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# Unit Conversion Practice Worksheet

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## Unit Conversion Practice Worksheet

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1. Unit Conversion Practice Worksheet Init 12/17/2007 by Daniel R. Barnes Hit the “End” key on your keyboard at any time to jump to the table of contents for this presentation. From there you can jump to just about anywhere in the presentation. WARNING: Some images appearing in this presentation may have been swiped without permission from the world wide web. Equally as heinous as this, I completely ignore significant figure conventions when I round numbers.

2. SWBAT . . . . . . convert between grams, moles, molecules, and liters of gas at STP

3. Let’s say you want to buy a six-dollar hamburger, but all you’ve got is pennies.

4. How many pennies would it take to buy that six-dollar burger? 6 x = ? x

5. To figure out how many pennies six dollars is, you need to know how many pennies one dollar is. ? x = 100

6. Now that we know one dollar is one hundred cents, we can do a unit conversion to find out how many pennies it takes to buy a six dollar burger. \$6 100 ¢ x = 600 ¢ \$ 1 1

7. It takes 600 pennies to equal 6 dollars. We figured this out by converting six dollars into pennies. Dollars and cents are both units for measuring amounts of money. We’ve just done a unit conversion. \$6 100 ¢ x = 600 ¢ \$ 1 1

8. This one was easy. You could have probably done it in your head. Everyone loves money, so they find it pretty easy to do money math. However, in chemistry, we have to do unit conversions that are more bizarre, using funny numbers and weird units, so we have to learn a procedure and stick to it. \$6 100 ¢ x = 600 ¢ \$ 1 1 You will use the method shown above to do almost all your unit conversions in chemistry. The numbers are sometimes fancier, and the units are weirder, but the procedure remains the same.

9. Unit Conversions

10. Unit Conversions Remember that when you perform a unit conversion, the original quantity does not really change. It’s still the same size. It just looks different.

11. Unit Conversions “\$6” looks quite different than “600¢”, but they mean exactly the same thing.

12. How many seconds in a human lifetime?

13. How many seconds in a human lifetime? Let’s assume that you live to be 100 years old. 100 years 365 days 24 hours 60 minutes 60 seconds x x x x 1 1 year 1 day 1 hour 1 minute 100 yr x 365 days/yr = 36,500 days 36,500 days x 24 hr/day = 876,000 hr 876,000 hr x 60 min/hr = 52,560,000 min 52,560,000 min x 60 s/min = 3,153,600,000 s In scientific notation, 3,153,600,000 s = 3.1536 x 10 109 s That’s about three billion seconds.

14. How many seconds in a human lifetime? Let’s assume that you live to be 100 years old. 100 years 365 days 24 hours 60 minutes 60 seconds x x x x 1 1 year 1 day 1 hour 1 minute 100 yr x 365 days/yr = 36,500 days 36,500 days x 24 hr/day = 876,000 hr 876,000 hr x 60 min/hr = 52,560,000 min 52,560,000 min x 60 s/min = 3,153,600,000 s In scientific notation, 3,153,600,000 s = 3.1536 x 10 109 s That’s about three billion seconds.

15. 1.9095636 ) 3.1536 6.022 Could you count all the molecules in a mole of water? A mole of anything is . . . 6.022 x 1023 molecules. Let’s say you can count one molecule per second. 6.022 x 1023 seconds 1 lifetime x 3.1536 x 109 1 seconds = 1.91 x 10(23-9) lifetimes = 1.91 x 1014 lifetimes That’s about 200 trillion lifetimes 3.1536 x 10 109 s That’s about three billion seconds.

16. Could you count all the molecules in a mole of water? GET COUNTING! = 1.91 x 1014 lifetimes That’s about 200 trillion lifetimes

17. Proxima Centauri, a red dwarf, is the second closest star to the earth. The closest star to the earth is . . . . . . the sun. It’s only 93,000,000 miles away from the earth. Proxima Centauri is so far away that the distance between it and the earth is not measured in miles, but in . . . . . . light years. Proxima Centauri is 4.2 light years away from the earth. How many miles is that?

18. A light year is how far light travels in one year. 4.2 light years The speed of light is 186,000 miles per second. How fast is that in miles per year?

19. A light year is how far light travels in one year. The speed of light is 186,000 miles per second. How fast is that in miles per year? 186,000 mi 60 s 60 min 24 h 365 days x x x x s 1 min 1 h 1 day 1 yr = 5,865,696,000,000 mi/yr

20. A light year is how far light travels in one year. The speed of light is 186,000 miles per second. How fast is that in miles per year? 186,000 mi 60 s 60 min 24 h 365 days x x x x s 1 min 1 h 1 day 1 yr 12 = 5,865,696,000,000 mi/yr = 5.866 x 10 mi/yr Proxima Centauri is 4.2 light-years away, so how far does light travel in 4.2 years? A light year is about six trillion miles. trillion billion million thousand 5.866 24.6372 trillion miles x 4.2 13 = 2.4 x 10 miles 24.6372

21. Proxima Centauri 24,637,200,000,000 miles Earth

22. This has all been very interesting, but now we need to focus on the kinds of unit conversions that you’re actually going to have to do on the test.

