But this week we're going to look a potassium on DDE.

As you know, potassium is more reactive than sodium.

One of the things which you might not realize in fact I had for gotten is that metallic potassium is less dense than metallic sodium, So if you have potassium underwater, it's much more likely to suit the surface than sodium, which has a density very close to the density of water.

Uh, ready for action.

Neil has sealed the potassium into the tube, but the Mountie Putin waas the same number of atoms approximately as of sodium.

We infected two experiments or kneeled to experiments, the 1st 1 with the test tube vertical in his device.

Thanks.

Oh, dear.

Before we start, let me just remind you that alkaline metals react with water to produce hydrogen, and they also produce the hydroxide as you watch to begin with.

As the water goes in, a few bubbles of hydrogen come out.

Then the reaction gets more violent.

Much bigger bubbles appear.

They look quite white ish because of the angle of sunlight lumps conf loot off.

It's less dense than water.

They go rather like Dave is going up inside a diving bell.

And we know that because if you look at the surface with the camera on the surface, you can see these lumps of potassium appearing, so we know they're getting to the surface quite by chance.

A piece of the tubing floats upward and inside it there is a tiny piece of protest.

Um, that's trapped on the two comes up and then it falls down again.

And you can see this little lump of potassium, which appears to be melted because it's beating rather like the gallium heart that we have seen you.

And you can see this reacting with the water really, quite peacefully.

It's not exploding or internal like that, because it's a small piece, and it's generating the hydrogen fast enough for the hydrant to escape.

And the reason it can escape is because Neil didn't quite seal up the end of the tube as well as the good of done, and you can see bubbles of hydrogen coming out.

This shows that if you have potassium, quite a small amount in a relatively unconfined situation.

It will react fast, but it won't react.

Explosive Neil is a perfectionist, and he's realised that we shouldn't be doing the experiment with the test you vertically and it would be much better to break the test tube horizontally under the water.

Wait.

So in the 2nd 1 what happened was that the test tube torture of wanting smashed the test tube and you can see the bubbles of hydrogen coming up.

But then you can see that there is quite a sizeable explosion which blows the test tube apart again, probably because of the pressure of hydrogen.

I know, because when I was doing my doctorate, I put a high pressure of hydrogen into a glass vessel and it went off with an enormous bang so you can get a big explosion with hydrogen pressure in glass vessel because you've got quite a large lump of potassium in a small volume of glass on dhe, water is very dense compared to hydrogen gas.

You can have a fast reaction, will generate a large volume of gas very quickly infraction of second.

The other thing, which is interesting, is that there's enough force in the reaction to produce modest ripples in the surface of the water.

You need to think about this because there are several kilos of water in this trough on their sloshing around, so they've been given quite a push, but just wait to see what season does.