1 st Year Science – Chemistry

Separating Mixtures – Introduction Mixtures: ‘ A mixture is made up of 2 or more substances mingled together but not chemically combined’ e.g. Air – oxygen, carbon dioxide, Nitrogen e.g. Cup of Coffee – coffee granules, milk, water, sugar e.g. Sea Water– water, salt, chlorine and many more

Ways of Separating Mixtures Decanting: Decanting: Filtration & Evaporation: Filtration & Evaporation: Distillation: Distillation: Chromatography: Chromatography: Separating Different Dyes in inks Uses evaporation to separate 2 liquids Uses evaporation to separate 2 liquids Separating solids from liquids FiltrationEvaporationDistillation Chromatography Very Basic method

Separating Solids from liquids The type of separation depends on whether the solid is Soluble or Insoluble in the liquid Soluble: Solids that dissolve in liquids to form a solution e.g. Sugar in tea or coffee, Salt in sea water e.g. Sugar in tea or coffee, Salt in sea water Insoluble: Solids that don’t dissolve. Instead they sink to the bottom of the liquid e.g. Sand & soil in water e.g. Sand & soil in water Evaporation can be used to separate soluble solids and Liquids Filtration can be used to separate insoluble solids and Liquids

Filtration Experiment Title: ‘Separation of Soil and Water’ Apparatus: Beaker, Stirring rod, Retort stand, Funnel, Filter paper, Soil/water mixture Filtrate Filter paper

Evaporation Experiment Title: ‘Separation of Salt and Water through Evaporation’ Apparatus: Bunsen Burner, Tripod, Evaporating Dish, Salt water solution, Beaker of Water (optional) Evaporating Dish Tripod Bunsen Burner Salt water Solution

Separating Solids from liquids Another basic method of filtration is Decanting Water Water Sand Solids are allowed to settle at the bottom of the liquid and then water is gently drained off.

Distillation The problem with evaporation is that the liquid is lost. The problem with evaporation is that the liquid is lost. Distillation is a method of separation that saves the liquid(s) Distillation is a method of separation that saves the liquid(s) Distillation is used to separate... 1.Two miscible liquids (liquids that mix) e.g. Water and alcohol 2.Soluble solids from liquids e.g. Salt and water Two types of Distillation... 1.Simple distillation 2.Fractional Distillation Immiscible means substances that do not mix together e.g. Water & oil

Distillation Simple Distillation Simple Distillation: e.g. Separation of two miscible liquids – Water and alcohol Both liquids have two different boiling points... Both liquids have two different boiling points... Water = 100⁰C Alcohol = 78⁰C Some water evaporates with the alcohol, therefore it is not a perfect method of separation Some water evaporates with the alcohol, therefore it is not a perfect method of separation Bunsen Burner Tripod Liebig Condenser Distillate Thermometer Wire Gauze Water In Water Out Can also be used to separate liquids and solids (salt & water) Can also be used to separate liquids and solids (salt & water) Round Bottom Flask Cooling water condenses steam back into water droplets (distillate) Cooling water condenses steam back into water droplets (distillate) Solution Solution

Distillation Fractional Distillation Fractional Distillation: Bunsen Burner Bunsen Burner Tripod Wire Gauze Wire Gauze Liebig Condenser Distillate Thermometer Water In Water Out Round Bottom Flask Solution Solution Fractionating Column Greater quality of separation Greater quality of separation Fractionating column is heated to the boiling point of alcohol (78⁰C) Fractionating column is heated to the boiling point of alcohol (78⁰C) The water cools down over the long distance and condenses back into droplets. The water cools down over the long distance and condenses back into droplets. The pure alcohol continues on through the Liebig condenser and condenses at the other end as distillate. The pure alcohol continues on through the Liebig condenser and condenses at the other end as distillate.

Distillation – Separating Salt and Water

Chromatography Chromatography is a method used to separate complex mixtures Chromatography is a method used to separate complex mixtures e.g. Hospitals: Analysing blood samples e.g. Forensics: Analysing samples from crime scenes How Chromatography is carried out: A coloured dot is placed at one end of the chromatography paper A coloured dot is placed at one end of the chromatography paper The strip is placed in a beaker/cylinder that contains a solvent (water) The strip is placed in a beaker/cylinder that contains a solvent (water) The strip is placed in the solvent with the ink dots above solvent (water) level. The strip is placed in the solvent with the ink dots above solvent (water) level. The solvent (water) is absorbed upwards through the paper and carries the different dyes with it The solvent (water) is absorbed upwards through the paper and carries the different dyes with it Some dyes only go up to a certain point therefore separating them out. Some dyes only go up to a certain point therefore separating them out.

Chromatography How Chromatography is carried out: Chromatography Paper Solvent (water) Ink Spots After minutes Direction of Absorbed Solvent Separated Dyes Container