Proper&esofMa,erSec$on2

Essen&alQues&ons

Whatarephysicalandchemicalproper$es?

Whatarethedifferencesandsimilari$esofphysicalandchemicalchanges?

Howdoesthelawofconserva$onofmassapplytochemicalchanges?

ReviewVocabulary

boilingpoint:thetemperatureatwhichthevaporpressureoftheliquidisequaltotheexternalpressureac$ngonthesurfaceoftheliquid

NewVocabulary

physicalproperty

physicalchange

dis$lla$on

lawofconserva$onofmass

chemicalproperty

chemicalchange

PhysicalProper&esYoucanstretcharubberband,butyoucannotstretchapieceofstringmuch,ifatall.Youcanbendapieceofwire,butyoucannoteasilybendamatchs$ck.Theabili$estostretchandtobendsubstancesarephysicalproper$es.Theiden$tyofthesubstances—rubber,string,wire,wood—doesnotchange.Anycharacteris$cofamaterialthatyoucanobservewithoutchangingtheiden$tyofthesubstanceisaphysicalproperty.Someexamplesofphysicalproper$esarecolor,shape,size,density,mel$ngpoint,andboilingpoint.

PhysicalChange

TedKinsman/Scien

ceSou

rce

Physicalproper$escanchangewhilecomposi$onremainsfixed.Ifyoutearapieceofchewinggum,youchangesomeofitsphysicalproper$es—itssizeandshape.However,youhavenotchangedtheiden$tyofthematerialsthatmakeupthegum.

Whenasubstance,suchaswater,freezes,boils,evaporates,orcondenses,itundergoesaphysicalchange.Achangeinsize,shape,orstateofmaMerinwhichtheiden$tyofthesubstanceremainsthesameiscalledaphysicalchange.

ChemicalProper&esandChemicalChangesYouhaveprobablyseenwarningsoncansofpaintthinnerandlighterfluidforcharcoalgrillsthatstatetheseliquidsareflammable(FLAmuhbuhl).Thetendencyofasubstancetoburn,calleditsflammability,isanexampleofachemicalproperty.Anycharacteris$cofamaterialthatyoucanobservethatproducesoneormorenewsubstancesisachemicalproperty.Flammabilityisachemicalpropertybecauseburningproducesnewsubstances.Asaresult,achemicalchange,alsocalledachemicalreac$on,hasoccurred.Manyothersubstancesusedaroundthehomeareflammable.Knowingwhichonesareflammablehelpsyoutousethemsafely.

ChemicalProper&esandChemicalChangesAlessdrama$cchemicalchangecanaffectsomemedicines.Lookatthefigurebelow.YouhaveprobablyseenboMleslikethisinapharmacy.ManymedicinesarestoredindarkboMlesbecausethemedicinescontaincompoundsthatcanchemicallychangeiftheyareexposedtolight.

BrianHa

giwara/Food

Pix/Ge

MyIm

ages

Detec&ngChemicalChangeThesmellofroMeneggsandtheforma$onofrustonbikesandcarfendersarealsosignsthatachemicalchangehastakenplace.Achangeofonesubstancetoanotherisachemicalchange.Bubbleforma$onproducedbythefoamingofanantacidtabletinaglassofwaterisasignofnewsubstancesbeingproduced.Insomechemicalchanges,arapidreleaseofenergy—detectedasheat,light,andsound—isacluethatchangesareoccurring.Adisplayoffireworksinthenightskyisanexample.Thefigureaboveillustratesanothervisualclue—theforma$onofasolidprecipitate.

Andrew

Lam

bert/LeslieGarland

PictureLibrary/Alamy

WeatheringGeologists,whousethesamecriteriathatyouhavelearnedinthischapter,saythatsomeweatheringchangesarephysicalandsomearechemical.

(t)©

JimZuckerm

an/Corbis,(b

)PeteTurner/Iconica/G

eMyIm

ages

TheConserva&onofMassMassisnotgainedorlostduringanychemicalchange.Infact,maMerisneithercreatednordestroyedduringachemicalchange.Accordingtothelawofconserva&onofmass,themassofallsubstancesthatarepresentbeforeachemicalchange,knownasthereactants,equalsthemassofallofthesubstancesthatremainaZerthechange,whicharecalledtheproducts.

TheLawofConserva&onofMasstotalmassofthereactants=totalmassoftheproducts

MaM

Meado

ws/

McG

raw-HillEdu

ca$o

n

elementD

conserva$onC

physicalB

chemicalA

Whattypeofpropertyisrepresentedbytheillustra$on?

Assessment

1.

CORRECT

STOCK

4B/agefo

tostock

mel$ngD

evapora$onC

burningB

boilingA

Whichisanexampleofachemicalchange?

Assessment

2.

CORRECT

physicalpropertyD

chemicalpropertyC

physicalchangeB

chemicalchangeA

Supposeyoustarttoeatsomepotatochipsfromanopenbagthatyoufoundinyourlockerandno$cethattheytasteunpleasant.Whatprocessresultedinthisunpleasanttaste?

Assessment

3.

CORRECT

physicalpropertyD

chemicalpropertyC

physicalchangeB

chemicalchangeA

Howwouldyoudescribetheprocessofevapora$ngfreshwaterfromseawater?

Assessment

4.

CORRECT

ShakeWellD

FlammableC

SharpObjectB

FragileA

Whichofthesewarningsreferstoachemicalpropertyofthematerial?

Assessment

5.

CORRECT

forma$onofasolidprecipitateD

rustC

forma$onofbubblesB

brokenglassA

Whichofthefollowingisevidencethataphysicalchangehasoccurred?

Assessment

6.

CORRECT