Science, Tech, Math › Science What Happens to Candle Wax When a Candle Burns The process involves an intricate chemical reaction Share Flipboard Email Print When you burn a candle, the wax is oxidized. an aruni photography / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 28, 2019 When you burn a candle, you end up with less wax after burning than you started with. This is because the wax oxidizes, or burns, in the flame to yield water and carbon dioxide, which dissipate in the air around the candle in a reaction that also yields light and heat. Candle Wax Combustion Candle wax, also called paraffin, is composed of chains of connected carbon atoms surrounded by hydrogen atoms. These hydrocarbon molecules can burn completely. When you light a candle, wax near the wick melts into a liquid. The heat of the flame vaporizes the wax molecules and they react with the oxygen in the air. As wax is consumed, capillary action draws more liquid wax along the wick. As long as the wax doesn't melt away from the flame, the flame will consume it completely and leave no ash or wax residue. Both light and heat are radiated in all directions from a candle flame. About one-quarter of the energy from combustion is emitted as heat. The heat maintains the reaction, vaporizing wax so that it can burn, melting it to maintain the supply of fuel. The reaction ends when there is either no more fuel (wax) or when there isn't enough heat to melt the wax. Equation for Wax Combustion The exact equation for wax combustion depends on the specific type of wax that is used, but all equations follow the same general form. Heat initiates the reaction between a hydrocarbon and oxygen to produce carbon dioxide, water, and energy (heat and light). For a paraffin candle, the balanced chemical equation is: C25H52 + 38 O2 → 25 CO2 + 26 H2O It's interesting to note that even though water is released, the air often feels dry when a candle or fire is burning. This is because the increase in temperature allows air to hold more water vapor. You're Unlikely to Inhale Wax When a candle is burning steadily with a teardrop-shaped flame, combustion is extremely efficient. All that is released into the air is carbon dioxide and water. When you first light a candle or if the candle is burning under unstable conditions, you may see the flame flicker. A flickering flame may cause the heat required for combustion to fluctuate. If you see a wisp of smoke, that's soot (carbon) from incomplete combustion. Vaporized wax does exist right around the flame but doesn't travel very far or last very long once the candle is extinguished. One interesting project to try is to extinguish a candle and relight it from a distance with another flame. If you hold a lit candle, match or lighter close to a freshly extinguished candle, you can watch the flame travel along the wax vapor trail to relight the candle.