Whenever we fill a bottle with cold water and place back the cap tightly closing it, why is it that after a few seconds we notice cold water droplets outside the bottle as if the water is coming out of the non porous plastic bottle? Also the same thing happens when the bottle contains hot water, so we can associate this with the thermodynamics' law of equilibrium, but then how and from where does this water form droplets outside the bottle? Because there can't be so much of moisture around in the air which is going to help in the droplet formation.


Actually the water droplets which are formed on the outer surface of water bottle are formed from the atmospheric water vapours

the water vapours which come in contact with the outer surface gets condensed into water droplets

see this article for more reference

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    $\begingroup$ As a point of possible interest: this exact effect is used by charlatans to sell statues of [fill_in_$deity_here] which appear to weep. Fill an internal chamber behind the eyes with cold water and "tears" form on the exterior. $\endgroup$ – Carl Witthoft Jun 30 '14 at 11:47
  • $\begingroup$ that was a great application which you illustrated i will surely try this to prank my friends $\endgroup$ – agha rehan abbas Jun 30 '14 at 12:26

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