[Physics] Why does cold water weigh more than hot water in a fixed volume

home-experimentweight

Take a bucket of hot water and the other bucket of cold water. Why does the bucket full of cold water weigh more than bucket full of hot water?

Best Answer

Heating almost any material will cause it to expand. That is, its density will go down, as the same mass of material takes up more space. Or, alternately, the same volume of the material weighs less.

If you take your bucket and fill it to the brim with cool water then heat the water (not to boiling), some of it will spill out of the top.

PS: Water is one of a very few materials that does not follow this rule perfectly. Water is actually at its densest (and heaviest for a given size container) at 4C. If you compare a bucket of 4C water to a bucket of 1C water, the warmer bucket will be heavier.

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