Chemistry Regents Practice Test

Which term describes the energy required to initiate a chemical reaction?

1. Enthalpy

2. Activation energy

3. Kinetic energy

4. Potential energy

The correct answer is: Activation energy

Activation energy refers to the minimum energy that must be provided to initiate a chemical reaction. This energy is necessary to overcome the energy barrier for the reactants to convert into products. It enables the reactants to reach the transition state, which is the point of highest energy where bonds are broken and formed during the reaction. For context, enthalpy is a measure of the total heat content of a system and is not specifically about the energy necessary to start a reaction. Kinetic energy is the energy of motion, which is relevant during the reaction but does not encompass the concept of the energy input required to trigger the reaction itself. Potential energy describes the stored energy in a substance due to its position or arrangement, but it does not specifically relate to the initiation of reactions. Thus, activation energy is the precise term that directly relates to the energy input needed to commence a chemical reaction.