GUIDE QUESTIONS Part 1. 1. Express equation equation 1 in terms of mass, specic specic eats, na! an" initia! temperature. Q Loss =QGained Σ Q Loss + Σ QGained =0 mc Δ T ¿ ¿ Lo ss+ mc ΔT ¿ ¿Gained =0 mc ( t −t o ) ¿ Loss + mc ( t − t o ) ¿Gained = 0
#. $% is it important important to immerse immerse te meta! meta! in te &oi!in' &oi!in' (ater for a !on' time) $at appens if te meta! (as immerse" on!% for a sort (i!e) It is important that the metal is immersed completely for a long time so that the boiling water would properly heat the metal. Immersing the metal for a short time would not yield accurate results. •
*. $% "o %ou nee" to (ipe (ipe o+ te (ater (ater from te meta!s meta!s surface &efore ta-in' te initia! temperature) It is needed to wipe of the water from the metal so that tha t the temperature of the water would not aect the temperature temperature of the mixture, mixture, which is the metal and the water inside the calorimeter. •
. $at is %our compute" compute" specic specic eat an" percenta'e percenta'e of error) error) Is it accepta&!e) $%) The computed specic heat is 0.2211 0.2211 calg!"# and the percentage percentage error error is 1.$%&$'. I thin( it)s acceptable since we got a minimal percentage error error and 0.2211 is *uite near to the actual specic heat which is 0.21&+ calg!"# •
/. $at are te sources of errors) $at are %our recommen"ation recommen"ations) s) The possible bases of errors errors in performing performing the experiment experiment are the time time the metal is immersed in boiling water. -rrors can be minimied if we immerse the metal for a long period of time. It can be minimalie be calculating it near the boiling water to a/oid the cold air that also a lso aect the experiment. The temperature temperature of the room is also another source of error since we are performing in the laboratory with well air!conditioned air!conditioned room. erforming erforming the experiment experiment fast and consistent can minimie this. lso, errors may ha/e happened during the recording of the initial temperature of the metals, which was *uite hard to record. nother source of error may ha/e been the excess water clinging on the metal)s surface, which was not wiped o before •
putting in the calorimeter.
Part #.
1. So( %our "eri0e" formu!a in "eterminin' te !atent eat of fusion of ice usin' te !a( of eat excan'e. |¿|= 0
Σ Q Rel + ΣQ¿ mc ΔT ¿w +mc Δ T ¿ c + mi Lf + mi c w ∆ T i +w =0
( mw c w+ mc c c )( T mix −T ow ) −mi cw T mix ¿ −¿ L f =¿
#. $at is te initia! temperature of te ice) $at assumptions "i" %ou ma-e to "etermine te initia! temperature of ice) The temperature of the ice is assumed to be ero degrees because at that temperature both the solid and li*uid state of water is present. •
*. $% is it important to (ipe o+ te (ater from te ices surface &efore puttin' it in te ca!orimeter) •
It is important to wipe o the water from the ice)s surface before putting it in the calorimeter because it can aect the initial temperature.
. a" te mass of ice &een 'reater, o( (ou!" it a+ect te resu!t of te experiment an" te compute" !atent eat of fusion) •
If there will be a dierent mass of ice, then the latent heat will depend on the mass of the ice. ass of ice is in/ersely proportional to the latent heat. If
mass of ice is greater than its initial, then the latent heat will decrease.
/. $at are te sources of errors an" %our recommen"ation) •
The possible errors are because of the room temperature, since we are performing in the laboratory with air!conditioned room3 performing the experiment fast and consistent can minimie it. The mass of ice before and after putting it in the calorimeter is also another source of error. sudden change in the mass of ice will result to an error. In able to minimie the error, we must wipe o the excess water in the ice before putting it in the calorimeter.
S23P4E 5O3PUT2TION
Part 16 24U3INU3 Specic eat of 2!uminum 3eta!6 c m=
−(mw c w + mc c c )( T mix −T ow ) mm ( T mix −T om)
c m=
−[ ( 168.2 × 1 )+ ( 46.4 × 0.2174 ) ]( 30 −27.5 ) (31.5)( 30−94 )
c m= 0.2211 cal / g −C °
Percent Error6
|
c mactual− c mexperimental
|
0.2174
error =
error =
c mactual
|
× 100
|
−0.2211 × 100
0.2174
error =1.6976
Part #6 Tria! 1 4atent eat of 7usion6
( mw c w+ mc c c )( T mix −T ow ) −mi c w T mix ¿ −¿ Lf =¿
Lf =
−[ ( 234.8 × 1 ) +( 46.4 × 0.2174 ) ( 38 −42.7 )−( 26.1 × 1 × 38 ) ] 26.1
Lf =82.0985 cal / g
Percent Error6
|
error =
Lfactual − Lf experimental
|
error =
Lf actual
− 82.0985
80
80
|
× 100
|
× 100
error =2.5560
2N248SIS 4or the rst part, water was boiled in the bea(er and then metal was immersed in it, one metal at a time. It was important to immerse the metal in the boiling water for a long time because we need to heat up the metal to absorb heat from the boiling water, so that if we transfer the metal in the calorimeter, we can get less error as a result. 5owe/er, if we immerse the metal for a short period of time, the metal will not absorb much heat that will heat up the calorimeter.
