Chemistry

Colloids - Tips


- Systems where one or more components have particles with average dimensions less than 1000 nanometers (1 nanometer = 1nm = 10-9m).

- Most colloids look cloudy or opaque.

- Scattered is the least present substance.

- Dispersant: Substance present in larger quantity.

- Colloids have two types of phases: Sol and Gel.

- Sol has solid dispersion and liquid dispersant, acquiring solution aspect in liquid form. An example is glue.

- Gel has solid dispersion and liquid dispersant, acquiring solid aspect. An example is fruit jelly.

- Some terms are used for the study of colloids such as suspension, emulsion, aerosols, hydrosol, foams.

Suspension is a colloidal system of a solid in a liquid (sun). The system is unstable and its particles are almost recognizable under the microscope.

- Emulsion is a colloidal system where the two phases are liquid.

- Aerosols are colloids in the form of dust grains that never settle. We should always dust off objects regularly. These dust grains have a diameter of 1000nm and are in suspension and tend to settle. But in the air, there are some non-settling colloidal-sized dust grains, the aerosols.

- Examples of aerosols are mist, smoke, spray.

Hydrosol is a colloidal system where the dispersing phase is water.

- Foams are colloidal systems. When a gas is bubbled in a liquid, in addition to huge and visible bubbles, bubbles of colloidal dimensions are also formed. For this reason, the foams are colloids.

- Examples of foams are whipped cream, air mixture and sour cream.

- Colloidal pore solid is classified as solid foam, such as pumice, which has air in microscopic colloidal pores.

Table with examples of colloidal mixtures showing dispersion, dispersant and their names:

DISPERSANT

DISPERSE

NAME

EXAMPLE

Gas

Liquid

Liquid aerosol

NEBLINA: water droplets dispersed in air

Gas

Solid

Solid aerosol

SMOKE: solid particles with colloidal dimensions

Liquid

Gas

Foam

SOAP FOAM OR SOAP BUBBLE: In foams, the liquid phase (bubble film) has colloidal dimensions, while gas inside the film is the dispersed one.

Liquid

Liquid

Emulsion

Mayonnaise: Whipped vinegar, oil and egg yolk. The yolk consists of proteins (lecithins) that promote the interaction between vinegar and oil.

Liquid

Solid

Sun

DENTAL CREAM: Colloidal sized particles of antacid and other flavoring substances. All dispersed in aqueous medium

Solid

Gas

Solid foam

PUMPS: The dispersed phase is solid. In solid phase micropores the gas remains

Solid

Liquid

Gel

GELATIN: Protein molecules intertwine and confine water molecules in this network of protein molecules.

Solid

Solid

Solid suspension

COLORED GLASS: Glass is the dispersing phase with dispersed metallic particles.