Extended Experimental Investigation
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. Introduction:
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 stored for months and be able to produce cold temperatures anywhere, anytime. They are quick and easy to use, consisting of two or three compartments separated by breakable barriers. The compartments contain various chemicals which when the barriers are broken combine together resulting in an endothermic reaction. Instant ice packs are commonly made from ammonium nitrate and water.4 The reaction is not reversible and therefore can only be used once.5 Ice packs in generally are used as a technique to care for pain, injury and the discomfort of joints and muscles. They play a crucial part in the first step of the treatment for sprains, strains, muscle pulls and other such injuries. 6 Ice packs are also commonly used in the rehabilitation of injuries and other long term chronic problems (eg. arthritis). If used correctly and immediately after an incident occurs, it can reduce swelling as well as tissue damage, blood clots, inflammation and muscle spasms. The pack can also assist in the reduction of pain by numbing the affected area. The cold temperatures increase the flow of nutrients, assist in waste removal, increases strength and encourage healing; essentially, it means one will heal faster. Furthermore, they constrict blood vessels round the affected area and cools surrounding tissue. This slows blood flow as well as cell metabolism, which can decrease the chance of hemorrhage and even cell death in serious cases. To ensure a quick recovery follow the R.I.C.E.R principle: Rest – Avoid movement to reduce further damage.
Ice therapy – Cools tissue, and reduces bleeding, swelling and pain. Ice for 20minutes every 2 hours. Compression – Reduces bleeding and swelling.
Elevant injury – Reduces bleeding and swelling.
Refer to a doctor/physiotherapist – full recovery more likely7
Normal frozen gel cold packs and the ordinary bag of ice can range anywhere between -17-0°C. This can actually be causing the body more harm than good resulting in freezing of the skin. In...
Bibliography: Carpi, A. “Chemical Reactions”, Visionlearning Vol. CHE-1 (6), 2003. http://www.visionlearning.com/library/module_viewer.php?mid=54
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
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