State and Path functions (Point and path properties)



State (or Point) Functions

  • State functions, also called thermodynamic variables, state quantities, or a functions of state describe the momentary condition of a thermodynamic system. Regardless of the path by which a system goes from one state to another — i.e., the sequence of intermediate states — the total change in any state variable will be the same. This means that the incremental changes in such variables are exact differentials.
  • Examples: internal energy, enthalpy, entropy, pressure, temperature, volume, etc.
  • Various thermodynamic diagrams have been developed to model the transitions between thermodynamic states.