Correct Option
The correct option isColoured gemstone
Explanation
Colloids are heterogeneous mixtures classified based on the physical state of the dispersed phase (the substance being dissolved) and the dispersion medium (the substance in which it is dissolved). A Solid Sol is a specific type of colloid where both the dispersed phase and the dispersion medium are solids.
Option Analysis
- Coloured gemstone Coloured gemstone: Correct. In coloured gemstones (e.g., ruby, sapphire) and coloured glasses, solid particles (often metal oxides or impurities) are dispersed within a solid crystalline or amorphous matrix. Since both phases are solid, this represents a Solid Sol.
- Mud: Incorrect. Mud consists of solid soil or clay particles dispersed in water (liquid). This type of colloid (Solid in Liquid) is simply called a Sol.
- Rubber: Incorrect. Natural rubber (latex) is typically an emulsion (Liquid in Liquid) or a sol depending on its state. Foam rubber involves gas dispersed in a solid, which is classified as a Solid Foam. It does not fit the strict definition of a Solid Sol (Solid in Solid).
- Shaving cream Shaving cream: Incorrect. Shaving cream consists of gas bubbles dispersed in a liquid medium. This classification (Gas in Liquid) is known as a Foam.
Key Takeaway
Solid Sol refers strictly to a colloid where Solid is dispersed in Solid (e.g., Alloys, Coloured Gemstones). This distinguishes it from a Sol (Solid in Liquid) or a Solid Foam (Gas in Solid).