Which term best fits the definition: a mixture of one or more substances (solutes) that cannot be separated by filtration or ordinary setting?

• A. Suspension
• B. Colloid
• C. Emulsion
• D. Solution

Answer: (D)

The main idea tested is how a mixture behaves at the particle level when you try to separate its components. A solution is a homogeneous blend in which the solute dissolves in the solvent so completely that the individual particles are too small to be removed by ordinary filtration or by letting the mixture sit. Because the dissolved particles are at the molecular level, you can’t see them, and they don’t settle out over time, so simple filtration or gravity separation won’t separate the components. Salt in water is a classic example: the salt dissolves and the mixture looks uniform throughout.

This distinguishes it from a suspension, which contains larger particles that can settle to the bottom and be separated by filtration, and from a colloid or an emulsion, where the particles or droplets are dispersed but not dissolved and require special methods to separate.