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Usually maximum time we see then after cooking by gas there is no black spot on the pot. But continually burning can affect the pot surface and makes black powder.

My question is:

What is the most acceptable reason that black powder(carbon) take places on the pot surface. Is it related to the burning temperature? or fuel reacts with the pot surface?

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  • $\begingroup$ Please clarify your question with an example. Is the pot empty? $\endgroup$ – bobthechemist Jul 24 '13 at 8:54
  • $\begingroup$ Will the answer differ for empty and filled pot? how? $\endgroup$ – Chem_boy Jul 24 '13 at 18:44
  • $\begingroup$ Your question is not clear - are you burning something that is in the pot, or are you concerned with the flame from the stove forming soot on the bottom of the pot? $\endgroup$ – bobthechemist Jul 24 '13 at 18:48
  • $\begingroup$ I'm concerning with that, how black spot is on the pot. What reaction behind this. $\endgroup$ – Chem_boy Jul 24 '13 at 18:52
  • $\begingroup$ See this question $\endgroup$ – bobthechemist Jul 24 '13 at 19:12
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For combustion to occur you need 3 things at the same place: fuel, oxygen and heat.

If the air intake is dirty or not big enough, you get a flame that has an orange color, and on a cooler surface deposits C before it has a chance to burn.

The reaction with the pot is only a physical one of heat transfer and maybe C deposition.

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  • $\begingroup$ Can you write some carbon depositions reactions which incorporated with the pot? $\endgroup$ – Chem_boy Jul 24 '13 at 18:45
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    $\begingroup$ Temperature is not a thing in the sense that it is a substance like fuel or oxygen; it is a measure of thermal energy. It is more syntactically correct to say fuel, oxygen and heat. $\endgroup$ – bobthechemist Jul 24 '13 at 19:16
  • $\begingroup$ One possibility for propane: $\ce{C3H8 + 4O2⟶ 4H2O + 2CO2 + C}$ but there are different mixes for the gas used for cooking. @bobthechemist: you're right. $\endgroup$ – f p Jul 24 '13 at 19:19

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