What is fire or flame made of

"Flame or fire is an exothermic reaction front or wave in gaseous medium produced as a result of an exothermic chemical reaction"

 

Fire or flame is the result of rapid chemical reaction with the emission of heat, light and other products. Combustion or burning is the result of this chemical reaction. It involves a number of reactions between the fuel and the oxidant and the visible manifestation of this process is called flame.

The components required for fire are:  an oxidisable material i.e fuel, oxygen i.e air, a minimum temperature i.e heat and inorder to sustain combustion – a chain reaction.

Even though charcoal burns in air, it requires  a minimum temperature of about 500 degree C, to start the combustion process. Here charcoal is the fuel and once lit, it burns as long as charcoal and oxygen are available. Combustion is the most common flame producing reaction process. However all substances cannot undergo the process of 'burning'. For example if mercury is heated in air, instead of burning it combines with oxygen in the atmosphere to form mercuric oxide. Therefore all fuels get oxidized by burning, but not all oxidation processes necessary involves burning.

Iron burning in oxygen does not produce any flame but substances such as phosphorous, sulphur etc produces a flame because the substances are volatized during the process combustion. Depending the material undergoing combustion and the temperature, the flame colour may vary. In short, flame or fire is an exothermic reaction front or wave in gaseous medium.

References


[1] https://en.wikipedia.org/wiki/Combustion

[2] http://www.thehindu.com/todays-paper/tp-features/tp-sci-tech-and-agri/fire-flame/article2202510.ece