Today, from 6:02 AM to 6:02 PM, 10-23, was National Mole Day. Chemistry teachers today celebrated the Mole, the gram-molecular weight, the amount of substance in grams numerically equal to the molecular weight of a substance. I.e, the atomic weight of hydrogen is 1 so 1 gram of hydrogen is a mole. The molecular weight of the paired hydrogen molecule is 2, so a mole of molecular hydrogen (H2) is 2 grams.

A mole of any substance always contains 6.02 x 10^23 molecules, AKA Avogadro's number. A mole of any gas will always contain Avogadro's number of molecules, and at standard temperature and pressure will always occupy 22.4 liters of volume.

These facts were established by simple experiments which can be conducted with the equipment of the high school laboratory, or even of a well-equipped kitchen. and which are often repeated by high school students as part of their studies in elementary chemistry. With the conceptual tools yielded by these experiments, we have been able to not only prove the existence of atoms and molecules, but their relative weights, and how they combine to form compounds. We have also been able to identify many of those elements and compounds, tiny entities otherwise invisible to us, now as real and as concrete as anything in our everyday experience. On this basis, a science of profound complexity and elegance has evolved which has allowed us to create a dazzling array of useful products and to probe the fundamental nature of matter, life, and even evolution itself.

Let's raise our cups to Amedeo Avogadro (1776-1856) and his moles.