e 3.1.1.2. chemistry sciences: c. atmospheric properties ... investigations 05... · density of...

E 3.1.1.2. Chemistry Sciences: C. Atmospheric Properties 1

E 3.1.1.2. Chemistry Sciences: C. Atmospheric PropertiesActivity: Fluid Investigations

NSES Standards for Grades 5-8:Structure of the Earth System

• Theatmosphereisamixtureofnitrogen,oxygen,andtracegasesthatincludewatervapor.Theatmospherehasdifferentpropertiesatdifferentelevations.

NCTM Expectations: • Represent,analyze,andgeneralizeavariety

ofpatternswithtables,graphs,words,andwhenpossible,symbolicrules.

• Solveproblemsinvolvingscalefactors,usingratio and proportion.

Science as Inquiry: Asaresultofactivitiesingrades5-8,allstudentsshoulddevelopUnderstandingaboutscientificinquiry.•

Abilitiesnecessarytodoscientificinquiry:identifyquestions,designaninvestigation,collectandinterpret•data,useevidence,thinkcritically,analyzeandpredict,communicate,andusemathematics.

Source: National Science Education Standards



Time: 75 Minutes

Materials: Globe•Thinsheetofbubblewrap•Bowlingball(orother14.7lbobject)•Balloon•Measuringtape•Aquariumwithwater•2glassflasks•

Student Materials:Per Student

TornadoTube®coupler•2empty2Lsodabottles•Coloredwater•

Per Pair of StudentsBagof100itemsof3colors,proportion-•atetoatmosphericgases(nitrogen:blue,oxygen:red,hydrogen:white)Smalltrayorpaperplate•Mini-belljarwithtubingandsyringe•Largemarshmallow•

Per Group of 4 StudentsEmpty2Lsodabottle•Pressurizingvalvebottlepumper•Digitalscale•

Science Process Skills:

Investigating•Comparing•Interpreting•Recordingdata•Inferring•Hypothesizing•

Math Process Skills:

Counting•Comparing•Graphing•

Objective:The learner will determine there are a number of characteristic properties of air including mass, weight, density, volume, and pressure.The learner will identify gases and their proportions that make up the Earth’s atmosphere.The learner will categorize air as a fluid, similar to the ocean, based on observable properties.



Instructor Preparation : Fluid Investigations ActivityPreparebagsofbeads(orotheritems)with78bluebeadstorepresentnitrogengasmolecules,21redbeadstorepresentoxygenmolecules,and1additionalbeadofwhitetorepresentthewatervaporandtracegasesintheatmosphere.

Puttogether“tornadotubes”withcoloredwaterapproximately2/3fullinonebottleandanemptybottleontop.

Havematerialsorganizedontraysorintubsandreadytodistributeduringthelesson.



Anatmosphereisalayerofgasesthatsurroundsaplanet.Earth’satmosphereisusuallyreferredtoasair.

What is Earth’s atmosphere made of?Earth’satmosphereiscurrentlycomposedoftwomaingases:nitrogen(N2)andoxygen(O2).Together,thesecomponenetsmakeupabout99%oftheparticlesintheatmosphere.Theremaining1%oftheatmosphereconsistsoftracegasessuchasargon,carbondioxide,neon,ozone,andotherminorcomponents.Youmaywonderwherewaterfitsintothemix.Thecompositionoftheatmosphereisusuallystatedintermsofthecompositionofdryair.Dryairreferstoairwithlittlerelativehumidity,oraverysmallamountofwatervapor.Watervapor(thegaseousstateofwater)isacomponentofEarth’satmosphere,butitvariessignificantly,fromabout1%to7%,dependingonseasonandlocation.Evenairthatisconsidereddrywillhavetraceamountsofwatervapor.Watervaporistheonlymajoratmosphericcomponentinwhichtherelativeconcentra-tionchangeswithaltitude(heightaboveEarth’ssurface);ingeneral,asaltitudeincreases,watervaporconcentrationdecreases.Theatmospherealsoincludesdustparticles,liquidwaterdroplets,andicecrystals.

Composition of Earth’s Atmosphere

Gas Percent of Dry Atmosphere by VolumeNitrogen 78.084%

Oxygen 20.946%

Argon 0.9340%

CarbonDioxide 0.0380%

Neon 0.001818%

Helium 0.000524%

Methane 0.00017%

Krypton 0.000114%

Hydrogen 0.000055%

WaterVapor Highlyvariable;typicallymakesupabout1%

Source: NASA: http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.htm

Instructor Background Information:

Note:Students may assume that because humans need oxygen and we get oxygen from air, that oxygen gas must be the primary component of Earth’s atmosphere. In fact, nitrogen gas (N2) is the main compo-nent of the atmosphere. Oxy-gen gas (O2) is the next largest component. Other gases such as carbon dioxide (CO2) and argon (Ar) each makes up less than 1% of the atmosphere.

