NCERT Textbook - Materials : Metals And Non-Metals Class 8 Notes | EduRev

General Science(Prelims) by IRS Divey Sethi

Created by: Divey Sethi

Class 8 : NCERT Textbook - Materials : Metals And Non-Metals Class 8 Notes | EduRev

 Page 1


MATERIALS : METALS AND NON-METALS
MATERIALS : METALS AND NON-METALS
Y
ou are familiar with a number of
materials like iron, aluminium,
copper, etc. Some materials have
been given in Table 4.1.
similar change if we try to beat a
wood log ?
Let us find out.
Activity 4.1
Take a small iron nail, a coal piece,
a piece of thick aluminium wire and
a pencil lead. Beat the iron nail with
a hammer (Fig. 4.1). (But take care
that you don’t hurt yourself in the
process). Try to hit hard. Hit hard
Table 4.1 : Appearance and
Hardness of materials
Object Appearance Hardness
/Material (Shiny/Dull) (Very hard/
Not very
hard)
Iron
Coal
Sulphur
Aluminium
Copper
-----
Can you name the materials which
are metals? The rest of the materials in
Table 4.1 are non-metals. Metals can be
distinguished from non-metals on the
basis of their physical and chemical
properties. Recall that lustre and
hardness are physical properties.
4.1Physical Properties of
Metals and Non-metals
Have you ever seen a blacksmith beating
an iron piece or an article made up of
iron, like a spade, a shovel, an axe? Do
you find a change in the shape of  these
articles on beating? Would you expect a
Table 4.2 Malleability of Materials
Object/ Change in Shape
Material (Flattens/Breaks
into pieces)
Iron nail
Coal piece
Aluminium wire
Pencil lead
also the aluminium wire. Then
repeat the same kind of treatment
on the coal piece and pencil
lead. Record your observations in
Table 4.2.
Fig. 4.1 : Beating an iron nail with hammer
© NCERT
not to be republished
Page 2


MATERIALS : METALS AND NON-METALS
MATERIALS : METALS AND NON-METALS
Y
ou are familiar with a number of
materials like iron, aluminium,
copper, etc. Some materials have
been given in Table 4.1.
similar change if we try to beat a
wood log ?
Let us find out.
Activity 4.1
Take a small iron nail, a coal piece,
a piece of thick aluminium wire and
a pencil lead. Beat the iron nail with
a hammer (Fig. 4.1). (But take care
that you don’t hurt yourself in the
process). Try to hit hard. Hit hard
Table 4.1 : Appearance and
Hardness of materials
Object Appearance Hardness
/Material (Shiny/Dull) (Very hard/
Not very
hard)
Iron
Coal
Sulphur
Aluminium
Copper
-----
Can you name the materials which
are metals? The rest of the materials in
Table 4.1 are non-metals. Metals can be
distinguished from non-metals on the
basis of their physical and chemical
properties. Recall that lustre and
hardness are physical properties.
4.1Physical Properties of
Metals and Non-metals
Have you ever seen a blacksmith beating
an iron piece or an article made up of
iron, like a spade, a shovel, an axe? Do
you find a change in the shape of  these
articles on beating? Would you expect a
Table 4.2 Malleability of Materials
Object/ Change in Shape
Material (Flattens/Breaks
into pieces)
Iron nail
Coal piece
Aluminium wire
Pencil lead
also the aluminium wire. Then
repeat the same kind of treatment
on the coal piece and pencil
lead. Record your observations in
Table 4.2.
Fig. 4.1 : Beating an iron nail with hammer
© NCERT
not to be republished
Fig. 4.2 : Electric tester
Where do you find the use of
aluminium and copper wires? Have you
seen wires of coal? Definitely not!
The property of metal by which it can
be drawn into wires is called ductility.
Have you ever noticed the difference
in sound on dropping an iron sheet/
plate, a metal coin, and a piece of coal
on the floor? If not, you can try it now.
Do you note any difference in the sound
produced?
Oh! The meaning of recalling
our experiences and then of
this activity was to show that
metals are good conductors of
heat and electricity. We learnt
this in Class VI.
