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Energetic Electrolysis: The Potentials of Hydrogen Power

 

ActivityGuide

Learning Objectives

• Thecomponentsofwatercanbeseparatedintooxygenandhydrogenusinganelectricalcurrent,aprocessiscalledelectrolysis

• Ifhydrogengasisgeneratedusingarenewableenergysourcesuchaswindorsolar,ithasalotofpotentialasa“clean”energysource

• Oncehydrogengashasbeencapturedandstoreditcanbeusedtopowercars,homes,orcomputers

• Hydrogenpowerisoneexampleofhowtechnologicalinnovationscanbeusedtoaddressenergyandenvironmentalconcerns

Climate Connection

Electrolysisistheprocessofusinganelectricalcurrenttoseparatewaterintohydrogenandoxygengas.Theelectricalchargethatisappliedtowaterwillbreakthechemicalbondbetweenthehydrogenandoxygenatomsandproducechargedparticlescalledions.Forthepurposesofthisexperimentthechargedhydrogenandoxygengasisproducedataluminumfoilelectrodes.Oncecapturedandstored,hydrogengascanberunthroughafuelcelltopowercars,homes,evencomputers.Hydrogengasproducedthroughelectrolysiscanbeusedforpowerwhenrunthroughafuelcell.Afuelcellcombinesseparatedhydrogenandoxygentomakeelectricity.Inthepastseveralyearswehaveseengreatadvancesinfuelcelltechnologyandanaccompanyingincreaseinexcitementaroundthepotentialsforhydrogenpowertoreplacefossilfuelenergysources.Thereareseveralobstaclestoovercomeifwearetousehydrogenasanenergysource.Hydrogengasisveryflammable,andtherearesafetyissuessurroundingitsstorageandtransport.Theexplosivepropertyofhydrogenisdemonstratedinthis

Description: This activity uses electrolysis to introduce the science behind hydrogen power. Visitors will use an electrical current to separate water into hydrogen and oxygen gas. The audience will then observe a demonstration showing the explosive properties of hydrogen gas.

Audience: Hands-on activity for families and kids ages 7 and up

Length: Approximately 25 minutes

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activityandservesasagoodlaunchingpointfordiscussingstorageissues.Currentlyscientistsareworkingondevelopingsafetransportandstoragesystemsforhydrogengas.Theproductionofhydrogengasisnotalways“cleanandgreen.”InfactmosthydrogengasproducedintheUnitedStatestodayismadeusingnon‐renewableresourcessuchaselectricityproducedfromcoalfiredpowerplantsthatproducetheelectricitynecessaryforelectrolysis.Hydrogendoeshavethepotentialtobeacleanenergycarrieriftheelectricalcurrentnecessaryforelectrolysisisproducedfromarenewableenergysourcesuchassolarorwindpower.Imagesofoff‐shorehydrogenpowerplantspoweredbysolarpanelshaveincreasedtheexcitementaroundhydrogenpower.Inadditiontohavingplentifulsunlight,thesaltyoceanwaterhelpstoconductelectricitythatallowsforelectrolysistooccur.Usinghydrogenpowerandfuelcellstostorerenewableenergycanreduceouruseofpollution‐producingenergysourcessuchasfossilfuels,thereforereducingpollutionandhelpingtoslowtherateofclimatechange.

Materials

Forthepresenter• Onesetofthematerialsforeachpairofvisitors• Matches• 2largetesttubes

Foreachpairofvisitors• One6voltlanternbattery• 2smallstripsofaluminumfoil• Smallplasticcontainer(withacenterdivider)• 2alligatorclips• Tapwater• Sodiumsulfateorsodiumchloride(tablesalt)

Note:Practicethedemonstrationbeforeconductingthedemonstration!Thisishighlyrecommendedastheexplosionpartofthedemocanbealittletricky!

The technology to use hydrogen as a power source was first developed for use on the space station. 

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Set Up

Setuptakesapproximately10minutesStep1:Preparethesaltwatersolutionaddingoneheapingspoonfulofsodiumchlorideorsodiumsulfatepercupofwater.Step2:Preparethematerialsingroupssothateachgroupofvisitorswillhaveaccesstoabattery,twoalligatorclips,twopiecesofaluminumfoil,andtheplasticcontainerwithsaltwater.Step3:Practicethedemonstration.

