October 23 - National Mole Day

Posted on October 23, 2021

Key points

This is an update of my post published on October 23, 2010:

This is NOT a holiday to honor the digging mammal called a mole!

Instead, it is a day commemorating Avogadro’s Number, which is a basic measuring unit in chemistry.

Actually, just PART of the day is Mole Day. From 6:02 a.m. to 6:02 p.m., on 10-23, we celebrate this chemistry commemoration. That’s because Avogadro’s Number is 6.02 x 10^23.

Amedeo Avogadro was an Italian
scientist who lived from 1776 to 1856.

For any molecule, one mole is a mass in grams whose number is equal to the atomic mass of the molecule. For example, a water molecule (H2O) has an atomic mass of 18. So one mole of water weighs 18 grams.

In general, one mole of any substance contains Avogadro’s Number of molecules or atoms of that substance. Another way of saying that is that 18 grams of water has 6.02 x 10^23 molecules of water.

Learn about Mole Day, Avogadro’s Number / moles, and chemistry!

Here is the official Mole Day site, and here is a “Happy Mole Day” song! (I think the song is pretty darned funny—check it out!)

Mole is just a word that stands for a number. (Granted, it’s a pretty ginormous number!) It’s a one-syllable word for a number that is used a lot by chemists, and the word is there so that chemists can easily refer to the number.

In other words, instead of saying “six point zero two times ten to the twenty-third power,” chemists just say “mole.” If you want to see a more complete explanation, go here.