What is the minimum amount of energy required for a reaction to take place called?

The minimum amount of energy required for a reaction to take place is referred to as activation energy. This energy barrier must be overcome for reactants to transform into products during a chemical reaction. It is crucial for initiating the process because it helps to break bonds in the reactants, allowing for rearrangement and the formation of new bonds in the products.

Activation energy is an essential concept in understanding reaction kinetics; it influences the rate of reaction and is a determining factor in whether a reaction will proceed or not under certain conditions. The higher the activation energy, the less likely the reaction is to occur at a given temperature, as fewer molecules will possess sufficient energy to overcome that barrier.

The other terms presented in the choices refer to different concepts: "threshold energy" is not a standard term in chemistry; "free energy" relates to the spontaneity of a reaction; and "heat of reaction" indicates the overall energy change but does not specifically address the energy needed to initiate the reaction.