On this fine day for a beer, we offer you a simple experiment – a bar trick, really – demonstrated by the great 19th century scientist Michael Faraday in his 1859 Christmas Lectures at the Royal Institution in London:
Is it not a glorious thing for us to look at the sea, the rivers, and so forth, and to know that this same body in the northern regions is all solid ice and icebergs, while here, in a warmer climate, it has its attraction of cohesion so much diminished as to be liquid water? Well, in diminishing this force of attraction between the particles of ice, we made use of another force, namely, that of heat; and I want you now to understand that this force of heat is always concerned when water passes from the solid to the liquid state. If I melt ice in other ways I can not do without heat (for we have the means of making ice liquid without heat - that is to say, without using heat as a direct cause)…
…I remember once, when I was a boy, hearing of a trick in a country ale-house: the point was how to melt ice in a quart pot by the fire and freeze it to the stool. Well, the way they did it was this: they put some pounded ice in a pewter pot, and added some salt to it, and the consequence was that when the salt was mixed with it, the ice in the pot melted (they did not tell me any thing about the salt and they set the pot by the fire, just to make the result more mysterious), and in a short time the pot and the stool were frozen together, as we shall very shortly find it to be the case here, and all because salt has the power of lessening the attraction between the particles of ice. Here you see the tin dish is frozen to the board; I can even lift the little stool up by it.
This experiment can not, I think, fail to impress upon your minds the fact that whenever a solid body loses some of that force of attraction by means of which it remains solid, heat is absorbed; and if, on the other hand, we convert a liquid into a solid, e. g., water into ice, a corresponding amount of heat is given out.
Operating on the same principle as those old hand-cranked ice cream makers, this little trick – performed just as easily with a metal bar shaker and a wet coaster – is hardly revolutionary. But like most feats of the ordinary, it is (by many orders of magnitude) far, far more mind-blowing when performed at your local drinking establishment.
Of course, this lesson in heat exchange was only a small part of Faraday’s series lectures that year on the forces of matter. That series of lectures was just one of many; Faraday gave 19 Christmas Lectures in all, most famously “The Chemical History of a Candle” in 1860. It was Faraday who established the youth-oriented Christmas Lectures – a tradition that lives on at the Royal Institute nearly 200 years later – in 1825. And these lectures are a mere fraction of his legacy. Faraday’s work in chemistry, optics, and most importantly the relationship between electricity and magnetism, has had enduring impact.
Michael Faraday – pillar of science, inquisitive, serious-minded, and tireless in his work – was born on this day in 1791. Is it fitting that we honor him with a centuries-old bar trick? Perhaps not…but hey, he’s the one who suggested it. Our only suggestion is that you wash it down with a beer – preferably one purchased for you by the crowd of amazed onlookers. (Rather easily amazed, don’t you think? All hail this voodoo known as science.)
