Solid solution is a type of mixture where two or more substances are mixed together in the solid state. The solute is the substance that is present in smaller amounts, and the solvent is the substance that is present in larger amounts. In most cases, the solute and solvent are both solids. However, there are some cases where the solute can be a gas.

Pumice stone is an example of a solid solution where the solute is a gas. Pumice is a volcanic rock that is formed when lava with a high concentration of gas is rapidly cooled and solidified. The gas bubbles get trapped in the solidified lava, resulting in a porous and lightweight rock. The gas in the pumice stone is the solute, and the solidified lava is the solvent.

Explanation:
1. Concept of solid solution: A solid solution is a homogeneous mixture of two or more substances in the solid state. The solute particles are dispersed throughout the solvent particles in a solid solution. In most cases, the solute and solvent are both solids. However, there are some exceptions where the solute can be a gas.

2. Example of solid solution with a gas solute: Pumice stone is an example of a solid solution where the solute is a gas. Pumice is a type of volcanic rock that is formed during volcanic eruptions. When lava with a high concentration of gas is ejected from a volcano, it cools rapidly and solidifies before the gas can escape. This rapid cooling and solidification trap the gas bubbles within the solidified lava, resulting in the formation of a porous and lightweight rock known as pumice.

3. Gas solute in pumice stone: The gas present in the pumice stone, such as carbon dioxide or water vapor, is the solute in the solid solution. The solidified lava acts as the solvent, holding the gas bubbles within its structure. The gas bubbles make pumice stone highly porous and lightweight, which gives it unique properties such as low density and high porosity.

4. Characteristics of pumice stone: Pumice stone is known for its abrasive properties and is commonly used as a scrubbing and exfoliating agent. Its porous and lightweight nature makes it float on water. Pumice stone is also used in horticulture and construction due to its ability to retain water and provide good drainage in soils and concrete mixtures.

In summary, pumice stone is an example of a solid solution where the solute is a gas. The gas bubbles trapped within the solidified lava act as the solute, while the solidified lava acts as the solvent. Pumice stone's unique properties, such as low density and high porosity, are a result of this solid solution.