Study of heat changes.
Proportional to the average kinetic energy of the particles. The higher the temperature the faster the molecules move.
Zeroth Law of Thermodynamics:
Objects in thermal equilibrium are at the same temperature. Objects in contact will eventually come to thermal equilibrium.
1st Law of Thermodynamics (Law of Conservation of Energy):
Energy cannot be created nor destroyed in a chemical or physical process.
Energy lost/gained from the system is equal & opposite to that lost/gaines from the surroundings
Disorder or random-ness
2nd Law of Thermodynamics:
The total entropy of the universe can never decrease.