Definition, Properties, and Types of Colloidal Systems
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Colloidis a mixture of homogeneous (similar) transitional phases to heterogeneous. The mixture is a state between solution and suspension. Macroscopically, colloids appear homogeneous, but actually colloids are classified as heterogeneous mixtures, because the differences in the particles of the two colloidal phases can still be observed and distinguished macroscopically.
Like a sugar solution or a salt solution, the particles may contain more than one molecule but are not large enough to be seen with an ordinary microscope. Particles located within a colloidal size range have a very large surface area compared to the surface area of larger particles with the same volume.
Dispersion system is a system in which one substance is finely divided or dispersed in another substance. Colloid is a dispersion system, because it consists of two phases, namely the dispersed phase and the dispersing phase.
B. COLOID PROPERTIES
The optical properties of colloids are properties that can scatter light. This event is known as Tyndall Effect. In everyday life, this effect can be observed such as in a movie theater where smoke billows will make the projector light brighter, foggy areas (headlights are seen more clearly), sunlight entering through a gap will make dust particles appear more clearly.
When light is passed through a medium containing particles less than 10-9 m, the light beam cannot be detected from the medium. optically clear. When colloidal particles are present, however, some of the light will be scattered, and some will be transmitted at a lower intensity.
The Tyndall effect can be used to observe colloidal particles using a microscope. Since the intensity of light scattering depends on the particle size, the Tyndall effect can also be used to estimate the molecular weight of colloids. Colloidal particles that have a small size, tend to scatter light with short wavelengths. On the other hand, large colloidal particles tend to scatter light with longer wavelengths
This property consists of two movements, namely: thermal movement and motion due to gravity. Colloidal particles move continuously in a broken or zigzag motion known as Brown’s Motion.
Brownian motion occurs due to the unbalanced collision of the molecules of the medium against colloidal particles.
Colloidal particles have a tendency to settle due to the influence of Earth’s gravity. It depends on the density of the particle mass to the medium. If the density of the particles is greater than the dispersion medium, the particles will settle. On the other hand, if the density is smaller, it will float.
The solute particles will diffuse from a solution of high concentration to an area of lower concentration. Diffusion is closely related to Brownian motion, so it can be assumed that molecules or colloidal particles diffuse due to Brownian motion. Colloidal grains diffuse very slowly because of their relatively large particle size.
The physical properties of colloids vary depending on the type of colloid. In hydrophobic colloids, properties such as density, surface tension and viscosity are almost the same as those of the dispersing medium. In hydrophilic colloids due to hydration, the physical properties are very different from those of the medium. The viscosity (viscosity) is greater and the surface tension is relatively small.
Colloidal particles have a charge on their surface due to ionization or absorption of charge. When a charged colloidal particle is placed in an electric field, the particle will move towards one of the electrodes depending on the charge, this process is known as electrophoresis.
Adsorption is the process of attaching a substance to the surface of a solid or liquid. Colloidal particles readily adsorb color. The colloidal particle size is small so that the surface area is large and the adsorption capacity is large.
Coagulation is the clumping of colloidal particles, so that the stability of the colloidal system is lost. The cause of coagulation in colloidal systems is due to the influence of prolonged heating, cooling, mixing of electrolytes, and electrophoresis. Examples of coagulation such as boiling raw eggs in water, cooling hot agar, and purifying river water.
It is a colloid system which is added to another colloid to produce a stable colloid. Like addition gelatin on ice cream, to produce soft ice cream.
C. TYPES OF COLOIDS
Based on the phase of the dispersed substance, the colloid system is divided into 3, namely sol, emulsion, and foam.
Sol, the dispersed phase is solid.
Emulsion, the dispersed phase is liquid.
Foam, the dispersed phase is gas.
TYPES OF COLOIDS
The nature of colloidal mixtures is heterogeneous.
Particle dimensions are less than 1 nm, so a special microscope is needed to observe colloids.
Although colloids are heterogeneous, they cannot be filtered. Like sea water which also contains salt in it, but after filtering it also doesn’t get results.
Stable colloidal systems are caused by attractive forces (London-van der Waals), which cause colloidal particles to aggregate to form aggregates and settle. Also due to repulsive forces caused by the overlapping of electrically charged double layers.
Examples of colloids such as sugar solution, salt solution, alcohol, vinegar, spirit, sea water, gasoline, and clean air.
Colloids are widely used in industry because they do not dissolve homogeneously, are stable, and are not easily damaged.
Industrial uses of colloids:
Many use emulsions and foams, such as foundation, shampoo, facial cleanser, deodorant, and body moisturizer.
Textile dye in the form of a sole makes the color absorb well.
Many drugs are made in the form of insoles.
4. Soap and detergent industry
Soaps and detergents are emulsifiers of dirt and water on clothes that keep clothes clean
5. Food and beverage industry
Foods and beverages such as soy sauce, sauces, milk, mayonnaise, and butter are made in various colloidal forms.
Colloids also have beneficial properties. As :
In cinemas where the lights are brighter, the lampshade is made of colloid so that it can scatter light.
Which is used for DNA identification as well as victims of crime
The red color of cane sugar is adsorbed by diatomaceous earth, by dissolving sugar in water, then flowing the solution through diatomaceous earth.
This is done by adding water with alum or aluminum sulfate which absorbs water pollutants, activated carbon for very high pollution, adding sand as a filter, chlorine as a desiccant, quicklime raises the pH value due to the use of alum.
Mud in water is coagulated using alum
4c. Factory smoke exhaust
Before being discharged into the chimney, the smoke is directed towards the metal charged with high voltage (20-75 kV) so that the surrounding air molecules are ionized. These ions are adsorbed by the smoke so that the smoke has a charge. Then the smoke is pulled by another electrode so that the gas discharged from the chimney is free of smoke.
5a. Emulsifying agents such as soap
5b. Milk is protected by casein which prevents fat clumping
5c. Butter is protected by lecithin which prevents fat clumping
5d. Ice cream protected by gelatin which prevents the formation of sugar crystals or ice cubes.
5e. Ink and paint protected by silicone oil which makes ink and paint last longer
So that’s our discussion in this post about COLLOID, Hopefully it can be useful for friends. If something is still unclear, please ask friends via the comment box below. Thank you for visiting Softilmu, don’t forget to like, follow, and comment, okay? J