Variable to keep the same
The variables I will keep the same are mainly the amounts of water in the beaker. The same size beakers will be used. The same bottle of peroxide shall be used and the same potato shall be used.
Safety Used Within the Experiment
The safety I will have to use is firstly safety goggles through out the experiment because of peroxide being used. I shall also have my tie tucked into my shirt, to avoid contact with peroxide and to stop it getting in the way. I will also need a safety tile whilst cutting the potato to ensure that the potato or bench wasn’t in any danger of germs. I will also have to consider the fact that other members of the group were to work along side myself, so I will have to be aware of other people’s movements. The main term of safety is to be sensible and act quickly if any spillage of Hydrogen Peroxide was to occur. I shall also place test tubes in a test tube rack carefully so that they do not break because they are easily broken.
Method
First of all I shall take safety precautions and wear goggles and tuck my tie in. Then I shall set the apparatus up shown in the diagram below.
Measuring cylinder
Clamp
Boiling tube with Beaker
peroxide and a potato
I shall choose a healthy looking potato so that the experiment shall work properly. Then I shall get a little bottle of hydrogen peroxide.
I shall cut a potato into the different cubic measurements listed below and place each potato into hydrogen peroxide for 3 minutes. I have chosen 3 minutes because I feel this is a sensible time from by knowledge from doing my preliminary that 5 minutes is too long and too time consuming. I will do the experiment with 4 different surface areas each 3 times because I feel this is a sensible amount of time to get accurate results. First I will measure the surface area of the potato to my preferred size, then I shall put it into a test tube and put enough Hydrogen peroxide in the test tube to fully cover the potato. I shall then time for 3 minutes using a stop watch how many bubbles appear via the measuring cylinder. I shall repeat this for each surface area and record my results.
Prediction
I feel that as the surface area increases so will the amount of oxygen produced because the enzyme shall decompose the Hydrogen Peroxide faster. I think the surface area will probably be proportional with the oxygen given of however the rate of reaction should increase because the concentration of the substrate will be highest and as the experiment progresses the amount of water in the substrate will increase so the number of collisions will decrease. I think the increase in surface area will reavh a limit when the enzyme becomes saturated but I think this would only work with a high surface area. The activation energy should stay at the amount it is changed to by the biological enzymes. The surface area in this reaction should not change the activation energy, however, because no energy is being added in this experiment.
Explanation
Enzyme
Substrate
This has an active site.
Enzyme
Substrate
The substrate no longer fits the active site.
Preliminary Work
I did a brief experiment in order to receive a more knowledgeable view over the final task. The changes that had to be enforced were that the experiment was done in 3 minutes instead of 5 minutes because 5 minutes was too time consuming and also 3 minutes would work just as well. The usefulness of the preliminary work was that I got the idea of using instruments like a measuring cylinder for example, with more accuracy by measuring below the meniscus. The main advantage of the preliminary experiment, was that in my method I stated that one should use a 100ml measuring cylinder for the retrieval of oxygen, but this test proved that 200ml beaker worked better for the experiment.