Desalination Lesson for Kids

Instructor: Patrick Zedrow

Patrick has taught intermediate science, language arts, and technology. He has a master's degree in educational technology.

Since the Earth is nicknamed the 'Blue Planet,' you would think we have enough water to last us forever. However, almost all of the water on Earth is undrinkable salt water. This lesson focuses on the process of turning that sea water into fresh, usable water.

Sea Water Versus Fresh Water

A cool glass of water can be very refreshing. Even though it may seem like there is an endless supply of water coming out of your faucet, it is important to remember that only 2.5% of the water in the world is fresh water! Many people on Earth struggle to get a reliable supply of water, even if they live right next to an ocean. So, if there is such a huge amount of ocean water on Earth, why can't we just drink it? Well, if you took a gulp of salt water, you would probably get sick because of the bad taste. Besides that, you would get even thirstier because your body cannot handle that much salt.


What if we could turn the salt water into fresh water? You may be surprised to hear, but many places are already doing it with a process called desalination. This process involves separating and removing high amounts of salt from fresh water. There are places around the globe that perform this job, and they are called desalination plants. This newer technology just might be the future for our drinking water!

Desalination is the process of removing salt from water.
Desalination is removing salt from water.

How Desalination Works

There are a few ways that engineers can separate salt from water. One way is called distillation. Distillation is the process of heating up water so forcefully that it changes into a gas, and it leaves any little solid particles behind, including salt. Once the water cools down, it turns back into a liquid, but now it is pure and fresh. When you heat up a pot of water on the stove, it takes about 10 minutes to boil. Can you imagine how much heat is needed to heat up, say, one million gallons of salt water?

Distillation involves boiling water in order to separate it from the salt.

Another way to desalinate water is called reverse osmosis. In reverse osmosis, salt water is forcefully pushed through a wall-like barrier that has many tiny holes in it. These holes allow the water to pass through, but they do not allow the tiny salt particles in the water to pass through. It acts like a very powerful filter, separating the salt and water.

Osmosis is pushing salt water through a barrier that salt particles cannot squeeze through.

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