Why does ice expand when frozen?

A few years ago in 7th grade science, I learn that when water is frozen the particles of matter move in close to each other, they go from being spread out, to being tightly bound. If this is true, then ice should be smaller than it was when it was water. So why does it expand

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  • 1 decade ago
    Favorite Answer

    The crystal structure of ice is not very dense. Water molecules

    are held in a wireframe-like structure with a lot of empty space.

    hence less density. Why are they held in that structure? Because

    of "hydrogen bonds" and +- attractions that have to line

    up the right way.

    There are, however, other crystal forms of ice, arising at

    different temperatures & pressures than humans usually encounter.

    Some of those other forms are denser then liquid water.

  • 1 decade ago

    This is due to something usually referred to as the anomalous expansion of water. Between 0-4deg celsius, water expands. This is why ice floats on water and why livin organisms still reside in frozen lakes or other water bodies.

    Source(s): High school physics
  • 1 decade ago

    i believe it expands because it actually forms a crystalline matrix, as opposed to the fluid nature of the molecules in water.

    the molecules are bound, but they themselves do not change size. perhaps it has something to do with the actual molecular bonding that occurs.

    something to think about next time you have a drink "on the rocks"!

  • eri
    Lv 7
    1 decade ago

    You learned wrong, at least in the case of water. Water freezes in a hexagonal pattern, which is actually LESS dense than it in liquid form.

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  • Anonymous
    1 decade ago

    i always thought that air gets caught in the water which makes it expand

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