Earth science – unit 6: earth's water
experiment: water purification
imagine being stranded in the desert without any clean water. how would you survive without becoming dehydrated? as long as you have a piece of plastic, some rocks, and a cup, you can purify dirty water using the water cycle. the purification process uses the "greenhouse effect" to cause evaporation and condensation. the setup used to purify the water is called a solar still. in this experiment, you will purify water using a solar still.
objectives
explain how evaporation and condensation can be used to purify water.
materials
1 cup of dirt
4 cups of water
small glass
large glass bowl
clear plastic wrap
small, round rock
sunshine
directions
pour the water into the bowl. mix in the dirt.
place the small glass in the center of the bowl. the lip of the glass should stand taller than the dirt and water mixture, but shorter than the sides of the bowl.
find a sunny spot outside. place the bowl in direct sunlight.
place the plastic wrap over the bowl. put the rock in the center of the plastic wrap, directly over the cup. gently push down on the rock until the sides of the plastic wrap slope at about a 45° angle. secure the loose sides of the plastic wrap to the outside of the bowl.
leave the bowl in the sun for three or four hours.
remove the plastic wrap. look in the cup and in the bowl. record your observations.
respond to the questions below.
questions
answer the questions in the essay box below.
is the water in the cup dirty? why or why not?
what happened to the water in the bowl?
this project simulates a real world process. what does the plastic wrap represent? what does the water in the cup represent?
which two parts of the water cycle are at work?