
Boltzmann constant
A constant, k, involved in the equation for average velocity. k = 1.38×10^{23} J/K

Diffusion
Diffusion is the spread of one substance through another.

Effusion
Effusion is the rate at which a gas passes through a small hole into a vacuum.

Kinetic energy
E_{k} = 1/2mv^{2}

Kinetic molecular theory
A theory that models the interaction between individual gas molecules. See the summary for more details.

MaxwellBoltzmann speed distribution
The distibution attained when molecule speed is set against the number of molecules sharing that speed.

Mean free path
The mean distance a molecule travels before it impacts another molecule; given the huge number of collisions in a gas, the mean free path is vastly smaller than any typical room or container. The equation for mean free path:
λ =

m_{p}
The most probable velocity at which the most molecules in a gas travel. The formula for most probable velocity is:
v_{p} = =

Root mean square velocity
An equation to measure the typical velocity of molecules in a gas.
v_{rms} = = =
Terms
Formulae
Average velocity 

Kinetic energy  E_{k} = 1/2mv^{2} 
Mean free path 

Formule for most probable velocity 

Formula for root mean square velocity 
