Final answer:
Chemical reactions involve the breaking of bonds in reactants and the forming of new bonds to create products, resulting in energy changes due to the alteration of stored energy in chemical bonds.
Step-by-step explanation:
During a chemical reaction, the chemical bonds in the reactants are broken and new bonds are formed to create the products. This process involves a reorganization of atoms, which results in the formation of different chemical compounds. For example, when methane (CH4) burns with oxygen (O2), the chemical bonds within the methane and oxygen molecules break and new bonds form to create carbon dioxide (CO2) and water (H2O). Similarly, the formation of water from hydrogen and oxygen can be represented as 2H + O → H₂O, illustrating the breakdown and construction of bonds in the process.
Chemical bonds are the forces that hold together atoms in a molecule and involve the sharing of electrons. When these bonds are broken or formed, there is a change in potential energy, since chemical bonds possess "stored energy". Consequently, chemical reactions often involve energy changes such as absorption or release of energy, depending on the nature of the bonds being altered.