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THE STRUCTURE OF LIVTNG MATTER
ion areoiientedwith theiroxygensnex to theion. and.molculasaround anesative
ion turntheirliydrogensto-wardthe ion.Thus thewatermolecuiesact ascageswhichseprateand neu-tralize theions. Thisesplainswhy wateris soeflective asoivent forelectrolvtes
(substances whichdissociate ir.toions)such assodiumchloride.
Water
isgenerallysupposedto be agoodconductor ofelectricity. Everylinemanknowsthedanger ofhandlinghigh-voltageelectricallineswhestand-ingor amoist surf
ace,Actuallythe con-ductvityis due toimpuritiesdissolvedin thewater.
Water issuch asood soi -vent forelectroiytes.includingcarbn,dicxiderom theatmosphere, hat anymoist surface rnaybeassumedto.be agoodconductor.But purwater(which is
80
HYDRATE is fanasri wiien a oreigr molecie in valer is eiectricaU" neutral sur! jus the righsiz- for liie v-ater XTOiecnie to eollect around t in crTstalline caze. Tbi? cage can tbsn groi>' toE n-uch iarger crysi.al. It E par*, of t. repeating unit of 136 molecnles.
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difficult tokeep pur it must be keptout of contactwith airand in avessel ofan inertmaterial
such asquartz) isa ven.-goodinsuiatorindeed.The rea-son is thatwhile thehydrosrenand oxy-gen atomsin a watermoiecue
are in asensecharged,or ionized.theycannotmoveabouiseparatelybecausethey areattached toeachother. and
henee can -not careyan eiectriocurrent.
Onec theanomalous
properties ofliquidwater ists highspedficheat or
heat-holding-capaciry. Thespecificheat of asubstance is thequantityof heatrequiredto raisethetemperat
ure of one Sramonedesreecentigrade. The-specificheat ofliquidwater ismorethantwice asgreat as
that ofice. Theexpiana-tion ishat theliquid'sionizedoxysenandhydrogenatoras,thoughheld to-gether,
behavelike freeions intheircapaciryto vbrateinresponseto heat.Thusthey canabsorb asmuchenergy asif theions
werereally free.
Thestrong
bondingof watermolecuiesaccountsfor thefact thatwater has
unusuallyhishmeltingand
boiling pcints. Itaisoexplainswhy it isso diffUcult tovaporizaice, To dothis we
must break allthehydrogen
bondsholdingthemoieciilestogether,Calculations indcatethat thetotalenergy of
the hydro -gen bondsin onemole ofwater (18grams) isequivalentto 6.000calories.
Hydrates
Formore than60 vean
physicalchemistshavestudiedwaterlargely intrras cfsoluonsofelectrolvtes. This
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study hasproducedconsidera
ble infor-maionaboutelectrolvtes andions. bunot agreat deal
about thepropertiesof wateritsel.Strangelvenoueh.in recentyears wehaveiearneclmuchmoreaboutwater bvexarninin
g its-behaviorwithsubstances whichfoi all
practica!pur-posesareinsolublein water!
Thisbehaviorwas callea
to the at-tention ofchemistsin adramaticfash-ion
by certaiasurprisins; natural
phe-nomena.One wasthe facthat ccrnsometmes showedfrosteffectswhen thetemperature was 40desreesF... wellabovefreezing.Anotherwas thediscov-ery that
pipelines
carrvingnaturalgas often
becamecloggedwith aslushy"snow."containingwater, at
tempera-tures ashigh as68degreesF. The
plainindication wasthatthesefreeze-ups weredue tothe
water.'-But thisraisedsomestartlingandinterestins;questioas. Whamadewaterfreeze atthese
highternperatures?Howcouldwatercom-
bine, orbecome"bounc."withsub-stanceswhichwere ali
butinsoiubiein it?Themysterywas notlessenedwhen itwasdiscovered thateven thenoblegases
such as
argn andkrypton.whichrefuse alichemicalreactions.couid joinwithwater toform aquasi
compound.Let us
look atthesequestionsin thelight ofwhat wehaveiearnedabouwater'sstructureand
properties. Tenyears agoin Illinoiswe begana study cfthe water-solubiiityof certainhydro-carbons.Methanegas willserve as
anexample.Themethanemoiecuedoes notform ionsin water,or doesit ac-ceptthehydrogen
bonds.There isvery littleattraction
between itand thewatermoiecue.It is.howevsr.sligysoluble inwater, andthedissolvingmethanemolecuies
form
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compounds withwater"hvdrates"
inwhichsevera!watermoie-cules are
joined to
one of methane.The
resctionliberares10 timesas muchheat aswhenmethanedissolvesin hexane.althoughit is muchmore
soluble inhexanetaar.- inwater.This fact
becoaiesevenmoresurprismgon ciseexamnation. Themethanemoiecue
occupiesmore thaniwice thevol-umeof a watermoiecue,Te formthisreiativeiylargecavitv foritself ondis-solving, agreat dea!of enerzywould beraquired:it should
besomewhatgreaterthan theheat of vaporization of watersay10,000
calories
perrnoie.Howcouid somuchenergv
beprovided?The.forces of
attraconbetweenmethaneand wa -ter areapparentiv tooslisht tosuppivanvapprecia
bl-3 partof suchan
arnouni.There
is analternative
possibiil*.'. The
presenceof thsmethanernavdras-ticallvohanse
the-.vatsrstructureitseli.