Enthalpy

Enthalpy (symbolized H, also called heat content) is the sum of the internal energy of matter and the product of its volume multiplied by the pressure. Enthalpy is a quantifiable state function, and the total enthalpy of a system cannot be measured directly; the enthalpy change of a system is measured instead. Enthalpy is a thermodynamic potential, and is useful particularly for nearly-constant pressure process, where any energy input to the system must go into internal energy or the mechanical work of expanding the system.

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Internal energy: The internal energy of a system (abbreviated E or U) is the total kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the total potential energy associated with the vibrational and electric energy of atoms within molecules or crystals. Internal energy is a quan...

State function: In thermodynamics, a state function, or thermodynamic potential, is any property of a system that depends only on the current state of the system, not on the way in which the system got to that state. (See the related Markov property.)...

System: :For the Macintosh operating system, which was called System up to version 7.5.5, see Mac OS....