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Question
How are colloids classified on the basis of interaction between the dispersed phase and the dispersion medium?
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Solution
The classification of colloids as lyophilic (solvent attracting) and lyophobic (solvent repelling) is based on the nature of the interaction between the dispersed phase and the dispersion medium.
(a) Lyophilic colloids (solvent-loving):
- These substances have a strong affinity for the dispersion medium and readily form colloidal solutions when mixed.
- Examples include proteins, starch, rubber, gelatin, gum, etc.
- These sols are quite stable due to strong attractive forces between dispersed particles and the medium.
- Lyophilic sols are reversible and do not require stabilizers.
(b) Lyophobic colloids (solvent-hating):
- These substances do not readily form sols with the dispersion medium due to lack of affinity.
- Examples include sols of metals like gold, platinum, and insoluble substances like metal sulphides.
- These sols are less stable, require special preparation techniques and stabilizers, and are irreversible.
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| Column I | Column II |
| (i) Protective colloid | (a) \[\ce{FeCl3 + NaOH}\] |
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| (iii) Positively charged colloid | (c) Emulsion |
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