2. Scientific & Chemical Fundamentals Dr. Ron Rusay Fall 2007 © Copyright 2003-2007 R.J. Rusay

3. Scientific & Chemical Fundamentals  Chemistry & the Scientific Method  Matter : Classification & Properties  Mathematics / Arithmetic: Exponents, Significant Figures  Measurement & Units: (SI & metric)  Conversions and Relationships: Dimensional Analysis: Density, Percent  VOCABULARY: Key Terms, Bold Style Learning © Copyright 1998-2007 R.J. Rusay

4. Textbook Reading Chemical Foundations 1.1 Chemistry: An Overview 1.2 The Scientific Method 1.3 Units of Measurement 1.4 Uncertainty in Measurement 1.5 Significant Figures and Calculations 1.6 Dimensional Analysis 1.7 Temperature 1.8 Density 1.9 Classification of Matter

5. Science & The Scientific Method

6. QUESTION The difference between a scientific law and a scientific theory can, at times, be confusing. For example, we will refer to the “Atomic theory” or perhaps the “Law of Gravity.” Should the Law of Gravity be changed to the Theory of Gravity? 1.Yes, no one can see gravity, it is better described as a theory. 2. No, scientific laws are based on summaries of many observations and gravity observations are well known and predictable. 3.Yes, gravity is better described as a theory because gravity explains why masses attract each other and theories are about explaining observations. 4.No, keep it as a law, laws offer explanations and gravity explains why masses attract each other and laws are about explaining observations.

7. Some Possible Steps in the Scientific Method  1. Observations qualitative qualitative quantitativequantitative  2. Formulating hypotheses  possible  possible explanation(s) for the observation  3. Performing experiments gatheringgathering new information testing whether the hypotheses are valid  4. Developing a theory  5. Testing & Refining

8. Chemistry: The Study of Matter  In all of its forms & all of its behaviors  Sub-categories (not so distinct any longer) Organic: carbon Inorganic: non-carbon Organometallic: organic + inorganic Analytical: what?, how much?, how pure? Biological / Biochemistry: living organisms Physical: energy, changes, rates Nuclear: the nucleus Environmental: interdisciplinary, eg. Oceanography © Copyright 1998-2007 R.J. Rusay

9. Chemistry & Matter (Chemicals)  How many different chemicals do you think have been reported in the scientific literature? A) 100,000 B) 1,000,000 C) 10,000,000 D) 100,000,000 E) 1,000,000,000

10. Chemistry & Matter: Properties & States Physical vs. Chemical Properties Solid (s), Liquid (l), Gas (g) Homogeneous vs. Heterogeneous Mixtures Organization of atoms/molecules: atoms/elements  molecules/compounds Extensive vs. Intensive Properties Varies with amount (extensive) or does not vary with amount (intensive) © Copyright 1998-2007 R.J. Rusay

11. Organization of Matter leptons up,down, strange, charm, bottom, top muons, tau, neutrinos Classification of Matter

13. The effects of a magnet on iron: filings in a mixture and atoms in a molecule.

14. Types of Mixtures  Mixtures have variable composition of two or more components.  A homogeneous mixture is a solution (for example, vinegar: water + acetic acid, or steel & bronze: solid metals)  A heterogeneous mixture is, to the naked eye, clearly not uniform (for example, a bottle of ranch dressing with two layers: water + oil, or two solids: iron and sulfur)

15. Element: A substance that cannot be broken into simpler substances by chemical means, eg. Fe, Iron or S 8 Sulfur Compound: A substance with a constant composition that can be broken down into elements only by chemical processes,eg. FeS, Iron (II) sulfide Elements & Compounds

17. QUESTION Is a cup of coffee a homogeneous solution or a compound? Which of the following agrees with your reasoning? 1.The coffee in the cup is a homogeneous solution because it contains the same components throughout, but there are many compounds dissolved to make coffee. 2. The coffee in the cup is a compound because it has a set ratio of components that make it the same throughout. 3.The coffee in the cup is both a compound and a solution. It looks the same throughout like a true solution, yet it always has the same amount of each component. 4. The coffee in the cup is a heterogeneous solution not homogeneous because it contains distinct, different compounds dissolved to make coffee.

18. Measurement & Units (SI units & common units in General Chemistry) Quantitative vs. Qualitative MASS (Chem: gram; SI: kg) LENGTH (Chem: cm & others; SI: m) TEMPERATURE (Celsius & Kelvin; SI: K) VOLUME (Chem: mL; SI: Liter) CHEMICAL AMOUNT: Mole (mol) © Copyright 1998-2007 R.J. Rusay

19. Units of Measure

20. Mass and Volume Measurement

21. Mass Determination (Weighing Devices: Balances)

22. Volumes of regular shapes h V = l x w x h V = s 3

23. Volume

24. Liquid Measurement Tools

25. Numbers & Measurement The Importance of Units  Measurement - quantitative observation consisting of 2 parts Part 1 - numberPart 1 - number Part 2 - unitPart 2 - unit  Examples: 20 grams20 grams 6.63    joules / second6.63    joules / second

26. Scale: Size & Comparison  Macroscopic vs. Microscopic  IBM financed Video: http://www.wordwizz.com/imagendx.htm How would you compare your lifespan?.. to that of a dog? ….to the age of the earth?…How about the age of mankind to that of all life?....the age of industrialized mankind to the age of mankind?

