# Hot and cool milk

Usually I have the habit of keeping the hot milk for a while, until it becomes cool. I have noticed many a times that, drinking it, after keeping for a while, gives the mixture of hot (relatively less hot than before) and cool milk.

• Almost $3$ by $4$ (approx) part of the milk at the top, is relatively found to be hot than the last $1$ by $4$ (approx) part of the milk.

What is the reason for upper part to be hot and lower to be cooler?