drew+kyle+taylor+calorimetry+lab

=Calorimetry Lab=


 * Participants**: Drew Twitchell, Kyle Davis and Taylor Brown


 * Purpose**: To identify an unknown metal by its specific heat and to measure the latent heat of fusion of paraffin.


 * Brief Description of Calorimeter**: The calorimeter was comprised of two aluminum containers placed one inside the other. The external container was larger than the internal vessel. The smaller container was seated on a removable black plastic ring which extended the lip of the internal container so it stayed flush to the metal suspension ring, which was down on the inner sides of the larger vessel's opening. This removable piece of plastic extended the surface area of the lip of the smaller internal vessel acting as a gasket so the internal vessel had trapped air surrounding it evenly on all sides. The trapped air between the two containers insulated the internal cup and no air was able to be exchanged with the atmosphere in the room. Over the entire set up was a black plastic cover[lid]. The lid had two strategically placed holes. The larger hole accommodated the thermometer and its rubber stopper which sealed the opening and also allowed the thermometer to remain suspended slightly off the bottom of the vessel. The other tiny hole housed the metal stirring rod, which fit the rod exactly, so no rubber support was needed.
 * *note this does not include the wire from the thermometer leading to the computer, nor does it include the stopper to make the thermometer's access hole air tight. **

**
 * Brief Description of Experiment:** ** Initially, we discussed what steps would be necessary to carry out the experiment. After defining the procedures we identified the mass of the entire calorimeter by placing all of the parts of the system [external container with suspension lip, internal vessel, stirring rod, separator ring, lid and the rubber stopper] by weighing them on the electronic scale and recorded the weight in grams. The thermometer was not weighed because it is suspended by the stopper so it adds no weight to the system. Next we measured the empty internal vessel without the stirring rod and recorded its mass in grams. Then we filled the internal vessel with a random amount of tap water and allowed it to equilibrate to room temperature before taking the temperature of the liquid with a LoggerPro thermometer that was attached to the computer. The temperature was recorded in degrees celsius. Next we measured the mass of the internal vessel and the water together, recording the weight in grams. We found out the mass of the random quantity of water in the smaller vessel by then subtracting the weight of the empty internal container from the total weight of the combined items and recorded the difference in grams. Then, we took the metal cylinder that was in boiling water (100 degrees celsius) and placed it in the internal vessel with the stirring rod and thermometer. Once the heated metal cylinder was transferred to the internal vessel we closed the lid very quickly so no energy escaped. With the metal cylinder now in the vessel we had set LoggerPro to take measurements of the time in seconds vs. temperature in degrees celsius every five seconds. We observed the change in temperature to the water with a radical jump in the graph, we analyzed the data until the temperature had fallen to approximately room temperature again. After recording the temperature differences over 60 seconds we set up calculations to measure the number of joules( amount of heat) the water was gaining. Once, we had the amount of heat or joules the water was gaining, we knew that, that was the same amount of heat the cylinder was giving off. We could now find the specific heat constant for the metal cylinder; we used a calculation to find this . Now that we had the specific heat constant of the cylinder we needed to calibrate the thermometer to make sure it was making accurate measurements. We placed the thermometer directly into two solutions that we knew should be certain temperatures; boiling water and ice. After we found that our thermometer was almost exactly correct, only 0.3 degrees off when placed in ice bath and 1.3 degrees off when placed in boiling water. We now knew that each temperature measurement we had made, had to be adjusted by .375 degrees. After calibrating the thermometer we found another source of error which was the heat given off by the cylinder wasn't only given to the water but the aluminum vessel the water was in. We measured the mass of the empty internal vessel and the stirring rod. Once that was found we looked in a book to find the specific constant of aluminum. Then we had to use the same temperature difference as the water from initial (almost room temperature) to final (room temperature). Once we had solved for the amount of heat the aluminum gained, we added it to the amount the water gained and came up with a total amount of heat given off by the metal cylinder. Due to the specific heat constant of the metal being .3765 we were inclined to believe that the metal was brass. Next was to reproduce half the experiment. This time we were trying to solve for the heat of fusion or latent heat of paraffin wax. We again measured the empty internal vessel [by itself] to find the mass in grams. Once found we filled the vessel with water and measured the mass of the combined items. Once we found the weight of the empty vessel, we subtracted the empty vessel from the combined amount to calculate the mass of the water. Next, we recorded the initial temperature of the water in the internal vessel and made sure to add the .375 degrees to the temperature because of the calibration we did. Next, we began to record the data on LoggerPro for 5 second intervals again, and then we took the paraffin wax in an enclosed test tube which was in boiling water and placed it in the calorimeter. We began to observe the changes of the graph and continued to observe until we came to agree that the paraffin had reached room temperature and had solidified. Again, we examined the data to try and figure out how much heat the paraffin was giving off and when it solidified. We found the mass of the paraffin we used by measuring an empty test tube and subtracting it from the mass of both the paraffin and the test tube. Once we had found the mass we found the amount of heat the liquid paraffin had given off and how much the solid paraffin had given off. We again knew that the water was gaining heat and the aluminum vessel was as well, so we had to find the amount of heat it gained and then add that to how much the water gained to find the total amount of heat gained. Now, with that data we could find the heat of fusion for paraffin. The two amounts of heat given off (both liquid paraffin and solid paraffin) were added together, then subtracted from the total amount of heat the aluminum vessel and the water gained. Once that number was found it was divided by the mass of the paraffin. That is how the latent or heat of fusion was found. **
 * Data****:
 * note that the red line is the water from experiment one and the blue is the paraffin from experiment two
 * **Lab Data** ||
 * || **Object Weights (g)** || **Initial Temperature (degree C)** || **Final Temperature (degree C)** || **Change in Temperature (degree C) ** ||
 * Internal vessel with water || **261.26** || **22.475** || **26.375** || **3.9** ||
 * Calorimeter || **232.86** || **XX** || **XX** || **XX** ||
 * Internal vessel || **42.68** || **XX** || **XX** || **XX** ||
 * Water || **168.67** || **22.475** || **26.375** || **3.9** ||
 * Metal Cylinder || **112.7** || **100** || **26.375** || **73.625** ||
 * Internal vessel+stirring rod || **49.5** || **XX** || **XX** || **XX** ||
 * Paraffin Wax Liquid || **4.42** || **100** || **50.375** || **49.625** ||
 * Paraffin Wax Solid || **4.42** || **50** || **25.075** || **24.625** ||
 * Water (paraffin) || **251.91** || **22.4** || **25.075** || **2.675** ||
 * Test tube || **11.08** || **XX** || **XX** || **XX** ||
 * Test tube + Paraffin || **15.50** || **XX** || **XX** || **XX** ||
 * Test tube + Paraffin || **15.50** || **XX** || **XX** || **XX** ||

