Another theory that can explain why the larger surface makes a difference is called the ‘Collision’ theory, which is where the enzymes and substrates collide to give the enzyme to collide with substrate in the solution. Both these theories help explain why surface area makes a difference.
Apparatus.
This is how our experiment was set-up: -
These are the apparatus we used in the experiment: -
●500ml beaker,
●A burette,
●Size 5 potato cutter,
●A conical flask,
●A bung with a delivery tube attached,
●A stopwatch,
●A clamp stand,
●A scalpel.
Method.
In the experiment we carried out each test in the same way every time. This would ensure that our results were consistent and as accurate as possible.
These are the steps we took through each of the test: -
●First we filled up a burette completely with water.
●We then placed the end of the burette we filled with water into a beaker, which was
about just over quarter full, (we did this so that the water inside the burette would
not empty out).
●We placed 10cm³ of H2O2, (hydrogen peroxide), in a conical flask.
●We then cut the potato with a potato cutter then into the length that we wanted, this was
4cm.
●We then placed our potato cylinder into the conical flask containing the H2O2.
●We had to quickly put a bung onto the conical flask that had a delivery tube attached
to it.
●The delivery tube was then placed under the burette as quickly as we could do it.
●We then took readings every 30 seconds with a stopwatch and recorded them in
our notes. (We recorded up until 300 seconds/10 minutes).
●We did each surface area 3 times and took an average.
●We used the same method each time for all 4 of the surface areas.
Fair Test.
There would be no point in doing this experiment if we were not going to make it a fair test. By making it a fair test we could obtain results that we could rely on. To make it as fair as possible we made sure we did the following during the experiment: -
●We made sure we used the same sized potato so we had consistent readings and had no
anomalous results.
●We had to use the same size potato cutter every time so the potatoes had the same
diameter. We used a size 5 cutter to do this.
●Hydrogen peroxide measurements had to be the same otherwise there would be
anomalous results.
●We had to make sure that the potato was the same length every time, which was 4cm.
●The same concentration of H2O2 was also vital. This was 20% H2O2.
●We made sure we used the same member of our pair to do the same job all the way
through the experiment just to make sure we kept a consistency.
●We used the same apparatus all the way through the tests so there was no chance of
anything being different so our results were accurate.
Preliminary Work.
This is our preliminary work to test what size and width we wanted our potato cuttings.
Diameter of the potato cutter = 0.85cm, (Size 5).
Potato was 4cm long.
Room temperature = 34°C.
2cm of H2O – The reaction was too slow.
4cm of H2O – The reaction was still to slow.
10cm of H2O – Good speed of reaction, not to slow with full potato and not to fast with
diced potato.
Crushed potato – Unable to crush potato in experiment as results are too different, (not a
fair test).
To help with prediction: - Full potato + 1o cm of H2O reacts slower than diced potato +
10cm of H2O.
Surface Area Calculations.
Full = 11.9cm.
½’s = 13.6cm.
¼’s = 16cm.
⅛’s = 20.8 cm.
Safety.
In the experiment we were going to performed we had to make sure we performed it very carefully to make sure no one got hurt or we did not damage anything in the Biology lab. These are the following precautions we had to stick to so the experiment was safe.
●Wearing safety goggles is a must in this experiment because we are using hydrogen
peroxide, (H2O2).
●We had to place our bags on the sides of the classroom, our stools under the benches
and also hang our coats up so we prevented any of our classmates or any of the group
tripping over these items and causing any damage to the experiment or themselves.
●We had to set our experiment up in the middle of the desk so there was no risk of the
apparatus falling over the edges of the desk.
●We made sure there was an eye washer near our apparatus in case some of the hydrogen
peroxide did get into one of our eyes.
●We made sure we did not run in the classroom so there was a smaller chance of
us tripping or smashing something in the lab.
●We made sure that we carried the apparatus and chemicals carefully around the class
so it was not split over anyone in the class.
Results.
On the next page are the results that I collected from the investigation in table form. On the page after the table is a graph to show the results and the differences between the amount of surface area exposed to the H2O2.
Conclusion.
On my graph it is clear that the lines get steeper as the potato was cut up into smaller pieces and the surface area was increased. So the graph indicates that the more surface area there was the hydrogen peroxide particles would react more frequently with potato particles. With our first experiment there was the least amount of surface area meaning that the rate of reaction was at its slowest. My results came out as I expected and the prediction I made was correct.
Evaluation.
Throughout the whole experiment we worked well and most importantly we worked safely. We did our utmost to make all the tests in the experiment as fair as possible also. I do not think that there was very much more we could do to get even more accurate results. One suggestion we discussed was that maybe we could have improved or figured out a way to get every potato cutting the same length each and every time. We could have achieved this by making some kind of stencil that would be placed on the potato and would be 4cm long and it would allow us to cut the potato exactly the same length every time.
The experiment ended up the way that we expected because we obtained the results that I imagined we would obtain. Our results show that the greater the surface area of the potato pieces the quicker the reaction would take place. This is what was expected and is shown in our results, (the graph).
