# What is Diffusion?

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• 0:03 Definition of Diffusion
• 1:50 Examples of Diffusion
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Lesson Transcript

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

Learn about diffusion and how this process works. We'll look at some examples of diffusion happening. You'll be able to take the short quiz that follows to test your knowledge.

## Definition of Diffusion

Let's look at something that you may have experienced at some point in your life. In some large cities there are transit systems that include trains with multiple cars, such as the New York City subway system or the Chicago L. You have decided that you are going to take the train to a baseball game or a concert downtown, or maybe even a rally at your city's convention center.

You board the train at the beginning of the line. More people board the train at each stop. By the time you get to the fourth stop, you realize that the car you're in is very full, and you don't have much space to move around or even simply raise your arms. You look through the window into the next car and see that it's almost empty. You figure that you'll have more space if you switch cars at the next stop. Upon reaching the next stop, you get out of your current car and move to the next car so you can have more space for yourself. So you essentially went from an area with more people to an area with less people. This is the same as the principle of diffusion.

Diffusion is when particles or objects move from an area of higher concentration to an area of lower concentration. Concentration refers to how much of a particular object or particle is in a given space. So in the example of the transit train, you went from an area of higher concentration of people to an area of a lower concentration of people. This means that you went through the process of diffusion.

The overall goal of diffusion is for the particles or objects to reach equilibrium. Equilibrium is when the amount of the particles or objects is the same throughout a solution or is equally dispersed through a given area. Equilibrium will be reached with the train you were on if more people were to move to the other cars of the train so that each car has the same amount of people.

## Examples of Diffusion

You're probably beginning to get a better idea of what diffusion is now, so let's look at some other examples of diffusion that you may have encountered throughout your life. As a kid, you may have learned how to make lemonade or fruit punch from a powder. You filled a container with water and then added the lemonade or fruit punch powder. The powder starts out as a clump with each particle in the powder having very little room to move. The particles of the powder will start to move away from each other so that they have more space. This diffusion of the powder to move throughout the water will create the fruit punch or lemonade. So the powder went from an area of higher concentration of powder to lower concentration of powder.

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