What characterizes a suspension?

A suspension is characterized by the presence of small particles that are dispersed throughout a gas or liquid. These particles do not dissolve but rather remain suspended, meaning that they can eventually settle out over time if left undisturbed. This is an important distinction because suspensions are not uniform in composition; their properties can change upon standing.

When the particles are described as being small, it implies that they can create a cloudy appearance in the liquid or gas medium. As time passes, gravity often causes these particles to aggregate and settle at the bottom of the container, which is a defining feature of suspensions, differentiating them from other types of mixtures such as solutions or colloids, where the particles remain evenly distributed and do not separate.

The other options refer to characteristics of other types of mixtures. For example, having all particles remain mixed or being a homogeneous mixture relates more to solutions, while the ability to separate over time is not a characteristic of solutions or colloids.