COLLOID

Please watch my video below. :

https://www.youtube.com/watch?v=AMQJFbjqr80&t=56s

Understanding Colloid

 Colloids is a heterogeneous mixture of two or more substances in which particle substances measuring between 1 and 1000 nm are dispersed (distributed) evenly in the medium of another substance. Substances dispersed as particles are called dispersed phases, whereas the substance into the medium disperses the particles called the dispersing medium.

Macroscopically, the colloid looks like a solution, in which a homogeneous mixture of solutes and solvents is formed. However, microscopically, it looks like a suspension, ie a heterogeneous mixture in which each of the mixed components tends to separate each other.

Colloidal Types

The colloidal system can be grouped according to the dispersed phase and the dispersing phase. Based on the dispersed phase, there are three colloid types, among others sol (solid dispersed phase), emulsions (liquid dispersed phase), and froth (gas dispersed phase). Colloids with a gas dispersing phase are called aerosols.

Based on the dispersed and dispersed phases, the colloidal type can be divided into 8 groups as in the following table.

Phase Dispersed	Phase Dispersing	Colloid Type	Colloidal Example
Liquid	Gas	Aerosol	Fog, cloud, hair spray
Solid	Gas	Aerosol	Asa, dust in the air
Gas	Liquid	The foam	Soap scum, whipped cream
Liquid	Liquid	Emulsion	Milk, coconut milk, mayonnaise
Solid	Liquid	Sol	Gold soles, ink, paint, toothpaste
Gas	Solid	Solid foam	Rubber foam, Styrofoam, pumice stone
Liquid	Solid	Solid emulsion (gel)	Margarine, cheese, jelly, pearl
Solid	Solid	Solid soles	Colored glass, black diamond

4. Properties of Colloid

    1. Tyndall effect

When a beam of light is directed to the solution, light is passed on. However, when the light beam is directed to the colloidal system, the light will be scattered. The effect of light scattering by colloidal particles is called the Tyndall effect.

    2. Brownian motion

Microscopically, colloid particles move randomly with a zig-zag pathway in the dispersing medium. This movement is caused by the occurrence of collisions between colloidal particles with the dispersing medium. This random motion of particles is called Brownian motion.

    3. Colloidal load

a. Adsorption

Colloidal particles can absorb other charged and uncharged particles on the surface. The absorption of particles on the surface of these substances is called adsorption.

b.Electrophoresis

Colloidal particles can move in an electric field. This shows that the colloid particles are electrically charged. The movement of colloid particles in electric fields where charged particles move toward the electrode with this opposite charge is called electrophoresis.

    4.Coagulation

Similar electrical charges from colloidal particles help stabilize the colloidal system. If the electrical charge is lost, the colloid particles will become unstable and combine to form clots. The process of forming clumps of these particles is called coagulation. Coagulation can be done in four ways, namely:

1. mechanical

2. using the principle of electrophoresis

3. adding electrolyte

4. add another colloid with opposite charge

Colloid Making

1. Colloid Making by Condensation

In this way, small particles (solute particles) merge into larger particles (colloidal particles), which can be done through:

1. Redox reactions

Example: the manufacture of sulfur sol

2H2S (g) + SO2 (aq) → 3S (colloid) + 2H2O (l)

2. Hydrolysis

Example: making Fe Fe (OH) 3 by adding FeCl3 solution to boiling water

FeCl3 (aq) + 3H2O (l) → Fe (OH) 3 (colloid) + 3HCl (aq)

3. Duplicate decomposition

Example: AgCl sole manufacture

AgNO3 (aq) + HCl (aq) → AgCl (colloid) + HNO3 (aq)

4. Solvent replacement

Example: when saturated calcium acetate solution mixed with alcohol will form a colloid of gel

2. Preparation of Colloid by Dispersion

In this way, large particles (suspension particles) are broken down into smaller particles (colloidal particles), which can be done through:

1. Mechanical way

In this way, the coarse grains are crushed or ground with a colloid grinder up to a certain degree of fineness and then stirred in a dispersing medium. Example: sulfur sole can be made by grinding sulfur powder together with sugar, then the finely ground powder is mixed with water.

2. How to peptisasi

In this way, large particles are broken down with the aid of the perceptifier (breaker). Example: Al (OH) 3 precipitated by AlCl3; Precipitate NiS by H2S; And agar is peppered by water.

3. How to Bredig arc

This method is used to make metal soles such as Ag, Au, and Pt. The metal to be used as a colloid is used as an electrode dipped in the dispersing medium and the two ends of the electrode are electrically jumped