Chemical reaction rates are influenced by a variety of factors, including temperature and the presence of catalysts. For example, an increase in temperature will increase reaction rates. According to collision theory, the reaction rate is equal to the frequency of successful collisions. What is mainly required for a successful collision of reactants (molecules entering a reaction) is a minimal quantity of energy (activation energy) as well as a specific spatial orientation of the reacting molecules. In other words, collisions not satisfying these prerequisite do not lead to a reaction. Collision theory explains why an increase in temperature accelerates a reaction: the kinetic energy of molecules rises with temperature. However, another theory is needed to explain the phenomenon of activation energy: transition state theory.

Transition state theory does not define colliding molecules as compact objects; in fact, the term "collision," although current in chemical vocabulary...