E3.1.1.2.ChemistrySciences:C.AtmosphericProperties 5


Key Vocabulary

Solids—Themoleculesinsolidsareboundtightlyanddonotmovemuch.Thisiswhysolidsmaintaintheirshapeandvolume.Example: Rock

Liquids—Themoleculesinliquidsarelooselyboundandareinmotion.Becauseitsmoleculesarelooselybound,aliquidwilltaketheshapeofthecontainerinwhichitisplaced.Example: Water

Gases—Themoleculesingasesarenotboundtooneanother.Becauseofthis,agasdoesnothaveafixedshapeorvolume.Itwillexpandtofillanycontainerinwhichitisplaced.Example: Air

Plasmas—Plasmaislikeagasinthatitspreadsouttofillthespacethatcontainsit.Butplasmaiscomposedofions(atomswithanega-tiveorpositivecharge)andfree-movingelectrons.Asaresult,plasmaconductselectricity.Itisahighen-ergy,hightemperaturestateofmatterthatemitslight.Examples: Neon signs, fluo-rescent lightbulbs, lightning

Fluids—Fluidsaresub-stancesthatflowfreelyandtendtoassumetheshapeofthecontainerin

whichtheyareheld.Liquids,gases,andplasmaareconsideredfluids.

Elements—Substancesmadeofonlyonetypeofatom.Example: Oxygen (O2)

Compounds—Substancesmadeoftwoormoretypesofatoms.Example: Water (H2O)

Atoms—Anatomisthesmallestparticleofanelementthatretainsallthepropertiesofthatelement.

Molecules—Aparticlemadeoftwoormoreatomsthatarechemicallybonded.

Mass—Theamountofmatterinanobject.

Weight—Thepullofgravityonanobjectorsubstance.Itisproportionaltothemass.Thegreaterthemass,thegreatertheweight.

Density—Theamountofmassperunitvolume.Somethingthatismoretightlypackedismoredensethansomethingthathasmorespacebetweenthemolecules.

Volume—Theamountofspaceanobjectoccupies.

Densityofair—MassperunitvolumeofEarth’satmosphere.

Atmosphericpressure—Theforceexertedbyaironaunitarea.

Equilibrium—Astateofrestorbalanceduetotheequalactionofopposingforces.

ExperimentalDesign—Astudyusedtotestcause-and-effectrelationshipsbetweenvariables.Theclassicexperimentaldesignspecifiesanexperimentalgroupandacontrolgroup.

Control—Aprocedureidenticaltotheexperimen-talprocedureexceptfortheonefactorbeingstudied.

Independentvariable—Avariablethatismanipu-latedbytheresearcherandevaluatedbyitsmeasurableeffectonthedependentvariableorvariables.Itispurposelychangedsothattheeffectcanbetested.

Dependentvariable—Afactorthatismeasuredtolearntheeffectofoneormoreindependentvari-ables.Itiswhathappensasaresultoftheindependentvariable.



Density, Volume, and Atmospheric Pressure

ThedensityofairisthemassperunitofvolumeofEarth’satmo-sphere,anditisausefulvalueinaeronauticsandothersciences.Airdensitydecreaseswithincreasingaltitude,andsodoesairpressure.Densityalsodecreaseswithincreasingtemperatureorhumidity.Asthedensityofairdecreases,thevolumeofagivenmassofairwillincrease.Forexample,NewOrleansisatsealevelandhasanairdensityofapproximately1.2kg/m3.Denverisatahigherelevation(approximately5,280feetabovesealevel),andithasanairdensityofapproximately1.05kg/m3.

Atmosphericpressureistheforceexertedbyaironaunitarea.Itcanbethoughtofastheweightoftheairagainstasurface.Thatis,thefewermoleculesaboveyou,thelowerthepressureextertedonyouandviceversa.(Moremoleculesaboveyoumeansthattheairwillexertmorepressureonyou.)Sincetherearefewermoleculesaboveyouasyoumoveupintheatmosphere,pres-surealwaysdecreaseswithincreasingaltitude.Atsealevel,theamountofairpressurepushinginalldirectionsisapproximately14.7poundspersquareinch.InDenver,at5,280feet,theatmo-sphericpressuredropsto12.10lbs/in2.(http://www.turblex.com/altitude/index.cfm)IntheUnitedStates,pressureiscommonlyexpressedinmillibars(mb)orinchesofmercury(in.Hg).Meteo-rologistsusemillibars(theunitshownonweathermaps),andavi-ationandtelevisionweatherreportsoftenuseinchesofmercury.Atmosphericpressureismeasuredwithabarometer,whichiswhyitissometimescalledbarometricpressure.Theaveragesealevelpressureis1013.25mbor29.92in.Hg.1mb=0.02953in.Hg.

