Instead of using one of the above methods we decided to use the bubble counting method.
This method is the easiest and quickest for students to set up correctly. It was also the cheapest method. However it is not the most accurate of the methods but does give a reasonable idea of how the rate of reaction changes.
Hydrogen Peroxide (H2O2) solution is a clear, colourless, water-like in appearance biological toxin, and can be mixed with water in any proportion. At high concentrations, it has a slightly pungent or acidic odour.
H2O2 has a molecular weight of 34.02 and is non-flammable at any concentration.
These diagrams show how enzymes and substrates work together.
Increasing the surface area (in terms of the active sites available) is a main factor of our experiment. I will now explain how it will have an effect on the experiment.
A solid in a solution can only react when particles collide with the surface, the bigger the area of the solid surface, the more particles can collide with it per second,
and the faster the reaction rate is. You can increase the surface area of a solid by breaking it up into smaller pieces. A fine powder has the largest surface area and will have the fastest reaction rate.
Through this simple diagram you can see that as we decrease the size of each block we increase the surface area.
Apparatus
Scalpel knife, plugs of potato, stop clock, goggles, white tile, ruler, conical flask, delivery tube, hydrogen peroxide, beaker of water, measuring cylinder, tube rack, boiling tube.
Method
The plugs of potato were cut into 1cm lengths using the scalpel on the white tile. 15cm3 of hydrogen peroxide was measured in the cylinder. The beaker was filled with water and the end of the delivery tube is placed in it. The potato was then added to acid in the boiling tube and the end of the tube is corked up with the delivery tube. The gas bubbles which were released from the reaction were counted for 2 minutes. Each result was then recorded and repeated 3 times. Then the potato was split into 1/2's,1/4’s, 1/8’s and 1/16’s each one been performed 3 times.
Results
Conclusion
These results show us that as you cut a piece of potato into smaller pieces the rate of reaction increases, therefore increasing the amount of bubbles released. The theory studied helps us understand about how the rate of reaction has increased this is very obvious in the results obtained as there is a diagonal line pointing upwards showing an increase in the size.
Evaluation
The method we followed was a simple method which enabled us to follow closely and obtain some accurate results from the experiment. The very last result had to be obtained from another test as we ran out of time so had to borrow some one else’s results.
We don’t have too many anomalies but the ones we do have may have been caused by swapping to a new potato as it is a natural source and we can not choose how many enzymes it contains.
The procedure used was suitable for us but it could have been improved by organising the time available for us to do the experiment.
The evidence we obtained is quite reliable and is sufficient to support the conclusion put forward.
