phase rule

noun

Physical Chemistry.

1. 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.

phase rule

noun

1. 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

phase rule

1. 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.

2. Also called Gibbs phase rule

3. See also phase transition state of matter

Word History and Origins

Origin of phase rule¹

First recorded in 1895–1900