MATERIALS : METALS AND NON-METALS 45
You saw that the shape of the iron nail
and the aluminium wire changed on
beating. If they were beaten harder these
could be changed into sheets. You might
be familiar with silver foil used for
decorating sweets. You must also be
familiar with the aluminium foil used for
wrapping food. The property of metals by
which they can be beaten into thin sheets
is called malleability. This is a
characteristic property of metals. As you
must have noticed, materials like coal and
pencil lead do not show this property. Can
we call these as metals?
Can you hold a hot metallic pan which
is without a plastic or a wooden handle
and not get hurt? Perhaps not! Why? Try
to list some other experiences in which a
wooden or plastic handle protects you
from being hurt while handling hot
things. On the basis of these experiences
what can you say about the conduction
of heat by wood and plastic?
You must have seen an electrician
using his screw driver. What kind of
handle does it have? Why?
Let us find out.
Activity 4.2
Recall how to make an electric
circuit to test whether electricity can
pass through an object or not
(Fig. 4.2). You might have performed
the activity with various objects in
Class VI. Now, repeat the activity
with the materials mentioned in
Table 4.3. Observe and group these
materials into good conductors and
poor conductors.
Table 4.3 : Electrical
conductivity of materials
S.No. Materials Good Conductor /
Poor
Conductor
1. Iron rod/nail
2. Sulphur
3. Coal piece
4. Copper wire
You observe that iron rod, nail and
copper wire are good conductors while
rolled sulphur piece and coal piece are
poor conductors.
© NCERT
not to be republished
Page 3


MATERIALS : METALS AND NON-METALS
MATERIALS : METALS AND NON-METALS
Y
ou are familiar with a number of
materials like iron, aluminium,
copper, etc. Some materials have
been given in Table 4.1.
similar change if we try to beat a
wood log ?
Let us find out.
Activity 4.1
Take a small iron nail, a coal piece,
a piece of thick aluminium wire and
a pencil lead. Beat the iron nail with
a hammer (Fig. 4.1). (But take care
that you don’t hurt yourself in the
process). Try to hit hard. Hit hard
Table 4.1 : Appearance and
Hardness of materials
Object Appearance Hardness
/Material (Shiny/Dull) (Very hard/
Not very
hard)
Iron
Coal
Sulphur
Aluminium
Copper
-----
Can you name the materials which
are metals? The rest of the materials in
Table 4.1 are non-metals. Metals can be
distinguished from non-metals on the
basis of their physical and chemical
properties. Recall that lustre and
hardness are physical properties.
4.1Physical Properties of
Metals and Non-metals
Have you ever seen a blacksmith beating
an iron piece or an article made up of
iron, like a spade, a shovel, an axe? Do
you find a change in the shape of  these
articles on beating? Would you expect a
Table 4.2 Malleability of Materials
Object/ Change in Shape
Material (Flattens/Breaks
into pieces)
Iron nail
Coal piece
Aluminium wire
Pencil lead
also the aluminium wire. Then
repeat the same kind of treatment
on the coal piece and pencil
lead. Record your observations in
Table 4.2.
Fig. 4.1 : Beating an iron nail with hammer
© NCERT
not to be republished
Fig. 4.2 : Electric tester
Where do you find the use of
aluminium and copper wires? Have you
seen wires of coal? Definitely not!
The property of metal by which it can
be drawn into wires is called ductility.
Have you ever noticed the difference
in sound on dropping an iron sheet/
plate, a metal coin, and a piece of coal
on the floor? If not, you can try it now.
Do you note any difference in the sound
produced?
Oh! The meaning of recalling
our experiences and then of
this activity was to show that
metals are good conductors of
heat and electricity. We learnt
this in Class VI.
MATERIALS : METALS AND NON-METALS 45
You saw that the shape of the iron nail
and the aluminium wire changed on
beating. If they were beaten harder these
could be changed into sheets. You might
be familiar with silver foil used for
decorating sweets. You must also be
familiar with the aluminium foil used for
wrapping food. The property of metals by
which they can be beaten into thin sheets
is called malleability. This is a
characteristic property of metals. As you
must have noticed, materials like coal and
pencil lead do not show this property. Can
we call these as metals?
