This qualitatively explains how chemical reactions occur and why reaction rates differ for different reactions. A basic principal is that, in order to react, molecules must collide.

collision theory this is the vocab on usatestprep.

Collision theory

Explanation:

The collision theory is the model used to explain chemical kinetics, that is, how chemical reactions occur.

The theory postulates that in order for a reaction to occur, reactants must collide and interact with one another. The rate of collision/interaction between the reactants is directly proportional to the rate of chemical reaction.

Although not all collision between reactants lead to products. Those that lead to the formation of product are referred to as effective collision. Effective collision among reactants is dependent on;

Size of reactant particles Orientation of reactant particles Activation energy of reactants