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CHEMISTRY FORM 1


i Common Chemistry Laboratory Chemicals
ii Common Chemistry Laboratory Apparatus
iii Safety in the Chemistry Laboratory
iv Why we should learn Chemistry
1. INTRODUCTION TO CHEMISTRY
2. SIMPLE CLASSIFICATION OF SUBSTANCES AND SEPERATION OF MIXTURES
3. ACIDS, BASES AND INDICATORS
4. AIR AND COMBUSTION
5. WATER AND HYDROGEN
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Simple Classification of Substances and Separation of Mixtures: Separation of miscible liquid-liquid mixture (solution)

2.0 Simple Classification of Substances and Separation of Mixtures


2.8 Separation of miscible liquid-liquid mixtures (solution)


Some liquids such as water and ethanol, water and methanol, or kerosene and petrol mix uniformly (form solutions). The methods described earlier cannot separate them.


How can we separate ethanol and water?


Materials and substances required
  1. Distillation flask and fractionating column
  2. Liebig condenser
  3. Tripod stand, wire gauze, retort stands, beakers, thermometer, solution of ethanol in water, wooden splint

Set-up fractional distillation, seperating ethanol and water, high school chemistry

Open the link fractional distillation to observe how ethanol is separated from its uniform mixture (solution) with water.


Questions 2.8

  1. What is the property of the mixture that makes fractional distillation possible?
  2. What are the boiling points of water and ethanol? Water -- Ethanol --
  3. How can we know when all the more volatile component has distilled off so that we stop heating or replace the beaker receiving the distillate?
  4. What is the use of a thermometer in the distillation process?
  5. What is the use of porcelain chips at the bottom of the distillation flask?
  6. What is the use of fractionating column?
  7. What is the function of glass beads in the fractionating column?
  8. Why is the process called fractional distillation?
  9. Explain the use of a Liebig condenser.
  10. How can we test whether the distillate collected is ethanol and not water?
  11. Why is the cold water inlet of a Liebig condenser at the lower end?

Answers to Questions 2.8



Separation of miscible liquid-liquid mixtures makes use of difference in boiling points. During heating, the component with a lower boiling point (more volatile) reaches its boiling point first, boils off, and condenses into a separate container as a distillate (condensate).


The component with the higher boiling point (less volatile) remains in the flask.


In industry

Fractional distillation is used to separate ethanol (an alcohol) from its brewing mixture with water. The process is also used in oil refinery to separate crude oil into various components such as petrol, diesel, kerosene, cooking gas, and butimen (tar).