When u put water in an erlenmeyer flask, and put a balloon over the top of it, and boil the water...?

Question

the balloon will inflate.... why ?

Answer 1

When the water boils, what happens? The water turns into what?
What does hot air do? Does it raise or fall?
If a balloon is filled with air what does it do?

Answer 2

Ok, when water boils, it turns into water vapor. Water Vapor is less dense than air, so it rises. And because it's in a gaseous state, it's actually expanded because of the absence of Hydrogen bonds. So the balloon inflates. It does not violate the law of conservation of mass in any way if you were questioning that.