Answer / amruthasesh

It is because the freezer when kept at top cools the circulated air in contact with it thus making it denser than the air below. Thus cooled air comes down and the hotter air being less dense moves up. Imagine if the freezer is at the bottom..circulation will not be possible as cold air being dense will continue to remain at the bottom and hot air being light will continue to be at the top. This is nothing but natural convection phenomena.

Answer / harish saini

Due to convection current

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