Washington Esthetician State Board Practice Exam

How is a solution best defined in cosmetic chemistry?

1. A mixture of water and oils

2. A blended mixture of two or more substances

3. A solid suspended in liquid

4. A gas mixed with a liquid

The correct answer is: A blended mixture of two or more substances

A solution in cosmetic chemistry is best defined as a blended mixture of two or more substances. This definition reflects the key characteristic of a solution, which is that the substances (the solute and the solvent) are homogeneously mixed at a molecular level. When two or more substances are combined and interact to form a single phase, it results in a stable mixture where the individual components are not easily distinguishable. In the context of cosmetic products, this can include an array of mixtures such as water with various active ingredients dissolved in it, or even alcohol-based solutions that carry fragrances. The ability of a solution to maintain uniformity is crucial in the formulation of cosmetics, ensuring efficacy and stability throughout the product's life. The other options focus on specific types of mixtures rather than solutions in general. For example, a mixture of water and oils does not result in a true solution, as oils do not dissolve in water and tend to separate, forming an emulsion instead. Similarly, a solid suspended in liquid describes a suspension rather than a solution, where the solid particles can settle over time. Lastly, a gas mixed with a liquid may create an aerated liquid, but it still does not encapsulate the broad definition of a solution in cosmetic chemistry.