WELCOME TO CHEMISTRY

1. WELCOME TO CHEMISTRY

2. What is Chemistry? Study of matter and energy Matter= all the “stuff”- anything that has mass or takes up space Energy=what lets us do work (move things)- this includes light, sound, heat Everything is either matter or energy Therefore… it is all chemistry (the “central science”) no matter what they told you in biology!

3. Branches of Chemistry • Analytical chemistry • Answers questions about composition (what is the level of lead in that drinking water?) • Physical chemistry • Deals with energy transfers in chemical processes (how much energy is stored in a battery?) • Biochemistry • Deals with the analysis of chemical processes in living things (cellular process such as photosynthesis and respiration) • Organic chemistry • Study of carbon containing molecules (overlap with biochem) • Inorganic chemistry • Study of the chemistry of nonliving things (geological chemistry, the analysis of the rate of corrosion of metals) • Other areas overlap (geochemistry) as well • Which branches might be involved in developing a dye for clothing?

4. Pure and Applied Chemistry • Pure Chemistry- Pursuit of chemical knowledge for its own sake. (studying it because you want to) • Ex: Nylon • Applied Chemistry- research directed to a practical goal or application • Ex: researching the commercial use of nylon

5. Macroscopic vs Microscopic • Macroscopic- objects large enough to see with an unaided eye • Microscopic – objects that could only be seen with an aided eye

6. Quick review of scientific method Observations Hypothesis Theory Scientific law EXPERIMENTS

7. Theory vs Law • Theory – well tested explanation for a broad set of observations • CAN BE CHANGED • Law – concise statement that summarizes the results of many observations and experiements

8. SI System • Agreed upon set of units and measurements- used all over the world • Except… (which country?) • Common base units used by chemists are: • Kilogram (mass) • Meter (length) • Kelvin (temperature) • Second (time) • Mole (amount)

9. Prefixes to the SI System • Deal with ones we use in class • mega (M) = million or 106 (factor of 1000000) • kilo (k) = thousand or 103 (factor of 1000) • deci (d) = tenth of 10-1 (factor of 0.1) • centi (c) = hundredth or 10-2 (factor of 0.01) • milli (m) = thousandth or 10-3 (factor of 0.001) • Micro (μ)= millionth or 10-6 (factor of 0.000001) • nano (n) = billionth or 10-9 (factor of 0.000000001) • pico (p) = trillionth or 10-12 (factor of 0.000000000001) • There are others as well.

10. Massunits and estimations • Basic SI unit = kilogram (mass of a textbook or a brick) • gram (g) or .001 kg (mass of a small paper clip) • milligram (mg) or .000001 kg (or .001 g) (mass of a few grains of salt- many medicine doses are mg) • microgram (μg) or .000000001 kg (.000001 g or .001 mg) mass of a grain of talcum powder

11. Volume • The amount of space an object takes up • Liter (L) and milliliter (ml) are most widely used. • A ml is the same as a cube 1 cm on a side (1 cm3 or cubic cm, cc) • There are 1000 ml to 1 L • 1L = 1000 ml or 1 ml = .001 L • 1L ≈ 1 quart (1 gallon ≈ 3.8L or 4 L) • 1 ml = 20 drops, 1 teaspoon = 5 ml

12. Volume estimations • Bathtub holds about 200L • Your car’s gas tank holds about 50-80 L • A medicine dropper holds 5 – 10 ml • A coffee mug holds about 400 ml

13. Length • Basic unit = meter • Also widely used are km, cm, mm, μm and nm • 1000 m = 1 km or 1 m = .001 (1/1000) km • 100 cm = 1 m • 10 mm = 1 cm and that means… • 1m = 1000 mm (or 1 mm = 0.1 cm)

14. Length Estimations • 1 km is about 2/3 mile (WHS to Wawa on Bethlehem Pike) • Doorframe = 2 m (a very tall person) • Ceiling in school is about 3 m high • 1 cm is about the width of a finger • 1 mm is about the thickness of a dime • (Are there about 10 dimes to a finger? (yes) • 1 μm = size of bacterium (micron) • nm = molecules sizes, picometer (pm) atomic nucleus

15. Temperature • “Official” unit = Kelvin (K) • Most widely used for measurement = degrees Celsius (ºC) • Temp in Kelvin = ºC + 273 (º C = K -273) • Examples: ice water = 0 ºC = 273 K • Boiling water = 100 ºC = 373 K • Body temp = 37 ºC = 310 K (about 99 ºF) • Hot coffee or tea = 85 ºC = 358K • Fridge = 4 ºC = 277 K • Very cold day = -15 ºC = 258 K (about 5 ºF)

16. Practice (unit first, then number) • Mass of a person • Length of this hallway • Mass of a quarter • Room temperature • Volume of a “half gallon” milk carton • Volume of a small cup of juice • Height of a desktop at school • Length of a dollar bill

17. Answers • Mass of a person – about 70 kg • Length of this hallway – about 25 m • Mass of a quarter – about 10 g • Room temperature – about 20-25ºC (293-298 K) • Volume of a “half gallon” milk carton- about 2 L • Volume of a small cup of juice – about 250 ml • Height of a desktop at school – about 1m • Length of a dollar bill – 15 cm (almost exact) (note that this = 6 inches, so you always have a 6 inch or 15 cm ruler with you!)

