What term is used for the energy needed to start a chemical reaction?

The term used for the energy needed to initiate a chemical reaction is known as activation energy. This is the minimum energy that must be provided to the reactants for the reaction to occur, allowing them to overcome the energy barrier and convert into products. Activation energy is crucial in understanding reaction kinetics and the rate at which reactions proceed.

During a chemical reaction, reactant molecules must collide with enough energy so that their bonds can break and new bonds can form, resulting in products. Activation energy is the energy required for this initial bond breakage. It signifies the threshold that reactants must surpass for the reaction to proceed.

In relation to the other options, catalytic energy refers to the energy lowered by catalysts but does not represent the energy needed to start a reaction itself. Reaction energy generally refers to the overall energy change associated with a reaction, indicating whether it is exothermic or endothermic. Thermal energy relates to the total kinetic energy of molecules in a substance but does not specifically denote the energy needed to initiate a reaction. Thus, activation energy is the precise term that defines the energy barrier that must be overcome for chemical reactions to take place.