Why do real gases deviate from the ideal gas laws at low temperatures?

1 Answer


Real gases tend to stick together briefly at low temperatures
Ideal gases bounce off each other like billiard balls with no interaction.


The ideal gas laws are based on ideal gas behavior. In ideal gas behavior there is no interaction between the gas molecules. The kinetic energy of the molecules and atoms is "completely" conserved in the collisions between the molecules and atoms.

Temperature is directly related to average kinetic energy. In classical physics kinetic energy is conserved in collisions. However at low temperatures the kinetic energy is such that the collision happen more slowly allowing time for the molecules and atoms to experience some interaction with each other. These interactions like London dispersion forces absorb some of the kinetic energy.

The loss of kinetic energy due to the interactions of the molecules and atoms changes the predicted gas molar volume in the ideal gas law, depending on whether the gas has predominantly attractive or repulsive forces.