Ice to Water & CO2 to Liquid: Volume Change Explained

[thereddevils]

When ice changes to water , its volume decreases but when solid carbon dioxide changes to liquid carbon dioxide ,its volume increases . Why is it so ? Both changes from solid state to liquid state but one with its volume increasing and the other one decreasing.

 

[Stonebridge]

Water is a special case. Its unusual behaviour is a result of the hydrogen bonding that occurs. In simple terms, the realignment of the bonds as the water cools below about 4 degrees takes up more space, this causes the water to expand.
http://chemistry.about.com/od/chemistryfaqs/f/icefloats.htm
http://www.chem1.com/acad/sci/aboutwater.html
http://en.wikipedia.org/wiki/Hydrogen_bond#Hydrogen_bonds_in_water

 

[Mindscrape]

Yeah, it's actually pretty cool because if water didn't behave in the way it did then we wouldn't have ice on top of cold lakes. But because liquid water is more dense than solid water we see ice float at the top, sweet!