I’m sure no-one needs reminding, but today is National Mole Day. . Nothing to do with small furry garden-diggers, although this year’s mascot might indeed be one the famous Sherlock Molmes.

Rather it’s a celebration of all things Avagadro’s Constant from 6.02am through 6.02pm every October 23rd.

Avagadro’s constant is 6.02 x 10^23 and thus on the date Americans call 10/23 at 6:02 it needs commemorating.

For anyone who forgot chemistry, per Wikipedia it’s useful as a kind of conversion factor:

The Avogadro constant is also the factor that converts the average mass of one particle, in grams, to the molar mass of the substance, in grams per mole (g/mol)

That’s to say, given that a water molecule has a molar mass of 18 - the oxygen provides an atomic weight of 16, and each of the two hydrogen molecules contribute 1 extra - we define one mole of water as the amount of water that has a mass of 18 grams. And to end up with 18 grams of water you need lots of water molecules, more specifically 6.02 x 10^23 of them.

In the same way if you wanted 16 grams of oxygen, you’d need to find 6.02 x 10^23 molecules of it, and so on.