The ability of a → liquid to → flow
in a → narrow space, such as a thin
→ tube, without the assistance of, and in opposition to,
external forces like → gravity.
Also called → capillarity. It
occurs because of intermolecular → attractive forces
between the liquid and solid surrounding surfaces. If the diameter of the tube
is sufficiently small, then the combination of → surface tension
(which is caused by → cohesion within the liquid) and
→ adhesion (between the liquid and the
→ container) acts to
lift the liquid. The capillarity of the
liquid is high when adhesion is greater than cohesion.
For example, water in a thin glass tube has strong
→ adhesive forces due to
the hydrogen bonds that form between the water molecules and the
oxygen atoms in the glass wall (made of → silica,
SiO2). In contrast, mercury is characterized by stronger cohesion, and hence its
capillarity is much lower.
See also: → capillary; → action.
