Thursday, March 24, 2016

Build a Solar Water Purifier

Salty water such as seawater is usually considered not drinkable.  The process of removing salt and other non-volatile impurities from salt water is called distillation. A solar water purifier uses the greenhouse effect to trap energy from the sun.  The mechanism of solar water purifier also demonstrates the water cycle that naturally occurs on earth: evaporation, condensation and precipitation.
Materials you will need:
  • A big bowl
  • A plastic cup which is 1’’ shorter than sides of the bowl
  • Clear plastic wrap
  • Tape or rubber band large enough to go around the bowl
  • Small rock or weight
  • Salty water
Step-by-step instruction:
  1. Put salty water in the bowl.
  2. Place the plastic cup (with no water inside) in the center of the bowl.
  3. Cover the bowl with plastic wrap and use either tape or rubber band to secure the plastic wrap.  Make sure the plastics warp is tight.
  4. Put the small rock or weight in the center of the plastic wrap.  The extra weight in the center will ensure that the evaporated water will drop into the cup.
  5. Place the bowl under the sun and observe how distilled water start to accumulate inside the plastic cup for every hour or so.
  6. When there is enough water in the plastic up, open the plastic wrap and taste your purified water.
  7. Can you tell whether the water taste differently from tap water?  If so, can you explain why?

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