1. Modern Chemistry Chapter 2 Measurements and Calculations
Sections 1 - 3
Scientific Method
Units of Measurement
Using Scientific Measurements

2. Chapter 2 Section 1 Scientific Method pages 29-32
System
Hypothesis
Model
Theory
Quantity SI
Weight
Derived unit
Volume
Density
Conversion Factor
Dimensional analysis
Accuracy
Precision
Percentage error
Significant figures
Scientific notation
Directly proportional
Inversely proportional
Chapter Vocabulary
Chapter 2 Section 1 Scientific Method pages 29-32

3. Chapter 2 Section 1 Scientific Method pages 29-32

4. Chapter 2 Section 1 Scientific Method pages 29-32
A logical approach to solving problems by
OBSERVING AND COLLECTING DATA
FORMULATING HYPOTHESIS
TESTING HYPOTHESIS
FORMULATING THEORIES
that are supported by data.
Not a fixed series of steps.
Chapter 2 Section 1 Scientific Method pages 29-32

5. Scientific Method Image
p. 31
Chapter 2 Section 1 Scientific Method pages 29-32

6. Scientific Method Animation
Chapter 2 Section 1 Scientific Method pages 29-32

7. Observation and Collecting Data
What are we studying?
A system is a specific portion of matter
in a given region of space
that has been selected for study
during an experiment or observation.
Chapter 2 Section 1 Scientific Method pages 29-32

8. Observation and Collecting Data
use of senses to obtain information
Qualitative – descriptive
Quantitative – numeric
Organize data and observations into tables and/or graphs.
Chapter 2 Section 1 Scientific Method pages 29-32

9. Organizing Data into a Graph
Chapter 2 Section 1 Scientific Method pages 29-32

10. Qualitative and Quantitative Observation Animation
Chapter 2 Section 1 Scientific Method pages 29-32

11. Formulating Hypothesis
Generalizations about data or observations can be used to make a hypothesis
A hypothesis is a testable statement
Often in an if-then statement
A prediction that is the basis for testing by experiment
Chapter 2 Section 1 Scientific Method pages 29-32

12. Chapter 2 Section 1 Scientific Method pages 29-32
Hypothesis Animation
Chapter 2 Section 1 Scientific Method pages 29-32

13. Chapter 2 Section 1 Scientific Method pages 29-32
Testing Hypothesis
Controls – conditions that remain constant (controlled variables)
Variable – any condition that changes
Driven by the hypothesis
Test only one variable at a time
Identify variables to be held constant
Chapter 2 Section 1 Scientific Method pages 29-32

14. Chapter 2 Section 1 Scientific Method pages 29-32
Theorizing
When data from experiments support a hypothesis a theory and model are constructed
A model in science is
more than a physical object.
It is often an explanation of
how phenomena occur and
how data or events are related
Chapter 2 Section 1 Scientific Method pages 29-32

15. Chapter 2 Section 1 Scientific Method pages 29-32
Model Animation
Chapter 2 Section 1 Scientific Method pages 29-32

16. Chapter 2 Section 1 Scientific Method pages 29-32
Theorizing
Models are a part of a theory.
A theory is
a broad generalization
that explains
a body of facts or phenomena.
not a fact; explains facts
modified with new discoveries
Chapter 2 Section 1 Scientific Method pages 29-32

17. Reading Notes #7-15 pages 33-43
Section 1 Homework
Reading Notes #7-15 pages 33-43
Chapter 2 Section 1 Scientific Method pages 29-32

18. Chapter 2 Section 2 Units of Measurements pages 33-43

19. Chapter 2 Section 2 Units of Measurements pages 33-43
QUANTITY
UNIT
STANDARD
Length
Foot
The king’s foot
Mass
Kilogram
Kg prototype
a.m.u.
1/12th of a carbon-12 atom
Something that has magnitude, size or amount
Objects or natural phenomena that are of constant value, easy to preserve and reproduce
Chapter 2 Section 2 Units of Measurements pages 33-43

20. Chapter 2 Section 2 Units of Measurements pages 33-43
Common SI Units Table
p. 33*
Chapter 2 Section 2 Units of Measurements pages 33-43

21. Chapter 2 Section 2 Units of Measurements pages 33-43
SI Measurements
Le Systeme’ International d’Unites
not 75,000 use spaces not commas
Chapter 2 Section 2 Units of Measurements pages 33-43

22. Chapter 2 Section 2 Units of Measurements pages 33-43
Base SI Units Table
p. 34
Chapter 2 Section 2 Units of Measurements pages 33-43

