Oasis Science and Technology 9

b. From electrolysis of water
When acidified water is electrolyzed, oxygen gas is formed along with hydrogen.

2H2O Electrolysis 2H2 + O2
+H2SO4

11.17 Physical Properties of Oxygen

i. Oxygen is a colourless, odourless and tasteless gas.

ii. It is slightly soluble in water.

iii. It is a neutral gas. So, it does not change the colour of litmus paper.

iv. It is non-combustible but supports combustion.

v. It becomes liquid at –183°C and solid at –219°C temperature.

11.18 Chemical Properties of Oxygen

i. Combustion

Oxygen does not burn itself but it supports combustion. Objects burn more brightly in

oxygen than in air. Metals like sodium, potassium, calcium, etc. burn in oxygen with

bright flame and form corresponding oxides.

4 Na + O2 ∆ 2 Na2O (Sodium oxide)

2 Mg + O2 ∆ 2 MgO (Mangnesium oxide)

4 K + O2 ∆ 2 K2O (Potassium oxide)

2 Ca + O2 ∆ 2 CaO (Calcium oxide)

ii. Reaction with non-metals

Non-metals like carbon, sulphur, phosphorus, etc. burn in oxygen and form corresponding
oxides.

C + O2 ∆ CO2 (Carbon dioxide)

S + O2 ∆ SO2 (Sulphur dioxide)

4 P + 5O2 ∆ 2P2 O5 (Phosphorus pentoxide)

iii. Reaction with organic compounds

Organic compounds like hydrocarbon, fat, carbohydrate, etc. react with oxygen and
form carbon dioxide, water and energy.

CH4+2O2 ∆ CO2 + 2H2O + Energy
∆ 6CO2 + 6H2O + Energy
C6H12O6 + 6O2

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iv. Reaction with oxides of non-metals

Non-metallic oxides react with oxygen and give corresponding higher oxides.

2 NO + O2 2NO2 (Nitrogen dioxide)

2 CO + O2 2CO2 (Carbon dioxide)

v. Reaction with hydrogen

Oxygen combines with hydrogen in the presence of electric spark and gives water.

O2 + 2H2 2H2O

vi. Reaction with nitrogen

Oxygen combines with nitrogen at about 30000C and forms nitric oxide. This reaction
takes place in the atmosphere during lightning.

O2 + N2 3000ºC 2NO (Nitric oxide)

11.19 Uses of Oxygen

i. It is used by living organisms to produce energy during respiration.
ii. It is used for combustion of wood, paper, fuel, etc.
iii. It is used for artificial breathing in hospitals.
iv. It is used for making oxy-hydrogen flame for cutting and welding of metals.
v. Mountaineers, deep sea divers, miners and astronauts carry oxygen cylinder for

breathing.
vi. Liquid oxygen is used as a fuel in rocket and missiles.

C. NITROGEN GAS

Symbol N 7p+ 7p+
Atomic number 7 7n0 7n0
Atomic mass 14
Valency 3 and 5 Fig. 11.7 Molecular structure of nitrogen
Molecular formula N2
Molecular weight 28
Electronic configuration 1s2, 2s2 2p3

11.20 Discovery

Nitrogen gas was discovered by a Scottish scientist Daniel Rutherford in 1772 AD and named
as metphitic air (poisonous gas). Lavoisier studied its properties and named it azota, i.e. gas

194 Oasis School Science - 9 CHEMISTRY

having no life. Finally, the name nitrogen was derived from nitre (NaNO2), which has nitrogen
as one of the elements.

11.21 Occurrence

Nitrogen occurs free as well as in combined state in nature. In free state, it is present in the
atmosphere at about 78.08% by volume. In combined state, it is present in different types of
compounds like ammonia, nitre, ammonium salts, nitrate compounds, etc.

11.22 General Methods for Preparation of Nitrogen Gas

Nitrogen gas can be prepared by either of the following methods:

i. From ammonia

Nitrogen gas can be prepared by the reaction of ammonia with chlorine.

