Question

Why do we get dew on the surface of a cold soft drink bottle kept in open air?

Answer 1

we get dew on the surface of a cold soft drink bottle kept in  air because when that the temperature of surrounding air is higher than the temperature of the cold soft drink. Air contains water in the form of vapour. When the molecules of water in air, during their motion, strike the surface of the bottle which is cool. They lose their kinectic energy which lowers their temperature and they get converted into droplets.   

Answer 2

because of condensation of water vapours ..