Method:
To collect our data we will be measuring the amount of oxygen produced from the reaction, by letting it pass through a tube and let it displace the water in the boiling tube. Then after 30 seconds we will remove the tube from the cylinder. During the 30 seconds we will be measuring the amount of bubbles produced, leading us to know roughly how much oxygen was produced. From the equation at the start we knew that this reaction will produce H2O, this will stay in the boiling tube but the oxygen will pass down the tube and up into the cylinder as tiny bubbles which will hopefully displace the water there.
To get clear results, and accurate conclusions from the experiment we feel that we have to change the concentration 10 times (keeping the total volume of the solution at 10ml) and repeat that a further 3 times. Overall we should end up with about 30 different readings altogether. Total volume- 10ml
This table shows the ranges we will be experimenting with, and how we have reduced the concentration of H2O2 with water. Each of these mixtures will be tested three times with the potato chip, this way we can see if there are any “way out” results from the other two and so with which we can discard that one and get a clear average from the remaining 2 or 3 results, hopefully this will ensure reliability.
Background knowledge:
By looking at what I have planned out already, I now strongly believe that by diluting the concentration of H2O2 with water this will decrease the rate of decomposition of the H2O2, this is because the enzymes found in the potato chip which are the catalysts and help the reaction to work and produce the water and oxygen. But because water molecules are now in there as well, the enzymes are finding fewer Hydrogen peroxide molecules so there are less reactions taking place.
The substance Hydrogen peroxide is a poisonous chemical and that´s why we have to be careful, but also this chemical is found in our liver, and with the presence of the enzymes in our body the catalyst help the decomposition of H2O2 and accelerates it, so water and oxygen are produced a lot faster which is vital for a respiration.
Enzymes are very important because without them some reactions could not take place and we would not be able to survive. An enzyme is a protein and is also known as a catalyst, each enzyme is specific which means that only the right shape and size of a chemical molecule will be able to fit in and be able to let the enzyme help with the reaction. This is also known as lock and key, as because they must be the right shape and size other wise the enzyme cannot take control of the molecule and help it to change into something else.
Our body is full of enzymes because we provide the right kind of atmosphere for them; we provide a steady temperature at 37, food and oxygen which is all they need but if one of these stops or goes wildly wrong it can upset them very easily and the enzymes can stop working and start to die, this would have a major effect on our bodies because they are helping us all the time.
To make these reactions work between the enzyme and H2O2 there must be a certain amount of force to combine them together, they have to collide to set the reaction of. The total kinetic energy of the reactant molecules must be at least as big as the activation energy if the reaction has a chance of working.
Naturally, the kinetic energy of the molecules would be higher when heated up, and so if there is a higher concentration although the temperature stays the same there will be a higher chance that because there are more molecules there will be more successful reactions, and so the overall reaction will occur much faster.
All this depends on the two molecules when collided actually reacting, because in some cases this does not happen, also the transition state does not always proceed to the products of the reaction - it can also return back to reactant molecules. So from this we know that the Hydrogen peroxide might not decompose when it hits the enzyme and so not all of the H2O2 might be used and so we are not getting the maximum amount oh H2O2.
Results:
These are the results I collected after my experiments:
From the results I had collected I have now plotted a graph, showing the decomposition of the H2O2. Starting to look at this graph we can clearly see that with the line of best fit drawn the points are not that far away from this line, showing a quite strong relationship but a negative one which means if we look at the graph that the lower the concentration the smaller amount of oxygen we are producing.
This shallower line almost horizontal shows that it is finding it hard to produce a lot of oxygen because there are not enough molecules for the enzymes to react with. To get an even bigger picture of this experiment we know that our 100% is 10ml of H2O2 so if we increase this to 110% we will have 11ml3 of H2O2 therefore exposing more molecules to the enzymes. This would increase our results and give us a more detailed graph.
My graph still looks a bit odd, and some of the results could be wrong, however I can still pull some conclusions from this and one is that we can definitely see that with the stronger concentration the more oxygen we are producing.
This diagram shows how one enzyme can take on all different molecules at the same time but only if they match the write part. This means that some parts of the enzyme only accept certain molecules for reacting with. In our case the enzymes take on the H2O2 molecules to produce oxygen. As we kept the potato chip the same throughout the experiment the one thing that mattered to us was the concentration of the H2O2 and so as we predicted with the concentration at its highest we found we produced the most oxygen this is because there more reactions taking place and more collision and so there was a higher percentage of reactions.
Evaluation
The data that I collected was reasonable for the accuracy of my experiment, it was fairly reliable meaning that the results we collected were mostly expected but again with human error and contamination there were a few different results, which stood out quite a lot. But by adding the line of best fit everything came together and some basic conclusion were produced but also the results were just accurate enough to back up my prediction quite substantially.
A major cause for concern on accuracy was the reading of the overall measurement of the oxygen produced but also the measurements of H2O2 and water used for the experiment. So if these miss-readings were carried out through the whole investigation then my results will be quite a long way out.
Looking back on experiment I believe that there are many ways to improve it. One way is the accuracy of the measuring of the chips this can be done by an electronic ruler, which has a digital screen that shows the length up to 3 decimal places. This would make every potato chip I use virtually the same length and thickness by using the same cork bora and so this ensures reliability from this. Measuring the oxygen produced is a little harder, to measure this it may include equipment that is not available to me and so cannot be carried out. All that is best is that the same person reads it off just in case someone else’s vision is not as good.
I think the timing was as accurate and reliable as it could be, but only a second or third experiment would back that up fully. The equipment we used was reasonable but not the best, but for the conditions we were based in it was the best we were going to get, I think contamination was minor so that did not cause a problem. One problem with our preliminary experiments was that we had to change the Hydrogen peroxide because we felt that some were to old, and were probably not as concentrated. This could of seriously effected our main experiment with using one chemical but out of several bottles, to eliminate this we must get one bottle big enough for the whole experiment and use that one only; so that there is no change in the quality of the H2O2.
