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Essentialknowledgestandards• 1.E.1: Physical and chemical processes can
be depicted symbolically; when this is done, the illustration must conserve all atoms of all types
• 2.A.3: Solutions are homogeneous mixtures in which the physical properties are dependent on the concentration of the solute and the strengths of all interactions among the particles of the solutes and solvent.
(Intro)FLT• I will be able to:
• Describe and practice the scientific method
• Use mathematical relationships to convert between different units
• Identify significant figures and use them in mathematical computations
• Describe the different classifications of matter
• By completing Ch. 1 Notes
Ch.1:ChemicalFoundations
TakingNotesinClass• Take notes on bigger ideas, not
every little detail • DO copy down all problems/
calculations • After class, go to website to review
powerpoint and add useful details to notes
Introduction
Chemistry-Introduction• Idea:Matteriscomposedofatoms• Canweviewatoms?
– Individualatomscanbeviewedbyusingascanningtunnelingmicroscope(STM)
55
Chemistry-Introduction• Keepinmind:
– Didthescientistswhodevelopedatomictheoryactuallyseeatoms?
56
Chemistry-Introduction• Propertiesofasubstancecanbedeterminedbythewayinwhichatomsareorganizedinthatsubstance
57
Chemistry-IntroductionWhenanelectriccurrentispassedthroughwater,itdecomposestohydrogenandoxygen
• Bothchemicalelementsexistnaturallyasdiatomic(two-atom)molecules
58
Chemistry-Introduction• Matteriscomposedofvarioustypesofatoms• Byreorganizingthewaytheatomsareattachedtoeachother,onesubstancechangestoanother
59
ScientificInquiryProcess
ScientificInquiryProcess• Framework/procedureforgainingandorganizingknowledge
• Scientificmethodàscientificinquiry• Itstartswithanobservationthatgeneratesaquestion
TheScientificMethodFirst:Observe• Qualitative(5senses)orquantitative(measurements)
• ThisshouldgenerateaQUESTION
TheScientificMethodSecond:Generateahypothesis• Ahypothesisisapossibleexplanationforanobservation
• Oftenwritteninaconditionalformat,suchasif____,then_____
• Beabletomakeclaims
TheScientificMethodThird:Test!• Performexperiment(s)• Recorddataandanalyzetoaccept/rejectyourhypothesis
• Experimentsproducenewobservationsthatusuallyrequiretheprocesstoberepeated/adjusted
TheScientificMethod• Whendoesitbecomeatheory?• Theory(model):Setoftestedhypothesesthatgivesanoverallexplanationofanaturalphenomenon(inotherwords,lotsandlotsofexperimentssupportthisidea)– Explanationofwhynaturebehavesinacertainway– Constantlyrefinedorreplacedasmoreinformationbecomesavailable
Pair-Share-Respond1. Whatismattercomposedof?2. Identifythemainpartsofthescientific
method.3. Provideanexampleofaqualitative
observation4. Provideanexampleofaquantitative
observation5. Younoticethatyourhouseplantisdying.