8 NH3 + 3Cl2 6NH4Cl + N2

ii. From nitric oxide

When nitric oxide gas is passed over heated copper, nitric oxide gets reduced into
nitrogen gas.

2Cu + 2NO 2CuO + N2
iii. From bleaching powder

When bleaching powder (CaOCl2) is heated with ammonia solution, it gives off
nitrogen gas.

3CaOCl2 + 2NH3 3CaCl2 + 3H2O + N2

11.23 Laboratory Preparation of Nitrogen Gas

Principle

In laboratory, nitrogen gas is prepared by heating a mixture of ammonium chloride and
sodium nitrite in solution state.

Ammonium chloride + Sodium nitrite Heat Sodium chloride + Water + Nitrogen gas
NaCl + 2H2O + N2
∆

NH4Cl + NaNO2

A Apparatus required

i. Round bottom flask (R.B. flask) ii. Delivery tube
iii. Gas jar iv. Water trough
v. Beehive shelf vi. Burner
vii. Cork viii. Stand
ix. Tripod stand

weld /weld/ - the process of joining the pieces of metals
missile /ˈmɪsaɪl/ - a weapon that is sent through the air and that explodes when hits the thing aimed

CHEMISTRY Oasis School Science - 9 195

Chemicals required
i. Ammonium chloride (NH4Cl)
ii. Sodium nitrite (NaNO2)

Delivery tube

Stand Thistle
funnel

Round Nitrogen gas
bottom flask
Gas gar
Ammonium chloride Water
+
Water trough
Sodium nitrite Beehive shelf
(NH4Cl+NaNO2)

Tripod stand
Burner

Fig. 11.8 Laboratory preparation of nitrogen gas (N2)

Procedure

i. Make a mixture of ammonium chloride and sodium nitrite and keep it in a round
bottom flask.

ii. Make a solution by adding some water and stir.
iii. Arrange the apparatus as shown in the figure.

iv. Supply heat with the help of Bunsen burner.

On heating the mixture, reaction takes place in two steps as given below and produces

nitrogen gas. NH4 Cl + Na NO2 ∆ NH4NO2 + NaCl
NH4NO2 ∆ 2H2O + N2
∆ NaCl +2H2O + N2
NH4 Cl + Na NO2

Nitrogen gas thus produced is collected in the gas jar by the downward displacement of

water.

Precautions

i. The apparatus should be made airtight.

ii. Moderate heat should be supplied during the course of reaction.

iii. The burner should be removed as soon as nitrogen gas starts to evolve.

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11.24 Test of Nitrogen Gas

i. When a burning match stick is inserted inside the gas jar, the match stick gets
extinguished. It proves that the gas is nitrogen. Carbon dioxide gas also extinguishes
the fire. So some amount of lime water is added into the gas jar. If it does not give
milky white colour, it proves that the gas is nitrogen.

ii. When a burning magnesium ribbon is inserted into the gas jar of nitrogen, it burns
in nitrogen gas forming yellow powder of magnesium nitride (Mg3N2).

11.25 Manufacture of Nitrogen Gas

For commercial purpose, nitrogen gas is prepared by following methods:

i. From air
A mixture of different types of gas (air) is collected and liquefied at very low tem-

perature and high pressure. Now, the liquid gaseous mixture is subjected to frac-
tional distillation. Liquid nitrogen having low boiling point (–196°C) distills out
first leaving the liquid oxygen of higher boiling point (–183°C). In this way, nitro-
gen vapour is collected in the cylinder.

ii. From ammonia

For commercial purpose, nitrogen gas can also be prepared by inducing a reaction
between ammonia and chlorine.

8NH3 + 3Cl2 6NH4Cl + N2

11.26 Physical Properties of Nitrogen Gas

i. It is a colourless, odourless and tasteless gas.
ii. It is lighter than air.
iii. It is neutral to the indicators.
iv. It neither burns nor supports combustion.
v. It is insoluble in water.

vi. It liquefies at –196°C and solidifies at –210°C.

11.27 Chemical Properties of Nitrogen Gas

Nitrogen is a diatomic molecule having triple covalent bonds (N≡N). