The chemical reaction that changes materials and produces heat, flames, and toxic smoke is known as which?

• A. Endothermic
• B. Exothermic
• C. Pyrolysis
• D. Chemical free radicals

Answer: (B)

Exothermic reactions are defined by releasing energy as heat to the surroundings. That energy release is what fuels flames and can lead to the production of smoke as materials burn and break down into further products. In the context of a fire, the burning of fuel is an exothermic process, driving heat, light, and the creation of combustion byproducts, including toxic smoke. Endothermic reactions absorb heat, so they wouldn’t produce flames. Pyrolysis describes thermal decomposition that creates volatile gases, but the key feature described—heat and flames from the reaction itself—points to energy release, i.e., exothermic.