Low on battery?

2001 a space odyssey

It’s 2015. Where’s my spaceship?

The other day I was reminded of something that happened, if my memory serves me correctly, in 2001. It seems like a long time ago doesn’t it? Strange to think that it seemed so futuristic to Arthur C. Clarke in 1968 that he named his classic science fiction novel with that date. Time is funny like that.

Anyway, back in 2001 I went into a mobile phone shop to get a new phone (yes young people, they did exist 14 years ago). I was shown one of the smaller, lighter phones on the market which was still, certainly by today’s standards, a rather blocky piece of kit. The salesman told me that phones just wouldn’t get much thinner than the model he was trying to convince me to sign up for, because that was the thinnest the batteries could be made.

How wrong was he? Perhaps not quite wrong on the scale of Bill Gate’s infamous (and since strenuously denied) “640K ought to be enough for anybody” line, but pretty wrong. Just a couple of years later lithium ion batteries became widely available, and everything changed.

Lithium-Ion-battery

Argh, my battery is down to 5%!

These days the only time most people think about batteries is when they’re cursing them for running down too quickly and scrabbling about looking for a charging cable. They’re part of modern life; something we take for granted. I’m writing this on a laptop that’s running on a battery. Pretty much everyone has a mobile phone with a battery. Lots of other devices in our households have batteries, either as their primary power source or as a backup to mains electricity. Electric cars, like the Nissan Leaf, run on batteries, and scientists are even investigating the possibility of putting large storage batteries into our houses to store any excess power generated from solar panels on our roofs.

And the majority of those batteries are lithium ion. Stop and think about that for a moment. Smartphones, tablets, eReaders and the like have changed our lives hugely over the last few years and yes, of course, they are the sum of lots of different strands of technology, including touch-screens and increasingly tiny processors. But the fact remains they probably just wouldn’t exist without the humble lithium ion battery, which provides a lightweight, thin and long-lasting (it is, really) source of captive electricity.

Lithium really doesn't place nicely with water.

Lithium really doesn’t play nicely with water.

Lithium batteries were first proposed in the 1970s, and the first ones actually contained lithium metal. Now, even if you’ve forgotten everything else you did in your school chemistry classes, you probably do remember your teacher dropping lithium, sodium and potassium metal into water and watching them suddenly burst into red, orange and purple flames respectively. It’s bad enough accidentally dropping your phone in the loo, imagine if didn’t just stop working but actually exploded. That really would spoil your day.

Lithium reacts spectacularly with oxygen too, so although nice in theory it was ruled out pretty much straight away on safety grounds. Researchers quickly started investigating lithium compounds, and lithium cobalt oxide, LiCoO2, was next up. As a general rule, very reactive elements produce much more stable compounds – and lithium cobalt oxide is much easier to handle than lithium metal.

Unfortunately it does still have poor thermal stability. Which means it has a nasty habit of blowing up if it gets too hot. A bit like that beltric acid stuff in Superman III, only without the turning into strawberry jelly and causing supercomputers to go rogue thing. At high temperatures lithium cobalt oxide starts to generate oxygen, and although oxygen itself isn’t flammable (we all knew that, right?) it does make everything else burn really, really well. Like, say, the plastic cover on your phone, or your curtains. So, that was a problem.

nissan leaf

The Nissan Leaf runs on lithium ion batteries. Big ones.

Not to worry: it didn’t take too long before Rachid Yazami found a way to reversibly insert lithium ions into graphite. The fact that the process is reversible is important: as you charge the battery the lithium ions are absorbed into the graphite, forming LiC6, and as you use it they are slowly released. The electrode that he discovered is still one of the most commonly used ones in commercial lithium ion batteries. These batteries are safe and affordable. The graphite does break down over time, in a process called exfoliation (not the facial wash type). There are ways to reduce this but as we all know from experience, while most lithium ion batteries can happily survive a few years worth of charge cycles, they still don’t last forever. It probably comes as no surprise that there are plenty of researchers out there working on new battery technologies. One of the newer types is the lithium vanadium phosphate battery (LVP), which is increasingly being used in electric cars.

Speaking of cars, we all learned at school that crude oil (the source of petrol and diesel) is a non-renewable resource. This is true, but there are alternatives to producing fuels from crude oil. Bioethanol is relatively easy to produce, diesel vehicles can run directly from plant oil fuel, and there are types of algae which can produce fuels. These alternatives also have the advantage of absorbing carbon dioxide as the plants or algae grow, so reducing the total amount of carbon dioxide that ends up being released into the atmosphere. That’s good, because pretty much everyone agrees now that global warming is a Bad Thing (even Republicans).

If you think about it, no metal is renewable. We can’t make metals (well, beyond a few atoms in a supercollider), and often there’s no really good alternative to using a particular type of metal. Having said that, scientists are working on sodium ion batteries, but they’re not commercially viable just yet. So right now, to feed our desire for new laptops, phones and even cars, we need lithium. Lots and lots and lots of it.

lithium triangle Salde Vida Map

The lithium triangle. Where batteries mysteriously disappear (not really).

Because lithium is so reactive it’s never found in its pure state; it has to be extracted from its compounds. Most of the world’s supply comes from a small group of places colloquially known as the ‘lithium triangle’, which includes the Atacama Salt Flat in Chile (generally considered to produce the best quality lithium in the world) and the Hombre Muerto Salt Flat in Argentina. Most of it, some 40-50% of the world’s reserves, is thought to be in Bolivia, where mining only began a few years ago.

It takes 750 tons of brine, and 24 months, to obtain just ton of lithium from these salt flat locations. The energy cost is high, although lithium itself is still relatively cheap (right now). It can of course be recycled: 20 tons of spent batteries can also provide one ton of lithium. So be good and recycle your phone responsibly. And next time you’re cursing your battery, just stop for a second and think of all the time and energy that went into making it. Pretty amazing, really.

The Salar de Arizaro. Beats a wet January in the UK, that's for sure.

The Salar de Arizaro. Beats a wet January in the UK, that’s for sure.

And if you’re a student thinking about career options, spare a thought for chemical engineering. Our demand for metals is only going to increase and someone needs work on more efficient ways of getting at them. You won’t be short of a job, and you might even get to visit some pretty nice locations along the way.

Now funnily enough, and I swear I’m not just saying this for artistic licence, my laptop battery has just hit 7%. Where did I leave my charging cable…?

The Chronicle Flask’s festive chemistry quiz!

