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Before we begin to explore all the aspects of the various colloids present in surface Chemistry, let us first understand the concept of colloids. What are colloids? Colloids are particles that have a diameter between 1 to 1000 nanometers. It consists of a mixture of particles.
These particles are spread throughout the solution in an even manner. However, the distribution can be uneven sometimes. Colloids will never settle on the bottom of the container where any experiment is being conducted. Instead, they seem to remain dispersed throughout the solution.
Colloids are further classified into various colloids depending upon the size of particles present in the solution. Either these particles are big enough to dissolve macromolecules in them or are composed of macromolecules. They are further classified into macromolecules and micromolecules.
Dispersed Phase and Dispersed Medium
A colloid is said to be a mixture that contains fine particles that are mixed directly into another substance. The fine particles to be mixed in the solution are termed the dispersed phase. On the other hand, the solution in which the particles are mixed is known as the dispersed medium. This solution is also called colloidal dispersion. The solution is called so because the particles of the solution do not settle down at all and are evenly dispersed throughout the solution.
Classification based on Dispersed Medium and Dispersed Phase
A great classification can be made based on the dispersed medium and phase present for the colloids. They are:
Lyophilic
If the dispersed phase has a great attraction or affinity towards the dispersed medium is known as lyophilic colloids. Lyo refers to liquid, and philic refers to loving. This combines to form liquid-loving colloids. Due to their attractive nature towards each other, the dispersed phase and dispersed medium can be readily combined after they are separated from each other. They are also termed intrinsic colloids. Examples of lyophilic colloids are protein, starch, and rubber.
Lyophobic
In literal terms, lyo refers to liquid, and phobic refers to repulsion or hatred. These two combine to form liquid-hating colloids. In case the dispersed phase has no attraction or inclination towards dispersed medium, it is called lyophobic colloids. They do not combine readily. Due to this, many special agents are required to form lyophobic colloids. Many agents are used for the preservation of these colloids. They are also called extrinsic colloids. Examples of lyophobic colloids include gold, silver sols, and so on.
Classification of Colloids
Colloids are classified based on the dispersed medium and dispersed phase that these solutions and particles possess. If there is water as the dispersed medium in these solutions, then these solutions are classified as hydrophilic or hydrophobic. Hydrophilic refers to water-loving particles, whereas water-hating particles or repel water are known as hydrophobic.
Generally, colloids are divided into the following:
- Multimolecular Colloids
- Macromolecular Colloids
- Associated Colloids
Multimolecular Colloids
As discussed earlier, all colloids are based on the size of particles present in the solution. In multimolecular colloids, several particles like atoms and molecules are bonded together to form an aggregate unit of their own. The particles present in the multimolecular colloids have diameters less than 1 nanometer. These colloids are said to be lyophilic.
The mass of all the particles present in the multimolecular colloids is not high. The molecules or atoms present in the multimolecular colloids have weak van der Waals’ forces between them.
Example: Sulphur sol and Gold sol.
Macromolecular Colloids
Macromolecular colloids are made with particles that consist of individual molecules. These molecules form aggregates together to give rise to a colloid whose size is in the colloidal range. This leaves room for no questions related to colloidal solutions. They are lyophobic colloids.
The macromolecular colloids’ molecular mass is very high compared to the other colloids. It consists of very large molecules that have a very high molecular mass. All the molecules used to form macromolecular colloids are large. In macromolecular colloids, there is the presence of a long chain of bonds. Due to this, the van der Waals’ force present in the macromolecular colloids is generally very strong.
Macromolecular examples are various polymers like nylon and starch.
Associated Colloids
These types of colloids are formed by many aggregated ions that are present in a concentrated solution. They also possess high molecular weight due to the presence of ions with more mass.
Associate colloids are lyophobic and lyophilic in nature. As much as the increase in the concentration of the bonds increases, the force of the Van der Waals’ bond increases. A common example of the associate collides is soap sols.
Conclusion
We have considered all the things related to the colloids in the aspect of surface chemistry. We have explored all the details and definitions of colloids. Further, we have discussed the different types of colloids present in surface chemistry. They include micromolecules and macromolecules along with associated colloids.
