LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFoodScientistsuseadevicecalleda“calorimeter”,showninFigure1,tomeasuretheamountofchemicalpotentialenergyinallsortsofmaterials..Todeterminethechemicalenergyofamaterial,scientistsfirstmeasurethemassofasampleofthematerial.Theythenplacethesampleinasealedcontainercalleda“bomb”.Theyputthebombinawell-insulatedcontainerfilledwithaknownvolumeofwater.Anelectricalsparkfrominsidethebombstartsthesampleburning.Thewaterinthecontainerabsorbstheenergyreleasedbytheburnedsample.Athermometermeasuresthechangeinthetemperatureofthewater.Thepotentialenergyoftheoriginalmaterialisequaltothethermalenergytransferredtothewater.Figure1.Calorimeter“Bomb”

Inthisactivity,youwilluseasimplifiedcalorimeterdevicemadeoutofasodacantomeasuretheamountofcaloriesinasampleoffood.SAFETYMEASURES

1. Wearsafetygogglesduringthisinvestigation2. Longhairmustbetiedback.3. Ifanythingotherthanthefoodmaterialbeginstoburn,notifyyourteacher

immediately4. Beespeciallycarefultokeepclothingandsleevesawayfromtheopenflame.5. Thecanmaybecomequitehot.Carefullyfollowallinstructionswrittenin

theprocedureandprovidedbyyourteacher.6. Anoteaboutfoodsensitivities:ifyouareallergictoanyofthefooditems,

pleasenotifyyourteacher.Sensitiveindividualsshouldnotparticipateintheburningofthematerialthatmayresultinexposure.

7. Noeatingordrinkinginthelab.

LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFood

Materials:Foreachgroup:Sodacan(empty)GlassStirringrodRingstandandringThermometerprobe(lab-quest)MiniadapterElectronicbalanceCorkMetalpaperclipGraduatedcylinderProcedure:CLEARSPACEOFALLFLAMMABLES1. Usingthegraduatedcylinder,obtain50mLofwaterandcarefullypourit

intothesodacan.2. Determinethemassofthewaterandrecordyourfindinginthedatatable

provided.(Hint:densityofwateris1g/mL)3. Holdthepapercliphorizontallyandbendtheouterendupwardsuntilit

isata90degreeangletotherestofthepaperclip.4. Obtainacorkandcoverthecorkwithaluminumfoil.5. Insertthepaperclipintothefoil-coveredcork.6. Insertthestirringrodthroughthesodacantabandpositionthecanin

theringstandsothatthestirringrodsupportsit(seeFigure2).

Figure2.

LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFood

7. Adjusttheringstandsothatthecanisapproximately4cmabovethefood

sample.

8. Suspendthethermometerinsidethecanandlettheedgeofthethermometercoverrestagainstthecan(seefigure3).

Figure3.

9. Attachthetemperatureprobetothelab-questminiadapterandconnectthistothedesktopcomputer

10. Open“loggerpro”andtakeaninitialtemperaturereadingofthewater.11. Measurethemassofyourfoodmaterialandrecorditinthedatatable.12. NowattachthefoodtothepaperclipasshowninFigure4.

LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFood

Figure4

13. Showyourteacheryourexperimentalset-upbeforeusingalightertoigniteyourfoodmaterial.

14. Onceyouhavereceivedapprovalforyourexperimentalsetup,initiatedatacollectioninlogger-proandigniteyourfoodmaterial.

15. Carefully,useamatchtolightyoursample.16. Allowthelitsampletoheatthewaterinthecan.Blacksootwill

accumulateontheunderneathsideofthecan.17. Monitorthetemperatureincreasewithloggerpro.18. Stopdatacollectionafterthesampleburnsout.19. Findtheremainingmassoftheburnedsample.20. Repeatforadditionalfoodsamplesastimepermits.

LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFoodDATACOLLECTIONTABLEMeasurement Sample1 Sample2 Sample3 Sample4 Sample5

Massofwater

Initialmass(foodpluspaperclip)g

InitialWatertemperature(Celsius)

FinalWaterTemperature(Celsius)

Finalmass(Foodsamplepluspaperclip)g

ΔT(oC)

Δ mass(g)

1.Calculatetheenergy(incalories)releasedbytheburningfoodsampleandabsorbedbythewater.

Q=mCpΔT

Q=heatabsorbedbythewater,m=massofwatering,Cp=1cal/goC,ΔT=changeintemperature

Q=________________calories

2.Prepareatableofyourresults.3.Determinethenumberofkilocalories(foodcalories)releasedbytheburningfoodsample.(1kilocalorie=1000calories)4.Calculatetheenergycontainedinthefoodinkilocalories/g5.Usinginformationonanutritionlabel,calculatekcal/g.(Dividecaloriesperservingbythenumberofgramsperserving).

LabActivity:MeasuringCaloriesinFoodLabActivity:MeasuringCaloriesinFood

6.Compareyourexperimentallydeterminedenergycontent(inkilocalories/g)tothecalculatedvaluefromthenutritionlabel.Calculatethepercenterrorforyourexperiment.PostlabReflection:Pleasetypeyouranswerstothefollowingquestions.1. Explainthesourcesoferrorinyourexperiment.2. Explain,intermsofenergytransferandtransformation,whatcausedthe

temperatureofthewatertochange.3. Wasalloftheenergycontainedintheburningfoodtransferredtothe

water?Ifnot,explainwhathappenedtotheenergythatwasnottransferredtothewater.

4. Howcouldyouimproveuponthedesignofthiscalorimetersothatitwouldworkbetter?

a. Drawadetailedlabeleddiagramofyourimprovedcalorimeter.b. Explainwhythisdesignisbetterthantheonethatyouused.

5. Acuriousstudentwantedtoknowifthecalorimeterwouldworkwith

differentamountsofwater.Thetablebelowshowstheresultsfromherburningfoodmaterialofthesamesizeandmass,butusingvariedamountsofwaterinthecan.Explainfromthetablebelowwhetherthecalorimetermeasuredtheenergyinthefoodmaterialproperlywhenusedwitheachamountofwater.

Experiment Massofwater(g) ΔT(oC)Sample1 200 19Sample2 100 39Sample3 50 77