Tis the season to be jolly! And also for lots of blog posts and articles about the science of christmas, like this one, and this one, and this one, and even this one (which is from last year, but it’s jolly good).

But here’s the question: have you been paying attention? Well, have you? Time to find out with The Chronicle Flask’s festive quiz! I haven’t figured out how to make this interactive. You’ll have to, I don’t know, use a pen and paper or something.

Arbol_de_navidad_con_adornos_de_personajesQuestion 1)
Which scientist invented a chemical test that can be used to coat the inside of baubles with silver?
a) Bernhard Tollens
b) Karl Möbius
c) Emil Erlenmeyer

Question 2)
Reindeer eat moss which contains arachidonic acid… but why is that beneficial to them?
a) a laxative
b) an anti-freeze
c) a spider repellant

1280px-ChristmasCrackers_2Question 3)
Which chemical makes crackers and party poppers go crack?
a) gunpowder
b) silver fulminate
c) nitrogen triiodide

640px-Glass_of_champagneQuestion 4)
We all like a glass of champagne at this time of year, but what’s in the bubbles?
a) carbon dioxide
b) nitrogen
c) oxgyen

Question 5)
What’s the key ingredient in those lovely bath salts you bought for your grandma?
a) calcium carbonate
b) magnesium sulfate
c) citric acid

The Bird - 2007Question 6)
Which chemical reaction is responsible for both perfectly browned biscuits and crispy, golden turkey?
a) Maillard reaction
b) Hodge reaction
c) Caramel reaction

Question 7)
Sucrose-rodmodelWhere are you most likely to find this molecule at this time of year?
a) in a roast beef joint
b) in the wrapping paper
c) in the christmas cake

Question 8)
Let it snow, let it snow, let it snow… but which fact about (pure) water is true?
a) It glows when exposed to ultraviolet light
b) It expands as it freezes
c) It’s a good conductor of electricity

Ethanol-3D-ballsQuestion 9)
Where are you likely to find this molecule on New Year’s Eve?
a) in a champagne bottle
b) in the party poppers
c) in the ‘first foot’ coal

OperaSydney-Fuegos2006-342289398Question 10)
Who doesn’t love a firework or two on New Years Eve?  But which element is most commonly used to produce the colour green?
a) magnesium
b) sodium
c) barium

(Answers below…)

1a) Bernhard Tollens (but his science teacher was Karl Möbius).
2b) It’s a natural anti-freeze.
3b) Silver fulminate (it always surprises me how many people guess gunpowder. That would be exciting).
4a) carbon dioxide.
5b) magnesium sulfate which, funnily enough, also causes ‘hard’ water.
6a) the Maillard reaction, although Hodge did establish the mechanism.
7c) In the cake – it’s sucrose (table sugar).
8b) it expands as it freezes and is thus less dense than liquid water (which is why ice floats). We take this for granted, but most things contract (and become more dense) as they turn from liquid to solid. You should be grateful – live probably wouldn’t have evolved without this peculiar behaviour.
9a) In the champagne – it’s ethanol (or ‘alcohol’ in everyday parlance).
10c) barium – copper produces green flames too, but barium salts are more commonly used in fireworks.

So how did you do?
Less than 4: D, for deuterium. It’s heavy hydrogen and it’s used to slow things down. Enough said.
4-6: You get a C, by which I mean carbon. Have another slice of coal.
7-8: You’ve clearly been paying attention. B for boring, I mean boron.
9-10: Au-ren’t you clever? Chemistry champion!

Happy New Year everyone! 🙂

Any old ions?

The other day, thanks to an expedition to the swimming pool, I found myself drying my hair twice in one day. As I did so it occurred to me that the process was a lot faster at home with my old, battered hair dryer that it had been in the pool changing rooms.

I pondered variables (what can I say, I’m a scientist). I hadn’t washed my hair at the pool, I’d just rinsed it (hence the need to wash it again later) which meant no shampoo and, critically, no conditioner. Does conditioner’s presumably slightly hydrophobic nature help your hair to shrug off extra moisture? This didn’t seem like it ought to make that much difference. It seemed much more likely that the difference was simply due to the hair dryer itself.

hair-dryer

My battered old hair dryer.

And this got me thinking about the nature of my much-loved, rather battered, bright red hair dryer.

I’m going to ‘fess up here. I didn’t buy this hair dryer because I’d carefully researched its specifications and features and decided it was the best model for the job. No, if I’m honest I bought it because it was red and all the others were boring black and silver. Rational eh?

However, I do remember something about this particular hair dryer, and you can just about see a reference to this feature on the photo. Namely, it apparently contains an “ionic generator”. The little dial that you can see in the middle of the photo (set to orange, which if I recall correctly means, ‘maximum ions’) apparently adjusts the ion levels.

At the time I did try to find out exactly what the technology might be. I recall it was difficult – there didn’t seem to be much information out there – and since to be honest I didn’t care that much so long as it dried my hair, and it wasn’t particularly expensive (and it was red, RED!) I bought it anyway.

It only takes a quick glance at Amazon to see that the idea has not gone away. There are lots of ‘ionic’ hair dryers on the market, making claims such as, “Ionic conditioning with 90 per cent more ions“, “Heat-balancing ionic technology for condition and shine and a frizz-free finish“, “stylish dryer with ionic technology–seals in moisture to the hair cuticle for increased shine and silky, glossy hair” and the simple “4X More Ions“.

Hm.

Ok, well first of all what are ions? Whereas most people have a faint idea what atoms and molecules are, far fewer are confident to describe ions – despite the fact that they are firmly a part of the compulsory GCSE Science syllabus and were, of course, also included in  O-level Chemistry before that. Exactly why this should be is tricky to explain. Possibly it’s simply because ‘atoms’ and ‘molecules’ do occasionally crop up in everyday speech, whereas ions are that bit more obscure. Possibly it’s because children learn about atoms in the most basic terms quite early on, and come back to the idea regularly, but ions only turn up relatively briefly (unless, of course, you choose to study A-level Chemistry). There may be an element (hoho) of confusion over the fact that element 26 is called ‘iron’, which in most English accents sounds the same as ‘ion’. And just to really confound everyone, there are such things as iron ions.

But I think the most likely is that ions are a bit tricky to understand.

I’ll have a go.

Ions are charged particles.

There, that was easy, wasn’t it?

What do you mean, what does ‘charged’ mean? It means they have either a positive or negative charge.

What do you mean, ‘what does that mean’?

