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Separating MixturesJunior Science

Terminology

• Soluble – the substance dissolves

• Insoluble – the substance does not dissolve

• Miscible – the substance can mix easily with another substance (salt/water)

• Immiscible – the substance does not mix easily with another substance (oil/water)

• Mixture – two or more substance mingled together but not chemically combined

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Separating Mixtures• Mixtures can be easily separated when there are

physical differences between the substances in the mixture.

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Immiscible(Oil and Water)

Magnetic(Iron)

Soluble(Copper Sulfate)

Separating Mixtures Pair Assignment

• Can you think of a physical difference between the following which enables them to be separated

Sulphur and Iron Filings

Sand and Sawdust

Sand and Salt

Sand and Water

Salt and Water

Oil and Water

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Iron is Magnetic

Sawdust floatsSalt is Soluble in water

Sand is Insoluble in water

Water Evaporates

Oil Floats on water

How can we separate the following?

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Insoluble solid and a liquid

Soluble solid and a liquid

Two liquids

Two immiscible liquids

Two solids

DECANTING and FILTRATIONUse to separate an Insoluble solid and a liquid

Sand and Water

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Decanting

Is a method used to separate an insoluble solid from a liquid.

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In decanting the liquid is poured gently so as not to disturb the sediment.

Filtration

• Filtration is a method used to separate small insoluble solids from a liquid.

• It uses a funnel and filter paper to trap the solid particles.

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FILTRATION and EVAPORATION

Insoluble Solid and a Soluble Solid

Sand and Salt

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Evaporation

Is a method used to separate soluble

solids from a solution by evaporating off the

liquid to leave the solid.

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Evaporation Dish

Crystallisation

Occurs when crystals appear from a solutions which has been evaporated.

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If cooled slowly Large crystals will form

If cooled quickly Small crystals will form

DISTILLATIONUse to separate a Soluble solid and a liquid

Copper Sulphate and Water

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Distillation Apparatus

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Leibig Condenser

Round bottom Flask

Conical Flask

Water (Distillate)

Water IN from Cold Tap

Distillation

• Distillation can be used to separate two liquids with different boiling points. For example Alcohol and Water

ALCOHOL Boiling point 78o C

WATER Boiling point 100o C

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DISTILLATIONTwo Liquids - Alcohol and Water

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Leibig Condenser

Thermometer Maintain at boiling point of Alcohol (78oC)

Round bottom Flask

Conical Flask

Alcohol (Distillate)

Water IN from Cold Tap

• Is a technique used to separate very small quantities of substances which vary in solubility in different solvents.

• Chemists use chromatography to determine

- colouring matter in food

- the presence of drugs in urine or blood

- natural compounds in urine which can cause disease.

Chromatography

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Paper Chromatography

used to separate the dyes in Ink 18

Separating FunnelTwo immiscible Liquids - Water and Oil

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Separating MixturesTwo Solids - Iron and Sulphur

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A magnet attracts the iron particles but not the sulphur

particles.

Summary

• Mixtures can be separated using a number of methods

– Settling (insoluble solid and liquid)

– Decanting (insoluble solid and liquid)

– Filtration (insoluble solid and liquid)

– Evaporation (soluble solid and liquid)

– Distillation (Soluble solid and liquid)

– Fractional Distillation (two substances with different boiling points)

– Chromatography (Dyes in Ink, Gases)

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