14. It can still float because there is still enough weight the balloon can handle.
15. The balloon will fall down because the helium is getting cool.
16. Less air is in the tank when you inhale, more air fills the tank when your exhale.
17. Mercury has less mass than water.
18. Evaporation is when the hot water turns in to steam and goes up. Boiling is when water is at boiling point.
19. Look for kinetic theory in your books, there is many answers for that question.
Hope this helps!
