Question

Give reason when we want to warm a liquid we should warm it from below why

Answer 1

Warm water being lighter than cold water always roses upward when heated and this enshure the uniform heating of water. If we try to heat water from the above, it will not mix uniformly as the hot water will remain at upper position while the cold water will remain at the bottom. Thus it will take a lot of time and energy to boil water from upward.

Answer 2

When we warm a water we find that water near to the burner get heated first.

we also know that warm things always rises up. Hence, this below warm water rises up and makes the cold upper water to move down and get heated.

Thus, to heat the bulk of water we need to heat it from the bottom.