Past exam of the soft condensed matter course of the University of Cambridge / 2014 / Paper 1 / 1 / b / Solution

Young's equation gives ${\gamma }_{SV}-{\gamma }_{SL}={\gamma }_{LV}\cos \theta$. The interfacial-energy difference from two contact angles follows by subtracting the two equilibrium contact-angle equations, which eliminates the common solid–air energy:The water–solid interface has the larger energy. This assumes the same clean solid surface and equilibrium angles, without swelling or strong contact-angle hysteresis.