23 October 12

It's Mole Day! Quick, get three and a half teaspoons of water (18 ml) or about 56 ordinary small paper clips (56 g). You are looking at (roughly) 6 X 10^23 molecules of water, or 6 X 10^23 atoms of iron. That constant number, which is 602,214 followed by 18 zeros, defines a "mole" of anything, and it expresses one of the fundamental units in chemistry. October 23, which is 10.23 or 10-23 or 10/23, reminds chemists everywhere about "Avogadro's Number." National Chemistry Week is celebrated every October during the week that includes Mole Day.