Evaporation Demonstration

• Once you have explained that water usually first makes its appearance on earth as precipitation in the form of rain or snow, demonstrate how the water disappears into the air again to explain one of the basic steps in the water cycle. Fill two cups equally full of water and mark the level with black marker. Seal one cup with plastic wrap and leave the other open. Place both cups near a window and check the cups on a daily basis, marking any changes in the water level. Preschoolers will be amazed as the water in the open cup disappears into thin air.
  
  

Ice Cold Condensation

• Water turns from a gas to a liquid when warm air filled with water vapor hits something cold, so demonstrate condensation with a simple science activity using only a glass of ice water. Fill a glass with ice water and let it sit for a few minutes. Watch as tiny droplets of water bead on the outside of the glass as the warm water vapor-filled air meets the cold glass to form condensation. Explain to students that clouds are actually formed by condensation as water in its gaseous form rises from the earth and cools.
  
  

Steamy Science

• Demonstrate evaporation and condensation hand-in-hand with a teakettle and piece of cardboard or book. Place an 8 1/2-by-11-inch sheet of cardboard in the freezer while you boil a kettle of water on the stove. Invite preschoolers to observe the steam rising out of the kettle created by the water getting hotter and turning from a liquid to a gas, evaporating into the air as they watch. Wear oven mitts to hold the frozen cardboard 1 foot above the spout in the steam to see how the hot, evaporating water turns back to a liquid through condensation when it hits the cold surface.
  
  

Cotton Ball Clouds

• Preschoolers will grasp the concepts of evaporation and condensation when they can hold a cloud in the palm of their hand. Pass a cotton ball cloud to each preschooler and spread a few shallow pans filled with 1/2 inch of cold water among small groups of preschoolers. Ask preschoolers to describe how their cloud feels when it is dry, as if the cloud had just rained or snowed. Have preschoolers warm up the water-filled pan lake by blowing warm air onto the water to make it "evaporate" back into the air. Dip the cotton balls into the water as you explain that the air is cooler way up high in the sky, so the water turns back into a liquid during condensation to form a cloud. If you are explaining the entire water cycle, you can now invite students to squeeze the water back out of their cloud into the lake to simulate precipitation.