Although temperature cannot be controlled I tried to keep the conditions the same so effect is limited. I did this by working in the same area, working at room temperature.
Safety Precautions: During the experiment the safety precautions I took are wearing safety goggles, also standing well enough back. Also I made sure I did not touch anything harmful or toxic such as hydrogen peroxide. Also all equipment (especially acid bottles) was kept on safety mats.
PREDICTIONS
The theory is that RATE OF OXYGEN PRODUCTION is proportional to SURFACE AREA.
This means as surface area increases so does rate of oxygen production.
Therefore as surface area doubles rate of oxygen production will double.
Theory
The rate of oxygen production depends on the number of successful collisions hydrogen peroxide particles on the potato. The more successful collisions the more oxygen produced. If surface area is increased there is more area for the hydrogen peroxide particles to hit the potato.
This means as one increases the other will increase.
At a higher surface area exposed there is more surface of the potato that can be attacked by the acid, which means more particles will attack the potato meaning there will be more successful collisions on the potato increasing the rate of oxygen production.
A lower amount exposed means there is less area hit meaning less successful collisions which means the rate of oxygen production is lower.
If you double the surface area at ends, there are more successful collisions
METHOD
First the apparatus was collected and set up as shown in the diagram; also a potato, cork borer and scalpel need to be collected. 12 potato cylinders from the middle of the potato are cut using the cork borer to get out the potato cylinder a smaller cork borer is inserted to push out the potato cylinder. The diameter of the potato cylinders is about 6mm. Then lay all the cylinders and cut them to the same length, the length of the shortest cylinder. The length should be no smaller then 40mm. Now 2 cylinders are cut in half to give two pieces, 2 cylinders are cut into 4 equal pieces; another 2 are cut into 8 equal pieces. Another 2 are cut into 16 pieces with another 2 into 32 pieces, 2 are left uncut. A scalpel is used to cut the potato cylinders. To make sure all pieces are equal measure with ruler. Measure 4cm of hydrogen peroxide accurately into the graduated test tube. After this is completed the stopwatch is checked to see if the timer is reset. Once this is done and the equipment is in place it is ready for the experiment. The potato cylinder is put into the acid and the timer is started, every 15 seconds the amount of oxygen produced is measured using the graduated test tube and is recorded. This is done for two minutes every 15 seconds then the timer is stopped and all results are recorded. Once the experiment is completed and the graduated test tube is washed and dried and the experiment is repeated for each different surface area twice.
DIAGRAM
CONCLUSION
Statement: ‘As surface area increases, the rate of oxygen production increases.’
Theory: This is because there are is more area of potato as the number of ends increases therefore the hydrogen peroxide particles have a larger area to hit therefore there will be more frequent successful collisions increasing the rate of oxygen production.
Other factors can affect the rate of oxygen production such as temperature as enzymes are sensitive to temperature and 1 C makes a difference. Also the substrate concentration must be kept the same as a higher concentration contains more particles, enzyme concentration also affects the rate as there are more collisions if there are more enzyme particles. Also the amount of active sites will affect the result because if there are none free the rate will not increase.
If you double the surface area at ends, there are more successful collisions
My results show his pattern as the amount of surface area increases so does the amount of O produced. At 2 ends of potato the rate is 2.5 and at 4 ends it is 3.88 this increase fits the pattern perfectly as the surface area of the potato does not double but does increase like the result. This paatern is similarly shown at 8 and 16 ends, at 8 ends the rate is 4.72 and at 16 ends it is 6.11, which is a proportionate increase to the increase in surface area.
The theory states that if you if you double the surface area, you double the rate of oxygen production this result is own between the 8 ends and 32 ends as the 32 ends is double the surface area of the 8 ends the results show the rate is 4.72 and 9.16 which is roughly double. This shows the result were quite accurate as they support the scientific theory and prediction. This allows you to compare results accurately and they can support an evaluation.
EVALUATION
The data collected from the experiment is accurate this is shown by the steady proportionate increase of the average rate of production as the amount of surface area increases. The graph of the average rates show some points are slightly outside the line of best fit but they are accurate enough to support a conclusion. The reasons for the slightly inaccurate results are the limitation on high quality equipment.
I did get one set of anomalous results with the experiment with a whole potato. This result was clearly wrong and I re did the experiment to gain the correct result. Reasons for this could be too strong acid, incorrect amount of potato or incorrect measurement. The evidence can support a conclusion because the results are correct and follow a proportionate increase. The anomalous result can be rejected therefore it does not become part of the data allowing the rest of the data to be accurate.
Error of graph plots = 0.5 x 10 -2
X 100 =12.5%
4.0 x 10 –2
Accuracy of Graph = diff X (1000)
Avg. value
PROCEDURAL ERRORS
- Reaction time of hand-eye – error of 0.1s (automatic timer by laser)
- Not all the bits of potato are in the acid when timer is started – error 5% (automatic stirrer)
- The potato may have lost some of the catalyse (Use newly grown potato)
- Judging accurately the amount of O produced. (automatic detector)
- Temperature not always being the same (measure and control temperature)
INSTRUMENTAL ERRORS
- Measuring cylinder 7cm error in 0.5cm – 2% error
- Length of potato (4cm) error of 1mm – 2.5% error (metal ruler)
- Time over 10s error 0.1 – 1% error (automatic)
- Temperature 2 C, error due to it being not being able to be kept constant 5%
- Whether equipment is washed and dried properly – 2%
Total percentage of maximum possible errors is 17.5%
OTHER EXPERIMENTS
- More results at each surface area – to get a better average
- Use higher and lower lengths of potato see effect on rate.
- Use higher and lower concentrations (such as 0.1, 2.2, 5) – to see how concentration affects rate of oxygen production
- Use other enzymes such as lipase and protease
- More and less amount of acid
- At different temperatures
- Using catalysts
