The Effect of Changing Surface Area and the Volume of Oxygen Produced From a Reaction Between Hydrogen Peroxide and Catalase

The Effect of Changing Surface Area and the Volume of Oxygen Produced From a Reaction Between Hydrogen Peroxide and Catalase
Aim In this experiment I will investigate how changing the surface area affects the volume of oxygen produced when hydrogen peroxide is reacted with catalase enzyme. Background knowledge An enzyme is a biological catalyst. A catalyst is a chemical substance that alters the rate of reaction, by providing a route with a lower activation energy, without being chemically changed itself. Enzymes are proteins, and each enzyme controls a particular reaction. ?Enzymes have clear-cut three-dimensional shapes and an area where the substrate (the substance that the enzyme is designed to react with) fits into the enzyme. This area is known as the active site. Each enzyme can only can only break down one kind of substrate molecule into different sorts of product molecule.? The diagram below shows the principle behind how enzymes work
Enzymes are affected by temperature and pH. Temperature ? After 40Â?C, enzymes stop working. This happens because increasing the temperature modifies the three-dimensional shape of the enzyme. Once the shape has been modified, the substrate no longer fits the active site of the enzyme exactly. pH ? Enzymes work best in neutral conditions. The pH of a solution can cause an enzyme to stop working (like temperature can). Enzymes that no longer work are termed denatured. Hypothesis I predict that as the surface area of the potato cubes increases, then the amount of oxygen produced will increase, so if the surface area of the potato cubes triples then the amount of oxygen produced will triple. I predict that this will happen because as the surface area increases, there are more catalase molecules for the hydrogen peroxide to collide and react with successfully. If there are more successful collisions then there will be more oxygen produced. I also predict that total surface area and volume of oxygen produced will be directly proportional. Direct proportionality between total surface area and volume of oxygen produced would be shown by a straight line on the graph. The equation for this reaction is: catalase [image]Hydrogen Peroxide Oxygen + Water catalase [image]H2O2 O2 + H2O My hypothesis is based upon the collision theory. The collision theory states that ?the particles of the reacting substances must collide with each other and a fixed amount of activation energy (Ea) (the minimum energy required before a reaction can take place) must be reached if the reaction is to happen. If a collision between particles can produce enough energy a reaction will happen?. However not all collisions will be successful (result in a reaction). The diagram below gives an idea about activation energy. [image] The diagram below shows how the use of an enzyme affects the rate of reaction. Apparatus
1 stand and one clamp
1 water trough
1 250Ml glass measuring cylinder
2 100 Ml plastic measuring cylinder
1 thistle funnel
1 capillary tubing
1 length of rubber tubing
1 size 45 rubber bung with two holes drilled in the centre
Stopwatch
Hydrogen peroxide 20 vol
Potato cubes (1cm x 1cm x 1cm)
Safety As with all scientific experiments and investigation, safety is very important. For this experiment we will take the following safety precautions: 1. Wear safety goggles 2. Mop up any spillages 3. Wash chemicals that make contact with the skin immediately with running water 4. Put stools under benches 5. Put bags under benches 6. Always stand when performing the experiment Variables and constants Variables In this investigation I will change the surface area of the potato cubes. Constants In this investigation I will keep the following factors constant:
Concentration of hydrogen peroxide
Temperature
Volume of hydrogen peroxide
Time
Concentration of hydrogen peroxide ? If the concentration of the hydrogen peroxide changes then it will have an effect on how the volume of oxygen produced. When the concentration of the hydrogen peroxide is increased then there are more molecules of hydrogen peroxide present in a given volume (e.g. 50Ml). With more molecules present this means that there is more opportunity for the molecules of hydrogen peroxide to collide and react with the molecules of catalase. Temperature ? If the temperature is increased, then the volume of oxygen produced will increase. ?An increase in temperature of about 10ºC approximately doubles the amount of oxygen produced. When a mixture of substances is heated, the particles move faster and gain more kinetic energy, and because of this, two things will happen. The particles, because they are moving faster, will collide more often in a given time and they are more likely to be involved in more collisions. As a result of the particles moving at a faster rate a large proportion of the collisions will exceed the activation energy and hence the volume of oxygen produced increases. Volume of hydrogen peroxide ? If the volume of hydrogen peroxide is increased, then it means that there are more particles in the hydrogen peroxide to react with the catalase. If there are more particles present to react with the catalase molecules, then the volume of oxygen produced will increase. Time ? If the time given to the reaction between catalase and hydrogen peroxide is increased, then it means that the particles of hydrogen peroxide have more time to collide and react with the molecules of catalase. This means that the volume of oxygen produced will increase. Method I first filled a water trough with water, and put it on the base of clamp stand. I then took a 100ml measuring cylinder and filled completely with water. I then upturned it and put it in the water trough without letting any of the water in the measuring cylinder escape. I then lowered the clamp down and attached it to the measuring cylinder. The clamp and measuring cylinder were then both moved up until the mouth of the measuring