Setting of cement is an

Which of the following is not a surface phenomenon?

Adding soap to water ................

The correct statement$(s)$ about surface properties is(are):
$[A]$ Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system.
$[B]$ The critical temperatures of ethane and nitrogen are $563 \ K$ and $126 \ K$,respectively. The adsorption of ethane will be more than that of nitrogen on the same amount of activated charcoal at a given temperature.
$[C]$ Cloud is an emulsion type of colloid in which liquid is dispersed phase and gas is dispersion medium.
$[D]$ Brownian motion of colloidal particles does not depend on the size of the particles but depends on the viscosity of the solution.

$A$ cube of edge length $1 \ cm$ is divided into smaller cubes of uniform size of length $1 \ nm$. Assuming that no voids are present, the ratio of total surface area of all the cubes of $1 \ nm$ edge length to the surface area of the initial cube is

Sodium thiosulphate is used in photography to :-