Carbon, and its compounds burn in presence of oxygen or air to give CO2, heat and light.
The process of burning of carbon or carbon compound in excess of oxygen to give heat and light is called the combustion reaction. In the reactions carbon is in its maximum oxidation state of 4+ in the product.
Generally, saturated hydrocarbons burn with a clear light blue flame, whereas unsaturated hydrocarbons burn with yellow flame with soot (carbon). If air is not sufficiently available during combustion, even saturated hydrocarbons give sooty flame. When Coal, Petroleum etc., burn in air, they give oxides of sulphur and nitrogen in addition to CO2 and H2O which pollute the environment. When Coal or Charcoal is burnt sometimes they just glow red without flame. This is because to get a flame gaseous fuels should burn.
Most of the aromatic compounds burn with sooty flame.
- Why do sometimes cooking vessels get blackened on a gas or kerosene stove?
Because of the inlets of air getting closed, the fuel gases donot completely undergo combustion. Hence, it forms a sooty carbon form which gets coated over the vessels.
A combustion reaction is generally defined as any reaction that sustains a flame. It usually involves burning with oxygen, though some exceptions are there, combustion reaction is always exothermic, that is energy is liberated during combustion reaction.