cylinder was just below the water level. After doing this, I then took a 100ml conical flask and put the potato cubes in it. I then put the bung, which includes the thistle funnel and capillary tube, on to the conical flask. With that done I put the plastic tubing into the water trough and then poured the hydrogen peroxide down the thistle funnel. I watch for the bubbles of the initial burst come out and then I put the plastic tubing into the measuring cylinder (at the mouth). I then started timing the reaction. The diagram below shows how the equipment was set up. see next page for diagram Preliminary work Prior to conducting the actual experiment, I conducted preliminary work using the method that I described above. The preliminary work influenced my decisions on the measurements and accuracy of readings. The table below shows the results of the preliminary work. 50ml of hydrogen peroxide did not cover the potato cubes, so we tried with 70ml. 70ml covered the potato cubes. I also found that the best way to get potato cubes of the same dimensions was to first cut the cubes with the potato chip cutter, and then put the potato chips back in the cutter perpendicular to the blades and cut them again. This would produce cubes of the same size. No of cubes Time (mins) Volume of oxygen produced (cm3) 6 1 too little to be measured 6 2 too little to be measured 6 3 5 6 4 7 6 5 9 22 1 10 22 2 18 22 3 24 22 4 31 22 5 36.5 Measurements For this investigation, I will take use the following amount of cubes: 6, 10, 14, 18, 22 and find out how much oxygen is produced in 5 minutes. Considering that I will have to do 5 experiments including repeats and that I only have limited time available, I have decided to choose a timescale of 5 minutes because it allowed me to produce a sufficient amount of oxygen with the minimum number of cubes. The minimum amount of potato cubes used will be 6 because in the preliminary work, you can see that in the results that 6 potato cubes gave me 9ml of oxygen in 5 minutes and as I consider this to be a measurable quantity in the time scale allowed I have chosen to use this as the minimum surface area. 22 cubes was been chosen as a maximum as I need a minimum of 4 observations to show my results on a graph. Also to make more than 22 cubes would be too time consuming and would not allow me to complete the experiment in the time I had available. I will repeat this twice, and take an average reading. If I do have time, I will perform the experiment for a third time and take an average of the two of the two results that are closest together. Any anomalous results will not be included in the average. Accuracy of readings I will take the accuracy of my readings to 0 decimal places because the 100ml measuring cylinder only has intervals of 1 (i.e. between 10 and 20 there are intervals of 1 between them). Accuracy of experiment The clamp stand will hold the measuring cylinder vertical, which makes it hands-free which means that I can concentrate on recording the results. The fact that the experiment is hands-free means that the cylinder will not be slanted and so produce incorrect results. I will also use potato cubes that are 1cm x 1cm x 1cm. To do this I will cut the potato using a potato chip cutter, and then I will put the chips back into the potato chip cutter and cut them up again to produce cubes. To measure the amount of hydrogen peroxide produced at the end of the 5 minutes, I will pull the rubber tubing out from the mouth of the measuring cylinder. This will ensure that no oxygen bubbles will get into the measuring cylinder after 5 minutes. I will then read the reading of the volume of oxygen produced off the cylinder while it is still being held by the clamp stand. This will ensure that the cylinder is not slanted when the reading is taken. When it comes to measuring the amount of oxygen produced, I will not count the bubbles produced, as they may be of different volumes. Instead, I will use a measuring cylinder to measure the amount of oxygen produced, which is a lot more accurate than counting the bubbles. Obtaining Evidence -???????- Volume of hydrogen peroxide (ml): 70 Cylinder capacity (ml): 100 Area of one side of a potato cube (cm2): 1 Potato cube volume (cm3): 1 Total surface area of one cube (cm2): 6 Volume of oxygen produced in 5 mins (cm3) No of cubes Total surface area (cm2) Test 1 Test 2 Test 3 Average result 6 36 12 8 8 9 10 60 15 13 11 13 14 84 23 16 15 19 18 108 25 24 18 22 22 132 28 18 22 23 Items marked red are anomalous results and are omitted from the average Analysing Evidence -???????- [image][image] I can see a definite overall trend in these results which are shown by the graph. As the surface area of the potato cubes increases, then the volume of oxygen produced in a certain amount of time increases. This is shown by looking at the results. We can see that as that when the total surface area is 36cm2, we can see that the volume of oxygen produced is 9cm3. When the total surface area is 60cm2, we can see that the volume of oxygen produced is 13cm3 and finally when the total surface area is 84cm3, the volume of oxygen produced is 19cm2. I can also state that there is a moderately strong positive correlation between the total surface area and the volume of oxygen produced. However the trend that I have identified shows that the volume of oxygen produced did not triple when the total surface area of the potato cubes was tripled. Therefore it is not appropriate to say that when the total surface area triples then the volume of oxygen produced will triple. This is shown by looking at the results. We can see that with a total surface of 36cm2 the volume of oxygen produced is 9cm3. However when the surface area is tripled to give us 108cm3 we see that 22cm3 of oxygen is produced. 