How thick is Earth’s atmosphere?

Thetermthicknessoftenreferstothedensityofanatmosphere.Earth’satmosphereissaidtobethickerthantheMoon’sbecauseitisdenser.Atthesurface,Earth’satmospherecontainsabout31020particlespercubiccentimeter,whiletheMoon’satmospherecontainsontheorderof2x105particlespercubiccentimeter.ThedensityoftheatmospheredecreasesexponentiallywithdistancefromEarth’ssurface.

Where does Earth’s atmosphere end?

Becausetheatmosphereismadeofgas,itishardtosayexactlywhereitends.Itsdensitydecreasesgraduallywithaltitude.Whilesomereferencesstatethattheatmosphereendsat160km(100miles)abovesealevel,othersstatethatitreaches560km(348miles)orhigher.Thisdiscrepancyarisesbecausesmostofthe



massoftheatmosphereislocatedwithintheregion75km(50miles)aboveEarth’ssurface,butsomeatmosphericgasesextendmuchfartherout.Forexample,theHubbleSpaceTelescope(HST)orbitsEarthatanaltitudeofabout600km(374miles).TherearestillenoughmoleculesatthisaltitudethattheygraduallyslowHSTdownandcauseittolosealtitude.

Therearefourlayersoftheatmosphere:troposphere,stratosphere,mesosphere, and thermosphere. The troposphere is the lowest,densestlayer.Thetroposphereextendstoanaltitudeofabout15km (9miles).Thisheight canvaryby locationand season.Near-ly allweatheroccurs in the troposphere (someweather extendsinto the lower stratosphere).Mostplanesfly in the troposphere.The stratosphere is the second layer from theground.This layercontainsmostoftheozonethatabsorbsharmfulUVradiation.Thisabsorptioncausesthestratospheretobewarmerthanthetopofthetroposphere.

Where do the gases in Earth’s atmosphere come from?

Earth’satmospherehasevolvedoverthe4.6billionyearsofEarth’shistory.

ThegasesthatmakeupEarth’satmospherecomefromthreemainsources:

1. Earth’sinterior(via volcanic eruptions and radioactive decay)

2. Livingthings(via biological processes such as photosyn-thessis and respiration)

3. Outerspace (via comets)

Why doesn’t Earth’s atmosphere float away?

Theatmosphereismadeofgases,whichmeansthattheatomsandmoleculescanfloatfreelyandarenotbondedtoeachother.Gravi-tykeepstheseparticlesfromfloatingoutintospace.IfEarth’sgrav-itywereweaker,therewouldbefewerparticlesintheatmosphere.Ifitwerestronger,Earth’satmospherewouldbethicker.

Bycomparison,themassofthemoonissmall,whichmeansthatitsgravitationalpullistooweaktokeepgasesfromflyingoutintospace.



Introduction: What is the Ocean of Air?UsingaglobeasamodelofEarth,pointoutthegeographicfeaturesofEarth,suchaslandformsandwater,andrelatethemtothestatesofmatter.(Landformsaresolids,waterisaliquid.)

Ask: ArethereanyothercriticalfeaturesofEarththatarenotdisplayedbytheglobemodel?(The atmosphere)

Explain:Atmosphereisthewordusedtorefertotheblan-ketofgasesthatsurroundsEarth.Eventhoughwecannotseeairweknowthatairparticlesareallaroundusbecausetheyhaveparticularcharacteristicsthatwecanobserveandmeasure.

Airisamixtureofmanydifferentgases.TherearemainlytwokindsofgasmoleculesthatmakeupEarth’satmo-sphere:nitrogenandoxygen.Nitrogenmoleculesarethemostabundant.OnereasonforthisisthatnitrogendoesnoteasilyreactwithmostsubstancesonEarth.Also,nitrogenisstableinthepresenceofsolarradiationintheatmosphere.Secondinabundanceareoxygenmolecules,mostofwhicharegeneratedthroughphotosynthesis.Theremainingpartoftheatmosphericparticlesareamixtureofwatermolecules(waterinitsgaseousform)andtraceamountsofothergases.

Note:Refer back to previous lessons on atoms, molecules, ele-ments, and compounds.

Lesson



ActivityGiveeachpairofstudentsapreparedZiploc®bagcontain-ing100smallbeadsormarblesandatrayorpaperplateonwhichtowork.Explainthateachbagrepresentsamodelofanairsample.Workinginpairs,havestudentsseparateandcountthenumberofitemsofeachcolorandenterthenumbersintoatabletodeterminethepercentageofeachgasintheatmosphere.

