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Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged.
At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion).[1]
There are two primary mechanisms in play. One is an inward force on the surface molecules causing the liquid to contract.[2][3] Second is a tangential force parallel to the surface of the liquid.[3] This tangential force is generally referred to as the surface tension. The net effect is the liquid behaves as if its surface were covered with a stretched elastic membrane. But this analogy must not be taken too far as the tension in an elastic membrane is dependent on the amount of deformation of the membrane while surface tension is an inherent property of the liquid–air or liquid–vapour interface.[4]
Because of the relatively high attraction of water molecules to each other through a web of hydrogen bonds, water has a higher surface tension (72.8 millinewtons (mN) per meter at 20 °C) than most other liquids. Surface tension is an important factor in the phenomenon of capillarity.
Surface tension has the dimension of force per unit length, or of energy per unit area.[4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to solids.
In materials science, surface tension is used for either surface stress or surface energy.
- ^ "Surface Tension - an overview | ScienceDirect Topics". www.sciencedirect.com. Archived from the original on 2021-12-30. Retrieved 2021-12-30.
- ^ "Surface Tension (Water Properties) – USGS Water Science School". US Geological Survey. July 2015. Archived from the original on October 7, 2015. Retrieved November 6, 2015.
- ^ a b Berry, M V (1971). "The molecular mechanism of surface tension" (PDF). Physics Education. 6 (2): 79–84. Bibcode:1971PhyEd...6...79B. doi:10.1088/0031-9120/6/2/001. S2CID 250797804. Archived (PDF) from the original on 31 December 2021. Retrieved 8 July 2020.
- ^ a b Halliday, David; Resnick, Robert; Krane, Kenneth S. (2010-04-20). Physics, Volume 2. John Wiley & Sons. p. 342. ISBN 978-0-471-40194-0. Archived from the original on 2022-09-22. Retrieved 2021-03-19.