What is activation energy? How is it related to the collision theory?

Collisions are necessary for a reaction to happen, according to the theory behind collision theory. Particles need to collide with enough energy to equal or exceed the activation energy; if the activation energy is not reached, a reaction won't happen.

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is the energy needed to break the bonds in the reactant molecules so that they can rearrange and form products. Activation energy is related to the collision theory as it explains that for a reaction to proceed, reactant molecules must collide with sufficient energy and proper orientation. Only collisions with energy equal to or greater than the activation energy result in successful reactions, leading to the formation of products. In essence, activation energy determines the likelihood of a reaction occurring and influences the reaction rate according to the collision theory.