to evaporate acetone we need to have a fan & we generate heat how can we generate heat using only hands??

Answer 1

Hold the evaporating dish in the palm of your hand. Body heat is more than enough. Do not hold it near your face and place the fan so that it blows away from you (you do not want to breathe in the fumes).

If your hands are cold, warm them back up by holding them under a stream of warm water. Dry them completely before holding the evaporating dish. Do not touch the inside of the dish with your fingers.

Answer 2

There are over 500 degrees of heat above absolute zero at room temperature. Acetone will evaporate at a very low temperature, even if it has frozen by way of sublimation. You don't need air motion and you don't need to apply heat to evaporate acetone. Heat and air motion only help it to evaporate faster.