23. Chapter 2 Section 2 Units of Measurements pages 33-43
SI Base Units
Comparing Mass and Weight
Mass is the measure of the amount of mater in an object.
Unit = kg
Weight is the measure of the gravitational pull on matter
Unit = N (newtons)
Dependant on gravity
Chapter 2 Section 2 Units of Measurements pages 33-43

24. Chapter 2 Section 2 Units of Measurements pages 33-43
SI Prefixes
giga G
1 Gm = 1 x 109 m
mega M
1 Mm = 1 x 106 m
kilo k
1 km = 1000 m
hecto h
1 hm = 100 m
deka da
1 dam = 10 m
1 m = 1 meter
deci d
1 dm = 0.1 m
centi c
1 cm = 0.01m
milli m
1 mm = 0.001m
micro μ
1 μm = 1 x 10-6 m
nano n
1 nm = 1 x m
Chapter 2 Section 2 Units of Measurements pages 33-43

25. Chapter 2 Section 2 Units of Measurements pages 33-43
SI Conversions Image
p. 40*
Chapter 2 Section 2 Units of Measurements pages 33-43

26. Chapter 2 Section 2 Units of Measurements pages 33-43
Derived SI Units
Derived Units – a combination of SI units
Example 1 kg/m∙sec2 = 1 pascal (Pa)
Volume – the amount of space occupied by an object
L x W x H = 1m x 1m x 1m = 1m3
1dm x 1dm x 1dm = 1dm3 = 1 liter
1cm x 1cm x 1cm = 1cm3 = 1 mL
Chapter 2 Section 2 Units of Measurements pages 33-43

27. Chapter 2 Section 2 Units of Measurements pages 33-43
Derived Units Table
p. 36
Chapter 2 Section 2 Units of Measurements pages 33-43

28. Chapter 2 Section 2 Units of Measurements pages 33-43
Density
The ratio of mass to volume
D = M / V
Unit = kg/m3 or g/cm3 = g/mL
A characteristic physical property
Can be used to identify a substance
Varies with temperature
Chapter 2 Section 2 Units of Measurements pages 33-43

29. Chapter 2 Section 2 Units of Measurements pages 33-43
Density Table
p. 38
Chapter 2 Section 2 Units of Measurements pages 33-43

30. Density Formula Animation
Chapter x Section x Section title pages xx-xx

31. Chapter 2 Section 2 Units of Measurements pages 33-43
Density
What is the density of a block of marble that occupies 310 cm3 and has a mass of 853 g?
Diamond has a density of 3.26g/cm3. What is the mass of a diamond that has a volume of cm3?
What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given the density of mercury is 13.6 g/mL?
p. 40
g/cm g mL
Chapter 2 Section 2 Units of Measurements pages 33-43

32. Chapter 2 Section 2 Units of Measurements pages 33-43
Conversion Factors
A ratio derived from the equality between two different units that can be used to convert from one unit to another
Chapter 2 Section 2 Units of Measurements pages 33-43

33. Chapter 2 Section 2 Units of Measurements pages 33-43
Conversion Factors
Conversion factors always equal 1.
The numerator is equal to the denominator.
4 quarters
1 dollar
= 1
1 kilogram
1000 grams
= 1
12 inches
1 foot
= 1
Chapter 2 Section 2 Units of Measurements pages 33-43

34. Conversion Factors Animation
Chapter 2 Section 2 Units of Measurements pages 33-43

35. Chapter 2 Section 2 Units of Measurements pages 33-43
Dimensional Analysis
A mathematical technique that allows you to use units to solve a problem involving measurements
Chapter 2 Section 2 Units of Measurements pages 33-43

36. Dimensional Analysis wanted unit # given unit = # wanted unit x
Put in numbers to make the numerator equal to the denominator
= # wanted unit x
given unit
Chapter 2 Section 2 Units of Measurements pages 33-43

37. Chapter 2 Section 2 Units of Measurements pages 33-43
Dimensional Analysis x x x x =
Arrange the units so that all cancel out except the last one, which should be the one you want.
Chapter 2 Section 2 Units of Measurements pages 33-43

38. Using Conversion Factors Image
p. 40*
Chapter 2 Section 2 Units of Measurements pages 33-43

39. Chapter 2 Section 2 Units of Measurements pages 33-43
Dimensional Analysis
How many seconds in one week?
Chapter 2 Section 2 Units of Measurements pages 33-43

