The Collision is the last, but most important piece of material on how substances will combine. It is the theory of reaction rates that states the effectice collisions betwen reactant molecules must occur in order for the reaction to occur. Basically, thsi means partiles have to collide at the proper angle with the proper amount of energy for a reaction to come. CONGRATULATIONS! You have completed ECQ! I hope that you have learned something new, and that at least some of the veil over chemistry was lifted. Want so test what you know? Click here.