I've been musing about thermal conductivity and came upon the following question.
Heat is transported through matter by molecules passing their kinetic energy onto other molecules, or simply by the matter itself being transported.
In gases, the first option should happens way more slowly than in bodies or liquids as the molecules are less likely to have contact. The second, however, happens very quickly.
If we now think of a small amount of a gas with a some temperature being released into a larger amount of gas with a different temperature, all of which is confined in a box, then the smaller amount will diffuse into the box, both gases become mixed.
If the pressure is low and the molecules rarely meet, they should be able to keep their respective temperatures and the overall temperature is not a single value, but a spectrum - with two spikes in this case.
I would expect the gases' temperatures to merge the faster the more pressure the gases are under.
I was wondering especially if the effect would be strong for air in the range of Earth's surface temperatures.
If not, how low would pressure have to for the effect to become relevant?
I'm sure there will be nice diagrams by physicists that describe the speed of the temperature merging process depending on pressure and temperature, but I don't know the right buzzwords to Google for them.
Can somebody help me out?