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I am investigating how the concentration of hydrogen peroxide affects the rate of a reaction.

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Introduction

Effects on a named variable on rate of a catalase catalysed reaction I am investigating how the concentration of hydrogen peroxide affects the rate of a reaction. I can find this out by finding out how much gas is given off when I place a piece of potato in different concentrations of hydrogen peroxide. As I change the input variable (the concentration), I will measure the amount of gas that has been collected in three minutes. I am using a potato chip that is 2cm. in length, 1cm. wide and 1cm. deep and I am going to be adding this into hydrogen peroxide, which will be diluted with varied amounts of water. Enzymes are biological catalysts; they speed up chemical reactions in living things. Enzymes are specific, which is to say that they will only catalyse one particular reaction. One particular enzyme is catalase. This is the fastest enzyme, and is found in most living cells. The reaction that I will be using in my experiment is: Catalase Hydrogen peroxide � water + oxygen 2H2O2 2H20 02 This reaction occurs because catalase breaks down hydrogen peroxide producing small bubbles of oxygen. The reason that we are using potato is that it contains catalase, and this can be released when the potato is cut. ...read more.

Middle

* Potato chips Method: To investigate how the concentration of hydrogen peroxide affects the rate of reaction when using the enzyme, catalase, we took a piece of potato measured to the standard size and poured hydrogen peroxide, diluted and undiluted, into a boiling tube. We made a range of dilutions, they were as follows: Volume of hydrogen peroxide (cm�) Volume of water (cm�) Concentration H202 (%) 20 0 100 16 4 80 12 8 60 8 15 40 4 16 20 0 20 0 Each time, the amount of fluid (hydrogen peroxide + water) totalled 20cm�. * Once the correct amount had been placed into the boiling tube, the potato chip was added. * The bung was placed onto the boiling tube as soon as the potato chip came into contact with the hydrogen peroxide. * While the bung was being placed on the test tube the stopwatch was started. * After three minutes the stopwatch was stopped and we looked at the gas syringe to see how much gas has been released. * I then noted down the results. * I repeated the experiment another two times giving me three sets of results. This made my results fairer and more accurate. ...read more.

Conclusion

There could of also of been a slight change in the measurement of hydrogen peroxide or water used. My results show the pattern of a straight line but some points do not lie along it. My line of best fit passes through the point of origin, showing that the concentration is proportional to the rate of reaction. At the end of my line it may of tailed off to another point, that I have marked as anomalous, showing that the rate of reaction did not increase after a certain concentration. Most of my results seem to follow the pattern but there are a couple of anomalous results but the evidence quite strongly supports my prediction. If I were to do the experiment again I would make some alterations. I would test more concentrations with smaller intervals between each measurement. For example o would test 10, 30, 50, 70 and 90% as well to give me a wider range of results, which would also hopefully prevent me getting any anomalies. Another amendment that I could make could be a change in apparatus. If I placed the potato chip into the test tube first and placed the bung on, I could then inject the hydrogen peroxide, perhaps with a syringe, into the test tube. Using this method would prevent me from losing any gas so my results would be more accurate. 1 Lottie De Souza ...read more.

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