Lab+Report+V

=°Lab Report Title= Oct 14, 2009


 * Participants**: Wangene Hall and Niko Pearson
 * Purpose**: The purpose of this lab is to measure the temperature changes of an unknown metal and liquid paraffin using a water-filled calorimeter.


 * Brief Description of Experiment**: This experiment was designed to collect data concerning the specific heat capacity (c) of an unknown metal, as well as the latent heat of fusion of liquid paraffin. The equations for calculating the heat of a substance are given, requiring that an object's mass, specific heat and change in temperature are known. An aluminum calorimeter, made of metal surrounding an insulating material, was weighed to determine its mass, as well as the mass of the water within it. The temperature of the water was taken, once the calorimeter and water had reached equilibrium. For the first part of the experiment, the mass and change in temperature for the unknown metal rod was calculated. The specific heat of the metal rod was extrapolated by equating the heat content gained of the water with the heat lost by the metal. The latent heat of paraffin was calculated by equating the total heat gained by each part of the calorimeter system and its contents with the total heat lost.

__Temperature change due to the addition of the hot cylinder to the water:__ Latent heat (L) Q/m (**Q**//water// + **Q**//container//) - (**Q**//test tube// + **Q**//liquid paraffin// + **Q**//solid paraffin//) || __Finding the Specific Heat of the Mystery Metal:__ Mass of Water- 73.68g Specific Heat Capacity of Water- 4.186J/g°c Initial Temperature of Water- 22.1°c Peak Temperature of Water- 26.5°c Final Temperature of Water- 26.4°c Change in Water Temperature- 4.3°c
 * Data**: Create a table (when appropriate) including all data collected or calculated during the lab. Be sure to include a heading for each column that includes the units of each measurement.
 * Data Collection:**
 * Heat (Q)
 * Q**//cylinder//
 * Q**//phase change// || mass x specific heat capacity x change in temperature
 * Q**//water// + **Q**//container//
 * Data Collection:**

Mass of Container- 42.68g Specific Heat Capacity of Aluminum- 0.9J/g°c Initial Temperature of Container- 22.1°c Final Temperature of Container- 26.4°c Change in Container Temperature- 4.3°c

Mass of Cylinder- 111.99g Specific Heat Capacity of Cylinder- ? Initial Temperature of Cylinder- 100°c Final Temperature of Cylinder- 26.4°c Change in Cylinder Temperature- 73.6°c

//**Q**lost by cylinder// = (1326.23J + 165.17J) = 1491.4J
 * Q**//gained by water//- 73.68g x 4.186J/g°c x 4.3 = 1326.23J **Q**//gained// by cup- 42.68g x 0.9J/g°c x 4.3 = 165.17J

Specific Heat of Cylinder: 1491.4J = 111.99g x c x 73.6°c 111.99g x 73.6°c = 8242.46 c = 1491.4J / 8242.46 = __**//0.181J/g°c//**

Finding the Latent Heat of Fusion of Paraffin:__ Mass of Paraffin- 4.5g Specific Heat Capacity of Solid Paraffin- 0.7J/g°c Specific Heat Capacity of Liquid Paraffin- 0.00213 Initial Temperature of Paraffin- 100°c Final Temperature of Paraffin- 24.1°c Change in Paraffin Temperature- 75.9°c

Mass of Test Tube- 11.08g Specific Heat Capacity of Glass- 0.2J/g°c Initial Temperature of Test Tube- 100°c Final Temperature of Test Tube- 24.1°c Change in Test Tube Temperature- 75.9°c

Mass of Water- 110.67 Initial Temperature of Water- 22.8°c Final Temperature of Water- 24.1°c Change in Water Temperature- 1.3°c

Mass of Container- 42.68g Specific Heat of Aluminum- 0.9J/g°c Initial Temperature of Container- 22.8°c Final Temperature of Container- 24.1°c Change in Container Temperature- 1.3°c


 * Q**//solid paraffin-// 4.5g x 0.7J/g°c x 25.9°c = 81.585J
 * Q**//liquid paraffin-// 4.5g x 0.00213J/g°c x 50°c = 0.47925J
 * Q**//test tube-// 11.08g x 0.2J/g°c x 75.9°c = 168.19J
 * Q**//water-// 110.67g x 4.186J/g°c x 1.3°c = 602.24J
 * Q**//container-// 42.68g x 0.9J/g°c x 1.3°c = 43.94J
 * Q**//phase change-// ?

