Make Fresh Water with the Help of the Sun!
Topics: Fifth Grade, Science
Fresh water is vital to our survival. The body needs it every day to stay healthy. What would you do if you were surrounded by salt water without fresh water to drink? How do we make salt water safe to consume? It’s easier than you think. This activity will teach your 5th grader how to distill (to purify a liquid by heat and condensation) salt water so that it is safe to drink and more importantly, it will build upon his developing 5th grade science skills.
What You Need:
- Large bowl
- Short glass or cup
- Tape
- Plastic Wrap
- Small rock
- Picture of water
- Salt
- Long spoon for stirring
What You Do:
- First make salt water by adding some salt to your water. Stir until the salt dissolves.
- Pour about 2 inches of water into your bowl.
- Take your empty glass and put it into the center of the bowl. The top of the glass should be shorter than the bowl but higher than the salt water.
- Put plastic wrap over the bowl. You may need to use tape to get the plastic wrap to seal tight.
- Place your rock over the center of your glass so that it weighs down the plastic wrap a little bit, directly over the center of the glass in the bowl. Now you have made what is called a still.
- Place your solar still in the sun for a few hours or all day long. Check on it throughout the day. Note how the water is condensing on the plastic wrap and dripping into the glass. The heat from the sun is evaporating the water up into the air in the bowl. The water then condenses on the plastic wrap, collecting and pooling where the rock is weighing the wrap down. When the water turns into vapor it leaves the salt behind. The result is pure water and this is what is collected in the glass.
- When you want to test your water, take the plastic wrap off and taste your water in the glass. It’s no longer salty! This process of salt distilling is called desalination.
Did You Know?
The biggest desalination plant in the world is in the Middle East, where fresh water is very hard to find. The United States also has plants but they operate on a much smaller scale because the process is expensive. A by-product (what’s left over) of desalination is table salt.
Comments from readers
In (Step 1) one you are adding salt water to the (Step 2) bowl of FRESH water, to make "salt-water". This is the purpose of learning this survival skill, because salt-water is not drinkable, or potable. It must be filtered first, by the mechanism of evaporation and condensation. This project will remove the salt and leave you with fresh drinking water in the glass.
This really does work, and well. My son was 6 when we tried it, and he was pleased with how it tasted. (That says a LOT!)
It does work best with a sunny day as the heat from the sun is necessary to heat the water up just enough to convert it from a liquid to a gas. The evaporating water is then trapped on the saran wrap which forms the "lid", and becomes condensation. As the droplets accumulate, they grow heavier and roll towards the center of the saran wrap on the underside(inside), and then just drop into the shorter glass you have set up in the middle of the bowl, which is shorter than the bowl sides. (A shot-glass in a small Tuperware-like bowl worked great for us!)
Good luck with it-it's fun!
Janet
Webelos Cub Scout leader
Water that you propose from the sun is with a pH of around 4.5 this is acidic it is possible to elevated with minerals, do not drink too much from this, it is excellent for cleaning windows.
Al