Diffusion

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Diffusion

Have you noticed when someone walks past you, you can smell their perfume?

Sometimes the smell will even linger.

When you spray a can of deodorant, the particles move randomly through the air.

They spread out, some entering your nose, while others randomly spreading out and filling up the room.

This is called Diffusion

Click on the spray can to see diffusion

So, why do they diffuse?

Remember, gas particles are in constant motion, meaning the particles will move randomly in the air.

You can see this as ink particles spread through the water.

Factors affecting diffusion

Temperature

As we increase the temperature, the particle gain more energy. This causes them to move more.
The more they move, the quicker they diffuse.

More heat = quicker diffusion

Less heat = Slower diffusion

Particle size

A particle of water (H2O) is different to an particle of oxygen (O2) and to a particle of hydrogen (H2).

What we will see, is the bigger molecules diffusing slower, while the smaller molecules diffuse faster.

Diffusing substance

Remember how particles in different states are structured. What do you think is easier. To get through a crowd of people set up like a liquid, or a crows of people set up like a gas.

Since a gas’s particles are further apart that a solids, particles can diffuse quicker through them.

Remember everything, including air, is made of particles.
Imagine if there are 2 people, a really big person and a really small person. They have to get from one side of the room to the other, but in between are lots of people. The smaller person will be able to move quicker through all the people than the bigger person. This is how size affects diffusion.

Click the race button on the animation to the left.