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I am doing an experiment to investigate the factors, which affect the breakdown of Hydrogen Peroxide.

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Introduction

Lydia Boast. 20th May 2003. Biology Coursework I am doing an experiment to investigate the factors, which affect the breakdown of Hydrogen Peroxide. The reaction is catalysed by the enzyme catalyase, which is found in potatoes. 2H2O2 ------ 2H2O + O2 Variables Liquidised potato Hydrogen Peroxide Temperature pH Water The variables may significantly change the outcome of the experiment and therefore need to be controlled in order for the experiment to be precise. The preliminary experiment will help to find what variables make the most difference to the results of the experiment and how to keep the ones that I don't want to investigate constant. Temperature I measured the temperature at the beginning of the experiment and found that it was 20o C. I then performed the experiment and recorded the temperature again after two minutes and found that it was still 20oC. Because the temperature remains constant throughout the experiment, there is no need for a water bath to be used to keep the temperature constant. The temperature needs to remain constant because enzymes only work at certain temperatures. If the temperature is too hot, it might denature the enzyme. As the experiment doesn't raise the temperature there is no need for a water bath to be used as no heat is produced that might denature the enzymes and make the experiment less accurate. ...read more.

Middle

Liquidised potato I used 1cm3 of liquidised potato in my preliminary experiment and found that that was adequate to create a reaction. In two minutes there was enough gas to collect a good reading and there was enough foam to measure. I have decided to keep the amount of potato constant as I feel that varying the amount of potato used would create too much gas and too much foam in two minutes and it would be difficult to collect accurate results so I will keep the amount of potato that I use constant throughout my experiment at 1cm3. Hydrogen Peroxide and Water I used 5cm3 of Hydrogen Peroxide in my preliminary experiment. I found that the amount of gas collected and the amount of foam created changed with the different concentrations of Hydrogen Peroxide, the higher the concentration, the higher the foam rose and the more the amount of gas collected. I have decided to use the concentration of Hydrogen Peroxide as my variable in my experiment as it varies the results but I am still able to collect the results easily. I am going to use different volumes of Hydrogen Peroxide from 0 to 5 and make sure that the volume always equals 5cm3 by adding water to substitute for the volume and dilute the Hydrogen Peroxide. ...read more.

Conclusion

� Keeping the test tube upright in a test tube rack so that it doesn't fall over and spill the potato, measure out the amount of water that you are using in the syringe and again squirt into the test tube. � Measure out the amount of Hydrogen Peroxide needed in the syringe and then squirt into the test tube, being careful that the rubber bung is placed on top so that none of the gas can escape. � Time two minutes on a stopwatch and record the amount of gas that is collected in the tube. � Repeat as many times as necessary and change the measurements of the Hydrogen Peroxide and water until all the results are collected. Prediction I predict that the higher the concentration of the Hydrogen Peroxide, the higher the volume of gas that is collected in the tube. Theory The higher the concentration of the Hydrogen Peroxide, the higher the number of particles there are in the same volume. There are therefore more collisions between reactants therefore the number of successful collisions increases. Therefore as the volume of the Hydrogen Peroxide increases, the amount of oxygen collected should also increase. Table of Results Time (secs) 1st set 2nd set Average Rate of reaction (1 / time) x 103 Infinity Infinity Infinity 0 300 300.6 300.3 3.33 243.6 213 228.3 4.38 207 184.2 195.6 5.11 120 120 120 8.33 61.8 72 66.9 14.95 Analysis ...read more.

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