The Phase Rule (Gibbs)

The Gibbs Phase Rule describes how the number of chemical components and phases (states like solid, liquid, or gas) in a system determine its degrees of freedom—that is, how many conditions (such as temperature, pressure, or composition) can be varied independently without changing the number of phases present. Mathematically, it’s expressed as F = C - P + 2, where F is degrees of freedom, C is components, and P is phases. This rule helps understand and predict the conditions necessary for different phases to coexist or change within a system.