1. Big Numbers mean Big Problems

2. We can picture 20 sheep, cars, … in our minds. How about large numbers? Number of molecules – defined in terms of Avagadro’s number N a =6.022 136 7(36) x 10 23 molecules/mole How big is this number?

3. Consider standing on the shore of a small lake ~5 mi x 1 mi x 20 ft deep Standing looking across the lake Houses look about 1/2 inch high Cars are too small to see

4. 1 mile 20 feet 5 miles Take 1 Aramark sugar packet pour it into the lake – stir and wait until mixed Fill a 1-liter mug with pond water - drink How many sugar molecules are in the mug?

5. Avagadro’s number tells us how many molecules there are in a mole. How many molecules did we put into the lake? What is the volume of the lake? We know the volume of the mug. We need a concentration. How do we solve the problem?

6. Avagadro’s number A gram molecular weight of a substance (a mole) contains Avagadro’s number of molecules.

7. Periodic Table of the Elements

8. Sugar – C 12 H 22 O 11 From periodic table mass C = 12.01 g/mol H = 1.008 g/mol O = 16.00 g/mol

9. Mass of a mole of sugar = 342.296 g/mol sugar = 342 g/mol gram molecular weight

10. How much sugar (in moles) did we add to the lake? Weigh a packet of sugar – 2.8055 g Probably only good to 2 significant figures – 2.8 g

11. What is the volume of the lake? US miles, feet !!! We need to convert to SI 1 mi = 5280 ft =1.609 km=1609 m wl d V lake =78 892 265 m 3

12. We need to find the concentration of sugar in the water. A standard unit of concentration is molarity. molarity = mol/liter

13. Lets convert the lake volume to liters.

14. Concentration of sugar in the lake from the Aramark sugar packet

15. How many molecules are there in the liter mug? Volume of mug Avagadro’s number Concentration

16. 10 10 = 10,000,000,000 still a fantastically large number What does this tell you about even small chemical spills, releases of gases, liquids, and solids into the environment? How many molecules are we adding? How many can we tolerate?

17. Volume of the Gulf of Mexico = 2,434,000km 3 Volume of the Deep Horizon oil spill = 780,000m 3 = 0.00078km 3 (This is equal to roughly 3ppb)