Can you hold a hot metallic pan which
is without a plastic or a wooden handle
and not get hurt? Perhaps not! Why? Try
to list some other experiences in which a
wooden or plastic handle protects you
from being hurt while handling hot
things. On the basis of these experiences
what can you say about the conduction
of heat by wood and plastic?
You must have seen an electrician
using his screw driver. What kind of
handle does it have? Why?
Let us find out.
Activity 4.2
Recall how to make an electric
circuit to test whether electricity can
pass through an object or not
(Fig. 4.2). You might have performed
the activity with various objects in
Class VI. Now, repeat the activity
with the materials mentioned in
Table 4.3. Observe and group these
materials into good conductors and
poor conductors.
Table 4.3 : Electrical
conductivity of materials
S.No. Materials Good Conductor /
Poor
Conductor
1. Iron rod/nail
2. Sulphur
3. Coal piece
4. Copper wire
You observe that iron rod, nail and
copper wire are good conductors while
rolled sulphur piece and coal piece are
poor conductors.
© NCERT
not to be republished
SCIENCE 46
Have you seen wooden bells in
temples? Can you give reason?
The things made of metals produce
ringing sound when struck hard.
Suppose you have two boxes similar in
appearance, one made of wood and the
other of metal. Can you tell which box
is made of metal by striking both the
boxes?
Since metals produce ringing
sounds, they are said to be sonorous.
The materials other than metals are not
sonorous.
After performing the above activities,
we can say that some materials are hard,
lustrous, malleable, ductile, sonorous
and good conductors of heat and
electricity. The materials which
generally posses these properties are
called metals. The examples of metals
are iron, copper, aluminium, calcium,
magnesium, etc. In contrast, materials
like coal and sulphur are soft and dull
in appearance. They break down into
powdery mass on tapping with hammer.
They are not sonorous and are poor
conductors of heat and electricity. These
materials are called non-metals. The
examples of non-metals are sulphur,
carbon, oxygen, phosphorus, etc.
which rust is formed. You had also
performed  in Class VII an activity of
burning a magnesium ribbon in air. You
had learnt that in both the processes
oxide formation takes place. Complete
the following reactions of iron and
magnesium with oxygen.
Iron (Fe) + Oxygen (O
2
) + Water (H
2
O) ? ?
Magnesium (Mg) + Oxygen (O
2
)  ? ?
Activity 4.3
Let us check the nature of rust
formed as a result of the reaction
between iron, oxygen and water.
Collect a spoonful of rust and
dissolve it in a very little  amount of
water. You will find that the rust
remains suspended in water. Shake
the suspension well. Test the
solution with red and blue litmus
papers (Fig. 4.3). What do you
observe? Is the solution acidic or
basic?
Metals like sodium and potassium are
soft and can be cut with a knife.
Mercury is the only metal which is
found in liquid state at room
temperature. These are exceptions.
4.2Chemical Properties of
Metals and Non-metals
A. Reaction with Oxygen
You are familiar with the phenomenon
of rusting of iron. Recall the reaction by
Rust
Rust
suspension
Red litmus
paper
Fig. 4.3 : Testing the nature of rust
© NCERT
not to be republished
Page 4


MATERIALS : METALS AND NON-METALS
MATERIALS : METALS AND NON-METALS
Y
ou are familiar with a number of
materials like iron, aluminium,
copper, etc. Some materials have
been given in Table 4.1.
similar change if we try to beat a
wood log ?
Let us find out.
Activity 4.1
Take a small iron nail, a coal piece,
a piece of thick aluminium wire and
a pencil lead. Beat the iron nail with
a hammer (Fig. 4.1). (But take care
that you don’t hurt yourself in the
process). Try to hit hard. Hit hard
Table 4.1 : Appearance and
Hardness of materials
Object Appearance Hardness
/Material (Shiny/Dull) (Very hard/
Not very
hard)
Iron
Coal
Sulphur
Aluminium
Copper
-----
Can you name the materials which
are metals? The rest of the materials in
Table 4.1 are non-metals. Metals can be
distinguished from non-metals on the
basis of their physical and chemical
properties. Recall that lustre and
hardness are physical properties.
