In terms of chemical reactions, what is meant by 'activation energy'?

Activation energy refers to the minimum amount of energy that must be input into a system for a chemical reaction to occur. This energy is necessary to break the bonds in the reactants and initiate the reaction, allowing the reactants to transform into products. Essentially, activation energy acts as a barrier to reaction progress; it needs to be overcome for the reactants to convert into products.

Understanding this concept is critical in chemistry, particularly in catalysis and reaction kinetics. For instance, increasing the temperature of a reaction can increase the kinetic energy of the molecules involved, helping them collide with enough energy to surpass the activation energy threshold. This leads to an increased rate of reaction.

In contrast, the other answer choices focus on different aspects of chemical reactions rather than the initiation process influenced by activation energy. The energy released during a reaction pertains to the exothermic processes, the energy of the products refers to the potential energy in the resulting compounds, and the energy stored in reactants relates to their bond energies, but none directly address the concept of the energy required to initiate or start a reaction.