You've probably seen our last two videos. One about breaking a tube of sodium underwater and the next one breaking two tubes of potassium underwater. Now the real reason That Neil devised his special device for breaking glass tubes underwater was because for years he's been holding a 5 gram sample of cesium in his cupboard.
And he wanted to see what would happen with breaking that cesium underwater. Now the cesium sample is different from the other ones that we had because that's a commercial sample which was sealed under vacuum. So there's no gas at all.
And the other difference, which is a physical difference, is that caesium metal is much denser than water. So there is no way that caesium metal itself can spontaneously float up to the surface of our trough. And for those of you who watched our earlier videos, it's important to realize that the five grams of caesium have about the same number of atoms as the weights of potassium.
and sodium that we were using in the earlier experiments. So you have three experiments you can compare. I should also say, like the others, this was filmed outside, but it was filmed a bit later in the day, so the Sun was at a different angle. And you can see this because as Neil started turning the screw, there were some interesting ripples on the surface from the vibrations, and gave quite nice patterns in the high-speed video.
But this is not chemical, this is just vibrations. Again, like the other two, as the test tube begins to break, you see some bubbles of hydrogen coming out. Now this time we know it's hydrogen because there was no gas at all inside the vessel. One part of the test tube you can see shoots across the screen and ends up...
on the left hand side, close to the wall of the vessel. But that piece near the wall still has a lot of cesium in it. And the water will then rush in again.
It reacts with the cesium, so there's another big explosion. And it's really big because if you look at the side of the plastic vessel, which is pretty rigid, it bulges out. And the surface of the water looks like a model tank. When they're videoing a disaster movie of a storm, huge waves, and potassium it was just a few ripples.
So a lot of energies come out. And this video is probably the best demonstration that I've ever seen that shows that cesium is a lot more reactive than potassium. Because we have had the conditions very much the same with one We get a reasonable reaction.
Here we get something where Neil was worried that his plastic vessel might be ruined. We have also with this tank of water a sort of crude energy meter. The more the waves go, the more energy is released. And here, if you look at them side by side, potassium, slight waves, cesium, hurricane.
Of course, we didn't do rubidium because Neil didn't have rubidium stashed away. And so, if any of you have got five grams of rubidium, we're always up for trying it.