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# Why does ice float on water ? watch

1. Why is ice less dense than water ?
2. (Original post by Butterfly)
Why is ice less dense than water ?
As water cools it vibrates less so more hydrogen bonds can be formed. These will push the molecules into a open lattice stucture which is less dense
3. Thanks
4. Why does water expand when frozen? I thought it loses energy, therefore less movement and so it's more compact.

These will push the molecules into a open lattice stucture which is less dense

-=X=-
5. ummm i thought i said that.. but maybe not clear. the H bonds will push the molecules apart
6. Ok. I quoted it because I thought that bit might apply to my question as well as the one about density. Thanks

-=X=-
7. (Original post by daydream)
ummm i thought i said that.. but maybe not clear. the H bonds will push the molecules apart
yeah your right, after as water cools down, more hydrogen bonds are formed, and this forms an lattice, in which the water molecules are further apart than in a liquid. hence, ice is less dense than water, since density is the amount per size.
8. As water turns to ice, the water molecules arent in liquid state anymore so they dont slide over each other anymore and vibrate a lot less. The molecules themselves rearrange themselves into a tetrahedral open lattice structure, rather like diamond. To do this, the molecules need to push themselves apart to form more hydrogen bonds. There are less hydrogen bonds in liquid water because the molecules are constantly moving.
9. try my best.....

As we know that ice is a solid, and the molecules are in fixed positions, and are unable to move freely, they form a maximum of 2 hydrogen bonds between molecules ( just try to draw out ice,.. i won't go into that) and the h bonds hold the molecules together. As a result the volume of solid water ( ice) increases because of the maximum formation of 2 bonds for a fixed mass of water. As density is mass per volume, volume is inversely proportional to density and ice has a lower density than water because it occupies a bigger volume. Understand?
10. Yes, thank you.

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