1.1 a: Separation Techniques

Separation Techniques

Year 12

​What we will cover

• ​physical properties of matter

• separation techniques ​

• flow charts ​

​Physical properties of matter

We use physical properties to separate mixtures, chemical properties are used in relation to chemical changes/reactions

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• Homogenous and heterogenous mixtures

• Colour (not useful)

• Magnetism

• Particle size

• ​Melting and boiling points

• Density ​

​Types of Mixtures

​Physical properties of matter

• Particle size

  • ​not useful in identifying substances, but useful for separating

  • ​use sieves and/or filter paper

• Melting and boiling points

  • melting point = lowest temp for a solid to change into a liquid

  • ​boiling point = lowest temp for liquid to change into a gas

  • ​use as a test for purity (pure = 'sharp' melting point)

• Density​

  • either by measurement or by displacement

  • useful for identification ​

​Separation Techniques

• Filtration

  • ​using filter paper

  • ​based on particle size

• ​Solubility

  • using solubility to separate two solids

  • i.e. sand from salt. Dissolve in water, filter off the sand. ​

​Separation Techniques

Separation based on boiling points

• Dissolved solid from solution

  • evaporating the liquid until only solid is left, as liquid has much lower boiling point than the solid

• ​Distillation

  • solution is boiled, then vapour is condensed back into a liquid and therefore separated from the mixture

  • used to separate liquids with different boiling points

  • FRACTIONAL distillation is used when the boiling points are closer together (less then 40 degrees)​

​Separation techniques

Separations based on density ​

• Decanting

  • when a sediment is formed, the liquid can be decanted off

• Separating funnel

  • when two immiscible liquids (when mixed do not form a homogenous liquid, i.e. oil and water), one will settle on top of the other and then can be separated out via the funnel​

​Separation techniques (less common)

• Fractional evaporation - separating gases based on their different boiling points

• Magnetic separation - exploiting magnetism in different substances

• Centrifuge - density of particles in a liquid

​Separation Flowchart

It is important to represent your flowchart of separation correctly in your answers. Indicating what substances you have and what is being separated out.

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Use diamonds for a separation technique, and rectangles for a substance that is being separated out by that technique, or a substance that is being added.

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E.g. ​Given a mixture of dry salt and salt, outline the procedure to obtain dry sand and dry salt.

Multiple Choice

What is the name of this separation technique?

• distillation

• filtration

• evaporation

• chromatography

Multiple Choice

What is the physical property on which fractional distillation depends?

• different boiling points

• different melting points

• different solubilities

• different densities

Multiple Choice

During filtration, the solid that is trapped in the filter paper is called ..A.. and the liquid that has passed through the filter paper is called ..B..

• A: residue B: filtrate

• A: residue B: filterate

• A: filtrate B: residue

• A: filterate B: residue

Multiple Choice

Which one of the following is the name for separation technique in the picture below

• distillation
• dissolving
• evaporation
• decanting

Multiple Choice

Which one of the following is a disadvantage of evaporation?

• It always requires heat
• It cannot be used for insoluble solids
• All of the solute is recovered
• The solvent (liquid part) is not recovered

Multiple Choice

What is the name of this separation technique?

• Simple distillation

• Fractional distillation

• Boiling

• Evaporation

​Next content

• gravimetric analysis

• nomenclature review ​