What causes the anomalous expansion of water?

[Karan Punjabi]

Guys, I was studying thermal expansion and i saw an unusual example of expansion in water when i asked my teacher what's the reason behind it, he says its advanced chemistry. Can someone explain this unusual behavior of water?

 

[DaveC426913]

No. Not without further details.

 

[russ_watters]

Are you referring to the fact that water expands when it cools below 4C and freezes? It's from the crystal structure the molecules arrange themselves into when they freeze:
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/waterdens.html