= MAPUAINSTITUTEOFTECHNOLOGY
DepartmentofPhysics
E302:HeatandCalorimetry
XXXXXXXXXXXXX
2005XXXXXXXXXX,Group1
PHY130LXX
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SAMPLECOMPUTATIONS
PartI.DeterminingtheSpecificHeatofMetals
Given:
mm 31.6 g
mc = 47 g
m w = 198.8 g
T0 m = 81 C
0
Solution:
T0 w = 27 0 C
Tmix = 290 C
Cw =
1cal
g C0
T0c = Tw = Tmix T0 w
Tm = Tmix Tm
T0c = Tw = 29 0 C 27 0 C Tm = 29 0 C 810 C
T0c = Tw = 2 0 C
Tm = 52 0 C
m c T + m w c w Tw
C m exp erimental = c c c
m m Tm
ExperimentalSpecificHeatofMetal
( 47 g ) 0.217cal 2 0 C + (198.8 g ) 1cal 0
0
g C
g C
C m exp erimental =
( 31.6 g ) 52 0 C
cal
C m exp erimental = 0.254380477
g C0
(
)
(
% error =
% error
% error
AV EV
AV
)
0
2 C
x100%
cal
cal
0.2174
0.254380477
0
g C
g C0
=
cal
0.2174
g C0
= 17.01%
x100%
(
)
PartII.LatentHeatofFusionofIce
Given:
mc = 47 g
T0 w = 29 0 C
m w = 187.7 g T = 22 0 C
mix
mi = 14 g
1cal
Cw =
0
T0i = 0 C
g C0
mc c c Tc + m w c w Tw + mi c w Tice water
mi
Tice water = Tmix T0 w
T0c = Tw = Tmix T0 w
0.217cal 0 0
1cal 0
7C
( 47Tc = Tw0 = 22 7C C 29 (0187.7 g )icewater =0 22 C0 0 0+C(14 g ) 1cal 0
g )0
+ C T
g C
g C
g C
= Tc = Tw = 7 0 C
Tice water = 22 0 C
0
(14 g )
cal
= 76.9495
g C0
ExperimentalLatentHeatofFusion
L f exp erimental =
Solution:
L f exp erimental
L f exp erimental
% error =
% error
AV EV
AV
(
)
x100%
cal
cal
80
g C 0 76.9495 g C 0
=
cal
80
g C0
% error = 3.81%
(
x100%
)
0
22 C
(
)
GUIDEQUESTIONS
PartI.
1. Expressequation1intermsofmass,specificheats,finalandinitialtemperature.
Qloss = Q gained
mcT = mcT
mc(T f Ti ) = mcT (T f Ti )
2. Whyisitimportanttoimmersethemetalintheboilingwaterforalongtime?
Whathappensifthemetalwasimmersedonlyforashortwhile?
Itisimportanttoimmersethemetalinboilingwaterforalongtimeinorder
forthemetaltoattainthermalequilibrium,Ifthemetalwasimmersedonlyfora
shortwhiletheinitialtemperatureofthemetalwouldhavebeenfalse.
3. Why do you need to wipe of the metal surface before taking the initial
temperature?
Youneedtowipeofthewatersothattheinitialtemperatureofthemetal
isntaffectedbythetemperatureofthewater.
4. What is your computed specific heat and percentage error? Is it acceptable?
Why?
ThecomputedC=0.254cal/g 0Cand17%errorisacceptable;sinceitisnotan
isolatedsystemandmanyfactorssetin,itishardtogetanaccuratereading.
5. Whatarethesourcesoferrors?Whatareyourrecommendations?
Irecommendhavingsomeonewithanaccurateyetfasteyetomonitorthe
temperaturereadingsandrepeattheexperimentstogetanaccurateresult.
PartII.
1. Showyourderivedformulaindeterminingthelatentheatoffusionoficeusing
thelawofheatexchange.
Qloss = Q gained
mcT + mL = mcT + mL
mc(T f Ti ) + mL = mcT (T f Ti ) + mL
2. Whatistheinitialtemperatureoftheice?Whatassumptionsdidyoumaketo
determinetheinitialtemperatureoftheice?
00C,sinceiceandwatercoexistonlyat00Cweeassumeditwascorrect.
3. Whyisitimportantowipeoffthewaterfromtheicessurfacebeforeputtingitin
thecalorimeter?
The surface of the ice waswiped of to remove the thermal change of
watertogetherwiththeice,bydoingsowecanconcentratepurelyonthephase
changeofice.
