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Duh- a bad question i know

  1. Feb 4, 2007 #1
    duh- a bad question i know....

    Ok i was in chemistry the other day and we were talking about combustion of alkanes in both complete and non complete reactions... i know that combustion is the oxidation of something... but what exactly IS the flame made when something burns? what is it made of?
     
  2. jcsd
  3. Feb 5, 2007 #2

    chemisttree

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    Usually the yellow flame is composed of superheated carbon soot. Blue flames are superheated plasma of the reaction products, usually nitrogen and carbon dioxide if it is burning in air. Air is 80% nitrogen which doesn't usually enter into the reaction process but can react with oxygen just outside the blue zone of the flame to produce some brownish oxides of nitrogen we see as smog.

    The complete flame starts at the surface of the substance to be combusted. Heat decomposes the stuff into a gas(s) which may combine with oxygen to produce a variety of oxygenates or may thermally decompose to carbon-rich soot. The flame that you see is the brief, fleeting existence of this decomposition just before it combines with oxygen to complely combust.

    Want to trap some of that carbon soot? Just place a piece of metal briefly into the yellow part of the flame. Voila! You have trapped the soot on the cool surface which should now appear black.
     
  4. Feb 6, 2007 #3
    ok thank you... i wasnt quite sure. I know how bad a question it was sorry :P
     
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