Letter to District Attorney

Letter to District Attorney - Bryce Krzenski Professor...

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Unformatted text preview: Bryce Krzenski Professor Lingerfelt CHM Lab 111 Dear District Attorney, My name is Bryce Krzenski, a professional consultant and I am writing to provide a technical report concerning the break in at McMichael Science Building at Elon University. I was asked to assess the crime that occurred specifically in the McMichael Wine Research Laboratory on September 1st. The lab was broken into with items becoming both damaged and stolen. Although the situation was unfortunate, trace evidence was left that had to be examined for the investigation. Campus police requested assistance to narrow down the possible subjects, which I had hoped the evidence would allow me to do. The evidence found at the scene that was pertinent to identifying a possible suspect was a plastic card jammed in the door, the metal ring that was found on the floor of the scene, an unknown white powder substance in a plastic bag and wine that appeared to have been tampered with. The last few weeks I spent running test on this evidence to provide you with conclusive results to help in the investigation. The photo to the left is of the metal ring found at the crime scene and in the background is the crime scene. During the first week in the laboratory, we worked to identify the metal ring (above) found on the floor of the crime scene and tested the wine that was suspected to be tampered with. To identify the ring, we had to identify the density of the metal by massing it and finding the volume via water displacement. Density was calculated by dividing the mass by the volume, calculated to be 15.140 g/mL. When compared to the densities of the other known metals it was closest to tungsten carbide, which has a density of 15.6 g/ml. The specific heat of the metal was calculated by boiling water and the immersing the ring in the boiling water. The initial temperature of the water was taken and was monitored in a coffee cup calorimeter (used to measure the amount of heat involved in a chemical reaction) where the final temperature was taken. The numbers from the coffee cup calorimeter were plugged into the equation: M1 c 1 ΔT 1= -­‐M2 c2 ΔT2, where M= mass, c= specific heat capacity, and T=temperature. The specific heat of the ring was found to be 0.160 J/g °C which is close to the specific heat of tungsten carbide which is 0.171 J/g °C. Since the specific heat and densities values are most similar to tungsten carbide, it can be concluded that the ring is made of tungsten carbide. The photo to the left is of bottles of wine found at the crime scene. As you can see there is severe discoloration between the two bottles o n the left and the bottle on the right, leading us to believe the wine had been tampered with. Further tests were run (explained below) to determine whether the wine was actually tampered w ith. The analysis of the tampered wine was completed by experiments similar to the metal ring, the density and specific heat capacities were found of both of the wines (tampered and untampered). The results of the two wines were compared to determine whether or not the wine collected from the crime scene had been tampered with or not. Using the same equation and procedure above with the new variables of aluminum and wine instead of metal ring and water, the specific heat of the evidence wine was 3.35 J/g °C and the specific heat of the tampered wine was 6.10 J/g °C, confirming that it had been tampered with due to the differences in heat capacity. The densities of the wines were also found to be difference with the tampered wine being .979 g/mL and the density of the evidence wine being .981 g/mL. This reaffirmed that the wine had been tampered with and was not the same as the evidence wine. To the left is the unknown plastic card found at the entryway of the stairway that lead to the crime scene. During the second week of lab the goal was to identify the unknown plastic found at the doorway. In order to identify the unknown plastic, a flame test and density test were conducted to identify characteristics to be compared to known plastics characteristics The known plastics tested were PET, PVS, ABS and PHA. The flame test was completed using a Bunsen burner to light a flame then holding the plastic over the flame, and recording observations. The observations made were of the color of the flame when burned, the pH and color of the smoke and how the plastic melted. The evidence plastic’s flame burned a blue/green flame and turned the plastic brown when it burned by twisting and charring. The smoke test showed that the flame from the plastic was acidic, as all the plastics tested were. After comparing the evidence plastic characteristics to the known characteristics it could be determined that the plastic was most like PVC. The density test also gave more insight into the type of plastic that it was. We took the mass and volume of all the samples including the evidence to find the density (mass/volume). We observed that the density of the evidence was 1.48g/mL. This density most closely aligned with PVC, which has a density of 1.78 g/mL. The slight difference in densities is most likely due to equipment or technician error. To the left is a photo of the unknown white powder found at the crime scene that was tested The last week of lab was when the unknown powder found at the crime scene was analyzed. The powder was analyzed using a titration using a base with a known molarity in order to find the molarity of the unknown powder as well as its pKa (measure used to describe how strong an acid is) and equilibrium. The molarity of the known substance, KHP, was found by titrating sodium hydroxide (NaOH) into a mixture of deionized water, KHP and phenolphthalein indicator until the mixture during slightly pink in color. The mass of KHP, water, and the indicator multiplied by the molar mass of the compound gave the moles of KHP used in the experiment. This number was about 0.00244 moles. This amount is equal to the moles of NaOH because they have a 1:1 mole ratio. By dividing the moles of NaOH by the liters of NaOH used in the titration, we found the molarity of NaOH, which was 0.1029 M. The second titration involved titrating NaOH into a mixture of the unknown powder from the crime scene dissolved in deionized water, and recording the pH along the way. One mL of NaOH was added at a time until we observed a spike in the pH, after observing a spike we added 0.2 mL of NaOH at a time until the pH plateaued. We then returned to adding 1 mL at a time until another spike occurred, then returned to adding 0.2 mL at a time. The data was then entered into a marked line graph in Microsoft Excel that analyzed volume of NaOH vs PH. From the graph pKa 1 was found to be 1.21 and pKa 2 was 6.75. After comparing the two pKa values to a list of common acids found in wine the substance found at the crime scene was found to be maleic acid. In conclusion, the metal ring can be identified as tungsten carbide and the wine was most definitely tampered with. The plastic card found in the doorway can be identified as PVC and the white acid powder found at the crime scene was determined to be maleic. I hope that the results of our analysis of evidence will assist you in your investigation. If there is anything else that I can do to assist you, don’t hesitate to contact me. Sincerely Bryce Krzenski ...
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