27. Graphic Comparisons

28. Powers of Ten: Scale

29. Shorthand Prefixes Language describes scale (prefixes) How many zeroes does yotta yotta yotta have?

30. Commonly used prefixes in Chemistry These should be known from memory.

31. Commonly used prefixes in Chemistry The dark ones should be known from memory.

32. QUESTION Conveniently, a U.S. nickel has a mass of approximately 5 grams. If you had one dollar’s worth of nickels what would be the mass of the nickels in milligrams? 1.100 milligrams 2.50 milligrams 3.1,000 milligrams 4.100,000 milligrams 1000 milligrams (mg) = 1 gram (g)

33. Scientific Notation & Significant Digits Scientific Notation: A single digit followed by a decimal and a power of ten. Examples: 2,345 mL and 0.002340 g 2,345 mL = 2.345 x 10 3 mL 0.002340 g = 2.340 x 10 -3 g

34. Numbers Expressing a number correctly is determined by the method used in the measurement! How many numbers should I include? Significant Digits (Figures) Consider: the exactness of the measured value Short Hand expression translates the number: Scientific Notation © Copyright 1998-2007 R.J. Rusay

35. What is the length of the rod? Different measurement tools give different numbers: Which ruler is better? ? cm 4.2 - 4.3cm 4.24 - 4.25cm

36. What does each line represent? 1 mL What can be estimated? O.1 mL

37. Measurement Assignment http://chemconnections.llnl.gov/General/Chem120/volume1.htm http://chemconnections.llnl.gov/General/Chem120/volume1.htm

38. Temperature Scales Relative to Water

39. QUESTION Dr. R. walks into class and claims, “It is very cold in here today. It feels like 242 K.” If that were the temperature, would you agree that you would feel cold? What would that be in Celsius degrees? 1.I agree, that would be 31°C. 2.I agree, that would be – 31°C. 3.I do not agree, that would be 31°C. 4.I agree, that would be –31.15°C.

40. Temperature

41. Precision & Accuracy QUESTIONS: 1) Rank the images from best to worst precision. 2) Rank the images from best to worst accuracy.

42. QUESTION Two Chem 120 students are each drinking a soft drink after class. The volumes of both containers are respectively listed as 375 milliliters. Philip remarks that the law requires bottlers to be very precise. Susan correctly responded: 1.If precision were the only requirement, bottlers could claim any volume as long as it was always very nearly the same volume. 2.Since precision is a requirement, bottlers have to get exactly 375 mL in every can. 3.Bottlers must have a precise average of all of the containers in a case of soft drinks equal to 375 mL. 4. If there were a difference of no more than +/- 1 mL between containers, the bottlers can sell their beverage.

43. Precision & Accuracy Numerical Data

44. QUESTION A) Precision: a > c > bB) Precision: b > c > a C) Precision: a = b > cD) Precision: a > b > c Average a)b)c) 8.38 7.99 average deviation a)b)c) +/- 0.57+/- 0.03+/- 0.04 Rank the relative precision of the three sets of data: a), b) and c).The accepted value is 8.08.

45. QUESTION A) Accuracy: a > c > bB) Accuracy: b > c > a C) Accuracy: c > a = b D) Accuracy: a = b > c Average a)b)c) 8.38 7.99 average deviation a)b)c) +/- 0.57+/- 0.03+/- 0.04 Rank the relative accuracy of the three sets of data: a), b) and c).The accepted value is 8.08.

46. Reporting Numbers Rules for Significant Digits (Figures)  Nonzero integers always count as significant figures.  3456 g has how many sig figs?  4 sig figs. Expressed in scientific notation?Expressed in scientific notation? 3.456 x 10 3 g

47. Reporting Numbers Rules for Significant (Digits) Figures  Exact  Exact numbers (unit, conversion or scale factors) factors) can have an infinite number of significant figures. 1 1 1 1 liter = 1,000. 1,000. ml, exactly 1 1 1 1 inch = 2.54 2.54 cm, exactly

48. Systematic Problem Solving Dimensional/Unit Analysis How many mL of milk are in a1/2 gallon carton? ? mL 0.50 gal 1 gal = 4 qt 1 qt = 946 mL 0.50 gal | 1 qt | 946 mL | 4 gal | 1 qt | 4 gal | 1 qt = ? mL

