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COLLOID

Team [2]o Agil Haykalo M. Hilmy Fawwazyo Hilda Permatasario Arlisya Tika Affandio Rizkha Faridao Ziyad Syauqi Fawwazi

presents:

Home General Types Importance Properties Preparation

Description

Colloid is a mixture of two heterogene phase of two substance or more, which particles of colloid-sized dispersed into another substance


The Difference of Colloid, Suspension and Solution

Properties Solution Colloid SuspensionType of mixture Homogene Homogene Heterogene

Type of dispersion Molecular dispersion Solid dispersion Solid dispersion

Particles size <1 nm 1nm – 100 nm >100nm

Phase Still homogene Heterogene Heterogene

Filtering Cant be fiiltered` Can only be filtered by permeable paper

Can be filtered by normal paper

Observe Can only be seen using electron microscope

Can only be seen using ultra microscope

Can be seen with normal microscope

Stability Stable, not separated Stable, sometimes separates

Unstable, separated

example Urea solution, sugar solution, salt solution

Milk, cheese, rice Mixture of sand and water

Type of Colloid

Sol (solid dispersed phase)

Solid Sol : sol within solid dispersion mediumexample : alloy, ruby glass, black pearl

Sol : sol within liquid dispersion mediumexample : paint, ink, starch in water, mud

Smoke : sol within gas dispersion mediumexample : dust in the air, particulate in smoke


Emulsion (liquid dispersed phase)

gel : emulsion within solid dispersion mediumexample : jelly, cheese, butter

emulsion : emulsion within liquid dispersion mediumexample : milk, mayonnaise, cream

Liquid aerosol : emulsion within gas dispersion mediumexample : fog, hairspray


Foam (gas dispersed phase)

Solid foam : foam within solid dispersion mediumexample : foam, rubber, styrofoam

Liquid foam : emulsion within liquid dispersion mediumexample : mixed egg-white, soap foam, carbonated drink



Importance of Colloids to Daily Life

Industry Food: cheese, butter, milk, mayonaise Cosmetics: Cream, toothpaste, soap Paint Household: soap, detergent Farming: pesticide, insecticide Medical: penicilin


Just Examples Of Importance of Colloids in daily life . . .

Properties of Colloids

Tyndall effect Brownian movemen

t Electrophoresis Coagulation

Dialysis


Tyndall Effect In 1869, Tyndall observed that when a

beam of light is allowed to pass through a colloidal solution, the path of light gets illuminated. It occurs because light is scattered by particles present in colloidal solution.

Because the first person who observed and announce this triviality to the world is Tyndall. This phenomenon called Tyndall Effect

Look at the bootle...The intensity of the

scattered light

depends on the

difference between

the refractive indices

of the dispersed

phase and the

dispersion medium.

Greater the

difference, greater the

intensity of light.


Brownian Movement There are continuous collisions between the colloidal particles and molecules of dispersion medium which are in constant motion by kinetic energy to colloidal particles by striking it from all sides.

This produced zigzag movement of colloidal particles. The zigzag movement of colloidal particles is known as Brownian movement

Robert Brown


Suppose . . .This black point is the collision’s place

imagine that every blue (or violets?) square is represent a molecule of the dispersion medium

The black straight line is constant motion of colloidal particle, when it collide with molecule of dispersion medium, it will stike make a zigzag movement Footnote: “hope you understand”


Electrophoresis The movement of colloidal particles

under the influence of electric field is called Electrophoresis.

When an electric field is applied across the colloidal solution, the colloidal particles migrate to oppositely charged electrode so they get neutralized. This phenomenon is known as electrophoresis.


Do you see that?

Colloid with positive charge, will migrate to negative charge so they will be neutralized. Just like a magnet


Coagulation

Coagulation is the destabilization of Colloids by neutralizing the electric charge of the dispersed phase particles, which results in aggregation of the colloidal particles.



Dialysis Dialysis is the separation of

colloids and crystalloids, and can be carried out with a suitable semi permeable membrane

Dialysis ussualy used for blood washing tool for malfunction of bill sufferer


Preparation of Colloid

As we know, there are 2 (two) ways to prepare colloid, by:

Condensation

Dispersion Click here

Click here


CONDENSATION

In condensation methods particles of atomic or molecular size are induced to combine to form aggregates of colloidal dimensions.

To achieve this, chemical and physical methods are employed.


Chemical methods Colloidal sols can be prepared by chemical reactions, which involve double

decomposition, oxidation, reduction and hydrolysis. For examples: i) Double decomposition

ii) Oxidation

iii) Reduction

iv) Hydrolysis

Note: Sols of silver halides are prepared by mixing dilute solution of

silver salts with alkali halides in equivalent

amounts. Similarly, silica gel sol is prepared by

mixing dilute solutions of sodium silicate and HCl.

Physical methods Exchange of solvent

In this method, a true solution in mixed with an excess of another solvent in which the solute is insoluble but the solvent is miscible. For e.g., a solution of sulfur in alcohol mixed with excess of water results in a colloidal sol of sulfur.

By excessive cooling

A colloidal sol of ice in an organic solvent such as CHCl3 or ether is obtained by freezing a solution of water in the solvent. The molecules of water, which can no longer be held in solution separately come together to form particles of colloidal size.


Dispersion Methods In dispersion methods, colloidal particles

are obtained by breaking large particles of a substance in the presence of a dispersion medium. Since the sols formed are unstable, they are stabilized by adding stabilizing agents. Some of the dispersion methods are:Mechanical dispersion Electrical disintegrationPeptization.


Mechanical dispersion

In mechanical dispersion, the coarse suspension of the substance is ground in a colloid mill, a ball mill or an ultrasonic disintegrator.

The colloid mill consists of two metal discs, close together and rotating at high speed (7000 revolutions per minute) in opposite directions. By the process of such grinding, the suspension particles are torn off to the colloidal sizes.


Electrical disintegration or Bredig's Arc Method In this method, an electric arc is struck

between electrodes of the metal immersed in the dispersion medium.

Peptization

The process of converting a precipitate into a colloidal sol by shaking it with the dispersion medium, in the presence of a small amount of electrolyte, is called peptization. The electrolyte used is called the peptizing agent.

This method is used to convert a freshly prepared precipitate into a colloidal sol.


Peptization ... In the process of peptization, the precipitate adsorbs

one of the ion of the electrolyte onto its surface. The ion adsorbed on the surface is generally common with those of the precipitate. Adsorption of ion results in the development of positive or negative charge on precipitates and which ultimately break up into colloidal size particles.

Example : a precipitate of silver iodide already formed can be dispersed by the addition of potassium iodide. Here potassium iodide is the peptizing agent.


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