Drinking water is becoming more and more scarce the world over as fresh water supplies are evaporated due to global warming and droughts. You can use the following resources to do some research on the current water shortage situation:
One of the things that has intrigued scientists from the time we emerged from the caves, was how to take the plentiful salt water of the seas and oceans and make them palatable for drinking.
Ok, onto the experiment, this is a small scale version of one of the methods scientists are evaluating.
* 1-2 TBS table salt
* 3 cups water (tap water is fine)
* small bowl or coffee cup
* thick plastic wrap
1) pour watere into the larger bowl
2) mix salt into the water until it is dissolved
3) place the small bowl or cup into the water CAREFULLY, you do not want to let any of the water to flow ov the sides of the cup.
4) Place the stone in the center of the plastic wrap, so at the wrap angles down into the cup a bit.
5) carefully place the bowl in the sun
6) wait several hours. You should see water droplets on the inside of the plastic wrap dripping into the cup.
7) after a few hours allow student to taste the water in the cup - it won't be salty!
The water from The bowl evaporated, condensing on the underside of the plastic wrap (which is why heavy duty plastic wrap is so important, lesser quality plastic wrap will allow the water vapor to escape and leave the cup empty.) salt doesn't evaporate, so essentially the evaporation process separates the water molecules from the salt ones.