There are about 20 species of fuzzy moles (the kind that crawl around on the ground), and one kind of mole that might appear on your face, but today is a day for celebrating a different kind of mole. Today’s mole is a unit — one invented by a man named Avogadro.

Really, a mole is just a group of objects. You can think of “a mole” the same way you think of “a dozen.” You’re probably familiar with a dozen eggs, or chickens or planets. Moles are no different. You can have a mole of molecules or people or cheeseburgers. But there are a lot more than twelve things in a mole — there are 6.02 x 1023. That’s 602,000,000,000,000,000,000,000 things. Because the mole contains so many units, they’re most often used in chemistry is a way of measuring really really small things like atoms or molecules.

So a mole of water is 6.02 x 1023 molecules of water, which works out to be about 18 grams, or 18 mL. A mole of aluminum is about 26 grams. But to really appreciate how many molecules are in a mole it helps to think about things we can see. To do that, let’s try these comparisons from Daniel Dulek’s lesson about how big a mole is.

A way to think about the relative size of a mole?

If you had a mole of doughnuts, they would cover the entire Earth in a doughnut-layer five miles deep.

If you had a mole of basketballs, you could create a new planet the size of the Earth!

If you received a mole of pennies on the day you were born, and spent a million dollars a second until you died at 100, you’d still have over 99.99% of your money in the bank.

One mole of red blood cells is more red blood cells than exist in every human on earth right now. A mole of cereal boxes stacked end to end would reach from the Sun to Pluto 7.5 million times. A mole of turkeys could form sixteen earths.

Okay, so now that we know why a mole has 6.02 x 1023 things in it, what can we do with that information? Moles in chemistry are far more useful than moles in the ground, or on your face. They factor into all kinds of equations and important concepts in chemistry. Chemists think of moles or atoms like you and I think of a dozen eggs – we add them to recipes, order them from the store and calculate what we need based on how many we have.

What would a mole of fuzzy moles look like? Well, the pile of animals would weigh a little over half of the mass of our moon. Thankfully, there’s no chemistry equation in the world that calls for that many mammals. But if there was, you’d now know just how many mammals that would be.