• Createabasicelectrolysissetupusingthelanternbattery,2alligatorclips,aluminumfoilelectrodesandsodiumsulfate(orsalt)watersolution.Note:  Don’t let the electrodes touch; this will short out the battery. 

• Completelysubmergethetesttubeintothewaterandslidetheelectrode

intothetesttube.(Ithelpstofillthetesttubewithsaltywater,thensubmergeittopreventairfromenteringthetube.)Oncetheelectrolysishasbegunthehydrogenandoxygengaswilldisplacethewaterinthetesttube.

• Afterhalfofthewaterinthetesttubehasbeendisplacedbyhydrogengas,

unclipthealligatorclipsandstoptheelectrolysis.

• Slowlypullthetesttubewithhydrogengasoutofthewatersolution,beingcarefultokeepthetesttubepointeddownsothegasdoesn’tescape.Pullthetesttubeupslowlyandavoidhavingwaterflowupthetesttube.

• Holdingthelitmatchunderthetesttubeslowlytiltthetesttube.They

hydrogengaswillencountertheflameandaquickexplosionwilloccur.

Program Delivery

[Connectthealligatorclipsonthedemonstrationsetupandbegintheelectrolysis.][Welcomevisitors.Explainthateachpairofparticipantsshouldsitinfrontofabattery.Explaintoparentsthatthisisafamilyactivity,andtheyshouldworkwiththeirchildrenifneeded.]Today’sprogramisallaboutenergy.Wheredoesenergycomefrom?[thesun,wind,water,coal,oil,wood,etc.Trywritinganswersdownandgroupingthemintotwocategories,renewableandnon‐renewables.]

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Wearegoingtotalkaboutanexcitingwaytostoreenergythatisproducedfromthesun,wind,coal,oranyoftheotherenergysourcesyousuggested.Thisistheformationofhydrogengas.Whoknowsanythingaboutusinghydrogenforpower?[Participantsmaycommentoncombustibility,hydrogenpower,hydrocars,etc.]Hydrogenisagasthat,ifstoredandharnessedcorrectly,canhelpuspowercars,homes,orevencomputersinaclean,greenway.Thetechnologytousehydrogenasapowersourcewasfirstdevelopedforuseonthespacestation.Inordertogethydrogengasweneedtoseparatewatermolecules.Whoknowthetwopartsofwater?[HydrogenandOxygen,H2O]ThechemicalformulaforwaterisH2O[Writethissymboldownifappropriate.]Everywatermoleculeincludestwoatomsofhydrogenandoneatomofoxygen.Weuseaprocesscalledelectrolysistobreakapartwatermoleculesintohydrogenandoxygen.Electrolysisusesanelectricalcurrenttosplitthemoleculeapart.Inthisactivitywearegoingtosplitwatermoleculesintohydrogenandoxygengasesusingelectrolysis.Inorderforelectrolysistoworkyouneedtousethematerialsthatyouhaveinfrontofyou.[Showvisitorsthematerials.]Becauseweareworkingwithelectricity,itisveryimportantthatyoulistentoinstructionscarefully.Thebatteryprovidestheelectricalcurrentthatweneedtoseparatethewatermoleculeintohydrogenandoxygen.Thepowerthatwentintomanufacturingorproducingthisbatteryprobablycamefromanonrenewableresource.Ifthepowerforelectrolysiscomesfromarenewableresource,thenhydrogenpowerisaverycleanenergysourcebecauseitdoesnotresultintheproductionofcarbondioxide,themaingreenhousegasresponsibleforclimatechange.Theplasticcontainerwillholdthewaterthatwewillseparate.Salt(orsodiumsulfate)hasbeenaddedtothewaterbecauseitconductselectricity.CanyouthinkofaplaceonEarthwerewehavelotsofsaltywater?[theocean]Manypeopleareexcitedabouthydrogenpowerbecausewecanusethehydrogenseparatedfromoceanwater.Nextweneedtomakeelectrodesusingpiecesofaluminumfoil.Inordertoattractthesetwopartsofthewatermoleculeswemustattachelectrodesontheendofourpowersource,inourcasethebattery.Theelectrodescarrytheelectricalcurrentfromthebatterytothewaterandhydrogengasisproducedatoneelectrodeandoxygengasisproducedattheother.[Notethatoxygengasisonlyproducedifyouareusingsodiumsulfateinyourwatersolution]

