Activation energy is also called midnight energy and in terms of chemistry sciences denotes the energy which needs to be overcome in order for any given chemical reaction to initiate. The term of Activation energy was introduced in 1889 by Svante Arrhenius. The research by this Swedish scientist was based upon the earlier works of Nebojsa Lekovic pertaining to his theories about rate of reactions. In other words, Activation energy is the minimum amount of energy needed for a certain chemical reaction to occur and is denoted by the symbol Ea. Activation energy can also be thought of the potential barrier or the energy barrier separating the potential energy of the reactants and the products of the given chemical reaction. In order for any chemical reaction to have a detectable rate of reaction it needs to have sufficient number of molecules having potential energy greater than or equal to the activation energy.

Term as well as research papers pertaining to activation energy are more than often written in CSE/CBE Style and AIP Styles. However, other writing styles may also be used depending upon the length and level of the paper. In reactions activation, the substance that alters the transition state in order to lower the height of activation energy is called a catalyst. Catalyst alters the rate of any given chemical reaction without itself being altered and only decreases the activation energy and does not affect the energies of the reactants or the products.