Understand Diffusion and the Particles in a Gas

You probably know that smells can spread out through a gas very easily, which is why we can smell yummy food cooking in the kitchen even when we are in the living room! But just what makes a gas, a gas?

The way its particles behave!

The particles a gas is made of are so spread out that they fill whatever space is given to them.

That also means that gases can be compressed (squashed) a little bit, as their particles are so spread out.

Weirdly, gases can flow, just like liquids. They move about really quickly too, whizzing about filling the space!

So, that's what makes a gas, a gas!

So back to the smell of yummy food cooking in the kitchen. The reason we can smell it even when we are in the living room is because the cooking smells diffuse, which means the 'smell' particles spread out in the particles of air (which is also a gas) and eventually the air is filled with these lovely smells. Diffusion is the name given to the spreading out of a substance in another substance. 

It's also why we can smell other smells too when we are far away, like deodorant being sprayed. Smells diffuse very quickly in a gas because the particles are spaced so far apart and move about so much. 

Let's try some questions.