What term is used to describe a mixture containing small, undissolved particles that do not settle out?

The term used to describe a mixture containing small, undissolved particles that do not settle out is a colloid. In a colloid, the particles are typically dispersed throughout the medium but are small enough that gravity does not cause them to settle quickly, leading to a stable mixture.

Colloids exhibit unique properties, such as the Tyndall effect, which is the scattering of light by the dispersed particles. This scattering gives colloids a cloudy appearance, differentiating them from solutions, where the solute is completely dissolved and cannot scatter light, resulting in a clear mixture.

Understanding the characteristics of a colloid is essential in various fields, including chemistry and materials science, as they are commonly encountered in products such as milk, fog, and certain cosmetics.