Oh all right. All right. Back to basics.

helium atom

A helium atom containing a tiny nucleus made up of two protons and two neutrons (red and blue), surrounded by an ‘electron cloud’. 1 fm = 0.0000000000010 millimetres.

First of all we need to understand a bit about atoms. Atoms are made up of two parts. There is the nucleus, which is made up of protons and neutrons (except for hydrogen’s nucleus, which is just a proton) and then, whizzing around that, are electrons. Electrons are quite fiddly things that behave frankly very oddly. In particular, they don’t actually drift around atoms in stately orbits as shown in most diagrams. In fact, they are sort of there and sort of not-there at the same time, and chemists talk about an ‘electron cloud’ as a result. An electron cloud need not contain lots of electrons (this depends on the size of the atom) – it just describes an area where you might find one or more electrons.

Anyway, that’s all a bit complicated and for our purposes it doesn’t really matter – all we need to know is that there’s a nucleus in the middle and electrons around it.

Electrons have a negative charge, protons have a positive charge, and neutrons have no charge. It’s quite difficult to rigorously define what I mean by ‘charge’ without getting into some tricky maths and physics. If you are ok with the idea of negative numbers (who hasn’t had an overdraft at some point or another?) then think of it like this: electrons are -1 and protons are +1 (and neutrons are 0). If you have one proton and one electron, the overall ‘balance’ is zero – their charges cancel each other out. In the case of helium, there are two protons and two electrons. This neat bit of balancing is no accident: it’s the case for all atoms. Carbon has 6 protons and 6 electrons. Oxygen has 8 protons and 8 electrons. Calcium has 20 protons and 20 electrons, and so on.

If the electrons and protons aren’t balanced for some reason (usually as a result of a chemical reaction) then the thing that you were calling an atom a moment ago stops being an atom and becomes, wait for it….

An ion!

Oxygen atoms have 8 protons and 8 electrons, but oxygen ions (properly called oxide ions) have 8 protons and 10 electrons. Which means they have a bit more minus than plus. They are, if you like, a bit overdrawn. If you add it up, you find the number works out as -2. And so we say that oxide ions have a charge of -2, and chemists (who are lazy) write this as O2-. Which is not, we must be careful here, the same thing as O2. That means two oxygen atoms joined together, to make an oxygen molecule. What do you mean it’s confusing?

One more example then. Calcium atoms have 20 protons and 20 electrons, but calcium ions have 20 protons and 18 electrons. Add that up and you get +2. We say that calcium ions have a charge of +2, and write Ca2+(and there’s no such thing as Ca2, so that’s one less thing to worry about).

Where have we got to? Ions are charged particles, and that means that they either have a positive charge or a negative charge. These charges are typically between 1 and 3, positive or negative.

mineral water label

Fizzy mineral water, chock full of lovely ions.

Ions are very important, because they form during chemical reactions and many everyday substances are made up of ions. For example table salt, sodium chloride, is made up of Cl ions and Na+ ions.

Tap water, and indeed bottled water, are full of ions. Tap water has chloride ions (chlorinated water is a jolly good thing, assuming you don’t want typhoid, and is definitely not harmful regardless of what your nearest quack might try and tell you). It might also have fluoride ions, which are also very good for your general health (again, there’s lots of nonsense spread about this). Both tap and mineral water usually contain some sodium ions and some calcium ions. The ion balance does affect the taste – the more sodium there is the more salty the water tastes, for example – but that’s about it really. The ions don’t give the water any special properties except, perhaps, the ability to conduct electricity (which pure water, as in just H2O, actually does really badly).

Having explained ions, let’s get back to hair dryers for a moment. Ionic hair dryers claim to produce streams of negatively-charged ions. They usually claim to use something like the mineral tourmaline to do this, but despite much searching I struggled to find out much about how this was supposed to work or, most crucially, what the negative ions actually are. Negative ions are not a thing in and of themselves. They must be ions formed from atoms, so which element? Or elements?

After much hunting I eventually came upon an interesting piece written by Andrew Alden, at about.com. He explains that tourmaline has an interesting trick called pyroelectricity, which means that it does become charged when heated. The ancient Greeks even knew about this: in 314 BC Theoprastus noticed that tourmaline (called lyngourion at the time) attracted sawdust and bits of straw when heated.

Ed Trollope, from Things We Don’t Know, helpfully explained this pyroelectric effect as follows: the crystal structure of tourmaline becomes polarised (in other words the charges already in the structure become unevenly distributed) if you change its temperature. This results in a voltage across the crystal, which in turn leads to a small current being generated.

But I’m still unclear what the ions, if they exist, actually are. And the problem is that if you search for this, the first umpteen links are all pure and utter nonsense. Tourmaline is a complicated mineral that contains a whole host of different metal ions as well as oxygen, OH (hydroxide) and fluorine. Does it produce oxide ions, O2-? These are very reactive and wouldn’t hang around for any useful length of time. And if they did they would surely be harmful. Presumably they would cause the production of ozone (definitely not a good thing). Are the manufacturers using the word ‘ions’ when they actually mean ‘electrons’? They are not the same thing of course, but perhaps ‘ions’ seemed like a friendlier word.

Electrons would reduce static in your hair, but then static is short-lived anyway. Would it speed up drying time? None of the explanations I’ve actually seen for this including, most memorably, “The negative ions break down water molecules to one-fifth of their size” (errrr, what?), provide a really satisfactory, scientific explanation as to why it should. Or why it should ‘seal water into the hair’, whatever that means. It is feasible that the reduction of static could help keep the hair strands separate, which might help, but surely brushing or even running your fingers through your hair would have a much bigger effect. What I’m also not clear on is whether the tourmaline in your hair dryer carries on producing streams of ions/electrons indefinitely, or whether it becomes degraded over time. Which you would expect, if the charged particles are coming from the tourmaline itself. Is my battered old hair dryer really doing anything at all anymore, if it ever did?

It’s all very unsatisfactory. My best guess? Ionic hair dryers do reduce static build-up in hair, which would leave it smoother immediately after drying. Conditioner and styling products will also help with this mind you, and will probably have a more significant effect. The rest, I strongly suspect, is pure woo. And my hair dryer dries my hair faster simply because it runs hotter and with a faster airflow than the cheap, basic models in the swimming pool changing rooms.

But if you know better, I’d genuinely love to hear from you.

Why weigh atoms that way?

