Equilibrium

Le-Chatelier's principle is applicable to only systems in equilibrium. According to this, "if a system in equilibrium is subjected to any change (in temperature, pressure or concentration of reactants and products), the equilibrium shifts in that direction in which the change is minimised." Heterogenous system is a system in which the various reactants and products are in different phase (solid, liquid or gas) whereas in a homogeneous system the various reactants and products are in same phase.