5) The time was checked constantly by a stopwatch so that this time counting would help us to work out the rate of bubble release.
6) The volume of water kept in the boiling tube into which the bubbles were being released was kept constant at 10 cm3 throughout the experiment.
My prediction, which I am not taking for granted, is that obviously oxygen bubbles will be produced which should eventually increase at rates, which are being recorded, and then eventually the bubble release will decrease until only water is left in the boiling tube until all the oxygen is gone.
To enhance my experiment, 2 observations were carried out for each value of 2,4,6,8,10,12 potato strips. Thus, 12 readings were taken so as to cover a wide range of values for the best results. Two readings were taken so as to confirm the validity of the first once since by taking an average one is not necessarily making one’s results more accurate. Also, results were limited due to a time limit.
Apparatus: 10ml Water, 20ml Hydrogen peroxide, potato strips of the same width and from the same source, Stopwatch, Boiling tubes, Boiling tube holder, Measuring tube, Scalpel, Pipette, Ruler, White Tile, Core taking device and Results sheet.
Throughout the experiment safety procedures were upheld and safety was kept due to cooperation and concentration. Firstly safety goggles were constantly worn and we were very careful with the chemicals since hydrogen peroxide is an oxidising agent and so is harmful to the skin and so if contact was made with the skin, the area of flesh was rinsed thoroughly. Also, care with the scalpel and cutting was upheld since a cut would be a very direct form of harm, also if any chemical were to enter a wound it would act as an irritant. However, general respect and consideration were constantly carried out throughout the whole experiment. Also, secondly to our own importance was the safety of the equipment and so we were careful with the equipment for example I never turned the pipette upside down so as to ensure the rubber part of the pipette was not damaged.
As a general point from the experiment, I discovered that it would be easier to do a pre-investigatory trial of the experiment so as to ensure that all the settings were adequate for the main experiment and so mistakes were altered. However, also I was worried about the fact that maybe as more and more potato strips were put in, maybe they would begin to obstruct each other and prevent bubbles from being released.
Obtaining Evidence.
Method: The first part of the experiment was to measure 10 ml of water, which was poured into the boiling tube; this was to be the water through which the bubbles would pass. Then, 1mm thick discs of potato were taken from a potato with a core-taking device. These discs were then put into a boiling tube. It was also important that these discs were kept fresh so that this would not affect the experiment. Safety goggles were worn at all times to make sure that no danger came from the handling of the oxidising agent, hydrogen peroxide, also to combat this danger, if any hydrogen peroxide was spilt on any part of the body, then it was washed off as quickly as possible. The next procedure was to pour 20ml of hydrogen peroxide into a boiling tube, which contained some potato strips, and then the rubber bung was positioned, having been lubricated with Vaseline. Now that this had been done, this apparatus was attached to the other boiling tube of water. The tip of the delivery tube was 2mm below the surface of the water so as to keep the pressure constant and as low as possible. When, the apparatus was fully set up and active, the stopwatch was started. Also, the temperature and pH were measured and kept constant before each reading was taken. The timing measured how long the first bubble took to appear and then how many followed the first over the next two minutes. This procedure was repeated several times and for each quantity of potato strips, the experiment was repeated so as to gain an average. Finally, the results were taken down on a ready prepared results sheet. Thus, throughout the experiment, the variables were controlled since after doing two readings for every number of potato discs I then moved onto the next reading of potato discs. When cutting the discs at the beginning of the experiment I was very careful to make sure that they were all of the same width of 1mm thickness since a few mm difference could affect the results. The volume of hydrogen peroxide was kept at 20 ml but changed every time for a new set of readings but the molarity was kept constant at 1. All the strips were from the same potato. Most importantly the temperature, pH and time were monitored by the use of a thermometer, universal indicator and a precise stopwatch. Thus, 6 measurements provided a suitable width and so two measurements were taken for the number of bubbles released for 2,4,6,8,10, and potato strips.
