Q.Differentiate between multimolecular and macromolecular colloids.

Multimolecular = aggregate of many small molecules; macromolecular = one very large (polymer) molecule of colloidal size.

Colloids are classified on the basis of the type of particles of the dispersed phase.

Multimolecular colloids:

• Formed when a large number of small atoms or molecules (each individually smaller than colloidal size) aggregate together to form a particle of colloidal dimensions (1-1000 nm).
• The particles are held together by weak van der Waals forces, so these sols are relatively less stable and are usually lyophobic.
• Examples: sulphur sol (aggregates of S8 molecules), gold sol.

Macromolecular colloids:

• Here the substance itself has very large molecules (macromolecules/polymers), and a single molecule is already of colloidal size when dissolved in a suitable solvent.
• These solutions are quite stable and generally lyophilic because they resemble true solutions. …