40. Chapter 2 Section 2 Units of Measurements pages 33-43
Dimensional Analysis
Express a length of m in centimeters and in kilometers.
Express a mass of mg in grams.
p. 40
cm and km g
Chapter 2 Section 2 Units of Measurements pages 33-43

41. Using Scientific Measurements
Section 3
Using Scientific Measurements
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

42. Accuracy and Precision
Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured
Precision refers to the closeness of a set of measurements of the same quantity made the same way.
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

43. Accuracy & Precision Darts Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

44. Accuracy and Precision Image
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

45. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Percent Error
High percent error = low accuracy
Negative? Experimental is too low
Positive? Experimental is too high
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

46. Percent Error Formula Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

47. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Percent Error
Express a length of m in centimeters and in kilometers.
Express a mass of mg in grams.
p. 40
cm and km g
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

48. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Errors in Measurement
Skill of the measurer
Limitation of instruments
Estimation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

49. Measuring Liquids & Meniscus Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

50. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
certain
estimated
Plus or minus one of the estimated decimal places
p. 46
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

51. Affectionately called “sig. figs.”
SIGNIFICANT
FIGURES
SIGNIFICANT
FIGURES
Affectionately called “sig. figs.”

52. Brought to you by….

53. Nonzero integers always count as significant figures!

54. All the certain number in a measurement plus one estimated figure.
Significant Figures
All the certain number in a measurement plus one estimated figure.

55. There are three classes of zeros.
There are three classes of zeros.
LEADING
TRAILING
CAPTIVE

56. as significant figures.
LEADING ZEROS
These do not count
as significant figures.
0.0025
2.5 x 10-3

57. as significant figures.
CAPTIVE ZEROS
These count
as significant figures.
1.008

58. 100 vs. 100. 1.00 x 102 TRAILING ZEROS These do not count
as significant figures…
unless there is a decimal point.
100 vs. 100.
1.00 x 102

59. 2 atoms of H in H2O EXACT NUMBERS These are determined by counting.
These have infinite significant figures.
2 atoms of H in H2O

60. These answer the question, “What do we round to?”
SIG FIGS IN
CALCULATIONS
These answer the question,
“What do we round to?”
There are two different rules:
Multiplication & Division
Addition & Subtraction

61. A team is only as good as its….
PRECISION
A team is only as good as its….
worst
player
Practice!
Your answer can only be as precise as your least precise (worst) piece of data!

62. MULTIPLICATION & DIVISION
The number of sig figs in the result is the same as the least precise measurement used in the calculation.
13.54g /0.40ml =
34 g/ml
33.85 g/ml

63. ADDITION & SUBTRACTION
The result has the same number of decimal places as the least precise measurement used in the calculation. =
13.86 +

64. In a series of calculations, round at the very end.
Rounding
In a series of calculations,
round at the very end.
LESS THAN
The preceding digit stays the same.
5 & GREATER
The preceding digit is increased by 1. 5

66. Significant Figures Rules Table
p. 47
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

67. Rules for Significant Zeros Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

68. Rounding Rules Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

69. M x 10n Scientific Notation
Greater than or equal to 1 but less than 10
A whole number
A negative exponent means the number is small A positive exponent means the number is large
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

70. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Scientific Notation
What is the volume, in milliliters, of a sample of helium that has a mass of 1.73 x 10-3 g, given that the density is g/L?
What is the density of a piece of metal that has a mass of 6.25 x 105 g and is 92.5cm x 47.3 cm x 85.4 cm?
p. 54
mL g/cm3
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

71. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Scientific Notation
How many millimeters are there in 5.12 x 105 kilometers?
A clock gains second per minutes. How many seconds will the clock gain in exactly six months, assuming exactly 30 days per month?
p. 54
x 1011 mm x 103 sec
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

72. Direct Proportions
Two quantities are directly proportional to each other if dividing on by the other gives a constant value
As Y increases; X increases Y X
= k
Y = k X
The equation for a line! k is the slope.
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

73. Directly Proportional Graph
The line must go through the origin to be directly proportional
p. 55
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

74. Chapter 2 Section 3 Using Scientific Measur. pages 44-57
Inverse Proportions
Two quantities are inversely proportional to each other if their product is constant.
As X increases; Y decreases
X Y = k
produces a curve – a hyperbola
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

75. Inversely Proportional Graph
Chapter 2 Section 3 Using Scientific Measur. pages 44-57

76. Directly Proportional & Inversely Proportional Graph Animation
Chapter 2 Section 3 Using Scientific Measur. pages 44-57