Subtitles section Play video Print subtitles You've probably seen our last two videos, one about breaking a tube of sodium under water and the next one breaking two tubes of potassium under water. 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 caesium in his cupboard and he wanted to see what would happen with breaking that caesium underwater. Now, the caesium 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 their 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 its 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 caesium in it and the water will then rush in again it reacts with the caesium 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 are videoing a disaster movie of the 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 to 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, caesium: hurricane! of course we didn't do rubidium because Neil didn't have rubidium stashed away and so if any of you've got five grams of rubidium we're always up for trying it.
B1 potassium vessel underwater water test tube tube Underwater Caesium - Periodic Table of Videos 3 0 林宜悉 posted on 2020/04/04 More Share Save Report Video vocabulary