Comeupwithaspecifichypothesisinthe“If___,then____”formtotestwhy. 67
UnitsofMeasurement
UnitsofMeasurement• Measurementsconsistofanumberandascale(unit)
• SISystem(international)isstandardsystem
UnitsofMeasurement• Table1.2–PrefixesUsedintheSISystem
UnitsofMeasurement• Table1.3–SomeExamplesofCommonlyUsedUnits
UnitsofMeasurement• Volume• Derivedunit(length)
UnitsofMeasurement• Figure1.6–CommonTypesofLaboratoryEquipmentUsedtoMeasureLiquidVolume
UnitsofMeasurement• MassvsWeight• Mass:Measureoftheresistanceofanobjecttoachangeinitsstateofmotion– Measuredbytheforcenecessarytogiveanobjectacertainacceleration
• Weight:Forceexertedbygravityonanobject– Varieswiththestrengthofthegravitationalfield
75
Uncertainty
UncertaintyinMeasurement• Differentmeasuringdeviceshavedifferentprecisions
UncertaintyinMeasurement• Certaindigits
– Numbersthatremainthesameregardlessofwhomeasuresthem
• Uncertaindigits– Digitsthatmustbeestimatedandthereforevary
Measurements:RecordALLcertaindigits+oneuncertaindigit
79
80
UncertaintyinMeasurement• Readvolumesatthemeniscus– Certaindigits-20.1– Uncertaindigit-20.15
UncertaintyinMeasurement• Significantfigures:Numbersinwhichthecertaindigitsandthefirstuncertaindigitarerecorded– Uncertaintyinthelastnumberisalwaysassumedtobe±1unlessotherwiseindicated
Pair-Share-Respond• Inanalyzingasampleofpollutedwater,achemistmeasuredouta25.00-mLwatersamplewithapipet– Atanotherpointintheanalysis,thechemistusedagraduatedcylindertomeasure25mLofasolution
– Whatisthedifferencebetweenthemeasurements25.00mLand25mL?
UncertaintyinMeasurement• Accuracy:Describeshowclosetothe“true”valueameasurementis
• Precision:Howreproduciblemeasurementsareinreferencetoeachother
UncertaintyinMeasurement• TypesofErrors• Randomerror(intermediateerror)
– Measurementhasanequalprobabilityofbeingloworhigh
– Occursinestimatingthevalueofthelastdigitofameasurement
Largerandomerrors Smallrandomerrorsandalarge
systematicerror
Smallrandomerrorsandnosystematic
error
UncertaintyinMeasurement• TypesofErrors• Systematicerror(determinateerror)
– Occursinthesamedirectioneachtime– Eitheralwayshighoralwayslow
Largerandomerrors Smallrandomerrorsandalarge
systematicerror
Smallrandomerrorsandnosystematic
error
Pair-Share-Respond• Theglasswareshownbelowiscalledaburet.Theburetisfilledtothezeromark(atthetop)withasolution,andthesolutionistransferredtoabeaker
• Whatvolumeoftransferredsolutionshouldbereported?
a. 20mL b. 22mLc. 22.0mLd. 22.00mLe. 25mL
UncertaintyinMeasurement
• Theboilingpointofaliquidwasmeasuredinthelab,withthefollowingresults:
– Theactualboilingpointoftheliquidis28.7°C
Trial Boilingpoint
1 22.0°C±0.12 22.1°C±0.13 21.9°C±0.1
Pair-Share-Respond• Theresultsofthedeterminationoftheboilingpointare:a. accurateandpreciseb. precisebutinaccuratec. accuratebutimprecised. inaccurateandimprecise
– Theactualboilingpointoftheliquidis28.7°C
Trial Boilingpoint
1 22.0°C±0.12 22.1°C±0.13 21.9°C±0.1
UncertaintyinMeasurement• _____reflectsthereproducibilityofagiventypeofmeasurementa. Accuracyb. Precisionc. Certaintyd. Systematicerrore. Randomerror
UncertaintyinMeasurement• _____istheagreementofaparticularvaluewiththetruevaluea. Accuracyb. Precisionc. Certaintyd. Systematicerrore. Randomerror
SigFigs
SigFigs• Rules:1. Nonzerointegersarealwayssignificant2. Leadingzeroesarenotsignificant3. Captive/In-betweenzeroesaresignificant4. Trailingzeroesaresignificantifadecimalpointis
present
SigFigs• Afterperformingacalculationinthelab,thedisplayonyourcalculatorreads“0.023060070”– Ifthenumberintheansweristohavefivesignificantfigures,whatresultshouldyoureport?a. 0.0230b. 0.00231c. 0.023060d. 0.2367e. 0.02306
Pair-Share-Respond• Howmanysigfigsin…?1. 1002. 1.0x1023. 1.00x1034. 100.5. 0.00486. 0.004807. 4.80x10-38. 4.800x10-3
SigFigs• Note:Exactnumbers
– Determinedbycountingandnotbyusingameasuringdevice
– Assumedtohaveaninfinitenumberofsignificantfigures
– Canarisefromdefinitions– Example-2in2πr – Ihave20gloves
• Thishasinfinitesigfigsbecauseitisanexactnumber,andisnotmeasured.
