Pennsylvania Esthetician State Board Practice Exam

Which ingredient listed is compatible with both water and oil?

1. Emulsifier

2. Surfactant

3. Solvent

4. Solute

The correct answer is: Emulsifier

An emulsifier is a substance that helps to stabilize a mixture of two immiscible liquids, such as oil and water. It functions by reducing the surface tension at the interface between the two liquids, allowing them to mix more easily. Emulsifiers have both hydrophilic (water-loving) and hydrophobic (oil-loving) properties, which makes them essential in formulations where a stable blend of oil and water is required. This characteristic ensures that the oil does not separate from the water, which is crucial in many cosmetic products like creams and lotions. In contrast, a surfactant primarily helps reduce surface tension, allowing the ingredients to spread more easily but may not always stabilize a mixture of oil and water in the same way an emulsifier does. A solvent is a substance that dissolves a solute, and while it can interact with solutes in both oil and water, it does not inherently create stability between them. Lastly, a solute refers to the substance being dissolved in a solution, which does not have the capability to mix or stabilize both oil and water. Therefore, the unique properties of emulsifiers make them the correct choice for compatibility with both water and oil.