18. Some Conversions (the factor label method) • Use a system and you won’t have to guess do I multiply or divide? Or which way should I move the decimal place? • You must know the basic metric prefixes • (kilo, deci, centi, milli, micro) • First a non metric example: • How many minutes is 450 seconds? • (you need to know the relationship 1 min= 60 sec)

19. Factor Label Example # 1 • Start with what you are given: 450 seconds • Use the known “factor” (known relationship) • Make the units cancel to give you minutes • 450 seconds 1 minute = 7.5 minutes 60 seconds The key is to make the units work

20. Practice • Convert 145 cm to m • You must know that there are 100 cm to 1 m 145 cm 1 m = 1.45 m 100 cm Check to see that the units work. If the units work, the numbers will too. 17.4 m = how many mm (knowing1m=1000mm) 17.4 m 1000 mm = 17400 mm 1m

21. More practice • Convert 458 mg to grams • You have to know that 1 g = 1000 mg • How do you know what goes on top and bottom? • Make the units cancel! (the factor) 458 mg 1 g = 0.458 g (the unit we want) 1000 mg

22. A more involved one(non-SI units are notyour responsibility • How many cm are in 2 miles • 1 mile = 5280 feet, 1 foot = 12 inches and 1 inch = 2.54 cm (these would be given) • Strategy: miles  feet  inches  cm 2 miles 5280 feet 12 in 2 .54 cm = 321869 cm 1 mile 1 ft 1 in You have to practice a bunch of these to get good at them (and you will get good at them)

23. Really Complex Convert a speed of 35 miles/hour to m/s Given: 5280 ft = 1 mile, 1 ft = 12 in, 1 in = 2.54 cm Your responsibility 100 cm = 1m (SI units) 35 miles 1 hour 1 min 5280 ft 12 in 2.54 cm 1 m = 1 hr 60 min 60 sec 1 mile 1 ft 1 in 100 cm 15.6 m/s (we’ll learn how to handle the number of digits soon) How to “punch it in” (follow on board for examples) Now go do some for practice! (you need to really know the SI units)

24. A Few for You to Try • Convert 6.7 cm to m • Convert 9.73 mg to cg • Convert 14675 cm to km • Convert 8.75 kg to mg • Convert 4500 cg to Mg

25. Set-up For Solving 6.7 cm 1 m = 0.067 m 100 cm 9.73 mg 1 cg = 0.973 cg 10 mg 14675 cm 1 m 1 km = 0.14675 km 100 cm 1000 m 8.75 kg 1000 g 1000 mg = 8750000 mg 1 kg 1 g 4500 cg 1 g 1 Mg = 0.000045 Mg 100 cg 1000000g

26. Scientific (Exponential) Notation • A very useful way to describe small and large numbers • Numbers are written as the product of some number from 1.0 to 9.99 x 10 to a power (form of a x 10b) • Examples (note + exponent = > 1 and – exponent = <1) • 325 = 3.25 x 102 • 0.0076 = 7.6 x 10-3 • 7987.07 = 7.98707 x 103

27. 698 = 9.87 x 10-6 = 0.087 = 5.67 x 105 0.000076 = 78700000 = 0.00000891 = 86.3 = 4.82 x 10-8 = 6.98 x 102 0.00000987 8.7 x 10-2 567000 7.6 x 10-5 7.87 x 107 8.91 x 10-6 8.63 x 101 0.0000000482 Practice/Examples

28. More Practice • 6.78 x 10-5 = 0.988 = • 5.90 x 105= 387000 = • 1.8543 x 10-3= 450.98 = • 9.99 x 10-4= 5.00 = • 6.23 x 106= 356.4 = • 7.72 x 10-5= 0.000156 = • 8.78 x 108 = 0.076 =

29. The Answers • 6.78 x 10-5 = 0.0000678 0.988 = 9.88 x10-1 • 5.90 x 104= 59000 387000 =3.87 x105 • 1.8543 x 10-3= 0.0018543 450.98 = 4.5098 x 102 • 9.99 x 10-4= 0.000999 5.00 = 5.00 x 100 • 6.23 x 106= 6230000 356.4 = 3.564 x 102 • 7.72 x 10-5= 0.0000772 0.00156 = 1.56 x 10-3 • 8.78 x 108 = 878000000 0.076 = 7.6 x 10-2

