Desalination

Research Questions:

• What occurs during the water cycle?
• How is the water cycle used in the desalination process?
• How is salt water turned into fresh water?

Water is a very important natural resource. Earth is covered with water but around 97% of that water is the salt water of the ocean. This means that most of the water on Earth cannot be used for drinking and other important things that require fresh water. Thankfully there is a process called desalination which removes salt from water providing fresh water. Desalination plants are scattered across the world and are vital in reducing water shortages. 

Materials:

• Plastic wrap
• Rubber band
• Spoon
• Bowl
• Small plastic container
• Salt
• Straw
• Clay
• Water

Experimental Procedure:

1. Pour 2 spoonfuls of salt into the water and stir. Use a straw to taste the salt water mixture. (Note: You should never taste anything from an experiment unless you are told to do so.)
2. Flatten a small piece of clay in the bottom of the bowl. 
3. Pour salt water into the bowl until it is about 1 inch deep.
4. Place the small container on top of the clay in the bowl of salt water so the small container will not move. (Note: The small container should be taller than the depth of the water. There should be no water in the small container.)
5. Stretch plastic wrap over the top of the bowl so that the plastic wrap hangs down slightly into the bowl yet doesn’t touch the water. Place a rubber band around the plastic wrap and the bowl to hold the wrap in place.
6. Place a small clay ball on top of the plastic wrap so it’s hanging over the small container inside the bowl.
7. Place the container in a sunny location for a day.
8. Make a prediction of what you think will happen.
9. The next day, look closely at the bowl, the plastic wrap, and the small container. Write down your observations.
10. There should now be water in the small container. How did that water get there? Using a clean straw, taste the water in the small container. Does it taste salty or fresh? 
11. How did this happen? It was the water cycle at work! Water evaporated from the mixture leaving the salt behind and condensing on the plastic wrap. The fresh water then fell into the small container as precipitation. 
12. Draw an illustration of your water cycle labeling where the salt and the fresh water went. 

Terms/Concepts: Desalination; Water cycle; Evaporation; Condensation; Precipitation

References:

 http://ga.water.usgs.gov/edu/drinkseawater.html