Thermodynamic State Variables

Beyond simple temperature change, thermodynamics is really about tracking how a whole set of a system's measurable properties change together as it gains or loses energy. Before that tracking can be done precisely, we need a formal vocabulary: what exactly counts as a state variable of a system, when a system counts as being in full thermodynamic equilibrium, how its state variables relate to each other through an equation of state, and how all of this is captured vis …