____________________
is
the
most
abundant
____________________
on
Earth
,
but
it
is
expensive
,
largely
because
of
the
amount
of
____________________
used
in
the
extraction
process
.
Aluminium
ore
is
called
bauxite
(
____________________
)
.
The
bauxite
is
purified
to
yield
a
white
powder
?
aluminium
oxide
(
also
known
as
____________________
)
?
from
which
aluminium
can
be
extracted
.
The
extraction
is
done
by
____________________
,
but
first
the
aluminium
oxide
must
be
melted
so
that
electricity
can
pass
through
it
.
However
,
aluminium
oxide
has
a
very
high
melting
point
(
over
____________________
)
so
it
would
be
____________________
to
melt
it
.
Instead
,
it
is
dissolved
in
molten
____________________
?
an
aluminium
compound
with
a
____________________
melting
point
than
aluminium
oxide
.
The
use
of
molten
cryolite
as
a
solvent
____________________
some
of
the
energy
costs
involved
in
extracting
aluminium
by
allowing
the
____________________
in
aluminium
oxide
to
move
freely
at
a
lower
____________________
.
