The collision theory proposes that reactants must collide with a certain minimum amount of energy to form products. In other words, for a chemical reaction to occur, the reactant molecules must collide with sufficient energy and in the correct orientation. If the collision has insufficient energy, the reactants will bounce off each other and not form any products. Therefore, the higher the frequency of successful collisions between reactant molecules, the higher the rate of reaction. The collision theory also suggests that not all collisions are effective; only those that have sufficient energy and correct orientation will lead to product formation.