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Youcanemailcommentsortalktomeinclass.Youcanalsolookforasurveysooncomingby
emailthatyoucanfillout.Thissurveyiscompletelyanonymous.Thegoalistokeepthisblog
andpodcastgoingthroughouttheterminawaythatismostusefultoeveryone.Iplantouse
thisforumtointroducechaptersandofferpost-chapterreviewsofchapters.Someanswersto
FAQscanalsobeafocusofposts.Anysuggestionsfortopicstodiscussareencouraged.
Today’sblogpostandpodcastareonthetopicofusefultopicsfromhighschoolchemistryfor
reviewpriortobeginningChem1210.ManyofthetopicsofChemistry1210willlikelybethings
you’vealreadylearnedaboutinhighschool.APchemistryisoftenverysimilarincontenttoour
classandevenregularhighschoolchemistrycoversmostofthemaintopicsoftenthoughwith
alittlelessdepth.OneparticularwayChem1210mightbemoreadvancedthanthesehigh
schoolcoursesisthatwehaveastrongfocusontheideasandconceptsthatyoumust
understandforsuccessinlatercourses,likeChem1220,Chem2310/2510/2520/2540/2550
(organicchemistrycourses),andupperlevelbiochemistry,genetics,andmaterialsscience
courses.
Asameanstoreviewand/orintroducesomeofthemaintopicsforthecourse,thisblogpost
willreviewsomeofthekeytermsandideasfromthefirst11chaptersofourtextbook.
Chapter1:
Chemistry:Propertiesandreactionsofmatter.
Chemicalreactions:transformationofasubstanceorsubstancestonewsubstances.Wewill
discusswhatachemicalsubstancemeansanddefinitionsofelements,compounds,and
moleculesinchapter1.
Significantfigures:Oneofthemorechallengingconceptsofhowtoapply,butthissystemhelps
knowhowtoroundresultsofmathematicalcalculationsinvolvingmeasurements.
Measurementsalwayshavesomefundamentallimitationonhowwelltheyareknown.Likea
scaleinyourbathroommightweightouttothenearest1poundormaybetothenearest0.1
pound.Mostobjectscouldbedescribedbyamuchmoreprecisemassthanthis,thoughthis
bathroomscalewouldbelimitedtoonlytheplaceholdersshownonitsdisplay.Oftenyoufind
toolsthishavesomeuncertaintyinthatlastplaceholder–youmightseesomefluctuationand
youwouldtryyourbesttotakethemassastheaverageofthesevalueswhenpossible.When
youdoacalculationonanumberlike123,youordinarilywouldthinkthismeans123.00000000
butif123representsthenumberofpoundsreadfromascale,itwouldreallymean123±1.The
truemassoftheobjectisverylikelybetween122.5and123.5andwecannotknowitsmassany
betterthanthisrange.Thisfundamentallimitationwilllimitthenumberofplaceholdersthat
aresignificantincalculationsofthisvalue,likeaddition/subtraction,multiplication/division,
naturallogs,etc.Wewillgoovertheserulesinthefirstweekoflecture.
Precisionvsaccuracyofameasurement:Precisionistherepeatabilityofameasurementand
accuracyishowcloseameasurementistoatruevalue.Accuracycanonlybetestedby
comparisontoaknownvalue,likeusinganexactly1.00000±0.000001kgobjecttotestthemass
ofabalance.Thetopicofsignificantfigureshasmoretodowithprecisionofameasurement,in
whichamoreprecisemeasurementisonethatcontainsmoresignificantdigits.Amass
recordedonabalanceof125.5poundsismoreprecisethananotherbalancewhichreadsits
masstobe126pounds.Bothmeasurementsareessentiallyjustasaccurateaseachother
though.Weeithertestatoolinthelaborwewilljustassumeagiventoolisaccurateitsgiven
numberofplaceholders.
Rulesofsignificantfigures,whichwewilldiscussthoroughlyinlecture,aregeneralizedrulesfor
statisticalanalysiswhendealingwithmeasuredquantitiesthatyoumightlearnmoreaboutin
anintroductorystatsclass.Significantfiguresareakeyitemofdiscussioninchapter1sowe
willexplorethistopicinlecture,sothisisnotatopicIexpectmostofyoutohavemuch
knowledgeaboutfromhighschoolchemisty.
