In thermodynamics, state variables, state parameters or thermodynamic variables describe the momentary condition of a 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. Below are some examples of state variables:
- Density (ρ)
- Energy (E)
- Helmholtz free energy (A)
- Gibbs free energy (G)
- Enthalpy (H)
- Internal energy (U)
- Mass (m)
- Pressure (p)
- Entropy (S)
- Temperature (T)
- Volume (V)
- The amounts of each of the chemical components { ni }, expressed as numbers of moles or molecules
