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Name:
Section:250-_
Period:_
Experiment 20 - Prersur€-VolumeRelationship in cas€s
The primary objectiveofthis €xperimentis to determinethe relationshipbetweenthe presswe
andvolumeof a conlined gas.The gaswe usewill be air, andit will be confinedin a iyringe
connected
to a Pressure
Sensor(seeFigure1).Whenmovingthepistonchanges
thevolumeof
thesyringe,a changeoccursin thepressure
exertedby theconfinedgas.Thispressure
change
wrll bemonrtored
usinga Pressure
Sensor.
It is assumed
thattemperatuewill be consran
tltougbouttheexperiment.
Pressure
andvolumedatapalrswill bi collectedduringthis
experimentandthen analyzed.From the dataand graph,you shouldbe ableto determinewhat
kind ofmathematicalrelationshipexistsbetweenthe pressureandvolume ofthe conflred gas.
Historically, this relationshipwas fust establishedby RobertBoyle in 1662andhassincebeen
knownasBoyle'slaw.
Purpose:In this expedment
you will:
a. Usea GasPressureSensorand a gass1'ringeto measwethe pressureofan air sampleat
severaldifferent volumes.
b. Determinethe relationshipbetweenpressureandvolumeofthe gas.
c. Describethe rclationshipbetweenpressureand volumein a mathematicalrelationship.
Figute I
PROCEDURE
1. Preparethe PressureSensorandan air samplefor datacollection.
a. With the 20-mL syringedisconnectedftom the PressweSensor,move the pistonof the
syrirgeurtil thefrontedgeof$e insideblackring(indicared
by theanourinfigureI r is
posrtroned
aI lhe lU.UmL mark.
b. Attachthe20-mLryringeto thevalveofthe Pressure
Sensor.
69
thecomputerfor datacollectionby openingthefile "06 Boyle'sLaw" from the
2. Prepare
Chemistrywith Vernierfolderof LoggerPro.
3 . To obtainthebestdatapossible,you will needto conectthevolumereadingsfrom the
sy nge.Iaok at thesyringe;its scalereportsits own internalvolume.Howevel,thatvolume
is noathetotalvolumeoftrappedair in yoursystemsincethereis a lidle bit of spaceinside
thepressure
sensor.
To accountfor theextravolumein thesystem,you will needto add0.8 mL to yoursyringe
readings.
For example,with a 5.0 mL syringevolume,thetotalvolumewouldbe5 8 mL.1ti!
this total rolune thai you will needfor the analysis.
4 . Click It c.[*tl to begindatacollection.
v.r.volumedata.Itis bestfor onepersonto takecareof the 8assyringe
5. Collectthepressure
another
to
operate
the computer.
andfor
a. Movethepistonto positionthefront edgeof the insideblackring (seeFigure2) at the
value
5.0mL line on thesyringe.Hold the pistorfirmly in this positiol until the pressure
stabilizes.
Figure 2
click[6 x*p l. (Thepersorholdingthes]Tinge
readinghasstabilized,
b. when thepressure
canrelaxafter[6 r*p ]is ciicked.)Typein thetotalgasvolume(in thiscase,5.8mL) in the
you areadding0.8 mL to the volumeof thesyringefor thetotal
editbox.Remember,
key to keepthisdatapair.Note:You canchooseto redoa point
volume.PresstheENTER
by pressingtheEsc key (afterclickinglaK;tl but beforeenteringa value)
readinghasstabilized,click@
c. Move thepistonto the7.0 mL line. Whenthepressure
andtypein thetotalvolume,7.8mL.
for syringevolumesof 9.0, 11.0,13.0,15O,17-0,and19.0mL
d. Continuethis procedure
e. Click lis.p lwhen you havefinishedcollectingdata.
andvolumedatapairsdisplayedin thetable(or,if
6. In yourdatatable,recordthe pressure
your
print
of thetable).
instructor,
a
copy
directedby
v.t-volume.Basedon this graph,decidewhatkind of
7. Examinethe glaphof pressure
To
dirbctor inverseyou
think
existsbetweenthesetwo variables,
mathematicallehtionship
seeif youmadethe rightchoice:
a. Click theCurveFit button,m.
b. ChooseVariablePower(l = Ar^n) from theIist at thelowerleft-Enterthe powervalue,n,
shownin thegraph(e g.' typeI if
therelationship
in thePoweredit boxthatrepresents
Clickfl'vti, ,.
direct,-l if inverse).
70
c. A bestht curvewill be displayedon thegaph.If you madethecorrectchoice'thecurve
turvedoesnotmatchupwell'trya differenl
shouldmatchuDwell\ ithihepoints.lf t"he
again.Whenthecurvehasa goodfit with the datapornts'then
.ii"r.lArl
"ipon.qaqa
click I o'( l.
8.
Onceyou haveconfirmedthat the glaph representseither a direct or invcrserelationship,
pdnt a copyofthe Graphwindow,with thegraphofpressurels. volumeandits best-fi.
curvedisplayed.Print a copy for eachmemberof your lab group. Under the File merluselect
Print G/6ph. Click the box Prlar Fooler. T)?e your nameand your lab parb1er'snane in
theNamebox. Click OK. Whenthe Prirl box appears,selectthe printerScience3'dFloor
Mezzaninear'dp.jnt enoughcopiesso that eachmemberof your gioup hasa copy.
DATA AXD CALCULATIONS
voiune (mI-)
Pressurc(kPa)
k= P*v
71
F
PROCESSING THE DATA
1.
If the volumeof the gasis doubledfrom 5.0 mL to 10.0mL, wha. happens.o the pressure?If the pressure
changes,by how much doesit change?
2.
to thepressure?
If thepressure
ff thevolumeoflhe gasis cut in half,from 20.0mL to 10.0mL, whathappens
changes,by how much doesit change?
3.
to lhe pressu(e?
If thepressure
If ihevolumeof the8asis tripledfron 5.0mLto 15OmL, lvhalhappens
changes,by how much doesit change?
4.
Basedon your answersto the frrst threequestionsandthe shapeof the curve in the plot of pressureas it
pressure
andvolumedirector indirecl?Explain.
depends
on volume,;stherelalionship
between
l
I
5.
One way to d€termineif a relationshipbetweentwo variablesis direcl or inverseis to find a propoiionality
is inverse,
is directthenk = P,^r'.If lhe relationship
constant,
k. from thedatacollectcd.Iflhe relationship
andrecordthe valuesfor P r' andP+Vfor eachpa;r
thenk=P*V. In thetableon thepreviouspagc.calculate
and volume direcl or
of datacollected. Basedon thesecalculations.is the relationshiDbetweenDressure
inverse?ExDlainvourchoice.
b.
W h a l e rp c ri mc n tj l fa c ro l | sa) re hel dcon\bnr i n !hrserp€ri mcnl ?
'72
7.
Basedon your resultsandyour answersto the quesrionsabove,wrile a verbal staremenrthat expressedBoyle's
I-aw.
8.
Basedon yourresultsandyouranswers
to lhequestjons
above,14ritea mathemalical
equarion
thatexpressed
Boyle\ taw.
Conclusion:
73