Question

What makes the candle flame yellow and luminous?

 

Answer 1

A candle burns with a yellow, luminous flame due to the incomplete combustion of wax in the air. When we light a candle, we observe the wax melt and rise up to the wick in the form of vapours. As there is no proper way for the oxygen to mix with these wax vapours, the latter burns with insufficient oxygen, thereby resulting into the incomplete combustion of wax. This incomplete combustion produces small unburnt carbon particles that rise in the flame, get heated up and make the flame yellow and luminous.