For any change that occurs in a chemical system, the equilibrium of that system will shift in order to counteract the change being imposed on that system. For example, if the temperature is increased for a reaction, and the forward reaction is endothermic, with an endothermic reverse reaction; the system will shift in order to dissipate the excess heat energy. Since an endothermic reaction takes in heat energy from the surroundings, this reaction will be favoured in order to use up the excess heat energy. Hence the shift in equilibrium will favour the reverse reaction.