Dry ice, or Cardice – as British researchers call it, is a solid form of carbon dioxide. When carbon dioxide is cooled below temperatures of -78.5 degrees centigrade, the gas gets directly frozen into a solid form. -78.5 degrees centigrade is extremely cold, and handling dry ice without proper protection can be very dangerous – could cause frostbite / burns. The point being, it’s extremely cold.
Since it’s too cold compared to something at room temperature, even everyday objects at room temperature can make it vaporize. A simple metal coin at room temperature would feel like a hot pan to dry ice. So, when a coin is shoved into a piece of dry ice, it creates a funny sound, just like water would, on a very hot pan; or, you could say the sound be very much like a hot metal ball being dropped into a cold bath of water (the temperature difference being much less in this case, of course).
This is how it works: The metal piece at room temperature vaporizes some amount of carbon dioxide from the piece of dry ice when it comes in contact. There’s a pressure difference (Bernoulli’s principle) associated with this process and the gas tries to escape. This makes the metal vibrate very fast, creating that funny sound. This is how it sounds…
Metals work best because they have a good thermal conductivity. For the sake of trying it out yourself, if you have a piece of dry ice lying unused, you could dip a spoon in hot water and make it touch the piece of dry ice. A slightly warmer spoon will probably give you a better effect. And then the spoon will be singing…
Short of time and keeping up with a busy schedule, I looked around for something interesting to learn today and I found this cool video of very interesting experiments that were done with liquid Nitrogen on ScienceDump. There are 11 such experiments that are shown in the video…
The first one is a Liquid Nitrogen explosion, something like this professor did some time back. To demonstrate his students how Liquid Nitrogen expanded, he blew up a container of Liquid nitrogen to toss 1,500 ping-pong balls. [Video]
Is an Aeolipile, or a rocket styled jet engine made using liquid nitrogen A.K.A Hero engine. Liquid nitrogen heats up inside a container, expands and comes out of tiny orifices to create a jet that makes the container spin. A simpler version of it can be done using a ping pong ball (again). [Video]
The third one simply is a demonstration of what happens when you eat a biscuit dipped in Liquid Nitrogen.
Fourth one again is something you’ll have to see to get really impressed by what some solids at very low temperatures can do. A nice demonstration of something similar is done on this video. [Video]
Fifth one! Oh, the Leidenfrost effect. We’ve talked enough about it already. [Here]
Others are all pretty interesting too. The eight one probably takes the cake – brings back a dead creature to life, or does it…. But I won’t spoil them for you. Watch the video now…
A couple of days back I wrote about the hottest place on earth. That made me think of how cold the coldest place would be. I was sure it’d be somewhere in one of the poles, but I wasn’t sure where exactly it was.
This is what Google said:
Aerial photograph of Vostok Station, the coldest directly observed location on Earth. The lowest natural temperature ever directly recorded at ground level on Earth is −89.2 °C (−128.6 °F; 184.0 K), at the Soviet Vostok Station in Antarctica, on July 21, 1983.
After a little more digging, I found that his was the old record. Turns out, the coldest place on earth now, not counting the laboratories, is still in the high ridges of the East Antarctic plateau close to Vostok station. It’s called the Dome B. And the coldest times happen when all the conditions are perfect.
When the conditions are right, the temperatures during winters can reach minus 92 degrees Celsius!