Which of the following will change when a catalyst is added to a chemical reaction?

When a catalyst is added to a chemical reaction, the activation energy of the reaction is reduced. This means that less energy is required to start the reaction and the reaction will proceed at a faster rate. A catalyst does not affect the potential energy of the reactants or products, as these are determined by the nature of the reactants and products themselves. The heat of the reaction is also not affected by the presence of a catalyst, as the amount of heat released or absorbed by a reaction depends on the difference in potential energy between the reactants and products, which remains the same with or without a catalyst. Therefore, the correct answer is The activation energy.