Darwinism designates a distinctive form of evolutionary explanation for the history and diversity of life on earth. Its original formulation is provided in the first edition of On the Origin of Species in 1859.
The enthalpy - or internal energy - of a substance is a function of its temperature and pressure. The change in internal energy with respect to change in temperature at fixed pressure is the Specific Heat at constant pressure - cp.
Enthalpy itself is a thermodynamic potential, so in order to measure the enthalpy of a system, we must refer to a defined reference point; therefore what we measure is the change in enthalpy, Î´ H. The Î´ H is a positive change in endothermic reactions, and negative in heat-releasing exothermic processes. For processes under constant pressure, Î´ H is equal to the change in the internal energy of the system, plus the pressure-volume work that the system has done on its surroundings.