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Chapter 1
Matter and MeasurementsMatter and Measurements
Wolpa/Advanced Placement Chemistry 2
How to be Successful in Chemistry
Memorize strategies not equations!Memorize strategies not equations! Study a lot!Study a lot! Work ALL the problems.Work ALL the problems. Self-evaluate after test results.Self-evaluate after test results. Make use of Tutorial.Make use of Tutorial. Start a Study GroupStart a Study Group
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Chapter 1: Matter and Measurement
Overview:Overview: The Study of ChemistryThe Study of Chemistry Classifications of MatterClassifications of Matter Properties of MatterProperties of Matter Units of MeasurementUnits of Measurement Uncertainty in MeasurementUncertainty in Measurement Dimensional AnalysisDimensional Analysis Basic Math Concepts (see Appendix A)Basic Math Concepts (see Appendix A)
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Chemistry
The study of matter and the changes it The study of matter and the changes it undergoesundergoes
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Matter
Anything that has mass and occupies Anything that has mass and occupies spacespace
Characterized by physical and chemical Characterized by physical and chemical propertiesproperties
Law of the Conservation of Mass - matter Law of the Conservation of Mass - matter is neither created nor destroyed in is neither created nor destroyed in chemical reactionschemical reactions
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Element
An element is a pure substance composed of one An element is a pure substance composed of one type of atom. type of atom.
An atom is the smallest particle of an element An atom is the smallest particle of an element that retains the chemical properties of the that retains the chemical properties of the element.element.
An element is the most basic form of matter An element is the most basic form of matter under ordinary circumstancesunder ordinary circumstances
Simplest chemical substanceSimplest chemical substance Only a few elements are found in their free state Only a few elements are found in their free state
(nitrogen, oxygen, gold, etc.)(nitrogen, oxygen, gold, etc.)
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Elements and the Periodic Table
Each element is represented by a name and Each element is represented by a name and a symbol. (Periods/groups - alkali metals, a symbol. (Periods/groups - alkali metals, alkaline earth metals, halogens, noble alkaline earth metals, halogens, noble gases) gases)
The first letter is always capitalized the The first letter is always capitalized the second (and third) are never capitalized.second (and third) are never capitalized.
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Compound
A unique substance composed of two or more A unique substance composed of two or more elements that are chemically combined (i.e. joined elements that are chemically combined (i.e. joined intimately, not just mixed together)intimately, not just mixed together)
Pure compounds have definite compositions and Pure compounds have definite compositions and propertiesproperties
Require complex chemical procedures to separate Require complex chemical procedures to separate into simpler substances (elements)into simpler substances (elements)
Compounds include water, table salt, sugar, etcCompounds include water, table salt, sugar, etc
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Properties of Substances
Elements and Compounds are pure substances.Elements and Compounds are pure substances. Properties describe the particular characteristics of Properties describe the particular characteristics of
a substancea substance Pure substances have definite composition and Pure substances have definite composition and
definite, unchanging propertiesdefinite, unchanging properties Physical properties - can be observed without Physical properties - can be observed without
changing the substancechanging the substance Chemical properties - require that the substance Chemical properties - require that the substance
change into anotherchange into another
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Physical States
The three physical states are solid, liquid and gasThe three physical states are solid, liquid and gas solids - have a definite shape and volumesolids - have a definite shape and volume liquid - have a definite volume but not a liquid - have a definite volume but not a
definite shapedefinite shape gas - neither a definite volume or shapegas - neither a definite volume or shape
A substance exists in a particular physical state A substance exists in a particular physical state under defined conditionsunder defined conditions
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Phase Changes
Melting point or freezing pointMelting point or freezing point temperature at which a substance changes from solid to temperature at which a substance changes from solid to
liquidliquid Boiling point or condensation pointBoiling point or condensation point
temperature at which a substance changes from liquid to gastemperature at which a substance changes from liquid to gas
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Density
ratio of the mass of a substance to the volume of ratio of the mass of a substance to the volume of that massthat mass
usually measure in g/mL for solids and liquids; usually measure in g/mL for solids and liquids; g/L for gasesg/L for gases
also a conversion factor relating the mass of a also a conversion factor relating the mass of a substance to it’s volumesubstance to it’s volume
Specific gravity is the ratio of the mass of a Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of watersubstance to the mass of an equal volume of water
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What’s happening?
