I cannot control how much heat energy is given out when the Hydrogen peroxide decomposes, although the temperature around the investigation will remain fairly constant, at room temperature of around 20i?? C. 2. Concentration of catalase-Although this is not easily controlled (as the amount of liver is not easy to measure), I try to use the same amount of liver in each experiment. Other things that will affect the results o the experiments are: Oxygen escaping when the liver is first added to the hydrogen peroxide. -Gas escaping from the gas syringe. -Inaccurate reading of results.
-The stopclock not being started at the same point in each experiment. Apparatus required: 1. Conical Flask-where the decomposition of hydrogen peroxide takes place. 2. Hydrogen peroxide of concentration 5 volume, 10 volume, 15 volume and 10 volume. 3. Liver-used as the source of catalase for this experiment. 4. Bung with delivery tube-To seal the conical flask and collect oxygen gas produced during the decomposition of hydrogen peroxide. 5. Gas syringe-Measures the amount of oxygen produced. 6. Stopclock-Times 1 minute so that we can calculate the rate of reaction. Risk analysis
Hydrogen peroxide is used as a bleach, so it will be handled very carefully. Results The table overleaf shows my results from this investigation. I took two readings each time to gain a better picture of my results and so that I could see whether there were any anomalous results. On the whole, I am pleased with my results although some seem to be a little anomalous. To test my hypotheses I shall draw a graph with lines to show the rate of reaction for each experiment in the investigation. Results analysis This set of results appear, on the whole, to support my hypothesis.
There is a general trend where the higher the concentration of the hydrogen peroxide, the faster more oxygen gas is produced. More oxygen gas would be expected to have been produced with the higher concentrations of hydrogen peroxide because as the concentrations go up, the more oxygen is produced and this is how the strength of the hydrogen peroxide is measured. For example, 1cmi??of 1V hydrogen peroxide will produce 1cmi??.
So, if we take the 10cmi?? 2. 5V hydrogen peroxide used in my investigation, if it had been left to fully decompose, 25 cmi?? oxygen gas would have been made. Therefore the 2. 5V hydrogen peroxide used in my experiment had fully decomposed, and no more oxygen gas could have been produced, which explains why the amount of gas produced levelled off at the end of the 5 minutes in which it was being tested. The hydrogen peroxide of higher concentrations continued producing gas after the 5 minutes in which I was timing the decomposition of the hydrogen peroxide was up.
I could not measure past 100cmi?? of oxygen gas, as my gas syringe was not large enough. My hypothesis was that where there is a higher concentration of hydrogen peroxide, the rate of reaction is faster. We can see from my table and graphs that on the whole my results support this hypothesis. Saying this, there are still anomalous results. Having checked my 12. 5V hydrogen peroxide result twice, it was still a little slower rate of reaction than that of the 10V hydrogen peroxide (which I also checked twice).
My results appeared to improve once I had checked them, although the results which I have plotted on my graph are averages of the two sets of results for each concentration of hydrogen peroxide. If there is an anomalous result, it will change the overall value of the averaged result, which can affect how accurately the results are shown. Other factors that can affect the results are: -That the experiment will not be timed accurately and that readings are taken at the wrong time, which gives an inaccurate result for that time.
-The gas syringe did not work properly, for example if the gas syringe was broken or if it stuck, an accurate reading would not be possible as the pressure would build up inside the gas syringe until it moved. This wouldn’t give an accurate result as the gas syringe would not show a different value every ten seconds. -The surface area of the liver used could also affect how well the experiment worked because if there were a greater surface area, there would be more area for the catalase to be in contact with the hydrogen peroxide, therefore more hydrogen peroxide would be exposed to the catalase in the liver.
I would expect this to make the rate of reaction faster as there would be more catalyst readily available to speed up the reaction. -The size of liver used will affect the results, for example, if the size of one piece of liver was larger than another piece of liver used with the same strength and amount of hydrogen peroxide, the hydrogen peroxide containing the larger piece of liver will have a faster rate of reaction as it will contain more catalase.
-Any error in measurement throughout the experiments in my investigation will affect the results in this investigation, for instance if the hydrogen peroxide was measured incorrectly, different results will be found which could possibly be anomalous. Most of these factors affecting my results are out of my control, such as whether the gas syringe is broken or the size and surface area of the liver (because it is almost impossible to weigh such a small piece of liver).
The pieces of liver I used were only approximately the size of a grain of rice, although some were inevitable larger or smaller. Errors in my measurement, however, can be controlled and so I was very careful whilst measuring everything out and timing my experiments. Rebecca Allot 11Y Page 1 03/05/2007 Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.