Me! what are the theoretical properties of a gas at a temperature of 0 kelvin?

The molecules of the gas will stop moving at all, and the gas will change into solid state

Explanation:

In a gas, the average kinetic energy of the particles is directly proportional to the temperature of the gas, according to the equation (valid for ideal monoatomic gases):

where

Ek is the average kinetic energy of the particles

k is the Boltzmann constant

T is the temperature of the gas in Kelvin

Therefore, we see from the relationship that at 0 K the kinetic energy of the particles will become zero: this means that the particles will not move at all, and also that the gas will actually be a solid, which is the state with lowest energy among the three states of matter.

Of course, 0 K is just an ideal condition, which is not reached in real life.