(3) Physically, water behaves as most liquids in contracting as it gets colder, but this is only true to 4 degrees C(aprox. ) Water is nearly unique in that as it starts to freeze, the molecules line up into a spiral structure that is less dense and so larger for the amount of water in it. Water expands as it freezes,Ice is both larger and less dense than the equivalent amount of liquid water. So as it freezes, the ice formed rises to the top, and seals in the remaining liquid, and if the freezing goes on long enough,the water that has solidified and expanded as it did begins to push hard on the glass,and eventually will fracture it. This is also how water breaks rocks up in areas of thawing and freezing.