Learning Lesson: The Rain Man

Overview

What goes up, must come down. As water vapor rises from the surface, it cools and eventually turns back into liquid water or solid ice. This is precipitation, the most commonly seen aspect of the hydrologic cycle. The students will watch a demonstration the concept of precipitation.

Procedure

1. Add about two inches (5 cm) of hot water to the jar.
2. Add the ice cubes to the sandwich bag and seal it.
3. Place the sandwich bag over the mouth of the jar, allowing one end of the bag to form a tip inside of the jar. This will allow the condensed water to collect at one location.
4. After a few minutes, the water (rain) will begin to drip from the sandwich bag, returning to the water.

Discussion

Water vapor will rise from the hot water and come into contact with the bag filled with ice. The ice will cause the water vapor to cool and condense, forming drops which will drip back into the water.

Despite the sometimes-excessive rainfall that occurs, only about 0.3% of all water on the Earth is found in the atmosphere. Of that 0.3%, most of the water in the atmosphere is in the form of a gas (water vapor).

Therefore, while the hydrologic cycle is essential for life due to the water it brings, the vast amount of water in the cycle is still found in the oceans, lakes, and ground water.