Learning outcomes

Describe distillation process and explain how it is used to separate water from salt water

Describe fractional distillation process and explain how it is used to separate water from ethanol water mixture

Part 3 Of

Separation TechniqueMethod 7:Method 7:

SIMPLE SIMPLE DISTILLATIONDISTILLATION

Method 7:Method 7: Simple Distillation Simple Distillation

1.Can be used to separate

A)pure water from salt water

B)Pure water from sugar water

2. Diagram drawn by students:

Label thermometer, round bottom flask, Leibig condenser, colleting flask

3. Function of anti bumping agent.

Method 7 Method 7 Simple Distillation

Some Terms Used : DistillateDistillate - the - the liquidliquid that distils over that distils over Miscible liquids Miscible liquids - liquids that - liquids that mix mix

completelycompletely to form a single layer to form a single layer Immiscible liquids Immiscible liquids - liquids - liquids that do not that do not

mixmix A solvent can be separated from a

solution and collected by simple distillation.

Method 7 Method 7 Principle of Distillation

A liquid boils and turns into vapour at its

boiling point.

When the vapour is condensed, the

(pure) liquid is obtained again.

Method 7 Method 7 Simple Distillation

flasksea water

thermometer

1. Solution is heated, causing the solvent to …

2. .. vapourise. The vapour rises up the flask

3. the condenser is cold, so the vapour that enters the neck of the condenser is cooled and condenses to liquid water.

condenser

distillate

Boiling chips 4. Pure water drips into the beaker. It is distilled water.

Method 7 Method 7 Simple Distillation

flasksea water

thermometer

condenserBoiling chips

Water out

Water in

To maintain even boiling, with not too much bumping

Liebig Condenser

Vapour entersCondensed vapour in liquid

form (distillate) leaves

Cold water in

Water out

Direction of water flow

Water flows in anti-current to the flow of vapour.

Liebig Condenser

Vapour entersCondensed vapour in liquid

form (distillate) leaves

Cold water in

Water out

Direction of water flow

This is to make sure the coldest part of the condenser is just before the vapour

escapes.

Method 7 Method 7 Simple DistillationSimple distillation can be used to obtain

from salt solution from copper(II) sulfate solution from a solution of sugar in

ether

Note : The liquid that distils over is called the distillate . The solid that remains in the flask is called the residue .

water

waterether

Method 7 Method 7 Simple DistillationQns. : Where is the thermometer

placed? What is the reason for this?

flasksea water

thermometer

condenser

distillate

Boiling chips

Simple DistillationThermometer placed at the side arm of the

flask so that it records the temperature of the vapour as it enters the condenser.

flasksea water

thermometer

condenser

distillate

Boiling chips

Part 3 Of

Separation TechniqueMethod 8:Method 8:

FRACTIONAL FRACTIONAL DISTILLATIONDISTILLATION

Separating miscible liquids - Fractional distillation• miscible liquids can only be

separated by fractional distillation if they have different boiling points .

• Eg. mixture of ethanol and water.Boiling point of water is 100Boiling point of water is 100°°CC

Boiling point of ethanol is 78°CWhich gets boiled off first?

Separating miscible liquids - Fractional distillation

flask

thermometer

mixture of ethanol and water

Water out

Water in

condenser

distillate

Boiling chips

Fractionating column

How ethanol and water Mixture is separated?Name of method: Fractional distillationFractional distillation

Reason used: Two liquid have different Two liquid have different boiling point can be separated. boiling point can be separated. The liquid with lower boiling point is distilled over first.

Example:

Pure liquid Water boils at 100 °C and Pure liquid ethanol boils at 78 °C.

So, ethanol with lower boiling point boils and forms vapour first.

1. The ethanol and water mixture is not flammable.

It can be directly heated with an open flame from bunsen burner. Anti-bumping agents are used to prevent violent boiling.

2. The fractionating column is packed with glass beads to increase its surface area. Vaporisation followed by condensation takes place many times as the vapour is swept upwards.

3. As the vapour rises higher, the temperature of the vapour increase. The vapour contains more of ethanol.

4. The vapour that enters the Leibig condenser is pure ethanol and the thermometer shows a temperature of 78 °C.

5. Pure ethanol Vapour that enters the Leibig condenser is cooled to liquid ethanol.

6. All ethanol liquid will boil to vapour and pure ethanol vapour will condense out to form pure ethanol first. The temperature shown by thermometer as 78 °C.

7. After all the ethanol has boiled over and condenses out, water will boil into vapour and then condenses out. This time the thermometer shows a temperature reading of as 100 °C.

2. The fractionating column is packed with glass beads to increase its surface area. Vaporisation followed by condensation takes place many times as the vapour is swept upwards.

3. As the vapour rises higher, the temperature of the vapour increase. The vapour contains more of ethanol.

4. The vapour that enters the Leibig condenser is pure ethanol and the thermometer shows a temperature of 78 °C.

5. Pure ethanol Vapour that enters the Leibig condenser is cooled to liquid ethanol.

6. All ethanol liquid will boil to vapour and pure ethanol vapour will condense out to form pure ethanol first. The temperature shown by thermometer as 78 °C.

7. After all the ethanol has boiled over and condenses out, water will boil into vapour and then condenses out. This time the thermometer shows a temperature reading of as 100 °C.

Separating miscible liquids Fractional distillation

1. When heated, the liquid with the lower boiling point will vaporize more readily.

2. The fractionating column is packed with

glass beads to increase its surface area.

Vaporisation followed by condensation takes place

many times as the vapour is swept

upwards.

3. Eventually, the liquid with the lower boiling point reaches the top and distils over.

Separating miscible liquids - Fractional distillation

5. The receiver is changed to collect each distillate separately.

4. The temperature stays constant at

78°C. When all the ethanol has distilled

over, the temperature reading

rises above 78 °C. At 100°C, water

starts to distil over.

Separating miscible liquids - Fractional distillation

Sketch a graph of temperature versus time to show the changes in temperature readings to obtain pure ethanol from the ethanol water mixture

temperature

time

78°C

100°C

Separating miscible liquids - Fractional distillation

Sketch a graph of temperature versus time to show the changes in temperature readings for the total time in separating the pure liquid.

temperature

time

100°C

Sketch a graph of temperature versus time to show the changes in temperature readings to obtain pure ethanol from the ethanol water mixture

temperature

time

78°C

100°C

Separating miscible liquids - Fractional distillationNote : • The glass beads in the

fractionating column provides a large surface area so that condensation occurs more readily.

• The liquid with the lower boiling point distils

over first, followed by the liquid with the next higher boiling point.

glass beads

Separating miscible liquids - Fractional distillationNote : • If the liquids in the mixture

have the same boiling point, fractional distillation is not possible.

• If the difference in boiling point is great, fractional distillation occurs readily.

glass beads

B

D

C

A Ethanol and water mixture

F1

F2

E

F

Fractional distillation - applications

Fractional distillation can be used to separate :-

nitrogen and oxygen from liquid air

the components of crude oil

ethanol from fermented liquor

Fractional distillation of crude oil