I eat everything and never get full. I drink everything and always feel dry. What am I?

This intriguing riddle points to a fundamental chemical process that has captivated and served humanity for millennia. When something burns, it undergoes combustion, a rapid chemical reaction with an oxidizer, typically oxygen, that consumes a substance known as fuel. This "eating" process breaks down materials like wood, gas, or even fabric, transforming them into new compounds such as ash, carbon dioxide, and water vapor, while releasing significant heat and light. Because this reaction requires a continuous supply of fuel to sustain itself, it metaphorically "never gets full," always ready to consume more.

The second part of the riddle, about "drinking everything and always feeling dry," refers to how this process is extinguished. When water is applied, it doesn't quench a thirst in the way a living creature drinks. Instead, water effectively puts out the reaction primarily by absorbing a tremendous amount of heat, cooling the burning material below its ignition temperature. As water turns into steam, it also helps to smother the process by displacing the oxygen it needs to continue. The intense heat generated by this chemical reaction also creates an environment that feels inherently dry, as moisture is rapidly evaporated, further contributing to the paradox of consuming liquid yet remaining parched.

This powerful and self-sustaining reaction, essential for countless aspects of human civilization from cooking food to generating electricity, is a constant transformer of matter. Understanding its basic components—fuel, oxygen, and heat—is key to both harnessing its power and controlling its destructive potential.