22 divided by 9 does not give 3, it gives 2.444â??. The overall trend was affected by the fact there was an anomalous result (which is the circled result on the graph). This anomalous result was caused because there was an anomalous result in one of the tests that I conducted. When all the results from the three tests are compared, I can see that a result in the 1st test was anomalous. This anomalous result, which was 28cm3, was not added to the average of the results. The anomalous result affected the graph because I originally had 3 results, however when the anomalous result was removed, this left two results. This meant that I had to add up the two results and divide by 2. This produced a smaller result than the result that would have been produced if the anomalous result had not been left out. The explanation behind the total surface area increasing and the volume of oxygen produced increasing is collisions. The particles of hydrogen peroxide are colliding with the molecules of catalase and reacting. As you increase the surface area you are exposing more molecules of catalase to the hydrogen peroxide particles. This means that there is a greater chance for hydrogen peroxide particles to collide and react with catalase molecules (a successful collision). The graph however is not a straight line (which shows direct proportionality), instead it is a curve. The probably ended up levelling off because of the potato cubes clumping together and decreasing the surface area, which meant that there was less catalase molecules exposed to the hydrogen peroxide particles. By comparing the graph that I have produced and my original hypothesis I can say that I have supported part of my hypothesis, however I have disproved the quantifying part of my hypothesis ("so if the surface area of the potato cubes triples then the amount of oxygen produced will triple"). I have disproved the quantifying part of my hypothesis because not all of the results form a straight line, which shows direct proportionality between the volume of oxygen produced and total surface area. The results that do not support the part of my hypothesis on proportionality have been circled on the graph. Evaluating Evidence -???????? Evaluating the results I am not happy with my results because they did not allow me to fully prove my hypothesis. I think that my results are not accurate because they did not allow me to fully prove my hypothesis. I do however think that using a measuring cylinder is a lot more accurate than counting bubbles, because bubbles can have different volumes of oxygen in them. However I do not think that this is the most accurate method. A more accurate method would be to use a gas syringe. From one of the experiments that I did, I found that there was an anomalous result. This was in the 1st test (the last result which was 28). These results probably occurred because of the rubber tubing not being in the same places during that measurement. If the rubber tubing is not in the same place in the measuring cylinder, then it can cause an increase in the amount of oxygen bubbles coming out of tube, which would thus affect our results. It may also be, like I said in the analysis, due to clumping of the potato cubes which decreased the surface area and hence affected our results. However even with the anomalous results I can still draw a definite conclusion that as the total surface area of the potato cubes increases, then so does the volume of oxygen produced from the reaction. If we look closely at the repeat results then we can see that there are fairly large gaps between some results and small gaps between other results. This probably occurred because the rubber tubing was not in the same place inside the measuring cylinder when did the various measurements and repeats. If the rubber tubing is not in the same place in the measuring cylinder, then it can cause an increase in the amount of oxygen bubbles coming out of the tube, which would in turn affect our results. Evaluating the procedure I think that the part of the procedure that produced anomalous results was the placing of the rubber tubing at the bottom of the measuring cylinder. I think this because it was very difficult for us to the rubber tubing in exactly the same place both times. If I were to repeat this experiment and fix this problem, I would use a gas syringe. Another part of the procedure that could have caused anomalous results was the size of the potato cubes. In each experiment, we tried to use the same size potato cubes, however it was difficult for us to get the same size potato cubes each (either by using a knife or using a potato chip cutter). If I were to repeat this experiment and fix this problem, then I would use very accurately measure the potato cubes and cut them precisely. Another factor that could have contributed to the anomalous results was the initial burst. After we had poured the hydrogen peroxide, we then had to wait for the initial burst of air to come out. This would of caused anomalous results because we did not know how much air had been displaced in the measuring cylinder. If I was to repeat this experiment again, then I find out how much air had been displaced from the measuring cylinder, and subtract that from the result that I got at the end of the experiment. Another factor that could have contributed to the anomalous results was the fact the potato cubes for each experiment had come from different potatoes. The fact that they had come from different potatoes means that there may be different amounts and/or different concentrations of catalase in the different potatoes. If I were to repeat this experiment again, I would attempt to get all the potatoes cubes for all the experiments in a series from the same potato. This should minimise the risk of changes in amounts and concentration in the potato, which may mess up the experiment by causing us to get anomalous results. Further work If I were to extend this investigation, then I would test to see how much oxygen is produced when hydrogen peroxide is reacted with other enzymes. From this I would then conclude which was the better enzyme. Another extension would be to use different sources of catalase and see if I get a similar pattern.

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