Item Number of Particles per 100

Fractional Equivalent

Decimal Equivalent

Percentage of Gases in the Atmosphere

Nitrogen-blue

78 78/100 0.78 78%

Oxygen-red

21 21/100 0.21 21%

Water vapor and other gases-white

1 1/100 0.01 1%

Usingtheinformationinthechart,havestudentslabelthepie-graphintheirActivity Logs.Thepie-graphrepresentsthepercentageofgasesinEarth’satmosphere.

ExplainthatclosertothesurfaceofEarththerearemoreairmolecules,butasyoumovehigherinaltitude,therearefewerandfewermolecules.Themoleculesabovepushdownonthemoleculesbelow.Therefore,theairclosetothesurfaceofEarthismoretightlypackedtogether.Thehigherinelevationyougo,themorethemoleculesarespreadout.

Note:This table is included in the Student Activity Log.



Theamountofspaceagivenamountofmaterialtakesupisitsvolume.Theamountofmassperunitofvolumeisitsdensity.Forexample,sandisdenserthanwater.Therefore,ifyoufilledonecontainerwithwaterandanidenticalcon-tainerwiththesamevolumeofsand,thecontainerfilledwithsandwouldhavealargermassthanthecontainerfilledwithwater.Thedensityofairdecreases(themole-culesarespreadfurtherapart)asyoumovehigherineleva-tion.HavestudentsobservethealtitudedensityimageontheirActivity Logs.Thenhavestudentsfillintheblankareasnexttothisimageintheirlogs.

Demonstration:Blowupandtieoffaballoon.Measureandrecorditscir-cumferenceinaplacevisibletotheclass.Telltheclassthatyouhavemeasuredtheballoontoseehowmuchspacetheairmoleculesaretakingup.Telltheclassthatairmoleculeswillspreadapartwhenthetemperatureoftheairincreases.

Ask:Howcanweproveordisprovetheideathattheairmoleculesspreadfurtherapartwhentheairiswarmer?Possible answer: We can warm up or cool down the balloon to see if there is any change in the volume of the balloon.

Leadstudentstosuggestplacingtheballoonintherefrig-eratorforsometime.Placetheballoonintherefrigeratorwhileyouconductotherinvestigationsandremoveitlater.

Height of the Atmosphere:

Explainthattheatmospheredoesnotcometoanabruptendbuttheparticlesgraduallygetfurtherandfurtherapart,untilthereisnosignificantnumberleft.Insomeplaces,theatmosphereextendshigherthanitdoesinotherplaces.Becauseitisagasandisalwaysinmotionandchangingshape,youcannottakeanexactmeasurement.However,theaverageheightoftheatmosphereis100miles.Usingtheglobemodel,layasheetofthinbubblewrapoverthesurface,andexplainthatatthisscale,theatmospherewouldbeaboutasthickasthebubblewrapcomparedtothesizeoftheglobe.

HavestudentscompletethisinformationintheirActivity Log.

Note:If this concept needs further clarification, you can use two objects of the same size and shape, such as a brick and a sponge, to demonstrate that objects with the same volume can have different masses.

Note:For a standard 12”-14” globe, the atmospheric thickness is about 0.6 mm, so you will need to use very thin bubble wrap. Several sheets of plastic wrap layered together can also be used. If your globe is larger, you will need to deter-mine what you will need.



What are the Properties of Air?Explaintostudentsthatscientistshaveinvestigatedairandhavefoundittorespondinpredictableways.Theseobserv-ableandmeasureableaspectsofairarereferredtoasitsproperties.Thestudentswillconductanumberofinvesti-gationsinordertodiscoversomeofthepropertiesofair.

Property One: Air Takes up Space(Volume)

Holdthe“tornadotube”infrontofstudents.Makesurethebottlewithwaterisonthebottom.(Or,ifstudentsareinvestigatinginsmallgroups,makesurethatthebottleissetupatastationwiththewateronthebottom.)

Ask:Whatisinsidethesetwobottles?(Air is inside one of the bottles. Water is inside the other bottle.)

Ask:WhatwillhappenifIinvertthebottle?(Relatethistermtomathematicsandfractions.)Allowstudentstodis-cusswiththeirpartner.

Invertthebottles.Studentsshouldobservethatthewaterremainsontop.

Ask:Whyisthewaterstayinginthetopbottle?WhatdoyouthinkIneedtodotomakethewaterfallthrough?

Askthestudentstogivesuggestionsonhowtogetthewaterandairtoexchangeplaces.Givethemtimetoinvesti-gateandtryouttheirideasononeofthe“tornadotubes.”

Beforemovingontotheinvestigationofthepropertiesofair,askstudentstobrieflyreviewtheinformationtheyjustcoveredconcerningtheatmosphere.Askthemtoselectabitofinformationandexplainittoapartner.Oncue,haveonepartnersharewhattheylearnedfor15-30secondswhiletheotherstudentlistens.Atthesignal,havestudentsreverseroles,allowingthesecondpartnertoshare.Circulateandlistentothediscussiontodeter-mineunderstanding.Closethediscussionbyclarifyingcontentasneeded.

