# How is heat transferred (microscopically)?

Microscopically talking, how is heat transferred and the temperature of bodies changed?

For example, if a hot material touches a colder piece of conductive metal, how does the heat and energy transfer from one body to another? I think the result is that the velocities of the molecules of the colder body raise ( $T \propto v_{th}^2)$ until they reach the thermal velocity of the hotter one and establish a thermic equilibrium. What is the mean through which this happens? Collisions between the molecules of the two surfaces in contact? Phonons interaction?

• This is well document topic and so I am surprised that you have asked such a general question about this phenomena. Sep 12, 2018 at 14:21
• I saw some things online about collisions with molecules (for example gasses) but I was thinking also about rotational kinetic energy (is that exchanged also by collisions?) about some characteristic potentials (are attractive fields involved in this exchange between two bodies?), collisions between electrons and phonons to thermalize, I thought I couldn't be that simple, microscopically. Sep 12, 2018 at 14:27
• If I thought about energy exchange, also an electromagnetic wave, for example, could raise the temperature modifying the velocity of the polar molecules Sep 12, 2018 at 14:28
• There are three heat transference types. I don't think the phenomena is very well explained on the web. In an imaginary experiment, where there are no molecules around, the piece of metal will emit radiation. So part of the heat will be transfered in terms of collisions, part of it in terms of radiation.
– user153036
Sep 12, 2018 at 14:47
• Phonons are not necessarily involved. You may define phonons only on crystals (periodic lattice systems). Heat transfer by contact is more general than that, it can be between any two bodies (of matter). Sep 12, 2018 at 15:00