Julia,+Hannah,+and+Marissa's+Calorimetry+Lab

=Calorimetry Lab Report=  October 12th, 2009


 * Participants**: Julia Kravitz, Hannah Mollmark, and Marissa Marton
 * Purpose **: To identify an unknown metal by its specific heat and to measure the latent heat of fusion for the substance paraffin.

** Brief Description of Experiment **: In the Calorimetry lab, Hannah, Julia, and I planned a procedure in order to collect sufficient data. We utilized the calorimeter system which mainly consists of an inner and outer vessel as well as a lid and a small hole for a thermometer to fit into. The vessel within a vessel, along with the lid serves the purpose to conserve the heat inside and thus reduces the chances for it to escape. We used this system to determine the change in the water’s temperature when a cylinder of metal that had been sitting in boiling water was placed into the inner vessel(containing the about room temperature water). We were able to record all of these changes on Logger Pro and we tested this system multiple times to collect more accurate data. Next, we also measured the change in the water’s temperature when we placed a hot tube of paraffin inside. All of the observations and data we collected, helped us to come to conclusions about this procedure and our final calculations. Below is a picture of what the calorimeter looks like. It is comprised of the inner vessel, the outer vessel, and the lid that was expressed above.
 * Data**:

__A graph of the metal in water__:

__A graph of paraffin__:

Q//lost// = Q//gained// || (Specific Heat)// || The heat (Q) added, in joules, was calculated by mulitplying the mass (m), in grams, of the water (or metal or paraffin), the specific heat (c) of the water (or metal or paraffin), and the change in temperature ( ∆ T) of the water. Q//added// = m x c x ∆T || (Latent Heat)// || The heat (Q) added, in joules, was calculated by mulitplying the mass (m), in grams, of the water (or metal or paraffin) by the latent heat (L). Q//added// = m x L ||
 * Sample Calculations:**
 * //Heat Lost Calculation// || The heat (Q) lost in joules was calculated by measuring the heat gained. This was determined by measuring the heat before and after the metal or paraffin was added.
 * //Heat Added Calculation
 * //Heat Added Calculation
 * These equations can be rearranged to determine parts that are unknown. For example, the heat added (specfic heat) equation can be rearranged to determine the specfic heat: c = Q//added// / (m x ∆T)

The purpose of this lab was to identify an unknown metal by its specific heat and to measure the latent heat for paraffin. By using known measurements, we calculated the specific heat of the metal to be 0.3714. We searched for a metal with this specific heat and there were two with similar specific heats: copper with a specific heat of 0.385 and zinc with a specific heat of 0.387J/gC. Our educated guess is that the metal was zinc because of the color of the cylinder, but we are not positive. We calculated the latent heat of paraffin by using known measurements and came up with a latent heat of 27.26J/g. After comparing this number with other groups, it seems very low, so there may have been errors in our calculations.
 * Results**:

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.
 * Lab Questions**:

We attempted to make the result as accurate as possible by keeping the thermometer in the water for a long period of time to allow the temperature to change completely. In doing so, we waited until the temperature ceased to rise or fall. In most cases, the recorded temperature would simply fluctuate between two relative temperatures. We would wait to see if the temperature would go up more and when it didn't, we knew that would be the end point of data collection for a given trial. We also closed the calorimeter as soon as possible after placing the hot metal into the inner vessel in order to prevent any heat from escaping into the outside enviornment.

2. In what ways did the calorimeter fail as a closed system? What mathematical effect on your result would these failures have?

When measuring the change in temperature for the paraffin, the calorimeter failed as a closed system because the tube the paraffin was in was too big so the top to the calorimeter could not close completely. This affected the mathematical results in that some of the heat was lost into the surrounding air in the midst of the procedure. These failures would affect the result in that some heat would be lost instead of it all transferring from the tube of paraffin to the water.

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 metal used in this experiment to a very high temperature (500 degrees C) and dropping it into a calorimeter with water initially at 95 degrees 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 degrees C.

In dropping the 500 degree C metal bar into 95 degree C water, the temperature of the water would increase because heat transfers from an object of higher temperature (metal bar) to an object of lower temperature (water). When the water hits a certain temperature, its latent heat, it will change state from a liquid to a gas. Measurements that will need to be taken: mass of the metal bar, initial mass of the water (my measuring the calorimeter with and without water), and temperature of the water throughout the procedure.

With the given circumstances, the recorded temperatures were somewhat reproducable however there were a lot of factors that affected the results. The fact that there was only one boiling pot of water with multiple weights inside was a bit of a problem. Each team places their weight into the room temperature water and waits until the cylinder basically cools. They then would place that cylinder into the boiling water. This can result in conflict because another team may come along and take that same bloke they put back potentially less than a minute before. As a result, the temperatures recorded were slightly different and in addition to this, the amount of water weighed prior to conduction the experiment was slightly different each time. Also, as stated above, the amount of heat escaped from the time that we had to place the hot cylinder into the inner vessel, carry it back to the table (quickly), and place the lid on, heat will be lost. A way to make the results more accurate would have been to let each group have their own group of cylinders in boiling water. This way, the group could know which had been used recently. Also, if the group had their own boiling water and cylinders, it would allow for placing the metal in quickly and immediately placing the cap on top. This would greatly minimize the amount of heat potentially lost. In addition to these things, measuring out the same mass for the water may have given very close results. Overall, there were apparent issues with the lab that caused the results to be inconsistent.
 * Conclusion**: