Yeast Fermentation Lab
Answer all the following on a separate piece of notebook paper:
1. Hypothesis
2. Data table (see board)
3. Discussion questions (complete sentences)
Purpose: to observe the effect of environment on yeast activities.
Hypothesis: Based on what you have learned about respiration and fermentation, state
which of the below groups (1-5) you think will produce the largest balloons? Explain
your answer.
Materials:
package of dry active yeast ruler or meter stick
250 mL beaker
string
250 mL flask
balloon
sugar packets
warm water (40 ºC)
artificial sweetener packets
Procedure:
1) Fill the beaker with 100 mL of warm tap water.
2) Add 1 package of yeast to the warm water and stir until it is in solution.
3) Carefully pour the yeast solution into the flask.
4) Complete the lab according to the group you have been assigned.
5) Thoroughly clean up your area and the glassware with soap and water. I will deduct
points for any group who leaves any mess. Return glassware to your area.
Group 1: After pouring your yeast solution into the flask, immediately
place the balloon on the top of the flask. Note the time on your lab chart.
Group 2: After pouring your yeast solution into the flask, add 1 packet
of sugar to the mixture and swirl it gently until it dissolves. Then place the
balloon on top of the bottle. Note the time on your lab chart.
Group 3: After pouring your yeast solution into the bottle, add 2
packets of sugar to the mixture and swirl it gently until it dissolves. Then
place the balloon on top of the bottle. Note the time on your lab chart.
Group 4: After pouring your yeast solution into the bottle, add 3
packets of sugar to the mixture and swirl it gently until it dissolves. Then
place the balloon on top of the bottle. Note the time on your lab chart.
Group 5: After pouring your yeast solution into the bottle, add 2
packets of artificial sweetener to the mixture and swirl it gently until it
dissolves. Then place the balloon on top of the bottle. Note the time on
your lab chart.
5) Using your string, measure the size of your balloon every 5 minutes.
Record the information on your data table.
Results: SIZE OF BALLOON
Start ____
5 min.
Group 1
Group 2
Group 3
Group 4
Group 5
10 min.
15 min.
20 min.
25 min.
Graphing:
Graph the above date on one graph. You should have 5 line graphs. You can use excel
if you want. (see resources for excel graphing instructions)
Discussion:
1) What was the purpose of this lab?
2) How would you summarize your procedure in two sentences? (what is the big
picture?)
3) Which of the balloons reached the largest size?
4) What material was collected in the balloons?
5) What was the fuel for the process?
6) Which type of fermentation did you witness? How do you know?
7) What was/were the variable(s) in this experiment?
8) Which one of the groups was the control? Why was it the control?
9) Make a multi-line graph of the data. Include a legend.
10) What is fermentation? What are the products of fermentation? What caused the
balloons to increase in size?
11) How did the results for the flask containing artificial sweetener compare with the
flasks containing sugar? Explain your results.
12) List at least three sources of error for this lab.
Conclusion:
Yeast is used in making bread. Using the information obtained in this
experiment to explain what causes bread to rise and what conditions are necessary for
optimum rising.