About 97% of Earth's water is salty. Why not convert the ocean's salty water to
pure salt-free water? Ocean water can and is being desalinated. There are many
ways to desalinate water. However, turning ocean water into fresh water can be
expensive. The cost can be up to ten times more than the cost of normally
Purifying Salt Water
Here are some methods used to convert salt water to fresh water!
When you boil salt water, the water turns to steam. The salt is left behind. The
steam is cooled back into relatively pure water. The system works well, but is very
Salt water is frozen and then melted. During the process, the salt can be removed
from the water.
Salt dissolved in water normally breaks into two electrical parts called IONS. The
salt ions are attracted electrically to special plastic sheets. The salt particles
(ions) pass through microscopic holes in the plastic sheets. Water molecules are
too big to pass through and stay behind.
Some algae (a water plant) and some bacteria have the ability to absorb salt.
Algae and bacteria can dramatically reduce the amount of salt in sea water.
Build Your Own Salt Water Solar Still
Obtain a CLEAN wide mouth gallon jar with a lid.
Fill a small glass or paper cup with a mixture of salt and water.
Place the lid upside down in full sunlight.
Place the small glass with salt water in the center of the large lid.
Place the jar carefully on the lid as shown. It does not need to be screwed on.
Wait at least a half hour.
Describe what you see forming on the inside surface of the jar.
The sun's heat causes the water, but not the salt, to evaporate. Is the water on
the inside surface of the jar fresh or salty? Leave your solar still out a few hours.
With a little luck you might end up with a little fresh water in the jar lid. Taste a
tiny bit of the lid water. Is it salty?
Reprinted with the permission from Ed Schevick Science Action Labs