Final answer:
In a chemical reaction, chemical bonds are both broken and formed, which involves the rearrangement of atoms and the transfer of energy. The amount of energy involved is dependent on the specific chemical bonds affected in the reaction.
Step-by-step explanation:
During a chemical reaction, molecular bonds are indeed broken and others are formed to create different molecules. This process is fundamental to any chemical reaction and involves rearrangement of atoms. Energy plays a crucial role in this process; breaking a bond requires an input of energy, while forming a new bond releases energy. The amount of energy involved depends on the specific bonds.
For instance, when two water molecules react to form hydrogen and oxygen (2H₂O → 2H₂ + O₂), the oxygen-hydrogen bonds in the water molecules are broken and new bonds are formed between hydrogen atoms and between oxygen atoms. Similarly, in the combustion of methane (CH₄ + 2O₂ → CO₂ + 2H₂O), bonds break within the methane and oxygen molecules, and new bonds form in the carbon dioxide and water that are the products of the reaction.
The bond energy, also known as the bond enthalpy, is the amount of energy needed to break a bond. It is measured in Joules (J) or Kilojoules per mole (kJ/mol). The enthalpy change of a chemical reaction can be estimated by considering the energies required to break the bonds in the reactants and the energies released upon forming bonds in the products.