ijk (04/08/83)
I am really amazed at the standard answers posted to this problem. Of course Archimedes' Principle applies, but what about the other effects? Water is densest just above freezing ( I forget exactly where, but it's only a degree or two, if I remember correctly). Since the energy of the phase change is fairly substantial, the water is probably going to get colder (all of which depends on the relative volumes) by a fair amount, and thus a bit denser. Denser water takes up less room (sure it's a small amount, but that's the correct answer). Incidentally, that is why bodies of water take so long to freeze - the water loses heat at the top, it then sinks - so effectively the entire body must cool to just above freezing. Have a nice day Ihor Kinal hou5e!ijk A former physics major, if not practitioner.