1. OCTOBER 27, 2015 Objective: Demonstrate how the conservation of atoms in chemical reactions leads to the ability to calculate the mass of products and reactants using the mole concept. Do Now: Brainstorm various counting units that can be used to group different items, or different groups of people. Record your ideas on the following table in your notebook: Counting unitNumber of units Ex: Dozen12

2. MOLES 3.4

3. COUNTING UNITS We buy things by the dozen One dozen = 12 items We use the unit mole to measure things in chemistry.

4. MOLES The SI base unit that describes the amount of a substance.

5. MOLES Avagadro’s number represents the number of particles in one mole of a substance. The number is 6.02 x 10 23 One mole also represents the atomic mass of an element. Ex: 1 atom of Mg has a mass of 24.3 amu 1 mole of Mg is 24.3g

6. CONVERSION FACTORS Get into groups of 4. Brainstorm units of measurement for your area of measurements. Write each unit on a card. Then, shuffle the cards and pick 2. Come up with a way to get from the Left unit to the Right unit. 10 minutes. Lets see A)How many units, and B) how many conversion factors each group can get!

7. MOLAR MASS Using the periodic chart you can determine the molar mass of any element. It will equal the atomic mass of the element. Example 40 Ca 20 has an atomic mass of 40 as well as a molar mass of 40. Therefore one mole of Ca equals 40g. Two moles would equal 80g.

8. MOLES You can determine how many moles of a substance you have if you know the mass of the substance Example If you have 92 grams of Na how many moles would you have.

9. SOLUTION You divide the mass by the molar mass of the element. 92g/23 = 4 moles

10. GRAPHIC ORGANIZER! 1 mol Molar Mass Mass in grams Molar Mass 1 mol Number of moles X = = x

11. PRACTICE! What is the mass, in grams, of each of the following? 2.50 mol of Sulfur 1.80 mol of calcium 0.50 mol of carbon

12. SIGNIFICANT FIGURES (SIG FIGS) Do Now: Determine how many Sig Figs are in the following: a) 1.638b) 900.06 c) 0.0004d) 8.1000 e) 0.0230