the volume decreases the number of collisions of gas molecules with the walls per unit time, which decreases the pressure. Charles' law is harder. By increasing T we increase the average energy of all the molecules.