A couple of days ago I was listening to the latest Radiolab podcast. If you’ve never listened to one of these, you really should. They are beautifully produced and, without fail, utterly fascinating. Over the last year or so I’ve learned about a possible cure for a disease with a 100% mortality rate, an apocryphal Russian story about horses frozen into a block of ice, and a new theory for the end of the dinosaurs where, if I understood it correctly, they were essentially grilled to death. Episodes of Radiolab always feel like a thoroughly good use of brain-time.

Anyway, if you’re still with me and haven’t dashed off to immediately download some of these little gems, the most recent episode is about weights and measures and how we’ve standardised them over the years. In particular the kilogram, which is the last physical standard in use, although possibly not for long (listen to the podcast).

shutterstock_27019597_Alhovik_mod_2

So what are the scales made of…?

This got me thinking about atoms and, in particular, how we decide their mass. This matters you see, because the mass of atoms tells us chemists how much stuff to use. If I want a saline solution with a particular concentration, all I need do is look up the numbers on the periodic table, weigh out the appropriate amount of salt and dilute it with the appropriate amount of water. And if you’re a patient who needs a saline drip, you’d better hope I did it correctly.

Anyway, if you remember your periodic table (which of course you do, but just in case, here’s a picture) all the elements come with two numbers.

The Periodic Table

One of these numbers is the atomic number, which is the number of protons in the nucleus of each atom of the element. Conveniently, nature has managed to produce an atomic nucleus for each number between 1 and, at last count, 118 and if you ‘read’ the periodic table from left to right, top to bottom, you’ll see the numbers go up one at a time.

The other number, relative atomic mass, is a bit less tidy. It still goes up as you go along the periodic table, but in less regular jumps of roughly between one and three.  Without going into lots of detail, relative atomic mass is standardised against 112 the mass of carbon-12. Which begs the question, why? The more mathematically aware will have clocked that 112 of 12 is, well, 1. So why don’t we compare all the elements to hydrogen, which actually has a mass of 1? Or if that’s infeasible for some reason why not, I don’t know, choose 19 of beryllium-9, or 128 of silicon-28?

Well actually, almost exactly 200 years ago now, atomic mass (called atomic weight, at the time) was originally compared to hydrogen, and it was thought that all elements would have masses which were exact multiples of hydrogen’s.

The problem with this was that as measuring techniques became more sophisticated it became clear that some elements were inconveniently failing to follow the rule. In fact, some were downright contrary, like chlorine which appeared to have a mass which wasn’t even a whole number.

This was, at least partially, sorted out in 1932 when James Chadwick proved the existence of neutrons. The existence of isotopes had already been suggested, but this finally cleared up what the pesky things actually were. It turns out some atoms are fatter than others, having one or two more uncharged particles in their nuclei. This doesn’t change what atom they are – they still have the same number of protons – but it does make them a bit heavier. Take a sample of pure chlorine, for example, and you find that roughly three quarters of the atoms in it have a mass of 35, whereas the other quarter have a mass of 37. These are the isotopes of chlorine: imaginatively named chlorine-35 and chlorine-37. Work out the weighted average of the two and you get 35.5, which is the number you see on periodic tables.

In the mid-20th century something of a minor squabble between chemists and physicists broke out (chemists and physicists often squabble: they’re a bit like the English and the French: they like to visit each other but only so that they can moan about how annoying the other lot are and how badly they do everything). By this time had been a switch from using hydrogen (the lightest element) to oxygen as the standard to which other elemental masses were compared. This was mainly for the convenience of chemical analysis: oxygen combines with a lot of things to make straightforward oxides, whereas hydrides are less common and trickier to work with. Plus, large quantities of hydrogen gas are a bit (in the sense of an elephant being a bit heavy, or cyanide being a bit poisonous) of an explosion risk. Oxygen causes other things to burn jolly nicely, but isn’t actually flammable itself. If you can manage to keep it away from other flammable stuff it’s a far safer option.

The problem was that chemists were using a mass scale based on assigning the number 16 to a natural mixture of oxygen (which contains mostly oxygen-16, with little bits of oxygen-17 and oxygen-18). Physicists, on the other hand, had instead assigned the number 16 to the isotope oxygen-16, which they had isolated using the technique of mass spectrometry.

Josef Mattauch

Physicist Josef Mattauch

You may think the physicists’ method sounds more logical, but the chemists’ reasoning was that in naturally-occurring compounds there would be a mixture of isotopes, so it made sense to use a number based on that mixture since you never actually encounter one atom on its own. Either way, the result was differences in the numbers, admittedly some way down the decimal places, but none the less a difference. Of course it was possible to convert between the two, but at the time scientists were fiddling with such tricksy things as nuclear energy and, of course, bombs. Even a tiny discrepancy in the nth decimal place was potentially catastrophic. Something had to be done.

Edward_Wichers

Chemist Edward Wichers

In 1961 a compromise was agreed, thanks largely to the combined efforts of the physicist Josef Mattauch and the chemist Edward Wichers, who set about persuading their respective groups to be reasonable and play nicely with each other.

The result was that carbon-12 was assigned a mass of exactly 12 and the relative atomic mass scale became based on that. The choice of carbon was, to an extent, somewhat arbitrary. It suited the physicists, who were already using carbon as a standard for mass spectrometry. It fell in between the two previous values (1 for hydrogen and 16 for oxygen), which meant it wouldn’t throw every existing piece of work out by too much. In particular, chemists weren’t keen on switching to the physicists’ method of 116 of the oxygen-16 isotope, because it would change their numbers quite significantly. Switching to 112 of carbon-12 meant, surprisingly, a smaller change. Carbon is also, of course, a naturally abundant element and it was easy to get samples of pure carbon.

And that, as they say, is that. The carbon-12 scale is still used today, over 50 years later, and it’s not going anywhere. Hydrogen is officially 112 the mass of carbon-12, and we use carbon-12 because, basically, it was the only option the chemists and physicists would agree on. Hey, it’s as good a reason as any.

Clever Chemistry Cupcakes

On Friday I had my last lesson with some lovely year 13 (upper sixth in old money) students who were about to go on study leave. They bought with them the rather fabulous cupcakes in the photos below. Now, I could talk about baking chemistry, but I’ve done that before so I won’t repeat myself. However as you can see they did a rather lovely job of icing. In fact I think they’ve gone above and beyond in covering a broad spectrum of chemistry. It’s really quite a nice revision aid. Perhaps eating the cake will somehow cause the information to be absorbed more effectively, who knows…

Chemistry cupcakes part 1...

