I almost forgot

Indeed, mole day.

A mole is a unit of measure, like a cup or a quart, only... different.  It’s more like a dozen, because it’s an exact number of items -- it’s 6.02 x 10^23 items.  Which is a lot, unless you’re talking about atomic particles.  The mole is used to measure quantities in chemistry, and its value was discovered by a guy named Avogadro.  This number relates the atomic mass of an element to its mass in grams.  So for example, oxygen has an atomic mass of 16, and 6.02 x 10^23 oxygen atoms weigh 16 grams.  And when you’re doing calculations that span 3 or 4 or 5 pages, it’s a heck of a lot nicer to use moles for your quantities than to constantly write n.nn x 10^23.

Anyway my chem teacher in high school made a big deal about it whenever October 23rd came around.  I would have thought that all chem teachers did, but I guess yours didn’t?