49. Complete the following Units & Conversions 13,000,000,000 yrs.________________ __? gigayears Number Scientific Notation Named unit ___________ mL ______________ mL 0.546 Liters ____________ kg__8.45 x 10 -1 kg___ _? grams__

50. Zeros  Leading zeros do not count as significant figures.  0.0486 mL has how many sig figs?  3 sig figs. Number expressed in scientific notation?Number expressed in scientific notation? 4.86 x 10 -2 mL

51. Zeros  Captive zeros always count as significant figures.  16.07 cm has how many sig figs?  4 sig figs.  Number expressed in scientific notation? 1.607 x 10 1 cm

52. Zeros  Trailing zeros are significant only if the number contains a decimal point.  9.300 kg has how many sig figs?  4 sig figs. Number expressed in scientific notation?Number expressed in scientific notation? 9.300 kg

53. QUESTION Which one of the following does NOT represent a result with four significant digits? 1.0.07100 2.0.7100 3.0.7010 4.0.0710

54. Mathematics & Arithmetic Relative to method(s) of measurement Short Hand expression: Scientific Notation Numbers : How many to include? Quantitative vs. Qualitative Addition/Subtraction...... Multiplication/Division..... What is “significant”?..... Rounding Off http:dbhs.wvusd.k12.ca.us/SigFigsFable.html © Copyright 1998-2007 R.J. Rusay

55. Computational Rules Addition/Subtraction: Answer expressed to the least number of decimal places of the figures in the process Multiplication/Division: Answer expressed to the least number of significant figures © Copyright 1998-2007 R.J. Rusay

56. Addition  Four students were each asked to measure a piece of wire and provide a total length for the four pieces.  Report the result correctly:

57. QUESTION If you were unloading a 23.50 kg box of books from your car and a “friend” added two more 482 gram chemistry books, how much in kg and using the rules for significant digits, would you be lifting? 1.23.98 kg 2.24.464 kg 3.24.46 kg 4.24.5 kg

58. Mathematical Processes:  Provide correct answers assuming each value (unit omitted) is written with the correct number of sig figs:

59. QUESTION The average mass of a certain brand of vitamin C tablets is 253 mg. What is the mass of three such tablets rounded to the proper number of significant digits? 1.0.760 grams 2.0.759 grams 3.0.7590 grams 4.0.253 grams

60. Conversion Factor Method (Dimensional Analysis) Qualitative Descriptions vs. Quantitative Use exact numbers / “scale factor” UNITS A Bookkeeping Method: Example ___ ft___in --------> ? m (1 ft = 12 in; 2.54 cm = 1 in; 100 cm = 1 m) ___ft x 12 in/ft + ___in = ___in ___in x 2.54 cm/in x 1 m/100cm = ___m © Copyright 1998-2007 R.J. Rusay

61. Density http://www.density.com/what.htm http://www.density.com/what.htm Density = Mass / Volume [g/mL or g/cm 3 ; g/L] Least dense man-made solid substance: Aerogel, D = 3.025 x 10 -3 g/cm 3 http://eetd.lbl.gov/ECS/aerogels/aerogels.htm http://stardust.jpl.nasa.gov/spacecraft/aerogel.html D air = 1.22 x 10 -3 g/cm 3 (1.22 g/L) Densest known substance: a White Dwarf http://antwrp.gsfc.nasa.gov/apod/ap961203.html 1.0 teaspoon = 3.0 T; D = ? g/cm 3 (1 tsp = 4.93 mL; 1 mL = 1 cm 3 ) © Copyright 1998-2007 R.J. Rusay

62. QUESTION The volume of a sample can be obtained from its density and mass. If the mass of a sample of acid from a battery were 5.00 grams and the density was 1.2 g/mL, what would you report in mL and with the proper number of significant digits, as the sample volume? 1.6.0 mL 2.6.00 mL 3.4.2 mL 4.4.17 mL

63. QUESTION Which would provide more grams of NaCl, sample one with a mass of 2,350 mg, or sample two, a solid with a volume of 2.00 cm 3 ? (The density of solid salt is 2.16 g/cm 3.) Report your choice and report the grams of the more massive sample. 1.Sample two; 1.08 grams 2.Sample two; 4.32 grams 3.Sample one; 2.35 grams 4.Sample one; 2.350 grams

64. Percent A comparison based on normalization to 100. George Washington University: 64 unsealed addressed envelopes with $10 in each were dropped on campus in different classrooms. In economics 18 of 32 were mailed, in business, history and psychology 10 of 32 were mailed. What is the percent for each of the 2 groups of students? © Copyright 1998-2007 R.J. Rusay

65. Percent Continued The Professor conducting the study received 43.75% of the $640 in the mail. How much did he receive? How many of you would mail the envelop presuming no one knows you found it? One student mailed an empty envelop with the return address: Mr. IOU, 1013 Indebted Lane, Bankrupt City, MS (WSJ 1/18/95) © Copyright 1998-2007 R.J. Rusay