Brady's given me a Christmas present
This is so-called 'artificial snow', or sodium polyacrylate
It's a white powder. If I put a little bit on the desk...
And what happens with this and why people like it: is that it absorbs water very easily.
I've got some water here. And since it's just water, I can do the experiments in my office.
So, are you ready? We'll try and see what happens.
If you pour a bit of water on this
You can see, it swells up
Probably I didn't put enough
Bit more...
It feels very like snow. I can even dribble it on my 'DNA' Christmas tree, that I was given as a Christmas present
Perhaps we should try the experiment on a larger scale
I've got a beaker here and we'll put the lot in
This material is famous for its absorption of water
So if we put in some water here
You can see it really swells up.
If we stir it up, it then starts expanding even more.
The reason why this stuff works is because it's a sodium salt
It is so-called 'acrylic acid', which is a small molecule
which has been polymerised. So you've joined a whole series of acrylic acid molecules together
to form a chain
Because it's an acid, it can be reacted with sodium to make the sodium salt.
The chains, because of the way the polymer is made, are actually linked together so they can't easily separate
So, when you add water, just like to many other sodium salts, it absorbs water
and the sodium ion (Na+) gets water going round it, to hydrate it - gives out energy
If it was sodium chloride the crystal structure would just collapse and it would all dissolve
But because these organic chains are joined together and interlinked, they can't dissolve.
The powder, each grain, is almost like a large molecule. And so, it just swells up
And this has all sorts of practical applications. It's used particularly in babies' nappies
or as you would say in the United States: 'diapers'
where you want to absorb the liquid and keep the baby dry. So you put some of this material inside a pad,
and so the liquid goes through the pad, and swells up, and the baby stays dry. You can use it for other
absorbent materials as well. But it's a very simple material and it's fun to use at Christmas.
So let's make it snow a bit more
Let it snow
200 millimetres of water. We'll try a new, fresh container. This one may be better because all being well
it won't be able to block the beaker in the way. So it's snowing quite nicely
Makes a terrible mess.
(Brady) Who's gonna clean that up?
Me
Everybody else has finished for Christmas. So can't even rely on Neil to clean it up this time
So, happy Christmas! To all of our viewers! And look forward to some really exciting videos for 2015
And a happy new year to you all, and enjoy your chemistry