Onefinaltopicfromchapter1isdimensionalanalysis.Youlikelyrecallthatthismethodisoften
usedtoconvertunitsforproblemslikefiguringouthowmanysecondsarein1year.Wecan
alsousedimensionalanalysisasageneralmeansofsolvingproblemsanytimeequalitiesare
known.Oneequalitythatcaneasilybeusedindimensionalanalysisisdensity,likethedensity
ofwateris1.00g/mL.Ifyouhave55.0mLofwater,itwouldofcoursehaveamassof55.0g
becausethedensitysaysyouhave1.00gpereverymL.Wehardlyneedanymethodtosolve
thatproblem.Butwhatifwe’retalkingaboutethanol,whichhasadensityof0.789g/mL,what
isthemassof55mLofethanol?Well,nowwemightrightthisoutmorecarefully:
#g=55mLx0.789g/mL=43.4g
AllweneedtoknowtosetthisproblemupisthatthemLmustcancelout,sowemust
thereforemultiplybythedensityandthenthiscalculationresultsinourdesiredunitofgrams
beinginthenumerator.Wecouldhaveinsteadusedtheformulafordensity,whichisd=m/V,
rearrangedform,andpluggedandchugged.Thisproblemsolvingmethodistotallycorrecttoo,
butwedidhavetorememberanequationtousethatmethodandwedidn’thavetoremember
muchofanythingtousedimensionalanalysis.Wewilloftenusedimensionalanalysisinthis
coursetosolveavarietyofproblemsinwaysthatoughttomakethesolutionssimplerthan
othermethods.
Ididn’tmentionthisdetailinthepodcast,butthereisreallyneveranywhereonexamsor
recitationswhereyouhavetoshowwork(recitationsarejustattendancepointsandexamsare
allmultiplechoice).Sohowyousolveyourhomeworkproblemsismostlyirrelevant,provided
youultimatelygettheanswerright!Ialwaysrecommendthoughthatyouwriteoutunitsin
yourworkthoughasthisprocesswillhelpeliminatemistakes.
Topicsinchapter2includemodernatomictheory,atomicandmolecularweights,andsome
examplesofcommoncompoundsandrulesfornamingclassesofcompounds.Thefirsttwo
sectionsdiscusstheoriesaboutthediscoveryofthesubatomicparticlesliketheelectron
(negativeparticle),proton(positiveparticle),neutron(neutralparticle),andhowthetheoryof
thenuclearatomwasdiscovered.Wewillbrieflydiscusstheperiodictableandit’sstructure
basedonincreasingsizeandgroupingofelementsbysimilarproperties.
Eachoftheelementsdifferbythenumberofprotonswithinthenucleusoftheatoms
comprisingtheelement.Hydrogenatomshave1protonintheirnucleus,carbonatomshave6.
Thenumberofprotonshencedefinestheidentityoftheatomsoit’scalledtheatomicnumber.
Theneutronisaneutralparticleandatomsofsomeelementscandifferinhowmanyneutrons
theycontain.Atomsofthesameelementwithdifferentnumberofneutronsareisotopes.
Carbonforexamplemostcommonlyexistsascarbon-12andcarbon-13.Thenumberafterthe
elementisthemassnumber,thesumoftheprotonsandneutrons(socarbon-12has6protons
and6neutrons,about99%naturalabundanceofcarbon,andcarbon-13has6protonsand7
neutrons,whichisabout1%naturalabundanceofcarbon).Theseisotopesoftenbehavevery
similarlyandtheyareonlydifferentbythesmalldifferenceinmass.Electronsarenotcounted
inthemassnumberprimarilybecausetheirmassisverylow,around1/1000ththemassofa
protonorneutron.Theelectronsbeingsolightareonereasonwhytheydonotcoexistamong
theprotonsandneutronsbutinsteadspinaroundthepositivelychargednucleus.Theproton
andelectronhavethesamemagnitudeofcharge,justoppositeincharge.Soaneutralcarbon
atomcontains6electrons.Afluorineatom(9protons)with10electronshasachargeof-1and
hencethisisanion.Na+istheionofsodiumwith11protonsand10electrons.Wewillsee
oftenatomsneartheendsoftheperiodictablecanloseelectrons(ontheleftside)orgain
electrons(ontherightside)sothattheyarriveatastablenoblegascountofelectrons.Wewill
seelaterinchapter6howelectronconfigurationsandshellsplayarole.
Metallicelementsonlyloseelectronstoformcationsandtheywillnevergainelectronsand
formanions.Metallicelementsaswewillseeinchapter7havelowionizationenergies.
