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 Lyophilic 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:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B and D only
Lyophilic means liquid-loving and lyophobic means liquid-hating; each statement is checked against these two kinds of sol.
(A) They are liquid hating — Incorrect. ‘Lyophilic’ means liquid-loving; liquid hating is lyophobic.
(B) They are reversible sols — Correct. After the medium is evaporated, the sol forms again on remixing with the medium.
(C) They can be easily coagulated — Incorrect. The particles are surrounded by a layer of the solvent, so lyophilic sols are not easily coagulated; easy coagulation is a property of lyophobic sols.
(D) They are quite stable — Correct. Charge and solvation together keep them stable.
(E) They can be prepared by special methods — Incorrect. Special methods (such as Bredig’s arc or chemical methods) are needed for lyophobic sols; lyophilic sols form directly on mixing.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Classification Based on Nature of Interaction between Dispersed Phase and Dispersion Medium – “(i) Lyophilic colloids: The word ‘lyophilic’ means liquid-loving. Colloidal sols directly formed by mixing substances like gum, gelatine, starch, rubber, etc., with a suitable liquid (the dispersion medium) are called lyophilic sols. An important characteristic of these sols is that if the dispersion medium is separated from the dispersed phase (say by evaporation), the sol can be reconstituted by simply remixing with the dispersion medium. That is why these sols are also called reversible sols. Furthermore, these sols are quite stable and cannot be easily coagulated as discussed later.
(ii) Lyophobic colloids: The word ‘lyophobic’ means liquid-hating. Substances like metals, their sulphides, etc., when simply mixed with the dispersion medium do not form the colloidal sol. Their colloidal sols can be prepared only by special methods (as discussed later). Such sols are called lyophobic sols.”