Science Coursework: Fermentation
How does the sugar level affect the rate of Fermentation?
Aim:
The aim of this experiment is to find out whether the rate of Fermentation is affected by the amount of sugar.
Apparatus:
The equipment used is:
- Bunsen burner.
- Heat proof mat.
- Boiling tube.
- Delivery tube.
- Water bath.
- Water flask.
- Thermometer.
- Stop watch.
- Yeast and Sugar.
- Digital weighing scale.
- Water.
- Measuring cylinder.
- Test tube.
- Tripod
Method:
- Fill the water bath with water (not to the maximum).
- Fill the boiling tube with 10ml of water.
- Add 2g of yeast to the water and add sugar (1g, 2g, …up to 5g).
- Put the Boiling tube into the water bath.
- Connect a delivery tube onto the boiling tube.
- Fill a test tube with a reasonable amount of water.
- Place the other end of the delivery tube into the test tube.
- Put the Bunsen burner on a heatproof mat.
- Place the water bath on the tripod and heat the water.
- Measure the temperature of the water (in the water bath) with the thermometer. Stop the heating until it reaches 40°.
- Start the stop watch after the first bubble has appeared in the test tube.
- Count the bubbles that appear in 1 minute then stop the stopwatch.
- Repeat the process but this time adding another gram of sugar until 5 grams.
- Then repeat the whole experiment again starting from 1g to ensure the reliability of the results obtained.
Ali Hammuda
Planning a fair test:
The factor chosen is the concentration of sugar solution, so the other factors are to be kept constant as control factors in order to make this investigation fair. Here are the control conditions and other procedures I must take. I should make sure that the test tubes are thoroughly washed each time I repeat the experiment. This is because remains of yeast or sugar could affect the results. I must use the stopwatch rather than counting or guessing the time so that I do not count the wrong number of bubbles. The yeast which I will use is to come from the same source so they are at the same age otherwise, bubbles might not appear as frequently as they should because of difference in freshness of yeast. The level of water in the boiling tube must always be exactly 10 ml otherwise; the concentration of the yeast and sugar mixture might increase of decrease depending on the amount of water added which will affect the number of bubbles. The mixture should be gently shaken to blend the solution and the culture together, as the culture tends to settle at the bottom over a certain time. The whole experiment should be repeated again to obtain a more accurate result and to calculate an average result. A thermometer must be always used when heating the mixture and is to be made sure that the temperature of the mixture in the boiling tube is at 40° so that there is enough energy and the enzymes do not denature and slow down the experiment. I must make sure that the Fermentation lock is not damaged so that it allows the escape of CO2 gas without the entry of oxygen, which could oxidize the ethanol produced. All these procedures must be taken into account in order to produce precise and reliable evidence. The variables that can be changed are the amount of yeast, amount of sugar and the temperature of each reaction. The only variable that will change is the amount of sugar as it goes up by 1 gram each time. The temperature shall remain at 40° degrees and the amount of yeast will always be 2g.