4 Check for Understanding:

Note:The following activities can be managed through guided, whole group hands-on inves-tigations in pairs or teams of four, or they can be managed through small group rotations through investigation stations utilizing task cards, followed by whole-group debriefs.



Afterthestudentsinvestigate,demonstratebygraspingtheapparatus(thebottlefilledwithwaterontop)andmoveitinacircularmotionuntilavortexorfunnelforms.Thespinningactionforcesthewaterawayfromthecenterofthecoupler,allowingasmallfunneltoform.Throughthevortex,theairmovestothetopbottle,makingroomforthewatertocomedownintothebottombottle.

Property Two: Air Has Mass and Weight

Ask: Posethequestion,“Weknowthatairhasmassbe-causeitismadeofmatterandallmatterhasmass.Wehavealreadydiscoveredthatairtakesupspace,orvolume,butdoyouthinkairhasweight?Whyorwhynot?”

Havestudentsharetheirthoughtsandtheirrationalewiththeirpartnerfor60seconds.

Experimental Design

Explainthatscientistsmustdevelopexperimentsthatwilltesttheirhypotheses.Tellstudentsthattheycanuseascaletomeasuretheweightofobjects.Thisisameasureofhowmuchgravityispullingdownonanobject.

Wealsoneedtohavesomethingto“hold”theairmoleculesinplacesowecanweighthem.Wewilluseabottletocapturetheairmolecules.Showthematerialstheyhaveavailabletouseforthisinvestigation-a bottle, pressurizing bottle top, and digital scale.

Tellthemtheymustdevelopaninvestigationusingthesematerialstodetermineifairhasweight.Makesuretheyunderstandthatthescaleisusedtomeasuretheweightasgravitypullsdownonthemass.Thepressuringbottletoppushesmoreairmoleculesintothebottle.

Givegroups2-3minutestoagreeonadesignfortheexper-iment.Circulatetoeachgroupandaskleadingquestionsto

Whatmakesthewatermovetothebottombottle?(Gravity pulls the water through the small opening.)

Havestudentsobservewherethewaterismoving. (The water is moving along the sides of the bottle.)

Whyisthewatermovingdownthesidesandnotdownthemiddleoftheopening?(Because the air molecules are moving up the center of the “hole” and both materials cannot occupy the same space at the same time.)

Strategic Questions:

Havestudentsverbalizethegeneralizationthatairmoleculestakeupspace—airhasvol-ume.HavestudentscompletecorrespondinginformationintheirActivity Logs.


OnEarth,wehavegravitypullingdownonevery-thing.Iftherewerenogravity,wouldwestillhavemass?Yes, we would still have mass.Withoutgravity,wouldwestillhaveweight? No, we would not have weight.




assistgroupsindesigningtheirexperiment.Makesurethatstudentsthinkofahypothesis.Forexample:IfIpumpmoreairintothebottle,itwillweighmore.

Solicitideasfromvariousgroupsandleadthemtoreal-izethatthebottlemustbeweighedtwice,oncewithoutaddedairandoncewithaddedairpumpedin.

Havestudentsopenandclosethebottlepumpertomakesurethatithasnotbeenpressurized.Tellthem,“We want to make sure we all have approximately the same amount of air in the bottle when we begin our experiment.”

ThestudentsweighthebottlewithoutaddedairandrecordthedataintheirActivity Loginatable.(Be sure they record the beginning weight in the appropriate blank.)

Explaintothestudentsthattheyaregoingtoputasmanyairparticlesinthebottleastheycanbypumpingthebottletop.Thestudentswilltaketurnspumpingairintothebottlebyrotatingthebottlearoundthetabletoeachstudent,changingevery15secondsoncue.

Thestudentswillweighthebottleasecondtimeandre-cordthedata.

Weight of Bottle and AirEndingweight __._gBeginningweight __._gDifference __._g

Ask:Whathappenedthesecondtime?(The weight mea-surement increased as we pumped in more air.)

Note:A spring scale (like a bath-room scale) measures the amount of force required to hold up an object against the force of gravity. When an object is at rest on a scale, the upward force that the scale exerts on the object equals the downward force of gravity on that object. This is how a scale measures the weight of the object.

Leading Questions:What is your plan?When you put the bottle on the scale, what are you weigh-ing?How will you know how much of the weight is from the bottle cap and how much, if any, is from the air?What is the minimum number of times you would have to weigh the bottle?

Confirmwitheachgroupthatthebottleweighedmorethesecondtimebecauseoftheaddedair.AskDoes this prove that air has weight?


Howcouldwedeterminehowmuchmoretheaddedairmassweighed?(In math, you subtract to determine the difference, so we could subtract the beginning weight measurement from the ending weight.)




