Mass

(but not the kind that lives underground) The Mole 1 Where Are We Going? Count large objects by ones (cars). Count smaller objects by dozens (eggs). Count tiny objects by hundreds (ream of paper). Where Are We Going? Smaller objects need larger numbers to be sizeable. Atoms and molecules are so small that we must have a HUGE number of them to work with them. Avogadro?s Number 2 is a pair. 12 is a dozen. 144 is a gross. 602,200,000,000,000,000,000,000 is Avogadro?s number. It can be written 6.022 ? 1023. The Mole A mole is the amount of matter in Avogadro?s number of particles (i.e., 6.022 ? 1023 particles). Use four significant digits for calculations. Why That Number? That many particles weighs (in grams) the exact weight (in u) of one particle. 1 atom of H weighs 1.008 u.