Beats flash cards huh?

So in their honour, and just in case you can’t make any of the symbols out, I’m going to attempt to explain what each one is (by the way, links go to Chemguide, an excellent source if you need a bit of last-minute information):

From left to right:

But wait, there’s more!!

Chemistry cupcakes part 2...

Are you full yet?

Left to right again:

So there we go, aren’t they great?  Good luck to this lovely lot, and to all the other students out there about to tackle their final A2 exams. Wishing you all the best for the future! 🙂

Good luck!

Good luck!

Are you a Christmas chemist and you didn’t know it?

So Christmas has been and gone and we’re all forlornly looking at pine-needles around the tree and the mountainous pile of recycling in the kitchen, promising ourselves that we’ll eat nothing but salad come January first. But in the meantime, let’s take a bit of time out from the sales, watching Christmas telly and eating endless chocolates (I’m pretty sure anything eaten between December 24th-31st doesn’t count) and think about all the chemistry we’ve done over the last few days – yay!

Cracker snaps contain silver fulminate.

Cracker snaps contain silver fulminate.

Pulling crackers
Pulled a cracker over Christmas? Of course you have, and probably more than one. Did you wonder what caused the bang and the strangely appealing chemically smell? Of course you didn’t, but never fear, I shall tell you anyway. It was probably silver fulminate, AgCNO. This particular chemical is a primary explosive, but not a particularly useful one due to its extreme sensitivity. It’s so sensitive to any kind of shock (including the touch of a feather, a drop of water, or even just a particularly loud noise) that it’s completely impossible to collect more than the most minute amount without it blowing up unexpectedly. It was first prepared by Edward Charles Howard in 1800, who was working on preparing fulminates. None of them are stable, and one has to wonder if he had any eyebrows or eardrums by the time he’d finished. Anyway, silver fulminate has found one sort of practical use, and that’s in novelty snaps like the ones in crackers. There’s a tiny amount of silver fulminate on one piece of cardboard, and an abrasive on the other. When you pull, the two rub against each other and BANG! Paper hats, plastic toys and bad jokes abound. What happened after an explosion at a French cheese factory? All that was left was de brie.

Release the pressure and carbonic acid converts into water and carbon dioxide. Quickly.

Release the pressure and carbonic acid converts into water and carbon dioxide. Quickly.

Opening bottles of fizzy stuff
Most people are probably already vaguely aware that the bubbles are carbon dioxide, but there’s more to it than that, oh yes. Have you ever noticed that the liquid in the bottle looks completely bubble-less until you actually open it? If not, check next time. It’s really quite amazing. Why is this? Well, there’s a bit of chemistry going on. Brace yourself for an equation:

CO2 + H2O ⇌ H2CO3

There on the left you have carbon dioxide and water, and on the right something called carbonic acid. The double arrow thingy means the reaction is reversible, and the thing about reactions like this is that they will sit there quite happily, perfectly balanced, until something happens to change them. In the case of fizzy bottles, opening them will do that. It lets out the carbon dioxide and that causes the reaction to make yet more water and carbon dioxide in an attempt to compensate. That’s where all the bubbles come from, and it’s also why fizzy drinks taste peculiarly sweet if they’re left to go flat – like all acids (testing this is not recommended, but trust me) carbonic acid tastes sour and when it gets used up the sweetness due to sugars and sweeteners starts to take over. Contrary to popular belief, putting a spoon in the bottle will do absolutely nothing whatsoever to stop your champers from going flat. Sticking some kind of air-tight stopper in it, on the other hand, will definitely help.

The blue flame is due to complete combustion.

The blue flame is due to complete combustion.

Setting fire to the christmas pudding
Or rather, the generous splash of alcohol you’ve just poured on it. Have you noticed that the flame is a lovely blue colour, very different from the warm yellow of coal and candles? That’s because when you burn alcohol, specifically ethanol, CH3CH2OH, you get something called complete combustion. This happens when there’s enough oxygen to only produce carbon dioxide and water as products. Ethanol has an oxygen atom built in, so it burns more completely than hydrocarbon fuels like coal and candle wax, which tend to produce carbon atoms (also known as soot) and carbon monoxide as well. The reason the flame is blue rather than yellow is because that yellow colour is caused by carbon atoms getting so hot that they glow. By definition, in complete combustion there’s no carbon, so no yellow. Instead the gas molecules in the flame get so hot they start glowing instead, giving off blue light. All together now, oooooh!

Alpha-pinene gives christmas trees their smell.

Alpha-pinene gives christmas trees their smell.

Sniffing a Christmas tree
What is that lovely smell? Mostly a molecule called pinene, specifically alpha-pinene. It’s a funny-looking thing isn’t it? Looks a bit like a waiter rushing with a full drinks tray. Anyway, there are two forms of this molecule: alpha and beta.  Alpha is the most common one in nature, particularly in conifers (which Christmas trees are). Peculiarly, it somehow manages to be both an insect repellant while also, apparently, being used by insects as a chemical communication system. I don’t know how this works, ask an entomologist.

Christmas lights owe their glow to tungsten.

Christmas lights owe their glow to tungsten.

Switching on the Christmas lights
These days, LED lights are slowly taking over, but there are still enough filament bulbs kicking around in boxes of decorations that they’ll probably persist for a few years yet. Electricity consumption be dammed, they do make a much prettier glow. And why is that? It’s partially due to tungsten, element number 74. It has the highest melting point of all the elements (there’s a handy fact for your next trivia quiz) and as a result it is, or at least used to be, used to make the filament in incandescent light bulbs. Heat it up and it starts to glow long before it reaches its melting point of 3422 oC. The bulbs are also filled with an inert gas, usually krypton (nothing whatsoever to do with Superman, sorry), which stops the tungsten from reacting with the oxygen that would be present in ordinary air. In fact, filling a bulb with krypton makes it even brighter and longer-lasting than just pumping all the air out leaving a vacuum, because the krypton helps to disperse the heat.

So there you go, just a few of the many, many bits of chemistry you’ve done so far this Christmas. Enjoy the rest of the chocolates, have a happy New Year, and to those out there with January mock exams coming up, good luck!

So how do you spell element 16?