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Density Calculation
EquationEquation
d=m/Vd=m/V Example: Example:
If an object has a mass of 15.0 g and a If an object has a mass of 15.0 g and a volume of 10cmvolume of 10cm3 3 what’s the objects what’s the objects density?density?
d = 15.0 g/ 10.0 cmd = 15.0 g/ 10.0 cm33 = 1.50 g/cm = 1.50 g/cm33
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Temperature and its Measurement
Temperature - measure of the intensity of Temperature - measure of the intensity of the heat of a substancethe heat of a substance
Thermometer - device to measure Thermometer - device to measure temperaturetemperature
Kelvin - K - SI unit of temperatureKelvin - K - SI unit of temperature Celsius - Celsius - °C - commonly used unit°C - commonly used unit Fahrenheit - °F - only used in USAFahrenheit - °F - only used in USA
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Relationships between temperature scales
F8.1
C1F32)F()C(
273)C()K(
tt
tT
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The Kelvin scale
The idea of negative temperatures is a problem for The idea of negative temperatures is a problem for any mathematical treatment of temperature any mathematical treatment of temperature dependent properties.dependent properties.
It was found that a practical minimum temperature It was found that a practical minimum temperature did exist (absolute zero) which has a value of did exist (absolute zero) which has a value of -273.15-273.15°C°C
This is defined as 0 K (no degree sign)This is defined as 0 K (no degree sign) The Kelvin degree is the same size as the Celsius The Kelvin degree is the same size as the Celsius
degree (K = °C + 273.15)degree (K = °C + 273.15)
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Temperature Scale Comparison
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Chemical Properties
Chemical properties - involve how a Chemical properties - involve how a substance changes into anothersubstance changes into another
Sometimes quite difficult to determineSometimes quite difficult to determine Some examples are burning (as opposed to Some examples are burning (as opposed to
boiling) and color changesboiling) and color changes
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Mixtures
Combinations of two or more substancesCombinations of two or more substances Can be separated by exploiting different physical Can be separated by exploiting different physical
properties (filtration, distillation, crystallization, properties (filtration, distillation, crystallization, chromatography)chromatography)
Have chemical and physical properties that are Have chemical and physical properties that are different from the substances that make them updifferent from the substances that make them up
The percentages by mass of the components of a The percentages by mass of the components of a mixture can be varied continuouslymixture can be varied continuously
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Types of Mixtures
Phase - one physical state with distinct boundaries Phase - one physical state with distinct boundaries and uniform propertiesand uniform properties
Heterogeneous mixture - nonuniform mixture Heterogeneous mixture - nonuniform mixture containing two or more phases with definite containing two or more phases with definite boundaries between the phases (e.g. ice and water)boundaries between the phases (e.g. ice and water)
Homogeneous mixture - same throughout and Homogeneous mixture - same throughout and contains only one phase (substances are mixed at contains only one phase (substances are mixed at the atomic or molecular level)the atomic or molecular level)
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Heterogeneous Vs. Homogeneous Mixtures
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Heterogeneous Vs. Homogeneous Mixtures
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Solutions
A type of homogeneous mixtureA type of homogeneous mixture Usually involves a liquid phase, but can be Usually involves a liquid phase, but can be
solid-solid, liquid-liquid, solid-liquid, etc.solid-solid, liquid-liquid, solid-liquid, etc. The pure substances can be in different The pure substances can be in different
phases but form a homogeneous mixture phases but form a homogeneous mixture (table salt and water, for example)(table salt and water, for example)
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Alloys
important solid solutions of two or more important solid solutions of two or more metalsmetals
dental fillings (silver and mercury)dental fillings (silver and mercury) stainless steel (iron, chromium and nickel)stainless steel (iron, chromium and nickel)
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Mixtures separated by:
FiltrationFiltration: Mixture : Mixture consists of a solid and consists of a solid and liquid; liquid liquid; liquid distributing distributing components between a components between a mobile separated by mobile separated by filtration.filtration.
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Separation of Mixtures cont.
DistillationDistillation: Liquid mixture is boiled; : Liquid mixture is boiled; components in the mixture boil off at components in the mixture boil off at different temperatures.different temperatures.
ChromatographyChromatography: Separates mixtures by : Separates mixtures by and stationary phase.and stationary phase.
