This topic summary covers Knowledge Organiser: Alcohols within Alcohols for GCSE Chemistry. Revise Alcohols in Organic Chemistry for GCSE Chemistry with 22 exam-style questions and 15 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Alcohols
Key Terms
- Functional group — -OH (hydroxyl)
- General formula — CₙH₂ₙ₊₁OH
- Fermentation — glucose → ethanol + CO₂
- Hydration — ethene + steam → ethanol
First Four Alcohols
- Methanol — CH₃OH (toxic!)
- Ethanol — C₂H₅OH (drinks)
- Propanol — C₃H₇OH (sanitiser)
- Butanol — C₄H₉OH (industrial)
Fermentation vs Hydration
- Fermentation: renewable, slow, low purity, anaerobic
- Hydration: non-renewable, fast, high purity, 300°C/70atm
Exam Checklist
- Fermentation: don't forget CO₂ product
- Functional group: -OH with dash
- Methanol = TOXIC (not drinkable)
- Fermentation = anaerobic (no oxygen)
Key Equations
- C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (fermentation of glucose)
- C₂H₄ + H₂O → C₂H₅OH (hydration of ethene)
- C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O (complete combustion of ethanol)
- General formula: CₙH₂ₙ₊₁OH
Common Mistakes
- Forgetting CO₂ in fermentation: Fermentation produces BOTH ethanol AND carbon dioxide — missing CO₂ loses a mark
- Saying fermentation needs oxygen: Fermentation is an ANAEROBIC process — it occurs without oxygen; oxygen would allow aerobic respiration instead
- Confusing methanol and ethanol: Methanol (CH₃OH) is TOXIC — even small amounts cause blindness or death; ethanol (C₂H₅OH) is the alcohol in drinks
- Saying hydration uses a biological catalyst: Hydration of ethene uses a phosphoric acid (H₃PO₄) catalyst at ~300°C and 70 atm — not enzymes (that is fermentation)
Practice questions for Alcohols
What is the functional group present in all alcohols?
Explain what happens when ethanol reacts with sodium metal. Include a balanced equation in your answer.
Quick recall flashcards
What are alcohols?
Organic compounds containing the -OH hydroxyl functional group
What is hydration of ethene?
Adding water to ethene to produce ethanol: C₂H₄ + H₂O → C₂H₅OH