Which term best describes an unstable physical mixture of two or more immiscible substances?

The term that best describes an unstable physical mixture of two or more immiscible substances is "emulsion." An emulsion occurs when two liquids that do not naturally mix, such as oil and water, are combined in a way that allows them to exist together temporarily.

In the case of an emulsion, one liquid is dispersed in the other, but the mixture remains unstable, meaning that over time, the two phases will separate back into their original components unless stabilized by an emulsifier, which helps maintain the mixture's uniformity for a longer period.

Understanding emulsions is essential in cosmetology, especially when formulating creams and lotions, where the ability to incorporate oils into a water-based solution is critical for performance and aesthetics. This knowledge helps cosmetologists create products that enhance the skin or hair's appearance and texture.

The other terms provided do not accurately capture this specific characteristic. A solution is a homogeneous mixture where one substance is completely dissolved in another. A suspension is a heterogeneous mixture where solid particles are dispersed in a liquid but can settle over time. A mixture is a more general term that can encompass various combinations of substances without specifying their interaction type.