Dear Patrick,
The answer to your question is that, in general, a given volume of liquid water at room temperature will increase in volume by about 9.05% after freezing. Most materials do the opposite, that is, the solid form of most substances is more dense than their liquid form.
(
Source University of Toronto)
[Above] Before freezing, liquid water molecules are somewhat free to move around. 
(
Source University of Wisconsin--Green Bay)
[Above] When frozen, water molecules form crystal structures. This is the most common form of crystallized H2O, called "Ih". The "h" in Ih is from it's "hexagonal" structure which may or may not be easy to see here. It is less dense than the liquid form of water above since this crystal structure takes up more volume than the free-to-move-around liquid water molecules. (You can ignore the different colors--each ball represents a full water molecule.) Interesting note: I
h is not the only form of crystallized water. If the water is put in a high pressure environment, frozen quickly or put in extremely low temperatures, frozen water will have other crystal structures which are more dense than liquid water. There are about 15 kinds of ice crystal structures, but I
h is the most commonly found crystal structure on Earth.
Hope that helps answer your question!
Sincerely,
John
(published on 03/12/2011)
