Name: Da Eun Kim

Partners: Charles and Eileen

Date of experiment: Oct 20th, 2010

Yeast Experiment

Aim: To find how much gas is produced when the amount of sugar changes.

Hypothesis: My hypothesis is that more sugar we put, more gas will be produced because sugar is the source of food for the yeast so the more sugar that the yeast has, the more energy will be produced and the gas will be produced more.

Variables:

Input variable: Amount of sugar

Firstly, we will start the experiment with 4 grams of sugar and I will increase the amount by 1.5 gram (4g, 5.5g, and 7g) for every experiment. I will measure the amount of sugar by using electronic scale.

Output variable: Carbon dioxide

I will measure the gas using gas collection tube in ml and see how much carbon dioxide produced by yeast.

Control variables:

Control variable 1: Amount of water

Firstly I will measure the amount of water using measuring cylinder. Amount of water will be 100ml. Then we will put it in conical flask.

Control variable 2: Amount of yeast

Amount of yeast will be 4 grams.

Control variable 3: Type of sugar

We will use castor sugar to do this experiment.

Materials:

• 100ml measuring cylinder

• 100ml conical flask

• Electronic Scale

• Stopper

• Rubber tube

• Gas collection tube

• Yeast

• Sugar

• Distilled water

Diagram:

Method:

1. Set up equipment as shown in Diagram 1

2. Measure out 4 grams of yeast.

3. Add yeast to conical flask.

4. Measure out 100ml of water.

5. Add water to the conical flask that with yeast in it.

6. Measure out 4 grams of castor sugar.

7. Add sugar to conical flask with the yeast and water.

8. Stir thoroughly.

9. Wait 10 minutes.

10. Check amount of gas produced.

11. Record data.

12. Repeat steps 2-11 two times accepts with the amount of sugar add increasing by

1.5 gram (5.5 grams, 7 grams) with each successive experiment.

Data Table:

First First First Second Second Second Average Average AverageAmount of Sugar (grams)

4.0 5.5 7.0 4.0 5.5 7.0 4.0 5.5 7.0

Amount of CO2 produced (ml)

84 39 26 41 43 50 62.5 44 38

On first experiment, when we put 4 grams of sugar in the conical flask, 84 ml of carbon dioxide was produced. When we put 5.5 grams of sugar in the conical flask, 39 ml of CO2 was produced. When we put 7 grams of sugar in the conical flask, 26 ml of carbon dioxide was produced.

On second experiment, when we put 4 grams of sugar in the conical flask, 41 ml of carbon dioxide was produced. When we put 5.5 grams of sugar in the conical flask, 43

ml of carbon dioxide was produced. When we put 7 grams of sugar in the conical flask, 50 ml of carbon dioxide was produced.

The averages of these experiments was that 62.5 ml of carbon dioxide was produced for 4 grams of sugar, 44 ml of carbon dioxide was produced for 5.5 grams of sugar and 38 ml of carbon dioxide was produced for 7 grams of sugar.

Graph:

Conclusion:

From this experiment, I couldn't see any pattern or relationship when I added more sugar in conical beaker. Our group started the experiment using 4 grams of sugar and 2 grams of yeast. After we put them in conical flask with the 100ml water, we waited for 10 minutes. After 10 minutes, the amount of carbon dioxide was produced only 2 cm so we asked Mr. Covington that it is too slow then he said change the amount of yeast to 4 grams so we started again and waited. Then there was a big change in the experiment. 22 ml of carbon dioxide was produced. And we started the experiment with 5.5 grams of sugar and 4 grams of yeast. After 5 minutes, there’s no change so we did it again but there's no changes either. We decided that this experiment was not reliable and it was little error on it so we determined that meet at lunchtime and do it again.

In lunchtime, we started our experiment using 4 grams of sugar and 4 grams of yeast and we put the stopper to conical flask and just waited. After 10 minutes, we can see that 84 ml of carbon dioxide was produced. Then we increased the 1.5 grams of sugar and did the experiment. Then only 39 ml of CO2 was produced. I wondered why the amount of gas that was produced was different and we did experiment using 7 grams of sugar and 4 grams of yeast. Then only 26 ml of gas was produced so I decided that increase of amount of sugar couldn’t make any changes and we started our second

experiment. The experiment with 4 grams of sugar's result was that 41 ml of carbon dioxide was produced. And then the experiment with 5.5 grams of sugar's result was that 50 ml of carbon dioxide was produced. Lastly the experiment with 7 grams of sugar's result was that 62.5 ml of carbon dioxide was produced. On second experiments, the amount of gas was produced was increasing but the first experiment was not so I decided that there was no pattern and relationship.

My hypothesis was not correct because my hypothesis is that more sugar we put, more gas will be produced because the sugar is the main food of yeasts. However, when we put more sugar in conical flask, gas wasn't produced more and the first experiment's result was that the amounts of gas were reducing.

I think my data was reliable because we did many experiments. Our group tried a lot and we spent much times doing experiments of them. The data was that we decided after careful consideration so it is very reliable.

Evaluation:

I think my method wasn't reliable because there were some errors on my method. The first error was that when the stopper was put on the cylinder the air pressure moved the gas collection tube out. This would cause the CO2 collected to be higher. This probably has a small effect because it happened all the time. Another error was that when we put the yeast, sugar and water in conical flask, the flask is too small so the mixture was coming through rubber tube. This would cause the carbon dioxide collected to be higher, too. This will affect to our experiment only a bit because this situation can occur other groups’ experiments. The last error was that when we finished the experiment, we washed it for another experiment and we couldn’t wipe the water inside the gas collection tube so we just used it. This would cause the carbon dioxide collected to be lower and this will affect small effect because other group also couldn’t wipe the inside of gas collection tube.

To improve my experiment, we should record the amount of cylinder moves and subtracts it, from the total value. This is for the first error of my method. Other improvements that I need in this experiment is that we should use bigger conical flask next time or we can reduce the amount of yeast, sugar and water we put. Last improvement is that we can use long wiper to wipe the inside of gas collection tube. Actually using another gas collection tube is the best way to improve our experiment but there were no more gas collection tube so we can just find the long wiper and wipe it.