Calorimetry+Lab


 * __CALORIMETRY LAB__**


 * __Participants:__** Jill McKenney and Rachelle Chiasson
 * __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 calorimeters consists of two cups (one smaller cup inside of the larger cup). The smaller cup's rim was lined with a black plastic ring that was removable. A black plastic lid covered the top of the larger cup. There were two holes in the plastic lid; one for the thermometer and one for the metal stirrer. First we brainstormed ideas of how we were going to go about this lab procedure. First, we measured the mass of the calorimeter, the stirring rod, and the little cup all separately. We then added room temperature water to the little cup of the calorimeter. We then measure the mass of the small cup with water to determine the amount of water in the small cup. Then we took the initial temperature of the water in the small cup using our thermometer and LoggerPro. After finding the temperature of water at room temperature, we took the metal (which was in 100 degree Celsius water), to the small cup. We placed the metal in the small cup on top of the metal stirring rod and sealed the calorimeter closed with the black plastic cover. We began to collect the data in five second intervals on LoggerPro. Once the data was stagnant we stopped the collection of data and recorded the final temperature of the water. We then removed the metal piece, measured its mass, and returned it to the boiling water. At this point we had all the data that we needed to determine the heat capacity of the metal. Then we had to calibrate our thermometer. We did this by measuring boiling water, which we pressumed would be 100 degrees Celsius; but in fact it was about 98.7 degrees Celsius. We also took the temperature of ice water, which we pressumed would be 0 degrees Celsius; but it was in fact about -.4 degrees celsius. From this information we could see that the thermometer was off by about 2 degrees Celsius. We repeated this procedure when we replaced the metal with liquid paraffin.
 * __Brief Description of Experiment__**:


 * __Data:__**

m=mass; c=constant; delta T= change in temperature; L=Latent Heat
 * __Sample Calculations__**:

Change in Temperature = Final Temp - Initial Temp Heat Added = m*c*delta T Heat Lost = Heat gained Heat Added = m * L

__**Calculations:**__
 * Finding the constant for the metal:**
 * Heat of water+ heat of calorimeter (filled with water) + heat of stirring rod = heat of metal
 * (198.27)*(4.186)*(3.5) + (445.77)*(0.9)*(3.5) + (7.27)*(0.9)*(3.5) = (114.99)*(specific heat)*(74.4)
 * 4331.93 = (114.99)*(specific heat)*(75.4)
 * Specific heat = **0.49 J/g °C** for metal
 * Finding the latent heat of fusion for paraffin:**
 * *Note: paraffin changes from liquid to solid at 50°C
 * Heat of cooling liquid + Heat of cooling solid + solidifying (latent heat) = heat of water + heat of container
 * (5.09)*(2.13)*(50) + (5.09)*(0.7)*(23.9) + (latent heat) = (211.85)*(4.186)*(1.5) + (50)*(0.9)*(1.5)
 * 616.39 + latent heat = 1397.64
 * 781.25/ 5.09 (weight of paraffin) = **153.48 J/g**

The results of our lab showed that the specific heat for the unknown metal was 0.49 J/g °C. After looking up different specific heats for metals we identified the metal as carbon steel. We also were able to conclude that the latent heat of fusion for paraffin was 153.48 J/g.
 * __Results:__**

__**Lab Questions:**__
 * 1.) In what ways did you attempt to make your results as accurate as possible? Describe how each way contributed to a more accurate result**.

- In order to make our results as accurate as possible we calibrated our thermometer using both the boiling and ice water. From doing this we discovered that the thermometer was about 2 degrees Celsius off when dealing with 100 degrees Celsius. In the experiment we were working with numbers around 25 degrees Celsius, which is one-fourth of 100. So from this we knew we had to add on .5 degrees Celsius to each temperature we recorded because one-fourth of two is 0.5. This gave us more accurate temperatures. We also accounted for where heat would be escaping from in our experiment. We concluded that it not only escaped to the water, but also the calorimeter and the stirring rod. We added these into our final equation to get a more accurate number for the heat constant of the metal.


 * 2.) In what ways does the calorimeter fail as a closed system? What mathematical effect on your results would these failures have?**

-The calorimeter failed as a closed system because even though it was sealed with a plastic lid, some of the heat was able to escape the calorimeter. Some went to the actual calorimeter cups as well as the stirring rod. We would have to calculate how much escaped through the cups and rod, otherwise the heat constant for the metal (which we calculated) would be inaccurate. Also heat was lost as we took the metal (or paraffin) from the boiling water and walked it over to our calorimeter.

By dropping a heated bar of metal into the calorimeter, the water would begin to steam and some of the water would be lost due to evaporation. We then would have to measure the increase in water temperature, and also the increase in temperature of the calorimeter.
 * 3.) 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.**

__**Conclusion:**__ The purpose of this lab was to identify an unknown metal by finding its specific heat and also to measure the latent heat of fusion of paraffin. We were able to identify the metal as carbon steel and found that the latent heat of fusion of paraffin was 153.48 J/g. We are not positive if our identification and our numerical value of latent heat is correct because our data may not be completely accurate even though we tried to make it as accurate as possible. (We calibrated our thermometer as well as took into account that some heat escaped to the stirring rod and the cup of the calorimeter). One source of error could have been when we were bringing our piece of metal or tube of paraffin to the calorimeter because we were all the way across the room causing its temperature to drop a lot by the time it reached the calorimeter. To improve this error next time we could be closer to the materials needed so heat wouldn't escape into the air.