What is meant by activation energy?

Activation energy refers to the minimum amount of energy that must be provided for reactants to undergo a chemical reaction. This energy is necessary to overcome the energy barrier that prevents reactants from converting into products. When this threshold is reached, the reaction can proceed, often involving the formation of an activated complex or transition state.

This understanding is fundamental because it explains why some reactions occur spontaneously at room temperature while others require additional heat or catalysts. The choice that defines activation energy correctly focuses on the requirement to initiate a chemical reaction, emphasizing that it is not merely about breaking bonds or the energy changes during the reaction itself. This clarifies the role of activation energy as a crucial starting point for reactions, making the chosen answer accurate in capturing the essence of the concept.