Year 12 Chemistry
Abstract: Cold packs are based on the principle of endothermic reactions, which means a reaction that absorbs heat from the surrounding resulting in a temperature drop. Due to this temperature drop, cold packs have many benefits when it comes to injuries such as sprains and strains. It cools the local tissue and reduces bleeding, swelling and pain. It also aids in a speedy recovery. The most commonly used chemical in instant cold packs is ammonium nitrate which will be tested in the investigation along with four other chemicals in water. These other chemicals include potassium nitrate, potassium chloride, sodium acetate and sodium chloride. The two lowest chemicals will then be mixed together at different concentration ratios to see if this drops the temperature further. The chemical/s the produce the lowest temperatures will be tested and compared against a normal frozen cold pack.
A chemical reaction is the process of altering the composition and structure of one set of chemical substances to another.1 Two or more elements react forming a chemical compound. These changes occur due to the movement of electrons breaking and forming new chemical bonds.2 Factors can influence the rate in which the reaction occurs, these include catalyst, concentration, temperature and particle size. All chemical reactions result in changes of energy whether that it through light, sound and of course heat. When energy (heat) is released from a reaction into its surroundings, it is called an exothermic reaction. However, on the hand when heat is absorbed it is called an endothermic reaction.3
The extended experimental investigation requires one to “design and make a pack which when operated will produce hot or cold temperature.” The group chose to attempt to produce an instant cold pack for the experiment. An instant cold pack does not require refrigeration and can be
Bibliography: Carpi, A. “Chemical Reactions”, Visionlearning Vol. CHE-1 (6), 2003. http://www.visionlearning.com/library/module_viewer.php?mid=54 Freeman, LJ Marsella, G. “Hot and Cold Packs”, (1987), Chemmatters http://www.unit5.org/chemistry/Chem%20Matters%20Articles%20by%20Topic/Solutions/Text%20Only%20Articles/Hot%20and%20Cold%20Packs.pdf Scott, K