In the combustion CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l), which substance acts as the reducing agent?

Core Concept

Carbon climbs from -4 in methane to +4 in carbon dioxide, so methane loses electrons and is oxidized. Whatever is oxidized reduces its partner, which makes methane the reducing agent. Oxygen simultaneously drops from 0 to -2, confirming that electrons flowed from fuel to oxidizer even though no metal appears anywhere in the equation.