1. Scientific & Chemical Fundamentals
Dr. Ron Rusay
Spring 2008
© Copyright R.J. Rusay

2. 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 R.J. Rusay

3. 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

4. Science & The Scientific Method

5. Law vs. Theory
Figure: 01-15

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.
HMClass Prep: Figure 1.5

7. ANSWER
Choice 2 follows the agreed-upon distinction between a theory and a law. Observations that consistently agree and provide the same result in a variety of systems become “Laws.” Theories are attempts to offer human interpretations and explanations about what was observed. Therefore, we should continue calling the summary about attractions the Law of Gravitation.
Section 1.2: The Scientific Method

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

9. 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 R.J. Rusay

10. 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
CAS Registry : ~12,000 in 1907; > 31 million June 2007
Today ~ 500 new molecules are added / hr

11. 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)
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12. Observations of Physical & Chemical Properties

13. States of Matter

14. Organization of Matter
Classification of Matter
leptons
Up,down, strange, charm, bottom, top

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

16. Figure: 01-09

17. Using Physical & Chemical Properties: Distinguishing a Compound & a Mixture

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

19. 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)

20. Elements & Compounds
Element: A substance that cannot be broken into simpler substances by chemical means, eg. Fe, Iron or S8 Sulfur
Compound: A substance with a constant composition that can be broken down into elements only by chemical processes,eg. FeS, Iron (II) sulfide

21. Figure: 01-05a-d

22. Figure: 01-06

23. Figure: 01-10

24. Figure: 01-01

25. 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.

26. ANSWER
Choice 1 provides the best reasoning. The coffee in the cup is a homogeneous mixture of components, making it a solution. The amount of each component can vary greatly from coffee bean to coffee bean. Compounds do not have a variable composition like solutions.
Section 1.9: Classification of Matter

27. 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 R.J. Rusay

28. Units of Measure

29. Mass and Volume Measurement

30. Mass Determination (Weighing Devices: Balances)

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

32. Volume

33. Liquid Measurement Tools

34. Figure: 01-20

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

36. Scale: Size & Comparison
Macroscopic vs. Microscopic
IBM financed Video:
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?

37. Graphic Comparisons

38. Powers of Ten: Scale

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

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

41. Commonly used prefixes in Chemistry
Figure: TB01-T05
Attosecond spectroscopy = x seconds
Science, 317, , (2007)
“The Electron Stopwatch”

42. 1000 milligrams (mg) = 1 gram (g)
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?
milligrams
2. 50 milligrams
3. 1,000 milligrams
4. 100,000 milligrams
HMClass Prep: Table 1.2
1000 milligrams (mg) = 1 gram (g)

43. ANSWER
Choice 4 shows the correct conversion. After determining that 20 nickels make up one dollar, then one dollar’s worth of nickels would have a mass of 100 grams. Next, the conversion between grams and milligrams can be performed by multiplying by 1,000 (because there are 1,000 milligrams per gram.)
Section 1.3: Units of Measurement

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

45. Numbers How many numbers should I include?
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 R.J. Rusay

46. What is the length of the rod?
Different measurement tools give different numbers:
Which ruler is better?
? cm cm
? cm cm

47. What is the diameter of a circle?
All measuring devices are not the same, and the values (numbers) that come from them indicate their limitations.
Is there a better instrument to use other than a ruler?

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

49. Measurement Assignment http://chemconnections. llnl

50. Temperature Scales Relative to Water

51. “Normal” Body Temperature

52. 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.
HMClass Prep: Figure 1.12

53. ANSWER
Choice 2 provides a correct (very) cold temperature. The formula to use is K = °C However this must be rearranged slightly to yield K – = °C. Since this is a subtraction, the correct value would have no numbers beyond the decimal point because 242 does not have numbers beyond the decimal point.
Section 1.7: Temperature

54. Temperature

55. Precision & Accuracy QUESTIONS:
1) Rank the images from best to worst precision.
c > b > a
2) Rank the images from best to worst accuracy.
c > a > b

56. 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 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.
HMClass Prep: Figure 1.10

57. ANSWER
Choice 1 best fits what scientists define as precise. High precision measurements may have closeness to a set goal (such as 375 mL in a can) but precision always means closeness within a set of measurements. If the volumes of 100 containers were within a range of 294 to 295 mL the volumes would be precise, but not accurately 375 mL.
Section 1.4: Uncertainty in Measurement

58. Precision & Accuracy Numerical Data

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

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

61. 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?
3.456 x 10 3 g

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

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

64. Complete the following Units & Conversions
Number Scientific Notation Named unit
1.3 x 1010 yrs
13,000,000,000 yrs. ________________ __? gigayears
13 Gyrs
546
5.46 X 10 2
___________ mL ______________ mL Liters
0.546 L
0.845
____________ kg __8.45 x kg___ _? grams__
845 g

65. Zeros Leading zeros do not count as significant figures.
mL has how many sig figs?
3 sig figs.
Number expressed in scientific notation?
4.86 x mL

66. 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

67. 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?
9.300 kg

68. QUESTION
Which one of the following does NOT represent a result with four significant digits?
HMClass Prep: Rules for Significant Figures

69. ANSWER
Choice 4 only has three significant digits. Note that the lone zero in front of the decimal point is not based on any measurement and the next zero serves only as a place holder not as a measurement.
Section 1.5: Significant Figures and Calculations

70. 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
© Copyright R.J. Rusay

71. 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 R.J. Rusay

72. 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: cm

73. QUESTION
If you were unloading a 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? kg kg kg kg
HMClass Prep: Table 1.2

74. ANSWER
Choice 3 provides both the conversion and proper number of significant digits. Consider that the 482 grams of mass must be doubled (to include both books) and that 482 grams is kg. When adding two measurements always report your answer to the same number of decimal places as the least precise measurement used in the calculation. In this case the answer should be reported to the hundredths place.
Section 1.5: Significant Figures and Calculations

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

76. 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?
grams
grams
grams
grams
HMClass Prep: Table 1.2

77. ANSWER
Choice 2 provides three significant digits (and accurate math work). 3 tablets  253 milligrams = 759 milligrams, then dividing by 1,000 converts the milligrams to grams. Note the three is a count of the number of objects, not a measured quantity and 759 retains the same number of significant digits as the least found in related measurements.
Section 1.5: Significant Figures and Calculations

78. 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 5 5 5 5 65
1.651 65
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79. Density Density = Mass / Volume [g/mL or g/cm3; g/L]
Least dense man-made solid substance: Aerogel, D = x 10-3 g/cm3
Dair = 1.22 x 10-3 g/cm3 (1.22 g/L)
Densest known substance: a White Dwarf
1.0 teaspoon = 3.0 T; D = ? g/cm3 (1 tsp = 4.93 mL; 1 mL = 1 cm3 )
© Copyright R.J. Rusay

80. 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 cm3? (The density of solid salt is 2.16 g/cm3.) 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; grams

81. ANSWER
Choice 2 provides the accurate mass for 2.00 cm3 of salt. This mass is larger than the 2.35 gram sample. Be sure to solve for the mass of a sample from its density and volume by multiplying 2.00 cm3 × 2.16 g/cm3.
Section 1.8: Density

82. Densities of Various Common Substances* at 20° C

83. 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? mL mL mL mL

84. ANSWER
Choice 3 shows the correct volume for 5.00 grams of this sample. First, be sure to use the correct solution for solving volume from mass and density (V = m/D). Then recall that the significant digit pattern for dividing measurements is to retain the same number of significant digits in the answer as the least number in any of the related measurements.
Section 1.8: Density

85. 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 R.J. Rusay

86. 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 R.J. Rusay