This is a syringe with a piston.

As I push the piston in here, the air will squirt out the other end If I put my finger over the end and now push it up.

So start over 50 I Let's go up to 30 and see if I'm pushing that far.

Yeah, I could push it, but it gets harder.

25 on The pressure is getting enormous.

And the reason is that the air is made of little molecules in here which are bashing away the sides of this on hitting the piston.

So if I push it up, they find that it's there, too many of them.

And they're hitting this pittance so much that it's pushing it down and I have to do work.

To squeeze is to get the volume to change.

So I like to illustrate this using Julian to operate this apparatus because I used these apparatus and they break down.

This apparatus is a scale, that version, so you can see the molecules.

These molecules will move around on me.

They're steel ball bearing on.

They will move up and bash around as though they are particles in the air.

Now, Julian, could you turn it on and we can see how it goes Now I would like to put in a piston.

Here is a polish starring piston, which more or less fits a thing and will float down slowly until it covers that.

Now, if you turn it on gently when it gets down near the bottom, you'll see that it will bash into this.

Hold it, and the more energetically Julian puts the energy into this, the higher this piston get that, if you turn it way up, will move the way out.

You see these particles fasting in the pit as a back into it pushes it up more, more.

It's coming back to my syringe.

I started off with the gas particles whizzing around in here, and as I push this down, they hit the top surface and bounce off.

But you can't see them, but that's causing me to have to push much harder as the volume gets smaller and smaller.

There is still the same number of particles in there, but there's more of them bashing the top surface at any one time until it gets to the point where I can't move this any further because it's too painful on my fingers.

So I had to let it go in the same way.

Oh, dear, look at that.

I mean, look, I mean, it really is painful.

We'll turn this on up to full whack and I add these little weights one at a time on these rates represents my finger pushing down on the Pistons.

I had the first way and it's got this volume I put one in on.

It falls down on the volume goes down there now.

I had the second way is the second way on.

It goes down from there down to there, and it goes down a little bit.

Any change in the States?

Because I've already put 21 dropped down a bit more.

Thank you.

Each time that I added a little extra weight, you could see the volume decreased a little bit.

I put on one.

It went down.

A small amount put onto it went down even more on as I squash it.