CellBiologist’sName:_____________________________Period:______Date:______
Mrs.Bouchard–7thGradeScience
PhotosynthesisLab
What Plants Need
What do plants need/use/consume?
(reactants)
What do plants give off? (products)
Basedonwhatyouwroteabove,trytowriteasummaryequationforphotosynthesis.
Example:Cakemix+Egg+OilCake
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Ontheleftofthearrowputthingsthatgointophotosynthesisandtotherightputthethingsthat
comeoutoftheprocess.
Bromothymolbluesolution,BTB,canindicate thepresenceofcarbondioxideinthewater.When
littleornocarbondioxideispresent, BTBwillshowabluecolor.Dependingupon theamountof
carbondioxide,BTBwill changetogreenoryellow.Yellowindicates morecarbondioxide.
BTBisanindirectindicatorforthepresenceofCO2.CarbonicacidisformedfromCO2andwater,
whichcausesBTBtochangefrombluetogreen,andwithevenmoreacid,to
yellow.WhenCO2istakenout(usedup),thecolorreversesbacktowardblue.ToseeifCO2is
consumedovertime,youmuststartwithyellowBTBsolution.
The Question: Do plants consume (use) CO2 or release it when they are in the light,
photosynthesizing?
Withyourgroupmembers,developaplan(procedure)toanswerthisquestion.Decidehowyou
willcollectconvincingevidence.Hereisthematerialyouhaveaccessto:
- 3testtubes
- testtubecapsorparafilmtocoverthetubes
- Elodeaplant,1piece(canbesplitinto2)
- Water
- Bromothymolbluesolution(BTB)
- Straw
- Aluminumfoil
- Lightsource(shared)
Directions:
1. Thecaptainwillgatherlabcoatsandgogglesforeachgroupmember.Anygroupmember
notwearingthecorrectsafetygearwillreceiveazeroforthelab.
2. Asagroup,youwilldecidewhatyourprocedurewillbefortoday’slab.Youaretryingto
provethatphotosynthesishasoccurredinsidethetubeovernight.
3. Eachgroupwillrun1experiment(butthismeansyouhavetocomparesomething)
4. Thingstoconsider:
- Doyouhavecontrolvariables(whatwillbethesameintheexperiment)
- Youhaveonly1independentvariable(whatyouaretesting)thatisdifferentinthe
experiment.
Procedure:
TeacherApproval:_______________
Data:
ObservationsofTestTubesinExperiment1
TestTube1
TestTube2
Start
After24hrs
Start
After24hrs
Whatwasyourprocedure?
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DataAnalysis:
1. Whichtesttube(s)showedacolorchangeinthisinvestigation?
2. Whatdoesacolorchangeindicateinthisinvestigation?
3.Whatdoyourresultsindicate?
4.WriteaC.E.R.openresponsetoexplainyouranswertotheprompt:
Do plants consume (use) CO2 or release it when they are in the light,
photosynthesizing?
Claim:
Evidence:
Reasoning: