Phases of water are constantly changing in the summer: dew on grass in the morning that is gone by lunch, water droplets forming on the outside of a cup, “clouds” appearing in covered dishes left in the sun. We see these things all the time, and kids are always noticing as well. Here are some fun activities, and explanations, for your kids to learn the science behind what they are observing.
Water Evaporation and Condensation: Cloud in a Cup
Have your kids grab two clear plastic containers. Fill them about half way full, and mark the water level. Cover one container with a clear lid, or plastic wrap. Leave the other container open. Place both containers outside in a sunny spot. Leave for a few hours.
Go back and notice what is developing on the inside of the lid. Wait two days and look again. When you go back to observe the containers, the open container will have lost water. The water was heated by the sun, turned into water vapor and evaporated. The container with the lid will also have a lower water level, but there should also be visible water droplets on the lid, or plastic wrap. The air in the covered container can only hold so much water vapor, without a way for the vapor to escape, it condenses back to water and forms droplets. The droplets will fall off the lid and back into the container.
This is a great example of how water from the earth evaporates, cools, forms clouds, condenses, and falls back to earth as rain. Your kids can think of the open container as an ocean, river, or lake. Heat from the sun turns liquid water into its gas phase, water vapor. The water vapor then evaporates and is cools back into liquid water and eventually becomes part of a cloud. The plastic wrap of the covered cup acts like the atmosphere, and traps the water vapor. In a real cloud, the water vapor cools back into liquid water. In the covered cup, the air can only hold so much vapor, and the vapor condenses back to liquid water forming a “rain cloud” on the plastic wrap.
You can change this up by doing some variations. Put a set of covered and uncovered cups out in the sun, and another set in a shady spot. Also, put one set in the refrigerator. See the differences in evaporation, and condensation over time.
Change the Phase of Water With a Cold Drink
All kids have held cups of ice water in the summer and felt, or even played with, the condensation that develops on the outside of the cup. We all do this, but we may not always think of the science that is behind the condensation. Telling your kids that the cool cup is changing the phase of water in the air, making it go from a gas to a liquid will get them thinking about the fun science that is happening right in their hands.
Grab a cup of water, add some ice cubes, and go outside on a warm sunny day. Within a minute or so, there will be drops of liquid water on the outside of the glass or cup. The temperature of the ice water in the cup is cooler than the temperature of the air. The cup cools the surrounding air, and the temperature change causes the water vapor surrounding the cup to turn back into liquid water. Now, make another drink with ice and put it into the refrigerator. Did the same thing happen?
This is a fun experiment, because let’s face it, we all love drawing things in water condensation. Grab a bunch of cups, add water and ice and have fun creating art with the beauty of science!