So Neil’s got a sample of sodium. Sodium is a very reactive metal, it is stored under
an oil to stop air or moisture getting on it - stop it oxidising, stop it reacting - and
as you can see it is a very soft metal, so he is going to put his knife in and withdraw
the lump of sodium, so there is about 2 kilos of sodium here, it's a really quite large
rod. So we are going to cut a small sample of the sodium and we are going to see if we
can explore some of its chemistry.
Sodium is again a light metal, rather like lithium and it has a, a melting point about
96 degrees.
So the sodium is a very, very shiny metal and as you can see as Neil cuts some off,
you can see the quite nice shiny material. It’s really quite beautiful. Reacts very,
very quickly with air and also with water, you form the oxide layer which is the white,
or the hydroxide is the white crust on the outside.
And many of you will know that if you drop sodium into water it reacts almost explosively.
So we are going to go outside now, go get some even bigger reactions, with the alkali
metals. This is a dog bowl which is stoneware, it is very hard, not likely to break, unless
I drop it on my toes.
This is sodium, the metal that we cut a minute ago and you can see there is quite a substantial
amount of the sodium, and we are going to pop it into the water and see what we can
do with the reaction. Ok? So here we have a bowl full of water and maybe, oh, a gram
of sodium? So let’s see what happens, see what this reaction’s like. So it is reacting
really, really quite quickly and really violently with the water, and you can see it is fizzing
around and it is generating lots and lots of hydrogen gas. And see now the heat from
the reaction is burning away all of that hydrogen which is generating and you can see the orange
sodium flame.
That was um?
That was good
That is a bit of, a chunk of molten sodium has come out of there mate.
So, let’s burn that.
Oh, it’s on your camera.
Oh it is too!
Sodium chloride is transparent through infrared light and so here we have got a sheet of sodium
chloride that has been stuck on to a glass vessel so that you can have infrared light
going through it. Now this is a broken one, which my students have broken.
Is that bit, have you got a, we need a needle Neil, or a pair of tweezers.
So you can see here that these windows have been broken but you can see an interesting
aspect of sodium chloride that when it breaks it forms cracks that form at right angles.
Why is that?
This is related to the structure of the atoms inside the crystal which are arranged in a
sort of cubic arrangement. I have also got quite a nice crystal of sodium chloride over
here which I don’t know if you can see has been turned into a table lamp. And if you
switch it on it lights up. So this is just a mass of natural sodium chloride from under
the ground somewhere, probably in Cheshire or somewhere else like this where they have
large underground salt mines, deposits.
Ok so we have got another lump of sodium, and you can see it’s really nice and shiny.
Ok? So we are going to pop that into that big bucket of water. See what the chemical
reaction is, ok? So here we go! So you can see again, see the orange sodium spectrum
as the sodium is getting excited as the hydrogen is burning all that heat. Whoa! Exciting!
That is brilliant.
That is much better.
So sodium and water, excellent reaction.
That was great.
I like sodium, because its symbol Na was the nickname that my mother whose name was Ena
used to use when she was a child, she was known as Na, so whenever I see sodium in the
formula, I sort of feel a sort of warm motherly feeling from this.