Does hot water weigh less than cold water?

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. read more

We know that hot water has more energy than cold water; We know that E=mc^2; Therefore, hot water, with more energy, must therefore have more mass, so weighs more; However, this is for two containers of water that have the same number of molecules, and therefore the same mass at a constant temperature. read more

Hot water is heavier than cold water. If density is decreasing means its cover area is also increasing, and weight is irrelative to the area body occupies. read more

However if you mean the same volume of water (say one cup) of cold and hot water, then the cold water should weight more than the hot water, since water (like most things) in a liquid state expands when heated. read more

Other way around. Cold water does weigh more than hot water because it is more dense at a colder temperature. The strange thing about this behavior is that once the water freezes and forms ice, the ice is less dense than the water. read more