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[Demonstratethefollowingprocedure]Let’sallmaketwoelectrodes.Becausewewantanelectrodewithalotofsurfacearea,wearegoingtotakeathinstripoffoilandfolditbackandforthaccordionstyle.Firstpushdownyourelectrodesothatitisflat.Thealligatorclipswillcarrytheelectricityfromthebatteryintotheelectrodes.Cliponeelectrodeontheendofeachofyouralligatorclips.Nextwecanfullysubmergeourelectrodesintothesaltwater.Beforeweconnecttothebatterypleasemakesurethatyourelectrodesarenottouchingeachother.Iftheelectrodestoucheachotherwhiletheyareconnectedtothebattery,thebatterywillbedamaged.[Stresstheimportanceofthis:iftheelectrodestouch,itwillruinthebattery.]Nowclipeachfreeendofyouralligatorclipsontothespringsofyourbattery.Whatdoyousee?(Gasbubbleswillbeproducedoneachelectrode.Thereshouldbemoregasbubblesontheelectrodethatisattachedtothenegative,cathodesidewherethehydrogengasisproduced)Doyounoticemoregasbeingproducedatoneoftheelectrodes?[Therewillbemoregasproducedatthecathode,negativeside,wherethehydrogengasisproduced.]Whydoyouthinkthereismoregasproducedthere?[TheelectrolysisissplittingwaterorH2O.Foreachwatermoleculeweseetwiceasmuchhydrogengasthanoxygengas.][Note:  This is only accurate if you are using a sodium sulfate solution.]Great,whatyouareseeingistheproductionofhydrogenandoxygengas!Whydoyouthinktherearemoregasbubblesononeelectrodethantheother?[Foreverywatermoleculethatseparates,thereistwiceasmuchhydrogen(H20).]Howdoweknowthatweareactuallytrappinghydrogengas?[Runatest,useourobservationskills,etc.]Onepropertyofhydrogengasisthatitisveryflammable.Infacthydrogengasissoflammablethatscientistsareconcernedaboutwaystosafelystorelargeamountsofhydrogengas.[Showvisitorsthedemonstrationyouhavesetuptocapturehydrogengas.]Slowlypullthetesttubewithhydrogengasoutofthewatersolution,beingcarefultokeepthetesttubepointeddownsothegasdoesn’tescapeandtoavoidhavingwaterflowupthetesttube.[Holdingthelitmatchunderthetesttube,slowlytiltthetesttube.Thehydrogengaswillencountertheflameandaquickexplosionwilloccur.]

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Frequently Asked Questions

• WhatdoIdoifonlyafewbubblesarebeingproducedduringelectrolysis?Tryaddingmoresodiumsulfateorsalttothewatersolution,ortrybringingtheelectrodesclosertoeachother(rememberingnottoletthemtouch!).

• Isn’thydrogengasdangerous?I’vehearditisverycombustible.Althoughinlargeamountshydrogengasisveryexplosive,theamountweareproducingtodaydoesnotriskexplosion.Thequestionofcombustibility,however,isaconcernintheuseofhydrogenpowerasasourceoflarge‐scaleenergy.

• CanIuseadifferentsizedbattery?Forsafetyconcernswerecommendthatonlya6voltbatterybeused.Thesebatteriescanbefoundatanygeneralhardwarestore.

• Willelectrolysisworkwithoutaddedsaltinthewater?Sometimes.Ifyouliveinaplacewithhighamountsofironinyourtapwater,theironmayactasagoodenoughconductortoproducegas.

• Whatisthedifferencebetweenusingsodiumchloride(tablesalt)andsodiumsulfate?Bothsaltandsodiumsulfateserveasaconductorofelectricity,whichincreasestheamountofhydrogengasproducedbytheelectrolysis.Whensaltisused,itproduceschlorinegas,insteadofoxygenontheanodesideofthecurrent.Usingasodiumsulfateandwatersolutionwillcauseoxygengastoform.(*Note:Theamountofchlorinegasthatisproducedwhenusingasaltsolutionisverysmallandisnotaconcern.)

• Whatisthedifferencebetweenafuelcellandabattery?Fuelcellsconsumepowerfromanexternalsourcethatneedstobereplenished,whilebatteriesstoreelectricalenergychemically.Inthecaseofahydrogenfuelcell,theexternalsourceishydrogenasfuel,andoxygenisanoxidantduringcombustion.

Credits ThisprojectismadepossiblebyagrantfromtheU.S.InstituteofMuseumandLibraryServicesCopyright2010,Sciencenter,Ithaca,NY.