Abstract
For each thermodynamic system, it is possible to determine a relation between energy, entropy, and the work parameters (the volume only in the case of simple systems) that is called the Fundamental Relation of the system. We start first with closed systems with no chemical reactions for which the Equilibrium State Postulate determines, in general, the number of degrees of freedom and then it is generalized to open systems with variable chemical composition. The Fundamental Relation describes the set of all stable and metastable equilibrium states that the system can reach and the geometrical properties of the surface described by it determines the conditions of stability of equilibrium states. It can be represented in various forms according to the external constraints. The representations commonly used, in addition to that of Energy and of Entropy, are the Free Energy, the Enthalpy, and the Gibbs Potential and the general properties of isothermal, isobaric and isochoric transformations are discussed. The definition of the chemical potential is given and its physical meaning as the thermodynamic potential responsible of phase equilibria is shown.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
With the term “equivalent pressure”, we mean to cover those situations in which, in addition to the external pressure in the strict sense (for example, exerted by the atmosphere on a movable piston) other forces applied to the mobile piston act such as a weight determined on a horizontal piston of the given area.
- 2.
For a wider discussion on this topic, see [6].
- 3.
This denomination is due to Gibbs and, as we shall see, it is absolutely appropriate.
- 4.
In many texts designed for applications in engineering, however, it is useful to take the mass as a state variable.
- 5.
And to do this the observer should ensure an efficient flow of extensive quantities such as energy or volume.
- 6.
The rule of the “entropy increase” is an expression often used in a very rough manner. It can be considered correct strictly for isolated systems. In general, for systems in interaction with the external world this rule takes different expressions as we remarked in Sect. 4.3.2 all resulting from the requirement \(\hat{d}_{\,\mathrm {i}}S>0\), which is the only fundamental condition.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2019 Springer Nature Switzerland AG
About this chapter
Cite this chapter
Saggion, A., Faraldo, R., Pierno, M. (2019). The Fundamental Relation and the Thermodynamic Potentials. In: Thermodynamics. UNITEXT for Physics. Springer, Cham. https://doi.org/10.1007/978-3-030-26976-0_4
Download citation
DOI: https://doi.org/10.1007/978-3-030-26976-0_4
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-26975-3
Online ISBN: 978-3-030-26976-0
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)