Havestudentsrecalltheirinitialhypotheses.Studentsshouldstateiftheirfindingssupportedordidnotsupporttheirhypothesis.Makesuretodiscussthatdisprovinginitialthoughtsisjustasimportantasfindingoutthatyouwerecorrect!

Property Three: Air Exerts Pressure in All Directions

Explainthatairpusheswith14.7lbsofpressurepersquareinchinalldirectionsatsealevel.Putabowlingballonthetableandletitbangdown.Drawasquareinchonthetabletopwithawashableoverheadmarkerandtellthemthatairispushingwiththeweightofthatbowlingballonjustthisonelittlesquare.Nowimagineifwecouldplacetheweightofthebowlingballoneachoftheoneinchsquares.Thatwouldmeanthateverysquareinchwouldbecoveredonthistabletopwithbowlingballs,withalloftheirweightpushingdownonthetabletop.That’swhatairisactuallydoingtothetable;pushingdownonthetabletopwiththeweightofabowlingballoneverysquareinch!

Ask:Whydoesn’tthetablecollapsefromallofthepoundsofpressurepushingonit?

Pointoutthatalthoughthetablelegsareverystrong,theycouldnotsupportthatmanybowlingballs.Leadthestudentstorealizethatairisnotonlypushingdownfromabove,butalsoupfrombelowandsidetoside.Thereisequalpressureonallsides.Havethestudentsholdouttheirhand,palmup.Havethemplacetheirotherhandontop,palmdown.Tellthemtopushdownwithonehandandupwiththeotherwithequalforce.Nomatterhowhardtheypush,iftheforceisequal,nothingmoves.Thisbalanceofforcesisreferredtoasequilibrium.

Havethestudentsthinkabouthowairispushingontheoutsideoftheirbodiesinthesameway.Drawasquareinchonyourarmandhavethemimagineallthebowlingballspushinginontheirbodies.

Ask:Whyarewenotcrushedbytheforce?

Guidethediscussionforthestudentstounderstandthatairisexertingpressureoneverythingittouches.Notonlyisthereairoutsideourbodiespushingin,butthereisairandotherfluidsinsideourbodiespushingoutwithequalforce.Iftherewerenopressureinsideourbody,thepressureoftheoutsidewouldcrushus.

Note:You can use a drilled bowling ball that measures 14.7 lbs or an equivalent object that is 14.7 lbs (such as a sack of flour).

Whatdoesitdemonstrateifthemeasurementisthesameafteryoupumpthebottlewithmoreair?(That air does not have weight.)

Whatdoesitdemonstrateifthemeasurementchangesafteryoupumpthebottlewithmoreair?(That air has weight.)

Whymustweconductthisinvestigationmorethanonce?(To confirm the results are valid.)




Ask:Thereislittleornoatmosphereinspace.Whatdoyouthinkwouldhappenifanastronautwentoutintospacewithoutapressurizedspacesuittoprotecthisorherbody?

Explainthattherewouldbeairandfluidsinsidetheastro-naut’sbodypushingoutward,butsincethereislittleatmo-sphereinspace,therewouldnotbeanyairpushinginwardonthebody.Thiswouldcausetheastronaut’sbodytoexplode.

Provideeachpairofstudentswithabelljarwithtubing,asy-ringe,andamarshmallow.Showthestudentsthattheywillplace themarshmallow inside thebell jar. Insert the tubeintothebelljarandattachthesyringetothetube.Explainthatthemarshmallowrepresentstheastronautandthebelljarrepresentsspace.Havethestudentspullbackonthesy-ringe.Thiswilldrawairoutofthejar.Whenair isremovedfromthebelljar(simulating conditions in space),thefluidin-sidethemarshmallowcontinuestopressoutward(simulat-ingthefluidpressureinsideourbodies).Asair isremovedfromthejar,themarshmallowwillexpand.

Demonstratethatthebelljarcannotbelifted.Askthestu-dentswhy. (The air on the outside of the jar is pushing in on all sides but there is no air on the inside to press outward. This creates an unbalanced force acting inward on the bell jar.)Al-lowthemtopredictwhatwillhappenwhentheyallowtheairtoflowbackin.Havethestudentstwisttheconnectoronthetoptoreturntheairintothebelljar.Themarshmal-lowwillshrink,andtheywillonceagainbeabletoopenthejar.Havethestudentsobserveresultsanddiscuss.

Revisittheinvestigationoftheballoonintherefrigerator.Haveavolunteermeasureandrecordthecircumferenceoftheballoon.Thestudentsshouldseethatthecircumferenceoftheballoonhasdecreasedbecausethecolderair(after refrigeration)takesuplessspacethanthewarmerairdid.

