Answer: Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.
Step-by-step explanation:
Activation energy can be represented as the difference between the energy of reactants and the energy of the activated complex.
A catalyst is a substance which increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and convert to products.