Question

Why anomalous expansion of water is caused? Why only water shows this unusual property?

Answer 1

Dear student,
It is the density of the water which causes this anomalous expansion of water.Due to decrease in the temperature, the top water layer contracts.It becomes dense and sinc to the bottom. A continous circulation occurs which causes the entire water to reach its maximum density at 4^oC.If the temperature further decreases, the top layer expands and freezes.Thus, the anomalous nature of water occurs in which upper layers are frozen and the water near the bottom is 4^oC.

Now, why only water shows this unusual property is because it form hydrogen bonds when heated at 277K.Generally ice is expected to expand when converting into water, this gradual change of formation of hydrogen bonds causes it to contract.Water has maximum density at 277K.It is because all the hydrogen bonds are formed at 277K. Beyond this temperature, the water follows the kineticf energy of the water molecules.That is an increase in volume when heated and reverse when cooled.

Regards