30. Multiplying in scientific Notation • General rule: (a x 10b)(c x 10d) = ac x 10(b+d) Multiply the front parts and add the exponents Ex: (4 x 102)(2 x107) = 8 x 109 Ex: (5 x 105)(6 x 103) = 30 x 108 (oops the “front” is >9.99. Turn 30 into 3 (down 1 exponent) and add 1 to the exponent to compensate = 3 x 109 On a calculator: 5 EE (or EXP) 5 x 6 EE (or EXP) 3 = and you’ll see . You “translate” into 3 x 109). Note you don’t punch in x 10– (times ten to the) (EE or EXP replaces that) Learn how to use your calculator! 3 09

31. Dividing in Scientific Notation • Similar logic as multiplying except… • You divide the front parts and subtract the exponents: • Ex: (5 x 104)/(2 x 105)= 5/2 x 10(4-5) • Or 2.5 x 10-1 (which is also 0.25) • Ex: (4 x 104)/(8 x 102) = 0.5 x 102 (oops) • Turn 0.5 into 5 (up 1 place) and compensate by making the exponent 1 less (5 x 101) (which = 50)

32. On Your Calculator (4 x 104)/(8 x 102) • For this problem you’d punch in: • (EE and EXP buttons do the same – you’ve got one of them!) • 4 EE 4 and you’ll see • / (divided by) • 8 EE 2 = and you’ll see • (or you’re calculator may turn it into 50) • What will your calculator do? Get familiar with it and you’ll know! 4 04 5 01

33. Significant Figures • No measurements are perfect • In any measurement you make you can include all numbers that are known plus one additional estimated number. • On a car speedometer you can say you are going 62 mph (you know it is 60-something for sure and the 2 is a good estimate (but you wouldn’t be shocked if you were really going 61 or 63) • You can’t go more places than that (62.37 may sound better but that’s all it does.)

34. Sig Figs Rules • All nonzero numbers are significant (1,2…9) • Zeroes between nonzero numbers are significant (the “0” in 406) • Leftmost zeroes are never significant (as in 0.005) • Rightmost zeroes are significant only if a decimal point is present (as in 8.900) • This applies to measured numbers (not counted (12 eggs to a dozen) or definitions • Those don’t have measurement uncertainty • In general, you can have one more digit (the estimated one) than your measuring device is marked off to

35. One estimated digit Marked of to the nearest whole number- estimated to 1 decimal Place. It is definitely 38 point something (the “6” is a good estimate and is trusted). Marked of to the nearest tenths place- estimated to 2 decimal places. It is definitely 38.5 something (the 7 is a good estimate and is trusted).

36. Sig figs cont’d 698 cm has 3 significant figures (shown in yellow) 0.009876 g has 4 significant figures 909.98 ml has 5 significant figures 0.00007 cg has has 1 significant figure 9.000 km has 4 significant figures 90 cms has has 1 significant figure 90.000 cm/s has 5 significant figures 0.00879098000 g/ml has 9 significant figures 908000000 cm has 3 significant figures The word significant doesn’t mean important- it means measured and trusted 90 is not 90.000?

37. So 90 and 90.000 are not the same? • Mathematically they are equal • If I weigh a coin on two balances one capable of reading to the nearest g and one to the thousandth of a gram, they could both read 90 g (one would say 90 and the other 90.000) • The one that reads to a milligram (thousandth) lets me get more “precision” • Watch the demo of graduated cylinders and of the marked measuring sticks

38. Using Sig Figs in Calculations (multiply/divide) • When you multiply or divide your answer can have no more sig figs than the least precise part of your problem (round as you normally would) • Ex: 489.5 x 3.00 = 1468.5 (can only have • So you’d round to 1470 (3 sig figs) • It looks like you’re losing accuracy but you’re not. You are making your answer reflect the measurements that went into it 4 sig figs 3 sig figs 3 sig figs (limited by The least precise part

39. Using Sig Figs in Calculations (add/subtract) • Here you are limited by the number of decimal places: • Ex: 5.990 (3 places) • +7.8 (1 place) • = 13.8 (13.79 rounded to 1 decimal place) (1 decimal place limits you)

40. Sig Fig Calculation Practice • 5.64 x 3.877 = 21.9 (21.866... rounded to 3 sig figs) • 4.999 + 1.2 = 6.2 (6.199 rounded to 1 decimal place (add/subtract has diferent rules) • (4.77 + 8.2)/6.88 = 13.0/6.88 = 1.89 • (4.1 x 103)(1.6772 x 102) = 6.9 x 105 or 69000 (not 68765.2) • Extra digits look good but they aren’t worth much

41. Accuracy and Precision • Accuracy = “correctness” • Precision = consistency of a set of measurements (1 measurement is not precise) • Field Goal ex: If you are always wide to the right, you are precise (consistent) but not accurate • A watch that is always fast by 5 minutes is precise, but not accurate

42. Accuracy and Precision

43. Wrap-Up of Unit 1 • Lots of stuff here • Get used to your calculator. Bring it to class daily and practice with the calculator you’ll use on the tests. • Test study hint- use the “chapter study guide” sheet as a checklist. There will be notes, homework and practice on just about everything. Ask questions if needed. Come in and get help. It is chemistry.