Learning Lesson: The Rain Man

OBJECTIVE Demonstrate the concept of precipitation.
OVERVIEW The students will see the hydrologic cycle in action as the water evaporates and condenses to form rain.
TOTAL TIME 30 minutes
SUPPLIES Mayonnaise size jar
Resealable sandwich bag
Ice cubes
SAFETY FOCUS Flash Flood Safety


What goes up, must come down. Precipitation is the most commonly seen aspect of the hydrologic cycle.

  1. Add about two inches (5 cm) of hot water to the mayonnaise 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.

Despite the sometimes excessive rainfall that occurs, only about 0.3% of all water on the earth is found in the atmosphere. And only a small fraction of that is seen as rain. Most of the water in the atmosphere is in the gas state called water vapor. So while the hydrologic cycle is essential for life due to the water it brings, the vast amount of water in the cycle is found in the oceans, lakes, and ground water.

Fast Facts
One inch of rain equals...
5.6 gallons of water per square yard (weighing 46.8 lbs / 21.2 kg)
27,104 gallons of water per acre (weighing 113.2 tons)
66,946 gallons of water per hectare (weighing 279.5 tons)
17.4 million gallons of water per square mile (weighing 72,515 tons)

Live Weatherwise

Flash Flood Safety

  • If a flash flood warning is issued, get to higher ground immediately! Follow evacuation instructions, but don't wait for them if you think you are in danger.
  • Do not drive across flooded roads or bridges-they may be washed out.
  • If your vehicle stalls in water, abandon it and get to higher ground. It takes only a foot or two of rapidly-moving water to sweep away a car.
  • Walking or playing around flood waters is dangerous; you can be knocked from your feet in water only six inches deep!

Back: The Hydrologic Cycle