Physical Chemistry Chapter 7 The phase rule SO liquid Critical oint riple point vapor Triple point: at which three different phases(,l, g) all simultaneously coexist in equilibrium. It occurs at a single definite pressure and temperature characteristic of the substance (outside our control e Critical point: at which(critical P and critical T)the surface disappears14 The Phase Rule Triple point: at which three different phases (s, l, g) all simultaneously coexist in equilibrium. It occurs at a single definite pressure and temperature characteristic of the substance (outside our control). T3 Tc P T Triple point Critical point vapor liquid solid Critical point: at which (critical P and critical T) the surface disappears. Physical Chemistry Chapter 7