Inmany occasions, energy is normally released in the form of chemicalreactions such as electricity, sound, and light energy (Gordon,1980). However, the most common form of energy is heat. When theenergy is in the form of heat, it is easier to measure as compared toother forms. The method that is used to measure the specific heatcapacity of metals and latent heat of a melting ice is referred to ascalorimetry experiment. The equipment used in the experiment is knownas calorimeter. The outer part of the calorimeter is typically madeup of a copper cup, while the inner part is made up polystyrene cup.
Normally,the starting temperature of the experiment is measured before wateris heated up using a burning fuel. After heating, the finaltemperature of the apparatus is recorded. Under normal circumstances,the mass of the spirit burner or the equipment that is used forburning is measured before the start of the experiment and after theexperiment. The process is carried out to measure the amount of fuelthat was used during the calorimetry experiment.
Inthe calorimetry experiment, there are some sources of errors. Suchsources of errors can be classified as systematic or random errors.Some of the errors are as a result of the condition at which theexperiment is carried out.
Themain objective of the experiment was to determine the specific heatcapacity of the metal (brass) and the latent heat of a melting iceusing the calorimetry.
Descriptionof the Equipment
Theequipment used during the experiment was a calorimeter. The innerpart of the calorimeter is made up of a nickel-plated copper cupwhile the outer part is made up of polystyrene container. Some of theother apparatus that were used include string, brass weight, a gasburner, a thermometer, and a stopwatch.
Heatcan be defined as the flow of energy due to temperature difference orthe transfer of energy from a region of high temperature to a regionof low temperature. Whenever a given amount of energy is transferredinto the object, it normally contributes to the change of theinternal energy of the system. The internal energy is labeled as.Some of the energy that is transformed into thermal energy causes achange in the kinetic energy of the molecules and at the same timethe change in temperature of the molecules, ΔT. The fraction of thetransferred thermal energy varies according to the nature of thematerial.
Specificheat capacity, Q, is defined as the amount of the energy that isrequired to raise the temperature of a 1kg mass of a substance by1Kelvin (Zhu, 2002). Therefore, Q can be expressed as follows:
Specificheat energy is a material-dependent property. However, under thecondition of this experiment, it will be assumed to be constant.Moreover, when calculating the ΔT, the initial state will besubtracted from the given final state. In that case, the change intemperature is expressed as follows:
Latentheat is defined as the amount of energy that is required to produce1-kilogram change in mass for a higher phase material that is inphase transition. Furthermore, the higher-phase material is amaterial that exists under high temperatures. According to themelting transition where the ice melts into water, water is normallyreferred to as the material of the higher phase. However, differentsubstances usually react differently to the energy that is removed oradded to them during the change of phase such as the melting process.It is mostly influenced by the different arrangements of the internalmolecules. In that case, Q can be expressed as follows:
Calorimetrycan be defined as a technique that is used for measuring the amountof energy that is associated with a chemical reaction or a physicalchange (White, 1928). The method can also be used in measuring thespecific heat capacity of a given substance. The process mainlyinvolves the heating of a given material and then adding a certainamount of water to the heated material. At the same time, the changein the equilibrium temperature is recorded. The process involving thechange in energy takes place in the isolated calorimeter. Therefore,energy will move from the hot substance and enters into the coldsubstance. In that case, the conversion of the energy will berequired. What follows is the expression showing the conversion ofenergy.
orthe equation can be expressed specifically as
SpecificHeat Capacity of Brass
The apparatus were examined and checked if their components were viable for the experiment.
The weight of the brass was weighed and its mass was found to be
The inner cup of the calorimeter was weighed and its mass was found to be
A thread was tied into the brass weight, and then the brass weight was left inside the boiling water to heat up.
The empty calorimeter that had lid and the thermometer was weighed. After weighing the calorimeter, it was filled with enough water to cover the brass weight. The mixture was also weighed.
Experimentalconsiderations: The temperature of the water that was being usedduring the experiment was taken to below the room temperature with afew degrees. This was to ensure that the temperature of the waterinside the calorimeter was close to the room temperature, that is,before and after the brass weight was added into the calorimeter.Furthermore, the considerations will ensure that the energy enteringor leaving the experimental set-up was easily minimized. Also, it waspractically possible to make sure there is little energy entering orleaving the polystyrene cup.
