Amount
Of
Oxygen
Time
I also, believe that the amount of oxygen will be directly proportional to the amount of potato. I believe this as the more potato added, the more active sites added. This means if you double the size of potato you double the amount of active sites so double the amount of oxygen will be given off at the end. However, I am aware that in our experiment we are not 100% how many enzymes are in the potato so we have to hope that it is the same.
Preliminary Work
Method: Put on goggles before handling any of the chemicals. You need to fill the ice cream tub up with water and fill the measuring cylinder up with water making sure that there is no air in the cylinder. The measuring cylinder must then remain in the water with the tube in the end. During the experiment you must check that the tube does not come out from the cylinder, as the oxygen would escape. Then 30cm of Hydrogen peroxide must be measured out and then added to the boiling tube. The potato needs to be pushed through the cutter so that all the chips are the same depth and width. They must then be cut to the correct length. Starting with 0.5 cm and going to 3cm. This must be done on a tile. The chip then needs to be added and the stop clock needs to start strait away. The bung must be pushed into the boiling tube with the tube in the top of the bung. Every 30 seconds read off the measuring cylinder how much oxygen is in it. Keep taking the readings every 30 seconds for 5 minutes. It must always be carried out in a neutral pH and it must be done at room temperature.
This method needs to be repeated for all the size chips ranging from 0.5cm up to 3 cm increasing 0.5cm every time. The experiment needs to be carried out 3 times for each size chip so that an average can be obtained to try and cancel out any anomalous results. The method must be kept exactly the same making sure that the same amount of Hydrogen peroxide is used every time (30ml)
Before carrying out the actual experiment I tested how the temperature of the Hydrogen peroxide affected the experiment. I decided to simply measure the froth with a ruler, as I just needed an indication of which temperature works best. I used the same size piece of potato, 2.5cm long and I used the same amount of hydrogen peroxide.
Measure of froth in cm
From doing this experiment I have decided to carry out the experiment at room temperature because it gave easy readable results that were the most accurate as there was the smallest difference between the 3 attempts. It also will make the experiment a lot easier to collect the oxygen. This is due to the fact that you don't have to worry about water baths.
I also investigated the pH to see how this would affect the enzyme so that I could find out which condition would be best suited for my experiment. Again, I measured the size of the froth and kept the same size potato and the same amount of Hydrogen Peroxide.
From doing this experiment I have decided to uses a pH that is neutral because it is not too high that all the oxygen given off will not fit in the cylinder but the oxygen given off is not to small the change will be nearly impossible to see. I feel that a neutral pH will give me a clear set of results.
From doing these preliminary tests I am now able to write my method using the information gathered.
For this experiment I am going to take the readings every 30 seconds for 5 minuets and record my results in a chart. I am going to do each size of potato three times and then obtain an average. The size of my potato is going to range from 0.5 cm to 3 cm so that I can get a clear idea of how size affects the reaction.
Equipment
The equipment you need for this experiment is:
1 ice cream tub
2 measuring cylinders
Boiling tube rack
Boiling tube
Bung
Tube
Stop clock
Pipette
Tile
Potato
Potato cutter
Knife
Ruler
Goggles
Method
First, the equipment needs to be gathered and set up as shown below.
Put on goggles before handling any of the chemicals. You need to fill the ice cream tub up with water and fill the measuring cylinder up with water making sure that there is no air in the cylinder. The measuring cylinder must then remain in the water with the tube in the end. During the experiment you must check that the tube does not come out from the cylinder, as the oxygen would escape. Then 30cm of Hydrogen peroxide must be measured out and then added to the boiling tube. The potato needs to be pushed through the cutter so that all the chips are the same depth and width. They must then be cut to the correct length. Starting with 0.5 cm and going to 3cm. This must be done on a tile. The chip then needs to be added and the stop clock needs to start strait away. The bung must be pushed into the boiling tube with the tube in the top of the bung. Every 30 seconds read off the measuring cylinder how much oxygen is in it. Keep taking the readings every 30 seconds for 5 minutes. It must always be carried out in a neutral pH and it must be done at room temperature.
