This is a great explanation. I have a masters in physics, so let me know if you have a deep question.

In class, we start by learning that “temperature” is a macroscopic quantity, and it is trying to describe the microscopic motion of particles. Heat transfer is really momentum transfer (of small things).

In grad school the class is labeled as statistical mechanics, because the coursework focuses on the statistics of it all.

Some cool concepts are things like heat capacity, which is the amount of energy it takes to change the temperature of a material. Water takes a lot of energy to change the temperature. We learn that this is because of the degrees of freedom that the molecule has. So a single atom can move in 3D, a pair of atoms like H2 can also spin along its axis, and H2O can spin along multiple axis. Each extra degree of freedom means it can store energy in more ways before a it “speed” increase (which is measured by temperature).

One useful application in life is diamonds: real diamonds need more energy to change temp. So if you touch it, and it’s cold, then it’s real. If it’s warm, then it’s fake.