2. So what unit do chemists use to count particles? Particles are so tiny, chemists use the unit of moles. A mole contains 6.02 x 10 23 atoms. 602, 000, 000, 000, 000, 000, 000, 000

3. One mole of popcorn would cover every dry surface of the Earth to a depth of six miles One mole of stacked pennies would reach to the moon and back 16 times One mole of marshmallows would cover the US to a depth of 650 miles

4. 1811- Avogadro- equal volumes of gases at the same temperature and pressure contained equal number of molecules 1861- Cannizzaro- developed atomic weights for known elements 1865- Loschmidt- determined the number of atoms present in given volume of air 1971- true value 6.02 x 10 23 found

5. Recall the Law of Conservation of Mass Mass of reactants = mass of products Mass of starting substances = mass of ending substances 2 hydrogen atoms + 1 oxygen atom  1 water molecule

6. Law of Definite Proportions Regardless of amount, a compound will always be composed of the same elements in the same proportions by mass For example, two hydrogen atoms will always combine with one oxygen atom to produce one molecule of water

7. Moles ↔ Particles Conversion Particles Atoms, molecules x 6.02 x 10 23 ÷ 6.02 x 10 23 Moles

8. Convert 3.5 moles to atoms

9. Convert 18.06x10 23 atoms to moles

10. Convert from moles to particles 2.7 moles of lithium 1.8 moles of sodium chloride

11. Convert from moles to particles 5.3 moles of bromine 4.7 moles of potassium oxide

12. particles  moles 4.32 x 10 24 atoms of calcium

13. particles  moles 2.7 x 10 20 atoms of copper

14. particles  moles 2.5 x 10 24 molecules of sodium chloride 5.32 x 10 23 molecules of calcium chloride

15. You try these… 25 moles to particles 4.08 x 10 4 particles to moles 0.002 moles to particles 2.3 x 10 16 particles

16. Homework Complete on another sheet of paper showing your work! Moles to particles 2.7 moles 1.8 moles 5.3 moles 4.7 moles Particles to moles 4.32 X 10 24 2.70 X 10 20 2.50 X 10 24 5.32 X 10 23