Sodium’sgroup(thealkalifamily)willloseoneelectrontoform+1cations,calcium’sgroup
(alkalinefamily)willlosetwoelectronstoform+2cations.Thetransitionmetalscanoftenlose
avariablenumberofelectronsthatisnotverypredictable,thoughtheywouldneverloseany
electronspastthenearestnoblegascount(forexample,titaniumcanformtheTi4+cationasits
highestchargedcationsinceitwouldhave18electronslikeargon).Inorderforametal(orany
atom)toloseelectrons,anotheratommustbeabletoacceptthoseelectrons.IfNa(s)andCl2
(g)wereallowedtoreacttogether,twosodiumatomswouldloseoneelectroneachandtheCl
atomsinaCl2moleculewouldgainoneelectroneachandthecompoundNaClwouldresult.
Thiscompoundisanioniccompound,Na+andCl–ionswouldbepresentandtheirelectrostatic
attractionkeepsthesaltcrystalheldtogether.
Wewillseecommoncompoundsandnamingconventionsintheendofchapter2.Wewillalso
seesomebasicsofformulasandchargesofionsincommonioniccompounds.
Chapter3dealswithchemicalreactions,suchaswriting,balancing,andsolvingproblems
relatedtobasicchemicalreactions.Achemicalreactionshowsthereactantsontheleftside
andthenewsubstancesthatresultintheproducts.Achemicalreactionisnotreallyan
equality,ratheritismuchbetterthoughtofasa‘beforeandafter’.Achemicalreactionnever
changestheidentitiesoftheelements,ratheronlynewcompoundsareformedfrom
rearrangingtheatomsintonewsubstancesintheproducts.Asanexample,CH4(methane)
reactswithO2(oxygengas)toformcarbondioxide(CO2)andwater(H2O).Allofthecarbonin
methanewillendasallofthecarbondioxide(CO2).Allofthehydrogeninmethaneendsupin
thewatermoleculesthatform.If1moleculeofmethanearereacted,then1moleculeofCO2
andtwomoleculesofH2OmustformtobalancetheCatomsandHatoms.TwomoleculesofO2
mustthereforebepresentinthereactants.Reactionsmustalwayshaveanequalnumberof
atomsinthereactantandproductsidesofthereaction:
CH4+2O2àCO2+2H2O
Subscriptsareneverchangedtobalanceareaction.Subscriptsrelatethenumberofatomsof
anelementinamoleculeorunitofthecompound.Anoxygenmoleculecontainstwooxygen
atoms.“2O2”intheabovereactionimpliestwooxygenmolecules.O4wouldbeatotally
differentmolecule,whichdoesnotevenexist.Afewothermoleculeexamplestogetasenseof
thecomplexityothermoleculeshave,methanolisCH3OH,youcouldwritethisasCH4Obut
CH3OHisimplyingsomethingaboutthemolecularstructureofthemoleculethatwewilllater
seemoreaboutinchapters8and9.Methanolisamolecularcompoundandasampleof
methanolwouldcontainmanymoleculesofmethanol.Ifyouweretoboilmethanol,individual
moleculesofmethanolwouldescapefromtheliquidsurfaceintogaseousvapors(justlike
watermoleculesevolvefromboilingwater).SulfateionisSO42–.PotassiumsulfateisK2SO4(and
thisisanexampleofanioniccompound,withanoverallneutralcompoundcomprisedofions).
Stoichiometryisanotherkeytopicchapter3,whichisthebookkeepingsystemforreactions.So
sayif3.0gramsofmethanereactswithexcessoxygen,stoichiometrywillhelpusfigureout
howmuchCO2andH2Owouldform.Themoleisacommonunitwewilluse.Amoleofan
objectrefersto6.02214179x1023ofthatobjectsoamoleofmethanolcontains6.02x1023
methanolmolecules(roundingtothreesigfigs).Theperiodictableliststheaverageatomic
weightsofalloftheelements,oftenroundedto4-5sigfigsbutyoucanlookmoresigfigsupin
theCRCifeverneeded.Theaverageatomicweightaccountsfortheabundanceofeachisotope
ofanelementanditsatomicweightanditsumsupallofthesequantitiesfortheaverageatom
ofeachelement.Forcarbon,carbon-12isdefinedtohaveamassofexactly12atomicmass
units(amu),sothinkofitsmassas12.000000000000·····amu.Moreonthissystemina
moment,butthemassofcarbon-13isabout13amu(wewillseeapreciseexampleinclass).If
yourecallcarbon-12isabout99%naturalabundanceandcarbon-13isabout0.01,sotake0.99
times12plus0.01x13=12.01.Sotheaverageatomicweightofcarbonisjustalittleoverthe
massoftheisotopethat~99%oftheatomshaveamassof,thatmakessenseIhope!Togeta
senseofamorepreciseatomicweight,we’dhavetoplugintheexactmassandabundanceof
thecarbon-13isotope.Backtotheamuacale,socarbon-12’smasswasdefinedtobeexactly12
amu.Ifyoutakeasexactmassof12gramsofcarbon-12asyoucanfindabalancetomeasure
(about9sigfigsispossible)andstartcountingatoms,you’dcomeupwithabout
6.02214179x1023atoms(Avogadrofiguredthisout).Whatthismeansisthateachatomweights
12.0000000g/6.02214179x1023atoms=1.992···x10–23g.Thisthenalsomeansthat12amu=
1.992x10–23g,orthat1amu=1.660····x10–24g,orthat1g=6.022···x1023amu.OK,ifyoucan
followallofthat,that’sgreat!Wewilltalkaboutthatderivationinclass,butthereisasimple
conclusionwecaneitherdrawfromthisorjusttakeforgranted,thatisthattheperiodictable
tabulatedthemassesofeachatom,eitherintheunitofamuperaverageatomoringramsper
moleoftheelement.Sooxygenontheperiodictablesays15.9994.Thismeanseitheran
averageoxygenatomhasamassof15.9994amuorthatonemoleofoxygenhasamassof
15.9994g.Wecouldcallthemolarmassofoxygento15.9994g/mol.Wecanthenusethe
periodictabletodeterminemolarmassesofcompoundsjustbyaddingupalloftheaverage
molarmassesofitselements,soCH4=12.01+1.008*4=16.04g/mol.
