(Earth Science for ages 5+)
So how do we find enough freshwater on a planet with so much saltwater? Well, there are a few different ways to “purify” water to make it fresh and clean, one of which is called distillation.
In the video above, you can see how distillation occurs with just a bit of heat. Here’s what you’ll need:
Small plastic cup
Plastic cling wrap
Rocks (or other weighted object)
- Start by adding some saltwater to your large bowl. Mix 2 tablespoons of salt per cup of water. There should be about 2 inches of saltwater in your bowl, or enough to allow the cup to float on top of it.
- Set your bowl in a sunny spot, either outside or near a window, where it can stay for several hours undisturbed. Set your plastic cup on top of the water in your bowl like a small boat. Do not let any water get into the cup.
- Using the plastic cling wrap, cover the bowl completely and tape the edges down to keep it secure.
- Finally, add the rocks or other weighted object to the top of the plastic cling wrap so the plastic slopes down toward the cup. Leave your bowl undisturbed for several hours, even up to a day.
- After several hours, check the plastic cup. What happened? Do you see water in the cup? Taste a small bit of the water. Is there salt in it?
When the heat from the sun warms the saltwater, it creates a small amount of water vapor gases under the plastic wrap. The salt is left behind in the bigger pool of saltwater, and the water vapor is made of freshwater.
When the sun is no longer shining directly on the bowl, this water vapor cools and condenses on the inside of the plastic wrap. Because the plastic wrap is sloped down toward the empty plastic cup, the water condensation drips slowly down into the cup, leaving you with freshwater in the cup and saltwater in the bowl.
This whole process is called distillation because the freshwater is distilled and purified from the saltwater.