HSTMr. Watson Chapter 1 Chemistry and Measurement.

HSTMr. Watson

Chapter 1Chapter 1

Chemistry and

Measurement

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ChemistryChemistry

What is it?Why do we study it?

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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

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Modern Chemistry: Modern Chemistry: A Brief GlimpseA Brief Glimpse

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Air Bags: How Do They Work?Air Bags: How Do They Work?

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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

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MatterMatter

has massmass vs. weightoccupies space

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Scientific MethodScientific MethodExperimentResultsHypothesis

– further experiments– refine the hypothesis

Theory– experiments to test the theory– refine the theory

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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.

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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.

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Physical PropertyPhysical Property

one that can be observed without changing the substances present in the sample

changes in physical properties of substances

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Chemical PropertyChemical Property

the tendency to react and form new substances

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Chemical ReactionChemical Reaction

reactants undergo chemical change to produce products

sucrose ---> carbon + water

reactant products

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Chemical ReactionChemical Reaction

Reactions are indicated by:evolution of a gaschange of colorformation of a precipitate

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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

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Pure SubstancesPure Substances

Elements

Compounds

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MixturesMixtures

Heterogeneousuneven texture

Homogeneous (Solution)sample uniform throughout

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Separation of MixturesSeparation of Mixtures

filtrationdistillationchromatography

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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.

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DistillationDistillation

separation by differences in boiling point (fractional distillation)– distillate– distillation

fractionating column - part of apparatus where separation occurs

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ChromatographyChromatography

liquid-columnpaperthin-layer (TLC)gasHPLCelectrophoresis (DNA mapping)

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Column ChromatographyColumn Chromatography

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Paper Chromatography of Paper Chromatography of InksInks

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Uncertainty in MeasurementsUncertainty in Measurements

Accuracy

closeness to true value

vs

Precision

reproducibility

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Accurate and/or Precise?

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Accurate and/or Precise?

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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

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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

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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.

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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)

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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

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4.371 302.5 -------- 306.8

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4.371 (I truncate extra data) 302.5 -------- 306.8

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Exact NumbersExact Numbers

conversion factorsshould never limit the number of significant

figures reported in answer

12 inches = 1 foot

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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

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Measurement and UnitsMeasurement and Units

length - meter

volume - liter

mass - gram

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Important Metric Unit PrefixesImportant Metric Unit Prefixes

deci -- 1/10*

centi -- 1/100*

milli -- 1/1000*

nano -- 1/1,000,000,000

kilo -- 1000*

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LiterLiter1 liter = 1 decimeter3

by definition

where

1 decimeter = 10 centimeters

therefore

1 liter = (10 centimeters)3

or

1 liter =1000 cm3 =1000 mL

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MilliMillimetermeter

1 millimeter = 1/1000 meter

1000 millimeter = 1 meter

1000 mm = 1 m

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NanometerNanometer

1 nanometer = 1/1,000,000,000 meter

1,000,000,000 nanometer = 1 meter

1,000,000,000 nm = 1 m

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LiterLiter

1 liter = 1 decimeter3

1 liter = 1000 milliliters

1 L = 1000 mL

1 mL = 0.001 L

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MilligramMilligram

1 milligram = 1/1000 gram

1 mg = 0.001 g

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KilogramKilogram

1 kilogram = 1000 gram

1 g = 0.001 kg

1 mg = 0.000001 kg

1 kg = 1,000,000 mg

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Conversion of UnitsConversion of Units

1 in = 2.54 cm

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TemperatureTemperature

Scales:FahrenheitRankin

– absolute scale using Fahrenheit size degree

CelsiusKelvin

– absolute scale using Celsius size degree

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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

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Temperature RelationshipsTemperature Relationships

C = 100/180 * (F - 32)

F = (180/100)*C + 32

K = C + 273.15

- 40o F = - 40o C

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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%

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DensityDensity

Mass per unit of volumeMass equals volume times densityVolume equals mass divided by density

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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

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ExampleExample

How many kilometers are there in 0.200 miles?

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ExampleExample


state question in mathematical form

#km

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ExampleExample


set equal to piece of data specific to the problem

#km = 0.200 miles

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ExampleExample


use conversion factors to convert units of data specific to problem to units sought in answer

#km = (0.200 miles)

* (5280 ft/mile)

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ExampleExample


cancel units

#km = (0.200 miles)

* (5280 ft/mile)

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ExampleExample


add another conversion factor

#km = (0.200)*(5280 ft)

*(12 in/ft)

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ExampleExample


cancel units

#km = (0.200)*(5280 ft)

*(12 in/ft)

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ExampleExample


#km = (0.200)*(5280)*(12 in)

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ExampleExample


add still another conversion factor

#km = (0.200)*(5280)*(12 in)

*(2.54 cm/in)

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ExampleExample


cancel units

#km = (0.200)*(5280)*(12 in)

*(2.54 cm/in)

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ExampleExample


#km = (0.200)*(5280)*(12)*(2.54 cm)

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ExampleExample



#km = (0.200)*(5280)*(12)*(2.54 cm)

*(1 m/100 cm)

HSTMr. Watson Dr. S. M. Condren

ExampleExample


cancel units

#km = (0.200)*(5280)*(12)*(2.54 cm)

*(1 m/100 cm)

HSTMr. Watson Dr. S. M. Condren

ExampleExample


#km = (0.200)*(5280)*(12)*(2.54)

*(1 m/100)

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ExampleExample



#km = (0.200)*(5280)*(12)*(2.54)

*(1 m/100)*(1 km/1000 m)

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ExampleExample


cancel units

#km = (0.200)*(5280)*(12)*(2.54)

*(1 m/100)*(1 km/1000 m)

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ExampleExample


#km = (0.200)*(5280)*(12)*(2.54)

*(1/100)*(1 km/1000)

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ExampleExample


solve mathematics

#km = (0.200)*(5280)*(12)*(2.54)

*(1/100)*(1 km/1000)

= 0.322 km

3 sig. fig.

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ExampleExample


solve mathematics

#km = (0.200)*(5280)*(12)*(2.54) *(1/100)*(1 km/1000) = 0.322 km

3 sig. fig. exact numbers

HSTMr. Watson Chapter 1 Chemistry and Measurement.

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