Separation Techniques

Separation Techniques

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Learning Objective

At the end of the lesson you should able to:

• understand the difference between pure substance and mixtures.

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A mixture is made up of two or more substances that are not chemically combined together.

Mixtures

Mixtures

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When two or more elements physically combined. Alloy is an example of a mixture of elements .

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Mixtures of elements

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When two or more compounds physically combined. Seawater is an example where salt and water physically combined.

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Mixture of compounds

When two or more compounds and elements physically combined. Surround air is a very good example.

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Mixture of compounds and elements

Open Ended

Name a mixture that you encounter in your everyday life.

Pure Substance

A pure substance is made up of one single element or compound. It is not mixed with any other substance.

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Fun fact:

Diamond is highly compressed carbon element

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Examples of mixtures:

Filtration is used to separate insoluble particles from a liquid.

Filtration

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• sand and water

• chalk powder and water (suspension)

• •clay and water

Open Ended

What do you think the picture is trying to illustrate about filtration?

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

This is a process of obtaining a soluble solid from a solution by heating the solution until all the water has boiled off.

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Evaporation to Dryness​

Substances that decompose on heating cannot be obtained by evaporation to dryness.

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e.g. Sugar decomposes on heating

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Evaporation to Dryness​

Process of obtaining pure solid sample (soluble solid) from its solution.​

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Crystallisation

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​Copper (II) Sulfate Crystals

Evaporation to dryness and Crystallisation​

​https://www.youtube.com/watch?v=vi_SJBnxmHo&ab_channel=Cognito

Multiple Choice

Which separation technique is used to obtain salt from seawater?

• Simple distillation

• Filtration

• Chromatography

• Evaporation

Fill in the Blank

What is the name of this separation technique?

Simple Distillation

Simple distillation is used to separate a pure solvent (liquid) from a solution.

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​Examples:

Extraction of water from:

•sea water

•salt (sodium chloride) solution

•sugar solution​

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Multiple Choice

Which separation technique is used to obtain pure water from seawater?

• Simple distillation

• Filtration

• Chromatography

• Evaporation

Multiple Choice

Which of the following statements tells us that a sample of liquid is pure water?

• It is colourless.

• It leaves no residue when filtered.

• It boils at 100^oC.

• It is odourless.

Multiple Choice

What is the name of this separation technique?

• Simple distillation

• Fractional distillation

• Boiling

• Evaporation

This method can be used to separate a mixture of miscible liquids with different boiling points.

​Liquids that mix together completely to form a solution are described as miscible.

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Examples: Ethanol and water ​

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Fractional Distillation​

Recall:

From Chapter 1 Kinetic Particle Theory:

1. what physical states were present when ​the temperature is constant?

2. Why did the temperature remain constant?​

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Heating curve of Fractional Distillation

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To separate:

1. the various components of crude oil such as petrol, kerosene, diesel in oil refineries.

2. nitrogen, oxygen and argon in liquid air.

3. ethanol from the fermentation mixture of water, glucose and malt in breweries.​​

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Industrial Application of Fractional Distillation

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​Fractional Distillation of Air

https://www.youtube.com/watch?v=J6J47XX55CU&ab_channel=FuseSchool-GlobalEducation​

Multiple Choice

What is the physical property on which fractional distillation depends?

• different boiling points

• different melting points

• different solubilities

• different densities

Chromatography is the method of separating two or more components that dissolve in the same solvent.

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Paper Chromatography

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Open Ended

Can you think of any use of colour pigment in our daily live?

• Depend on relative solubility of the component

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• More soluble travel ​faster and further from start line

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• less soluble travel slower and closer to start line​

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Which color pigment in the picture is the most and least soluble?

Principle behind paper chromatography

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• Identical dyes travel up the same distance and produce the same colour on the paper when the same solvent is used

• ​The chromatography paper with the separated components is called a chromatogram.

Which color pigment in the picture is the most and least soluble?

Principle behind paper chromatography

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Open Ended

Why is the chromatogram on the right is a pure substance?

Open Ended

Chromatography was performed on a sample of food colouring (‘X’) and 4 banned dyes (‘A’, ‘B’, ‘C’ and ‘D’). If X contains any of the 4 banned dyes, it is not safe to be consumed. What conclusions can we drawn from the chromatogram shown?

• Identical dyes produce spots at the same height.

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• Sample X does not contain the banned dyes A, B and D.

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• However, X contains the banned dye C. Therefore, it must not be consumed.

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Conclusions that can be drawn from the chromatogram:​

• ​Dyes A and D are pure.

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• Both dye B and dye C are mixtures of two different dyes.

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• Sample X is a mixture of three dyes.

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Conclusions that can be drawn from the chromatogram:​

Multiple Choice

If a substance is not soluble in the solvent, what happens to the spot placed on the start line?

• a) Dot moves to the top of the paper

• b) Dot does not move at all

• c) Dot moves to the left or right

• d) Dot moves down to the bottom of the paper

Multiple Choice

Why must the base line be drawn in pencil and not pen?

• a) Pencil is good at keeping substances in place.
• b) Pencil is soluble in water
• c) Pencil is insoluble in water
• d) Pencil is not coloured

Multiple Choice

A pure substance shows ------------------ spot on chromatogram

• 0

• 1

• 2

• 3

Multiple Choice

chromatography separates the mixture of dyes on the basis of their ----------------------------

• density
• solubility
• gravity
• boiling point

Multiple Choice

Referring to the chromatogram, black ink contains

• Blue, red and yellow ink only

• Blue, red, yellow and green ink

• Blue and yellow ink

• Black ink only

Multiple Choice

Which ink is a mixture?

• Blue

• Red

• Yellow

• Black

Multiple Choice

Which ink is most soluble?

• Blue

• Red

• Yellow

• Green

Multiple Select

What change of states are included in fractional distillation? (Can select two or more answers)

• Melting

• Evaporation

• Condensation

• Freezing

Multiple Choice

The laboratory apparatus used to collect 15.0 cm³ of oxygen gas from a chemical reaction.

• gas syringe

• condenser

• pipette

• burette

Multiple Choice

A liquid ester used to flavour food is believed to be impure. What would be the best way of testing its purity?

• filter it

• measure its boiling point

• use paper chromatography

• evaporation to dryness

Multiple Choice

In an experiment, a student needs to measure out 36.50 cm³ of a solution. Which piece of apparatus would measure this volume most accurately?

• beaker

• burette

• measuring cylinder

• pipette

Multiple Choice

An unknown gas can be collected using the apparatus shown.

Based on the diagram only, what can your infer about the physical property of this gas?

• It is denser that air.

• It is insoluble in water.

• It is less dense than air.

• It is soluble in water.