why is there more smoke after the fire goes out than while it’s burning?
In: Chemistry
Surely there is more smoke during a fire than when it has gone out. No?
However, you might be refering to a candle? Because it is true that once the candle is burning, you pretty much see no smoke, and once you kill the fire, there is a clear line of black/grey smoke releasing.
Short answer is a non-complete reaction.
When you have an intensive fire, the fire will yield enough energy for the carbon (originated from the hydrocarbon fuel – Wax in the case of a candle) to combine with the oxygen (O2) in the air.
If you have a complete reaction, the byproduct of a burning candle is CO2 (which is colourless like vapour), while a less complete one has more CO (also colourless and at low densities pretty much invisible to the eye). Also free carbon (soot) will be released during the candle fire. But the ratio of soot to COx is quite low.
Now, when the candle’s fire has been killed, there is only the tiny weak ember on the top of the wick.
This glowing ember doesn’t yield enough energy for a complete reaction – so you have quite a big ratio of pure carbon (soot) released along the COx which you can see as a black smoke.
**TL;DR**
**Dead fires doesn’t have enough energy to completly combust hydrocarbon (fuel) to colourless gases like COx. Just enough energy to release the black-ish nano-particle carbon aka soot.**
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