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Fun with liquid nitrogen

malbui

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malbui
Joined
Nov 8, 2004
Messages
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So today I popped up the road to the local shopping centre to start on the Xmas shopping, and to my delight I found that CERN (which is just down the road) were exhibiting there. The best part was one of their blokes doing a lengthy demonstration of the fun things you can do with liquid nitrogen, balloons, rubber tubing and a hammer, powerful magnets and ceramics. Entertaining and informative - I was very impressed. And Mlle Malbui, who's almost six, was transfixed by the whole thing and has decided that being a physicist is even better a career than being a ballet dancer.
 
Great stuff!

This summer I took a job which involved me handling liquid nitrogen on a daily. It was great fun but I suspect being a physicist is a lot more fun and economically sound than a contract killer on Heracleum :)
 
I've worked in a few materials labs so have had access for ages. At one place we used to do some silly things with it.

We used to go to a pub on Friday lunchtimes and so we'd ask who was coming. Now and then people would make the excuse that they had sandwiches so weren't coming. We'd wait for them to leave the office then take their sarnies out and pop them into the LN2 and then put them back in their lunch box. Funny as hell watching them open the box at lunchtime and then get their coat ready to go over to the pub!

We also had a lab manager that was always leaving his pass lying around (you know the ones with a chain or ribbon to hang around your neck). We got the biggest container we could find, filled it with water, dangled his pass in then froze it with LN2. We also had a very cold freezer (-50°C or something) and put the block of ice in there for the rest of the day. At the end of the day we left the block out and scarpered. Lab manager was last seen walking across the car park swinging this massive block of ice with a very disgruntled look upon his face! That'll teach him to leave his pass lying around.
 
I did shows with LN2 almost everyday back in the 90's. I still think that my hands are thermally immune as a result. :D

I enjoyed taking a balloon filled with Oxygen and cooling it to a liquid. Nice and blueish in color.
 
We used to play with LN2 in my first job at a lab. We discovered that some poured over a floor would clean it nicely, and that sandwiches and cherry tomatoes would shatter satisfyingly after being chilled to 70 kelvin.

I became more cautious of it though after receiving my first liquid nitrogen burn. You could pour a little into the cup of your palm, and it would dance around happily in it, supported by a cushion of warmer gas (the Leidenfrost effectWP).

Until, that is, that gas cushion collapses and the LN2 comes into contact with your palm. I got a burn that was as deep as it was wide.
 
We do demos with LN2 every year on the day employees are allowed to bring their kids to work.

Last year I had to temporarily halt the demo because the kids were sitting on the floor in front of demonstration table. The LN2 was boiling off from the dewar and was starting to exclude the oxygen in the kids breathing zone, plus they were exposed to direct contact with a splash or spill.

Once we got the kids moved back a safe distance, the demo continued.

The kids enjoy the show though. We use it to launch corks out of rigid tubing, freeze fruits and vegetables then shatter them, etc.
 
I work for an engineering company that deals with cryogenic fluids on a daily basis. We're out in the desert and let's just say that you don't want to be a snake that finds his way into our workshop.
 
My A level physics teacher managed to lay his hands on some liquid nitrogen and he gave us all the usual demos; shattering roses and bits of rubber tubing, that sort of thing. At the end, he had some left over, so for want of something better to do, he poured it over the table. Guess who was the poor unfortunate standing at the opposite end, who took a direct hit at hip height? No injuries, but I did get severely laughed at, standing there as I was with the front of my trousers smoking.

The best LN2 trick I've ever heard about (although never seen deployed) is to pour it down a sink, put the plug in and block up the overflow pipe. This causes a pressure build-up somewhere in the plumbing system, which will cause the water to shoot out of the u-bends in some other random sinks in the building.
 
We would pour it under the lab door as we heard our phys chem lab prof returning to see if we were all still alive.
 
Myriad said:
Four words: liquid nitrogen ice cream.
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I saw that demonstrated on the Tonight Show. Leno said something about wanting to get some of that liquid nitrogen for himself. The scientist guy (don't remember his name) remarked that liquid nitrogen was a bit expensive. Leno replied "What do I care, I'm rich?" That stuck in my mind because I've rarely heard rich people describe themselves as rich.
 
jwwalker said:
I saw that demonstrated on the Tonight Show. Leno said something about wanting to get some of that liquid nitrogen for himself. The scientist guy (don't remember his name) remarked that liquid nitrogen was a bit expensive. Leno replied "What do I care, I'm rich?" That stuck in my mind because I've rarely heard rich people describe themselves as rich.
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Billy Connolly has a pretty good routine where he describes his teachers at school saying that he'll go nowhere. "You're a jellyfish, Connolly. A spineless jellyfish, and you'll never amount to anything!"

His response:

"Well, I'm ****ing rich."
 
If you spit in it, you get a perfect sphere, which can then be thrown at people. Not that I'd ever do such a thing.

malbui said:
rubber tubing
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My university had to stop doing that at open days after someone lost an eye. Smashing a frozen piece of rubber sounds like a great idea until you realise that it's pretty muc h the same as smashing a piece of glass.

arthwollipot said:
I've heard that it's incredible. The ice cream freezes so quickly that there's no time for ice crystals to form. Or that they do form but they can't grow large, so the ice cream is smooooth.

I'd love to try it someday.
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As I said when I first heard of this, it sounds absolutely horrible. Why would you want smooth ice cream? The whole point is that it's got bits of ice in it so there's a nice crunchy texture. Well, that and chocolate.
 
Cuddles said:
As I said when I first heard of this, it sounds absolutely horrible. Why would you want smooth ice cream? The whole point is that it's got bits of ice in it so there's a nice crunchy texture. Well, that and chocolate.
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So you like your ice cream partially melted and then refrozen? That's like saying that you prefer hamburgers to be burnt.

Weird. :nope:
 
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I do LN2 demos every year for my physics students during the unit on thermal physics - they're always a hit and I love doing them. After showing the standard "brittle flower" demo, they always ask what would happen if I were to stick my hand in the LN2, so I do it for them...

... of course, nothing happens so long as you do it quickly - the Leidenfrost effect being what it is. But then I say, "I know, you want me to stick my hand in there and leave it there, right?" Of course they answer in the affirmative.

So then I go through a demo where I fool them into thinking that I've frozen my finger solid and then I break it against the lab table. It scares the hell out of them every time! :D

Check it out (note that I'm not Mr. Blau, I just don't have myself on video doing this trick):



ETA: Btw, LN2 ice cream is extremely tasty and smooth. I highly recommend it - yum! :)
 
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MattusMaximus said:
So then I go through a demo where I fool them into thinking that I've frozen my finger solid and then I break it against the lab table. It scares the hell out of them every time! :D
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:D

That's so cool (geddit?). I'd put that in the same league as the introduction to urology where the demonstrator dips his middle finger in then sucks on his index and comments on the taste. A simple trick, but it had me going at the time.
 
My dad was a dermatologist and used LN2 to burn off warts and skin cancer/moles. He sometimes brought leftovers home to let me play with.

One day when I was about 8 years old I discovered condensed oxygen. While playing with LN2 in a steel cup on the floor on a synthetic fiber throw rug, I was dunking lit matches and other burning objects into the vapors to snuff them out (I was also a notorious firebug), I dropped a lit match beside the cup onto the normally only slightly (just barely) flammable rug. WHOOSH! The rug in a foot-wide circle around the cup flared up vigorously and as quickly died out, leaving a cue-ball bald spot of backing without pile.

Years later I realized that Oxygen had condensed and liquified out of the air and saturated the area around the cup. Dangerous lesson, that one.

Dave
 
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