The title of this text certainly caught your attention, as it has a name that is not at all common in our daily lives: colloid. Even with this “strange” name, colloids are a type of mixture that is extremely present in everyday life.
You colloids they are heterogeneous mixtures, that is, they have more than one phase, which are always formed by a material called dispersed (substance in smaller quantity) and another called dispersant (substance in greater quantity). An example of dispersant is proteins, and an example of dispersant is Water. It is the size of the disperse that differentiates colloids from a common heterogeneous mixture, such as the union of water and sand.
The curious thing is that colloids, even though they are heterogeneous mixtures, when analyzed with the naked eye, they present a homogeneous appearance. To check the phases present in a colloid, it is necessary to use an electron microscope. Let's get to know the other characteristics of colloids?
- At rest, the dispersed particles do not undergo decantation, that is, they do not settle at the bottom of the container;
- The disperse particles only decant when the colloid is subjected to an ultracentrifuge;
- Disperse cannot be separated from dispersant by means of an ordinary filter, only with an ultrafilter;
- When a beam of light is applied, the scattering particles spread this beam over the entire length of the colloid.
As every colloid has a dispersant and a dispersant, another important characteristic of colloids is the physical state in which we can find them. The determination of the physical state of a colloid is related to the physical state of the dispersant. Thus:
- solid colloid =presents solid dispersant
- liquid colloid = presents liquid dispersant
- gaseous colloid = has gas dispersant
According to the physical state of the dispersant, colloids can be divided into several groups. Are they:
a) Solid colloids
- Solid sun: presents solid dispersion.
Ex.: Sapphire, pearl and ruby.
- Solid emulsion: presents liquid dispersion.
E.g.: Ice cream.
- Gel: presents liquid dispersion.
E.g.: Jelly, cheese and gelatin.
- Solid foam: presents gaseous dispersion.
E.g.: Maria-mole, pumice and Styrofoam.
b) Liquid colloids
- Sun: presents solid dispersion.
Eg toothpaste, gum arabic and paints.
Toothpaste is an example of the sun colloid we use daily
- Emulsion: presents liquid dispersion.
E.g.: mayonnaise, butter, margarine, milk, moisturizing lotion and blood.
Mayonnaise is an emulsion used in many cooking recipes.
- Foam: presents gaseous dispersion.
E.g.: whipped cream, soap foam or detergent.
c) Gaseous colloids
- Solid aerosol: has solid dispersed
Eg smoke coming out of a chimney and dust cloud.
- Liquid aerosol: presents liquid dispersion.
E.g.: fog, spray deodorant and clouds.
By Me. Diogo Lopes Dias
