Transcript: How is the Kelvin temperature scale related to the velocity of particles in a gas? The theory was worked out a hundred and fifty years ago by James Clark Maxwell and Ludwig Boltzmann. Essentially we are relating the kinetic energy of a particle (0.5mv2) to the temperature measured on the Kelvin scale. The constant of proportionality is called the Boltzmann constant. It has a very small numerical value, 1.4 times 10-23 joules per Kelvin. Using this scaling we can see that the temperature of a gas is proportional to the velocity squared of the particles in the gas and proportional to the mass or atomic weight of the particles. Inverting this relation we can see that the velocity of the particles is related to the square-root of the temperature and to one over the square-root of the mass of the particles.