I also made several other relevant observations. Firstly, it is very likely that the potato tissue was damaged in the cutting and some enzymes may have been lost. The readings were only taken in two minutes since anything longer would have been too long and anything shorter would not have allowed enough bubbles to be produced and we were also limited by time. Also, concerning time keeping, my stopwatch was very unreliable and also the experiment required one to use a very high level of manual dexterity during the experiment and so a few seconds may have been lost due to human error.
Results:
Results Table.
Results.
At the beginning of the experiment the room temperature was noted to be 19˚c and the pH was 6. After the hydrogen peroxide was added, the liquid began to show signs of activity in frothing and bubbling, this was an obvious sign that oxygen was being produced and this was confirmed by the produced oxygen appearing in the form of bubbles at the end of the delivery tube and into the 10ml of water. If there had been more time for the experiment it is likely that there would have been no hydrogen peroxide but merely water since it would have been catabolically broken down into two natural substances, well known by man, oxygen and water- produced by catalyse enzymes breaking down some potato cells. More specific results are shown in the tables above.
Analysing Evidence.
From the graph it is possible to see that between 4-8 potato discs the number of bubbles produces increases from 9 bubbles produced on average in two minutes to 19 bubbles on average in two minutes by 8 potato discs but the shape of the graph suggests that from 8-10 the number of bubbles produced begins to drop but then suddenly rises. Thus, it would be possible to make a potential conclusion that the dependent variable begins to increase as the independent variable increases and then eventually the number of bubbles produced on average begins to decrease and then for a particularly bizarre reason the number of bubbles begins to increase again sharply just as it looks like the rate of reaction is beginning to drop it suddenly rises. Thus, there are two bends to the graph. Thus, it could be concluded that as the potato discs increase the number of bubbles produced increases and then drops before mysteriously increasing again.
By analysing the graphical curve of the graph in sections, I can demonstrate what has occurred. The graph can be divided into three sections. The first of these sections is 2-8 potato discs along the X-axis when the number of bubbles produced on average in two minute rises from 3.5 to 19; this therefore is an increase of 1bubble every ten seconds on average. Then the second major part of the graph can be seen as the number of bubbles begins to drop slightly from the readings of 8-10 potato discs. Here the readings drop from 19 on 8 potato discs to 16.5 on 10 potato discs. This however is a minor drop in comparison to the rate of increase; this is a drop of 0.2083˚ every 10 seconds on average. The third and final part of the graph is the point of 10 potato discs to 12 potato discs as the shape of the graph begins to shape up to increase. The readings rise from 16.5 on 10 potato discs to 23 on 12 potato discs; this was an increase of 0.541666667 bubbles per 10 seconds on average.
Obviously, the shape of the graph was unexpected by myself but by using my scientific knowledge I will attempt to form a scientific explanation. The experiment begins normally and expectedly with the rate of reaction increasing at a steady rate and as the experiment reaches between 6-8 discs the rate of reaction which is still increasing begins to fall, so this starts a decline from 8-10 potato discs. Up to this point all of the results were anticipated to a certain extent. The enzyme catalyse has been reacting with the substrate of potato and so the rate of reaction has started and has carried on increasing at a steady rate as more and more potato discs are put in then as there is more substrate to react with the number of bubbles produced increases since there is more substrate available to the active binding sites. Then the curve begins to drop ever so slightly. This drop can be explained since there should be a point when the number of bubbles begins to drop maybe as the rate of reaction just follows a natural shape and decreases or maybe there are so many potato discs in such a small space that the discs begin to prevent the full surface area being exposed and hinder any bubbles being released. This may explain why there is an ever so slight decrease. Also this decrease may be an error in the experiment and this decrease may have been the curve staying the same or even increasing slightly, thus, the decrease is so slight that error must be taken into consideration. In the final part of the graph, the curve begins to unexpectedly rise and this was certainly not predicted but I think that it can be explained by the possibility that with 10 potato discs there are too many to produce enough bubbles to sustain the rate and the discs begin to get in each others way but when there are 12 potato discs this results in there being enough potato discs to oversee this problem and although they obstruct each other there are enough to carry on producing up to 23 bubbles on average per 2 minutes. Thus, the fact that there are not enough bubbles to overcome the obstruction for 10 potato discs but there are enough potato discs to cancel out the obstruction and continue the production of bubbles at a faster rate would be a possible explanation for the rise in the graphical curve in the last part of the graph.
