Enthalpy

In thermodynamics, enthalpy is the sum of the internal energy U of a system and the product of pressure p and V of the system,

$H=U+pV\,$

Enthalpy used to be called "heat content", which is why it is conventionally indicated by H.

The work term pV has dimension energy, in SI units joule, and H has the same dimension. Enthalpy is a state function, a property of the state of the thermodynamic system and its value is determined entirely by the temperature T, pressure p, and composition N_A, N_B, ... (molar amounts of substances A, B, ... ) of the system and not by its history.

To be continued