A colloid is a heterogeneous system in which one substance is dispersed as very fine particles in another substance. Their range of diameters is between 1-1000 nm. Based on dispersed phase and dispersion medium, colloids may be of different types like sol, gel, emulsion, aerosol, foam etc. Based on nature of interaction between two phases, sols are divided into Lyophillic and Lyophobic sols. Colloidal solutions exhibit various properties like Tyndall effect, Brownian movement and Electrophoresis. Stability of colloids is due to presence of charge. If somehow charge is removed, the particles will coagulate. Coagulation rate by various solutions containing ions, is decided by Hardy-Schulze rule. Everyday we come across many colloids. The meals we eat, clothes we wear, wooden furniture etc. are largely composed of colloids.

Which of the following statement/s are correct for Lyophilic colloids?

A. They are liquid hating

B. They are reversible sols

C. They can be easily coagulated

D. They are quite stable

E. They can be prepared by special methods

Choose the correct answers from the options given below:

B and D only

The correct answer is option 2. B and D only.

Lyophilic colloids (also called hydrophilic colloids when the medium is water) are colloidal systems where the dispersed phase has a high affinity for the dispersion medium. These colloids form easily when the dispersed substance comes into contact with the solvent.

Examples include starch, proteins, and gelatin in water

A. They are liquid-hating (Incorrect)

The term "lyophilic" literally means "liquid-loving" (from Greek: "lyo" = solvent, "philic" = loving). Lyophilic colloids have a strong attraction for the dispersion medium, whether it’s water or another solvent. This is why they easily form colloidal solutions. In contrast, lyophobic colloids (e.g., metals in water) are "liquid-hating" and require special methods to form colloids. Therefore, statement A is incorrect.

B. They are reversible sols (Correct)

Lyophilic colloids are reversible, meaning if the colloidal solution dries up or the dispersed phase is separated from the medium, the colloid can be reformed by simply mixing the dispersed phase with the dispersion medium again. This is because the affinity between the two is strong, and they easily re-establish their colloidal state

For example, gelatin dissolved in water can be dried, but when mixed with water again, it forms a colloidal solution. Thus, statement B is correct.

C. They can be easily coagulated (Incorrect)

Lyophilic colloids are highly stable due to the strong interactions between the dispersed phase and the dispersion medium. These interactions create a protective layer around the dispersed particles, preventing them from aggregating and precipitating out. Coagulation (the process of aggregation or precipitation) in lyophilic colloids is difficult. They require much stronger conditions (e.g., high concentration of electrolytes) to be coagulated compared to lyophobic colloids. Therefore, statement C is incorrect.

D. They are quite stable (Correct)

Lyophilic colloids are very stable because the dispersed particles have a strong affinity for the dispersion medium. This stability arises due to both:

Solvation: A layer of solvent molecules tightly surrounds the colloidal particles, preventing them from sticking together.

Charge stabilization: Sometimes, the particles carry like charges, creating electrostatic repulsion that prevents aggregation.

As a result, lyophilic colloids remain dispersed and don’t easily coagulate or settle. Therefore, statement D is correct.

E. They can be prepared by special methods (Incorrect)

Lyophilic colloids form easily when the dispersed phase is simply mixed with the dispersion medium. No special preparation methods are needed. For example, proteins dissolve in water to form a colloid by simple stirring. In contrast, lyophobic colloids (e.g., metal sols) require special methods like condensation or dispersion to prepare, because the dispersed phase doesn’t easily interact with the solvent. Therefore, statement E is incorrect.

Hence, the correct option is 2. B and D only.