Variables:
The variables that I will keep constant and the reasons are:
- The equipment-I will use the same equipment so if there is something wrong with it then all the results will be affected instead of just one that could make my whole experiment wrong.
- The potato-I will use the same potato because different potatoes have different amounts of Catalase in. If I change the potato then all the results will have no meaning because of the different amounts of Catalase. I will also always crush the potato up so there is a large surface area meaning the rate of reaction will be quicker than with an uncrushed potato.
- The hydrogen peroxide-I will keep the hydrogen at the same concentration. If I did not then the Catalase in the potato will react quicker or slower depending on the concentration.
- The amount-I will not change the amount of Hydrogen Peroxide or Potato because it will change the rate of reaction.
- The time-I will keep the amount of time that the potato and Hydrogen Peroxide are heated for and the amount of time that they have to react the same at 1 minute so the results are all valid and there will be some consistency in them.
The things that I will measure are:
- The potato-I will measure out the amount of potato each time so the experiment is always under my control.
- The Hydrogen Peroxide-I will measure the amount of Hydrogen Peroxide so I can keep the reactions controlled.
- The time-I will measure the time that I allow the reactions to take place so I can record it.
- The water-I will measure the amount of water in the beaker so the potato and the Hydrogen Peroxide are both heated the amount I want them to be.
- The temperature-I will measure the temperature so I can control the experiment and get the reactions what I want.
- The gas-I will measure the amount of gas coming off the reaction so I can record it for my results.
The Variables that I will change are:
- The temperature-I will change the temperature so that I can answer the question that I set myself to find out, ‘what temperature does Catalase work best at?
Safety: In my experiment I will be as safe as is possible so I do not injure or in any way harm any other person or myself. To make the experiment safe I will:
- I wore glasses and an apron so I did not get any chemicals or hot water into my eyes or onto my clothes.
- When I was not using the Bunsen burner I made sure it was on the yellow flame so people could see that it was on and going.
- I made sure that when I was boiling the water I was standing next to it so I could warn people that the water was hot and to tell them to stay a safe distance away.
- When using the scalpel to cut the potato I always made sure that people knew in case I slipped and hurt them.
- I cut the potato slowly and carefully so I did not cut myself with the scalpel.
- I made sure that if I came into contact with the Hydrogen Peroxide I washed my hands immediately so I did not burn my hands because of the concentration.
Apparatus: For my experiment I had to use certain pieces of apparatus. These apparatus are:
Bunsen Burner,
Tripod,
Heatproof mat,
Gauze,
Scalpel,
Thermometer,
3 x Boiling tube,
Beaker,
Test tube holder,
Tile,
Conical flask,
Bung,
Scales,
Syringe,
Potato,
Hydrogen Peroxide,
Pestel,
Mortar.
Observations: I intend to observe and record in my experiment. I wish to observe and record how much gas is coming off the Potato and Hydrogen Peroxide at the different temperatures. The temperatures are:
10, 20, 30, 40, 50, 60 and 70Oc.
I intend to record these three times at each temperature.
Method: As plan.
Results:
A table to show how much oxygen was given off during each reaction.
Discussion: My graph shows that there is a definite pattern in the amount of oxygen given off in relation to the temperature. The graphs shows an increase up to 40OC then a drop back down to zero.
I have found out that the temperature that Catalase works at depends on the temperature of the substance and the Catalase itself. The Catalase also starts to denature between 40 and 50Oc and works best at around 40 degrees Celsius. I can also establish from my graph and my results that different parts of a potato has different amounts of Catalase inside. I have found this out because not all of the results are exactly the same.
My prediction was partly right because I predicted that the Catalase would work best at around 40 degrees Celsius because the bodies’ average temperature is 37 degrees. But I also said in my prediction that the Catalase would start to denature at 50 degrees, which is partly right, but really it started to denature in between 40 and 50 degrees.
My results agree with my background information saying that Catalase is in every living thing. I have proved this by showing that it is in potato. It also functioned as an organic catalyst because it made the reaction happen without any other chemical.
Evaluation: The procedure that I used was, I believe, quite good. There is a few parts of my plan which now I have carried out I could change to make the experiment more accurate. These changes would be:
- When crushing the potato some of the juices were lost. To stop this I should have not crushed it but cut it into the same size cubes so it is fair and it will give more reliable results.
- When I was heating the potato and the Catalase I put them into the water bath when it was at the right temperature. Because the boiling tubes were not heated at the same time it made the temperature rise or fall. This was the same with all the results but each time it changed a different amount. To stop this from happening I should have heated the boiling tubes and the water at the same time.
- When I took the boiling tubes out of the water and tried to put the potato into the conical flask sometimes it would not all come out. I overcame this problem after a little think by pouring some hydrogen peroxide out of the boiling tubes and into the boiling tube with the potato in and then pouring it into the flask. This washed the potato out but sometimes I had to do this a couple of times meaning the results were not as accurate as they could have been.
- I noticed halfway through my experiments that my bung did not fit into my conical flask properly and it was leaking some of the gas. If I repeated my experiment I would use a different conical flask and bung so none of the gas would be lost.
- When I measured the Hydrogen Peroxide I measured it in the conical flask. Now I look at this it was not a very good idea because I may not have washed it out properly meaning there might have been some potato inside the flask making the Hydrogen Peroxide react before I have mixed it with the desired pieces of potato.
During my experiment and as my results show I did have a few odd results. This may be due to many factors as I have pointed out in the above statements.
When reading the syringe I did read it to the best of my ability but the syringes do not have a very good scale for pinpoint accuracy. They only measure every 1 cm3. When I was measuring the Hydrogen Peroxide I used a conical flask, which is not very accurate because it only goes up in 50 cm3. Even though I used 100 cm3 it was not a very accurate way of measuring the chemical. I did however measure the potato correctly and accurately by using electric scales.
A clear conclusion can be made even though I have some results that are out of place. That is that between 0-40 degrees the rate of reaction is increasing, at 40 degrees it reaches its ultimate rate of reaction then it starts to denature and the rate of reaction falls until it reaches zero.
I could extend my experiment by heating only the potato or the Hydrogen Peroxide so I can find out whether the temperature of the substance being broken down changes the rate of reaction. Also I would like to find out what has the most Catalase in out of liver, potato and bread like some of my other colleagues in my class.
