exp22 - Determination of the Most Efficient Salt for the...

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Unformatted text preview: Determination of the Most Efficient Salt for the Production of Hot and Cold Packs Lab Partners: Matt Bledsoe, Lanier Heyburn, Peter Hill, Hunter Hodge, Anqi Zhou Date: October 23 rd , 2007 Introduction: The purpose of this experiment is to find the best salts suited for making cold packs and hot packs that can reach the desired temperatures and be economically profitable for the Dystan Medical Supply Company. A cold or hot pack is composed of a plastic bag with one compartment filled with water and one compartment with a salt. When the bag is broken, the bag would turn hot or cold as the water dissolves the salt. The temperature of the pack would depend on the concentration of the salt in the water. Since the reactions of the salts and water will either release or absorb heat, this experiment deals with the concept of thermodynamics. When a reaction releases heat, it is exothermic. When a reaction absorbs heat, it is endothermic. According to the First Law of Thermodynamics, energy can neither be created nor destroyed, but is converted from one form to another. This concept is essential in how a cold or hot pack works. The cold pack will have an endothermic reaction, so the absorption of heat from the skin into the cold pack will cool and reduce the swelling on an injury. The hot pack, on the other hand, will have an exothermic reaction, so the heat can be passed from the hot pack to warm the skin. In order to determine which salt is best suited, this experiment will involve testing the enthalpy of dissolution of four different salts, ammonium nitrate (NH 4 NO 3 ), calcium chloride (CaCl 2 ), lithium chloride (LiCl), and potassium chloride (KCl). By determining the enthalpy of dissolution, one can determine whether a salt will have an endothermic or exothermic reaction with water. In addition, one can determine how much of each salt will be needed to produce a cold or hot pack that would reach the desired temperatures and still be economical. Finally, considering the amount of salt needed for a pack, the temperature obtainable by each pack, and the production cost of each pack, the salts best suited for a cold pack and a hot pack can be determined. Since the typical commercial cold packs are made with ammonium nitrate and the commercial hot packs are made with calcium chloride (How do instant hot and cold packs work?), it is plausible to assume that these two salts are most likely be the most suitable ones. 2 Procedures List of Special Equipment (a) MeasureNet WorkStation and temperature probe - This computerized tool will be used to record instantaneous temperature values on a 0.5 second interval from the start of the dissolution of the salt to its finish. The data will be saved as a tab delimited file according to the directions in Appendix 4....
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This note was uploaded on 04/27/2008 for the course CHEML 1311H taught by Professor Robinson during the Fall '07 term at University of Georgia Athens.

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exp22 - Determination of the Most Efficient Salt for the...

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