Which statement best defines combustion?

• A. A chemical process that does not require oxygen
• B. A chemical process in which the combination of a substance with oxygen produces heat and light
• C. A physical change without energy release
• D. A process that only produces water

Answer: (B)

Combustion is a chemical reaction in which a fuel reacts with oxygen, producing heat and often light. The key features are the involvement of oxygen and the release of energy, which you see as warmth and flames in a fire. This distinguishes it from processes that don’t need oxygen or from physical changes that don’t release energy. While complete combustion tends to yield carbon dioxide and water, the defining idea is the fuel-oxygen reaction that releases heat and light, making the described statement the best definition.