The temperature of the water inside the calorimeter was measured using a thermometer. The intial temperature was taken to be
The brass weight was left in the boiling water for a while so that its temperature can be at the same level with that of water. A second thermometer was used to measure the temperature of the boiling water. Initial temperature of the brass weight was taken to be equal to the temperature of the boiling water. The value was measured to be 95.
A string was used to remove the brass weight from the boiling water and then transferred into the calorimeter. The step was carried out quickly so that brass weight does not cool down. Care was taken so as not to carry the brass weight with too much water.
Experimentalconsiderations: it was considered how the result will be affectedsupposed the brass weight carried some hot water with it to thecalorimeter. Additionally, it was considered how the result will beaffected if some water from the calorimeter were splashed out whilethe brass was being transferred into the calorimeter.
A series of the temperature readings were taken so as to find the maximum temperature reached at the calorimeter. The temperature was labeled .
The specific heat capacity of brass can be calculated as follows:
Theheat added to the cold water and the inner copper cup is taken to be
Fromthe expression shown above,
LatentHeat of the Melting Ice
The empty calorimeter together with the thermometer and the lid were weighed. The calorimeter was then filled with about a quarter full of warm water which was at a temperature of 40-60 It was then weighed again. Mass of the empty calorimeter was found to be
Temperature of the water inside the calorimeter was measured and the initial temperature was taken to be
The ice was let to warm up in the cold water and a paper towel was used to absorb excessive water from it. The temperature of the ice was approximately taken to be 0. Another ice block was then added to the calorimeter. Readings were then taken at intervals of 30seconds until volume of the ice had fully melted. The final temperature of the water was found to be 24.
Note:During the experiment some elements of considerations were made. Theconsiderations include how the excess water on the surface of thewater will affect the results to be obtain, more so, when the iceblock was being transferred into the calorimeter.
Calorimeter was then weighed to find the mass of the added ice., final mass of water is equal to the mass of the cold water and it is given by.
Determinationof the Specific Heat Capacity of Brass
Finaltemperature was found to be =30.5
Table1: temperature measured with respect to time
Theheat added to the cold water and the inner copper cup is taken to be
Therefore,is calculated as follows:
=0.0562 X 4.18 X 103X (30.5 -22) + 0.0362 X 387 (30.5 -22)
Heattaken from the hot brass is expressed as follows:
Wheremass of the brass was measured to be 0.1004kg.
Heattaken from the hot brass is equal to the heat added to the cold water
Therefore,the specific heat capacity is calculated as follows:
-2115.8659J= 0.1 X c X (30.5 -95)
c= (-2115.8659J)/(0.1004 X (30.5 – 95)
Sincethe accepted value of the specific heat capacity of brass is 380Jkg-1,there must be a deviation from the calculated value. Therefore, thedeviation is calculated as follows:
Difference= 380 – 326.7342877
Percentagedeviation is calculated as follows:
Determinationof the Latent Heat that is associated with the Melting Ice
Massof the calorimeter is = 66.2 0.05
Massof the calorimeter + warm water = 104.3 0.05 g
Initialmass of water was taken to be equal to the mass of the warm water =38.1 0.05g
Initialtemperature of water was found to be, = 50.5 0.5
Table2: temperature readings
Fromthe table the final temperature of the water was found to be 24
Massof the calorimeter together with the cold water = 114.8g
Finalmass of the water is equal to mass of the cold water which is 48.6g
Massof the added ice was found to be equal to the change in the mass ofwater = 10.5g
Heatadded to melt the ice is expressed as follows:
Heatadded to the melting ice is calculated as follows:
Therefore,=0.0105 X 4.18 X 103X (24-0)
Heattaken from the warm water is expressed as
Fromthe expression shown above is calculated as follows:
Qwarm= 0.0391 X 4.18 X 103(24-50.5) + 0.0365 X 387 (24- 50.5)
=-4220.337 + (- 374. 32575)
Itis apparent that,
=- (-4594.66275) – 1053.36
However,the accepted value of the latent heat of a melting ice is normally3.34 X 105JKg-1.Therefore, there must be a deviation between the theoretical valueand the value obtained from the experiment. What follows is thecalculation of the deviation and the percentage deviation of thelatent heat of a melting ice.
