I have chosen to vary the lengths of the potato for my variable. I think that this variable will produce the most accurate results, and the most varied results.
I will use 5 different lengths of potato. These will be.
Prediction.
I predict that the bigger the cylinders of potato’s are, the bigger amount of oxygen will be produced. I think this will occur because there will be a larger surface area for the hydrogen peroxide to react with, in turn making more oxygen.
Predicted graph.
Axes 1 represents rate of reaction. Axes 2, represent’ length of catalyst. As you can see from the graph, I predict that the greater the length of the potato the greater the rate of reaction.
Fair test.
To make this experiment a fair test I will have to:
- Make sure I use the same equipment all the way through the investigation.
- Make sure I measure the potato’s correctly
- Make sure the gas syringe is at the same angle all the time.
- Make sure the clamp stand is at the same height every time
- Make sure I use the same amount of hydrogen peroxide for every cylinder of potato
Observations.
I will make sure that I.
Make observations every 1 minute, I will do this for 10 minutes for each length of potato. I will repeat the above twice for each length of potato. So if the results don’t match up I will repeat the experiment again, because the two separate results should be very similar.
I will use the average of the results, so that we find a medium of the two results.
Secondary sources.
Properties of enzymes.
- There are 700 identified types of enzyme.
Living organisms have hundreds of different chemical reactions going on inside them. Some of these reactions need happen to happen quickly. The reactions could be sped up heating the reactants. But living cells are quickly killed, their temperature goes to high. So living organisms use ‘catalysts’ to speed up their reactions. These catalysts are called ‘enzymes’. Each different reaction occurring inside the living organism has a different enzyme attached to it.
There are 700 identified types of enzyme. Enzymes are another form of catalyst. They are classified into many broad categories, such as hydrolytic, oxidizing, and reducing, depending on the type of reaction they control. Hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds trough reaction with water molecules. Oxidising enzymes, known as ‘oxidases’, accelerate oxidation reactions; reducing enzymes speed up reduction reactions, in which oxygen is removed. Many other enzymes catalyse other types of reactions.
Lock and key theory
- Enzymes are a form of catalysts. In fact they are the strongest form of catalyst.
Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the ‘active site’ (see diagram below) or the location on the enzyme where the substrate fails to bind if their shapes do not match exactly. This ensures that the enzyme doesn’t participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with the new substrate.
Industry.
Catalysts are important to chemical manufactures, because they allow more product to be made in shorter time. They also don’t get ‘used up’, so they don’t constantly need to be replaced, they only have to be cleaned. This is because dirt build up will affect the performance.
Collision theory.
The collision theory is: There is a greater chance of reaction if the hydrogen peroxide has more catalyst to collide with. The bigger the catalyst = the bigger the rate of reaction or, the stronger the solution= the greater rate of reaction. This theory would alter slightly with different variables. I will show a diagram of the collision theory with the (concentration of H202) variable.
Variable 1
Concentration of the H2O2 (Hydrogen peroxide).
The two top diagrams a magnified version of the experiment but using a different variable (concentration of the H2O2). The second diagram is a greater magnified version of the top two diagrams. What you can see is the reaction happening between the catalyst and the hydrogen peroxide. This is the collision theory. The substrate (H202) is reacting with the active site (Catalyst).
Obtaining evidence.
Safety
- All the safety procedures I will use for the obtaining evidence are in the planning section.
Observations.
The equipment was set up as in the diagram in the planning section.
We completed the first rotation of experiments and found a problem with are equipment. We found that the syringe was sticking, which means that the oxygen would struggle to push the weight of the glass plunger. Which in turn means that are results would not be accurate as there was an opposing force. My partner and I decided tat we shall have to repeat the whole rotation, which we did. These are the results we found after repeatin the experiment.
Results
Table 1 Volume of Gas (Oxygen) Collected in a Syringe from various sized Potato’s reacting with Hydrogen Peroxide (Units cm3)
Analysing my evidence.
We found that the bigger the length of potato, the more gas is produced. This is because there was a bigger surface area in contact with the hydrogen peroxide in turn producing more oxygen, because the hydrogen peroxide has a bigger area to react with.
I will now produce a graph of my results.
