Why might the products have more energy than the reactants?

• A. Because bonds are weaker and less stable
• B. Because energy is absorbed during product formation
• C. Because mass increases
• D. Because bonds are stronger, more stable, and release more energy

Answer: (D)

The key idea is how energy changes when bonds are broken and formed. If the products end up with more energy than the reactants, energy must enter the system from the surroundings during the reaction. That is an endothermic process. It can happen when the products are in a higher‑energy arrangement or form bonds that don’t release as much energy as was required to reach that state, so overall more energy remains in the products.

In contrast, forming stronger, more stable bonds typically releases energy, making the products lower in energy than the reactants. That’s why that option describes a scenario where products would have less energy, not more. Mass doesn’t drive this energy difference—the change comes from bond energies and whether energy is absorbed or released during the reaction.