Water plays a very important role in the atmospheric circulation. The water vapor, which evaporated from the ocean and land goes around the globe with the atmospheric circulation and finally becomes rain drops in the clouds. The large amount of energy which is released in the condensation process, is one of the main driving forces of the atmospheric circulation

 
Problem:

• What is rain and where does it come from?

Materials:

• Electric tea kettle containing 1 or 2 glasses of water.
• Small saucepan, filled with a little cold water.
• Ice cubes for cooling water in pan.

Procedure:

• Bring water in tea kettle to boiling point so steam is rising from spout.
• Put ice cubes and water in pan.
• When steam is rising from kettle, hold pan of water over spout so steam from spout will strike bottom and sides of pan.

Result:

The steam from the kettle, upon striking the cold pan, is cooled and condenses to form droplets of water on the outside of the pan. These droplets collect and fall from the pan like rain falling from a cloud.

This demonstration can be used effectively by the pupils in the classroom to further their understanding of how rain is formed.

The visible part of what we call steam is actually small droplets of liquid water. Water vapor (gas) is invisible.

Discussion Questions:

• What is rain?
• How is rain made?
• How are puddles formed?
• Why do puddles disappear?
• What are clouds made of?
• How does rain help us?
• Is rain ever harmful to us?
• What would happen if it stopped raining?

 
Vocabulary:

• Condensation
• Precipitation
• Evaporation