Why Incomplete Combustion Makes Flames Yellow or Orange

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Detailed Solution

Incomplete combustion occurs when there isn’t enough oxygen available for the fuel to burn completely. As a result, the reaction produces carbon monoxide (CO) and tiny carbon soot particles instead of pure carbon dioxide (CO₂).

These unburned carbon particles heat up and glow, emitting yellow or orange light — giving the flame its characteristic color. This is commonly seen in candle flames, kerosene lamps, or low-oxygen burners.

Chemical explanation:

Incomplete combustion: Hydrocarbon + Limited O₂ → CO + C (soot) + H₂O
The glowing carbon particles emit yellow/orange light (blackbody radiation).

Therefore, a yellow flame indicates inefficient burning, energy loss, and more soot — whereas a blue flame indicates efficient, complete combustion.

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