When Water Does Not Boil at the Boiling Point

18 March 2010, United Kingdom

Introduction

We all learn at school that pure water always boils at 100°C (212°F), under normal atmospheric pressure. Like surprisingly many things that "everybody knows", this is a myth. We ought to stop perpetuating this myth in schools and universities and in everyday life: not only is it incorrect, but it also conveys misleading ideas about the nature of scientific knowledge. And unlike some other myths, it does not serve sufficiently useful functions. There are actually all sorts of variations in the boiling temperature of water. For example, there are differences of several degrees depending on the material of the container in which the boiling takes place. And removing dissolved air from water can easily raise its boiling temperature by about 10 degrees centigrade. The fickleness of the boiling point is something that was once widely known among scientists. It is quite easy to verify, as I have learned in the simple experiments that I will show. And it is still known by some of today's experts. So actually the strange thing is: why don't we all hear about it? Not only that, but why do most of us believe the opposite of what is the case, and maintain it with such confidence? How has a clear falsehood become scientific common sense?

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