Name: Da Eun KimPartners: Charles and EileenDate of experiment: Oct 20th, 2010 Yeast ExperimentAim: 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 producedbecause sugar is the source of food for the yeast so the more sugar that the yeast has, themore 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 theamount by 1.5 gram (4g, 5.5g, and 7g) for every experiment. I will measure the amountof sugar by using electronic scale. Output variable: Carbon dioxide I will measure the gas using gas collection tube in ml and see how much carbondioxide 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 waterDiagram: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 4.0 5.5 7.0 4.0 5.5 7.0 4.0 5.5 7.0Sugar(grams)Amount of 84 39 26 41 43 50 62.5 44 38CO2produced(ml) On first experiment, when we put 4 grams of sugar in the conical flask, 84 ml ofcarbon dioxide was produced. When we put 5.5 grams of sugar in the conical flask, 39 mlof CO2 was produced. When we put 7 grams of sugar in the conical flask, 26 ml ofcarbon dioxide was produced. On second experiment, when we put 4 grams of sugar in the conical flask, 41 mlof 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 wasproduced for 4 grams of sugar, 44 ml of carbon dioxide was produced for 5.5 grams ofsugar and 38 ml of carbon dioxide was produced for 7 grams of sugar.Graph:Conclusion: From this experiment, I couldnt see any pattern or relationship when I addedmore sugar in conical beaker. Our group started the experiment using 4 grams of sugarand 2 grams of yeast. After we put them in conical flask with the 100ml water, we waitedfor 10 minutes. After 10 minutes, the amount of carbon dioxide was produced only 2 cmso we asked Mr. Covington that it is too slow then he said change the amount of yeast to4 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 ofsugar and 4 grams of yeast. After 5 minutes, there’s no change so we did it again buttheres no changes either. We decided that this experiment was not reliable and it waslittle 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 ofyeast and we put the stopper to conical flask and just waited. After 10 minutes, we cansee that 84 ml of carbon dioxide was produced. Then we increased the 1.5 grams of sugarand did the experiment. Then only 39 ml of CO2 was produced. I wondered why theamount of gas that was produced was different and we did experiment using 7 grams ofsugar and 4 grams of yeast. Then only 26 ml of gas was produced so I decided thatincrease of amount of sugar couldn’t make any changes and we started our second
experiment. The experiment with 4 grams of sugars result was that 41 ml of carbondioxide was produced. And then the experiment with 5.5 grams of sugars result was that50 ml of carbon dioxide was produced. Lastly the experiment with 7 grams of sugarsresult was that 62.5 ml of carbon dioxide was produced. On second experiments, theamount of gas was produced was increasing but the first experiment was not so I decidedthat 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, whenwe put more sugar in conical flask, gas wasnt produced more and the first experimentsresult was that the amounts of gas were reducing. I think my data was reliable because we did many experiments. Our group tried alot and we spent much times doing experiments of them. The data was that we decidedafter careful consideration so it is very reliable.Evaluation: I think my method wasnt 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 movedthe gas collection tube out. This would cause the CO2 collected to be higher. Thisprobably has a small effect because it happened all the time. Another error was that whenwe put the yeast, sugar and water in conical flask, the flask is too small so the mixturewas coming through rubber tube. This would cause the carbon dioxide collected to behigher, too. This will affect to our experiment only a bit because this situation can occurother groups’ experiments. The last error was that when we finished the experiment, wewashed it for another experiment and we couldn’t wipe the water inside the gas collectiontube so we just used it. This would cause the carbon dioxide collected to be lower andthis will affect small effect because other group also couldn’t wipe the inside of gascollection tube. To improve my experiment, we should record the amount of cylinder moves andsubtracts it, from the total value. This is for the first error of my method. Otherimprovements that I need in this experiment is that we should use bigger conical flasknext time or we can reduce the amount of yeast, sugar and water we put. Lastimprovement 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 butthere were no more gas collection tube so we can just find the long wiper and wipe it.