As a chemistry nerd, Mole Day is one of my favorite days. What’s a mole, you ask? It’s another name for Avogadro’s number, 6.022 × 1023. And 1023 is today’s date – 10/23 – see how we did that?! Chemists, so creative. So really, it is just a number like a “dozen” or a “pair.” It is actually a really really big number that we could also write out as 602214129000000000000000. In fact, did you know that Avogadro’s number is more than a million times as big as the number of seconds since the Big Bang?
Chemists use moles to make counting easier, like when talking about numbers of atoms or molecules. We can actually count anything in terms of moles, like water molecules. How many molecules are in a cup of water, which holds about 240 g of water? It turns out that a cup of water contains about 8,000,000,000,000,000,000,000,000 molecules of water. That’s a lot of molecules and chemists don’t want to write that out every time, so we can also just call it 13 moles of water instead.
– Yuki, Khan Academy Chemistry Fellow and fan of moles, both animal and chemical