The law of mass action is one example of Le Chatelier's principle, that the equilibrium in a chemical system responds to a change in concentration, temperature, or pressure by shifting in the direction which partially counteracts the imposed perturbation. Thus if the reaction considered were exothermic, such that heat could formally be regarded as one of the products, an increase in temperature would shift the equilibrium to the left. If A, B and C were gases, an increase in total pressure would shift the equilibrium to the right.