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Putting it All Together
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Measurements and Units
Measurement - determines the quantity, Measurement - determines the quantity, dimensions or extent of somethingdimensions or extent of something1.Consist of two parts1.Consist of two parts
a. a numerical quantity (1.23)a. a numerical quantity (1.23)b. a specific unit (meters)b. a specific unit (meters)
Unit - a definite quantity adapted to as a Unit - a definite quantity adapted to as a standard of measurementstandard of measurement
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Features of Measured Quantities
When we measure a number, there are physical When we measure a number, there are physical constraints to the measurementconstraints to the measurement
Instruments and scientists are not perfect, so the Instruments and scientists are not perfect, so the measurement is not perfect (i. e., it has error)measurement is not perfect (i. e., it has error)
The error in the measurement is related to the The error in the measurement is related to the accuracyaccuracy and the and the precisionprecision of the measurement of the measurement
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Accuracy and Precision
Accuracy – how close the measurement is to Accuracy – how close the measurement is to the “true” value (of course we have to know the “true” value (of course we have to know what the “true” value is)what the “true” value is)
Precision - the degree to which the Precision - the degree to which the measurement is reproduciblemeasurement is reproducible
1. expressed through how we write the 1. expressed through how we write the number – significant figuresnumber – significant figures
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Example: Accuracy and Precision
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Equations for Precision and Accuracy1. Precision1. Precision
Percent Relative errorPercent Relative error
% RE = Avg. Dev / Avg Value X 100% RE = Avg. Dev / Avg Value X 100
2. Accuracy2. Accuracy
Absolute ErrorAbsolute Error
% AE = % AE = (True value-Avg Value(True value-Avg Value) X 100) X 100
True ValueTrue Value
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Significant figures
Significant figure – a digit that is either reliably Significant figure – a digit that is either reliably known or estimatedknown or estimated
Assume that the last digit is uncertainAssume that the last digit is uncertain ex: in the number 1.23, there are three ex: in the number 1.23, there are three
significant figures and assume that the last digit, significant figures and assume that the last digit, the 3, is uncertainthe 3, is uncertain
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Reading Scales Estimate measurement to one digit beyond the Estimate measurement to one digit beyond the
smallest scale divisionsmallest scale division
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Counting Significant Figures
Atlantic / Pacific MethodAtlantic / Pacific Method
a. Absent Decimal- Start on “atlantic” side a. Absent Decimal- Start on “atlantic” side of number & cross out all zeroes until 1of number & cross out all zeroes until 1stst nonzero digit is reached, remaining digits are nonzero digit is reached, remaining digits are significantsignificant
b. Present decimal- start on the “pacific” side b. Present decimal- start on the “pacific” side of the number & cross out all zeros until the of the number & cross out all zeros until the 11stst nonzero digit Is reached, remaining digits nonzero digit Is reached, remaining digits are significantare significant
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2. Examples:
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Practice
Count the significant figures in each of the Count the significant figures in each of the following measurements:following measurements:
1.08951.0895 140001400012.012.0 5.0205.02010103001010300 17.19017.1900.001810.00181 910196891019680.19800.1980 0.000027000.00002700
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Examples
Round each of the following measurements Round each of the following measurements to 3 significant figuresto 3 significant figures
16.89216.892
1467014670
0.013350.01335
1.92201.9220
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Practice
Round each of the following measurements Round each of the following measurements to 2 significant figuresto 2 significant figures7.7117.7110.0001880.0001885.015.0113500135000.09850.0985
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Practice
Round each of the following measurements Round each of the following measurements to 2 significant figuresto 2 significant figures7.7117.7110.0001880.0001885.015.0113500135000.09850.0985
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Significant digits in calculations
1.1. Addition and subtraction – answer is expressed Addition and subtraction – answer is expressed to the same number of significant figures as the to the same number of significant figures as the number in the calculation with the fewest digits number in the calculation with the fewest digits to the right of the decimal pointto the right of the decimal point
ex.ex. 10.6871 10.6871 +1.42+1.4212.1071 = 12.1112.1071 = 12.11
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2. In multiplication or division - the answer is 2. In multiplication or division - the answer is expressed to the same number of significant expressed to the same number of significant digits as the number with the fewest digits as the number with the fewest significant digitssignificant digitsex.ex.2.34 2.34 3.225 = 7.5465 = 7.55 3.225 = 7.5465 = 7.55
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Calculation Practice
6.378 + 0.0025 = 6.378 + 0.0025 = 22.37 x 3.10 x 85.75 =22.37 x 3.10 x 85.75 = 22.4420 + 56.981 = 22.4420 + 56.981 = 91.68 - 19.191.68 - 19.1 = =
16.216.2 500,000 / 5.002 =500,000 / 5.002 =
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Scientific notation -Expressing very large and small numbers
