Ethanol can be produced by two different industrial and biological methods. Describe the differences between the fermentation of glucose and the hydration of ethene as methods of producing ethanol. Include the conditions required for each method.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Fermentation uses glucose as the raw material, whereas hydration of ethene uses ethene from crude oil.
Fermentation requires yeast (or the enzymes from yeast) as a catalyst and takes place at a low, warm temperature of about 30–40 °C. It is a batch process that produces a dilute ethanol solution, which must then be distilled or otherwise purified.
Hydration of ethene uses an acid catalyst, typically phosphoric acid (H₃PO₄), and is carried out at a high temperature of about 300 °C. It is a continuous process that yields a more concentrated, essentially pure ethanol.
Fermentation requires yeast (or the enzymes from yeast) as a catalyst and takes place at a low, warm temperature of about 30–40 °C. It is a batch process that produces a dilute ethanol solution, which must then be distilled or otherwise purified.
Hydration of ethene uses an acid catalyst, typically phosphoric acid (H₃PO₄), and is carried out at a high temperature of about 300 °C. It is a continuous process that yields a more concentrated, essentially pure ethanol.
Examiner tips
- Use the exact terms: glucose, ethene, yeast, phosphoric acid, 30–40 °C, 300 °C, batch, continuous, dilute, pure.
- Show clear comparison points – raw material, catalyst, temperature, process type, purity.
Common mistakes
- Confusing the temperature ranges (e.g. writing 300 °C for fermentation).
- Failing to mention that fermentation is a batch process and hydration is continuous.
Mark scheme (4 marks)
- Fermentation uses glucose (sugar) as the raw material / hydration of ethene uses ethene (from crude oil/petroleum) as the raw material
- Fermentation requires yeast / enzymes (from yeast) as a catalyst; hydration of ethene uses an acid catalyst (phosphoric acid / H₃PO₄)
- Fermentation occurs at a low / warm temperature (approximately 30–40 °C); hydration of ethene occurs at a high temperature (approximately 300 °C)
- Fermentation is a batch process producing dilute ethanol (must be distilled / purified); hydration of ethene is a continuous process producing pure / more concentrated ethanol
Key terms in this question
fermentation · hydration · ethene · glucose
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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