Water on the outside of the glass might mystify your preschooler.

How to Explain the Process of Condensation to Children

by Kathryn Rateliff Barr

Your little one might point out with a puzzled expression, “Mommy, there's water on the outside of my glass -- and the glass left water on the table. How did it get there? I didn’t spill it.” Condensation is likely a word she doesn’t know, but she can see the results with two simple experiments you can do at home with some common household items and a little preparation. Your little Einstein can help you perform the experiments to make the results more memorable.

Cold Condensation

Place one empty glass in the freezer and leave it for 15 minutes. Place three glasses each 6 inches apart, on the table or counter.

Take the glass out of the freezer and set it on the counter 6 inches away from the other glasses. Pour cold water in the second glass and add 1 drop of food coloring to the water. Add room temperature water to the third glass and leave the remaining glass empty.

Watch the glasses on the counter. The condensation on the freezer glass should form first in the form of ice crystals. Your little one can see that there was no water inside the glass, so there is no way the water was spilled from the glass. Condensation will also form on the outside of the glass of cold water, but the condensed water will be clear, unlike the colored water in the glass. The remaining glasses will not have any condensation.

Explain that invisible water in the air forms on the outside of the glasses that were in the freezer or filled with cold water because the glass became cold. The glasses that stayed at the same temperature as the room didn’t cause condensation, even if the glass contained water.

Evaporation and Condensation

Line a cardboard box with newspaper and spray paint it black. Alternatively, line it with a large black garbage bag or black construction paper. If your spray-paint the box, allow it to dry. Place the box in an area where it gets direct sunlight.

Pour water into a clear glass until the glass is one-quarter full. Cover it with plastic wrap -- and tape it in place. Place the glass in the center the box and allow it to sit for one to two hours.

Examine the glass. Your child will notice that water drops formed on the bottom of the plastic wrap. Explain that the water evaporates from the bottom of the glass, but can’t rise any further than the plastic wrap covering, so it condenses on the underside of the plastic wrap. If she taps the plastic wrap, the water will rain down inside the glass, just like it rains from water condensed in the clouds. Talk about how water evaporates from puddles, rivers and oceans all over the world. The water rises into the colder air and condenses to form clouds. When the water gets too heavy, it falls down as rain to start the cycle all over again.

Items you will need

  • Five clear glasses
  • Freezer
  • Water
  • Ruler
  • Food coloring
  • Cardboard box
  • Newspaper (optional)
  • Black paint (optional)
  • Black plastic garbage bag or construction paper (optional)
  • Plastic wrap
  • Tape

About the Author

Rev. Kathryn Rateliff Barr has taught birth, parenting, vaccinations and alternative medicine classes since 1994. She is a pastoral family counselor and has parented birth, step, adopted and foster children. She holds bachelor's degrees in English and history from Centenary College of Louisiana. Studies include midwifery, naturopathy and other alternative therapies.

Photo Credits

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