4.1Physical Properties of
Metals and Non-metals
Have you ever seen a blacksmith beating
an iron piece or an article made up of
iron, like a spade, a shovel, an axe? Do
you find a change in the shape of  these
articles on beating? Would you expect a
Table 4.2 Malleability of Materials
Object/ Change in Shape
Material (Flattens/Breaks
into pieces)
Iron nail
Coal piece
Aluminium wire
Pencil lead
also the aluminium wire. Then
repeat the same kind of treatment
on the coal piece and pencil
lead. Record your observations in
Table 4.2.
Fig. 4.1 : Beating an iron nail with hammer
© NCERT
not to be republished
Fig. 4.2 : Electric tester
Where do you find the use of
aluminium and copper wires? Have you
seen wires of coal? Definitely not!
The property of metal by which it can
be drawn into wires is called ductility.
Have you ever noticed the difference
in sound on dropping an iron sheet/
plate, a metal coin, and a piece of coal
on the floor? If not, you can try it now.
Do you note any difference in the sound
produced?
Oh! The meaning of recalling
our experiences and then of
this activity was to show that
metals are good conductors of
heat and electricity. We learnt
this in Class VI.
MATERIALS : METALS AND NON-METALS 45
You saw that the shape of the iron nail
and the aluminium wire changed on
beating. If they were beaten harder these
could be changed into sheets. You might
be familiar with silver foil used for
decorating sweets. You must also be
familiar with the aluminium foil used for
wrapping food. The property of metals by
which they can be beaten into thin sheets
is called malleability. This is a
characteristic property of metals. As you
must have noticed, materials like coal and
pencil lead do not show this property. Can
we call these as metals?
Can you hold a hot metallic pan which
is without a plastic or a wooden handle
and not get hurt? Perhaps not! Why? Try
to list some other experiences in which a
wooden or plastic handle protects you
from being hurt while handling hot
things. On the basis of these experiences
what can you say about the conduction
of heat by wood and plastic?
You must have seen an electrician
using his screw driver. What kind of
handle does it have? Why?
Let us find out.
Activity 4.2
Recall how to make an electric
circuit to test whether electricity can
pass through an object or not
(Fig. 4.2). You might have performed
the activity with various objects in
Class VI. Now, repeat the activity
with the materials mentioned in
Table 4.3. Observe and group these
materials into good conductors and
poor conductors.
Table 4.3 : Electrical
conductivity of materials
S.No. Materials Good Conductor /
Poor
Conductor
1. Iron rod/nail
2. Sulphur
3. Coal piece
4. Copper wire
You observe that iron rod, nail and
copper wire are good conductors while
rolled sulphur piece and coal piece are
poor conductors.
© NCERT
not to be republished
SCIENCE 46
Have you seen wooden bells in
temples? Can you give reason?
The things made of metals produce
ringing sound when struck hard.
Suppose you have two boxes similar in
appearance, one made of wood and the
other of metal. Can you tell which box
is made of metal by striking both the
boxes?
Since metals produce ringing
sounds, they are said to be sonorous.
The materials other than metals are not
sonorous.
After performing the above activities,
we can say that some materials are hard,
lustrous, malleable, ductile, sonorous
and good conductors of heat and
electricity. The materials which
generally posses these properties are
called metals. The examples of metals
are iron, copper, aluminium, calcium,
magnesium, etc. In contrast, materials
like coal and sulphur are soft and dull
in appearance. They break down into
powdery mass on tapping with hammer.
They are not sonorous and are poor
conductors of heat and electricity. These
materials are called non-metals. The
examples of non-metals are sulphur,
carbon, oxygen, phosphorus, etc.
which rust is formed. You had also
performed  in Class VII an activity of
burning a magnesium ribbon in air. You
had learnt that in both the processes
oxide formation takes place. Complete
the following reactions of iron and
magnesium with oxygen.