SigFigs• Multiplicationordivision
– Youranswershouldhavethesamenumberofsigfigsasthenumberisyourleastprecisemeasurement
SigFigs• Additionorsubtraction
– Youranswershouldhavethesamenumberofdecimalplacesasyourleastprecisemeasurementused.
Example:– 12.11+18.0+1.013
SigFigs• Rounding• Unlessyourproblemisseparatedintosteps,roundoffonlywhenyougetyourFINALRESULT
• Youranswermaybeverydifferentwhenyouroundsequentially
• Yourtextbookspecificallystatesthatitroundsoffeachsteptoshowsigfigs,butthatthismakestheiranswerdifferentàbecarefulwhenlookingatsomeoftheexamples.
SigFigs• Rounding• Whatifyouwereaskedtoroundtothehundredthsplacefor…– 2.835?– 2.845?
SigFigs• Rulesforrounding:
– Followwhatyou’velearnedaboutrounding– Ifthelastdigitis5,roundthenumbersothatitwillbeeven
– Ex/– 2.835à2.84– 2.845à2.84
Pair-Share-Respond• Roundthefollowingtotwodecimalplaces:1. 3.6824172. 21.8600513. 45.46734. 7.5555. 3.665• Calculateandroundifnecessary:
1. 1.05×10–3÷6.1352. 21–13.8
SigFigs• Thebeakersbelowhavedifferentprecisions
SigFigs• Youpourthewaterfromthesethreebeakersintoonecontainer– Whatisthevolumeinthiscontainerreportedtothecorrectnumberofsignificantfigures?a. 78.817mLb. 78.82mLc. 78.8mLd. 79mL
DimensionalAnalysis
DimensionalAnalysis• DimensionalAnalysis(UnitFactorMethod)• Helpsconvertagivenresultfromonesystemofunitstoanother
DimensionalAnalysis• Convertingfromoneunittoanother• Theequivalencestatementgoesintotheunitfactor(ex/102cm=1m)
• Theunityou’restartingwithalwaysgoesonthebottom(tocancelout)
• Theunityouwanttoendupwithgoesontop
DimensionalAnalysis• Ex/• Youwanttoorderabicyclewitha25.5-inframe,butthesizesinthecatalogaregivenonlyincentimeters– Whatsizeshouldyouorder?
DimensionalAnalysis• Ex/Howmanycentimetersarein4.50meters?
TryThis:• Ex/Howmanykilometersarein256centimeters?
Temperature
Temperature(don’tmemorize)• K=oC+273• oC=K–273
• oC=oF–321.8• oF=1.8(oC)+32
• (technically,it’s273.15forKàCorCàK,butwecanuse273)
• It’snotdegreesKelvin,justKelvin
Temperature• Withrespecttosignificantfigures
– ForoCàKorKàoC,sincetheconversioninvolvesadditionorsubtraction,it’sallabouttheprecisionofthegiventemperature• 85oC+273=358K• 85.5oC+273=358.5K• 85.55oC+273=353.55K
– ForoCàoForoFàoC,youwillhavetoconsiderthenumberofsignificantfiguresandtheprecision• 275.6oCbecomes528.1oF• 105.6oFbecomes40.9oC
Temperature• Ex/OneinterestingfeatureoftheCelsiusandFahrenheitscalesisthat–40°Cand–40°Frepresentthesametemperature– Verifythatthisistrue(oF=1.8(oC)+32)
Density
Density• Density• Propertyofmatterthatisusedasanidentificationtagforsubstances
• Densityofaliquidcanbedeterminedeasilybyweighinganaccuratelyknownvolumeofliquid
Density• Ex/Achemist,tryingtoidentifyanunknownliquid,findsthat25.00cm3ofthesubstancehasamassof19.625gat20°C
• Whichcompoundismostthemostlikelyidentifyoftheunknown?
