Controls
Temperature: This must be controlled to make the experiment a fair test. If it is not controlled it will change the reaction rate in the experiment. In order to control this we must do all experiments at room temperature making sure not to put in the path of an open window or heated radiator, open window causing a drop in temperature effecting the enzyme activity, radiator increasing the temperature again effecting the enzyme activity.
pH value: In our experiment we are testing how the different concentrations would change the reaction rate, so will not be using pH.
Amount of hydrogen peroxide: we will be using 10ml of hydrogen peroxide, which must be measure using a pipette and a measuring cylinder to make sure accurate amount is measured and also that its the same during each experiment so to get accurate results to be able to compare the results of each molar.
Concentration: concentration is the factor that we will be changing in this experiment. But to keep it a fair test we will be using molars, which will be able to give us the results that we are trying to accomplish. We will also be using the same amount of each concentration.
Catalyse: the catalyst we are using in this experiment is yeast. In order to perform a fair test the yeast must be measure accurately so not to give uneven amount in each experiment but the same to have accurate results to compare.
Apparatus list
- Conical flask
- Test tubes
- Bung & gas tube
- Test tube rack
- Gas syringe
- Safety goggles
- Pipette
- Stop clock
- Yeast (catalyse)
- Hydrogen peroxide
- Buffer solutions of different pH
- Clamp
- Clamp stand
- Boss
- Mass balancer
Safety
To keep safe in the experiment we all wore safety goggles to protect our eyes when handling the acid. Also when measuring out the acid use a pipette so not to spill the acid and if any was spelt clear it up immediately. If we spill any acid over our hands, wash them immediately. If any equipment gets broken tell a teacher straight away in case of any accidence that might happen.
Diagram
Method
Firstly collect all the equipment and set it up. Attach he clamp and boss to the clamp stand, carefully placing the gas syringe into the clamp. Then using a beaker, carefully measure out 1g of Yeast. To make sure it is exact place the beaker on the scales making sure it has been reset to weigh 0g before weighing out the yeast. This way you will only be measuring out the yeast not the beaker Then collect 10ml of the first concentration of hydrogen peroxide, using a pipette and a and a measure cylinder to make sure the measurement is correct. When it is all prepared connect the bung and tube to the gas syringe ready to attach it to the flask. Firstly add the Hydrogen Peroxide to the cronical flask and then the yeast, and immediately place the bung over the flask and start the stopwatch ready to record the amount of oxygen produced at every 10second intervals, having your results table at the ready. We repeated this method with the 5 different concentrations:
Making sure to keep the same quantities of each the hydrogen peroxide and the yeast, insuring the experiment is fair. Make repeats of each concentration at least twice to get accurate results to be able to compare with.
Preliminary Work
Firstly we gathered up all the equipment and set it up. Then we used a bora to cut out circles of potato measured exactly to 1g on a mass balancer. We added this to the test tube and then added the buffer solution, which was ph 7. We then added the hydrogen peroxide to the test tube instantly adding the bung to the top on the test tube to collect the oxygen in the measuring cylinder. We measured the mount of oxygen every 10 seconds after that we read off the measuring cylinder and took down the results and we did this twice for a repeat result to make it more accurate and we did this for yeast and liver.
When carrying out our preliminary work we found out that there wasn’t a lot of catalase in the potato so the amount of oxygen produced was not a lot and the gas syringe measures volumes off gas in larger units so it becomes less accurate.
Results table
Oxygen produced measured in cm3
Averages in red
Conclusion
I conclude from the results we obtained from the experiments that as the concentration increases, the reaction rate increases proportionately as collisions between enzyme molecules and reactants are more often. This shows that higher concentrations help enzymes to work faster before the concentration gets to high and oxygen stops being produced. From my results I can see that the amount of oxygen produced at 1 molar is slightly more than the amount of oxygen produced at 1.5 molars, this could show that the enzyme (yeast) was working better at 1 molar then it was at 1.5 molars. So you can see a raise and fall in the amount of oxygen produced showing that in my experiment that the enzyme worked better at 1 molar. In my prediction I stated that the higher the concentration the more oxygen would be produced at faster rate, in my experiment this is true up until 1.5molars where is slightly less, this could have been because on an inaccurate experiment, or that the experiment was just slowing down. But overall the enzyme worked better at higher concentrations then it did lower.
Evaluation
From this experiment, I can draw many positives and negatives. We had a fairly wide range of concentration values to choose from which meant that results would be quite good in that we have not restricted ourselves to just 2 or 3 different values. However it would have been better to have used another higher concentration, to see if the results collected at 1.5 molars were inaccurate, or the amount of oxygen being produced did start to lower. Also, we had the chance to repeat our results, which meant that we had a clearer idea of how accurate or reliable our results were, it would have been better thought to repeat more than twice to give more accurate averages, and to have a more accurate idea on if our results collected were right. I would have preferred to have repeated the experiment 3 times at least. Fortunately, on this occasion, our repeat results proved to be the same or similar to that of the original experiment. This means that the probability of these results being accurate is much greater.
There is some thing I would have liked to change in this experiment, but it was not possible. The equipment we used was, I believe, good enough for experiment, although I think it could have better, so could have had more accurate results. One problem we had was that we were unable to clean and dry the equipment sufficiently enough, and so this meant that it was not quite a fair test as it would have slightly diluted the hydrogen peroxide and it would not have given is the more accurate results, if we could dry it. This could have been overcome by using separate boiling tubes for each experiment. Also we found that the yeast stuck to the side when we first put it in, which meant that it did, sometimes, not touch the hydrogen peroxide at the bottom of the test tube, as quickly this again affecting the efficiency of our results. Another problem we had was getting the bung on top of the boiling tube in time to record our results; this meant we missed the first few second of the reaction. The experiment could have also been better if we measure the amount of oxygen on a greater scale, so that the results could have been more accurate.
