Grades 3–5 · Everyday Life
Why does a candle need a wick?
A candle has a large store of wax and a thin wick. The wax is its main fuel. In a burning candle, heat from the flame melts some wax near the wick, forming a small pool of liquid.
In the diagramThe wick brings liquid wax toward the flameSolid wax melts; wax vapor reacts with oxygen3 · Vapor burns2 · Liquid rises1 · Wax meltsOxygen from airHeat returnsProducts leave:CO₂ + water vaporThe wax is fuel; the wick is its liquid supply route.
The wick contains narrow spaces between its fibers. Liquid wax moves into and along those spaces by capillary action. This is the same general kind of movement that lets liquid spread through a paper towel. The wick brings liquid fuel close to the hot region of the flame.
There, the wax becomes vapor. Wax vapor reacts with oxygen from the surrounding air. This burning reaction releases energy as heat and light and produces gases including carbon dioxide and water vapor.
Some heat returns to the candle and melts more wax. Melting, movement through the wick, vaporization and burning keep working together. The visible flame depends on a continuing supply of fuel vapor and oxygen.
About this explanation
Starting knowledge: Distinguish solids, liquids and gases; know that burning needs fuel and oxygen.
Sources
- CandleScience — Where Does the Wax Go When a Candle Burns?
- National Candle Association — Expert Tips: A Calm, Steady Flame