effusion

Effusion is the process by which a gas escapes through a small opening in a container. This occurs when the hole's diameter is significantly smaller than the distance between gas molecules. According to Graham's law of effusion, lighter gases escape faster than heavier gases at the same temperature and density. This phenomenon is explained by the kinetic theory of gases, which relates the macroscopic properties of gases to the motion of their molecules. Effusion is distinct from diffusion, which is the intermingling of particles from a region of high concentration to one of low concentration.123