What occurs during energy changes in a chemical reaction?

During a chemical reaction, energy changes are primarily due to the breaking of existing bonds and the formation of new bonds. When reactants come together to form products, bonds within the reactants must be broken, which requires an input of energy. This energy input allows the atoms to rearrange and form new bonds in the products.

The energy released or absorbed during this process can vary, depending on the relative strengths of the bonds broken and formed. If the energy required to break the bonds in the reactants is less than the energy released when new bonds form, the reaction is exothermic, releasing energy to the surroundings. Conversely, if more energy is required to break the bonds than is released upon the formation of new bonds, the reaction is endothermic, absorbing energy.

This understanding highlights the dynamic nature of energy changes in reactions, which reflects the interplay between bond energies. The idea that energy remains constant or that only energy is released or absorbed serves as oversimplified views of a more complex process that involves both aspects in most reactions.