Which type of mixture allows particles to pass through a filter but not a membrane?

The correct choice, colloid, refers to a type of mixture where particles are dispersed throughout a medium, but these particles are larger than those found in a true solution. In a colloid, the particles do not settle out over time, and they cannot be separated through ordinary filtration because they are small enough to pass through filter paper. However, they are too large to pass through a semi-permeable membrane, which distinguishes colloids from solutions.

This property of colloids makes them unique in various applications, including food products, pharmaceuticals, and cosmetics, where stability and dispersion of particles are critical. On the other hand, in a true solution, the solute particles are completely dissolved and can pass through both filters and membranes, while suspensions typically contain larger particles that can settle out or be filtered. Emulsions are a specific type of colloid made up of two immiscible liquids mixed with an emulsifier, but they also fall under the colloid category, reinforcing that the characteristics of colloids allow them to fit this question specifically.