Understand the Movement of Particles in Diffusion

Diffusion is the spreading out of one substance into another. But there's a bit more information we can add to this definition to make it even better.

Diffusion is the movement of particles of a substance from where there are a lot of them, to where there are fewer of them. 

Maybe it would help if we thought of the particles like a group of shy dogs. Ok, ok, keep with me here!! A shy dog wouldn't want to be around lots of other dogs, so would try and get as far away from the other dogs as possible, to a place where there are fewer dogs. 

So eventually the shy dogs would have spread out as far as possible, so they are mixed into the flowers. The shy dogs have diffused into the flowers!

Think you have got this idea? Let's see some more scientific examples in the questions that follow!