Name Date Lab Partners Yeasty Beasties Lab and Experimental Design Write-Up *this lab was adapted from the Yeasty-Beasties Lab at the following web address: http://www.sciencebuddies.org/science-fair-projects/project_ideas/microbio_p011.shtml#help Final Version by Lisa Seff 1/14 DRAFT COPY! Introduction Yeasts are micro-organisms that are more closely related to a mushroom (they are a singlecelled fungi) than to bacteria. Fungi are not green, do not have chlorophyll, and cannot undergo photosynthesis to make their own food. Instead, yeast must get their food from their surrounding environment. Yeasts use sugars (simple carbohydrates) and starches (complex carbohydrates) as food sources. Yeasts break down these sugar molecules to make energy and release carbon dioxide gas (CO 2 ) as a result. The carbon dioxide gas is what makes a slice of bread so soft and spongy. The pockets of gas are produced by yeast when the dough is allowed to rise before baking. This is the process of fermentation. Fermentation is also used to make beer, wine, and champagne. In this experiment you will grow yeast in different conditions to see which conditions will cause the yeast to be most active during fermentation. You will use balloons to trap the CO 2 gasses released by the yeast during fermentation. Then you will submerge the balloons under water and use water displacement to measure the amount of gas in each balloon. Which ph conditions will result in the formation of the most CO 2 gas and the most active fermentation?
1. Statement of the Problem/Question How does the ph environment affect yeast CO 2 gas production during fermentation? 2. Hypothesis: ( If, then format) 1) If you increase the acidity (by lowering the ph) of the environment for the yeast from a ph of 6 (for Springs School water) the amount of CO2 gas produced during fermentation will. 2) If you increase the alkalinity (by increasing the ph) of the environment for the yeast from (ph of 6 (for Springs School water) the amount of CO2 gas produced during fermentation will. 3. Variables Independent variable (be specific, say what the 3 ph s are, that s what operationally defined means): Dependent variable (explain how you will measure the independent v., that s what operationally defined means): Constants (also known as Controlled Variables) Include at least 4: 1) 2) 3) 4) 4. Experimental Control
5. Materials 3-500mL flasks and 1-300mL flask 3-latex balloons 3-tablespoons of yeast 3-Tablespoons of sugar 200 ml of 42 degree Celsius water with a ph of 6.0 (Springs School Water) 200 ml of 42 degree Celsius alkaline (basic) water with a ph of 8.0 (with 1 Tablespoon baking soda) 200 ml of 42 degree Celsius acidic water with a ph of 3.0 (with 2 Tablespoons Vinegar) Various sized graduated cylinders Tap water for the graduated cylinders and 300mL beaker Tablespoon sized measuring spoon Funnel Stop Watch 6. Procedure 1. First label the flasks for your experiment. Label each flask #1, #2 and #3,using the following data table as a guide (all bottles will have the same amount of yeast, sugar and water added). 2. Pre-stretch your 3 balloons by blowing each one up twice. Make sure you blow the balloons up to the same size each time for consistency. A six inch diameter is good. Set the deflated balloons aside. 3. Place your goggles on. Keep your goggles on until you have washed your hands at the end of the experiment. 4. Add 1 tbsp of sugar to each flask. Yeast needs sugar for the process of fermentation, 5. Add 1 tbsp of baking powder to flask #2 only. *the baking soda creates basic/alkaline solution 6. Add 2 tbsp of vinegar to flask #3 only. *the vinegar creates an acidic solution 7. Add 25 ml of warm water to each flask. Swirl for 1-2 minutes to mix the ingredients. 8. Cover each flask with plastic or wax wrap to prevent evaporation overnight. 9. The next day Add 200 ml of warm water to each flask 10. Start your stopwatch. 11. Place the funnel into flask #1. Add 1 Tablespoon of yeast to flask #1 and immediately attach a balloon to the top of the flask. Swirl the flask for 1 minute to mix the ingredients.
