Why do chemical changes often involve energy release or absorption?

Chemical changes often involve energy release or absorption due to the breaking and forming of chemical bonds.

Chemical changes, also known as chemical reactions, involve the rearrangement of atoms in molecules. This process requires the breaking of existing chemical bonds in the reactants and the formation of new bonds in the products. The breaking of bonds requires energy, known as endothermic reactions, while the formation of bonds releases energy, known as exothermic reactions.

In an endothermic reaction, the energy needed to break the bonds in the reactants is greater than the energy released when new bonds are formed in the products. This results in an overall absorption of energy, usually in the form of heat, from the surroundings. A common example of an endothermic reaction is photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen.

On the other hand, in an exothermic reaction, the energy released when new bonds are formed in the products is greater than the energy needed to break the bonds in the reactants. This results in an overall release of energy, again usually in the form of heat, into the surroundings. Combustion reactions, such as the burning of wood or the explosion of dynamite, are typical examples of exothermic reactions.

In both types of reactions, the energy changes are due to the differences in the energy required to break and form chemical bonds. This is a fundamental aspect of chemical reactions and is governed by the laws of thermodynamics. Understanding these energy changes is crucial in predicting the outcomes of chemical reactions and in harnessing these reactions for practical applications, such as in the design of energy-efficient chemical processes and the development of new energy sources.