Iron (Fe) + Oxygen (O
2
) + Water (H
2
O) ? ?
Magnesium (Mg) + Oxygen (O
2
)  ? ?
Activity 4.3
Let us check the nature of rust
formed as a result of the reaction
between iron, oxygen and water.
Collect a spoonful of rust and
dissolve it in a very little  amount of
water. You will find that the rust
remains suspended in water. Shake
the suspension well. Test the
solution with red and blue litmus
papers (Fig. 4.3). What do you
observe? Is the solution acidic or
basic?
Metals like sodium and potassium are
soft and can be cut with a knife.
Mercury is the only metal which is
found in liquid state at room
temperature. These are exceptions.
4.2Chemical Properties of
Metals and Non-metals
A. Reaction with Oxygen
You are familiar with the phenomenon
of rusting of iron. Recall the reaction by
Rust
Rust
suspension
Red litmus
paper
Fig. 4.3 : Testing the nature of rust
© NCERT
not to be republished
MATERIALS : METALS AND NON-METALS 47
Fig. 4.4 (a) : Burning of sulphur powder
Improvised
deflagrating
spoon
Now recall  the activity of burning
magnesium ribbon. The ash obtained
on burning magnesium ribbon is
dissolved in water and tested for its
acidic / basic nature.
Is the solution acidic or basic? How
do you ascertain this?
You must have observed that the red
litmus turns blue. So, oxide of magnesium
is also basic in nature. In general, metallic
oxides are basic in nature.
Let us now observe the reaction of
non-metals with oxygen.
Activity 4.4
(To be demonstrated by the teacher
in the class)
Take a small amount of powdered
sulphur in a deflagrating spoon and
heat it. If deflagrating spoon is not
available, you may take a metallic cap
of any bottle and wrap a metallic wire
around it and give it the shape
shown in Fig. 4.4 (a).
As soon as sulphur starts burning,
introduce the spoon into a gas jar/
glass tumbler [Fig. 4.4 (a)]. Cover the
tumbler with a lid to ensure that
the gas produced does not escape.
Remove the spoon after some time.
Add a small quantity of water into
the tumbler and quickly replace the
lid. Shake the tumbler well. Check
the solution with red and blue
litmus papers [Fig. 4.4 (b)].
When a copper vessel is exposed to
moist air for long, it acquires a dull
green coating. The green material is
a mixture of copper hydroxide
(Cu(OH)
2
) and copper carbonate
(CuCO
3
). The following is the reaction
2Cu+H
2
O+CO
2
+O
2
?Cu (OH)
2
 + CuCO
3
         moist air
Does copper also get
rusted? I have seen
a greenish deposit
on the surface of
copper vessels.
Fig. 4.4 (b) : Testing of solution with litmus
papers
© NCERT
not to be republished
Page 5


MATERIALS : METALS AND NON-METALS
MATERIALS : METALS AND NON-METALS
Y
ou are familiar with a number of
materials like iron, aluminium,
copper, etc. Some materials have
been given in Table 4.1.
similar change if we try to beat a
wood log ?
Let us find out.
Activity 4.1
Take a small iron nail, a coal piece,
a piece of thick aluminium wire and
a pencil lead. Beat the iron nail with
a hammer (Fig. 4.1). (But take care
that you don’t hurt yourself in the
process). Try to hit hard. Hit hard
Table 4.1 : Appearance and
Hardness of materials
Object Appearance Hardness
/Material (Shiny/Dull) (Very hard/
Not very
hard)
Iron
Coal
Sulphur
Aluminium
Copper
-----
Can you name the materials which
are metals? The rest of the materials in
Table 4.1 are non-metals. Metals can be
distinguished from non-metals on the
basis of their physical and chemical
properties. Recall that lustre and
hardness are physical properties.
4.1Physical Properties of
Metals and Non-metals
Have you ever seen a blacksmith beating
an iron piece or an article made up of
iron, like a spade, a shovel, an axe? Do
you find a change in the shape of  these
articles on beating? Would you expect a
Table 4.2 Malleability of Materials
Object/ Change in Shape
Material (Flattens/Breaks
into pieces)
Iron nail
Coal piece
Aluminium wire
Pencil lead
also the aluminium wire. Then
repeat the same kind of treatment
on the coal piece and pencil
lead. Record your observations in
Table 4.2.
