https://doi.org/10.1351/goldbook.A00302
The property of surface activity is usually due to the fact that the molecules of the substance are amphipathic or @A00303@, meaning that each contains both a @H02906@ and a hydrophobic (@L03572@) group. This assumes that one of the two phases is aqueous, and the other non-aqueous. If both are non-aqueous (e.g. oil/air), molecules containing organophilic and organophobic groups may be amphipathic and surface active.