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Chemistry and

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Chapter 1 Chemistry and Measurement – PowerPoint PPT presentation

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Title: Chemistry and


1
Chapter 1
  • Chemistry and
  • Measurement

2
Chemistry
  • What is it?
  • Why do we study it?

3
Physical States
  • solid
  • fixed volume and shape

4
Physical States
  • solid
  • fixed volume and shape
  • liquid
  • fixed volume
  • shape of container, horizontal top surface

5
Physical States
  • solid
  • fixed volume and shape
  • liquid
  • fixed volume
  • shape of container, horizontal top surface
  • gas
  • takes shape and volume of container

6
Physical States
  • solid
  • fixed volume and shape
  • liquid
  • fixed volume
  • shape of container, horizontal top surface
  • gas
  • takes shape and volume of container
  • liquid crystal
  • some characteristics of solid and some of liquid
    states

7
Modern Chemistry A Brief Glimpse
8
Exploring the Nanoworld
To order a kit (Special introductory price, 24
shipped to US addresses) contact the Institute
for Chemical Education
9
Air Bags How Do They Work?
http//whyfiles.news.wisc.edu/032air_bag/how_work.
html
10
Matter
  • has mass
  • mass vs. weight
  • occupies space

11
Scientific Method
  • Experiment
  • Results
  • Hypothesis
  • further experiments
  • refine the hypothesis
  • Theory
  • experiments to test the theory
  • refine the theory

12
Law of Conservation of Mass
  • In an ordinary chemical reaction matter is
    neither created nor destroyed.
  • The sum of the masses of the reactants equals the
    sum of the masses of the products.

13
Properties of Matter
  • Extensive Property
  • depends on specific sample under investigation
  • examples
  • mass and volume
  • Intensive Property
  • identical in all samples of the substance
  • examples
  • color, density, melting point, etc.

14
Physical Property
  • one that can be observed without changing the
    substances present in the sample
  • changes in physical properties of substances

15
Chemical Property
  • the tendency to react and form new substances

16
Chemical Reaction
  • reactants undergo chemical change to produce
    products
  • sucrose ---gt carbon water
  • reactant products

17
Chemical Reaction
  • Reactions are indicated by
  • evolution of a gas
  • change of color
  • formation of a precipitate

18
Law of Definite Proportions
  • All samples of the same pure substance always
    contain the same elements in the same proportions
    by weight

19
Pure Substances
  • Elements
  • Compounds

20
Mixtures
  • Heterogeneous
  • uneven texture
  • Homogeneous (Solution)
  • sample uniform throughout

21
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22
Separation of Mixtures
  • filtration
  • distillation
  • chromatography

23
Filtration
  • separate solids by differences in melting points
  • separate solids by differences in solubility
    (fractional crystallization)
  • mechanical separation such as in Fig. 1.11 page
    13.

24
Distillation
  • separation by differences in boiling point
    (fractional distillation)
  • distillate
  • distillation
  • fractionating column - part of apparatus where
    separation occurs

25
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26
Chromatography
  • liquid-column
  • paper
  • thin-layer (TLC)
  • gas
  • HPLC
  • electrophoresis (DNA mapping)

27
Column Chromatography
28
Paper Chromatography of Inks
29
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30
Uncertainty in Measurements
  • Accuracy
  • closeness to true value
  • vs
  • Precision
  • reproducibility

31
Accurate and/or Precise?
32
Accurate and/or Precise?
33
Significant Figures
  • Rules for determining which digits are
    significant
  • All non-zero numbers are significant
  • Zeros between non-zero numbers are significant
  • Zeros to the right of the non-zero number and to
    the right of the decimal point are significant
  • Zeros before non-zero numbers are not significant

34
Significant FiguresExamples
  • Railroad Track Scale
  • 70,000,000 g
  • 500,000 g
  • 7.00 x 107 g (scientific notation)
  • 7.00 E7 g (engineering notation)
  • 3 significant figures

35
Significant FiguresExamples
  • Regular Lab Balance
  • 1,000 g 0.1 g
  • 1.0000 x 103 g
  • 5 sig. fig.
  • 400 g 0.01 g
  • 4.0000 x 102 g
  • 5 sig. fig.
  • 100 0.001 g
  • 1.00000 x 102 g
  • 6 sig.fig.

36
Rules for MathematicsMultiplication and Division
  • For multiplication and division, the number of
    significant figures used in the answer is the
    number in the value with the fewest significant
    figures.

(2075)(14) ---------------- (144)
2.0 x 102
4 sig. fig.
gt
2 sig.fig.
3 sig. fig.
2 sig. fig.
37
Rules for MathematicsAddition and Subtraction
  • For addition and subtraction, the number of
    significant figures used in the answer is
    determined by the piece of data with the fewest
    number decimal places.
  • 4.371
  • 302.5
  • --------
  • 306.8

38
Rules for MathematicsAddition and Subtraction
  • For addition and subtraction, the number of
    significant figures used in the answer is
    determined by the piece of data with the fewest
    number decimal places.
  • 4.371
  • 302.5
  • --------
  • 306.8

39
Rules for MathematicsAddition and Subtraction
  • For addition and subtraction, the number of
    significant figures used in the answer is
    determined by the piece of data with the fewest
    number decimal places.
  • 4.371 (I truncate extra
    data)
  • 302.5
  • --------
  • 306.8

40
Exact Numbers
  • conversion factors
  • should never limit the number of significant
    figures reported in answer
  • 12 inches 1 foot

