What term describes unstable physical mixtures of undissolved particles in a liquid?

The term that describes unstable physical mixtures of undissolved particles in a liquid is "suspension." Essentially, suspensions consist of a liquid that contains larger particles that are not dissolved and will settle over time if left undisturbed. This characteristic of being unstable and tending to separate makes suspensions distinct from other types of mixtures.

For instance, in a suspension, the undissolved particles can often be observed within the liquid and will eventually settle at the bottom when the mixture is not agitated. This is unlike an emulsion, which involves two liquids that are mixed together but generally stable due to the emulsifying agent that prevents separation. Solvents are substances that dissolve solutes to create a solution, while colloids represent mixtures where the dispersed particles are small enough to remain suspended within the liquid without settling.

Understanding suspensions is essential in practical applications, as they often require shaking or stirring before use to ensure the even distribution of particles, particularly in cosmetic products where active ingredients may be delivered in this form.