capillary action
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The cohesion between a liquid and a solid results
in the liquid surface curving near the solid, to meet it at a definite
angle. Water curves upward against glass, and the force of cohesion
is exerted along the water surface, tending to lift it. The lifting
force is proportional to the circumference of the water surface; in
a narrow tube this force becomes powerful enough to lift a tall column
of water.
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Also called capillarity, the name given to various surface
tension phenomena in which the surface of a liquid
confined in a narrow-bore tube rises above or is depressed below the level
it would have if it were unconfined. When the attraction between the molecules
of the liquid and those of the tube exceeds the combined effects of gravity
and the attractive forces within the liquid, the liquid rises in the tube
until equilibrium is restored.
Capillary action is very important in nature, particularly in the transport
of fluids in plants (see xylem) and through
the soil. Related entry
capillary
constant Related category
PROPERTIES
OF MATTER
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