I was reminded by a comment on the anti-microwave.
IS N2 any good at cooling things without being dnageorus?
I mean, if you try to cool some beverage bottles with the stuffv, ytou just have lots of glass and ice. And food… alsio freezes and is vcery birrttle for a tliee while, as whell as oihnoitg being very dangerous to handle.
OKayt, never mind abouty ferzzing stuff.
What happens if you drop a gram of liquid N2 into a large glass beaker filled with liquid water?
I dunno how dense liquid N2 is. I’ll pretend it’;s heavier than water.
I imagine - the droplet falls through the surface of the water, but as heat transfers picks up and ice forms really quick, it will be slowed and stopped beofre it hits the bottom. A ball of ice constantly expanding. Probelm - nitrogen is constanly evaporating, and inside the ball is a contstnly incrfedasing pressre spafe of nitrogen gas. Soon, the pressure will perhaps be high enough to break the ball.
So, you get two interesdting noises - one, the sound of ice freezing suddenly. I’ve heard this when I went out at 3 in the morning on a cold Vermont night. No snow, no wind, maybe -15 degrees F. I had a glass of water and poured it on a flat stone. Less than a second later CRACK the thing is solid white.
Second noise ios the ice ball breaking as N2 escapes.
Seriously though, I once saw a fun show using liquid nitrogen at my local science museum. Two neat and easily replicable tricks were dropping one of those rubber “super pink” balls into N2 and then shattering it with a hammer. The second one was to fill a basin with water and dish soap and mix it until its all bubbly, then drop in a little N2 and flash freeze the bubbles. Then smash them like so many delicate glass spheres. Good times.
it will almost always vaporize on contact with air, but if your skin comes in contact (like when retreiving in item dunked in the stuff) the result is loss of tissue - it will die, turn black, become gangrenous if not amutated, etc.
Are you just speculating about the ball of ice forming around the liquid N2?
Because my guess is that it would just boil away, perhaps violently. Yeah, ice would form in the water, but I expect everything would be moving around too much for it to freeze into a ball. Like a slushee in a blender on high - without a lid.
But I did say that was a guess. Maybe someone with access to liquid N2 can expermient (carefully, please) and enlighten us.
There’s nothing reckless about it. If you’re quick enough, the Leidenfrost effect will protect you. Liquid nitrogen has a low heat capacity, so it warms quickly. The initial feeling of plunging ones hand into a container of N[sub]2[/sub] is “cool and bubbly” rather than freezing cold.
I’ve never tried this trick, but some folks even know how to safely gargle with liquid N[sub]2[/sub]. Do not try this without understanding the physics !
just to reiterate -liquid nitrogen is very dangerous. It was reported in Chemistry in Britain recently some someone died after swallowing liquid nitrogen after a dare.
It is fun to see little drops skoot across the floor, held up by the pressure of the vaporising nitrogen.
Putting a little liquid N2 into water. You cant see anything because of all the mist and violent bubbling that comes up. essentially vast anounts of cold wet N2 gas is released into the air and you cant work out what happens
I used to work in a pharmaceutical lab and regularly used liquid nitrogen. It’s not really all that dangerous (although I certainly wouldn’t swallow it!).
I have dipped bare fingers into a beaker of the stuff, purely out of curiosity, and came to no harm (the rapidly vaporising nitrogen forms an insulating layer around your skin due to the Leidenfrost effect referred to above). However, when I was stupid enough to try this with a mixture of dry ice (solid CO2) and acetone, I managed to freeze my fingertip instantly (I yanked it out PDQ, so no major damage) despite the temperature being more than 100 degrees Celsius higher. (The acetone, of course, does not evaporate around your finger).
In terms of dropping it in water - firstly it doesn’t sink as the density is about 0.8g/ml. As scm1001 says, you just get a lot of spitting and clouds of vapour as water in the air condenses around the cold nitrogen gas that’s liberated.
One danger when using large quantites of liquid nitrogen is that of asphyxiation. Say you have a a litre of the stuff. One mole of liquid nitrogen is about 35ml, so you have nearly 30 moles of the stuff. Spill that and it all evaporates, and of course 1 mole of gas now takes up 22.4 litres. Those 600 litres of nitrogen gas can do a good job of displacing the ambient air in a confined space. Fortunately in the lab we’d work with fume cupboards and very efficient air conditioning.
Another good cryogenic party trick is to pop a small lump or two of dry ice into your mouth. Keep it rolling round on your tongue so you don’t freeze one spot, creep up behind someone, tap them on the shoulder and breathe out of your nose. Cue impressive clouds of dry-ice smoke Try this at your own risk, of course…
LN[SUB]2[/SUB] can be used to make ice cream, which is a lot of fun. Simply mix up a batch of cream, milk, sugar and chocolate, and pour some into a styrofoam cup. Add the liquid nitrogen, stir, and voila!
