Which of the following best describes a colloid?

A colloid is a mixture in which very small particles are dispersed throughout a substance. The defining characteristic of a colloid is that its particles do not settle out over time, making the mixture stable. This stability allows the colloid to maintain a uniform appearance without the particles separating due to gravity.

In contrast to the other options, which may describe different types of mixtures or solutions:

• Particles in a colloid are typically too small to be seen with the naked eye, meaning that the claim about visibility is not accurate for colloids.

• Colloids cannot be effectively filtered to remove particles, as the particles are generally small enough to pass through filter paper, and this distinguishes them from suspensions, where larger particles will settle out and can be filtered.

• Additionally, while some colloids can be transparent, many are actually opaque or translucent due to the size and concentration of the particles. Thus, being always transparent does not accurately describe colloids either.

The choice that most accurately captures the essence of a colloid is that the particles do not settle out, underscoring their stable nature.