Question

what is enthalpy of a substance​

Answer 1

Answer:

Enthalpy, the sum of the internal energy and the product of the pressure and volume of a thermodynamic system. ... In symbols, the enthalpy, H, equals the sum of the internal energy, E, and the product of the pressure, P, and volume, V, of the system: H = E + PV.

Answer 2

Answer:

Enthalpy of a substance is defined as the internal energy of the substance + pressure energy per unit mass of the substance. The reason for defining such kind of relationship is that under constant pressure system the change of this property (enthalpy) denotes the heat added or removed from the system.