Separation techniques - PowerPoint Presentation

Slide1

Separation techniquesSlide2

Objectives

To understand the key separation techniques used to separate mixturesSlide3

Key terms

What do these mean?

Solvent

Solute

Solution

You must be able to use these confidentlySlide4

Separating mixtures

Which mixtures do we need to separate?Slide5

How can we separate mixtures?

Any suggestions?Slide6

Filtration

Example: Water filtrationSlide7

Principles

Insoluble solids separated from

fluid:

Solid particles too large to pass through holes

Fluid

particles small enough to pass through holes.

Solid trapped in filter

Fluid passes through.

N.b

. Fluid =

l

iquid or gasSlide8

Chromatography

Example gas chromatography:Slide9

Principles

Separates mixtures of chemicals that can be dissolved in a liquid medium or

vaporised

in an inert gas medium.

Dissolved or

vaporised

substances rise up the paper or column.

The height to which they rise is dependant on their particle size/mass.

Smallest particles rise further thus separating the constituent parts of the mixture. Slide10

Magnetic separation

E.g. the separation of iron from its ore:Slide11

Principles

Iron in rich ores is magnetic;

Iron ore is crushed.

Iron rich material is attracted to the magnet;

Other parts of the ore containing little or no iron are washed away.

Left with iron that can be purified.

Only works on high grade oresSlide12

Distillation/fractional distillation

E.g. the fractional distillation of crude oilSlide13

Principles

Separates mixtures of two or more liquids;

Each liquid has a different evaporation point;

As the mixture is heated it stays at the boiling point of the lowest liquid until this has boiled off;

It then rises to the boiling point of the next liquid.

Used to distill spirits, components of air and of crude oil.Slide14

Centrifugation

E.g. separating the

Parts of the cell Slide15

Principles

Mixture is spun in a centrifuge at great speeds;

Extreme forces cause suspended solids to separate out;

The amount of force applied and length of time affects the size of the particle that sediment;

The smaller the particle, the higher the force needed.

Liquid on top of the sediment can be decanted off.Slide16

Decanting

E.g. to separate oil and waterSlide17

Principles

Can separate two immiscible liquids;

Liquids that separate out of a mixture because their particle repel each other;

Liquids of different densities.

Can be used to separate solids from liquids, e.g. the supernatant is decanted from a centrifuged sampleSlide18

Evaporation

e.g. salt pansSlide19

Principles

Solid dissolved in a solvent to create a solution;

Solvent evaporates off;

Solute

crystallises

to form a solid that remains behind.Slide20

Electrophoresis

E.g. to separate proteinsSlide21

Principles

An electric current is used to separate components of mixture

Current attracts charged particles along a gel

Lighter particles travel further

Is like chromatography only using charged particles and electricity;

Used to separate proteins;

A very important tool in working out evolutionary relationships between species.Slide22

Mixtures

Heterogeneous

All particles are equally distributed throughout the mixture, e.g. air and blood

Heterogeneous

Particles are not equally mixed throughout but are indifferent concentrations in different areas, e.g. soil, a lake,

a tiramisuSlide23

Particle models

In your groups produce a particle model for one of the above mentioned separation techniques:

Filtration Chromatography

Magnetic separation Fractional distillation

Electrophoresis Evaporation

Decanting Centrifugation

Make sure your diagram shows all steps and shows the make up of the mixture at

the beginning.

Slide24

Questions

Why do we do chromatography?

Give an example of distillation

How might you obtain a dissolved solid from its solvent

Why might filtration be useful?

How might a hospital technician separate blood

?

How does electrophoresis

separate proteins?