1. Bell Ringer The mass of a copper cylinder is 49.71 grams. If the mass of one copper atom is 1.06 x 10 -22 g, how many copper atoms are there in the cylinder?

2. Counting Atoms and the Mole

3. Counting Atoms SI unit for amount of substance is called mole. A mole measures the number of particles within a substance. A mole refers to a specific number of particles. (Counting Unit)

4. 1 mole = 6.02 x 10 23 particles 6.02 x 10 23 is also known as Avogadro’s Number 1 mole magnesium = 6.02 x 10 23 Mg atoms 1 mole zinc = 6.02 x 10 23 Zn atoms 1 mole lead = 6.02 x 10 23 Pb atoms

5. Molar Mass Although 1 mole always contains the same number of particles, the mass of one mole varies depending on the substance. Molar Mass – mass of one mole of a substance. Mass of one mole of an element is equal to its ATOMIC MASS expressed in grams. –1 mole of magnesium = 24.31 grams –1 mole of zinc = 65.39 grams –1 mole of lead = 207.2 grams

6. Mole Conversions Many times in chemistry, you will need to express a measurement in a unit different from the one given or measured initially. Conversion factor = ratio of equivalent measurements used to convert from one unit to another. (take form of a fraction) LabelNumber Used in Conversion Factor Mole1 Atoms6.02 x 10 23 Mass (grams)Molar Mass (Atomic Mass)

7. Sample Problem A student has a 1 mole sample of silver and a 1 mole sample of gold. a)Which sample contains the greatest number of atoms? How many atoms are in each sample? b)Which sample has the greatest mass? What is the mass of each sample? c)The current price of gold is $44.64 per gram. How much is the gold sample worth?

8. Mole Conversion Problems A chemist produced 11.25 g of magnesium, Mg. How many moles of magnesium were produced? Determine the number of silver atoms that are contained in 0.650 mol Ag? Calculate the mass, in grams, of 3.07 x 10 24 atoms of sulfur (S).

9. One Minute Paper You have one minute to answer these two questions concerning today’s lesson. –What was the most important thing you learned? –What is still muddy?