3. Using Mass to Count Things Atoms are so tiny it is impossible to count number of atoms in even 1 gram of matter massWe use mass to “count” atoms

4. Counting by mass a pile of nails weighs 1227 g one nail has mass of 0.450 grams How many nails are in pile? 1227g_____ = 2726.6 nails 0.450 g per nail

5. What is a mole? No, not this kind of mole!

6. The MOLE Unit used to “count” numbers of atoms –Count-by-mass technique Defined as # of atoms in 12.0 grams of C-12 –This is the STANDARD! 12.0 g of C-12 has 6.0221415 X 10 23 atoms

7. Just how big is a mole? Mole movie

8. The MOLE 1 mole of any element has 6.02 X 10 23 particles This is a really big number – It’s so big because atoms are really small!

9. 6.02 X 10 23 = Avogadro’s Number One mole of water = 6.02 X 10 23 water molecules One mole of gorillas = 6.02 X 10 23 gorillas One mole of He atoms = 6.02 X 10 23 He atoms One mole of anything = 6.02 X 10 23 of that thing

10. Similar Words PairPair: 1 pair shoelaces = 2 shoelaces DozenDozen: 1 dozen oranges = 12 oranges GrossGross: 1 gross spider rings = 144 rings ReamReam: 1 ream paper = 500 sheets of paper MoleMole: 1 mole Na atoms = 6.02 X 10 23 Na atoms

12. Equalities 1 mole of C-12 = 12.0 grams of C-12 = 6.02 X 10 23 atoms of C-12 0.5 mole of C-12 = 6.0 grams of C-12 = 3.01 X 10 23 atoms of C-12

13. Equalities 1 mole of C-12 = 12.0 grams of C-12 = 6.02 X 10 23 atoms of C-12 0.25 mole of C-12 = 3.0 grams of C-12 = 1.50 X 10 23 atoms of C-12

14. Equalities 1 mole of C-12 = 12.0 grams of C-12 = 6.02 X 10 23 atoms of C-12 2 moles of C-12 = 24.0 grams of C-12 = 12.04 X 10 23 atoms of C-12 = 1.204 X 10 24 atoms of C-12 How does this help with other elements?

15. Molar mass for any element: molar mass of any element: –take atomic mass and replace a.m.u. with grams 1 mole Ne = 20.179 g = 6.02 X 10 23 atoms 1 mole Ar = 39.948 g = 6.02 X 10 23 atoms 1 mole Kr = 83.80 g = 6.02 X 10 23 atoms

16. sliding scale of size How small?