Ask:Whichdoyouthinkexertsmorepressure,warmairorcoldair?Why? (In warm air, the molecules are farther apart. Therefore, they will probably exert less pressure.)

Ask:Howdoyouthinkdifferencesinairpressurerelatestowindflow?(The wind will flow from areas of higher pressure to lower pressure.)

Ask:WhatdoyouthinkwouldhappentoyouifyouwenttoaplanetthathasamuchdenseratmospherethanEarth? (You might be crushed.)

Note:Although not as dramatic as the bell jar, this activity can be conducted using mini-marsh-mallows and syringes without the bell jar. The students place the marshmallow inside the syringe, place their finger over the hole in the end and pull the plunger back slightly. This expands the volume inside the syringe, causing the air molecules the spread out. This decreases the air pressure inside the syringe, causing the marshmallow to expand. When the plunger is pushed back in, the marshmallow will shrink.

Doyouthinkthatairpres-sureisthesameevery-where?WhyorWhynot?

Whatdoyouthinkmaycauseairpressuretochange?(Elevation, vacu-ums, compressed air streams, heating and cooling of molecules)




Thisisoneofthereasonswhyanastronautmustwearaspacesuitinspace.Theabsenceofairpressureontheout-sidewouldallowthefluidontheinsidetoexpand,causingtheastronaut’sbodytoexplode.

HavestudentscompletetheinformationaboutairpressureintheirActivity Logs.


Air Is a Fluid

ReferbacktotheglobemodelofEarth.Havestudentsiden-tifythesolidmatterontheglobe (landforms),theliquidmat-terontheglobe(oceans, lake, rivers) andtheinvisiblegases(the atmosphere).Remindthemthatsolids,liquids,andgasesarethreeofthestatesofmatterpreviouslystudied.

Askstudentsiftheyarefamiliarwiththesubcategoryofmatter,“fluids.” Tellthemthatwearegoingtoconductatesttodeterminewhethersolids,liquids,orgasesalsobelonginthesubcategoryoffluids.Allowthemtodiscusswiththeirpartnerswhetherornottheythinkeachofthesestatesofmatterisafluid.

Explainthatbydefinition,afluideasilychangesitsshape.Themoleculeswillseparatesoyoushouldbeabletoputyourhand(oranotherobject)intoafluid.Afluidcanalsobepoured.

Todemonstrate,carryoutthefollowing:

Pickupasolidobjectsuchasarock.

Ask:Doesthisobjecthaveadefiniteshape?Isitkeepingitsshape?(Yes)CanIputmyhandinit?(No)CanIpourit? (No)

Usingatable,havestudentsdeterminewiththistestthatasolidis not afluid(See sample table).

What is a FLUID?Afluid:

• doesnothaveitsownshape

• separatesandflows

• canbepoured

Isasolidafluid? YES NO

Isaliquidafluid? YES NO

Isagasafluid? YES NO



Withanaquariumofwaterandaflask,repeatthethreetestswithaliquid.Usingthetable,havestudentsdeter-minewiththistestthataliquidisafluid.

Usingthesameaquariumandtwoflasks,repeatthethreetestswithagas(air).Whendeterminingifagascanbepoured,pushoneflaskintotheaquariumrightsideup,allowingittofillwithwater,andturntheotherflaskupsidedown,keepingitfullofair.Carefully“pour” theairunderthewaterfromoneflaskintotheother.Thestudentscanobservethebubblesofairenteringtheflask.

Usingatable,havethestudentsdeterminewiththistestthatagasisafluid.Therefore,thegasesintheatmospherehavefluidproperties.

Conclusion:

Understandingabouttheairisimportantinmanyscientificinvestigationsandwillbeimportantinhelpingusinunder-standingaeronautics.

Air is made up of mainly three types of gas molecules: 78% nitrogen, 21% oxygen, and 1% of trace gases.

Air that is closer to the surface of Earth is denser and exerts more pressure on objects.

Air takes up space. The volume increases as air becomes warmer.

Air has mass and weight.

Air exerts pressure in all directions. Pressure decreases with altitude.

Air is a fluid.

ActivityLog


ATMOSPHEREAbout_______milesthick.

Fluid Investigations Activity

Theatmosphereistheblanketof _________thatsurroundsEarth.Itismadeupofparticlessosmallyoucan’tseethemaroundyou.Theyareheldinplaceby_________.

Ocean of Air

The Gases in the Atmosphere

TypeofGas

NumberofParticlesper100

EquivalentFraction

DecimalEquivalent

PercentageofGasesin

theAtmosphere

Nitrogen(Blue)

—100

0.__ __%

Oxygen(Red)

—100

0.__ __%

WaterVaporandTraceGases

(White)

—100

0.__ __%

FartherfromthesurfaceofEarth,theairis_________dense.

ClosertothesurfaceofEarth,theairis____________dense.

