Differentiate between Lyophilic and Lyophobic colloids.
Answers
Answer:
Difference between Lyophilic and Lyophobic Colloids
The table below shows the main differences between Lyophilic and Lyophobic Colloids or sols:
Lyophilic Colloids
Lyophobic Colloids
Affinity for the dispersion medium
High affinity, solvent attracting
No affinity, solvent repelling
Preparation
Easy to prepare just by mixing, shaking or heating substance with the dispersion medium
Require special methods to prepare and an electrolyte for stabilisation
Stability
Highly stable and do not coagulate easily on adding electrolytes
Unstable and can easily be coagulated by electrolytes
Reversibility
Reversible sols and can be reconstituted back by adding back the dispersion medium
Irreversible sols and once precipitated, they cannot be reconstituted back just by adding the dispersion medium
Solvation
Highly solvated, dispersed particles are covered by a layer of dispersion medium
Dispersed particles are not solvated
Effect of adding an electrolyte
Require a large amount of electrolyte for coagulation
Get coagulated even on adding a small amount of electrolyte
Viscosity
Highly viscous, more viscous than the medium
Viscosity is the same as that of the dispersion medium
Surface Tension
Generally less than that of the medium
Generally, the same as that of the medium
Examples
Starch, protein, gelatin, gum, etc. dissolved in water
Metals, metal sulphides and oxides
Explanation:
Lyophilic Colloids
In this type of colloidal system, the dispersed phase has a high affinity for the dispersion medium. They are also known as reversible sols due to their ability to reconstitute on adding dispersion medium after separation. They are quite stable and do not coagulate easily. Lyophilic sols are highly solvated and the particles of the dispersed phase are covered by a layer of the dispersion medium. They have the ability to protect lyophobic colloids from electrolytes. They form a protective layer around lyophobic particles. Lyophilic colloids can be coagulated by adding electrolyte or a suitable solvent. Examples of lyophilic colloids are gelatin, gum, starch, protein, rubber, etc.
Lyophobic Colloids
In this type of colloidal system, the dispersed phase does not have an affinity for the dispersion medium so the colloid is not readily formed. They are also known as irreversible sols as they cannot be reconstituted by simply adding dispersion medium after precipitation. They are unstable and can coagulate easily on adding electrolyte, shaking or heating. Lyophobic colloids can be prepared by special methods and require a stabilising agent. Examples of lyophobic colloids are metals and their insoluble compounds such as sulphides.