GoingbacktotheCH4+2O2àCO2+2H2Oreaction,thereactantsandproductscanberelated
intermsofmoleculesormoles:1moleculeofCH4reactswith2moleculesofO2toform1
moleculeofCO2and2moleculesofH2OOR1moleofCH4reactswith2moleofO2toform1
moleofCO2and2moleofH2O.If3.00gramsofCH4reactswithexcessO2,andwewantedto
knowhowmuchCO2forms,wecouldconvertgramsofCH4tomoles,molesofCH4canthenbe
convertedtomolesofCO2,andthenthemolarmassofCO2(44.01g/mol)canbeusedto
convertmolesofCO2togramsofCO2;8.23gramsofCO2wouldform.
Stoichiometryalsogetsintowhichreactantlimitstheamountofproductformationandwhich
mightbepresentinexcess,orwhatthepercentyieldisofareaction.Chapter4getsinto
reactionstakingplaceinwater,suchasacid-basereactionsandmetathesisreactions(whichare
reactionswhereyoutaketwowater-solubleioniccompounds,likeNaCl(aq)andAgNO3(aq)
whenmixedleadtoAgClforming,whichisawhitesolid,whichwouldappeartoformas
snowflakesinthesolutionandultimatelysettleonthebottomofthereactionflask.AgClforms
asasolidbecausethecompoundisinsolubleinwater.Solubilitytrendsofionswillbediscussed
sowecanproductwhenmetathesisreactionswilloccur.Chapter4alsodiscussesoxidationreductionreactions,whicharereactionswhereelectronsaregained(i.e.reduction)andlostby
atoms(i.e.oxidation)duringthereaction.Chapter4wrapsupwithsolutionstoichiometry
problems,suchastitrations.
Chapter5discussesheatcapacity,likehowmuchheatmustwaterabsorbtoraiseits
temperature,andenthalpychangesofchemicalreactions.AlaterchapterinChem1220would
getintootherthermodynamicstopics.
Chapter6dealswithpropertiesofelectronsinatoms,startingwiththehydrogenatomin
greaterdetailandthenelectronconfigurationsforlargeratomstowardstheendofthechapter
(e.g.youmightrecallthegroundstateelectronconfigurationofcarbonis1s22s22p2).
Chapter7dealswithnuclearandperiodictrends.Onesuchperiodictrendisionizationenergy,
whichmostlyincreasesfromlefttorightacrossarowoftheperiodictablebutdecreasesfrom
toptobottomdownagroup.Wewilldiscusswhy,aswellwewilldiscussothertrendslike
atomicsize,ionicsize,andelectronaffinitytrends.Thesetrendscanhelpusunderstandsimple
bondingtrendsinioniccompounds,likesodiumshouldhasarelativelylowionizationenergy,
sonotmuchenergyisrequiredfortheatomtoloseanelectron.Chlorineontheotherhandhas
amuchhigherionizationenergy.SoifyouareconsideringtheionicstructuretobeeitherNa+Cl–
vs.Na–Cl+,thelatterwouldtakemoreenergytoformCl+thanitwouldtakeforsodiumtolose
anelectron,soNa–Cl+isunlikelytoformwiththosecharges.Additionally,theelectronaffinity
ofClismorenegative,aselectronaffinitydecreases(becomesmorenegativeandhencemore
favorableforanatomtoabsorbanelectron)fromlefttoright.SoClisenergeticallymore
favoredtoacceptanelectronthanNa.SowecanconcludethatNaClformsthestructurewe
havethoughtallalong,Na+Cl–.
