-Knife
Method
I will carry out my experiment by following these stages:
-I will collect and set up apparatus as shown above
-Use the borer, then cut the potato into smaller pieces.
- Weigh 3 grams of this
-Collect 15ml of hydrogen peroxide
-Set up as shown in apparatus
-Time the experiment for one minute
-When time has reached measure the amount of water left in the measuring cylinder
-Do this for each temperature.
Control of Variables
The independent variable will be the temperature. My dependant variable will be the oxygen. My controlled variable will be the amount of hydrogen peroxide and the amount of water, and potatoes. Therefore, my results will be fair and reliable.
Safety
To be safe I am going to wear goggles when handling chemicals. I will be careful when handling objects that are hot. I will wash my hands after handling hydrogen peroxide, as it is a corrosive and irritant. I will be careful when using the knife, as it is very sharp. Laboratory rules must be taken into account
Fair test
The factors which I would keep the same, is the mass of hydrogen peroxide, potatoes and the water. This is because; the experiment will not be reliable as the results will differ each time. This would not help me to conclude my experiment. I will chop the potatoes into smaller pieces because by the surface will be increased giving a greater area of collisions to take place and so causing an increase in the rate of reaction.
Measurements to Be Made
Readings
My results shall be taken after one minute of the experiment. I will use temperatures 0°c, 20°c, 40°c , 60°c and 80°c, I have gone up in 20°c because it not time consuming yet its accurate, although by going up 10°c, it would be more accurate. The range was chosen from research done which showed 0°c - 80°c is reliable. I will repeat my experiment, to make it more accurate and reliable. My overall results should be averaged so that it should be more accurate.
Prediction
I predict that the higher the temperature, the faster the time of catalyse to react. However, when the temperature reaches it optimum level it will start to slow down.
This is how I think my graph will look like:
At low temperature, the enzyme does not have enough energy to meet many substrate molecules, so the reaction is slowed.
At the optimum temperature, the enzyme is most efficient.
This is between 40°c -60°c
At higher temperature, the structure of the enzyme is broken down. The enzyme cannot be used again
The graph shows that when the rate of the enzyme activity reaches its optimum level its starts to decrease, this is because the enzyme denatures. This information was found from
Explanation
This is because; increasing the temperature makes the particles move faster. This leads to more collisions. Also the particles have more kinetic energy, so more collisions will lead to reaction. Catalyse works only under particular conditions. It works best at 37°c. At higher temperatures the protein structure is permanently changed (denatures): it no longer decomposes hydrogen peroxide.
O OBTAINING RESULTS
Table of Results
First results
Second results
Average of all results
A ANALYSIS
Conclusion
The graph shows that as the temperature increases, so does the rate of reaction. At 60°c, the graph reaches its optimum level, meaning that this is its peak. After this, the rate of reaction starts to fall rapidly, although at 70°c, it does not completely denature. This is due to the fact that the particles are still transferring energy. The particles are moving slower than how they were during the peak, 60°c, these particles are colliding and the collisions are still likely to lead to a reaction.
The graph looks like this because a rise in temperature speeds up the chemical reaction and a fall in temperature slows them down, the particles are moving faster and have more effective collisions, when the optimum temperature is reached there are less effective collisions, and enzymes change shape meaning that they can not work anymore.
From my prediction, the graph shows that I was correct, which is that; the higher the temperature, the faster the time of catalyse to react. However, when the temperature reaches it optimum level it will start to slow down. Also the optimum level predicted was correct.
E Evaluation
Procedures
Problems I had during the experiment were that it was hard to measure the temperature at the exact time needed to, which was after one minute. At first I was supposed to measure 20°c of water, but, by the time the apparatus had been set, this temperature at fallen, so we had to use 70°c instead, this did not alter the experiment or the results.
Data
My plan worked well for my experiment, because it gave me an idea of how my results will turn out like. It made it easier for me to obtain my results, and because the plan was detailed and precise, I was not confused on what to do; therefore my results were more reliable.
The scatter of my graph is strong; this made the results more accurate because there is a noticeable trend, which proves my prediction.
On my graph there is an anomalous result at 20°c, if I had more time I would have repeated the experiment to make the result more reliable. Factors which may have caused this could be that, like the wind form the open windows, the temperature of the boiled water may not be the same readings at the start of the experiment, also the iced water may not be exactly at 0°c, ad the readings collected may not have been at the correct time which is exactly 60 seconds.
I repeated my results, and averaged this out to get an accurate and reliable result as possible. I approximated my results to one decimal place, therefore I think that my results are reliable. The range used was a wide range which made it even more reliable.
Further Work
Changes to my experiment which may have helped me get better results will be to go up in 10°c, this is because the range will be closer making the results more accurate and reliable. Any other alternative experiment I would do to help me investigate the problem is to compare with potatoes and liver, rather than just potatoes, this is because both of these things contain catalyst for this reaction, and comparing both substances would make my experiment more reliable. Extending the range of my experiment would not help me obtain more reliable results because I think that the range is a good range to have as it is not too small or too big. Although using 10°c would be time consuming, but the results will be more accurate.
