I also found that my range of results should be from about 10ºC – 90ºC, because if you go lower than 10ºC that a reaction takes such a long time to occur that it is not worth including. Also when the results exceed 90ºC the enzymes in the yeast become denatured and do not work as they are expected to do. Thus, I am going to take the following temperatures to test at, 15ºC, 37ºC, 45ºC, 60ºC, and 90ºC.
I also found out that, the best way to do accurate repeats is to put the repeat test tube in with the first experiment, so that they both receive the same heat and equilibration times. Thus, Ensuring a fair experiment. Also for the control I will put it in with the other test tubes so that it also receives the same conditions that the other results will receive.
When the tin can has been heated it is inevitable that that the temperature of the can will drop and thus effect the experiment results. This is hard to combat without overheating the water and thus effecting the results too much. If the drop is very extreme (at higher temperatures) then I will try to heat the water back up to the required temperature using the Bunsen burner.
Factors to keep constant:
When I experiment I need to use the same concentration of yeast-glucose solution. This is so that the yeast does not produce too much or too little carbon dioxide compared with all the other results. So to make the experiment fair I must experiment with the same concentration of yeast-glucose solution in each different experiment.
I must also allow the same amount of time for equilibration each time I start a new experiment. I will do this so that the results are fair and the suspension gets a chance to become the same temperature as its experimental atmosphere no matter what temperature is used.
I will also put the same amount of suspension in each fermentation tube. I will do this so that, proportionally, the same amount of carbon dioxide is produced in each experiment. Thus, the experiment will be fair.
Key factors.
Temperature- the temperature affects the rate of the reaction. The higher the temperature the faster the reaction. Roughly, for every increase of 10ºC the rate approximately doubles.
Higher temperatures mean that the particles have more energy. This causes:
- The particles to move faster and collide more often. Thus, there is a faster reaction.
- More particles have enough energy, Activation energy, to break the bonds and allow a reaction to occur. This increases the reaction rate dramatically.
Temperature is an independent variable- something that I can change. Also the length of the gas bubble is dependent on the temperature that the suspension is being tested at.
The concentration of the yeast will be diluted by 50% so that the reaction, taking place in the yeast will be reduced and so we can analyse the reaction properly and at a slower rate. This affects the results, as the time taken for the experiment to be completed will be longer.
Also the first part of the reaction in the yeast will be aerobic, as there is a small bubble that appears in the top of the fermentation tube when it is inverted. However, after the oxygen has been used up only anaerobic respiration takes place. There is very minimal change in the results due to this.
Proposed results table and graph.
I will than use this results table for every experiment but change the temperature in the top row to the desired temperature.
For the control I will leave it running until the actual experiment has finished, thus, it will get the same time for equilibration and experimentation.