The enthalpy H of a thermodynamic system is defined as the sum of its internal energy and the product of its pressure and volume:
H = U + p V ,
where U is the internal energy, p is pressure, and V is the … See more

The above expression of dH in terms of entropy and pressure may be unfamiliar to some readers. There are also expressions in terms of more directly measurable variables such as temperature and pressure: … See more

The U term is the energy of the system, and the p V term can be interpreted as the work that would be required to "make room" for the system if the pressure of the environment remained constant. When a system, for … See more

In order to discuss the relation between the enthalpy increase and heat supply, we return to the first law for closed systems, with the physics sign convention: dU = δQ − δW, where the heat δQ is supplied by conduction… See more

In thermodynamics, one can calculate enthalpy by determining the requirements for creating a system from "nothingness"; the mechanical work required, p V , differs based upon the conditions that obtain during the … See more