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Unformatted text preview: Priyal R. Chitale IBD Year 11 Dhirubhai Ambani International School Biology Laboratory Report – Endothermic & Exothermic Reactions Aim : To investigate the type of reaction that takes place when hydrogen peroxide reacts with liver, and when it reacts with potato, and to determine whether the two reactions are endothermic or exothermic. Hypothesis : If hydrogen peroxide is added to liver/potato, the reactions should be exothermic, that is, the temperature of the mixture should rise. Constant – mass of the liver/potato Controlled variable – volume of hydrogen peroxide Uncontrolled variable – temperature of the mixture Introduction : Hydrogen peroxide or H202, when broken down, gives oxygen (O2) and water (H20) – an enzyme contained in many organic substances including potato and liver called catalase acts as a catalyst in the decomposition of hydrogen peroxide. A catalyst is a substance that speeds up a chemical reaction without being used up itself. Therefore, the catalase in potato and liver catalyses the chemical reaction of the decomposition of hydrogen peroxide, so that we get oxygen and water in a shorter period of time. The reactions of hydrogen peroxide with liver, and of hydrogen peroxide with potato should both be exothermic, that is, the temperature of the mixture of hydrogen peroxide and liver and the mixture of hydrogen peroxide and potato should increase. All chemical decomposition reactions are endothermic reactions, however, decomposition reactions that are catalysed by catalase are all exothermic reactions, because when the decomposition of a compound is catalysed by catalase, it emits or gives out energy, thus its temperature increases. Note: All temperature readings taken in course of the experiments are in Centigrade. Apparatus • A mortar • A pestle • Potato slices • Liver • A scalpel • Hydrogen peroxide • A measuring cylinder • A beaker • An electronic temperature sensor • A pair of latex gloves • 2 watch glasses • A digital weighing balance • Tissue paper Method 1. Wear the latex gloves before beginning the experiment. 1 Priyal R. Chitale IBD Year 11 Dhirubhai Ambani International School 2. Cut out a small amount of liver, and chop it into tiny pieces using the scalpel. 3. Find the mass of the liver, using the weighing balance. 4. Transfer the chopped liver from the watch glass to a beaker....
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This document was uploaded on 09/08/2009.
- Spring '09