Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: martin on 09/09/2009 11:30:03

Title: Why does water expand when frozen?
Post by: martin on 09/09/2009 11:30:03

martin asked the Naked Scientists:
   
Why does water expand yet other things contract when frozen?

What do you think?

Title: Why does water expand when frozen?
Post by: Cooljeffct2 on 09/09/2009 20:57:55

Water expands when it freezes due to molecular geometry and the fact that it is a very polar molecule. The water molecule is shaped like an upside-down "v". Due to this shape, when water freezes it make a hexagonal shape such that the slightly negatively charge oxygen atoms are aligned with the slightly positively charge hydrogen atoms -- this is the most stable configuration. (Less polar molecules do not configure themselves in this way because there is less of a reduction in energy if the molecule is not as polar) This orientation leaves space in the middle of the frozen water molecules. That is why water expands when it freezes. 

http://wiki.answers.com/Q/Why_does_water_expand_when_it_freezes