Hello. I am a thermodynamics novice trying to gain a better understanding of state functions, particularly enthalpy. I understand that enthalpy is defined as "A measure of the total energy of a thermodynamic system, including internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure." The equation: ΔH=ΔU(internal energy) + ΔPV confuses me b/c ΔU= q(heat added) - w(work done by system on environment) so ΔH really means: ΔH=q - w + ΔPV There are two terms of work (w and ΔPV) and b/c of the opposite sign, they cancel out, leaving only q. This means ΔH= q which is at odds with the accepted definition of enthalpy. Where did I mess up?