Increasing Altitude

Elevation and Air Density

ActivityLog


Fluid Investigations Activity

Experiment#1:___________________________

Airmoleculeshave_______________.

Airmoleculestakeup_______________.

The Properties of Air

Experiment#2:___________________________

Airmoleculeshave__________.Whatistheforceofgravityactingdownwardonanobject?__________

Weight of Bottle and AirEndingweight____.__gBeginningweight____.__gDifference____.__g

Airmoleculesexert____________inalldirections.




• canbepoured




Experiment#3:_______________________________________

Thisshowsusthat________________________.

WhenairistakenOUTofthejar,themarshmallow____________.

WhenairisputbackINthejar,themarshmallow____________.

ActivityLog


Fluid Investigations Activity Key

Experiment#1:Tornado Tube

Airmoleculeshavevolume.

Airmoleculestakeupspace.

The Properties of Air

Experiment#2:Mass and Weight

Airmoleculeshavemass.Whatistheforceofgravityactingdown-wardonanobject?weight

Weight of Bottle and AirEndingweight____.__gBeginningweight____.__gDifference____.__g

Airmoleculesexertpressureinalldirections.




• canbepoured




Experiment#3:Marshmallow in bell jar

Thisshowsusthatair is a fluid.

WhenairistakenOUTofthejar,themarshmallowexpands.

WhenairisputbackINthejar,themarsh-mallowreturns to its original size.

ActivityLog


Fluid Investigations Activity Key

Theatmosphereistheblanketof gasesthatsurroundsEarth.Itismadeupofparticlessosmallyoucan’tseethemaroundyou.Theyareheldinplacebygravity.

ATMOSPHEREAbout100milesthick.

Ocean of Air

The Gases in the Atmosphere

TypeofGas

NumberofParticlesper100

EquivalentFraction

DecimalEquivalent

PercentageofGasesin

theAtmosphere

Nitrogen(Blue)

78 78—100

0.78 78%

Oxygen(Red)

21 21—100

0.21 21%

WaterVaporandTraceGases

(White)

1 1—100

0.01 1%

Oxygen Traces of gases

Nitrogen

FartherfromthesurfaceofEarth,theairislessdense.

ClosertothesurfaceofEarth,theairismoredense.

Increasing Altitude

Elevation and Air Density


Fluid Investigations Assessment

1. Whatarethemajorcomponentsoftheatmosphere?Whatpercentageofeachisfoundunderordinaryconditions?

2. Inwhichcitywouldtheairbemoredense,NewOrleansatsealevel,orDenver,the“MileHigh”City?(1mile=5,280ft.)Whichcitywouldhavehigheratmosphericpressure?Explainyouranswer.

3.Whatisthedifferencebetweenweightandmass?

4. Howistheatmospheresimilartotheocean?

Suggested Final Assessment Questions


1. Whatarethemajorcomponentsoftheatmosphere?Whatpercentageofeachisfoundunderordinaryconditions?

Possible answer: nitrogen 78%, oxygen 21%, water vapor mixed with other gases and particulate matter 1%.

2. Inwhichcitywouldtheairbemoredense,NewOrleansatsealevel,orDenver,the“MileHigh”City?(1mile=5,280ft.)Whichcitywouldhavehigheratmosphericpressure?Explainyouranswer.

Possible answer: The air in New Orleans would be more dense and have more pressure because there would be many more air molecules above you, pushing molecules together. Denver is higher in elevation, and there would be less air on top push-ing down, so the molecules would be able to spread further apart. Therefore, it would also have less pressure.

3.Whatisthedifferencebetweenweightandmass?

Possible answer: Mass is the amount of matter in an object. Weight is the force of gravity pulling on a object. If you have more mass, there are more molecules for gravity to pull on, so you have more weight.

4. Howistheatmospheresimilartotheocean?

Possible answer: The ocean and the air are both large bodies of fluids that wrap around everything they touch. They both have volume, mass, weight, and pressure. Neither the ocean nor the air has a definite shape (their shapes continually change). The molecules in the atmosphere and ocean separate and flow, and both can be poured.

Knowledge

Application

Analysis

Synthesis

Suggested Final Assessment Questions

Fluid Investigations Assessment Key



Sources http://www.school-for-champions.com/science/definitions.cfmKids Discover: Matter. www.kidsdiscover.com.Volume 18, Issue 10, Oct 2008.http://weather.about.comhttp://www.turblex.com/altitude/index.cfmhttp://www.nasa.gov/audience/forstudents/9-12/features/912_liftoff_atm.htmlhttp://hubble.nasa.gov/http://nasa.gov/worldbook/earth_worldbook.htmlhttp://www.soest.hawaii.edu/GG/ASK/atmonitrogen.html

e 3.1.1.2. chemistry sciences: c. atmospheric properties ... investigations 05... · density of...

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