Chem Lab #3

Chem Lab #3 - Introduction: There are many ways chemistry...

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Introduction : There are many ways chemistry can be used including to solve criminal investigations. In forensic labs, scientists use a technique called chromatography to decode evidence from a crime scene. This process involves the separation of mixtures such as ink, as presented in a ransom note. There are two phases within the chromatography process. The first is the mobile phase, which is the water and/or ethanol, and the second is the stationary phase, which is the water in cellulose. The first step is to test each different pen on chromatography paper and see which ethanol solution produces the best results. After this decision has been made, the retention factor and the length of each pen’s ink components can be measured, which will be explained further in the experimental portion of the report. A retention factor is simply the distance traveled by the component divided by the distance traveled by the solvent. This retention factor value plays a key role in solving the criminal investigation. By comparing the retention factor and ink component values of each pen, with the values from the actual ransom note, the pen that made the ink markings can be determined. Experimental Section : Materials: Black ink pens Chromatography paper Scissors Large beakers Rulers Plastic wrap or beaker cover
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Ink sample from “crime scene” Deionized water 20%, 50%, and 90% ethanol solutions Procedure: The first step was to figure out which ethanol or water solution would show the best results. In order to quicken the experiment process, four beakers were set up side by side so that the four solution tests could be run at the same time. Three beakers were filled with one of the three ethanol solutions and the last beaker was filled with the deionized water. Only a small amount of liquid, or about one to two centimeters, was needed in each container. Then, the chromatography paper was cut to fit each beaker and using the four given pens, four separate dots were drawn onto each sheet of paper. The pens were labeled Liquid Expresso, Office Depot, Stabilo, and Papermate. The dots were spaced out enough so that they would not bleed into each other once they hit the liquid. Also, the dots were drawn about two to three centimeters up so that the liquid had time to absorb into the paper and reach the ink. The containers were covered with plastic wrap to
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Chem Lab #3 - Introduction: There are many ways chemistry...

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