Which of the following is a $Gel$?

Explain the purification of colloidal solutions.

Consider the following statements about the Tyndall effect:
$(I)$ It is used to distinguish between a true solution and a colloidal solution.
$(II)$ It is possible only when the refractive indices of the dispersed phase and the dispersion medium differ significantly.
$(III)$ It is observed only when the size of the colloidal particles is much smaller than the wavelength of the light used.
Which of the following statements are correct?

At the critical micelle concentration,the surfactant molecules

What is formed when a lyophilic sol is added to an emulsion?

In which of the following sols are the colloidal particles negatively charged?