This animation shows Helium (He) diffusing into two different states of air (a mix of O2 and N2): gaseous air and liquid air. Air will turn into the liquid state at approximately -200 °C, and in condensing has a density approximately 900 times greater than gaseous air.
Molecules in the gaseous state will diffuse faster than those in the liquid state because of differences in density. In gases, the mean free path – the distance a molecule can travel before colliding with another molecule or barrier – is greater than in liquids.
This animation has been created to show the effect of state only. It does not take into account the temperature differences between these two samples that would occur in real life, or other factors that would influence rates of diffusion.