This method needs to be repeated for all the size chips ranging from 0.5cm up to 3 cm increasing 0.5cm every time. The experiment needs to be carried out 3 times for each size chip so that an average can be obtained to try and cancel out any anomalous results. The method must be kept exactly the same making sure that the same amount of Hydrogen peroxide is used every time (30ml)
Fair Test
To make this experiment fair all the factors must stay the same apart from the amount of enzyme. This means that the experiment must be done in the same room on the same day so that there is not a large change in temperature. It must also be done in a neutral solution so that this factor does not affect the results obtained. The same potato must be used as different amounts of potato may contain different amounts of catalase so the amount of active sites will vary affecting the amount of oxygen given off. For this experiment to be fair all these factors must stay the same so that the results obtained show how the amount of catalase affects the reaction rather than the other factors also affecting the results. In case all the factors are not correct I have decided to take three readings for each size of potato chip so that any anomalous results will be cancelled out.
Safety
In this experiment goggles must be worn so that no Hydrogen Peroxide gets in our eyes. Care must be taken when using the Hydrogen peroxide and it must be washed off skin straight away. If irritation continues then the teacher should be informed straight away.
Care must also be taken when cutting the potato. Bags and coats should be hung up so that no one falls over.
Results
Below are the results gathered the experiment
Results for 0.5 cm of potato
Attempts 1 2 3
Results for1cm of potato
Attempts 1 2 3
.
Results for 1.5cm of Potato
Attempts 1 2 3
Results for 2 cm of potato
Attempts 1 2 3
Results from 2.5cm of potato
Attempts 1 2 3
Results for 3cm of potato
Analysis
From looking at the graphs showing the amount of oxygen given off against time it is clear that there is an increase in the gradient of the graphs as the size of the potato increases. This means that generally the larger the amount of potato the more amount of oxygen given off. It is also very clear from my results that the increase of oxygen given off was a lot larger between 2.5 and 3.0 cm of potato than any other size of potato. The lines of best fit appear to be very straight but they do not always go through the origon. This is because Hydrogen Peroxide can start to break down at room temeprature so it wil go through a point above (0,0).
If you take the rate of the 0.5cm reaction and the 3cm reaction you see that it has increased.
0.5 cm of potato the rate is gradient= 2 =0.5
4
3 cm of potato the rate is gradient=3 =0.6
5
Conclusion
As the size of potato increases the amount of oxygen given off increases. This is due to the factt that as the potato size increase more catalase is being added so the amount of enzymes present is higher. This means that ther are more active sites there for the reactions to take place in. The rate of the reaction also increase as the size of the potato does as there are more active sites the amount of oxygen is given off at a higher rate due to the extra active sites that allow the reactions to take place quicker. This means that prediction is correct as the amount of oxygen increases as the potato size does.
The reaction is:
Catalase + Hydrogen Peroxide water and Oxygen
My results show that the amount of enzymes are not directly proportional to the size of the potato. However this should not have been the case and I feel that only a few of my results suggests that my prediction that they were directly proportional is correct. Howerev I know from my studies that the end results all should have been directly proportional.
From the results it is clear how quickly the catalase can break down the harmful Hydrogen Peroxide in our body to safe substances such as water and oxygen.
Evaluation
I feel that my method was safe and gave me accurate results. I feel that the method allowed me to get results that can support my conclusion. I believr that the reason why my results were not directly proportional is that I had to use a different potato half way through the test. This means that the amount of enzymes it contained could have been slightly different.
The anamonous results where my 3cm of potato ones. I believe that this again could be down to the change in potato or the bung may not have been in fully so some of the oxygen may have escaped and not have been measured. The tube may also have been blocked so the oxygen may never got through to be measured.
I feel the way I measured the height of the froth was very accurate. After trying in my peliminary test by measuring it with a ruler I feel the method I used gave much more precise readings.
If im was to re do this experiment I would make sure that I used the same potato and the same enzyme solution every time as this may have lead to the anomolus results.
If I want to do futher work I could try measuring the gas given off by using a gas suringe. This would work by having the test tube set up the same as befor but this time having the tube leading into a suringe so as the oxygen is forced out is pushes the suringe so that the reading can be taken.
This method would be a lot quicker and you don’t have to worry about the tube coming out from the bottom of the test tube. However the suringe would need to be very big on some of the larger pieces of potato.
The same experiment could be done using exactly the same method as I stated but by using different substances that catalase is present in.
