David Kirtley

They can move around.

They have some kinetic energy, but they're still pretty contained.

They stay in the bowl.

Keep heating it.

Now you're in gas.

And now these particles are free to move around.

They're moving around.

They're bouncing off of each other all the time.

And you can keep heating it from there.

And that's where we talk about some more phases of matter.

We can add a little bit more physics here.

We talk about rarefied gases.

So when we think about most gases that humans interact with, they act like a fluid.

And what I mean by that is that they're colliding with each other so often that the particles at any one place here, the air is roughly the same temperature as the air here.

That these particles are bouncing off of each other.

If you put a really hot one right here, it would then cool enough that all the air is roughly on the same temperature.

But you can be what's called rarefied.

And this is like space.

This is where now you have particles moving around, but they don't,

collide with each other very often.