What is an emulsion defined as?

An emulsion is defined as a dispersion of one phase in another, meaning that it involves the mixing of two immiscible liquids, such as oil and water, where one liquid is dispersed in the form of small droplets throughout the other. This definition highlights the fundamental characteristic of emulsions, which are unstable mixtures that require specific stabilizing agents, such as emulsifiers or surfactants, to maintain their structure and prevent separation over time.

While the other options offer various types of mixtures or states of matter, they do not correctly encapsulate the essence of an emulsion. A homogeneous mixture of oil and water may imply a stable blend, but in reality, without proper emulsifying agents, oil and water will not remain mixed. A solid substance suspended in liquid refers to a suspension, and a liquid substance dissolved in gas describes solutions or aerosols, neither of which accurately characterizes the unique behavior of emulsions. Understanding these distinctions is crucial for recognizing how emulsions function in various applications, particularly in cosmetic formulations, food products, and pharmacology.