m= mass; c= constant; delta T= change in temperature; L= latent heat or heat of fusion
 * Sample Calculations:**

Heat added= m*L Heat lost = heat gained Heat added = m*c*delta T Change in temperature = final temperature - initial temperature


 * Calculations:**
 * 1. Finding the specific heat constant for the metal:**

water= (191.41)(4.186)(3.9)= **3124.84J** metal= **3124.84J**=(112.7)(c)(73.625)= **.3765J/g****oC **


 * allowance for //the aluminum vessel taking some of the heat from the cylinder//

aluminum= (49.95)(.9)(3.9)= **175.32J+****3124.84J=3300.16J**
 * 3300.16**=(112.7)(c)(73.625)=**.3977J/g** oC = **specific heat constant of metal cylinder =** brass


 * 2. Finding the latent heat or heat of fusion of paraffin**:
 * Paraffin changes from liquid to solid around 50****oC

water = (251.91)(4.186)(2.675)= 2820.77J aluminum = (49.95)(.9)(2.675) = 120.25J 2820.77J+120.25J= 2941.02J

liquid paraffin= (4.42)(2.13)(49.625)= 467.19J solid paraffin= (4.42)(.7)(24.925)= 77.11J ** **467.19J+77.11J= 544.3J heat of fusion= 2941.02J-544.3J= 2396.22J/4.42= 542.24J/g=** Latent heat


