The Gas Laws 4.8. Molecular motion and Temperature 4.10. Liquids and Solids 4.11. Heat Engines 4.14. Fate of the Universe 4.16.
Temperature is a measure of the energy of random motion in the molecules of a substance.
The measure of mass per unit volume is the density. The deeper you go, the more the pressure. It also depends on the gravitational attraction of the planet you're on. Ice bergs in water are like big ice cubes.