Fig. 4.1 : Beating an iron nail with hammer
© NCERT
not to be republished
Fig. 4.2 : Electric tester
Where do you find the use of
aluminium and copper wires? Have you
seen wires of coal? Definitely not!
The property of metal by which it can
be drawn into wires is called ductility.
Have you ever noticed the difference
in sound on dropping an iron sheet/
plate, a metal coin, and a piece of coal
on the floor? If not, you can try it now.
Do you note any difference in the sound
produced?
Oh! The meaning of recalling
our experiences and then of
this activity was to show that
metals are good conductors of
heat and electricity. We learnt
this in Class VI.
MATERIALS : METALS AND NON-METALS 45
You saw that the shape of the iron nail
and the aluminium wire changed on
beating. If they were beaten harder these
could be changed into sheets. You might
be familiar with silver foil used for
decorating sweets. You must also be
familiar with the aluminium foil used for
wrapping food. The property of metals by
which they can be beaten into thin sheets
is called malleability. This is a
characteristic property of metals. As you
must have noticed, materials like coal and
pencil lead do not show this property. Can
we call these as metals?
Can you hold a hot metallic pan which
is without a plastic or a wooden handle
and not get hurt? Perhaps not! Why? Try
to list some other experiences in which a
wooden or plastic handle protects you
from being hurt while handling hot
things. On the basis of these experiences
what can you say about the conduction
of heat by wood and plastic?
You must have seen an electrician
using his screw driver. What kind of
handle does it have? Why?
Let us find out.
Activity 4.2
Recall how to make an electric
circuit to test whether electricity can
pass through an object or not
(Fig. 4.2). You might have performed
the activity with various objects in
Class VI. Now, repeat the activity
with the materials mentioned in
Table 4.3. Observe and group these
materials into good conductors and
poor conductors.
Table 4.3 : Electrical
conductivity of materials
S.No. Materials Good Conductor /
Poor
Conductor
1. Iron rod/nail
2. Sulphur
3. Coal piece
4. Copper wire
You observe that iron rod, nail and
copper wire are good conductors while
rolled sulphur piece and coal piece are
poor conductors.
© NCERT
not to be republished
SCIENCE 46
Have you seen wooden bells in
temples? Can you give reason?
The things made of metals produce
ringing sound when struck hard.
Suppose you have two boxes similar in
appearance, one made of wood and the
other of metal. Can you tell which box
is made of metal by striking both the
boxes?
Since metals produce ringing
sounds, they are said to be sonorous.
The materials other than metals are not
sonorous.
After performing the above activities,
we can say that some materials are hard,
lustrous, malleable, ductile, sonorous
and good conductors of heat and
electricity. The materials which
generally posses these properties are
called metals. The examples of metals
are iron, copper, aluminium, calcium,
magnesium, etc. In contrast, materials
like coal and sulphur are soft and dull
in appearance. They break down into
powdery mass on tapping with hammer.
They are not sonorous and are poor
conductors of heat and electricity. These
materials are called non-metals. The
examples of non-metals are sulphur,
carbon, oxygen, phosphorus, etc.
which rust is formed. You had also
performed  in Class VII an activity of
burning a magnesium ribbon in air. You
had learnt that in both the processes
oxide formation takes place. Complete
the following reactions of iron and
magnesium with oxygen.
Iron (Fe) + Oxygen (O
2
) + Water (H
2
O) ? ?
Magnesium (Mg) + Oxygen (O
2
)  ? ?
Activity 4.3
Let us check the nature of rust
formed as a result of the reaction
between iron, oxygen and water.
Collect a spoonful of rust and
dissolve it in a very little  amount of
water. You will find that the rust
remains suspended in water. Shake
the suspension well. Test the
solution with red and blue litmus
papers (Fig. 4.3). What do you
observe? Is the solution acidic or
basic?