My original prediction was that the rate of reaction would increase steadily as expected and then decrease as the enzymes could not sustain the rate of reaction throughout and then the graph would dip at the end steadily and the graph would be similar to a “rainbow” like shape or it could be compared to a quadratic parabola graph with a negative coefficient. However, my prediction was right to a certain extent since I predicted a rise followed by a fall, although I believed that the rise and fall would be small but the gradient varied significantly, however, I did not predict that there would be a sudden rise at the end of the graph and so this part of my prediction was not true and to confirm me even more incorrect the final rise was the quickest increase of the experiment and the graph was more of a cubic graph. Thus, my prediction was right to a point but then the final part of the experiment introduced a new perception to the experiment.
EVALUTATING EVIDENCE
I think that this method was an adequate method. However, I found that it was hard to cut the potato strips into an exact width due to human error, and also there would be an uneven value of catalyse in each strip of potato. Although I attempted to keep the tip of the boiling tube 2mm below the water level, this was very hard to maintain since it is hard to be consistent with 2mm only. The experiment would have been more suitable and more accurate, had I used a more complex apparatus and had more time. Thus, I believe that my procedure was suitable but I would have liked to have taken more readings.
I am willing to accept that the results were not as accurate as they could have been but when one takes into account the limitations and restrictions, I believe that my results were as good as they could have been. Unfortunately, much time was lost to the fact that the stopwatch that I used was very poor and frequently faulted and some time was lost as the stopwatch was started and then the bung was placed as quickly as possible and so sometimes the first bubble had emerged by the time that I had completed the experiment. There was only one real rogue result and that may have been for 12 potato discs since the bubbles are being produced so quickly with 12 discs that it is possible that some results may have been missed or maybe the increase for the number of values for 12 potato discs was a valid reading. However, I tried to compensate for any problems by doing all the readings for the potato discs twice just to confirm that there were no odd results.
I believe that my results are accurate if I my justification for the potential rogue result is true, since I was aware of all problems throughout the experiment and came to the conclusion that they would not alter the readings of the experiment. However, the data was extremely different, and had I not paid attention to the experiment and taken an average or two readings I would have not been able to confirm my results. For my purposes, I believe that my results were accurate but I would not base any further scientific experimentation on merely my results but maybe culminate more to find an average.
My first concern about this experiment is that by taking all the readings from one source of potato, it is possible that the potato I took my readings from was defected and so all my readings will be from an impure source which may have been catalyse deprived or abnormally catalyse rich and so I would repeat the same experiment but with two sources of potato just to ensure that the readings are similar for potatoes since I have no justification that my potato is the stereotypical potato. I would also use more complicated apparatus since the apparatus is simple and easy to use but it would be possible to find a point to sacrifice complication for improving the accuracy of one’s readings. I felt that the experiment could have been kept in a temperature bath just to ensure that the temperature was constant throughout since from the background information I learnt that enzymes are affected by temperature. Also, although I carried out a pre-investigatory trial to decide and help to plan a method I would have preferred to do another one just to confirm any variables for my ultimate experiment. I believed that the range should have been extended but on the other hand one had to take into account human resources and time. I believe that the results were slightly limited due to time and the surface area was affected due to the lack of space in the boiling tube and so this would have affected the experiments results. Thus, the range should have been extended in order to see the shape over more readings and I would have liked to taken each reading over more time just to see the effect. Thus, the recommendations in the paragraph are the ways in which I believe that the experiment could be improved for anyone doing the experiment.