Biology Lab Report 2

Biology Lab Report 2 - Biology Laboratory Report...

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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. However, there might be an initial decline in temperature in the mixture as the hydrogen peroxide absorbs energy in order to break down its bonds, making the reaction endothermic at this point of time. When the oxygen and water are formed, a greater amount of energy is needed to form the O-O bond of oxygen and the H-H-O bond of water, causing the mixture to absorb energy, and making the reaction exothermic. In this lab, we take the mass of the potato/liver as a constant, and investigate the difference, if any, in the reaction of potato/liver with hydrogen peroxide, if the volume of hydrogen peroxide used is varied. 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.
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This document was uploaded on 09/08/2009.

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Biology Lab Report 2 - Biology Laboratory Report...

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