Thermodynamic transformation is a process by which a thermodynamic system passes from a state of thermodynamic equilibrium to another.

A thermodynamic system is in principle in a state of thermodynamic equilibrium when the main variables of the system (ie pressure, volume and temperature) do not experience any additional variation over time.

In the event that two or all of the above variables change (the variation of only one of them is impossible because they are all interconnected by an inverse or direct proportion ratio) we are in the presence of a thermodynamic transformation, which leads the system towards a another balance point.

The initial and final state of a transformation are identified by two values of the three quantities that define the state of a body: pressure, volume or temperature.

## Classification of thermodynamic transformations

In a thermodynamic transformation it can take place:

- exchanging work, but without exchanges of heat (for an adiabatic system: adiabatic transformation);
- exchanging heat, but without exchanging work; (for example, for an Isocora transformation)
- exchanging work and heat (for example, for an isobaric transformation or an isotherm)

A thermodynamic transformation can be reversible or irreversible; all real transformations are irreversible, since frictions can not be completely eliminated, so the condition of reversibility is only a theoretical approximation.

Other classifications of thermodynamic transformations are:

- Isothermal transformation: process at constant temperature.
- Isobaric thermodynamic transformation: constant pressure process.
- Isometric or isochoric transformation: process at constant volume.
- Isoenthalpic transformation: process at constant enthalpy.
- Isentropic transformation: constant entropy process.