4. Hadthemassoficebeengreater,howwoulditaffecttheresultoftheexperiment
andthecomputedlatentheatoffusion?
Hadthemassoftheicebeengreaterthecomputedlatentheatoffusion
andexperimentalvalueswouldhavebeenthesame.
5. Whatarethesourcesoferrorsandyourrecommendation?
Irecommendhavingsomeonewithanaccurateyetfasteyetomonitorthe
temperaturereadingsandrepeattheexperimentstogetanaccurateresult.
REMARKSANDCONCLUSION
Thermodynamics is the study of energy and its transformations; of particular
interestisthe relationship between heat and work.One of the fundamental tools
thermochemistry, in a branch of thermodynamics, is calorimetry. Calorimetry is the
measurementofheatflow.
Heatcanonlybeidentifiedasitisbeingtransferredfromonesystemtoanother.
Heattransferisapathfunction(processquantity),asopposedtoapointfunction(state
quantity). Heatflowsbetween systemsthatare notin thermal equilibriumwith each
other; it spontaneously flows from the areas of high temperature to areas of low
temperature. All systems (matter) have acertainamount of internal energy.Internal
energyisapropertythatisameasureofallmicroscopicwaysbywhichasystemcan
possessenergy,forexampletherandommotionofitsatomsormolecules.Whentwo
bodiesofdifferenttemperaturecomeintothermalcontact,theywillexchangeinternal
energy until their temperatures are equalized; that is, until they reach thermal
equilibrium.Theamountofheattransferredisequaltotheamountofenergyexchanged
betweenthetwobodies.Itisacommonmisconceptiontoconfuseheatwithinternal
energy.Ahotobjectdoesntcontainheatitcontainsinternalenergy.Theadjective hotis
usedasarelativetermtocomparetheobjectstemperaturetothatofthesurroundings
(orthatofthepersonusingtheterm).Thetermheatisusedtodescribetheflowof
energy.Intheabsenceofworkinteractions,theheatthatistransferredtoanobject
endsupgettingstoredintheobjectinforminternalenergy.
Specificheatisdefinedastheamountofheatthathastobetransferredtoor
fromoneunitofmassormoleofasubstancetochangeitstemperaturebyonedegree.
Specific heat is a property, which means that it depends on the substance under
considerationanditsstateasspecifiedbyitsproperties.Fuelswhenburned,release
muchoftheenergyinthechemicalbondsoftheirmolecules.Uponchangingfromone
phasetoanother,apuresubstancereleasesorabsorbsheatwithoutitstemperature
changing.Theamountofheattransferduringaphasechangeisknownaslatentheat
anddependsprimarilyonthesubstanceanditsstate.
Calorimetersaredesignedtobewellinsulated,sonoheatisgainedfromorlost
tothesurroundings.Ifnoheatingelementisusedtointroduceheatinthesystem,the
totalheattransferred(q)fortheentirecalorimetersystemmustequalzero. Toensure
the validity of the experiment one must have an accurate and precise temperature
readingandavoidanymovementsthatmayleadtothermalleakage.Thetotalheatcan
be split into heats for each component in the system, which is heat loss and heat
gained.
Calorimetrycanbeappliedineverydaylife,fromthereactionsinsideourbodyto
thepowerplantsusedtopowerourhomes.
FREESPACE
REFERENCE
http://en.wikipedia.org
http://www.britannica.com
http://www.chm.davidson.edu
http://www.space.com/scienceastronomy.html
AmazingEarthFacts
We live on a sphere of extremes and oddities. In fact it's not really a sphere, but it is a wild planet, mottled
with deadly volcanoes, rattled by killer earthquakes, drenched in disastrous deluges. But do you know
which were the worst?
1. What is the hottest place on Earth?
Count one wrong if you guessed Death Valley in California. True enough on many days. But El Azizia in
Libya recorded a temperature of 136 degrees Fahrenheit (57.8 Celsius) on Sept. 13, 1922 -- the hottest
ever measured. In Death Valley, it got up to 134 Fahrenheit on July 10, 1913.
2. And the coldest place around here?
Far and away, the coldest temperature ever measured on Earth was -129 Fahrenheit (-89 Celsius) at
Vostok, Antarctica, on July 21, 1983.
3. What makes thunder?
If you thought, "Lightning!" then hats off to you.
But I had a more illuminating answer in mind.
The air around a lightning bolt is superheated to
about five times the temperature of the Sun.
This sudden heating causes the air to expand
faster than the speed of sound, which
compresses the air and forms a shock wave; we
hear it as thunder.