IUPAC says sulfur, and what they say goes

IUPAC says sulfur, and what they say goes

I found myself yet again discussing the correct spelling of the name of element number 16 today with a group of students. Now, on the one hand, going over this again and again is a tad wearisome. On the other, I’m quietly glad that in a time in which the media constantly blather on about terrible literacy levels, rant about the use of txt spk and generally mutter under their (or there/theyre/one of those) breath about the inability of the nation to use an apostrophe properly, I can consistently find an entire roomful of youngsters who care so much about spelling that they’re willing to argue over the correct use of ‘f’ vs. ‘ph’.

I am, of course, talking about sulfur.

You will note that I have spelled it with an ‘f’.  I should point out that the spelling chequer* on my browser has just underlined that with a row of red dots. It disagrees with me as well.

However, IUPAC (The International Union of Pure and Applied Chemistry – sounds like a fun place for a holiday doesn’t it?) do not, and in this they get the deciding vote. One of the many things IUPAC does is to sort out the official nomenclature of organic and inorganic molecules.

Of course, chemistry professors have been cheerfully ignoring them for years, and so it is that generations of chemistry students have tripped gaily into their first university session, fresh from A-level teachers using systematic names, to be immediately and thoroughly bamboozled by a lecturer talking about acetone, neopentane, para-nitrophenol and the gloriously-named glacial acetic acid.

But there it is, when it comes to element 16, IUPAC are crystal clear. It’s sulfur. With an f. That means it’s also sulfide with an f, and sulfate, with an f. Oh and sulfuric, as in the acid, with an f. Interestingly Richard Osman, on the BBC quiz show Pointless, has been very keen to point out in elements rounds that it’s sulfur, and then in a round about acids spelled it sulphuric. Weird.

In their notes, IUPAC even say that ‘”aluminum” and “cesium” are commonly used alternative spellings for “aluminium” and “caesium.”’ No such note is made for sulfur. Time to get over it.

Volcanic sulfur - it looks prettier than it smells.

Volcanic sulfur – it looks prettier than it smells.

If the Online Etymology Dictionary is to be believed, the ph/f thing has gone backwards and forwards a few times. It was apparently sulphur in Latin, and sulfur in Late Latin. There was an Old English word ‘swefl’ meaning sulfur or brimstone (same thing really, just with more religious connotations), and an Old French one: ‘soufre‘. Actually, according to Google Translate, that’s the modern French spelling as well. I am pretty clueless when it comes to French, so feel free to correct me.

The UK started spelling the word with a ph in around the 14th century, along with several other words that have since fallen out of use, such as phantastic and turph. The ph makes some sense in words with a Greek origin, such as philosophy and orphan, since the Greek alphabet actually has the letter phi, but little sense otherwise. However the scribes of the time believed that the more letters there were in a word the more impressive it would look, so they made everything as long and complicated as possible. Why use f when you can use ph? Why spell it ‘tho’ when you can write ‘though’? And you also have them to blame for all those annoyingly unnecessary double consonants that turn up far from occasionally (I absolutely never get that one right first time).

If we’re honest, this belief still persists to some extent. True we don’t throw extra letters in for good measure any more, but there are plenty of sesquipedalianist writers out there who believe such behaviour makes them look intelligent (see what I did there?) And just look at how annoyed people get about text speak, or how many quietly sneer about tweeting.

So back to element 16. Chuck in a few more centuries and we come, more or less, full circle. IUPAC adopted the spelling sulfur in 1990, and the Royal Society of Chemistry Nomenclature Committee followed suit in 1992. The Qualifications and Curriculum Authority for England and Wales switched in 2000, and it’s now the spelling you will see in both GCSE and A-level examinations and, consequently, the one in any text book published within the last decade. For those that complain it’s an American spelling, even The Oxford Dictionaries admit that “In chemistry… the -f- spelling is now the standard form in all related words in the field in both British and US contexts.”

So it’s sulfur. With an f. It’s not “the American spelling”. Well, ok, it IS, but it’s also the British spelling. And the rest of the world’s spelling. So add sulfur to your spell checker’s dictionary and let’s move along.

——

* this is a joke. Probably not a very good one, since a number of people have pointed out my ‘mistake’. It’s never a good sign if you have to explain your attempts at humour is it? Anyway, it’s a reference to this famous (well I thought it was, anyway) poem.

Liquid calcium? Why words really matter in chemistry

dl-265_1zI happened to see an advert for Arm & Hammer toothpaste on TV a couple of days ago, in which they cheerfully proclaimed that it contained “liquid calcium”.

navigator_highlighted_periodic_table

Calcium, on the left. With the metals.

This brought me up short.  First thing: calcium is a metal.  Now, as a famous British movie star might say (or perhaps might not say), “not many people know that”.  Ask a roomful of people if calcium is a metal and most of them will tell you it’s not.   I’ve even heard students who know what the periodic table is and what the position of elements within it means, and who can see calcium right there on the left hand side, express their doubts.  Everyone associates calcium with bones and teeth, possibly rocks at a push.  No one (other than chemists of course) hears ‘calcium’ and thinks of a silvery-grey metal.

But that is indeed what it is.  It is a metal, and although its melting point isn’t huge in the grand scheme of metals, it’s still a fairly substantial 842 oC.  The temperature in your bathroom is probably in the region of 20 oC.  In fact your kitchen oven probably only goes up to about 240 oC, so the melting point of calcium is some 600 oC hotter than the hottest setting on your oven.

ca_2_2

Calcium and water: what you can’t see is how hot this sucker is going to get.

Temperature problems aside, pure calcium is also highly reactive.  Drop some in water and you’ll see a lot of violent bubbling followed by the solution turning white as a corrosive calcium hydroxide solution forms.  The bubbling is due to flammable, potentially explosive, hydrogen gas.  Oh, and it will get really, really hot too – this is what chemists call an exothermic reaction.  I for one will confess to once (many, many years ago, of course) dropping a red-hot boiling tube into which I’d popped just a little too much calcium metal.  After it had also bubbled up and covered my hand with the aforementioned calcium hydroxide.  Ooopsie.  (Fear not, my hand survived unscathed, after the application of copious amounts of cold water – the go-to cure for most chemical exposures).

So, at the risk of stating the obvious, there’s no liquid calcium in Arm & Hammer toothpaste.  And a jolly good thing too.

What is there?  At this point I should probably point out that Arm & Hammer are quite careful, in their literature and on their packaging, to always put a little ™ by “Liquid Calcium”.  A quick glance at their website clarifies that they’re talking something called “Liquid Calcium ™ Technology” which refers to an ingredient that contains “up to 8 times more calcium and phosphate ions than the amount found in saliva so it is able to replenish ion content in your mouth and subsequently re-mineralise and protect your teeth more efficiently.”

