What defines an emulsion?

An emulsion is specifically defined as a mixture where one liquid is dispersed throughout another liquid with which it does not readily mix, resulting in a stable combination. This process is typically facilitated by an emulsifier, which helps maintain the stability of the mixture by reducing surface tension between the two liquids.

In this context, the answer signifies that the defining characteristic of an emulsion is the suspension of one liquid within another, creating a homogeneous system despite the inherent immiscibility of the two liquids involved. This is common in many beauty products, including lotions, creams, and certain hair color formulas, where oils and water-based components are blended.

Other options do not accurately represent what an emulsion entails. For example, a mixture that refuses to settle might refer to several different types of mixtures, but does not specifically denote the unique characteristics of emulsions. Similarly, a solid dissolved in a liquid refers to solutions, not emulsions, and a gaseous mixture would describe interactions among gases rather than liquids. Therefore, the correct choice encapsulates the precise nature of emulsions in chemical terms.