Give reasons for the following observation.
Air holes of a gas burner have to be adjusted when the vessels being heated get blackened by the flame.
The gas stove used in our homes comprises burners with tiny holes in them so as to let in sufficient oxygen required for the fuel to burn. When there is sufficient oxygen, the fuel will burn completely with a blue flame. If the fuel fails to burn completely, a sooty flame will be produced (due to the incomplete combustion) which will blacken the bottom of the vessel. Therefore, the air holes in the gas burner need to be adjusted so that the burner gets enough oxygen to burn the fuel completely