which is much heavier, a liter of hot water or a liter of cold water?

Answer 1

Cold by a small amount.

Hot water is less dense than cold, so the same volume will have less mass.

Answer 2

When water is heated it expends. (expension is a natural process)
as a result of expansion there is more volume per atoms .
Therefore at higher temperature there is less atoms per unit volume. Less atoms means less weight for the same volume.
So even if heat has injected some mass in the atom its so small that its neglible.

So conclusion is that one liter of hot water weights less than one liter of very cold water.

Answer 3

Water reaches its maximum density at about 4 deg C, so a litre of water close to 4 deg C would weigh more than a litre of water at, say, 80 deg C ~ but it's not MUCH heavier: a litre at 4C weighs 1000g and at 80C 972g ~ about 3% less.

Answer 4

Mass doesn't change, mass is a property of matter. Unless you change the matter by heating up the water, the mass stays the same. That's like saying if somebody has a fever or suffering from hypothermia, his/her mass changes.

Some of you are confusing mass with weight.

Tha molecular mass of water is about 18.02 grams per mole, no matter what the temperature. MASS DOES NOT CHANGE. The density changes. Some of you are saying "colder water is lighter than hot water" which is just ridiculous, it is less dense, it doesn't have less mass. Density is a measurement of mass per unit volume. Ice doesn't float because its lighter, it floats because it is less dense. If you have a cup of water and measure the mass, freeze it and measure the mass, they're the same. However the ice is less dense because it expanded, therefore it has less mass PER VOLUME.

Answer 5

I think that is the cold, because the colder the temperature is, the more atoms are in the substance.
I also learned that at 4 celsius degree the density of water is 1g/ml , it is the maximum value

Answer 6

your question is not so specific. if cold water is near the freezing point, (becoming ice), cold water is lighter. (picture geysers in the Atlantic, they float on water which, is at a higher temperature). however, if your cold water decreases in temperature, and you expect its mass/weight to become lighter with respect to a fixed volume, you have to stop at 4 degrees Celsius since at this point, water becomes denser and hence becomes heavier with respect to volume. lower temperatures past this value will again result to a decreasing density (mass/volume), since water will expand, until its coldest (ice at 0 degrees Celsius), so that we can observe ice floating on water.

Answer 7

of course cold water because its density is greater than hot water.
for most materials(including water above 4C) density decrease by increasing temperature.
we have:
mass = volume * Density
the greater density, the greater mass.

Answer 8

depends on the definition of "much". generally, the difference would be within a few grammes, e.g. 996g and 999g. the hotter water will always be lighter.

Answer 9

water is different other than other liquids.
when it is cold it would weigh higher

Answer 10

a liter's a liter. they'll weigh the same... assuming you used containers that weigh exactly the same.