Defining Enthalpy

[Paul Adkisson 1D]

What exactly is enthalpy? I understand that when pressure is constant and all work is expansion work that enthalpy = heat, but what is enthalpy defined as when pressure is not constant? Furthermore, I know that heat is measured in Joules so it must be some form of energy, but what differentiates it from say kinetic energy or potential energy?

[Lucy Nakashima 1E]

Enthalpy is the heat of the reaction and allows us to monitor the energy changes that occur when the pressure is constant. Since the definition of enthalpy states that pressure is constant, we will always make that assumption in our calculations. To find the enthalpy, you find the sum of the internal energy of the system and the product of the pressure and volume of the system.