Which process requires energy input: bond breaking or bond making?

Bond breaking is an endothermic process, meaning it requires an input of energy to separate atoms that are held together by chemical bonds. In order for bonds to break, sufficient energy must be supplied to overcome the attractive forces that hold the atoms together in a molecule. This energy input can come from various sources, such as thermal energy (heat) or electromagnetic energy (like light).

In contrast, bond making is an exothermic process, during which energy is released when new bonds are formed between atoms. This release of energy occurs because the resulting bonds are more stable than the individual atoms alone, allowing the atoms to achieve a lower energy state.

Understanding the distinction between these processes is crucial in the context of chemical reactions, as the overall energy change in a reaction depends on the balance between the energy required to break bonds in the reactants and the energy released when new bonds are formed in the products. This is central to concepts such as reaction enthalpy and Gibbs free energy.