This Demonstration shows the diffusion of two gases from opposite ends of a tube. The root mean square velocity of a gas is given by , where is the gas constant 8.314 J/mol K, is the temperature in K and is the molecular weight in kg/mol. The temperature is set at 298 K to show diffusion under standard conditions. This Demonstration shows how the molecules of gas 1 and gas 2 diffuse toward each other and intermingle in a one-meter tube. You can select from several diatomic and noble gases.