This lesson is about aluminium (or aluminum), a metal once as precious as gold, now used for wrapping a sandwich.
0:00 We’ve decided to make a new video about aluminium because it’s a long time, over five years, since we made the first one and we didn't say very much.
0:12 Aluminium is a surprisingly abundant element. If you look at this periodic table here, where the area of the different elements gives you a rough idea of the abundance, you can see that aluminium
0:30 is one of the most abundant metals up there with sodium, magnesium and calcium; more aluminium than potassium;
0:38 about the same or perhaps even more than iron. We’ll never get run out to aluminium.
0:43 The problem with aluminium is that you don't find aluminium metal in nature as a metal. It’s always tied up with other compounds mostly with oxygen in clays.
0:58 You know what clays are this so too muddy stuff that you get stuck on your shoes when it's raining.
1:03 To get the aluminium out of the clay, that is to break the aluminium-oxygen bonds which are very strong requires a lot of energy which comes from electricity so
1:17 making aluminium is very energy-intensive. That's why people like to recycle aluminium, because once you've got it's worth preserving.
1:28 But it's fantastically important because aluminium is a very light metal and it's often used as an alloy because
1:38 the aluminium alloys are stronger than the aluminium itself so if you’re using it for an aircraft or some other use like that where you want to combine lightness with strength then
1:55 the stronger you can make it the better. But when it was first made in the nineteenth century isolated as a metal it was terrifically valuable and there are stories of the French Emperor serving his honoured guests
2:09 with aluminium plates or aluminium cutlery; while less important people had silver or gold.
2:16 But those times are passed and now you can get cupcakes and things like that surrounded by foiled aluminium. Aluminium is a very good metal for making things because it has a very thin coating
2:32 of aluminium oxide on the surface, which prevents it reacting with things. But as soon as that coating goes it becomes very reactive.
3:09 Here on base to hearing Houston? Oh there quite wide, Joe. OK, and I guess for a stand for your hard game I want not protect checker. OK
3:20 You may have seen a video where we put copper chloride in one of these cupcake holders. First of all I'm going to dissolve some up and make a fairly concentrated solution.
3:36 I’m going to place this here and what came out was this, or other, the copper chloride came out through the hole. It starts boiling really quite nicely now imagine I was doing this for my children, who were quite small at that time
4:00 and bush! and the aluminium was completely dissolved up forming aluminium chloride and copper metal. In my own research
4:11 aluminium is quite important, quite a lot of our equipment uses aluminium not so much for the high pressure tubing that we use, because quite a lot of my research involves high pressures,
4:25 but we use it for the metal blocks that we put round the tubing so that we can heat it up. Aluminium has a good electrical conductivity and it also is easy to machine. This is a piece of equipment here
4:40 where we have a tube going down the middle, you can see the diameter of the tube here; round it is an aluminium block and an electrical heater. Now this particular case,
4:54 there was an accident or a mishap because the thermal cup that was controlling the temperature of this fell out so the heater got hotter
5:06 and hotter and eventually the aluminium melted and pulled down here and I think this is really beautiful.
5:17 Well fortunately I was not in the lab or I would got very angry with my students, but I think when it happened it was quite exciting; this would have been blowing
5:28 almost red because the melting point of the minimum is around 500 degrees centigrade. But then, once it formed, originally it was very shiny but quickly it again
5:39 developed; the surface layer of aluminium oxide. If you have fine particles of aluminium and blow them into a flame, then they will burn quite spectacularly and you form aluminium oxide.
5:57 Now on the face of it the aluminium oxide sounds a rather boring compound, but it's really very useful and we use it quite a lot in our research in all sorts of different ways. It looks like a white powder.
6:12 Not very exciting, but in our group this aluminium oxide has been a fantastic catalyst also to reactions that we didn't expect have gone with this material. My students keep it in a bottle almost like a
6:28 magic catalyst and I’ve then been given a little too show you. It acts as a solid acid, which can be used at very high temperature and we'll get various acid catalysed reactions
6:42 of organic compounds. It will make ethers; we have made various alkenes and a whole series of different compounds. My students still use it very much. If you melt the aluminium oxide, which we can't do here but it can be done
6:58 Industrially, you can make single crystals, which are transparent like glass and then you can grow a single-crystal tube, like this one, which because it's a single crystal
7:11 is terrifically strong. It’s the defects that make something weak and so if you have just one crystal, then no defects and so it's very strong, so you could put it a very high pressure
7:25 inside this tube without it blowing up. You could make that tube out of metal, professor? But if you have metal then you can’t see what's going on inside and we are using these tubes
7:37 for photochemical reactions so we take a light like this and shine it on the chemicals going through the tube under high pressure and we can convert one chemical into another. We can do this
7:52 very efficiently because the light is absorbed by the molecules that we want to react and so we don't waste the energy on everything else.
8:01 And using LED's which is a very efficient light source, you can get a process that is very energy efficient. And it all depends on having the sapphire tube. This is synthetic sapphire;
8:15 the real sapphire, the gems, has impurities in the mood by the metals, which give the nice colours particular blue. Princess Kate has a blue sapphire ring, which belonged to her husband's mother Princess Di
8:30 before her and so these are very valuable ones, but synthetic sapphire is also expensive, but not in the same class as a natural gem.
8:42 What can make you do it of the gas of the sapphire effect you can not do it? Nature has time. The people who grow this will take hours or days or perhaps weeks to grow it.
8:56 Nature can spend thousands or millions of years growing a particular gem and therefore they can heat it up and cool it down in natural surroundings and volcano
9:09 or whatever far more slowly than people can afford to do industrially. There's a lot of argument why you should call aluminum or aluminium. Now, there isn't
9:21totally correct one because both forms are acceptable, but all, or nearly all, chemists use aluminium because it's very important to use a standardized nomenclature right across the world
9:36 and I think aluminium sounds nicer. Hi, professor, my question is: is it aluminum or aluminium?, ‘cause I want to know how to call my aluminium marvel.
9:46 There was a decision in nineteen ninety by the UPAC, the International Union of the Pure and Applied Chemistry that it should definitely be called aluminium but then they relented three years later
10:01and said you could use aluminum as well, but if you're a serious chemist you really need to say aluminium because otherwise people won't find your papers, your publications,
10:15 when they search because they'll almost certainly put an “I” in the name.
Aluminium is frequently used or used frequently to be used for source bonds for cooking in, because it's easy to make, easy to machine
10:33 and particularly when people used electric stoves it was easy to make the flat bottom so there you got good contact between the electric element and
10:43 the saucepan. The problem with aluminium saucepans is that if you’re cooking some fairly acid food, for example boiling lemons or rhubarb,
10:55 something like that which is quiet acidy, you can dissolve some of the aluminium and people got quite worried about getting aluminium in their food. Also if you cook red cabbage,
11:08 which is an indicator, blue for alkali red for acid, then if you boil it in the aluminium saucepan it goes blue.
11:18 And earlier in my career I used a red cabbage together with the white one to make a Union Jack, A UK flag, with the mixture of red and blue red cabbage and the white from the white cabbage.
11:34 Unfortunately I've lost the photo but it was very cross with me, but it was quite fun cooking it in the kitchen.
11:42 I did it once myself but it was such a lot of work that the second time I’ve gone to one of my students to do it
Now it's your time to prove your worth with the test 4!