C1 P4: Separation methods

• Scheikunde
• Middelbare school
• vwo
• Leerjaar 3

Separation methods leacture 1.  

learning objectives:

• You are able to recognize and describe various separation methods. 
• You can explain the underlying principle for various separation methods. 

Separation methods

Mixtures consist of two or more different substances with different properties. 

Separation method is the technique used for unmixing or separating substances. 

Filtration

The filtering technique, also known as filtration technique, uses a filter to separate solid particles out of liquid. 

(suspension)

Any solid particles left behind on the filter form the residue and everything that goes through the filter form the filtrate. 

The underlying principle of filtration relies upon the difference in particle size.

 

A few examples of filtration:

• A face mask 
• Sand and water mixture

Sedimentation and Decanting 

The underlying principle of sedimentation relies upon a difference in density. 

Gravity makes particles with the greatest density slowly sink to the bottom leaving a clear fluid. Once all the particles have sunk you can then carefully decant the clear fluid. 

Sedimentation is often used with great amounts. 

Examples of sedimentation: 

• Sand and water suspension.
• Oil and water emulsion.  

Centrifugation

In centrifugation, a high-speed rotating motion is used to force substances or particles with a greater density to the bottom. 

It is used to separate suspensions or emulsions. 

Centrifugation is a very sped up version of sedimentation. The underlying principle of centrifugation also relies upon a (small) difference in density 

a few examples of centrifugation: 

• Blood samples in a laboratory. 
• Water in a washing machine. 

Extraction

Extraction or Extract means to "pull out". Extraction uses an extraction agent to separate mixtures of solid substances.  

The underlying principle of extraction relies upon the difference in the solubility of the substances in a particular extraction medium.  

A few examples of extraction: 

• Making tea or coffee  

Adsorption

Adsorption is used to remove a specific substance from a homogeneous mixture. 

This is done using an adsorbent, often activated carbon. 

The underlying principle of adsorption relies upon the difference in adhesion. Adhesion is the ability of substances to stick to each other. 

 

A few examples of adsorption: 

• Norit tablets when u have diarrhea  
• An extraction hood in the kitchen

Extraction          VS          Adsorption 

• Extraction agent (liquid)      vs.        adsorbent (solid)

• solubility            vs.            adhesion 

Homework H3

• Read paragraph  1.4 Separation methods 

• Make exercises : 3, 4, 6a, 7a, b &c 

Separation methods lecture 2. 

learning objectives:

You are able to recognize and describe various separation methods.

You can explain the underlying principle for various separation methods. 

Evaporation

In Evaporation, you heat up a solution containing a solid dissolved in water. 

 Because of the (great) difference in boiling points the water evaporates leaving the solid substance behind.  

the underlying principle of evaporation is the  (great) difference in boiling points. 

An example of evaporation is:

• Kitchen salt mixture

Distillation

Distilling, also known as distillation, is used to separate homogeneous liquid mixtures in which the liquids have different boiling points.

The difference in boiling points of the two liquids needs to be greater then 20°C.  

 

The underlying principle of distillation relies upon the difference in boiling points. 

An example of distillation: 

• separating alcohol and water out of wine 

Chromatography

Chromatography is used to separate dye mixtures. This is done by using a eluent/ liquid (also known as the mobile phase). 

The underlying principle of chromatography relies upon the solubility of the ink with the eluent and the adhesion of the ink to the stationary phase. 

An example of chromatography:

Ink markers. 

Side by side comparison of the different separation methods. 

Method	Principle	Mixture
Filtration	Difference in particle size	Suspension
sedimentation and decanting	Difference in density	Suspension and Emulsion
Centrifugation	Difference in density	Suspension and Emulsion
Extraction	Solubility
Adsorption	Adhesion	Homogeneous solutions and gas mixtures
Evaporation	Difference in boiling points	Solutions
Distillation	Difference in boiling points	Solutions
Chromatography	Difference in solubility in the eluent and adhesion to the stationary phase.	Ink solutions

Homework

• Read paragraph 1.4 Separation methods

• Exercises: Finish the rest of the exercises of paragraph 1.4.