Density• Table1.5-DensitiesofVariousCommonSubstances*at20°C
Density• Ex/A25gcylinderofiron(d=7.87g/mL)anda1.0grampelletofcopper(d=8.96g/mL)areplacedin500mLofwater(d=0.9982g/mL)– Predictwhethereachwillfloatorsinkinwater
a. Ironwillfloat,andcopperwillsinkb. Ironwillsink,andcopperwillfloatc. Ironandcopperwillsinkd. Ironandcopperwillfloate. Moreinformationisneeded
ClassificationofMatter
ClassificationofMatter• Matter=Anythingthatoccupiesspaceandhasmass• Hasmanylevelsoforganizationandiscomplex• Existsinthreemainstates
– Solid– Liquid– Gas
ClassificationofMatter• Solids
– Rigid– Fixedvolumeandshape– Slightlycompressible
ClassificationofMatter• Liquids
– Definitevolume– Nospecificshape
• Assumestheshapeofitscontainer
– Slightlycompressible
ClassificationofMatter• Gases• Nofixedvolumeorshape
– Takesontheshapeandvolumeofitscontainer
• Highlycompressible– Relativelyeasytodecreasethevolumeofagas
SeparatingMixturesIntoPureSubstances
SeparatingMixtures• Mixtures-havevariablecomposition• Classification
– Homogeneousmixture:Hasvisiblyindistinguishablepartsandisoftencalledasolution
– Heterogeneousmixture:Hasvisiblydistinguishableparts
• Canbeseparatedintopuresubstances,whichhaveconstantcompositions,byphysicalmethods
SeparatingMixtures• PhysicalChange• Changeintheformofasubstance
– Nochangeinthechemicalcompositionofthesubstance
• Example– Boilingorfreezingofwater
• Usedtoseparateamixtureintopurecompounds– Willnotbreakcompoundsintoelements
SeparatingMixtures
MethodsforSeparatingComponentsinaMixture
Distillation Filtration
Chromatography
SeparatingMixtures• Distillation• Dependsonthedifferencesinthevolatilityofthecomponents
• Worksbestwhenoneofthesubstancesisvolatile,andtheotherisnot,asthemostvolatilecomponentvaporizesatthelowesttemperature
• Ex/distillationofseawater
ClassificationofMatter• Filtration• Usedwhenamixtureconsistsofasolidandaliquid• Mixtureispouredontoamesh,suchasfilterpaper,whichpassestheliquidandleavesthesolidbehind
ClassificationofMatter• Chromatography• Generalnameappliedtoaseriesofmethodsthatuseasystemwithtwostates(phases)ofmatter– Mobilephase-Liquidorgas– Stationaryphase-Solid
• Separationoccursbecausethecomponentsofthemixturehavedifferentaffinitiesforthetwophases– Theymovethroughthesystematdifferentrates
ClassificationofMatter• Chromatography
– Componentwithahighaffinityforthemobilephasewillquicklygothroughthechromatographicsystemascomparedtoonewithahighaffinityforthesolidphase
• Paperchromatography:Usesastripofporouspaperforthestationaryphase
ClassificationofMatter• PureSubstances• Eithercompoundsorfreeelements
– Compound:Substancewithaconstantcompositionthatcanbebrokendownintoitselementsviachemicalprocesses
• Givensubstancebecomesanewsubstanceorsubstanceswithdifferentpropertiesanddifferentcomposition
– Element:Substancethatcannotbebrokendownintosimplersubstancesbyphysicalorchemicalmeans
ClassificationofMatter
ClassificationofMatter• Asolutionisalsoa:
a. heterogeneousmixtureb. homogeneousmixturec. compoundd. distilledmixturee. puremixture
ClassificationofMatter• Whichofthefollowingstatementsisfalse?
a. Solutionsarealwayshomogeneousmixturesb. Atomsthatmakeupasolidaremostlyopenspacec. Elementscanexistasatomsormoleculesd. Compoundscanexistaselementsormolecules