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Purpose: Examining variables that affect the rate of a reaction between the catalase found in liver or potato and Hydrogen peroxide. Materials: Liver extract or pieces, potato extract or pieces, 3% Hydrogen Peroxide, test tubes, test tube racks, stopwatch, millimeter ruler, beakers or cups, disposable pipette Cautions – Hydrogen Peroxide is a caustic solution. Wear goggles when using Hydrogen Peroxide. Procedure: 1) Identify what factors you want to test that could affect the rate of the reaction between catalase and hydrogen peroxide. For example, test it in different temperatures (0, 40, 60, 80) 2) Obtain some liver or potato extract and keep in an ice bath to maintain enzyme integrity. 3) Measure out 0.25 ml of extract and place in a clean test tube. 4) Set in test tube rack where the tube is clearly visible. 5) Measure out 1 ml of 3% hydrogen peroxide and place into another test tube. 6) Into this same test tube add 1ml of distilled water. 7) Have a ruler and watch handy. Be prepared to measure the height of the froth and time the movement as soon as the tubes are mixed. 8) Pour the peroxide into the liver extract tube and immediately begin timing and measure the distance from the bottom of the tube to the line of maximum height. If the froth overflows the tube or if the reaction proceeds too quickly, dilute your liver extract with some distilled water and repeat. 9) The actual height of the froth is the height reached during the reaction minus the starting height of the solution. To determine the starting height of the solution pour 2.2.5 ml of water into an empty test tube and measure this height. Rate= height of froth above starting height/ time taken to reach that height Using the technique above to measure the speed of the catalase reaction you should be able to design an experiment to measure the effects of a variable you wish to investigate on the rate of reaction.