Heat of Phase Change and Latent Heat: (602.24J + 43.94J) - (168.19J + 0.47925J + 81.585J) 646.18J - 250.25J = 395.93J = **Q**//phase change//
 * L**//paraffin =// Q/m = 395.93J / 4.5 = **//__87.98J__//**


 * Results**: The major result of this experiment was discovering the factors involved in calculating specific and latent heat. Although the values we calculated we not conclusively accurate, we learned the techniques involved in using calorimetry to calculate physical properties.

1. In what ways did you attempt to make your result as accurate as possible? Describe how each way contributed to a more accurate result. We attempted to make our results as accurate as possible by measuring the masses and temperatures accurately. This contributed to a more accurate result in that our calculations were more accurate. We also tried to work quickly and precisely, to mitigate the effects of heat loss and energy transfer into other forms. There were not a large number of ways to increase the accuracy of our experiment because we did not follow a definitive procedure.
 * Lab Questions**:

2. In what ways does the calorimeter fail as a closed system? What mathematical effect on your result would these failures have? The calorimeter fails as a closed system because mass and energy can leave the system. During the calculations of heat for the metal rod, energy dissipated from the calorimeter because the insulating material absorbed the heat. In addition to this, during the data collection for the latent heat of paraffin, the container had to remain open, because the glass rod could not fit in the calorimeter. This lead to the dissipation of heat energy into the atmosphere, resulting in a high degree of inaccuracy. The mathematical effect of these failures on the system was apparent in the calculation of heat gained by the water and calorimeter. The amount of heat lost due to the system's failure as a closed system would have to be added to the equation for the total heat gained by the water and the heat lost by the metal/paraffin.

3. Suppose you were asked to measure the latent heat of vaporization of water (the amount of heat required to turn liquid water into a gas). You propose to do this by heating a bar of the metal used in this experiment to a very high temperature (500 C) and dropping it into a calorimeter with water initially at 95 C. Describe what you think will happen and what measurements you would need to make in order to calculate the latent heat. Approximate how much water would be turned to steam if the bar had a mass of 0.7 kg and the final temperature of the 0.35 kg of water in the calorimeter was 100 C.

The water in the calorimeter will evaporate, nullifying the accuracy of heat gained by water in the equation. The evaporation of the water would introduce too many variables into the system. The phase changes of paraffin might never occur to such a result that they could be measured and placed into an equation. The measurements needed to be taken to calculate the latent heat of paraffin would be: the specific heats of all objects in the system, the temperature changes of each object and the respective masses.

The question is stated somewhat unclearly-- but would nonetheless not accurately be answerable. Assuming the system is perfect for the sake of this calculation, and that the starting mass of the water was also 0.7 kg, the water lost 0.35 kg to the change in temperature. If more information were given, this problem would be more easily solved, but unfortunately, it is rather difficult to understand.


 * Conclusion**:
 * This experiment did not produce a valid and reproducible result. Our metal was not determinedly a single substance, but was probably a combination of different metals. The specific heat we calculated was closest to tungsten. Lead, gold, and platinum are highly unlikely candidates for the unknown metal. Our sources of error were numerous, and our techniques/procedures somewhat dubious, as we did not know beforehand how to design the experiment.
 * The accepted value/expected result did not exist in the conventioal sense, because the unknown metal rod did not have a comparitive standard, neither did the paraffin data have a firmly established procedure and result.
 * This experiment could be improved by re-performing it according to an established procedure. If the metal was known, its specific heat could be determined with certainty. Also, the temperature of the room could be established to ensure that the calorimeter is not losing excess heat. In addition to this, a different type of calorimeter might more accurately contain heat, especially if the thermometer was integrated into it. Measurement inaccuracies were the result of having to equate heat lost to heat gained without being able to mathematically consider non-conservative forces. This is an example of simplified assumption that was necessary for our data collection. Likewise, using one data trial as the definitive specific heat calculated caused error which could be remedied by multiple trials.

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