And what that basically means is in order to get from nothing to this volume and pressure, these molecules have to do work on the environment and displacing them in forming this structure, this sphere or the circle. So what enthalpy is, it's the total energy of the system plus the work that the system has to do on the environment in creating that system. And that's what enthalpy is. Now, enthalpy is a state function, which means that enthalpy is independent of the pathway and the reactions that lead to the system. In other words, enthalpy only depends on the current state of the system, okay? Now, enthalpy is also an external property, which also means that entropy depends on the amount of the system.