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Published on Sep 10, 2012
This is an elementary science video that explains Convection of Heat for Grade 7-8 kids.
CONVECTION OF HEAT Take a round-bottomed flask. Put some crystals of Potassium Permanganate in it. Pour water into the flask gently so as not to disturb the crystals much. Heat the flask gently. Water molecules go up from the level of Potassium Permanganate reach the surface of the water and come down touching the sides of the flask. After a few minutes the crystals of Potassium Permanganate dissolve in water making it coloured violet. The water at the bottom gets heated and expands. The density of water becomes less because of this expansion, therefore water becomes light and goes up to the top. At the top the cool water which has more density comes down by the sides of the flask. You can observe that the colored water going up in the middle and coming down along the sides of the flask. Molecules absorb heat go up and the cool molecules come down absorb heat and go up. In this way heat gets transferred from one place to another. This process is called convection of heat. The difference in the densities of different parts of the substance is responsible for the phenomenon of convection of heat.