Deviationof the latent heat = (3.372669286 X 105)– (3.34 X 105)= – 0.033 JKg-1
%deviation is given by (0.033 X 100)/3.373 = 0.978357%
Fromthe above calculations, the specific heat capacity of brass was foundto be while the accepted value is.It implies that there was a deviation of the obtained value. Thepercentage of the deviation calculated was found to be 14.0173%.Similarly, there was a deviation between the expected value of thelatent heat of a melting ice and the calculated value. The percentagedeviation was found to be 0.978357%. The main causes of thesedeviations were the sources of errors that were experienced duringthe experiment. Some of the sources of the errors that might have ledto the deviation between the expected value and the calculated valueinclude the heat that was lost to the air during the heating process.
Possibly,the condition of the experiment was also a source of error to theexperiment. The condition was mainly contributed by carbon monoxideand soot as a result of the insufficient supply of oxygen during theheating process. Another source of error was the random errors whichare mainly contributed by the precision that is inherent in theapparatus. For example, reading of the scale of a measuringinstrument, thermometer, and graduated beakers can contribute torandom errors during the experiment. This implies that differentmeasurement taken at different times using the same measuringequipment will not give the same value. It was also possible toexperience errors that were caused by systematic errors. It is mostlycontributed by the incorrect use of the equipment or when theexperiment was poorly designed.
Othersources of errors that might have been experienced during theexperiment include personal errors, instrumental errors, and errorsthat resulted from the methods that were used. Personal errors arenormally associated with ignorance and carelessness during theexperiment, and perhaps, physical limitation during the experiment.To avoid it in the new future, it is imperative to be well equippedwith the apparatus at the disposal. Instrumental errors are oftenexperienced when the instruments that are being used are veryimperfect. However, it can be easily eliminated by calibrationapproach. Moreover, some elements that lead to the deviations ofresults include the experimental considerations.
Theconsiderations include excess water that was used during the latentheat experiment and the splashing of water when the brass was beingtransferred into the calorimeter. Perhaps, they might interfere withthe resulting mass of the warm water and the cold water. Perhaps, itwas critically not possible to ensure that there was no or littleenergy leaving the polystyrene and the copper cup of the calorimeter.Besides the experimental considerations, it was difficult tomanipulate some of the variables. It was necessary for the energy topass out and inside the calorimeter.
Inconclusion, the main objective of the experiment was achieved in thatthe determination of the specific heat capacity of brass and thelatent heat of the melting ice was carried out successfully. Thelatent heat of the melting ice was found to be while the expected value is 3.34 X 105.Similarly, the value of the specific heat capacity of brass was foundto be .This result was different from the expected value of 380JThe deviations were as a result of errors and the experimentconsiderations. Perhaps, it was not difficult to abide by theconsideration of the experiment.
Despitethe sources of errors that were experienced during the experiment, itwas still possible to determine the specific heat capacity of brassmetal and the latent heat of a melting ice using the calorimetrymethod. The method is flexible in that it can be used to measure thespecific heat capacity of metals such as bronze, zinc, steel, andaluminum. However, it will be difficult to measure the specific heatcapacity of copper and polystyrene because they are one of itscomponents.
Calorimetrymethod can find its application in the comparison of the quality ofenergy of different types of fuel. Different types of fuel can beburnt during the experiment, and the mass of the burnt fuel ismeasured. Therefore, using the calorimetry formula of Q = mcΔT thebest fuel can be determined.
BrookhavenNational Laboratory. United States. Gordon, H. A., Smith, S. D., &Palmer, R. B. (1980). New ideas in calorimetry. Upton, N.Y:Brookhaven National Laboratory.
InternationalConference on Calorimetry in Particle Physics, & Zhu, R. (2002).Proceedings of the Tenth International Conference on Calorimetry inParticle Physics: Pasadena, California, USA, 25-29 March 2002. RiverEdge, N.J: World Scientific.
White,W. P. (1928). The modern calorimeter. New York: The Chemical CatalogCompany, Inc.