capillary action

American  

[kap-uh-ler-ee ak-shuhn, kuh-pil-er-ee] / ˈkæp əˌlɛr i ˈæk ʃən, kəˈpɪl ər i /

noun

1. Physics. Also called capillarity. a phenomenon resulting from surface tension and adhesive forces by which a liquid rises or is depressed in a narrow passage or tube, depending on the adhesive or cohesive properties of the liquid.

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capillary action Scientific  

1. The movement of a liquid along the surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid.

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Closer Look

The paper towel industry owes its existence to capillary action, both for the way paper towels soak up liquids and for the trees out of which the towels are made. Molecules of water are naturally attracted to each other and form temporary hydrogen bonds with each other; their attraction for each other on the surface of a liquid, for example, gives rise to surface tension. But they are also attracted in a similar way to other molecules, called hydrophilic molecules, such as those in the sides of a narrow glass tube inserted into a cup of water, in the fibers of a towel, or in the cells of tree tissue known as xylem. These attractive forces can draw water upward against the force of gravity to a certain degree. However, they are not strong enough to draw water from the roots of a tree to its highest leaves. An additional, related force, referred to as transpiration pull, is required to do that. As water evaporates from the tiny pores, or stomata, of leaves, water from adjacent cells is drawn in to replace it by osmosis. Again, intermolecular attractive forces cause other water molecules to follow along, ultimately drawing water up from the roots of the tree.

Example Sentences

They function through capillary action -- the very phenomena by which a spilled liquid on the kitchen table spontaneously wicks into the paper towel used to wipe it up.

From Science Daily • Dec. 11, 2023

But for hummingbirds, which flick their tongues 15 times per second as they drain each flower and quickly move on, capillary action just isn’t fast enough, Rico-Guevara says.

From Science Magazine • May 24, 2023

Fill the reservoir about every three weeks, she says, and capillary action does the rest.

From Seattle Times • Sep. 22, 2022

You depend on a constant supply of tears to keep your eyes lubricated and on capillary action to pump tear fluid away.

From Textbooks • Feb. 14, 2019

Water rises through the clay to meet it, but cannot proceed further because the sand is too loose for further capillary action.

From "1491" by Charles C. Mann