NAME_________________________________________________________________________________PERIOD_______
LAB: Ocean Acidification
OBJECTIVES:
• IdentifyanddescribethechemicalreactionbetweenCO2andH2OtoformtoH+ions,
bicarbonateions(HCO3+)andcarbonateions(CO3+)intheworld’soceans
• Explainthecausesandeffectsofoceanacidification
• Simulatechemicalreactionforoceanacidificationusinglabmaterials
• CreateagraphdemonstratingtheeffectofexposuretimetoCO2onpHlevelsof
‘seawater’
• Predictanddeterminetheeffectofacidicconditionsonthemassofseashells
• Applyskills:DeterminepHusinguniversalindicatorstripsandcalculatetherelative
[H3O+]
BACKGROUND:
RefertotheCLASSNOTESonOCEANACIDIFICATION.
PART A) Effect of CO2 exposure to seawater on pH over time
WhenCO2isaddedtoseawateritbecomesdissolvedintosolution.Inasimulationactivity,
youwilladdCO2toabeakerofartificial‘seawater’byblowingbubblesthroughastrawfor
2minutes.HowwillthisaffectthepHofthe‘seawater?’
*Source:http://serc.carleton.edu/eslabs/carbon/7a.html
RECORDYOURHYPOTHESIS:
MATERIALS:
• Timer
• Beakerofartificialseawater
• Beakeroftapwater
• BromothymolBlueindicator
• Straw
PROCEDURE:
Assignthefollowingrolesinyourgroups:
• BUBBLEBLOWERS
• TIMER
• PHMEASURER(Comparessolutioncolortostandardsforbromothymolblue)
• RECORDER(recordsthedatatosharewiththegroup)
1) DeterminethepHoftheARTIFICIALSEAWATERBEFOREbeginning.Recordyour
datainthetablebelow.
2) Usingthestraw,STEADILYblowbubblesintotheseawaterfor2minutes.DON’T
BLOWTHEWATEROUTOFTHEBEAKER–NOMESSESPLEASE!!!
3) DeterminethepHevery30secondsusinguniversalindicatorstrips
4) Repeatsteps1-4usingthebeakerofTAPWATER
TABLE1:pHforseawaterexposuretoCO2
SAMPLE
pHat30
pHat60sec pHat90sec pHat120sec
sec
Tapwater
Artificialseawater
ANALYSIS:
1) Inthespacebelow,createagraphthatshowstheeffectoftimeofexposuretoCO2
(independentvariable)onpHfortapwaterandartificialseawater(dependent
variable).Besuretoincludethefollowingonyourgraph:LABELEDcurves
and/oraLEGEND,TITLE,LABELEDX-AXISandY-AXIS.
2) DescribetheresultsofyourCO2/pHexperiment.
3) Wasyourhypothesissupported?EXPLAIN.
4) Thisexperimentwasasmall-scalesimulationintheclassroomlaboratory.Could
theresultsofyourexperimentsbeusedtoaccuratelyinfertheeffectsofCO2
exposureonthepHofoceanwater?EXPLAIN.
PART B) Effect of acidic conditions on the mass of seashells
Thecompositionofcoralandtheshellsandskeletonsofshellfishismadeup,inpart,of
calciumcarbonate(CaCO3).Theyrequirecarbonateionsfromtheoceanwatertoundergo
calcification(theprocessofshellformation).WhenoceansabsorbexcessCO2,theresulting
acidificationdisruptsthecarbonateionconcentrationinthewater,whichimpedesthe
processofacidification.Asaresult,otherspeciesinthefoodchainmayalsobeaffected.In
thislabactivity,youwillexposeaseashelltoacidicconditionsanddeterminetheresultby
measuringtheseashell’smass.
HYPOTHESIS:Howdoyouthinktheacidicconditionswillaffecttheseashell’smassafter
2-3days?After1week?
MATERIALS:
• Artificialseawater
• Aceticacid(whitevinegar)
• Seashell
• Smallbeaker
• Universalindicatorstrips
• Digitalscale
PROCEDURE:
1) Selectaseashellofyourchoosing.Measureandrecorditsmass.
2) Inasmallbeaker,mixaceticacidwithseawater–youcanchoosetherelative
amountstocreateyourownuniqueacidiccondition!DeterminethepHofyour
acidicseawatersolutionusinguniversalindicatorstrip.Recordyourdata.
3) Placetheseashellinthesolutionyouhavecreated,makingsuretheshellis
COMPLETELYIMMERSED.
4) Coverbeakerwithplasticwrapandlabelwithyourname(useapapertowel).
5) Onday2or3,removetheshellandallowdryingthroughouttheclassperiod.
RecordthemassoftheshellanddeterminethepHofthesolution.Returntheshell
tothesolution,recover,andallowtoincubateuptoaweek.
6) Onthelastday,removetheseashellandallowtodrycompletely.Measureand
recorditsmass.DeterminethepH.
7) Calculatethe[H3O+],[OH-],andpOHfromyourpHdata.Inthespacebelow,
createadatatabletorecordandcompareALLofyourresults.
ANALYSIS:
1) Whatwastheeffectofacidificationonthemassofyourshell?
2) Wasyourhypothesissupported?EXPLAIN.
3) DidthepHofyoursolutionchangeovertime?WHYdoyouthinkitdidordidn’t?
4) RESEARCH:Asagroup,usethewebsiteslistedintheRESOURCEHANDOUTto
research:
• Theeffectsofoceanacidificationonaspecifictypeofsealife
• Industrial/economiceffectsofoceanacidification
• Waystopreventorcounteractoceanacidification
• PredictedpHlevelsfortheworld’soceans
Compileallofyourfindingsinavideoorpresentationslidefile.Submitin
GoogleClassroom.