Chapter 19:Separating Mixtures

What I should know:

• Define a mixture• List techniques used to separate mixtures, and

explain them– Decanting– Filtration– Evaporation– Distillation– Chromatography

Experiments I should know:

• To separate soil and water using filtration• To separate salt and water through

evaporation• To separate salt and water through distillation• To separate the dyes in water soluble markers

using chromatography

What is a Mixture?

Definition:A mixture is made up of two or more substances mingled together but not chemically combined..

Everyday examples of mixturesinclude crudeoil, sea water and air.

How can you separate mixtures?

1) Decanting:Decanting is a technique used to separate insoluble solids and liquids, e.g. sand and water.

Procedure:Allow the solid to sink to the bottom and gently pour off the liquid.

How can you separate mixtures?

2) Filtration:Filtration is used to separate a liquid and an insoluble solid, e.g. sand and water.

Filtration uses a material which allows the liquid to pass through but not the solid - e.g. filter paper.

Filtration

Exp. 1: To Separate Soil and Water

Equipment:conical flask, filter funnel,filter paper, beaker.Chemicals:Water and soil sampleMethod:1. Set up the apparatus as shown.2. Slowly (& carefully) pour the mixture into the filter

paper as shown.3. Allow time for the water to separate from the soil.

Exp. 1: To Separate Soil and Water

Result:The insoluble solid (soil) is unable to pass through the pores in the filter paper and is trapped. This is known as the residue.Clear water passes through the filter paper and is collected in the conical flask. This is the filtrate.Conclusion:Soil can be separated from water by filtration.

How can you separate mixtures?

3) Evaporation:Evaporation is used to separate a liquid and an soluble solid, e.g. salt and water.

The solution is heated until the liquid evaporates, leaving the just the solid behind.

Exp. 2: To Separate Salt and Water

Equipment:Evaporating dish, beaker, tripod,wire gauze, Bunsen burnerChemicals:Solution of salt waterMethod:1. Set up the apparatus as shown, and heat

until the water in the dish has evaporated.

2. Carefully remove the evaporation dish & observe the residue (the salt).

Exp. 2: To Separate Salt and Water

Result:As the solvent (water) is evaporated, the solute (salt) comes out of solution and forms crystals. Conclusion:Salt can be separated from water by evaporation.

How can you separate mixtures?

4) Distillation:In distillation a liquid is vaporised by boiling, and then condensed by cooling.• Distillation is a technique that can be used to

separate a soluble solid from a liquid e.g. salt and water.

• Or to separate two miscible liquids (liquids that mix) on the basis that they have different boiling points e.g. alcohol and water.

Distillation – Liebig Condenser

How can you separate mixtures?

5) Chromatography:This can be used to separate a mixture of dissolved substances in a solution - e.g. a mixture of dyes in ink.