Nisha observed that the bottoms of cooking utensils were turning black in colour while the flame of her stove is yellow in colour.Her daughter suggested cleaning the air holes of the stove to get a clean, blue flame. She also told her mother that this would prevent the fuel from getting wasted.
What could be the reason for this sooty flame?

Explanation

The sooty flame was produced due to the incomplete combustion of the fuel. This is because the air holes of the stove were blocked which resulted in limited air (or oxygen) supply.