 * Results**:The results of our lab showed that the specific heat for the unknown metal was .3765J/goC. After looking up many different specific heats for metals on many different sites and in books, we identified the metal as brass. However, we do not think that the metal is brass, as the color of the cylinder would leave us to believe the metal is some other compound[perhaps zinc]. We think that there is some sort of human error involved that found the specific to be .3765J/goC which is brass. A lso in this lab were able to come to an answer for the latent heat or heat of fusion for paraffin as 542.24J/g.
 * Lab Questions**:
 * In what ways did you attempt to make your results as accurate as possible? Describe how each way contributed to a more accurate result.

To make our results as accurate as possible we calibrated our thermometer, we used boiling water and ice water as the two reference points for the calibration. In doing this calibration we found that our thermometer was .3 degrees celsius off when placed in ice and 1.3 degrees celsius off when placed in boiling water. Once we discovered the amount off each known temperature, we figured that any temperature we had, we had to add .375 degrees celsius to account for this difference. This addition of .375 made our results very accurate. Another way we tried to make the results accurate was when the paraffin was added the test tube was too big to fit in the inside of the calorimeter so there was a hole that let air escape. We tried our best to cover this hole with our hands and account for this in our results. In covering the hole with our hands we made our results more accurate because we tried no to let any air from the calorimeter to escape into the atmosphere. In what ways does the calorimeter fail as a closed system? What mathematical effect on your results would these failures have?

The calorimeter fails to be a closed system because again when the paraffin was added the test tube was too big which allowed air to escape. Another reason why the calorimeter is not a closed system is because even though it was sealed with a plastic lid, some of the heat added escaped into the atmosphere through little gaps in the system. Another location where heat gained escaped is into the internal cup and stirring rod of the calorimeter. To calculate these failures mathematically we would have to figure out how much escaped from the system through the gaps and through the stirring rod and internal cup, if we didn't then the heat constant for the metal cylinder would't be accurate. Another location where heat was lost was in the carrying of the metal and/or paraffin to the calorimeter from the boiling water.

Suppose you were asked to measure the latent heat of vaporization of water (the amount of heat required to turn liquid water into gas). You propose to do this by heating a bar of the metal used in this experiment to a very high temperature (500 degrees celsius) and dropping it into a calorimeter with water initially at 95 degrees celsius. 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 0.7kg and the final temperature of the 0.35kg of water in the calorimeter was 100 degrees celsius.

Dropping a extremely heated bar of metal into the calorimeter, would make the water begin to steam and some of the water would be lost due to evaporation and condensation. Then we would have to measure the increase in water temperature in the calorimeter and see how much the hot metal affected the amount of steam that was produced. **

As this experiment was carried out in an open air system, it most likely can not be considered valid. The number of errors applied to the experiment, through inexperienced handlers and inadequately utilized equipment, increased the chances of the results not accommodating the necessary parameters to make the results reproducible. Loss of energy, through the lack of a timely transfer of the heated cylinder to the inner vessel may have initiated the first of many unacceptable parameters for error. The experiment seemed straight forward enough but, as the results showed, human error plays a large part in the problems associated with reproducible results. Time is a factor that inexperienced experimenters forget to account for. The accepted results indicate that especially when looking at the specific heat constant for the metal, human error makes the specific heat a number that the metal we used shouldn't be. For the improvement of this I believe if you gave us the specific heat constant for the metal then human error couldn't make our results differ from what they should be. Our group got a specific heat for the metal we used, however, we believe that due to human error it is not correct. Another suggestion would be when adding the paraffin to the calorimeter have a smaller test tube that fits inside, because the test tube was too big and so the system wasn't closed anymore letting the hot air escape into the atmosphere.
 * Conclusion**:
 * A statement about whether you think that the experiment produced a valid and reproducible result and reasoning supporting your statement.
 * A suggestion as to why your experimental results differ from any accepted value or your expected result (if appropriate).
 * A suggestion for a simple improvement to the experiment. Think about what caused problems, measurement inaccuracies, or inappropriate simplifying assumptions and propose a change. A sketch may be helpful.