Conclusion
We found that the bigger the surface area of the potato, the more oxygen was produced. The 5 cm length of potato reacted with the hydrogen peroxide to produce 25 cm3 of oxygen over a period of ten minutes, while the 3 cm length of potato produced 20 cm3 of oxygen in the same amount of time, and the 1 cm length of potato produced 11.5 cm3 of oxygen again in the same amount of time. This is shown by the downward trend of oxygen produced. This is shown in the graph. The change in the volume of oxygen was very steady throughout the experiment, about 2 cm3 per minute. This means that the only thing affecting the rate of reaction is the length of potato, because the amount of hydrogen peroxide hasn’t changed nor has the equipment, and the timing of the results has not changed either, meaning that the only possible reason for the amount of oxygen
to decrease is the length of the catalyst (potato).
Rate of reaction.
The change in time compared with the rate of reaction in the experiment was very high with the larger lengths of potato, (5 and 4 cm) and rather smaller with the smaller pieces of potato, (2 and 3 cm). Overall there was a difference of 16 cm3, between the largest length, (5cm) and the smallest length (1 cm). The change in the volume of oxygen was very steady throughout the experiment, about 2 cm3 per minute. This means that the only thing affecting the rate of reaction is the length of potato, because the amount of hydrogen peroxide hasn’t changed nor has the equipment and the timing of the results have not changed either, meaning that the only possible reason for the amount of oxygen
to decrease is the length of the catalyst (potato).
Was my prediction correct?
My prediction was accurate. I found that the larger the surface area of the potato, the more oxygen produced. Just like I stated in my prediction. So the longer the potato the more gas will be produced.
To see if my prediction was truly accurate I could of chosen another variable, i.e different shape maybe square or rectangular or maybe change the solution of the Hydrogen Peroxide. This would of answered my hypothesis that ‘the larger the surface area the more oxygen will be produced’. A square has a larger surface area than a cylinder, so more oxygen should be produced. Although the mass would not be the same, so this would not be a fare test. I would have to compare the two sets of results by mass instead of length. I would keep my plan exactly the same and I would of used exactly the same equipment as my original experiment. I would of also record my results for longer (around 15 minutes, instead of 10). If I did this (record the oxygen every minute for 15 minutes instead of 10), my results would have been more accurate, I would have been able to check that my prediction about the rate of reaction was correct. If the rate of reaction would stay the same all the way through the experiment, to improve this experiment even further I would record my results for as long as possible. This would put pay to my prediction that (the rate of reaction will rise smoothly all the way through the experiment).
Evaluating
Method
I set up the apparatus as shown on the fist page (planning section) of the investigation).
I then cut the potato into the desired length (5,4,3,2 or 1 cm). Then I placed the potato into the test tube and filled the test tube with 6 cm3 of hydrogen peroxide and placed the delivery tube over the test tube quickly so that no gas escaped. As soon as I put the delivery tube over the top of the test tube I started the stopwatch. I recorded the amount of oxygen which had entered the gas syringe every 1 minute. I repeated this method for every length of potato twice. Still using the same amount of hydrogen peroxide (6 cm3).
Accuracy
But the results I recorded were wrong. The gas syringe was sticking which slowed the progress of the gas down because the pressure had to build to a greater PSI because it had to lift the plunger as well. So we repeated the whole rotation again. After repeating the rotation, we looked at the set of results, fortunately they were accurate, the amount oxygen collected was very similar each time we repeated each length, the experiment ( each minute there was either little or no difference between set of results one or results two). I should of left the experiment longer to make sure that my results were even all the time, not just in the early stages of the experiment. If I would of left the experiment longer my results would have been more accurate.
I could of made my experiment more accurate by making my measurments better. I cut the potato next to ruler and marked the length with my finger. My finger could of moved slightly and I could of cut the potato in the wrong place. I could of also improved the accuracy by repeating the readings twice to make sure that I did not read them wrong the first place.
Further Work
To investigate further into the investigation, I would choose exactly the same variable. But I would change my equipment. This would prove weather my results were completely accurate. If they weren’t I would completely re- do my investigation with the new equipment and then compare the two sets of results. If the results were similar, I would know that my results were correct, and I used the most effective way of collecting oxygen from the catalyst reacting with hydrogen peroxide.