The metal should absorb the heat for a long time rst before measuring its temperature using a thermometer. The excess water that was on the metal was then wiped o because it can aect the initial temperature. The water in the metal has dierent a temperature than the metal itself and so that can result in an error for the experiment. 6nce the initial temperature was measured the heated metal was then placed inside the calorimeter. It was then closed and was mixed using the stic(. fter a few minutes, the nal temperature of the calorimeter was measured. 7sing the 8aw of 5eat exchange, a deri/ed e*uation was made to sol/e for the specic heat of the metal. The aluminium metal being heated by hot boiling water held in a bea(er. The temperature was measured and the excess water was wiped o to reduce error and was transferred to the calorimeter. Then the second part of the experiment is about the 8atent heat of fusion of ice, the goal is to get the latent heat of fusion of ice. 9ame in part one, we measure the calorimeter, water and the temperature of water and ice. :e put the ice in the calorimeter and melt it. 6ur initial temperature of ice is 0#". :e get the /alue of mass of ice by subtracting the total mass from the water and calorimeter. nd once the ice is being mo/ed into the calorimeter, it is important to wipe o the water from the surface of the ice, because excess water can aect the mass of the ice when measuring it after melting it in the calorimeter. 9ince we don;t need the excess water, we could rather wipe it o to get less error. If there will be a dierent mass of ice, then the latent heat will depend on the mass of the ice. ass of ice is in/ersely proportional to the latent heat. If mass of ice is greater than its initial, then the latent heat will decrease.
5ON54USION Thermodynamics studies the energy and its intercon/ersions with which all forms of energy follows the rst law of thermodynamics since energy in uni/erse is always constant. The internal energy inside a system is the total sum of the potential energy
and (inetic energy but usually termed as the sum of heat and wor(. :or( primarily focuses on the expansion or compression of the system. 5eat is the energy in motion that causes temperature and phase change in a system. "alorimetry *uantitati/ely measures the heat for both types of changes. Temperature change occurs when there is absorption or discharge of heat without causing the matter to e/ol/e. Temperature is directly proportional to heat. hase change occurs when there is phase transition at a constant temperature. The process is endothermic when heat is gained and exothermic, otherwise. 9pecic heat capacity, c, is the energy needed to raise the temperature of one gram of a substance by one degree "elsius or
MAPÚA INSTITUTE OF TECHNOLOGY
E9PE:I3ENT *;#6 E2T 2ND 524O:I3ET:8 :2
Name
Pro'ram=8ea r Su&?ect=Sect ion Part 1: Determining the Specific Heat of Metals
Group No.
5E>*
Seat No.
;#
P81#4 @ <#
Date
3a% /, #;1/
ass of metal, mm
Trial 1. luminum etal >1.? g
ass of calorimeter, m c
+$.+ g
+$.+ g
ass of water, m w
1$@.+ g
12$.? g
Initial temperature of metal, t om
%+ #"
%> #"
Initial temperature of calorimeter, t oc
2&.? #"
2% #"
Initial temperature of water, t ow
2&.? #"
2% #"
4inal temperature of mixture, t mix
>0 #"
>1 #"
-xperimental specic heat of metal, c m
0.221 calg!"#
0.0@%0 calg!"#
ctual specic heat of metal, c m
0.21&+ calg!"#
0.0%1& calg!"#
ercentage of error
1.$%&$ '
2.%>2+ '
ass of calorimeter, m c
Trial 1 +$.+ g
Trial 2 +$.+ g
ass of water, m w
2>+.@ g
2>+.@ g
ass of mixture, mmix
>0&.> g
2%1.% g
ass of ice, m i
2$.1 g
10.& g
Initial temperature of ice, t oc
0 #"
0 #"
Initial temperature of calorimeter, t oc
2$ #"
2>.& #"
Initial temperature of water, t ow
+2.& #"
+@.? #"
4inal temperature of mixture, t mix
>@ #"
+$.% #"
-xperimental 8atent heat of fusion, 8 f
@2.0%@? calg
@>.?1@& calg
ctual 8atent heat of fusion, 8 f
@0 calg
@0 calg
ercentage of error
2.??$0 '
+.21>0 '
Trial 2. =rass etal +%.? g
DATA and OBSERVATO!S
Part 1: Determining the Specific Heat of Metals
2ppro0e" <%6
Instructor
Date
