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How does surface tension cause a liquid to resist an increase in surface area?

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differential manometer, Torricellian barometer, and siphon — fluid mechanics Figure 1: Schematic representations of (A) a differential manometer, (B) a Torricellian barometer, and (C) a siphon.

Surface tension causes a liquid to resist an increase in surface area because of the cohesive forces acting between its molecules.12

Within the bulk of a liquid, molecules are attracted equally in all directions by their neighbors. However, molecules at the surface experience an imbalance: they are attracted inward by the molecules below them but lack equivalent neighbors above them. To increase the surface area, molecules must be moved from the interior to the surface, which requires overcoming these inward attractive forces.13

This process requires the input of work or energy to break intermolecular links and bring more molecules to the interface. Because this energy is associated with the surface, the liquid naturally tends to minimize its surface area to reach a state of lower energy, often resulting in spherical shapes for drops. Consequently, the surface behaves as if it were a stretched elastic membrane, resisting any deformation that would expand its area.132