ChemistryChapter 17: Separation Techniques
Types of Distillation
Simple distillation suits solvent recovery or two liquids with widely different BP.
Learning objectives
- State the main idea of types of distillation in clear words.
- Explain why types of distillation is useful in chemistry.
- Apply the correct method, observation, equation, or comparison.
- Avoid the common mistakes and write a complete exam answer.
Definition
Simple distillation suits solvent recovery or two liquids with widely different BP. Fractional distillation suits closer BP miscible liquids: a column has a temperature gradient and the vapour condenses and revaporises many times. Alcohol and water need fractional distillation, not filtration, because both are liquids and they mix.
Important terms
- Simple distillation
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- widely different BP
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- Fractional distillation
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- closer BP
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- miscible
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- temperature gradient
- Simple distillation suits solvent recovery or two liquids with widely different BP.
Overview
Two extra tricks, then two big uses:
Steam and Vacuum
Steam distillation is for heat-sensitive oils and perfumes: steam carries the oil over at a safer T. Vacuum distillation lowers BP by lowering external P, so a high-BP liquid need not be overheated.
Examples Rose oil with steam · Perfume oils · High-BP oil under vacuum
Crude Oil and Air
Crude oil is split into fractions by BP in a fractionating column. Distilled water for batteries removes ions that would conduct. Cryogenic distillation of air gives N2, O2, and argon after the air is liquefied.
Examples Petrol and diesel cuts · Battery top-up water · Air to N2, O2, argon
WHAT — Core idea
Simple distillation suits solvent recovery or two liquids with widely different BP. Fractional distillation suits closer BP miscible liquids: a column has a temperature gradient and the vapour condenses and revaporises many times. Alcohol and water need fractional distillation, not filtration, because both are liquids and they mix.
WHY — Why it matters
Do not say "filter alcohol from water." They form one homogeneous liquid. Use a fractionating column. Simple distillation is enough when BP values sit far apart, or when you only need to recover a solvent from a solid.
HOW — Method, evidence, or comparison
1. 1. STEAM AND VACUUM: Steam distillation is for heat-sensitive oils and perfumes: steam carries the oil over at a safer T. Vacuum distillation lowers BP by lowering external P, so a high-BP liquid need not be overheated. 2. 2. CRUDE OIL AND AIR: Crude oil is split into fractions by BP in a fractionating column. Distilled water for batteries removes ions that would conduct. Cryogenic distillation of air gives N2, O2, and argon after the air is liquefied.
HOW — Answer in an exam
Fractional = closer BP and miscible. Simple = widely different BP or solvent from a solid. Steam = heat-sensitive oils. Vacuum = lower the BP on purpose.
Explanation
Do not say "filter alcohol from water." They form one homogeneous liquid. Use a fractionating column. Simple distillation is enough when BP values sit far apart, or when you only need to recover a solvent from a solid.
In simple words
Fractional = closer BP and miscible. Simple = widely different BP or solvent from a solid. Steam = heat-sensitive oils. Vacuum = lower the BP on purpose.
Key points
- Simple distillation
- widely different BP
- Fractional distillation
- closer BP
- Steam distillation
- heat-sensitive
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Types of Distillation
Sticky Notes · Quick Revision
WHAT
- Simple distillation suits solvent recovery or two liquids with widely different BP.
Key Points
- Simple distillation
- widely different BP
- Fractional distillation
- closer BP
- miscible
HOW
- Steam distillation is for heat-sensitive oils and perfumes: steam carries the oil over at a safer T.
- Crude oil is split into fractions by BP in a fractionating column.
Example
- Rose oil with steam
- Perfume oils
- High-BP oil under vacuum
Common Mistake
- Use fractional, not simple, distillation for miscible liquids with close boiling points.
Exam Tip
- Fractional = closer BP and miscible.
- Simple = widely different BP or solvent from a solid.
60-second revision
- Simple distillation suits solvent recovery or two liquids with widely different BP.
- Fractional distillation suits closer BP miscible liquids: a column has a temperature gradient and the vapour condenses and revaporises many times.
- Steam distillation is for heat-sensitive oils and perfumes: steam carries the oil over at a safer T.
- Crude oil is split into fractions by BP in a fractionating column.
- Fractional = closer BP and miscible.
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