phase rule

noun Physical Chemistry.

a law that the number of degrees of freedom in a system in equilibrium is equal to two plus the number of components less the number of phases. Thus, a system of ice, melted ice, and water vapor, being one component and three phases, has no degrees of freedom. Compare variance(def 4).

Origin of phase rule

First recorded in 1895–1900

Words nearby phase rule

phase in, phase inverter, phase microscope, phase modulation, phase out, phase rule, phase shift keying, phase space, phase speed, phase transition, phase velocity

British Dictionary definitions for phase rule

phase rule

noun

the principle that in any system in equilibrium the number of degrees of freedom is equal to the number of components less the number of phases plus two See also degree of freedom, component (def. 4)

Scientific definitions for phase rule

phase rule

A rule used in thermodynamics stating that the number of degrees of freedom in a physical system at equilibrium is equal to the number of chemical components in the system minus the number of phases plus the constant 2. Also called Gibbs phase rule See also phase transition state of matter.