Aglass of cold milk sometimes forms a coat of water on the outside of the glass (often referred to as ‘sweat'). how does most of the water get there?

It is from condensation from the air where the glass of cold milk is. 

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts