The Gas Laws The gas laws are a set of laws which describe the experimental evidence and the ways the volume, pressure and temperature of a fixed mass of gas are related. Name of Law Definition- words Formula/ Relationship Apparatus Graph Qualitative explanation Questions Charles Law (Jacques Charles) States that the volume of a fixed mass of gas is directly proportional to its absolute temperature (on the Kelvin scale), provided that its pressure is kept constant. V α T V/T = constant V 1 /T 1 = V 2 /T 2 Apparatus
On absolute scale as well Qualitative explanation When a gas is heated, its molecules begin to move faster as the temperature of the gas rises. The molecules therefore collide more frequently and with each other as well as with the walls of the container. In addition, the molecules strike the walls harder at every collision. The increased rate of collision contributes to an increased pressure exerted by the gas and so if the gas is free to expand, it will do so until its pressure is once again equal to the external pressure. It should also be noted that the pressure of a gas at a given temperature is directly proportional to the concentration (number of molecules per unit volume) of the molecules. Hence, if the temperature of a gas is doubled, the volume of the gas would have to be doubled as well so that the concentration of the molecules would be halved, so that the external temperature will once again be equal to the internal temperature. So for example: if we have a container which has a volume of 10 cm 3 and we have 5 molecules moving in the container and let’s say that the external pressure is equal to the internal pressure.
- Fall '19