And this is known as an endothermic reaction. So once again, endothermic reaction is a reaction in which the energy of product is higher than the end of reactants and energy is used up or inputted into the system for that reaction to take place. So once again, anytime we have an endothermic reaction going this way, going the forward direction, we have an endothermic reaction going in the backward or reverse direction. So once again, to sum this information up, anytime we form a bond, energy is released. Anytime we want to break a bond, energy needs to be inputted into our system, into the molecule. Now, what is bond association energy?