Which is the best explanation of why heat is released when wood burns?

• A. Burning wood absorbs energy from the surroundings, causing the temperature to increase.
• B. The process of burning wood is endothermic, so heat is given off to maintain equilibrium.
• C. Heat is released because the reaction forms unstable products that quickly break down.
• D. The chemical bonds in the reactants (wood and oxygen) have higher energy than the bonds formed in the products (carbon dioxide and water), so energy is released as heat.

Answer: (D)

Verified step by step guidance

1. Understand that burning wood is a chemical reaction called combustion, where wood (mainly composed of cellulose) reacts with oxygen to form carbon dioxide and water.
2. Recall that chemical reactions involve breaking bonds in reactants and forming new bonds in products, and that energy changes depend on the bond energies involved.
3. Recognize that breaking bonds requires energy input (endothermic step), while forming new bonds releases energy (exothermic step).
4. Compare the total bond energies of reactants and products: if the bonds in the reactants have higher energy than those in the products, the excess energy is released to the surroundings, often as heat.
5. Conclude that heat is released during wood burning because the energy released from forming the stable products (CO\_2 and H\_2O) is greater than the energy needed to break the bonds in the reactants (wood and oxygen).