In combustion, which component acts as the oxidizer?

• A. Fuel
• B. Heat
• C. Oxygen
• D. Nitrogen

Answer: (C)

In combustion, the substance that enables the fuel to burn by accepting oxygen is the oxidizer. In most practical fires, the oxidizer is oxygen from the air. The air we breathe is about 21% oxygen, which reacts with the fuel molecules when the mixture is hot enough, releasing heat and forming combustion products like carbon dioxide and water. Without oxygen, the fuel cannot sustain combustion, even if heat is present.

The other options aren’t the oxidizer because fuel is what burns, providing the energy; heat is the energy needed to start and drive the reaction; nitrogen in air is mostly an inert filler that doesn’t drive the burning process (though very high temperatures can lead to some nitrogen-related byproducts, it doesn’t act as the oxidizer).