Question

Pumice stone is an example of -

• A. gel
• B. solid sol
• C. foam
• D. sol

Answer 1

The Correct Option is B

Pumice stone is a classic example of a solid sol. To understand why this is the correct answer, let's delve into some key concepts of colloidal chemistry.

Definition of a Solid Sol: A solid sol is a type of colloidal dispersion where solid particles are dispersed in a solid medium. The dispersed phase and the dispersion medium are both solids, but the dispersed phase is present in a colloidal size range.

Pumice stone, which is formed from volcanic activity, has a porous structure. The bubbles trapped within solidified lava result in a structure where solid particles (lava) enclose gas bubbles. Therefore, pumice stone fits the definition of a solid sol.

Let's quickly look at the other options to understand why they aren't correct:

• Gel: A gel is a colloidal system in which a liquid is dispersed in a solid medium, resulting in a semi-rigid structure. Examples include jelly and gelatin.
• Foam: Foam is a colloidal system where gas is dispersed in a liquid or solid. Common examples include shaving foam and Styrofoam.
• Sol: A sol is a colloidal system where solid particles are dispersed in a liquid medium. A common example is paint.

Hence, based on the definition and composition of pumice stone, it is clear that the correct classification for it is solid sol.