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Can we teach chemistry with explosions alone?

By Oli Usher, on 20 February 2015

Professor Andrea Sella (UCL Chemistry)

Professor Andrea Sella (UCL Chemistry)

Explosions, eruptions and exothermic reactions are the backbone of chemistry demonstrations. Generations of kids have been wowed by them.

But do they really learn much from it?

Professor Andrea Sella (UCL Chemistry) is a major purveyor of these explosions at science festivals and shows around the country. (He is also the only person I know who, when asked to sign off a risk assessment form full of apparently irresponsible pyrotechnics, was able to truthfully reply: “I make 7 foot fire tornadoes all the time, I’m sure it’s fine.”)

Having won the Royal Society Michael Faraday Prize for his explosion-based science outreach, Sella used the opportunity of his celebratory public lecture (‘Is chemistry really so difficult?’, 9 February) to make a plea for… well, not the complete elimination of explosions from public lectures, but more thoughtful and judicious use of them.

But first: one last opportunity to “blow sh*t up”, in this case, a can of hydrogen. Cue laughter and applause.

Back on track. For centuries, chemists have tried to impress people by blowing things up, he says, but this gives a false impression of what chemistry is really about. It suggests that it’s exciting, and that it’s dangerous. It wows the crowds, but from a scientific perspective it’s not actually all that interesting. Flashes and bangs are chemistry porn, and they undermine recognition of modern chemistry as one of the towering intellectual achievements of our time.

Chemistry becomes, at worst, something dangerous and irresponsible, or at best, boring and worthy – plastics, fertilisers, medicines etc. When in fact, chemistry lies at the heart of our understanding of the world around us.

So what’s the solution? Sella says we need to resist the urge to ‘shock and awe’ with flashy demonstrations, but instead to do what astronomers and physicists have done, and to talk in terms of the big, fundamental and inspiring questions addressed by science. Chemistry needs to capture the sense of awe that Brian Cox – a previous Faraday Prize winner – brings to astrophysics.

Where is this awe-inspiring chemistry? Sella says that it’s in the processes of chemistry, not in the end results.

Don’t look at the results of mixing chemicals, but in the processes of their reactions. The end results of chemical reactions in chemistry demonstrations are boring – whether it’s heat and smoke from an explosion, or phenolphthalein turning pink in titration experiments. They’re the static results of chemistry reaching equilibrium.

Forget equilibrium, he suggests, and look instead at feedback mechanisms, and the way complex behaviours can emerge from simple chemical mixtures.

He demonstrates this with a bizarre jar of chemicals which periodically changes colour from red to blue as the relative concentrations of different chemicals in it change – a process similar to what creates the concentric rings of candy-striped beetroot.

Complex patterns can emerge spontaneously from nowhere, without there being a design, thanks to the simple laws of chemistry following their course.

Chemistry can be a bridge between the animate and inanimate world.

It can even tell us about the emergence of life on Earth.

And it’s the job of chemists to unravel all of these processes, Sella says, so the rest of us know what we’re missing.

And if we want explosions? Well, we can still have a few of them – for they are chemistry too – but only a few. And they should be good ones, like the nitric oxide and carbon disulfide he ignites just before finishing off.

And with a deafening roar, and a huge blue flame, the lecture is over and he leaves the stage.

Watch the lecture:

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