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Drink Up!
An activity you can use in the classroom

Background
Water covers almost three-quarters of the Earth. Yet most of it is seawater, which has too high a salt content to make it drinkable. By distilling seawater into its original components (salt and water), large desalination plants provide fresh drinking and irrigation water to people on islands and in deserts.

In this activity, you'll create a desalination still and use the water cycle to convert saltwater into freshwater.

What You Need

  • Large, heavy foil baking pan (see Advance Preparation)
  • Small foil baking pan (see Advance Preparation)
  • Block of wood one-inch thick and same length as the shorter end of the larger pan
  • Saltwater (see Advance Preparation)
  • Plastic wrap
  • Beaker with measurement markings
Advance Preparation:
  • Spray black paint on the interior of the large tin.
  • Cut the corners on one short side of the small pan, and then fold in the flap to make that side of the pan shallower by about half an inch.
  • Prepare saltwater: Mix salt and tap water.
What To Do
  1. Set up the pans in direct sunlight: Use the block of wood to tilt the large pan so that it's resting at an angle. Then place the smaller pan so that its shallow side is touching the lower end of the large pan.
  2. Fill the beaker with saltwater, and record the starting volume of saltwater on the attached worksheet.
  3. Pour saltwater into the large pan, filling it so the water level is just below the rim of the pan's low end.
  4. Record how much water is left in the beaker on the worksheet. Then calculate how much water you've poured into the pan.
  5. Place plastic wrap over both pans to finish creating your closed desalination still.
  6. For the next several days, observe the still and describe any changes you see on the worksheet.
  7. When all the saltwater in the large pan has evaporated, measure the amount now in the small pan. Record the amount on the worksheet, and answer the questions.