I don't understand how energy is released in combustion. We have a reaction of a combustible material with oxygen and this releases energy. In what form is this energy released? It should be some waves or a medium in which the energy is released! And I suppose that released energy causes the products of the combustion to have extremely high kinetic energy (ie. temperature), right? Anyway, can you answer me please.
Notice, the combustion is an exothermic chemical reaction with the oxygen that liberates the energy mainly in the form of heat, comparatively less amount of light, sound etc. Reactant molecules react with the oxygen that results in breaking of old bonds & formation of new bonds with comparatively less bonding energy. Thus, releasing the rest amount of energy in form of heat during combustion.
In the combustion process, the heat energy comes from the chemical energy stored in the combustible material being burnt.