Ah, now we get to the truth of the matter.  It’s not liquid calcium, but calcium ions in solution.

Does this matter?  Am I being unnecessarily pedantic?  Liquid/solution, calcium metal/calcium ions, what’s the difference?

H2O2

When an extra O really matters.

Well, the thing is, chemists are pedantic.  See, in chemistry, it genuinely could be a matter of life and death.  Ethanol, for example, is ‘drinking’ alcohol.  It’s the stuff in beer, and wine, and strawberry daiquiris.  It may not be exactly healthy, but most adults can consume some fairly safely.  Ethanal, on the other hand, is a toxic and probably carcinogenic substance that’s mainly used industrially as a starting point to make other chemicals.

To pick another example, chlorine is a highly toxic gas that’s been used in chemical warfare; chloride ions are found in salt and are consumed perfectly safely every day.  The difference between ions (atoms or molecules which have become charged due to the gain, or loss, of electrons) and atoms is really quite critical in chemistry, and in life in general.

potassium and water

Potassium reacting with water – pretty!

‘Everybody’ knows that bananas contain lots of potassium.  But potassium is another highly-reactive metal.  In fact it’s even more reactive than calcium.  Potassium explodes with a rather beautiful lilac flame in contact with water.  It’s pretty to watch, but you wouldn’t want it in your mouth.  Actually bananas contain potassium ions (and just to really mess with everything you thought you knew, not even that much compared to lots of other foods).

Back to the dubious labelling again, It’s interesting that Arm & Hammer have chosen to say “fluoride” – which specifically, and correctly, refers to fluoride ions – and not “liquid fluorine”.  I mean surely, in the spirit of consistency, it should be liquid fluorine and liquid calcium (argh!), or fluoride ions and calcium ions.

The word liquid has a specific meaning in chemistry.  It means a pure element or compound in its molten state.  Pure water at room temperature is a liquid.  So is ethanol, and mercury, and bromine (interestingly these last two are the only chemical elements which are liquids at room temperature).  Ethanol dissolved in water, as it is in strawberry daiquiris (more or less), isn’t a liquid.  It’s a solution.  This matters.  Liquid ethanol is pure ethanol.  Drink that and you’re looking serious alcohol poisoning in the face, and it’s about to wallop you for looking at it funny.

frustration_350px

An Arm & Hammer chemist?

Saying, or even implying, that calcium ions in solution is ‘liquid calcium’ is like saying that seawater is liquid sodium (sodium is another highly reactive metal – orange flame this time).  It’s just nonsense.  Ok, it’s probably not going to cause anyone any actual harm, but that’s not the point.  It’s completely factually inaccurate.  I am absolutely certain that the chemists working for Arm & Hammer wanted to tear their hair out when the advertising company came up with this name for the formulation they’d spent (probably) years slaving over.  And I expect they were essentially told to shut up about it, the vast majority of our customers won’t know the difference.

And sadly this may be true.  But it shouldn’t be.  Would Arm & Hammer care if their boxes were labelled ‘tothpast’ instead of toothpaste?  I bet they’d be bothered if the boxes were priced at £250 instead of £2.50.  Why fuss over spelling and numbers but be careless over scientific literacy?  Either precision matters or it doesn’t.

Perhaps it’s time scientists starting making as much noise about this kind of thing as people who complain about stray apostrophes or the misuse of the word disinterest.  You never know, it might help levels of scientific understanding.

Mind you, perhaps the author of a blog called The Chronicle Flask shouldn’t throw stones…

—-

After I wrote this post I tweeted something referring to “liquid phosphorous”.  It was pointed out to me, quite rightly, that I meant “liquid phosphorus”.  Phosphorus is the noun – the name of the chemical element – and phosphorous is an adjective.  As in, “phosphorous fertiliser”.  I confess I was a bit hazy on that one until made to check, which is ironic really. Consider me sent to the back of the class 😉

Gold! Bright and yellow, hard and cold

200px-Gold-49956Let’s talk about element number 79.  It’s one of the oldest known elements, used for quite literally thousands of years.  It’s constantly at the heart of conflicts and politics.  Poets have waxed lyrical about it, authors have written about it, economists and prospectors have hinged their livelihoods on it.  And, of course, chemists have studied it.

As an element it’s unusual.  It’s a metal, but instead of the boring silvery-grey of most metals it glows a warm yellow.  It’s also one of the most unreactive elements, and yet has found use a catalyst – speeding up chemical reactions that otherwise would be too slow to be useful.  It’s rare, making up only about 0.004 parts per million of the Earth’s crust, and yet its annual production is surprisingly high: 2700 tonnes in 2012.  Its density makes it heavy – weighing over nineteen times more than the same volume of water – but it’s also relatively soft, so soft that it’s possible to scratch a pure piece with your fingernail (in theory, and if you have fairly robust fingernails).

Yes, gold.  Chemical symbol Au, from its latin name aurum meaning ‘shining dawn’ or ‘glow of sunrise’ (how lovely is that?)

The history of gold is fascinating.  You could easily write a whole book about it.  In fact, someone has.  I won’t attempt anything so ambitious, but it does have some very interesting chemical stories associated with it.

Because of its unreactivity, gold is one of the relatively few elements that’s found uncombined in nature.  In other words, you can pick up a piece of pure gold from the ground or, more likely, out of a river bed.  Thanks to this property it’s very probably the first metal that humans as a species interacted with.  It’s too soft to be much use as a tool, so its earliest uses were almost certainly ornamental.  Decorations and jewellery had value and could be traded for other things, and ultimately (skipping over a chunk of history and early economics) this led to currency.

And so it was that early alchemists, some two thousand years ago, became obsessed with the idea of a quick buck.  Could other metals be turned into gold?  They searched long and hard for the mythical philosopher’s stone (like in Harry Potter, only not exactly) which could turn base metals into gold or silver.  Of course they never found it, because it doesn’t exist.  It’s not possible to change one element into another during a chemical reaction.  This is because what defines an element is the number of protons in its nucleus, and chemistry is all about the electrons. Chemical processes don’t touch protons, which are hidden away in the nuclei of atoms.

But where there’s a will there’s almost always a way.  Two millennia after alchemists were hunting for a magical stone, the chemist Glenn Seaborg managed to transmute a minute quantity of lead, via bismuth, into gold by bombarding it with high-energy particles.  Apparently, these days particle accelerators ‘routinely’ transmute elements, albeit only a few atoms at a time.

