So we're gonna go find some liquid Nitrogen.
We keep it in a really large dewar tank at the back of the shop,
so we're gonna go find that now.
So this is a dewar that we used to keep the liquid Nitrogen in within the building
so it's much more convenient for us and our students to get it.
So what we're gonna do now is we're gonna fill up our small dewar
to carry the Nitrogen back to the lab.
So you can probably hear it hissing and fizzing going into the bottle,
and you can see all the Nitrogen evaporating off.
Nitrogen exists as a gas. Molecules of N2.
And it is interesting, because the bond between the two Nitrogen atoms
is the strongest bond that you can get between any two atoms in the Periodic Table.
Any two atoms that are the same. Sometimes, if you have two atoms
that are different, the bond can be slightly stronger,
but the NN triple bond is one of the strongest that you can have.
So what we're doing is we're filling up the dewar with liquid Nitrogen
so that we can take that back to our lab to do our next experiment.
So many explosive compounds, things that you've heard of,
like TNT and other explosives, all contain Nitrogen,
which are isolated atoms, and when the explosion goes off
the atoms come together and release energy.
Nitrogen is used widely in laboratories, partly because it's not as reactive as Oxygen,
so if you do an experiment in an atmosphere of Nitrogen
you can avoid reactions that might occur with air.
You can also use Nitrogen when it's liquified as a coolant.
Liquid Nitrogen boils at -196 degrees Centigrade, 77 degrees absolute,
and you can just hold it in a normal thermous flask.
So this is a dewar of liquid Nitrogen, and you can see that the Nitrogen
is evaporating from the top, coming out and frosting,
coming down over the sides because it's a little bit more dense than the air.
You can see it's heavily laden with ice, and you can see
that the ice crystals are starting to grow on the top of the dewar here.
It's very cold though, so we mustn't touch it for too long.
So if we just tip some out on the floor,
we can see that the Nitrogen itself will come out like a liquid,
like pouring water, but the interesting thing is,
water, when I pour it on the floor it forms a puddle.
It does nothing useful. In fact, it sort of gets in the way.
But liquid Nitrogen, when I pour it on the floor,
it forms these really quite nice bubbles, and they fly across
to the side of the room and take all the dust with them. Pretty cool.
But if you put materials like rubber or flowers into liquid Nitrogen,
instead of being soft and bendy they become really rigid,
and you can smash them with a hammer.
So you can see all of the bubbles forming on this steel tray now,
and they're sweeping away all the dust quite nicely
as they evaporate and move further afield.
So Neil's got a piece of tubing, and it's really quite flexible tubing,
you can see it's really floppy, and now he's gonna put it into
the cryogenic liquid Nitrogen and freeze it,
and see what happens to the rubber.
But you see another interesting thing there is that the liquid Nitrogen
is siphoning out through the tube, and that's a really good joke,
because you can direct that siphon at someones trousers and freeze their legs.
So I think that's enough, Neil, let's see if it's a bit harder.
Wow, that shattered.
And there's quite a nice little operation that I've heard about,
in which you can take the lens out of somebody's eye
when they're suitably anaesthetized, and this lens can be frozen
and then put on the lathe and you can change its shape
so you get the right shape, and then you let it unfreeze,
it goes soft again, and you pop it back into their eye.
. . . . . . . . . . . . Captions by www.SubPLY.com