Overview
This lecture explains the principles and equipment for simple and fractional distillation, methods used to separate mixtures of liquids based on their boiling points.
Simple Distillation
- Used to separate a liquid from a solution, e.g., obtaining pure water from seawater.
- Essential equipment: flask (with mixture), bung, thermometer, condenser (with water jacket), beaker, and heat source.
- The mixture is heated; the liquid with the lower boiling point evaporates first.
- Vapor enters the condenser, cools, condenses back to liquid, and is collected in a beaker.
- Remaining substance (like salt) stays in the flask.
Limitations of Simple Distillation
- Ineffective when separating mixtures of liquids with similar boiling points (e.g., methanol, ethanol, propanol).
- Multiple liquids may evaporate together, preventing pure separation.
Fractional Distillation
- Used to separate mixtures of liquids with close boiling points.
- Equipment includes a fractionating column filled with glass rods in addition to the simple distillation setup.
- The column provides high surface area and a temperature gradient (cooler at the top).
- Liquids with the lowest boiling points evaporate and rise first, condensing in the column if they meet cooler temperatures, while higher boiling liquids fall back.
- By gradually increasing temperature, each component can be separated and collected as a pure substance.
Key Terms & Definitions
- Distillation — A process for separating mixtures based on differences in boiling points.
- Simple Distillation — Separates a liquid from a solution using evaporation and condensation.
- Condenser — Equipment that cools vapor back into liquid, often using a cold water jacket.
- Fractional Distillation — Separates mixtures of liquids with similar boiling points using a fractionating column.
- Fractionating Column — A column filled with glass rods providing high surface area and a temperature gradient for better separation.
Action Items / Next Steps
- Review equipment diagrams for both types of distillation.
- Practice identifying which distillation method to use for various liquid mixtures.