Osmosis Lesson for Kids

Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

Have you ever heard the word 'osmosis' and wondered that that is? This lesson will teach you exactly what osmosis is, explain how it works, and give an example of osmosis in your own body!

Learning About Osmosis

Imagine you, your family, and all of your friends are crammed into an elevator. What if all these people began dancing? With so much movement, you might want to get out, but the elevator door is shut, keeping everyone in.

What if it opens? Some people might be pushed out the door into the lobby. After that, more people would probably want to be dancing outside the elevator in the larger lobby space.

Osmosis is when there are a lot of thing taking up a small space and then some of those things move to a less-crowded space through a barrier. When it comes to osmosis, a barrier is something that traps some of things but not others. We'll explain more about this later.

Back to our elevator. We would say that the elevator has a high concentration of people. In this case, concentration is a word we use to describe the amount of something (like people) contained in something else (like an elevator). Our crowded elevator had a high concentration of dancers; the big lobby had a low concentration of dancers.

Barriers and Molecules

Back to osmosis. Osmosis needs a separation, or barrier, with high concentration of something on one side and a low concentration on the other. There are lots of barriers in your body. One example of a barrier is the lining of your lungs. The barrier of your lungs lets some things in and out but not everything. You want air to move freely in and out of your lungs but not other things, like blood.

Instead of people, osmosis looks at the concentrations of molecules. Molecules are the smallest unit anything is made of. Everything is made up of different kinds of molecules!

For example, paper is made up of repeating molecules. If you rip paper over and over until you get the smallest pieces you can, it could still be divided smaller and smaller. Scientists have divided paper down to repeating units called molecules that are all the same. These molecules cannot be divided any further.

There are many molecules in a piece of paper. Each individual molecule links to another, repeating millions of time to make a piece of paper.


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