A beer koozie is designed to keep a beer cold. The koozie is effective at blocking heat transfer from your warm hand into the cold beer and it also prevents condensation from forming on the side of the beer. Why does preventing condensation on a beer bottle keep the beer cool on a hot humid day?

Water-vapour molecules give of their heat to convert into liquid water which is absorbed by the surface on which they condense.

Explanation:

Preventing condensation on the surface of a cold beer container will prevent the heat gain by the beer by absorbing the energy from the surrounding molecules of the water vapour present in the air in the form of humidity.When water vapour of the atmosphere which is present in the form of humidity condenses on the cold surface it releases the latent heat of vapourization to the cold surface of the container which is directly in contact with the beer which further absorbs the heat form the container.We know that the latent heat of vapourization of water is . This amount of heat is very high and can lead to gain of temperature considerably.