A certain skin lotion is a fine mixture of water and various oils. This lotion is cloudy and cannot be separated into oil and water by filtration or centrifuge. What type of mixture is it?

Question

anonymous · Answer

What you're describing is an emulsion, which is a mixture of two or more normally immiscible liquids.  The interaction is stabilized by a surfactant, which can interact with both liquids.

A good everyday example of this is oil, water, and ordinary dish soap.  Oil (a hydrophobic liquid) and water (a polar liquid) can mix together with the addition of something that can interact with both the oil and the water.  I this case, dish soap has a hydrophobic region that can interact with the oil, and a hydrophilic region that can interact with the water.