Chapter8startswithadescriptionofionicbondstrengthsasarelationshiptothelatticeenergy
oftheions.Asionsaremorehighlychargedinmagnitude,thelatticeenergyincreaseshence
theionicbondstrengthisstronger,andthenanassociatedtrendlikemeltingpointshould
increase.Forexample,wecancompareNaCl(mp~800˚C)toMgO(mp2850).MgOhashigher
chargedionsofMg2+O2–,sotheattractionoftheseionsismuchgreater.Thecompoundhasa
latticeenergyaboutfourtimesthatofNaClandlikewiseitsmeltingpointismuchgreater.
Thesecondhalfofchapter8iscenteredaroundLewisstructuresofmolecularcompounds.
Molecularcompoundsresultbetweennon-metallicelementslikeC,H,N,O,Cl,etc.These
elementsbynaturehavehigherionizationenergiesandmanyhavelessnegativeelectron
affinities.Sothesecompoundsarenotabletogainandloseelectronslikemetalsandnonmetalsareableto.Instead,theseelementsmustshareelectronswitheachotherinorderto
gainstability,throughbondscalledcovalentbonds.Covalentbondsarenotasstrongasionic
bonds.ALewisstructureisadepictionofallofthebondsandbondtypes(suchassingle,
double,triple,etc)inamolecule.Hydrogenmolecule,H2,hasasinglebondbetweenitstwoH
atoms,H–H.EachHatomhastwoelectronsnearit,allowingeachtohaveanelectroncountlike
He–it’snearestNoblegaselement.Twooxygenatoms,eachwith6valenceelectrons,can
adoptaconfigurationof8valenceelectronsbyformingtheoxygenmoleculewithadouble
bond:O=O.CH3OHforexamplehasthreesinglebondsbetweenCandH,asinglebondbetween
aCandOatom,andasinglebondbetweenOandH.Throughsomesimplerulesandideas,we
cangetintosomebiggermoleculestowardtheendofchapter8.
Electronegativityandbondpolarityisdiscussedinchapter8andwediscussmolecularpolarity
inchapter9.Wealsotalkaboutthreedimensionalmolecularshapeinchapter9.Chapter9also
discussesmolecularshape.Organicchemistrybuildsoffmanyoftheideasfromchapters8and
9.
Chapter10isonthetopicofgasesandbeginswiththeidealgaslaw.Inthislaw,gasesare
describedasnon-interactingparticles.Notmuchchemistryhappensbetweennon-interacting
particles!However,allgaseswilleventuallycondense,hencetheirparticlesmustatsomelow
temperaturebegintointeract.TheseinteractionscanbedescribedbythevanderWaals
equationtowardtheendofchapter10andthesubsequentliquidstateisdiscussedinchapter
11.
Chapter11discussesmanyimportantfactorsofliquids,suchasintermolecularforcesof
dispersionforces(forcepresentinliquidsofnonpolarsubstances),dipole-dipoleforces(force
presentinliquidsofpolarsubstances),hydrogenbonding(forcepresentinliquidsofpolar
substanceswhereHisdirectlybondedtoanN,O,orFatom).Theseintermolecularforcesare
weakerthancovalentbondsbuttheyarestillveryimportantforunderstandingpropertiesof
liquids.Manypropertiesandtrendsofaliquidcanbeinferredfromitstypesofintermolecular
forces,andtheseforcescanbeimpliedfromknowledgeoftheshapeandstructureofa
molecule.Chapter12completesadiscussionofthephaseofsubstancesbydiscussingsolids.
ThisismuchlongerthanIthoughtitwouldbe!Ihopethisgivesasenseofwhatthiscourseis
aboutandthatyouprobablyhaveheardmanyofthesewordsandideasbefore.Wewillexpand
upontheseideasandfocusonproblemsolvinginourlectures.
Thereisanotherhandoutyoucanreadonsomeofthesetopics.It’spostedbelowontheblog–
checkitoutifyouwanttoreadmore.
ThisisthelastblogentryoftopicsIhadplannedbeforeourclassstartsup.Ifyouhave
questions,keepthemcomingasIcoulddomorepostsonFAQsiftherearestillquestions.Ialso
plantokeepthebloggoingthroughoutthetermthoughI’mexactlysurehowIplantodothis.
MyplanatthemomentisIcouldprovidepreand/orpostchaptersummariestohelpintroduce
topicsandtohelpreviewmaterial.Ifyouhaveideasforfutureblogtopics,letmeknow!