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HSTMr. Watson
Chapter 1Chapter 1
Chemistry and
Measurement
HSTMr. Watson
ChemistryChemistry
What is it?Why do we study it?
HSTMr. Watson
Physical States 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
HSTMr. Watson
Modern Chemistry: Modern Chemistry: A Brief GlimpseA Brief Glimpse
HSTMr. Watson
Air Bags: How Do They Work?Air Bags: How Do They Work?
HSTMr. Watson
Science and the Ozone LayerScience and the Ozone Layer
For more information about the Ozone Layer: Ozone Depletion
– http://www.epa.gov/ozone/
Thickness of ozone layer– http://jwocky.gsfc.nasa.gov/teacher/ozone_overhead.html
Memphis: +35 latitude -90 longitude
HSTMr. Watson
MatterMatter
has massmass vs. weightoccupies space
HSTMr. Watson
Scientific MethodScientific MethodExperimentResultsHypothesis
– further experiments– refine the hypothesis
Theory– experiments to test the theory– refine the theory
HSTMr. Watson
Law of Conservation of MassLaw 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.
HSTMr. Watson
Properties of MatterProperties 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.
HSTMr. Watson
Physical PropertyPhysical Property
one that can be observed without changing the substances present in the sample
changes in physical properties of substances
HSTMr. Watson
Chemical PropertyChemical Property
the tendency to react and form new substances
HSTMr. Watson
Chemical ReactionChemical Reaction
reactants undergo chemical change to produce products
sucrose ---> carbon + water
reactant products
HSTMr. Watson
Chemical ReactionChemical Reaction
Reactions are indicated by:evolution of a gaschange of colorformation of a precipitate
HSTMr. Watson
Law of Definite ProportionsLaw of Definite Proportions
All samples of the same pure substance always contain the same elements in the same proportions by weight
HSTMr. Watson
Pure SubstancesPure Substances
Elements
Compounds
HSTMr. Watson
MixturesMixtures
Heterogeneousuneven texture
Homogeneous (Solution)sample uniform throughout
HSTMr. Watson
HSTMr. Watson
Separation of MixturesSeparation of Mixtures
filtrationdistillationchromatography
HSTMr. Watson
FiltrationFiltration
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.
HSTMr. Watson
DistillationDistillation
separation by differences in boiling point (fractional distillation)– distillate– distillation
fractionating column - part of apparatus where separation occurs
HSTMr. Watson
HSTMr. Watson
ChromatographyChromatography
liquid-columnpaperthin-layer (TLC)gasHPLCelectrophoresis (DNA mapping)
HSTMr. Watson
Column ChromatographyColumn Chromatography
HSTMr. Watson
Paper Chromatography of Paper Chromatography of InksInks
HSTMr. Watson
HSTMr. Watson
Uncertainty in MeasurementsUncertainty in Measurements
Accuracy
closeness to true value
vs
Precision
reproducibility
HSTMr. Watson
Accurate and/or Precise?
HSTMr. Watson
Accurate and/or Precise?
HSTMr. Watson
Significant FiguresSignificant FiguresRules 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
HSTMr. Watson
Significant FiguresSignificant FiguresExamples:Examples:
Railroad Track Scale70,000,000 g + 500,000 g
7.00 x 107 g (scientific notation)
7.00 E7 g (engineering notation)
3 significant figures
HSTMr. Watson
Significant FiguresSignificant FiguresExamples:Examples:
Regular Lab Balance 1,000 g + 0.1 g
1.0000 x 103 g5 sig. fig.
400 g + 0.01 g4.0000 x 102 g
5 sig. fig.100 + 0.001 g
1.00000 x 102 g6 sig.fig.
HSTMr. Watson
Rules for MathematicsRules for MathematicsMultiplication and DivisionMultiplication 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.
