chapter 1 matter and measurements. wolpa/advanced placement chemistry2 how to be successful in...

Chapter 1

Matter and MeasurementsMatter and Measurements

Wolpa/Advanced Placement Chemistry 2

How to be Successful in Chemistry

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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)


Chemistry

The study of matter and the changes it The study of matter and the changes it undergoesundergoes


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


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.)


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.


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


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


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


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


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


What’s happening?


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


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


Relationships between temperature scales

F8.1

C1F32)F()C(

273)C()K(

tt

tT


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)


Temperature Scale Comparison


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


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


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)


Heterogeneous Vs. Homogeneous Mixtures


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)


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)


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.


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.


Putting it All Together


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


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


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


Example: Accuracy and Precision


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


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


Reading Scales Estimate measurement to one digit beyond the Estimate measurement to one digit beyond the

smallest scale divisionsmallest scale division


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


2. Examples:


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


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


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


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


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


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 =


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


Scientific notation format


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


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


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


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


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


. 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.


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


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


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


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

chapter 1 matter and measurements. wolpa/advanced placement chemistry2 how to be successful in...

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