Creating Water in the Desert

Overview: This is such a neat little experiment, it's fun and informative for all ages. Based on the process of condensation, it appears to create water from nothing (which is, of course, not the case).
Teacher Preparation: Aquarium, sand, clear plastic, small container like a jar lid, plant, water.
Procedure Ideas:

1. Put 5-10 cm of sand in aquarium.
2. Hollow out a 10-15 cm depression in the sand.
3. Place jar lid in the center of the hole, and plant material (small whole plants or broken up larger ones) around the container on the sand.
4. Lay 20x20 cm clear plastic over the hole, and hold in place with sand or pebbles around the edges.
5. Put just enough sand or a pebble in the very center of the plastic to make it sag slightly. Too much weight will pull the plastic loose around the edges.
6. To speed up the process, place a light bulb over the aquarium to warm the sand and plastic, as the sun might.
7. Water from the plants will form on the underside of the plastic by evaporation (from the plants and residual moisture in the sand) and condensation. If the plastic sags enough, the moisture will run to the center of the plastic and drip into the container in the bottom of the hole.