Ice expands as it freezes.
We’ve all seen what happens to milk after we put it in the freezer – we’ve seen how milk cartons expand.
The reason for this is simply that as water cools it traps air into its structure. The minimum volume for water is about 4 degrees, and after this it increases in volume as it takes air into it as it cools.
And this of course is why ice floats – the air it contains makes it less dense than water.
350-22cookie-checkWhy Does Ice Expand as it Freezes?
I’m not sure where you learned your chemistry, but covalent bonds are not temperature dependant. If they did in fact get longer as they cooled, then cold water would be less dense than hot water, which of course it isn’t.
And if you don’t believe that ice cubes contain air, I’d suggest you go and have a very close look at one.
This is not correct. No air is drawn into ice as it undergoes phase change. Water molecules are held together by very strong covalent hydrogen bonds. The structure is directionally charged, with one end being positive, and the other negative. These strong , directional bonds increase in magnitude as temperature drops, eventually forcing the molecules into a crystalline structure as the water freezes. This crystalline structure is less dense than liquid water, and therefor displaces a larger volume.