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The Modern Alchemist does show and tell

Peter Wothers explains one of the experiments that forms part of his Royal Institution Christmas Lectures.

I started to have a passion for chemistry when I was about eight years old and was given my first chemistry set. From that moment, I was absolutely hooked. I was given another chemistry set and then another and, during high school, I managed to get a parttime job at a laboratory supplier. Rather than money, it paid me in chemicals and equipment.

I bought textbook after textbook. I think what I was most obsessed with (aside from blowing things up) was the idea that I could demonstrate what I was reading in the books. I could show with experiments that water was made from two hydrogen atoms and one oxygen atom or how to extract copper from mineral ores.

My chemistry set has grown a lot larger since then and so has my passion for loud bangs and fiery explosions. For more than 15 years, I have been giving lectures as part of the Cambridge Science Festival and this, along with the other lectures that I deliver around the world, has given me the chance to focus on developing the best, the clearest and the most dramatic demonstrations possible.

When the opportunity to give the Royal Institution Christmas Lectures arose, I was thrilled by the prospect of sharing some of these finely honed demos and trying some that were bigger and more dangerous than I had ever done before. The unique thing about giving the Christmas Lectures is that you must think of demonstrations that could captivate the millions of people watching at home as well as those in the lecture theatre.

The storyline is important, too, so we developed an enchanting theme around the concept of a modern alchemist. The old alchemists were mysterious and magical but they never revealed their secrets. We’ve captured that spirit and intend to inspire awe and wonder.

Sometimes, even just a very simple demonstration is sufficient. For instance, how do we know that some atoms are heavier than others? And how can we show it? For the Christmas Lectures, we have developed an easy, elegant experiment comparing the densities of the noble gases by putting them in balloons that hold equal amounts of each gas.

The heavier gases sink quickly to the floor – direct evidence of the relative weight of the atoms, as each balloon contains pretty much the same number of atoms.

Bolt from the blue

The nitrogen cycle is a topic that is commonly taught at school but students rarely get any direct experience of nitrogen, other than the 78 per cent they are taking in with every breath. Experiences such as seeing liquid nitrogen at -196°C instantly freeze a flower so that it shatters like glass are all too rare for young people these days. In the Christmas Lectures, we’ve included many spectacular demonstrations using nitrogen, from fixing it in nitroglycerine (and then releasing it explosively) to a breathtaking situation in which I create lightning in the lecture theatre to combine nitrogen and oxygen from the air.

Seeing these demonstrations and experiments, either in person or on television, provides an unparalleled experience of the power and scope of science. I hope that by sharing some of my favourite demonstrations, I can provide evidence not only of my passion for chemistry but also of the ability of science to transform and shape our world.

Peter Wothers is a teaching fellow in the department of chemistry, University of Cambridge. He will present the Royal Institution’s 2012 Christmas Lectures, entitled “The Modern Alchemist”, which will be broadcast on BBC Four at 8pm on 26, 27 and 28 December

This article first appeared in the 24 December 2012 issue of the New Statesman, Brian Cox and Robin Ince guest edit