Steel
(
a
form
of
____________________
)
is
one
of
the
____________________
and
more
useful
metals
,
but
its
greatest
disadvantage
is
the
fact
that
it
____________________
with
the
____________________
of
the
air
to
form
____________________
.
Chemists
need
to
____________________
as
much
as
possible
about
the
process
of
rusting
so
they
can
try
to
____________________
it
.
Which
parts
of
the
air
cause
____________________
?
From
our
experience
we
might
well
suggest
that
oxygen
is
____________________
.
If
the
experiment
is
____________________
____________________
and
left
for
several
days
,
it
is
found
that
about
1
/
5
of
the
air
has
been
____________________
____________________
.
The
gas
____________________
in
the
tube
puts
out
a
lighted
splint
.
Therefore
____________________
is
involved
when
____________________
rusts
.
INVESTIGATING
THE
RUST
OF
IRON
1
.
Put
four
clean
test
-
tubes
in
a
____________________
and
____________________
them
A
,
B
,
C
and
D
.
Place
an
iron
____________________
in
each
.
2
.
Add
____________________
water
to
tube
A
(
____________________
air
)
so
that
about
a
____________________
of
the
nail
shows
____________________
the
surface
.
3
.
Add
a
similar
volume
of
____________________
solution
to
tube
B
(
damp
,
____________________
air
)
.
4
.
Place
a
spatula
____________________
of
anhydrous
calcium
chloride
in
tube
C
(
____________________
air
)
and
____________________
tightly
with
a
rubber
____________________
.
The
anhydrous
calcium
chloride
is
a
____________________
agent
which
will
____________________
all
the
water
vapour
from
the
air
in
the
test
-
tube
.
5
.
Boil
5
cm
depth
of
____________________
water
in
a
____________________
with
a
few
____________________
granules
.
6
.
Fill
tube
D
(
water
but
no
air
)
to
well
above
the
top
of
the
nail
with
the
____________________
distilled
water
.
Then
add
a
small
amount
of
____________________
to
float
on
the
surface
to
____________________
out
the
air
.
7
.
Place
the
test
tubes
in
a
safe
place
and
leave
them
for
a
week
.
8
.
After
a
week
examine
each
of
the
test
-
tubes
and
____________________
your
results
.
9
.
Only
the
iron
in
tubes
A
and
B
____________________
.
So
we
can
say
that
oxygen
and
____________________
are
necessary
for
iron
to
rust
.
More
rust
is
formed
in
tube
____________________
than
in
tube
____________________
.
