Disappearing Water

To see for yourself what happens when water evaporates! For this project, you will need only a glass beaker and a sunny window, but you will learn why evaporation is an important part of the water cycle.

What You Need:

  • Clear glass beaker (150 ml or 250 ml will work well)*
  • Water
  • Window with lots of sunlight coming through
  • Wax pencil or masking tape and markers

*You could also use a tall glass if you don’t have a beaker.

What You Do:

  1. Fill the beaker with water up to the 150 ml mark. If you like, you can use the wax pencil to draw a line at the water level, and write ‘start.’
  2. Set the beaker in a spot that gets a lot of sunlight through a window. Try to set it as close to the window as you can, using the windowsill if possible.
  3. Leave the water there for the whole day. Check on the water level every hour, and mark with the wax pencil (or use tape) where the level is at, and how many hours it has been.
  4. If you like, you can keep the beaker of water in the sun for several more days to see what happens.

What Happened:

The water in the beaker seems to disappear the longer you leave it in the sun. This is not a magic trick. It’s science! As the sun heated up the water in the cup, some of the water evaporated into a gas called water vapor. You can’t see water vapor, but you can tell that the water has changed from a liquid to a gas because there is less liquid in the cup. Right before it rains there is water vapor inside clouds. When the weather is right the water vapor will come together and form raindrops. When the water vapor starts forming tiny drops of water we call it condensation. When condensation falls to earth as rain we call it precipitation. Sometimes the droplets freeze before they get to the ground and become hail, sleet, or snow!