12. Place the funnel into flask #2. When the stopwatch has reached 2 minutes, immediately add 1 Tablespoon of yeast and attach a balloon to the top of the flask. Swirl the flask for 1 minute to mix the ingredients. 13. Place the funnel into flask #3. When the stopwatch has reached 4 minutes, immediately add 1 Tablespoon of yeast and attach a balloon to the top of the flask. Swirl the flask for 1 minute to mix the ingredients. 14. At the 20 minute mark, gently twist the balloon, on flask #1, several times and remove carefully from the top of your flask. Tie a knot in the end of your balloon. (ask your teacher for help ahead of time if you think you ll need it!) 15. At the 22 minute mark, gently twist the balloon, on flask #2, several times and remove carefully from the top of your flask. Tie a knot in the end of your balloon. (ask your teacher for help ahead of time if you think you ll need it!) 16. At the 24 minute mark, gently twist the balloon, on flask #3, several times and remove carefully from the top of your flask. Tie a knot in the end of your balloon. (ask your teacher for help ahead of time if you think you ll need it!) 17. Now you are ready to measure the amount of gas inside each balloon using a water displacement technique. Fill the smallest graduated cylinder or beaker possible for each balloon (but make sure the balloon will fit in and out!) with enough water to fully submerge the balloon. Make sure that you do not spill any water out of the container, that your hand does not go under the water, and that the entire balloon is submerged. 18. In the data table, write down the Initial Water Amount measured in ml in the graduated cylinder. (this is your water level without the balloon) 19. Then submerge Flask #1 balloon until it is completely covered (I suggest using the eraser end of a pencil or your fingers) 20. Write down the new water level in the data table under After Balloon Submerged Water Level. 21. Complete steps #17-20 for Balloons #2 and #3. 22. Subtract the initial water levels from the After Balloon Submerges Water Level to get the final amount of water displaced which will be equal to the volume of gas produced by the yeast.
Diagrams (at least 2)
7. Qualitative Observations Observations about results (what you noticed at the end of the experiment) Observations about possible procedure/deviations Observations made during the experiment Observations about results not directly relating to the dependent variable
8. Quantitative Data Includes Data Tables Trial 1 Flask Condition Qualitative Observations What you see Water Level Initial Amount Water Level After Balloon Submerged Water Displaced #1 ph 6-7 Neutral #2 ph 10 Alkaline (basic) #3 ph 3 Acidic Example calculations for water displacement gas measurement for Trial #1: Flask #1: - = ml of CO2 produced during fermentation. Flask #2: - = ml of CO2 produced during fermentation. Flask #3: - = ml of CO2 produced during fermentation.
Trial 2 (Who were your associate scientists? ) Flask Condition Qualitative Observations What you see Water Level Initial Amount Water Level After Balloon Submerged Water Displaced #1 ph 6-7 Neutral #2 ph 10 Alkaline (basic) #3 ph 3 Acidic Example calculations for water displacement gas measurement for Trial #2: Flask #1: - = ml of CO2 produced during fermentation. Flask #2: - = ml of CO2 produced during fermentation. Flask #3: - = ml of CO2 produced during fermentation.
Trial 3 (Who were your associate scientists? ) Flask Condition Qualitative Observations What you see Water Level Initial Amount Water Level After Balloon Submerged Water Displaced #1 ph 6-7 Neutral #2 ph 10 Alkaline (basic) #3 ph 3 Acidic Example calculations for water displacement gas measurement for Trial #3: Flask #1: - = ml of CO2 produced during fermentation. Flask #2: - = ml of CO2 produced during fermentation. Flask #3: - = ml of CO2 produced during fermentation.
10. Statistics Flask Condition Trial #1 Water Displaced (CO2 Produced) Trial #2 Water Displaced (CO2 Produced) Trial #3 Water Displaced (CO2 Produced) Mean (average) Water Displaced (CO2 produced) Median Mode #1 ph 6-7 Neutral #2 ph 10 Alkaline (basic) #3 ph 3 Acidic Mean: Flask #1: Example calculations for determining Mean, Median and Mode: Flask #2: Flask #3: Median: Mode:
9, Graph the mean water displacement amount of CO2 produced Title: Dep. variable Independent Variable
11. Analysis and interpretation of data. All statements must be supported by actual quantitative and qualitative data. Numbers, numbers, numbers! 12. Possible Experimental Errors
13. Conclusion 14. Applications and Recommendations for Further Use: How could the experiment be improved? Suggestions for future experiments Practical applications(s) of experiment given (how can what you learned be useful in the real world?)