Details

Autor(en) / Beteiligte

• Smith, J. G.
• Schmidt, B. E.

Titel

On the state principle of classical thermodynamics

Ist Teil von

• American journal of physics, 2024-06, Vol.92 (6), p.450-454

Ort / Verlag

Woodbury: American Institute of Physics

Erscheinungsjahr

2024

Link zum Volltext

Quelle

AIP Journals Complete

Beschreibungen/Notizen

• We discuss the state principle of classical thermodynamics, namely that the thermodynamic state of a simple compressible system can be uniquely determined by specifying two independent properties. We show that for certain combinations of properties, one is not guaranteed to arrive at a unique state. This caveat to the state principle is illustrated with three examples, two involving liquid water and a third using real gases. Finally, we show that to guarantee a unique state for a simple compressible system, the required two independent properties must be chosen from the trio consisting of a thermodynamic potential and its two natural variables. Editor’s Note: The state principle of classical thermodynamics asserts that the state of a simple compressible system can be uniquely determined by specifying two properties, such as temperature and pressure. However, there are situations where such a specification does not guarantee a unique state; for example, specifying the pressure and temperature of liquid water around its freezing point gives two possible volume states. In this paper the authors explore how to guarantee a unique state by choosing two properties from the trio of a thermodynamic potential and its two natural variables. A handy table of results lists 12 pairs of intensive variables that are guaranteed to specify a unique state for a single-phase, single-component substance. Appropriate for intermediate-level thermodynamics students.