In the ideal gas model, intermolecular forces are assumed to be zero except during collisions.

The mean free path increases as the number density of gas molecules decreases.

The formula for the mean free path $\lambda$ in an ideal gas (number density $n$, molecular diameter $d$) is:

The mean free path of a gas molecule depends on:

The molar heat capacity at constant volume $C_V$ for a diatomic ideal gas (ordinary temperatures) is:

The total number of degrees of freedom of a diatomic ideal gas molecule at ordinary temperatures is: