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Why are candle flames classified as diffusion flames?
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Learn about the chemistry of lighting a match.
Candle flames are classified as diffusion flames because their fuel and oxidant are not mixed prior to entering the burning zone. In a candle, the wick draws up molten wax, which then vaporizes. This fuel vapor must meet and mix with atmospheric oxygen through the process of molecular diffusion to sustain the flame.14
Because the ingredients are not premixed, the structure of the flame relies on this diffusion process to distribute the combustible material and oxygen. This stands in contrast to premixed flames, where the fuel and oxidant are combined before combustion occurs.12