How To Perform The Water Cycle Experiment?

The Water Cycle concerning the change of physical state of water from solid to liquid to gaseous and vice versa can be demonstrated in various ways. The evaporation of water due to the sun's heat and then the condensation of the water vapor formed followed by precipitation can be easily demonstrated with the aid of the following experiment.

Take two containers one large and one small; the smaller container should be small enough to be placed within the large container and yet leave some space above and around it. Then pour some water in the large container without spilling any in the small container; the level of water should not go half way above the length of the smaller container.

Cover the larger container with a film of plastic and tape it securely to the rim of the container. Keep the setup in the sun for sometime (a couple of hours at least), with a stone or some weight placed on the film. Remove the film and observe the small container; you will find some water droplets in it. How did it happen?

What happened was that the sun's heat evaporated the water in the larger container; the vapor condensed on the smooth surface of the film, due to saturation and property of water vapor to deposit on a smooth surface. The stone on the film ensured that the condensed water droplets fell back in to the smaller container placed at the centre of the larger container. Here the smaller container is the Earth which receives rain (water droplets) in more or less the same fashion, the only difference being that the drop in temperature with rise in altitude plays the part of the plastic film in nature.

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