2 sig.fig.; 3 sig. fig. => 2 sig. fig.4 sig. fig.;
= 2.0 x 102(2075)*(14)
----------------
(144)
HSTMr. Watson
Rules for MathematicsRules for MathematicsAddition and SubtractionAddition 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
HSTMr. Watson
Rules for MathematicsRules for MathematicsAddition and SubtractionAddition 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
HSTMr. Watson
Rules for MathematicsRules for MathematicsAddition and SubtractionAddition 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
HSTMr. Watson
Exact NumbersExact Numbers
conversion factorsshould never limit the number of significant
figures reported in answer
12 inches = 1 foot
HSTMr. Watson
Round OffRound Off
Chemistry is an inexact scienceall physical measurements have some errorthus, there is some inexactness in the last
digit of any numberuse what ever round-off procedure you
choosereasonably close answers accepted
HSTMr. Watson
Measurement and UnitsMeasurement and Units
length - meter
volume - liter
mass - gram
HSTMr. Watson
Important Metric Unit PrefixesImportant Metric Unit Prefixes
deci -- 1/10*
centi -- 1/100*
milli -- 1/1000*
nano -- 1/1,000,000,000
kilo -- 1000*
HSTMr. Watson
LiterLiter1 liter = 1 decimeter3
by definition
where
1 decimeter = 10 centimeters
therefore
1 liter = (10 centimeters)3
or
1 liter =1000 cm3 =1000 mL
HSTMr. Watson
MilliMillimetermeter
1 millimeter = 1/1000 meter
1000 millimeter = 1 meter
1000 mm = 1 m
HSTMr. Watson
NanometerNanometer
1 nanometer = 1/1,000,000,000 meter
1,000,000,000 nanometer = 1 meter
1,000,000,000 nm = 1 m
HSTMr. Watson
LiterLiter
1 liter = 1 decimeter3
1 liter = 1000 milliliters
1 L = 1000 mL
1 mL = 0.001 L
HSTMr. Watson
MilligramMilligram
1 milligram = 1/1000 gram
1 mg = 0.001 g
HSTMr. Watson
KilogramKilogram
1 kilogram = 1000 gram
1 g = 0.001 kg
1 mg = 0.000001 kg
1 kg = 1,000,000 mg
HSTMr. Watson
Conversion of UnitsConversion of Units
1 in = 2.54 cm
HSTMr. Watson
TemperatureTemperature
Scales:FahrenheitRankin
– absolute scale using Fahrenheit size degree
CelsiusKelvin
– absolute scale using Celsius size degree
HSTMr. Watson
HSTMr. Watson
Comparison of Temperature Comparison of Temperature ScalesScales
Fahrenheit Celcius
body temp. 98.6 37.0
comfort temp. 68.0 20.0
bp water 212 100
mp 32 0
bp-mp 180 100
HSTMr. Watson
Temperature RelationshipsTemperature Relationships
C = 100/180 * (F - 32)
F = (180/100)*C + 32
K = C + 273.15
- 40o F = - 40o C
HSTMr. Watson
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%
HSTMr. Watson
DensityDensity
Mass per unit of volumeMass equals volume times densityVolume equals mass divided by density
HSTMr. Watson
Problem Solving by Problem Solving by Factor Label MethodFactor Label Method
state question in mathematical formset equal to piece of data specific to the
problemuse conversion factors to convert units of
data specific to problem to units sought in answer
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
state question in mathematical form
#km
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
set equal to piece of data specific to the problem
#km = 0.200 miles
HSTMr. Watson
ExampleExample
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)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
cancel units
#km = (0.200 miles)
* (5280 ft/mile)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
add another conversion factor
#km = (0.200)*(5280 ft)
*(12 in/ft)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
cancel units
#km = (0.200)*(5280 ft)
*(12 in/ft)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
#km = (0.200)*(5280)*(12 in)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
add still another conversion factor
#km = (0.200)*(5280)*(12 in)
*(2.54 cm/in)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
cancel units
#km = (0.200)*(5280)*(12 in)
*(2.54 cm/in)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
#km = (0.200)*(5280)*(12)*(2.54 cm)
HSTMr. Watson
ExampleExample
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)
HSTMr. Watson Dr. S. M. Condren
ExampleExample
How many kilometers are there in 0.200 miles?
cancel units
#km = (0.200)*(5280)*(12)*(2.54 cm)
*(1 m/100 cm)
HSTMr. Watson Dr. S. M. Condren
ExampleExample
How many kilometers are there in 0.200 miles?
#km = (0.200)*(5280)*(12)*(2.54)
*(1 m/100)
HSTMr. Watson
ExampleExample
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)
HSTMr. Watson
ExampleExample
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)
HSTMr. Watson
ExampleExample
How many kilometers are there in 0.200 miles?
#km = (0.200)*(5280)*(12)*(2.54)
*(1/100)*(1 km/1000)
HSTMr. Watson
ExampleExample
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.
HSTMr. Watson
ExampleExample
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