Diagram:
Procedure:
- A solution of 50g of catalase per 1000ml of water was prepared.
- The Erlenmeyer flask was placed inside a water bath (filled with tap water), and the apparatus shown in the diagram was prepared.
- Water peroxide was poured into the flask, and then it was tapped with a cork.
- Ice cubes were added to the water in the bowl, containing the Erlenmeyer flask, and its temperature cooled down (to 5ºC)
- The catalase was injected with the syringe into the flask, too, and the oxygen started to appear (in the measuring cylinder).
- The results were recorded every 20 seconds for the first 3 minutes, and then each minute, until a period of 5 minutes showed no change in the oxygen collected.
- The syringe wasn’t removed until the end; otherwise it would let some of the oxygen escape.
Data collection:
The following data was recorded, where the Tº of the tap water remained constant at 5ºC.
Table 1.1: Results obtained by cooling the reaction of H2O2.
Data processing:
Graph 1.1: Results from the experiment plotted as Time vs. O2 produced
This graph shows how at a low temperature, rate is slow due to the poor energy it provides. If this graph could continue (which wasn’t possible due to the maximum measurement of the measuring cylinder (100ml)), it would show how the reaction comes to an end and the line stabilizes horizontally.
It is correct to assume that the highest rate at the beginning of the experiment is due to the absence of substrate for the enzyme to work with. This means, that at the very first contact it has with the water peroxide, all enzymes start working at the same time as they are not affected by the concentration of the substrate since there is enough substrate for all the enzymes to react with. But as time passes, there is less substrate to react with and so the rate slows down.
The cause of its instability is that at time 140s and 180s the reaction was shaken, so because of the energy given, the reaction fastened again. But the resultant O2 will always be the same, no matter the tº. The only variable it changes is the rate at which equilibrium is reached.
Now, we will plot the results of the group 2, which was left to react without changing its temperature, that is, at normal temperature:
Table 1.2: Shows results of group 2, who did the same experiment without changing the temperature.
Graph 1.2: Shows results of group 2.
The 100ml of O2 were obtained quickly, in approximately 60 seconds. This is because as temperature is higher, molecules have more energy and move faster. As this happens, molecules are more likely to encounter with each other and react. Also, the necessary energy to react is acquired quicker.
Now we will compare both results:
Graph 1.3: Shows both group’s results compared to each other.
Here we clearly see that the rate of reaction of group 2 was higher than group 1’s. Finally, both lines would get to an end together, because as explained before, the yield of production will be the same, but not the rate at which it is obtained.
Conclusion: We found out experimentally that the reaction with the cow liver catalase was faster at a higher temperature, and that there was enzyme activity in both experiments, by watching how O2 was released in the measuring cylinder.
Errors:
- The flask was shaken only after 140s since the beginning of the experiment.
- There might have been some air in the tube generating the oxygen before the experiment started.
- The error for the time is quite large. This is due to the period between a person reading (or even re-reading) the values while the other one is recording the data.
- Some air might have escaped back to the syringe.
- The temperature inside the reaction was not actually measured, but the tap water outside it.
- When putting the cylinder upside-down, some air remained in it and so made it difficult to measure well the O2 released.
Improvements:
- Shake the flask constantly to allow complete mixture of both reactants.
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Re-do the experiment until there is no air at all in the measuring cylinder.
- Be permanently watching the thermometer until the college tells you to tell him the data.