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Flames are produced by the reactions between oxygen (the COMBUSTIVE AGENT) and many substances that can react quickly with it, producing gases during the reaction (CO, CO2 and partially burned molecules) and a lot of energy in the form of HEAT (like in all the EXOTHERMIC reactions) that excites the external electrons (e-) of these gases with production of intense light.

This light is just the energy that the excited e- give back returning to their fundamental state, immediately after the excitation. Every e- continuously absorbs and releases this energy during the combustion reaction, giving continuity to the flame light.
So, a flame is simply a mix of very hot gases (2400-3100C).

Only the substances that create gaseous compounds in the combustion with O2 can give a flame, like many organic substances, NH3, H2, phosphorus (P) and so on.

Normally, in the flame of a burner, there are 3 zones:
- a central zone, relatively cold, nearly without combustion
- an intermediate zone, very bright and reducing because the reaction is not complete, containing mainly CO.
In this zone, many metallic oxides can be reduced to metals.
- an external zone, not bright, but oxidizing, where the combustion is complete.

Learn more about this author, Aldo Bonincontro.
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