Question

What is the difference between surface tension and interfacial tension?

Answer 1

For surface tension there is solid material on side, such as water, and a air on the other side, such as air.

The transition from water to air forms a surface.

For interfacial tension there is some material A on one side, and a different material on other side.

The transition from one material to another forms an interface.

Answer 2

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In short; surface tension is the property of the liquid in contact with gas phase (usually air). Interfacial tension, on the other hand, is the property between any two substances. Surface and interfacial tension are usually presented by the symbol σ and it is measured by force per unit length.