Which of the following reactions would be classified as exothermic?

The classification of a reaction as exothermic is based on the release of heat during the process. In the case of burning wood in a fireplace, combustion occurs, which involves the reaction of wood with oxygen to produce heat, light, carbon dioxide, and water. This release of energy in the form of heat is a hallmark of exothermic reactions.

When burning wood, the chemical bonds in the wood and oxygen are broken and new bonds are formed in the products, but more energy is released in this process than is required to break the bonds of the reactants. The result is a net release of heat energy, which is felt as warmth and can even create flames.

Other reactions mentioned—such as absorbing heat, melting ice, and boiling water—do not release energy into the environment. Melting ice and boiling water are endothermic processes, where energy is absorbed to change the state of the substance rather than being released.