Thermodynamics: the study of systems involving energy in the form of heat and work.

The First Law of Thermodynamics: Q = ΔE_int + W

Q represents heat added to a system (or removed if it is negative)

ΔE_int is the change in internal energy of the system. This is directly proportional to the change in temperature.

W is the work done by the system.

The First Law is often written as ΔE_int = Q - W