Using scientific Notation - Numbers are Using scientific Notation - Numbers are expressed with one nonzero digit to the left expressed with one nonzero digit to the left of the decimal point multiplied by 10 raised of the decimal point multiplied by 10 raised to an appropriate powerto an appropriate power1. The base is the number with all of the 1. The base is the number with all of the appropriate significant digitsappropriate significant digits
2. The exponent is the power of ten the base 2. The exponent is the power of ten the base is multiplied byis multiplied by
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Scientific notation format
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Scientific notation and calculators 1. Calculators handle scientific notation by 1. Calculators handle scientific notation by
only inputting the exponent, using an EXP only inputting the exponent, using an EXP or EE keyor EE key
a. enter the base as you would a regular a. enter the base as you would a regular number, then press EXP or EE, then enter number, then press EXP or EE, then enter the exponentthe exponent
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Scientific notation and significant figures 1. When using scientific notation the base 1. When using scientific notation the base
must be written with the correct number of must be written with the correct number of significant digitssignificant digits
2. All zeroes are significant when using 2. All zeroes are significant when using scientific notationscientific notation
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Measurement of mass, length and volume In the United States, we use a fairly awkward In the United States, we use a fairly awkward
system of measurement for most things - the system of measurement for most things - the English system Scientists use the metric and SI English system Scientists use the metric and SI systems of units for the measurement of physical systems of units for the measurement of physical quantitiesquantities
This system using standard units based on very This system using standard units based on very precisely known properties of matter and lightprecisely known properties of matter and light
Prefixes are used in from of the units to indicate Prefixes are used in from of the units to indicate powers of tenpowers of ten
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SI Units
MeasurementMeasurement UnitUnit SymbolSymbol
MassMass KilogramKilogram kgkg
LengthLength MeterMeter MM
TimeTime SecondSecond ss
TemperatureTemperature KelvinKelvin KK
QuantityQuantity MoleMole molmol
EnergyEnergy JouleJoule JJ
PressurePressure PascalPascal PaPa
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SI Prefixes
PrefixPrefix SymbolSymbol PowerPower PrefixPrefix SymbolSymbol PowerPower
tera-tera- TT 10101212 deci-deci- dd 1010-1-1
giga-giga- GG 101099 centi-centi- cc 1010-2-2
mega-mega- MM 101066 milli-milli- mm 1010-3-3
kilo-kilo- kk 101033 micro-micro- 1010-6-6
hecto-hecto- hh 101022 nano-nano- nn 1010-9-9
deca-deca- dada 101011 pico-pico- pp 1010-12-12
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. Base Units
Mass - the quantity of matter that a sample containsMass - the quantity of matter that a sample contains
Note that weight is a measure of the attraction of Note that weight is a measure of the attraction of gravity for a sample and it varies depending on the gravity for a sample and it varies depending on the distance of the mass to a planet or moondistance of the mass to a planet or moon
Scientists often speak imprecisely of the “weight” Scientists often speak imprecisely of the “weight” of an amount of substance. They really mean of an amount of substance. They really mean mass.mass.
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Basic SI units/Derived units
Used to generate new UnitsUsed to generate new Units Volume - space a given quantity of matter Volume - space a given quantity of matter
occupiesoccupies Volume - expressed in terms of length - mVolume - expressed in terms of length - m33
mm33 - an inconveniently large volume, so we - an inconveniently large volume, so we use liter (L; one cubic decimeter)use liter (L; one cubic decimeter)
We often use a mL (1 cubic centimeter) for We often use a mL (1 cubic centimeter) for more manageable amounts of mattermore manageable amounts of matter
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Converting between units
The standard method to convert between The standard method to convert between two different units is the factor-label or two different units is the factor-label or dimensional analysis methoddimensional analysis method
Dimensional analysis converts a Dimensional analysis converts a measurement in one unit to another by the measurement in one unit to another by the use of a conversion factoruse of a conversion factor
Conversion factors are developed from Conversion factors are developed from relationships between unitsrelationships between units
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Conversion factors
Unit factors - factors that relate a quantity in Unit factors - factors that relate a quantity in a certain unit to 1 of another unita certain unit to 1 of another unite.g.e.g.101033 m = 1 km m = 1 km
The conversion factor is created by divided The conversion factor is created by divided both sides by the same quantityboth sides by the same quantity
101033 m m = 1 = = 1 = 1 km1 km101033 m 10 m 1033mm
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Dimensional Analysis
Multiplying a quantity in one unit by an appropriate Multiplying a quantity in one unit by an appropriate conversion factor converts the number into the new unitconversion factor converts the number into the new unit
Note that conversion factors are exact relationshipsNote that conversion factors are exact relationships Exact relationships have unlimited precision, so they can Exact relationships have unlimited precision, so they can
be ignored for the purposes of decided the number of be ignored for the purposes of decided the number of significant digits in a calculationsignificant digits in a calculation
km1068.4m10
km1m468.0 4
3
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