Check option A

• Peptization is the process of converting a precipitate into a colloidal sol by shaking it with a small amount of electrolyte having a common ion.
• Precipitating a colloidal sol by adding an electrolyte is called coagulation or flocculation, not peptization.

Therefore, A is false.

Check option B

• Freezing point depression is a colligative property and depends on the number of solute particles.
• For the same concentration, a true solution generally has more dispersed particles at molecular/ionic level than a colloidal solution, since colloidal particles are large aggregates and fewer in number.
• Hence, the depression in freezing point is less for a colloidal solution than for a true solution.
• Therefore, the colloidal solution freezes at a higher temperature than the true solution of the same concentration.

Therefore, B is true.

Check option C

• Surfactants form micelles only when their concentration exceeds the critical micelle concentration (CMC).
• The value of CMC is affected by factors like the nature of surfactant, solvent, presence of electrolytes, and temperature.

Therefore, C is true.

Check option D

• Micelles are associated colloids formed by aggregation of surfactant molecules above CMC.
• Macromolecular colloids are colloids in which the dispersed particles themselves are giant molecules, such as proteins, starch, nylon, etc.
• Since micelles are aggregates of small molecules, they are associated colloids, not macromolecular colloids.

Therefore, D is false.

Final answer

The correct statements are: $\boxed{\text{B, C}}$

Comparison with stored correct answer

• Stored correct answer: B, C
• Derived answer: B, C

Hence, the derived answer agrees with the stored correct answer.