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The
forces
of
attraction
that
exist
between
a
molecule
of
a
liquid
and
all
the
other
molecules
around
it
are
called
forces
of
cohesion.
The
forces
that
exist
between
a
molecule
of
liquid
and
the
surface
of
the
liquid's
container
are
called
adhesive
forces.
When
the
adhesive
forces
are
strong
in
comparison
with
the
cohesive
forces,
we
say
that
the
liquid
"wets"
the
surface
(as
the
water
does
to
the
inner
walls
of
the
straw).
When
this
happens,
the
surface
of
the
water
column
inside
a
tube
is
not
flat:
rather,
it
is
concave,
as
shown
in
the
illustration
When
the
surface
of
the
liquid
is
concave,
the
surface
tension
at
the
wall
of
the
tube
has
an
upward
component,
as
shown
in
the
illustration.
So
the
liquid
will
climb
up
the
tube
until
that
upward
force
reaches
a
state
of
balance
with
the
liquid's
own
weight.
This
lifting
effect
is
called
capillary
action,
or
just
"capillarity".
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