Guided practical worksheet 22.6
Designing an investigation of alcoholic fermentation
in yeast (Investigative approach)
Class:
Student name:
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Group:
Date:
Introduction
Historians believe that alcoholic fermentation was discovered by accident. One belief is that
someone in the Stone Age left berries or grains in a pot and wild yeast from the air fermented the
sugars in the food into alcohol.
Task
Design and perform an investigation to study alcoholic fermentation in yeast. The following
materials and apparatus are provided for you.
3

1 beaker (250 cm )

2 two-holed stoppers (for vacuum flasks)

1 Bunsen burner

2 two-holed stoppers (for conical flasks)

1 wire gauze

2 rubber tubings

1 tripod

10% glucose solution

1 heat-proof mat

yeast suspension

2 vacuum flasks

paraffin oil
3

1 measuring cylinder (10 cm )

hydrogencarbonate indicator

1 glass rod

safety goggles

2 thermometers

heat-resistant gloves

2 conical flasks

4 delivery tubes
HKDSE BIOLOGY: Connecting Concepts
© 2020 Aristo Educational Press Ltd.
1
Guided practical worksheet 22.6
Designing an investigation of alcoholic fermentation in yeast (Investigative approach)
Write a full report of your investigation. Below are some guidelines and questions to help you write
your report.
A. The design of your investigation
1.
What is the aim of your investigation?
2.
What are the products of alcoholic fermentation? What conditions are needed for
alcoholic fermentation?
3.
What is the independent variable? How would you change it?
4.
What is the dependent variable? How would you measure it?
5.
What are the control variables? How would you keep these variables constant?
6.
Do you need to set up a control? If yes, what is the purpose of setting up the control?
7.
What assumptions do you need to make when designing your investigation?
B. The procedure of your investigation
1.
State the detailed procedure of how you conduct the investigation.
2.
What materials and apparatus are used in each procedure?
(Hint: State the quantity of materials used.)
3.
How can you ensure that the data obtained for the dependent variable are accurate and
valid?
4.
What are the potential hazards in this investigation? What safety precautions should be
taken?
HKDSE BIOLOGY: Connecting Concepts
© 2020 Aristo Educational Press Ltd.
2
Guided practical worksheet 22.6
Designing an investigation of alcoholic fermentation in yeast (Investigative approach)
C. The results
Present your results as in the table below.
The products formed in the experimental and control set-ups
Colour of
hydrogencarbonate
indicator solution
Temperature (°C)
Set-ups
Initial
Final
Initial
Smell
Final
Experimental set-up
(with suspension of
living yeast)
Control set-up
(with boiled yeast
suspension)
D. Discussion and conclusion
1.
Explain the results of the set-ups
2.
Are there any problems with the investigation that may cause other people cast doubt on
the results? For example, are the data obtained reliable? What are the possible sources of
errors in your investigation? How could these problems and errors be avoided or
reduced?
3.
Are there any limitations on the design of the investigation? How can the design be
improved?
4.
Try to suggest further investigations that can be done.
5.
What conclusion can you draw with reference to the results and the aim (or hypothesis)
of the investigation?
HKDSE BIOLOGY: Connecting Concepts
© 2020 Aristo Educational Press Ltd.
3