Hydrogen Peroxide = 2H2O2
Hydrogen Peroxide + Catalase = Oxygen + Water
Apparatus:
Measuring cylinder To hold 100ml of water. This was thoroughly cleaned with tap water beforehand to ensure that the water was not contaminated with anything. This may have led to anomalous results in the long-term.
Clay Beehive To provide somewhere to connect the pipe from the mixture to the water. It also acted as a ledge to hold the measuring cylinder as it stood upside-down.
Tub To hold water and everything in place.
Stopclock To time experiment. I ensured that the experiment was timed as soon as it began because if it hadn't, then the results may have been inaccurate.
Water bath To heat chemicals.
Conical Flask To hold the yeast and hydrogen peroxide solution together once the experiment had begun. This needed to be cleaned using water to ensure that nothing would contaminate the solution.
Diagram:
Method:
I set up the experiment as shown above. I filled the tub full of water. I then placed the beehive in the water. Then I filled a measuring cylinder with exactly 100.0ml of water and placed it on the beehive in the water without letting any of the water in the measuring cylinder escape. I needed it to be exactly 100.0ml so that I could measure it exactly, from a starting point which is relatively easy to remember. After all, 100.0ml is a lot easier to remember than 87.3ml! The measuring cylinder was thoroughly cleaned to ensure as little impurities in the water as I could possibly control. Whilst this was being set up, I had already prepared 40.00ml of yeast and 20.00ml of hydrogen peroxide in separate boiling tubes. At this point, it was very important that I kept the two substances apart because if they had been mixed, they would have begun to react The boiling tubes were both cleaned to ensure the chemicals didn't react with anything, and were as "pure" as possible before the experiment began. When I was certain that it was all prepared, I poured both liquids into a conical flask and fixed on a bung with an attached tube. This operation needed to be practised before the experiment was done for real to ensure it was done as quickly as possible. After all, the hydrogen peroxide and yeast solution will have started reacting as soon as they came into contact. I connected the tube to the clay beehive and measuring cylinder, which were both already prepared in the water. From the very beginning, I started the stopclock timing and noted down how much oxygen had been reacted and had travelled down the pipe into the 100ml of water in the measuring cylinder. I noted down the volume of water that was left in the measuring cylinder after five minutes, taking a result every minute. I chose to take down the result for five minutes because any longer than that and there was none, or barely any water remaining in the measuring cylinder. This is because the yeast and the hydrogen peroxide would have finished reacting completely.
Variables:
Variable: The temperatures of the hydrogen peroxide and the yeast.
Controlled Variables:
Volume of water in the measuring cylinder: 100.0ml
Times: 0, 1, 2, 3, 4, 5 minutes
Types of liquid: Water, Hydrogen Peroxide, and Yeast solution
Volumes of substances: 40.00ml yeast, 20.00ml hydrogen peroxide
Room temperature: 25ºC approximately
Temperatures of mixture: 20.0?C, 30.0?C, 40.0?C, 50.0?C, and 60.0?C. These must be kept as exactly as possible as yeast is very receptive to changes in temperature.
If these variables were altered, it would not be fair test.
Results:
20.00 20.00 20.00 Avg 30.00 30.00 30.00 Avg
0 100.00 100.00 100.00 0 100.00 100.00 100.00
1 75.00 58.00 66.50 1 41.00 42.00 41.50
2 61.00 45.00 53.00 2 2.00 10.00 6.00
3 50.00 27.00 38.50 3 0.00 0.00 0.00
4 39.00 13.00 26.00 4 0.00 0.00 0.00
5 30.00 2.00 16.00 5 0.00 0.00 0.00
40.00 40.00 40.00 Avg 50.00 50.00 50.00 Avg
0 100.00 100.00 100.00 0 100.00 100.00 100.00
1 58.00 60.00 59.00 1 25.00 22.00 23.50
2 39.00 27.00 33.00 2 0.00 0.00 0.00
3 18.00 9.00 13.50 3 0.00 0.00 0.00
4 2.00 0.00 1.00 4 0.00 0.00 0.00
5 0.00 0.00 0.00 5 0.00 0.00 0.00
60.00 60.00 60.00 Avg
0 100.00 100.00 100.00
1 69.00 28.00 48.50
2 26.00 2.00 14.00
3 5.00 0.00 2.50
4 0.00 0.00 0.00
5 0.00 0.00 0.00
Graphs on following pages
Conclusion:
I conclude that my prediction was partly correct. I was correct by saying that the reaction would be quicker as the temperature was 30?, but it was slower at 40? and again quicker at 50?. This may be because the catalyst, in this case catalase worked best at that temperature, allowing for more successful collisions between the yeast and hydrogen peroxide molecules.. I cannot explain these results because I can guarantee that I made sure that it remained a fair test throughout the experiment. I didn´t alter any of the other variables. All the other results came out to be what I expected, with the reactions slower at 20? and 60?.
Evaluation:
I was a little surprised at some of the results, and if I were to do this experiment again, I would try to discover what it was that gave these findings. I would also do the experiments for every 5? instead of every 10?. I would also measure other variables, to ensure that there cannot be any more fluke results. I would conduct the experiment more times to get a more accurate average. Although I conducted the experiment as accurately as I could there were many sources of error in the method that I used. Firstly, some help from friends was required to begin the experiment and this lead to a small delay in starting the stopclock. I would have to find a way to be a little more accurate. This would ensure that my results were as accurate and as precise as I could possibly get them.
