October 23 is National Mole Day

National Mole Day is not a time to pay tribute to cute furry diggers, secret agents, Mexican sauces, freckles or skin tags. (By the way, you really ought to have that thing checked out.)

Once a year on October 23 from 6:02 a.m. to 6:02 p.m., National Mole Day celebrates Avogadro’s Number (6.02 x 1023), a unit of measurement in chemistry. Mole Day originated in an article from The Science Teacher in the early 1980s. Inspired by the article, a chemistry teacher in Wisconsin created the National Mole Day Foundation on May 15, 1991.

In 1811, Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto—Amadeo Carlo Avogadro to his parents—proposed a law stating that equal volume of all gasses, at the same temperature and pressure, have the same number of molecules.

Avogadro contradicted better-known scientists of his time, didn’t publish his work in highly regarded journals and hailed from Italy, which had fallen out of favor as a site of scientific innovation. It took almost a hundred years for the scientific community to catch on. Chemist and Nobel laureate Jean Baptiste Perrin proposed in 1909 that the total number of particles contained in one mole be called the Avogadro Constant.

6.02×10^23

One mole is a mass (in grams) whose number is equal to the molar mass of the molecule. Because atoms are so small, they can only be measured in enormous numbers, on the scale of Avogadro’s number.

1 Mole = ∼ 602,200,000,000,000,000,000,000

It ‘s hard to imagine such a large number. Oklahoma State University has some useful analogies to help envision it:

• Astronomers estimate that there is a mole (6.02 x 10²³) of stars in the universe.
• Water flows over Niagara Falls at about 650,000 kL (172,500,000 gallons) per minute. It would take 134,000 years for one mole of water drops to flow over Niagara Falls.
• One mole of marbles, each 2 cm in diameter, would form a mountain 116 times higher than Mount Everest. The base of the marble mountain would be slightly larger than the area of the USA.

National Mole Day has always been about fostering interest in chemistry. It has been celebrated by teachers, students and schools for decades and inspires participants to create activities, thought experiments and even music videos to make learning about Avogadro’s Number fun.