The trouble is, this method costs a fortune – way, way more than the value of any gold produced.  Gold, after all, is ‘only’ worth about a thousand pounds for a troy ounce (31 grams).  Particle accelerators cost billions of pounds to build, and yet more in running costs.  If you really want gold so desperately, these days there may be more mileage in harvesting it from defunct bits of electronic equipment.

Or just ask people to send you their old jewellery through the post in exchange for cash.  Even Tesco have got into that game now.  Through the post!  Honestly, people fear putting a tenner in a birthday card but gold jewellery in a paper bag?  No problem.

But anyway, back to gold’s reactivity, or rather lack of it.  Gold isn’t the most unreactive element (depending on how you’re defining reactivity, that honour probably goes to iridium) but it’s up there.  Or perhaps I should say down there.  It keeps its shiny good looks even when it’s regularly in contact with warm, damp, salty, slightly acidic skin, which is quite handy from the jewellery and money point of view.

But there is one thing gold reacts with: aqua regia.  Aqua regia is a mixture of nitric and hydrochloric acid and ancient alchemists gave it its name – which literally means ‘royal water’ – because it dissolves the ‘royal’ metal, gold.  It’s pretty cool stuff, in a slightly scary way.  Freshly-prepared it’s colourless, but quickly turns into a fuming, reddish solution.  It doesn’t keep – the hydrochloric and nitric acids effectively attack each other in a series of chemical reactions which ultimately result in the production of nitrogen dioxide, accounting for the orange colour and nasty fumes. Screen Shot 2013-06-04 at 00.20.27The fire diamond (remember those?) for aqua regia has a 3 in the blue box, putting it on a nastiness par with pure chlorine, ammonia and, funnily enough, oxalic acid (the stuff in rhubarb).  It also has ‘ox’ in the white box, telling us it’s a powerful oxidising agent, which means it’s effectively an electron thief.

All atoms contain electrons but they can, and frequently do, lose or gain them during the course of chemical reactions.  Acids in general are often quite good at pinching electrons from metals, but aqua regia is particularly good at it, and especially with gold.  Much, much better than either nitric acid or hydrochloric acid on their own because, in fact, the two work together, as a sort of two-man gang of acid muggers.  When metal atoms lose electrons they become ions, and ions dissolve very nicely in water.  Hence, aqua regia’s fantastic property of being able to dissolve gold.

Which leads me to a really great story.  During World War II it was illegal to take gold out of Germany, but two Nobel laureates – Max von Laue, who strongly opposed the National Socialists, and James Franck, who was Jewish – discretely sent their 23-karat, solid gold Nobel prize medals to Niels Bohr’s Institute of Theoretical Physics in Copenhagen for protection.  All well and good, until the Nazis invaded Denmark in 1940.  Now, unfortunately, the evidence of von Laue and Franck’s crime was sitting on a shelf in a lab, just waiting to be found.  This was serious: if the Gestapo found the gold medals they would persecute von Laue and Franck, and probably take the opportunity to make things very unpleasant for Bohr as well, particularly since his institute had protected and supported Jewish scientists for years.

Nobel_PrizeWhat to do?  At the time a Hungarian chemist called George de Hevesy was working at the institute, and it was he that had the bright idea of dissolving the medals in aqua regia.

It would have taken ages, because although aqua regia dissolves gold, it doesn’t do it quickly, and these were chunky objects.  He must have been anxiously looking over his shoulder the whole time.  But he managed it, and eventually ended up with a flask of orange liquid that he stashed on a high shelf.  The Nazis searched the building but didn’t realise what the flask was, so they left it.  Iit stayed there undisturbed for years, in fact until after the war was over.  At which time, de Hevesy precipitated the gold back out and sent the metal back to the Swedish Academy, who recast the prizes  and re-presented them to Franck and von Laue.

So there we have it, you can’t turn lead into gold (at least, not without a particle accelerator) but, if you know what you’re doing, you might just be able to turn a flask of orange liquid into two solid gold Nobel prize medals!

———–

The title of this post comes from a poem by the British poet, Thomas Hood, 1799-1845. Here it is in full:

Gold!
Gold! Gold! Gold! Gold!
Bright and yellow, hard and cold
Molten, graven, hammered and rolled,
Heavy to get and light to hold,
Hoarded, bartered, bought and sold,
Stolen, borrowed, squandered, doled,
Spurned by young, but hung by old
To the verge of a church yard mold;
Price of many a crime untold.
Gold! Gold! Gold! Gold!
Good or bad a thousand fold!
How widely it agencies vary,
To save – to ruin – to curse – to bless –
As even its minted coins express :
Now stamped with the image of Queen Bess,
And now of a bloody Mary.

Chemical conundrums: #whichelement

Recently a group of us started playing a game of #whichelement on Twitter. Yes I realise this is quite geeky but, hey, at least it’s not #YouDontKnowBeliebersTheMovie or #jeremykyle (if you think those sound more interesting, at the risk of alienating a reader you’re probably reading the wrong blog…)table

Not-really-coincidentally I have also recently become co-admin of a page on Facebook called Brain Teasers, Illusions and Fun (come along if you like puzzles in general).

So here’s a little tie-in; can identify the elements from the clues below? Feel free to post answers in comments. I’ll post my list of answers in a couple of days.

Which element…

  1. Has a clump of earth, or possibly an unpleasant person, in its name?
  2. Is not very entrepreneurial? (thanks @slhyde!)
  3. Is like a bicycle with no audible warning? (thanks @RobSomme!)
  4. Had a place named after it? (this one’s general knowledge)
  5. Has a policeman in its name?
  6. Has a medical test in its name?
  7. Contains a musical instrument?
  8. Sounds like it might drone a bit?
  9. Has a chicken in its name?
  10. Sounds like something a phishing email is trying to get you to fall for?
  11. Has a name that literally means ‘smell’? (more general knowledge)
  12. Could be something you use to take your dog for a walk?
  13. Is an anagram of livers?
  14. Has a bottom in its name?
  15. Has a name that sounds a lot like a famously smelly plant?
  16. Might be described as ‘container donkey ium’
  17. Has a very silly person in it?
  18. Are hayfever sufferers most worried about? (thanks @hullodave!)
  19. Might be a source of amateur dramatics?
  20. Has a name that means goblin? (general knowledge again)