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Q & A: The Weight of Frozen Water

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Q:
If I have a countainer of water that is 1lb and I freeze it will it still be 1lb or will it be more.
- Louis Arambula (age 12)
Denver co. usa
A:
Louis -

Let's think about it. You probably know that if you take something (anything) and cut it up into almost the smallest parts you can, you get what's called molecules. Everything in the world is made up of these little tiny molecules, and each molecule weighs a certain amount. In a liquid (like water), the molecules are sort of stuck together, but they can slosh around a lot. When you freeze it and turn it into a solid (like ice), you slow all of the little molecules down, and they get stuck together really tightly so they can't move. But all the same atoms are still there...they're just moving more slowly. So the water will still weigh the same amount when it's frozen, since it still has all of the same molecules that it started off with.

-Tamara

(republished on 07/25/06)

Follow-Up #1: water density

Q:
When warm water mixes in the ocean with cold water, the warm water rises and the cold water sinks. This is because it is denser than the cold water, correct? If that is true the total volume (or amount of space) that the water takes up, when cold, has been reduced. Therefore, wouldn't a gallon of 92 degree water take up less space than a 32 degree portion of water even though it has the same number of molecules?
- Russell Geary (age 31)
Atlanta, GA. USA
A:
I got a little lost in trying to follow which way you were thinking the density change went. Hot water is less dense than cold water. The same number of molecules take up more room when they're hot. Just near the freezing point the pattern reverses, so the densest water is at about 4 C, around 39 F.
Mike W.

(published on 08/02/08)

Follow-up on this answer.