Wednesday, February 25, 2015

The Water Cycle: Evaporation

Playing in puddles and during rain showers is a favorite activity for Jelly Bean and Jumping Bean on warm spring afternoons.  But, when I told them that water is in the air all the time, and not just during rain showers, they were surprised.  This is a pretty abstract idea for little ones, so we conducted an easy science experiment exploring the idea of water in the air and evaporation.

First, two cups were filled with water.  Jelly Bean and Jumping Bean then played with the water noting that it felt cold.

I placed one of the cups into the microwave for two minutes to heat the water.  The girls wanted to see if it was "super" hot, so they held their hands over the cup feeling the heat and touched the side of the cup to see how hot is was.

A clear, plastic cup was then placed over each of the cups.

Immediately, the clear, plastic cup above the heated water fogged over.

Why did one cup fog over and the other not?  The cup with hot water in the bottom started to evaporate faster than the cold water.  The water vapor started to rise up, but was trapped by the plastic cup allowing it to become more visible.  Just like in the real world, the sun heats up water in lakes, ponds, and rivers.  The water evaporates and water vapor rises up to the clouds eventually producing rain.


  • 2 cups
  • 2 clear, plastic cups
  • water
  • microwave

  1. Fill the 2 cups with about 2 inches of water.
  2. Place 1 cup into the microwave and heat for 2 minutes.
  3. Place a clear, plastic cup over each of the cups filled with water.
  4. Watch the water vapor form in the cup with hot water.

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