Question

wax candle burns with a yellow flame well as the domestic gas burns with a blue flame why

Answer 1

The flame of natural gas (mostly methane) burns blue because it contains more hydrogen atoms than carbon atoms which makes the fuel burn cleaner. A candle flame does have some blue flame visible, but most of the color is orange or yellow. During combustion, the hydrogen is being turned to water vapor (in the blue flame) and carbon is being turned to carbon dioxide in the yellow flame. If a cold metal object was held in the yellow flame, the object would be covered in black soot. This is the carbon that is burning in the yellow flame.