Equipment must also be rinsed thoroughly, as someone could unknowingly pick up a beaker covered with H2O2. Rinsing out excess substrate and enzyme could also increase the validity/reliability of the results.
Suggested Data Analysis:
The type of graph used will be a scatter graph with axes labelled as follows:
Results may be analysed by looking at mean, mode and median to look for trends in the graph, for example, looking to see if as the concentration doubles, the distance travelled does the same.
A scatter graph was chosen, as a trend line can be added, which can help identify anomalous results.
Modifications:
During the first run of the experiment, it was noticed that the Catalase was not running as quickly at 100% (20 volume) as it did in the trial runs (on a previous day).
Therefore, running the experiment by measuring the distance travelled in a set time of 10 seconds became unpractical, as the distances travelled in this time were too small.
So, a new set time of one minute was added before this limitation presented a problem.
Results:
The results were collected in the order suggested in the plan (100% descending to 20%, then 20% ascending to 100%) to eliminate the affects of room temperature change when an average was taken.
As two results were taken for each concentration an average was calculated for the distance travelled, this will be analysed.
Data Analysis:
From the graphs it is possible to see the trend that, as predicted, as the concentration of substrate increases, the rate of reaction increases.
The gradient for the graph of the first run of results is: 0.189
The gradient for the graph of the second run is: 0.198
The gradient of the graph showing the average distance is: 0.192
This shows a close similarity between the results.
It was expected that as the concentration double, the rate of reaction would double also. On the graph showing the averaged results, this is approximately true for the double of 20% to 40%, but as show by the exponential trend line, as the concentration increases, the rate of reaction escalates.
When 40% is doubled to 80% there is a 257.14% increase.
When the trend line approximation for 50% is double to 100% there is an approximate increase of 271.20%.
This shows that as the concentration of substrate is increased, there is more likeliness that the H2O2 will contact a Catalase enzyme because there are molecules of H2O2 to collide, so they are moving at greater rates, so the rate of reaction escalates with the concentration of substrate.
Evaluation:
The equipment used had high limitations, which could have affected the results.
Firstly, when the mixture is made in the syringe, the reaction begins and water and oxygen are produced immediately, due to the syringe being difficult to attach to the glass tube, oxygen was lost in the process of attaching the syringe. This was unavoidable because the rubber connector had to be tight to prevent further gas loss. Repeats were important here so that excess gas loss could be identified. An anomaly that relates to this limitation is in the 40% concentration test in the second run. It is possible that it may have taken longer here to attach the syringe.
Due to uncontrollable gas escape the bubble would have gone less far if it took longer to attach the syringe and further if it took less time.
In most cases the values for the first run and the second run do not vary by more than 0.2 around the average, so there is an uncertainty value on the distance travelled of ± 0.2cm, as shown by the error bars in the graph to show average.
As all measurements were made by the guide on the syringe, there could have been an effect on the concentrations, if the syringe was not marked accurately there would be an inaccuracy in concentrations, therefore there is an uncertainty value of ± 0.1cm^3. This is shown as a horizontal error bar on the graph to show average.
