Why is there an unusual behaviour of water? Its maximum density is at 4 degree Celsius.
Water doesn't always expand unlike other liquids and contract when it is cooled.
This is from the topic "Expansion of Liquids"

Question

Why is there an unusual behaviour of water? Its maximum density is at 4 degree Celsius.
Water doesn't always expand unlike other liquids and contract when it is cooled.
This is from the topic "Expansion of Liquids"

irishboy123 · Answer

a lot of water's unusual behaviour/properties are based in its polarity and hydrogen bonding

so the usual explanation is that, as energy is taken from water, its molecules can settle into regular hexagonal patterns.  if it is re-heated, the kinetic energy of the H2O molecules disrupts this so whilst there is still that liquid stickiness between molecules, it is less well defined and the molecules are more compacted.

anonymous · Answer

https://www.youtube.com/watch?v=UukRgqzk-KE

arindameducationusc · Answer

Nice video @bozhena