Warm-up: Intro activity

1. Determine, to the greatest precision and accuracy possible, the thickness of a piece computer paper? Determine which of the following has the most amount of pieces (not necessarily worth the most money). Do you need any more information? 1 kg of pennies 1 kg of nickels 1 kg of dimes Brainstorm as many words as you can that are directly related to numbers (for example, 1 dozen=12) Warm-up: Intro activity

2. coefficients give ratios coefficients of a balanced equation give the ratio of molecules in the reaction 2H2 (g) + O2 (g)  2 H2O (l) ___ molecules of hydrogen gas react with ___ molecules of oxygen gas to give ___ molecules of water

3. Correct Ratio of molecules 2H2 : 1O2 : ?H2O 2 hydrogen molecules 1 oxygen molecule 2 water molecules

4. Wrong Ratio of molecules 1H2 : 1O2: ?H2O 1 hydrogen molecule 1 oxygen molecule ?

5. Problems in chemistry… • Atoms are too small to talk about and measure easily • Atoms of different elements have different masses (periodic table)

6. Also… • Can you “measure out” 2 molecules of hydrogen and 1 molecule of water??? Why or why not??? What do unit do we use to measure? How many molecules are in one gram?

7. Since one gram contains a huge amount of molecules or atoms... chemists have devised a special counting unit to understand the large numbers of molecules or atoms measured in the lab. This unit is called the mole!

8. What is a “counting unit”? • Bakers use the counting unit “dozen” to understand they have 12 donuts • Pencils are sold by the “gross”. If you buy 1 “gross” you will get 144 pencils.

9. Learning Check Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects. 1. How many paper clips in 1 rapp? a) 1 b) 4 c) 8 2. How many oranges in 2.0 rapp? a) 4 b) 8 c) 16 3. How many rapps contain 40 gummy bears? a) 5 b) 10 c) 20

10. The Mole • A counting unit • Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 • 6.02 X 1023 (in scientific notation) • This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

11. Just How Big is a Mole? • Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. • If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. • If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

12. The Mole • 1 dozen cookies = 12 cookies • 1 mole of cookies = 6.02 X 1023 cookies • 1 dozen cars = 12 cars • 1 mole of cars = 6.02 X 1023 cars • 1 dozen Al atoms = 12 Al atoms • 1 mole of Al atoms = 6.02 X 1023 atoms Note that the NUMBER is always the same, but the MASS is very different! Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

13. A Mole of ParticlesContains 6.02 x 1023 particles 1 mole C 1 mole H2O 1 mole NaCl = 6.02 x 1023 C atoms = 6.02 x 1023H2O molecules = 6.02 x 1023NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023Cl– ions

14. Calculator 101 • The mole in scientific notation is 6.02 x 1023 • Type in: • 6.022 • [2nd] • [,] • 23 • [ee] takes the place of “x 10^”

15. Process of multiplying by conversion factors to obtain an answer Hinges on : Neatness and Diligence Steps Find the conversion unit between the 2 units Make this conversion unit into 2 fractions Write the 1st number w/ unit Multiply by the fraction (conversion) that cancels Cancel unit Multiply/ Divide #’s Dimensional Analysis

16. Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a particle could be an atom OR a molecule!

17. Conversion Steps • What are you given? • What is the end unit? • What is the conversion factor? • Set-up problem Given x conversion factor = _______end unit • Cancel out units • Do math • Circle your final answer

18. Example • You have 3.5 dozen roses how many actual roses is this? • Given: 3.5 dozen • End unit roses • Conversion factor 1dozen or 12 roses 12 roses 1 dozen • 3.5 dozen x 12 roses = ____ roses 1 dozen • Cross out matching units

19. Converting Mole Particles • 6.01 mole Na = ? Atoms of Na • .75 mol Cl = ? Atoms Cl • 8.203 x 1024atoms O2 = ? Mol O2

20. Molar Mass Since 1mol always has the 6.02x1023 particles, and (by definition) 1mol 12C has a mass of 12g…then…1mol of 24Mg must have a mass of 1 atom of 12C = 12amu  1mol 12C = 12grams 1atom of 24Mg = 24amu  1mol 24Mg = 24grams 24g

21. Molar Mass How much does one mole weigh? Would 1 mol of 12C weigh as much as 1mol of 24Mg ? *** Remember: one 12C atom has a mass of 12amu & one 24Mg atom has twice as much mass or 24amu

22. Molar Mass • The Mass of 1 mole (in grams) • Equal to the numerical value of the average atomic mass (get from periodic table) 1 mole of C atoms = 12.0 g 1 mole of Mg atoms = 24.3 g 1 mole of Cu atoms = 63.5 g

23. Molar Mass The mass of a single atom of an element (in amu) is numerically equal to the mass (in grams) of 1mol of that element 1 mol Zn = _____ g 1mol Al = _____ g

24. Na atoms Pb atoms Molar mass is the mass of 1 mole of in grams Kr atoms Li atoms 1 mole C atoms = 6.022 x 1023 atoms = 12.011 g 1 mole lithium atoms = 6.941 g of Li For any element atomic mass (amu) = molar mass (grams)

25. Other Names Related to Molar Mass • Molecular Mass/Molecular Weight: If you have a single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different. (This is the beauty of Avogadro’s Number!) • Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different. • THE POINT: You may hear all of these termswhich mean the SAME NUMBER… just different units

26. Conversion factors • Moles to mass (grams) molar mass (periodic table) = grams mole • Mass (grams) to moles mole = mole molar mass (grams)

27. Mass to Atoms and Atoms to Mass • 2 steps • Mass g (given) to moles • Mol to atoms (particles) Mass g (given) x 1mol x 6.02*1023= atoms mass g (PT) 1 mol Atoms (given) x 1 mol x MM (PT) = grams 6.02*1023 1 mol (atoms)

28. Do You Understand Molar Mass? How many atoms are in 0.551 g of potassium (K) ? 1 mol K 6.022 x 1023 atoms K x x = 1 mol K 39.10 g K 1 mol K = 39.10 g K 1 mol K = 6.022 x 1023 atoms K 0.551 g K 8.49 x 1021 atoms K 3.2

29. Moles, n Avogadro’s Number Molar Mass # Atoms Mass, grams

30. Practice Time • Complete practice questions • Don’t forget units and sig figs

31. Mole of compound to mole of individual atoms in the compound • Example: How many moles of F atoms are there in 5.5 moles of CCl2F2 ? • Given 5.5 moles of CCl2F2 • Want atoms of F • Need a conversion factor that relates moles of F to moles of compound • moles of CCl2F2 x moles of F atoms = moles of F atoms 1 mole of CCl2F2 • F2 = 2 moles of F • 5.5 moles of CCl2F2 x 2moles of F atoms = moles of F atoms 1 mole of CCl2F2

32. Practice What is the mass (in grams) of 2.01 x 1022 atoms of S?

33. Work Time • Read section 11.1 pages 309-312 • Complete: • Practice problems 1-3 on page 311 and 4 on page 312 ***must show all of your work for credit*** • Assessment questions 1-10 on page 312