In this laboratory I will add the same amounts of yeast and water to different amounts of sugar in water bottles and cap them with a testing tube to see how much carbon dioxide gas is produced. The more the fermentation, the more the carbon dioxide will be produced.
Work cited:
Time Requirements
This lab will require three, days to complete.
Selecting variables
Independent variables: amount of sugar
Dependent variables: amount of CO2 produced
Controlled variables
Amount of yeast and water, the time for fermentation is the same – three days, the amount of both distilled and normal water.
Material
- 5g dry yeast
- 10g sugar
- distilled water (room temperature, If the water is too hot (above 37°C), the yeast will die)
- water
- three 500ml beakers
- three 80ml test tubes
- three 500ml flasks
- 3-finger clamps
- Ring stand
- 3 rubber stoppers
- Pencil
- scale
Procedure
I make sure I will follow normal safety procedure during this lab
Each beaker is filled with 400ml of water.
Each flask is labeled: A, B, C
I put the certain amount of water, yeast and sugar into each flask as stated in the chart below:
Allow the yeast suspension to incubate for 5 minutes, with occasional swirling.
Each flask is stoppered with a 1-hole rubber stopper containing a short tube that is attached to a long piece of tubing; the end of this tubing outside of the flask is placed under water in a 250mL beaker. The yeast in this flask will use up the oxygen inside the flask and will ferment sugar to produce carbon dioxide. The CO2 will displace the remaining air. This flask will not contain oxygen after the first hour or two of the experiment. Shake up the culture in the flask to mix the yeast cells evenly. This is important in order to get consistent results.
Each test tube is filled up with tap water and fixed in a finger clamp on the ring stand up side down the bottom side is dipped into water in a beaker.
Each beaker is labeled by the same letter as on the flask that is connected to by tubing.
When the laboratory is set the time and the amount of water in testing tube is written down. Time is written down again at 12:00 and 15:00.
The second day data is written down three times during the day: 8:00, 12:00, 15:00 o’clock and the following third days in the morning at 8:00 only.
Finally, I cleaned up work area. Wash and dry the equipment and return all equipment to its proper place.
Error reduction
I made sure that the amount of yeast used in each fermentation flask was the same (because I used a scale). I tried to reduce air us much as possible by rubber stopper.
Method of Collection
Procedure is proper and goes in order I stated above.
Data
Flask A – Day 1
Flask A – Day 2
Flask A – Day 3
Flask A
The amount of carbon dioxide produced in flask A, with one gram of sugar is watched and written down in the charts above the final amount after 47.5 hours is 20ml of CO2.
Flask B – Day 1
Flask B – Day 2
Flask B – Day 3
Flask B
The amount of carbon dioxide produced in flask B, with three grams of sugar is watched and written down in the charts above the final amount after 47.5 hours is 75ml of CO2.
Flask C – Day 1
Flask C – Day 2
Flask C – Day 3
Flask C
The amount of carbon dioxide produced in flask B, with three grams of sugar is watched and written down in the charts above the final amount after 47.5 hours is 75ml of CO2.
Total amounts of CO2 produced
How variables are controlled
To ensure this is a fair test all the variables except for the concentration of sugar must be kept the same for each of the flasks. Variables that must not be altered include: Temperature, place.
These variables were kept constant
- Temperature of experiment: room temperature
- The amount of yeast: 0.5g
- The amount of distilled water in flasks: 200ml
- The amount of water in beakers: 400ml
Measurement problems
It is impossible to precisely measure out the amounts of water just by an eye, even though I tried to measure the amount looking at the angle of 90 degrees. Other measurement problems were taken care of because I used the scale to weight the amounts of sugar and yeast.
Reducing of errors
I tried to reduce all air errors by tightening the robber stopper, which should have taken care of the lack of air in the experiment.
Qualitative observations
Conclusion and Evaluations
Hypothesis
If we limit the oxygen that is available for yeast reproduction and increase the amount of sugar the yeast can react with, we expect the yeast will use the sugar for energy and reproduction.
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Conclusion
Looking at my background knowledge and experiments using yeast and different amounts of sugar I can explain my results and conclude that I can see that my prediction stated above was correct according to the results I have measured. The higher the concentration of sugar was the more carbon dioxide was produced. We can see the results on the data table above. My results are in line with those I predicted.
Evaluating
Weaknesses
The Procedure states that the flasks were stopper by the rubber stopper, which could not be tight enough. Each day was slightly different temperature in the room which might have affected the yeast mixture. All measurements were done as accurately as rationally possible. I could have measured the amount of CO2 produced more often, which would have brought more accurate results, but because the procedure was not repeated, the possible errors were not learnt. Besides that there was the chance that sugar was not dissolved completely
Limitations
The worst limitation was the problem of lack of time therefore I could not repeat the laboratory process. Besides that supplies were limited therefore I could not use more flasks and beakers to expand my experiment.
Improving
Ways of improvement
The procedure of this experiment could be improved, although the results do give adequate results. Improvements would simply remove certain errors, and improve the accuracy of results: A better overall result would be obtained by repeating the experiment more times. But because the purpose was to show the effect, which I successfully managed to achieve – the result was according to my background information I believe that repetition of the experiment would show slightly different values but the overall result which in this case is the most important would be the same. I should ask another person for help during the preparation time so all testing tubes are set at the same time and not one after another. In order to show better results I could have done one experiment of aerobic respiration and compare the difference.
Another idea that may be worth investigating would be the effect of water temperature. So perhaps by increasing the temperature of the solution that the yeast is in, we would see less oxygen in the water at the end of the experiment because more sugar would be in solution and therefore more accessible to the yeast for use.
Related to weakness/limitations
Using more different concentrations of sugar would have produced a better looking data.