41
Round Off
  • Chemistry is an inexact science
  • all physical measurements have some error
  • thus, there is some inexactness in the last digit
    of any number
  • use what ever round-off procedure you choose
  • reasonably close answers accepted

42
Measurement and Units
  • length - meter
  • volume - liter
  • mass - gram

43
Important Metric Unit Prefixes
  • deci -- 1/10
  • centi -- 1/100
  • milli -- 1/1000
  • nano -- 1/1,000,000,000
  • kilo -- 1000

44
Liter
  • 1 liter 1 decimeter3
  • by definition
  • where
  • 1 decimeter 10 centimeters
  • therefore
  • 1 liter (10 centimeters)3
  • or
  • 1 liter 1000 cm3 1000 mL

45
Millimeter
  • 1 millimeter 1/1000 meter
  • 1000 millimeter 1 meter
  • 1000 mm 1 m

46
Nanometer
  • 1 nanometer 1/1,000,000,000 meter
  • 1,000,000,000 nanometer 1 meter
  • 1,000,000,000 nm 1 m

47
Liter
  • 1 liter 1 decimeter3
  • 1 liter 1000 milliliters
  • 1 L 1000 mL
  • 1 mL 0.001 L

48
Milligram
  • 1 milligram 1/1000 gram
  • 1 mg 0.001 g

49
Kilogram
  • 1 kilogram 1000 gram
  • 1 g 0.001 kg
  • 1 mg 0.000001 kg
  • 1 kg 1,000,000 mg

50
Conversion of Units
  • 1 in 2.54 cm

51
Temperature
  • Scales
  • Fahrenheit
  • Rankin
  • absolute scale using Fahrenheit size degree
  • Celsius
  • Kelvin
  • absolute scale using Celsius size degree

52
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53
Comparison of Temperature Scales
54
Temperature Relationships
  • C 100/180 (F - 32)
  • F (180/100)C 32
  • K C 273.15
  • - 40o F - 40o C

55
  • If the temperature of the room goes from 20
    degrees C to 40 degrees C, the ambient thermal
    energy
  • doubles
  • is halved
  • increases by less than 10

56
Density
  • Mass per unit of volume gt d m/V
  • Mass equals volume times density gt m Vd
  • Volume equals mass divided by density gt V m/d

57
Problem Solving by Factor Label Method
  • state question in mathematical form
  • set equal to piece of data specific to the
    problem
  • use conversion factors to convert units of data
    specific to problem to units sought in answer

58
Example
  • How many kilometers are there in 0.200 miles?

59
Example
  • How many kilometers are there in 0.200 miles?
  • state question in mathematical form
  • km

60
Example
  • How many kilometers are there in 0.200 miles?
  • set equal to piece of data specific to the
    problem
  • km 0.200 miles

61
Example
  • How many kilometers are there in 0.200 miles?
  • use conversion factors to convert units of data
    specific to problem to units sought in answer
  • km (0.200 miles)
  • (5280 ft/mile)

62
Example
  • How many kilometers are there in 0.200 miles?
  • cancel units
  • km (0.200 miles)
  • (5280 ft/mile)

63
Example
  • How many kilometers are there in 0.200 miles?
  • add another conversion factor
  • km (0.200)(5280 ft)
  • (12 in/ft)

64
Example
  • How many kilometers are there in 0.200 miles?
  • cancel units
  • km (0.200)(5280 ft)
  • (12 in/ft)

65
Example
  • How many kilometers are there in 0.200 miles?
  • km (0.200)(5280)(12 in)

66
Example
  • How many kilometers are there in 0.200 miles?
  • add still another conversion factor
  • km (0.200)(5280)(12 in)
  • (2.54 cm/in)

67
Example
  • How many kilometers are there in 0.200 miles?
  • cancel units
  • km (0.200)(5280)(12 in)
  • (2.54 cm/in)

68
Example
  • How many kilometers are there in 0.200 miles?
  • km (0.200)(5280)(12)(2.54 cm)

69
Example
  • How many kilometers are there in 0.200 miles?
  • add still another conversion factor
  • km (0.200)(5280)(12)(2.54 cm)
  • (1 m/100 cm)

70
Example
  • How many kilometers are there in 0.200 miles?
  • cancel units
  • km (0.200)(5280)(12)(2.54 cm)
  • (1 m/100 cm)

71
Example
  • How many kilometers are there in 0.200 miles?
  • km (0.200)(5280)(12)(2.54)
  • (1 m/100)

72
Example
  • How many kilometers are there in 0.200 miles?
  • add still another conversion factor
  • km (0.200)(5280)(12)(2.54)
  • (1 m/100)(1 km/1000 m)

73
Example
  • How many kilometers are there in 0.200 miles?
  • cancel units
  • km (0.200)(5280)(12)(2.54)
  • (1 m/100)(1 km/1000 m)

74
Example
  • How many kilometers are there in 0.200 miles?
  • km (0.200)(5280)(12)(2.54)
  • (1/100)(1 km/1000)

75
Example
  • How many kilometers are there in 0.200 miles?
  • solve mathematics
  • km (0.200)(5280)(12)(2.54)
  • (1/100)(1 km/1000)
  • 0.322 km
  • 3 sig. fig.

76
Example
  • How many kilometers are there in 0.200 miles?
  • solve mathematics
  • km (0.200)(5280)(12)(2.54)
  • (1/100)(1 km/1000)
  • 0.322 km
  • 3 sig. fig. exact numbers
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