jon edwards

My favourite chemistry things

I’ve been tagged! A fun blog meme for the day has been thrown my way by science writer David Bradley of sciencebase fame. His post can be found here. It started a few iterations ago so I can’t guarantee all mine will be original, but I do promise to back up my choices with video evidence that these things are amazing. Except one. But that one’s good enough, and quantum-level videos are… difficult.

Luminescence

I think the idea that light can come from chemical reactions is just fantastic, and the results are sometimes stunning. I spent the better part of a year analysing what light came off a pyrrole molecule I battered into submission with a couple of laser pulses, but here I’m talking more macroscopic. This video is simply fascinating, and beautiful, and it’s all chemistry.

The Incredible Hulk reaction

I include this because I was shown it for the first time only today, it made me go “wow”, and a colleague gave it a brilliant name. The cobalt chloride-catalysed reduction of hydrogen peroxide by Rochelle salt solution, while interesting, was too long to fit in a text field for a website. On hearing a description of the reaction, my witty and astute colleague Katie noted the reactants went from a pleasant light pink to an angry, frothy dark green, then back to pink as the reaction ended - rather like the Hulk. If an picture speaks a thousand words, a video speaks a million; and, in this case, they’re all “Don’t make me reduce. You wouldn’t like me when I’m reducing.”

Vacuum

Perhaps this doesn’t count; it could be better described as the lack of chemistry. Pedants can write to jon@idontcareitsfun.com.

For my final year of my chemistry degree, my MChem project comprised: 5% chemistry, 5% computer programming, 10% cleaning, 15% aligning laser beams, 20% engineering, and 45% bolting metal tubes together as hard as we could. Arguably those final two elements are the same. The incessant bolting was to make a seal on our collision chamber good enough to bring the pressure down to about 10^-9 psi, so when our miniscule amounts of injected gas were flying through, they wouldn’t crash into anything. Or, when our precisely-aligned laser beams were winging their way in, they wouldn’t excite any molecules they shouldn’t have. Those laser beams, they ain’t picky about who they excite. Pump ‘em and dump ‘em, as we say in the chemical physics community.

Anyway, the concept of nothing is almost as cool as everything else in the universe (which would make it the least cool thing in the universe. Pedants, write to the usual address). An example of the nature of the absence of stuff, and incidentally the physical structure of marshmallow, can be seen in the next video.

Hot ice (super-saturated sodium acetate solution)

This is a heart-warming, or at least hand-warming, bit of chemistry. The crystallisation of super-saturated sodium acetate is exothermic, and is what they use in little clicky handwarmers. Chemists who’ve ever had time and sodium acetate to hand will know it’s better used for making excellent sculptures, as seen in this video.

The Pauli Exclusion Principle

Perhaps an odd final choice but there’s something amazing about this: it applies on a quantum scale, obviously, but also in the real world. My wonderful A-level chemistry teacher Dr Ann Lewis Kell of Gorseinon College, Swansea, explained this concept in an easy-to-grasp way. The Pauli Exclusion Principle applies on trains.

The first person on a train picks a seat. They sit in the most comfortable seat they can, where they’re least likely to be asked to leave. The next picks another seat, and so on until all double seats have one person on them. Then and only then do people start occupying half-occupied orbitals. Sorry, I mean seats. Even better, when a seat is vacated entirely, people will often leave their full seat to occupy an empty one. Electrons value their personal space in much the same way.

So there I was, 17 and wide-eyed, being told people would not sit on top of me in a train because it was impossible for us to have the same quantum states. I had assumed it was my teenage repulsion forcefield, or the Megadeth blaring from the headphones.

The Exclusion Principle is a beautiful aspect of quantum theory. I’m told the maths are interesting, too, but my tiny chemist mind cannot comprehend such things.

There we have it: five of my favourite chemistry things. I’d tag some people if anyone read my blog, but they don’t, so it’s a bit pointless. I would suggest that some of my chemistry-liking Twitter followers take up the case though: I’m looking at you, @_MisterG, @Rutherfordium, and @NeilWithers.