I will change the number of potato cubes used so I will increase the total surface area of potato used in the experiment as well as there being more catalyse for the Hydrogen Peroxide to react with. The cubes I will are 1cm x 1cm x 1cm. This gives a total Surface area of 6cm². However since one of the sides is touching the bottom of the glass the total Surface Area is actually 5cm².
I will now explain why I am keeping some aspects of my experiment constant.
Temperature:
When you increase the temperature you increase the kinetic energy of the particles. This results in the Hydrogen Peroxide having more successful collisions with the catalyse enzyme, found in the potatoes, so more oxygen is given off in the experiment.
Concentration of Hydrogen Peroxide:
When you make the Hydrogen Peroxide more concentrated you increase the amount of reactant present. This results in more successful collisions with the catalyse enzyme in the potatoes and more oxygen is released.
Time the Experiments Last:
If the experiments lasted for longer there is more time for a larger amount of successful collisions to take place so more oxygen would be released.
Surface Area of the Individual Potatoes:
When you increase the Surface Area you increase the amount of catalyse exposed to the Hydrogen Peroxide. This means that more successful collisions will take place since there is more catalyse to react with and more oxygen will be produced.
Volume of Hydrogen Peroxide:
If you increase the volume of Hydrogen Peroxide used in the experiment you increase the amount of reactant particles. Since there are more reactant particles when the volume has increased you will get more successful collisions with the catalyse enzyme in the potatoes so more oxygen is given off.
For my experiment I will need the following apparatus:
- Bung
- Delivery Tube
- Thistle Tube
- Conical Flask
- Two 50ml Measuring Cylinders
- Tile
- Potatoes
- Knife
- Hydrogen Peroxide
- Water Tub
- Safety Glasses
- Clamp & Clamp Stand
- Stopwatch
- Ruler
- Water
Prediction
I predict that in my experiment as I double the total surface area of the potatoes the amount of oxygen will double as well. This is because if I increase the amount of potato it should increase the amount of catalyse. When I increase the total surface area of potato in the experiment more catalyse will be present to react with the Hydrogen Peroxide so more Oxygen will be produced.
Before I began to collect our data I did preliminary work to decide what our range of results should be. I first decided to test what volume of Hydrogen Peroxide I should use. These are the results for 50cm³ of Hydrogen Peroxide for 5 minutes.
Since I am using a 50ml-measuring cylinder using 50cm³ of Hydrogen Peroxide is unacceptable since I will not be able to collect results. I then decided to try 30cm³ and this generated better results so I decided to use 30cm³ in my actual experiment. So I collected more preliminary results with 30cm³ of Hydrogen Peroxide instead of 50cm³.
Now I have results that can be used but now they are too close together. This means they may not be reliable. So to make my diverse I will change the number of potatoes to 4(20cm²),8(40cm²), 12(60cm²), 16(80cm²) and 20(100cm²)
So my experiment now looks like this.
- It will last for 5 minutes each time.
- The volume of Hydrogen Peroxide will always be 30cm³
- The numbers of potatoes used will be 4,8,12,16,20.
Results:
Graph: PTO
Conclusion:
From my results I can see the following trend. In my experiment as I increased the total Surface Area, by increasing the number of potatoes, the volume of Oxygen increased too. This is because as I increased the total Surface Area the amount of catalyse exposed to the Hydrogen Peroxide also increased. Since there was more catalyse present there were more chances for successful collisions to take place and more Oxygen was produced. However in my prediction I stated that I thought the amount of Oxygen would double as the Surface Area doubled. From looking at my results you can see that this is not entirely true. Between 20cm³ to 40cm³ my results did almost double from 8cm² to 15cm². However later on in both experiments this did not happen. Between 80cm³ and 100cm³ the results were 39cm² to 51cm². As you can see here it has not doubled. My prediction was wrong since the oxygen given off did not double as Surface Area did but is right eventually because it did increase.
Evaluation:
I am pleased with the results recorded because they all fit in the pattern of increasing volume when Surface Area increases. Since my results are very similar in both experiments I believe my results are reliable. I collected the bubbles in a measuring cylinder and did not count them this makes my results more accurate since the bubbles could have different volumes of air in them. There are no anomalous results in my experiments and both sets match up proving to me again that my results are reliable. My method of getting the results could use some work though.
Since one side of each potato cube was always touching the glass not all the possible catalyse was available for the Hydrogen Peroxide to react with. This could be fixed by some how suspending the potatoes in the Hydrogen Peroxide perhaps using string attached to the bung. Another problem I encountered was that sometimes the delivery tube would pop out from the measuring cylinder halfway through the experiment and some gas could obviously escaped and not been recorded. The only way I can think of to remedy this problem would to have me constantly hold the tube in the measuring cylinder. Since my investigation spanned several lessons, and because I used large amounts, I used more than one potato. This could be fixed if I found a large enough potato or changed the number of potatoes I used to a smaller amount. A problem I experienced with the larger numbers of potatoes was that they clumped at the bottom of the conical flask. Getting a conical flask with a larger diameter could easily solve this. . To see if there is another relationship, if I had had the time, I would like to have done some intermediate values from my original ones. For example 6,10,14,18 to see if there was a relationship even though there wasn’t a relationship in the other ones.