in thermal expansion, usually an object expands with a high temperature and contracts in a low temp. but why is it that the case of water, it is the opposite?

Question

anonymous · Answer

because density of water is maximum at 4'c....

anonymous · Answer

because at that temperature h-bonding in water is maximum so density  is maximum

anonymous · Answer

H-bonding

anonymous · Answer

Yeh I thought it was at it's max density at 4 degrees c too. So water does expand and contract 'normally' above this temperature. Below 4 degrees c the hydrogen bonds can't slide past each other so easily (it'll form a crystal/latice stucture as it freezes) so it takes up more space i.e. is less dense.

anonymous · Answer

actually if the temperture is high enough then it goes same as other object. but in particular temperture water goes different because of its morecule structure.

anonymous · Answer

Have a look at this page - quite a good and not too long explanation: http://www.chem1.com/acad/sci/aboutwater.html#HBOND