Final answer:
Forming a chemical bond typically releases energy and breaking a bond requires energy. The concept of bond energy is central to understanding these processes. The energy change during a reaction indicates if it's exothermic or endothermic.
Step-by-step explanation:
Forming a chemical bond typically releases energy, while breaking a bond requires energy. This release or absorption of energy is heavily dependent on the type of bond and the specific reactants involved in a chemical reaction. Energy changes during chemical reactions are indicative of whether a reaction is exothermic (releases energy) or endothermic (absorbs energy).
The energy associated with chemical bonds is referred to as bond energy. It is the amount of energy needed to break a bond between two atoms. Conversely, when bonds form, they release energy because the resulting molecule is more stable.
This release of energy as a result of bond formation is a key principle in understanding the energetics of reactions. For example, when hydrogen gas (H₂) forms, each covalent bond's formation releases 436 kJ/mol, which is the same amount of energy required to break it.
The Law of Conservation of Energy applies to chemical bonds, meaning that the energy cannot be created nor destroyed but can change form. During a chemical reaction, some bonds are broken and new ones are formed. The overall energy release or absorption depends on the balance between the bond energies of the bonds broken and the bonds formed, thus determining whether a chemical reaction is exothermic or endothermic.