Select the statement that correctly explains the source of the energy change in a chemical reaction.

• A. The energy change results from the physical mixing of reactants.
• B. The energy change arises from the breaking and formation of chemical bonds, which involves changes in potential energy.
• C. The energy change is solely due to the movement of electrons between atoms.
• D. The energy change is caused only by changes in temperature during the reaction.

Answer: (B)

Verified step by step guidance

1. Understand that in a chemical reaction, energy changes occur because chemical bonds are broken and new bonds are formed between atoms.
2. Recognize that breaking chemical bonds requires energy input (endothermic process), while forming new bonds releases energy (exothermic process).
3. Know that the overall energy change of the reaction depends on the difference between the energy required to break bonds and the energy released when new bonds form.
4. Realize that this energy change is related to changes in potential energy stored in the chemical bonds, not just physical mixing or temperature changes alone.
5. Conclude that the correct explanation for the source of energy change in a chemical reaction is the breaking and formation of chemical bonds involving changes in potential energy.