I used to work at a science centre, and we had lots of fun doing liquid nitrogen demos. One of my favourites was to make a little balloon doggy, and give him a liquid nitrogen “bath”. Doggy would shrink into nothing, so then I would have to give him “mouth-to-mouth” resuscitation to bring him back to life. The kids loved it
However, I’d like to reiterate the warnings of happyheathen, JCHeckler and scm1001 - there are lots of ways to be badly hurt by liquid nitrogen. Don’t play with the stuff unless you have the proper safety gear, and know what you are doing.
Fortunately, although liquid nitrogen is relatively cheap and easy to get hold of, clueless people aren’t likely to be able to do much with it, because Dewar flasks are seriously expensive, and it won’t last long in any other type of container. I’m not sure whether there are regulations regarding who can buy it, either. At work, we had to be quite strict about where it was kept and who had access to it.
As for swallowing liquid nitrogen, it has (apparently) been done, and the guy lived to tell the tale. Check out this link. Not sure how true this is, though - I did a medline search, and couldn’t find the NEJM articles mentioned. If anyone can confirm or deny this, let me know.
I’ve worked with liquid nitrogen a lot, and in general, you’re pretty safe. The Leidenfrost effect usually keeps it from staying close enough to your skin to do any harm. But if you should happen to form a “cup” that can contain the LN2 long enough for it to cool down the intervening gas layer and make contact with your skin, you can get a “burn”. This happened to me once on my hand. It happened to the luckless soul mentioned above who swallowed some. It could happen inside your mouth, so, although you can, in principle, "gargle’ with a little bit (I’ve seen people do this) it’s dangerous to do it with a lot. Besides, I have nightmares about cracking teeth due to differential contraction of enamel and amalgam. In short, don’t do it unless you know what you’re doing. And even then, still don’t.
If you’re looking for a cold thing for your party, get some DRY ICE. It’s more readily available, doesn’t need a Dewar flask, and lets you do cool effects like “Mad Scientist Bubbling Punch”. And if you work at it, you can injure yourself with dry ice, too.
One of my favorite tricks is one that my chemistry teacher did. After putting one of those superballs into the liquid nitrogen she put on a clear latex glove and reached into the N2 to retreive the ball. She then held the ball on the lab table and attempted to smash it with a hammer, but missed hitting her gloved finger which promptly shattered! After a few seconds of awed silence we began to realize she had slipped a hot dog into one of the fingers and held it in the N2
As for the Darwin link:
What sort of scientist says 77° Kelvin? It should simply be 77 Kelvins.
I saw a neat demo in college in a Materials Science class. The main point of the demo was to show the Meissner Effect, as the “high-temperature” ceramic superconductors had just been discovered.
Anyway, the prof also shattered a few things, such as a banana and a rubber tube. But what really stuck with me is that at the conclusion of the demo, he took the large Dewar flask and abruptly threw the entire contents of the flask into the audience!
People shouted; one guy tripped over himself trying to dodge the stream of liquid nitrogen.
What happened? It all vaporized in mid-flight. The audience only felt cool vapor hit them (which you could see, due to the condensing water vapor).
Pretty dramatic. I wonder if the guy is still doing this.
I got to play with some a few years ago. Use it to install rabbitted crankshaft bearings in an old Continental airplane engine. I shattered a piece of onion and a carrot. Both sounded like glass breaking. Froze a bunch of roll up bugs and a couple worms, none came back to life after defrosting.
As a former consumer of marijuana, I have always wondered what it would be like to fill up a bong with LN and take a bong hit.
Freeze, peel (with tools) leave shaving cream brick in a fun confined space… like a trash can. Lots of fun watching a big foam exploding mountain of good.
It breings a whole new meaning to a science project Volcano
I’ve been around people who have been hurt playing with dry ice, carbon dioxide. They were engineers, and stone sober at the time. You are yanking our chains, aren’t you?
Sure you can hurt yourself with dry ice (and much more so with liquid N2), but then there are lots of other things at the average party/BBQ that are also dangerous. I reckon a carton of dry ice strikes the best balance between cool tricks and safety - a big vat of coloured punch with a load of dry ice in it is always good - especially for Hallowe’en parties
Just a tip - don’t drop it into a full can of beer in order to cool it down, unless you want to experience a lager volcano…
BTW Osip, does that shaving foam thing really work? I’d have thought the propellant would separate out or something. Shame I no longer have access to the cold stuff, or I’d give it a try…
Try this at your own risk, of course…