We're outside here just to show you the reactivity of this lovely stuff here, liquid oxygen,
so you can see, wonderful liquid oxygen, nice blue colour, so over here on the table,
We've got a tin tray which we're going to use to contain the experiment that I'm going to
show you next, so we've got our favourite liquid oxygen there, strongly oxidizing
very very reactive, and here I've got some cotton wool. So this is the same stuff that we use to
take make-up off or perhaps our partners or our girlfriends or our wives, and it's the same
stuff that we use to wipe our babies bums. - Oxygen is an interesting element,
because it exists in 2 forms. The taught form which we breath all the time is O2,
2 oxygen atoms joined together, and there's another form called Ozone which
has 3 atoms arranged like a letter V, or letter V ,this way up.
- Oxygen has unpaired electrons within the molecular orbitals in the atom which is around
the structure, and these unpaired electrons give rise to colour, and that colour is blue.
So blue is often perceived to be the colour of solvated or unpaired electrons.
And you can see here the lovely blue colour. Now lot of chemists are really scared when
they see the blue of liquid oxygen, because liquid oxygen is very very reactive.
Generally you only make liquid oxygen by mistake. Not like today when we're making some on purpose.
And if you've made it by mistake in an uncontrolled way where there might be organic
molecules, perhaps simple organic chemicals like hydrocarbons, grease or perhaps a highly
elaborate compound, they tend to detonate and they tend to cause very energetic experiments
so here it's very fluffy, not very reactive, doesn't really burn, cinders, might smolder,
here we go. We're goint to pop it in the tray, and then we're goint to fill up all of the void
space, all of the space between the cotton particles with oxygen so you might want to step
back after this bit, Brady, so here we go, here's our liquid oxygen, do you want to come in and zoom
in on it and see me? - I've got it zoomed nicely.
- Okay so here you can see the lovely blue liquid oxygen colour going in to the cotton wool
particles, so here we have a match on a stick, And I think you can see it's probably a light,
we have our fire, we have our oxygen and we have our fuel and let's see what
happens if we put them all together. Are you ready? Okay?
- Woohoo! and there she blows!
- And Ozone is much more reactive the oxygen. So near the Earth's surface, where you and I
are at the moment, ozone is really quite dangerous because if you breathe it in it can start reacting
with any sort of molecule that has bonds between carbon. But in the upper atmosphere,
ozone is extremely important because it absorbs ultra-violet light that comes from the sun
and stops this ultra violet light attacking the molecules in biological species on the surface.
If it wasn't for the ozone in the upper atmosphere all of us would be if not dead, certainly very
much less comfortable than we are at the moment.
So Neil is now connecting up a piece of that tube to the oxygen cylinder and he's going to fill up
this gas jar with oxygen and we're going to do a really classic experiment, the one that everyone
learns at school, a test for oxygen which is to re-light the glowing splint. So we have a
traditional gas jar full of oxygen. So here you can see we're burning a splint. So this is
the wood burning in excess oxygen around us okay? So now what we're going to do is we're going to
take the splint out so that it is just glowing, if I blow on the splint you can see it gets brighter.
Now we're going to try and re-light that splint by putting it into a very oxygen rich atmoshpere,
so now we move over to the jar, and we'll put in our glowing splint. And you can see
the flame comes back to life, so that's a test that everyone learns for an oxygen rich
environment. - So what happened? What made that happen? - Well the incrased oxygen content
concentration re-ignites and re-initiates that oxidation of the wood or the burning of the wood,
so I'll do that again, So there we go. Flame again. -Cool.
Captions by www.SubPLY.com