Modeling the Water Cycle

You'll find many variations of this activity, some more sophisticated than others, throughout the Internet and in numerous books.  This one is very basic - it's simple to set up and can be effective in helping students visualize the processes occurring throughout the water cycle.

You'll need a glass jar with a metal lid.

Fill the jar with about an inch of hot tap water (the hotter it is, the faster you'll see something happening). 

Flip the lid upside down and set it on top of the jar.

Fill the lid with ice cubes.

Wait, watch and observe.

The hot water will evaporate.  As it rises, it will cool.  The cooled vapor will condense into drops, which will accumulate on the underside of the lid and eventually drop.