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Marley Emerich Grade 9 Biology/Chemistry Yeast ExperimentBeijing BISS International School School Code: 1123Wednesday, November 2, 2011
Name: Marley EmerichPartners: David Shong (De Wei)Date of experiment: Monday, October 17, 2011 Does the Amount of Yeast Affect the Amount of Carbon Dioxide Produced?Aim: The aim of the experiment is to investigate if the amount of yeast added affects theamount of carbon dioxide produced.Hypothesis I think that with the more yeast we put in, the more carbon dioxide it willproduce. Therefore, the amount and speed the tube is pushed out by the carbon dioxideshould increase as well. When yeast is mixed with sugar and water it creates a reaction.When all these chemicals react to each other, they produce carbon dioxide. If I put moreyeast into the mixture than before, the sugar will have more to react to. Therefore,creating even more carbon dioxide. More carbon dioxide should increase the pressure ontube more, therefore pushing it down faster.Variables: Independent variable: The variable that will be changed is the amount of yeast. It will be changed by each time measuring a different amount of yeast on the electronic scale and adding it.Dependent variable: The variable that will be measured is the amount the tube goesdown in 10 minutes. After 10 minutes, I will look at the scale on the side of the cylinderand see how much it went down. Control variables:Control variable #1: TimeI will keep it the same by: Using a stopwatch to make sure each trial lasts 10 minutes.Control variable #2: Amount of WaterI will keep it the same by: Making sure I fill the measuring cylinder up to 100 mL eachtime.Control variable #3: Amount of SugarI will keep it the same by: By using the electronic scale to measure 5g of sugar each time.
Control variable #4: Cylinder and Conical FlaskI will keep these the same by: Using the same sized cylinders and flasks every time.Materials: • Gas Collection Tube • Measuring Cylinder using 100 mL of water (to get an accurate reading of the amount of water for the conical flask.) • Stopwatch (for timing the amount of time each trial is, 10 minutes). • Rubber tube with cork (that transfers the carbon dioxide from conical flask to gas collection tube). • Conical flask (where the Xg yeast and 5g sugar mix is in). • 45g of sugar • 36g of yeast • A small bowl to place the yeast and sugar in for weighing. • An electronic scale for weighing the sugar and yeast. • Glass rod to mix the yeast and sugar with. • Pen, paper, and notebook to record my data with.Diagram:
Method: 1. Set up equipment as shown in Diagram 1 2. Measure 5g of sugar, 2g of yeast on the electronic scale. 3. Fill up the measuring cylinder to 100 mL of 40˚ water. 4. Transfer this water into the conical flask with yeast and sugar ready. 5. Pour the yeast and sugar in the conical flask and mix with glass rod. 6. Seal it with the rubber tube and cork connected to the gas collection tube. 7. Wait for 10 minutes and stop the timer. 8. Record how much the CO2 has pushed the tube out in cm³. 9. Collect data. 10. Repeat Steps 1-9 except increase the amount of yeast by 2g each time. 11. Repeat the whole experiment two more times.Results: Amount of CO₂ Produced With Different Amounts of YeastAmount of Trial 1 – Trial 2 – Trial 3 – Average -yeast (cm³) (cm³) (cm³) (cm³)(grams) 2 16 25 23 21 4 33 40 44 39 6 87 62 68 72
Conclusion: My hypothesis was correct. The hypothesis was that when I increased the amountof yeast in the water and sugar mixture, it would produce more carbon dioxide, thereforeincreasing the amount of pressure on the gas collection tube. This pushes it out more andmore depending on the amount of carbon dioxide produced. The data shows that witheach added two grams of yeast, the amount of carbon dioxide produced increasedimmensely. As you can see in my graph, in each trial the pattern of the carbon dioxideincreasing was consistent. The trend continues on and my data supports my hypothesis,even though there were some minor errors. My data was mostly reliable because therewere some sections that had some mistakes in them. Like in the first trial using 6 gramsof yeast I measured 87 cm³ when the 10 minutes was up. While in the second and thirdtrial I got two smaller but closer numbers, 62 and 68 cm³. The same thing happened inthe 1st trial using 2 grams of yeast instead. I got 16 cm³ which was low compared thesecond and third trial 25 and 23 cm³ difference. The same happened with the 4 grams ofsugar on the 1st trial. The amount moved was 33 cm³ but the second and third trial was 40and 44 cm³. Something either went wrong in the first trial or in the second and third trial.But even though the data may have been a bit unreliable at first, the pattern continued to
increase steadily over the next two trails getting the averages of 21, 39, and 72 cm³.Something that was hard to measure was the amount of yeast and sugar. I put both ofthese on an electronic scale to measure the right amounts but sometimes the scale wouldbe a little off or the paper the yeast or sugar were sitting on would add to the weight,giving me measurements that were a little off.Evaluation:Weaknesses in my Specific Effect on my Improvements IMethod Data Could Make on my MethodGas Collection Tube being The tube being moist I didn’t realize how a littlemoist – caused it to stick to the dampness could affect aIn the first trial, I had taken inside glass, enabling the whole trial. Next time nota tube from right next to thegas to push it down only will I make sure it’s asink and dried it. I thought properly. Once I realized completely dry tube, but Iit was dry enough but it what was happening, I will not shake or touchwasn’t. shook the conical flask a anything in the process little and it pushed way far because it could push the up to 87 cm³, which wasn’t tube to a point it shouldn’t very accurate. be.Weighing the yeast and On both days, our scale was Next time, I really shouldsugar properly - a bit broken. It didn’t sit make sure they myIn order to get a consistent right and would move every electronic scale is notand accurate amount I time I touched it, causing broken so I can get the sameneeded to weight the the measurements to amount of yeast and sugaramount of sugar and yeast change. I also had to place each time. Also, I shouldeach time on the electronic the yeast and sugar on a not use a paper to placescale. piece of paper, which also yeast and sugar in because weighed some, causing the it changes the results quite a measurements to all be a bit bit. off and possibly different each time.The temperature. The I performed this experiment Improvements I could maketemperature in the room and on two different days. The based on these problems areof other elements (maybe first time I did it, the one, next time measuringthe water) affected some of temperature in the room and the temperature of the roommy results. of some of the materials each time so I can consider was different. The next day that in my data or trying to the two trials I did were reduce or increase the very close most likely temperature in the room. Or because they were on the doing the experiment the same day. Also, sometimes same day. Also, next time I when I took out the water use heated water I should which should have been at pour it and time how long it 40˚ I left it sitting for longer is sitting by itself and how times then others when long it sits with the yeast preparing which could have and sugar so I can consider had an affect on each result. that in my results.