Physical Chemistry Chapter 7 The phase rule Degree of freedom or Variance () the number of intensive variables that can be changed independently without disturbing the number of phases in a equilibrium The phase rule: a general relation among the variance f, the number of components c and the number of phases p at equilibrium for a system of any composition f=c-p+2 (7.7) no reactions8 The Phase Rule Degree of freedom or Variance (f): the number of intensive variables that can be changed independently without disturbing the number of phases in equilibrium. The phase rule: a general relation among the variance f, the number of components c and the number of phases p at equilibrium for a system of any composition. f = c – p + 2 (7.7) no reactions Physical Chemistry Chapter 7