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there are several, repetitive discharges amongst the clouds themselves. 19) Snow fall and Rain
Snow flakes are not circular or spherical in shapes. Normally when water vapour (cloud) condenses, it should first form a net-like thin layer of water sheet, floating in cloud itself. It is broken at several places due to contraction (540 times) in size. This is opposite of evaporation of water in form of vapour. Here molecules of vapour come together and condesne in form of liquid-water. Its molecules vibrate, just as vigorously as that of liquid water at 100°C in oceans.
(During evaporation, the surface water gains so much mechanical energy at 100° C in ocean that they detach from the liquid mass with a jerk and are released in form of gas-water in the air called water vapour. Here, the inter-molecular attraction is overcome by vigorous vibrations of the hotter Molecules. They can no more be held together.)
In condensation, the vibration energy of vapour molecules reduces so much that the inter molecular attraction force becomes more than the vibrating threshold, so that they come together to form a super liquid molecule.
In this condensation, when vapor molecules come together to form a giant liquid molecule, why should it not form a tiny spherical droplet? Normally it does so under the influence of surface tension and forms a droplet. However, in state of super cooling, the sheet of water vapour converts into a 2 dimensional layer of super-cooled liquid. Its molecules are attracted together to form giant molecules of liquid in the layer. They are again attracted together to form snow flakes having air entrapped between them. They form hexagonal or pentagonal shapes, as per the unit structure of water-body. Various shapes of snow flakes are shown in fig. 1 (page 198)
(ii) Vapour Molecule :
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