Making ethanol by fermentation
4 marks · Normal| Temperature (°C) | Ethanol produced after 2 days (cm³) |
|---|---|
| 10 | 3 |
| 20 | 15 |
| 30 | 28 |
| 40 | 10 |
| 50 | 0 |
Describe the effect of temperature on the amount of ethanol produced after 2 days.
Suggest a temperature range suitable for the fermentation process to produce the most ethanol.
Explain why no ethanol is produced at 50°C.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Ethanol production increases as temperature rises from 10°C to 30°C, reaching a maximum at 30°C, then decreases above 30°C.
(b) Between 30°C and 35°C.
(c) At 50°C, yeast enzymes are denatured so fermentation does not occur.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Describes increase in ethanol produced from 10°C to 30°C.
B2 (a) · 1 mark · Describes ethanol production decreases above 30°C.
B3 (b) · 1 mark · Gives temperature range around 30–35°C as suitable.
B4 (c) · 1 mark · Explains yeast enzymes denatured at 50°C so fermentation is stopped.
Worked solution
a) The amount of ethanol produced increases as temperature rises to 30°C, after which the production drops sharply at higher temperatures.
b) A suitable temperature range is around 30°C to 35°C.
c) At 50°C, the enzymes in yeast are denatured and stop working, so no ethanol forms.