23. This has all been very interesting, but now we need to focus on the kinds of unit conversions that you’re actually going to have to do on the test.

24. Before actually doing some true mole math problems, you’re going to take a good look at your tool box.

25. Volume of Gas at STP (L) "The Mole Road Map" Standard temperature = 0oC = 273 K = 32oF See Prentice Hall’s Chemistry textbook, page 303 MOLE Representative Particles (atoms, molecules) Mass (g)

26. SWBAT . . . . . . understand the definition of STP

27. P = 0 atm in outer space “Standard Temperature and Pressure” STP 1 atm OoC P = 0.3 atm on top of Mt Everest P = 1 atm at sea level

28. These are all different ways of saying standard pressure.

29. One mole of gas at STP occupies 22.4 liters of volume. It doesn’t matter what gas it is. At STP, 6.022 x 1023 gas molecules takes up 22.4 liters of space. That’s just a bit more than the combined volume of 11 two-liter soda bottles. 22.4 L = 1 mol

30. If you don’t memorize it, you better know where to look.

31. Volume of Gas at STP (L) "The Mole Road Map" Standard temperature = 0oC = 273 K = 32oF See Prentice Hall’s Chemistry textbook, page 303 MOLE Representative Particles (atoms, molecules) Mass (g)

32. Volume of Gas at STP (L) In what units is each quantity measured? MOLE Representative Particles (atoms, molecules) Mass (g)

33. If the material is a covalently-bonded compound, the “representative particle” unit will be molecules. Representative Particles (atoms, molecules)

34. If the material is a polyatomic non-metal element, the “representative particle” unit will be molecules. Representative Particles (atoms, molecules)

35. If the material is a noble gas, a lattice-forming non-metal, or a metal, the “representative particle” unit will be atoms. Representative Particles (atoms, molecules)

36. Na Na Na Na Na Na Na Na Cl Cl Cl Cl Cl Cl Cl Cl If the material is ionic, technically, the “representative particle” unit would be “formula units”. Representative Particles (atoms, molecules)

37. Volume of Gas at STP (L) How do you convert from one quantity to another? MOLE Representative Particles (atoms, molecules) Mass (g)

38. Volume of Gas at STP (L) To go from grams to moles or from moles to grams you need . . . In what units is molar mass given? MOLE MOLAR MASS g/mol Representative Particles (atoms, molecules) Mass (g)

39. Volume of Gas at STP (L) To go from particles to moles or from moles to particles, you need . . . In what units is Avogadro’s number given? MOLE AVOGADRO’S NUMBER molecules/mol Representative Particles (atoms, molecules) Mass (g)

40. Do you remember Avogadro’s Number? What is it? NA = 6.022 x 1023 formula units/mol molecules/mol atoms/mol It’s not on your CST Reference Sheet, so you’d better memorize it.

41. Volume of Gas at STP (L) To go from volume of gas at STP to moles, or from moles to volume of gas at STP, you need . . . 22.4 L/mol This is a constant, and it Can be found on your CST Reference Sheet. MOLE Representative Particles (atoms, molecules) Mass (g)

42. Volume of Gas at STP (L) These three pieces of information are your “mole math tool box”. 22.4 L/mol MOLE MOLAR MASS AVOGADRO’S NUMBER g/mol molecules/mol Representative Particles (atoms, molecules) Mass (g)

43. Volume of Gas at STP (L) "The Mole Road Map" 22.4 L/mol MOLE MOLAR MASS AVOGADRO’S NUMBER g/mol molecules/mol Representative Particles (atoms, molecules) Mass (g)

44. Did you get it? Q1: What “tool” allows you to convert grams into moles or convert moles into grams? A: molar mass Q2: Why is molar mass the right tool for converting grams into moles or converting moles into grams? A: Molar mass is given in grams per mol = g/mol Q3: What is Avogadro’s number? A: 6 x 1023 Q4: What is Avogadro’s number useful for? A: converting molecules into moles or moles into molecules

45. Did you get it? Q5: When you see “STP” in a question, what mathematical quantity should immediately pop into your head? A: 22.4 liters per mole of gas = 22.4 L/mol Q6: What does “STP” stand for? A: Standard temperature and pressure Q7: What are the conditions at STP? A: a temperature of zero degrees Celsius (273 Kelvins = 32oF) and a pressure of 1 atm = 101.3 kPa = 14.7 psi = 760 mmHg = . . .

46. Did you get it? Q8: How do you get molar mass? A: calculate it using the chemical’s formula and the atomic masses from the periodic table. Q9: Where can you get Avogadro’s # during a test? A: Sorry. You have to memorize it. Q10: Where can you get that 22.4 L/mol thingie? A: It’s on the back side of the reference sheet. Q11: How many representative particles are in a mole? A: 6 x 1023 representative particles = 1 mole Q12: What does “representative particles” usually mean? A: “molecules”

47. http://what-if.xkcd.com/4/

48. Unit Conversion Practice Worksheet Try each problem in pencil before you look at the answer. Then, make whatever corrections you need to make to your answer. Don’t just look at the answer first, or you won’t learn as much.

49. 1. How many grams is 72 kilograms? 72 kg 1000 g x = 72,000 g 1 1 kg 1 kilogram = 1000 grams

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