Metals like sodium and potassium are
soft and can be cut with a knife.
Mercury is the only metal which is
found in liquid state at room
temperature. These are exceptions.
4.2Chemical Properties of
Metals and Non-metals
A. Reaction with Oxygen
You are familiar with the phenomenon
of rusting of iron. Recall the reaction by
Rust
Rust
suspension
Red litmus
paper
Fig. 4.3 : Testing the nature of rust
© NCERT
not to be republished
MATERIALS : METALS AND NON-METALS 47
Fig. 4.4 (a) : Burning of sulphur powder
Improvised
deflagrating
spoon
Now recall  the activity of burning
magnesium ribbon. The ash obtained
on burning magnesium ribbon is
dissolved in water and tested for its
acidic / basic nature.
Is the solution acidic or basic? How
do you ascertain this?
You must have observed that the red
litmus turns blue. So, oxide of magnesium
is also basic in nature. In general, metallic
oxides are basic in nature.
Let us now observe the reaction of
non-metals with oxygen.
Activity 4.4
(To be demonstrated by the teacher
in the class)
Take a small amount of powdered
sulphur in a deflagrating spoon and
heat it. If deflagrating spoon is not
available, you may take a metallic cap
of any bottle and wrap a metallic wire
around it and give it the shape
shown in Fig. 4.4 (a).
As soon as sulphur starts burning,
introduce the spoon into a gas jar/
glass tumbler [Fig. 4.4 (a)]. Cover the
tumbler with a lid to ensure that
the gas produced does not escape.
Remove the spoon after some time.
Add a small quantity of water into
the tumbler and quickly replace the
lid. Shake the tumbler well. Check
the solution with red and blue
litmus papers [Fig. 4.4 (b)].
When a copper vessel is exposed to
moist air for long, it acquires a dull
green coating. The green material is
a mixture of copper hydroxide
(Cu(OH)
2
) and copper carbonate
(CuCO
3
). The following is the reaction
2Cu+H
2
O+CO
2
+O
2
?Cu (OH)
2
 + CuCO
3
         moist air
Does copper also get
rusted? I have seen
a greenish deposit
on the surface of
copper vessels.
Fig. 4.4 (b) : Testing of solution with litmus
papers
© NCERT
not to be republished
SCIENCE 48
The name of the product formed in
the reaction of sulphur and oxygen is
sulphur dioxide gas. When sulphur
dioxide is dissolved in water sulphurous
acid is formed. The reaction can be given
as follows:
Sulphur dioxide (SO
2
) + Water (H
2
O) ?
Sulphurous acid (H
2
SO
3
)
The sulphurous acid turns blue
litmus paper red. Generally, oxides of
non-metals are acidic in nature.
Recall the name of some of the
laboratory acids and bases you have read
in Class VII. Note down their names in
Table 4.4. Identify the metal or non-
metal present in them which forms
oxides with oxygen.
B. Reaction with Water
Let us see how metals and non-metals
react with water.
Table 4.4 : Metals and Non-metals in Acids and Bases
S.No. Name of the base Metal Name of the acid Non-metal
1. Calcium hydroxide Calcium Sulphuric acid Sulphur
2.
3.
4.
5.
Sodium metal is very reactive. It
reacts vigorously with oxygen and
water. A lot of heat is generated in
the reaction. It is, therefore, stored
in kerosene.
Activity 4.5
To be demonstrated by the teacher.
During demonstration special care
should be taken that the size of the
sodium metal piece is roughly the
size of a wheat grain. It should be
held with a pair of tongs.)
Take a 250 mL beaker/glass tumbler.
Fill half of it with water. Now
carefully cut a small piece of sodium
metal. Dry it using filter paper and
wrap it in a small piece of cotton.
Put the sodium piece wrapped in
cotton into the beaker. Observe
carefully. During observation  keep
away from the beaker. When reaction
stops touch the beaker. What do you
feel? Has the beaker become hot?
Test the solution with red and blue
litmus papers. Is the solution acidic
or basic?
Fig. 4.5 : Reaction of sodium with water
© NCERT
not to be republished
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