آنتالپی

Enthalpy () is the sum of a thermodynamic system's internal energy and the product of its pressure and volume. It is a state function in thermodynamics used in many measurements in chemical, biological, and physical systems at a constant external pressure, which is conveniently provided by Earth's ambient atmosphere. The pressure–volume term expresses the work W that was done against constant external pressure P_\text{ext} to establish the system's physical dimensions from V_\text{system, initial}=0 to some final volume V_\text{system, final} (as W=P_\text{ext}\Delta V), i.e. to make room for