In thermodynamics, equation of state or state equation is a mathematical expression that defines the state of a given system. State equations, if the variables are independent quantities, are generally of the following format: [1]

f(P, V, T) = 0

This form applies particularly for systems comprised of homogenous fluids. In this scenario, the state of the system is completely determined by any two of the three state variables. In more complicated systems, state functions come into play.

The ideal gas equation (1662-1893), which describes the state of an ideal gas, is the simplest type of state equation.

The van der Waals equation (c.1690), which describes the ideal gas system as the vapor-liquid state begins to be approached, wherein intermolecular interactions and particle volume effects need to be taken into account, is the next simplest equation of state.

1. Fermi, Enrico. (1936). Thermodynamics (pg. 2). Prentice-Hall.

External links
Equation of state – Wikipedia.
Equation of state (cosmology) – Wikipedia.

TDics icon ns