According to the Le Châtelier's Principle, when a system in equilibrium is subjected to a change in concentration, volume, pressure, or temperature, the system responds in such a way as to minimize the effect of the imposed change. This is accomplished by re-establishing equilibrium through a shift in the equilibrium constant, which is determined by the ratio of forward and reverse reaction rates. For example, if the concentration of a reactant is increased, the reaction will shift in the direction that consumes the reactant, in order to reduce the concentration of the reactant and re-establish equilibrium. Similarly, if the volume of the system is decreased, the reaction will shift in the direction that produces more moles of the product, in order to increase the pressure and re-establish equilibrium.