I think that as the time increased the rate of reaction decreased because as the hydrogen peroxide reacted with the catalase, the hydrogen peroxide decomposed so there were less hydrogen peroxide molecules and so there were less collisions with the catalase and so less ‘lock and key’ mechanisms taking place. Therefore the rate of reaction decreased as time went on. That is why less bubbles were produced each minute.
The fact that my graph of total number of bubbles against surface area of the potato gives a slight curve means that there will be a certain surface area of the potato where no more bubbles can be produced in the five minutes seeing as there will be so much catalase involved in the reaction that it will decompose all of the hydrogen peroxide before the five minutes have gone by. Eventually, no matter what surface area of potato is used, considering it is not a ridiculously small surface area, there will always be the same number of bubbles produced by the reaction seeing as the catalase will never run out and it will therefore decompose all of the hydrogen peroxide, the only difference being that with potatoes with smaller surface areas the rate of reaction will be much slower than that of potatoes with larger surface areas.
My graph of time against number of bubbles per minute also gave me curves which tells me that after a certain time no bubbles will be produced anymore because all of the hydrogen peroxide will have been decomposed so there will be no more reactions. I think that the larger the length and surface area of the potato, the faster its reaction would get to the point where no more bubbles would be produced seeing as there would be more catalase molecules involved in the reaction so there will be more collisions with the hydrogen peroxide molecules and therefore the ‘lock and key’ mechanisms would take place faster. So the hydrogen peroxide would decompose faster and therefore reach the time when all of the hydrogen peroxide has decomposed before a potato with a smaller length and surface area.
I think that my results and my reasoning for them would be true in all situations because from my results it is obvious that the larger the surface area of the potato the faster the rate of reaction and therefore when you increase the surface area the rate of reaction will also increase. Also, seeing as the hydrogen peroxide decomposes, there will be less and less of it until it has all been decomposed, so there will obviously be less reactions taking place as time goes on and therefore less bubbles being produced until no more are produced.
In the reasoning I gave for my results I said that the hydrogen peroxide would decompose instead of the catalase being used up because the catalase is a catalyst and will therefore stay the same throughout and be the same when the reaction has finished. No matter what amount or concentration of hydrogen peroxide would be used or what surface area of potato, the catalase would always remain the same throughout the experiment and would be unchanged at the end of it.
From my experiment I can say that I have found out the following things:
- The enzyme catalase makes hydrogen peroxide decompose into water and oxygen faster than it would on its own.
- The larger the surface area of the catalase, the faster the hydrogen peroxide decomposes, so more oxygen is produced in a certain amount of time.
- The longer the experiment goes on for, the hydrogen peroxide decomposes slower, so the production of oxygen starts slowing down.
- No matter what the surface area of the catalase, the same amount of oxygen will always be produced, considering that the amount of hydrogen peroxide is kept constant, just over a different amount of time.
