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COLLOID


Colloids are a mixture of heterogeneous substances between two or more substances in which colloidal-sized substance particles are uniformly distributed in other substances. Colloid size ranges from 1-100 nm (10-7 - 10-5 cm).
Example: Mayonnaise and paint, mayonnaise is a homogeneous mixture in water and oil and paint is a homogeneous mixture of solids and liquids.

The colloidal system is a mixed form which lies between the solution and the suspension (crude mixture). This colloidal system has distinctive properties that are different from the nature of the solution or suspension.

The colloid state is not a feature of a particular substance because all substances, either solid, liquid, or gaseous, can be made in a colloidal state.

 Colloid is a mixed system of "metastable" (as if stable, but will separate after a certain time). Colloids are different from solutions; Solution is stable.

In colloidal solution in general, there are 2 substances as follows:

- Substance dispersed, ie substances dissolved in colloidal solution

- Substances dispersants, ie solvents in colloidal solutions

 Based on the dispersed phase and dispersion phase a colloid is divided as follows:

The dispersed dispersive phase Colloidal name Example

Gas Gas Not colloid, because the gas mixes homogeneously
Liquid.       Gas.                   Foam,                      soap, waves, whipped cream
Solid.          Gas.                   Solid foam.             Pumice stone, foam mattress
Liquid.       Gas.                   Aerosols liquid.     Spray, mist, hair spray in the air
Liquid.       Liquid.             Emulsion.               Water coconut milk, milk, mayonnaise
Liquid.       Solid.               Gel.                            Butter, gelatin
Solid.          Gas.                  Aerosol Dust,          exhaust gas, smoke
Solid.          Liquid.             Sol.                           Cat, ink
Solid.          Solid.                Sol Pad.                   Soil, glass, mud

 Colloidal properties

A. Tyndall Effect

The Tyndall effect is the scattering of light by colloid solutions, an event in which the path of the colloid rays can be seen because colloid particles can scatter light into all directions.

Examples: sunlight scattered colloidal particles in the sky, until the sky is blue at noon and orange in the afternoon; Dust in the room will be visible if there is light coming in through the gap.

 B. Brownian motion

Brownian motion is the motion of colloid particles in the dispersing medium continuously, because of the collision between the dispersed particle and dispersant. Due to this continuous active motion, the colloid particles do not separate if they are ignored.

 C. Colloid Adsorption

Colloid Adsorption is the absorption of a substance or ion on a colloidal surface. The adsorption properties are used in the process:

1. Bleaching cane sugar.

2. Norit.

3. Purifying water.

Example: colloid between diarrhea drugs and fluid in the intestine that will absorb the germs that cause diarrhea.

 D. Colloid Charge and Electrophoresis

Colloid charges are determined by the ion charge absorbed by the colloidal surface. Electrophoresis is the movement of colloid particles due to the influence of electric fields.

Example: factory chimney fitted with electroplated metal plate in order to coagulate the dust.

 E. Colloid Coagulation

Colloid coagulation is a clumping of colloids due to opposite charge electrolytes.

Example: the dirt on the water is clumped by alum so the water becomes clear.

Factors that cause coagulation:

 Temperature changes.
 Stirring.
Added ions with large loads (eg: alum).
Positive colloid mixing and negative colloid.

F. Emulation

Emulation is a fluid liquid in a liquid medium. To stabilize the solid solution, the colloid is usually added emulsifiers, ie stabilizing agent to stabilize the colloids.

Example: milk is a fatty emulsion in water with casein as emulsifier.

G. Colloid Stability

A. Many colloids should be preserved in colloid form for use.

Example: ice cream, ink, paint.

For that is used another colloid that can form a layer around the colloid. These other colloids are called protective colloids.

Example: gelatin in Fe (OH) sole 3.

 H. Purification of Colloids

To purify colloids is to remove ions that interfere with colloid stability, can be done dialysis. The colloid to be purified is fed into a bag made of a semipermeable membrane that is a membrane that can only pass ionic particles and can not pass through colloidal molecules.

Example: parchment paper, selopan or kolodion.

Making Colloidal System

1. Condensation Method
Preparation of colloidal system by condensation is done by clumping very small particles.

2.How to Dispersion

 Preparation of colloidal system by dispersion is done by minimizing the suspension particles that are too large into colloidal particles, breaking the coarse particles into colloids.


Components of Colloidal Components

1. Continuous phase: more dispersing medium.

2. The discontinuous phase: the dispersed medium is numerous.

Form of Colloidal Particles

1. Circle: eg virus, silica.

2. Trunk: eg virus.

3. Dish: eg globulin in the blood.

4. Fiber: eg cellulose.

Use of the Colloidal System

1. Drugs: ointment, cream, fish oil.

2. Food: ice cream, jelly and gelatin.

3. Cosmetics: hair cream, skin spray, body lotion.

4. Industry: ink, paint.
you can see a video in
https://www.youtube.com/watch?v=FlxOFNXRdV0&t=16s

Komentar

  1. Colloidal and suspense are mixed types, what distinguishes both ?

    BalasHapus
  2. please explain the process making of tahu ?

    BalasHapus

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