Lab Report: Measuring Specific Het of Mozzarella Cheese
In this Lab, the specific heat of mozzarella cheese was measured to be 2.46 (J/g °C) as a function of its temperature. The experiment was performed at 60 Celcius degree, and the specific heat was determined at the various temperatures. The measure was repeated fourth times in order to obtain the statistical error associated and the error was found as +/- 1.50
Introduction
The Specific heat is defined as the amount of energy required to raise in calories to produce a temperature change of 1C per gram of substance (J/g °C). Calorimetry is the measurement of heat energy changes. Calorimeter will be used to determine the specific heat of mozzarella cheese. This experiment will be done by using an aluminum cup calorimeter containing hot water at 60 Celcius degrees.
Based on the First Law of thermodynamic, when a heated piece of substance is placed into the calorimeter, all of the energy should be accounted for. Therefore, energy cannot be created or destroyed, energy of the system and surrounding is constant, and any energy transferred from the system must be transferred to the surrounding. The relationship between the thermal energy and specific heat capacity is
(1)
qcheese = - qcalorimeter = -(qH2O + qAl)
mcheesesCchesse ΔTcheese = -(mwaterCwaterΔTwater + mAlCAlΔTAl) (3)
where ΔTcheese = Tf – Ti (cheese) (4)
ΔTwater = ΔTAl = Tf – Ti (calorimeter)
The statistical error in the heat capacity ratios was found using the student’s T test with 95% at degrees of freedom equal 3 and the value of t is 3.18 And the interval for 95% CL was defined as
(5)
Experimental
800 ml of water in a glass beaker (1L) was heated on the hot bath to 60 Ceicus degree specified. The calorimeter was prepared during waiting, the calorimeter consist of an aluminum cup was placed into a larger outer container supported by insulating ring. A cover with a hole and stopper to accommodate a thermometer was fitted onto the top of the outer container. The masses of the empty aluminum cup and the mozzarella cheese were determined for each run.
The hot water (approximate to 60 Ceicus degree) was poured into the calorimeter cup and replaced by the cover. The initial temperature of the calorimeter was recorded after few seconds. The mozzarella cheese was placed into the cup and recorded the temperature of the mixture every 30 second for the next 5 minutes. Then the total mass of the cup, cheese and water were obtained, and the mass of water was equal to the total mass minus the masses of the cup and the cheese. The experiment was repeated for fourth time. The Aluminum cup was clean up by the hot water.
Result and Discussion
First, the temperature of mozzarella cheese was collected every 30 second in 5 minutes (Table 1, 2, 3 and 4). The final temperature systems of each run after plotted were 45.4 C (Figure1), 49.20 C (Figure 2), 51.20 C (Figure 3) and 51.30 C (Figure 4).
Figure 1: 1st graph
In table 5, the specific heat of mozzarella cheese was then calculated using equation 3 and 4 for all fourth trials of reach cheese run. The statistical error in the heat capacity ratios was found using equation 5 of the student’s T test with 95%, and the confidence interval found as 0.96 and 3.96. The standard deviation was determined as 0.991. The average heat capacity ratio an average statistical error is 2.46 ± 1.50 (J/g °C)
As seen in table 6, the specific heat of mozzarella cheese and its error was hard to define. The scale did not go smoothly in trending line. Even comparing with the same staring temperature at 60 Ceicus degree, the result was not too close. The specific heat of the Mozzarella cheese from the experimental analysis decreases with an increase in temperature. This is also because of the relationship between specific heat and temperature expressed in the equation below
Q=cm∆T.
Where, Q=heat added, c=the specific heat, m=mass, ∆T= the change in temperature
Comparatively, the results from the groups shows a consistency in the aforementioned principle. The results are not similar but they analytically conform to Duolong and Petit theories as will be outlined in this section. However, this relationship does not usually apply when there is a change of phase. This is because the heat added or ejected during the change in phase does not affect the change in temperature. The law of Duolong and Petit also explain that the molar specific heats of most solids are nearly constant at room temperatures and above limit (Bimalendu, 564). At lower temperatures, the specific heat also drops as the quantum process energy also increases. This analysis is also clearly proved by the Einstein-Debye model while introducing the quantum behavior which clearly showed that the specific heat is temperature dependent at low temperatures and also that the specific heat has a high temperature limit (Bimalendu, 564).
Sources of error
The sources of error in the example included:
Loss of heat while recording the and some mass of water with the escaping vapor
Human parallax error while taking measurements.
Inaccuracy in taking the measurements of the mass of the inner aluminum wall due to the water adhered to the walls.
Conclusion
References
Chemprime. The Thermodynamics of Pizza. 2010. Accessed on 9th February 2016 from: http://wiki.chemprime.chemeddl.org/index.php/The_Thermodynamics_of_Pizza
Roy, Bimalendu N. Fundamentals of Classical and Statistical Thermodynamics. Chichester [u.a.: Wiley, 2002. Print.
