In general, when a pure substance or mixture goes from liquid to solid, the molecules in it get closer resulting in a higher density.

If this is so why does ice float in water?

solid water i.e. ice is actually less dense than liquid water and that is why it floats. Water is one of the few substances that actually has this property. Water is actually most dense at 4 degrees celsius. Ice is less dense than liquid water because of something called hydrogen bonds that form between water molecules. In ice, a nice structured latice is formed which makes more empty space between molecules. When water is at 4 degrees celsius the molecules are actually packed closer together than at any other temperature making the water most dense at that temperature.

Posted by James on 2003-08-27 15:10:10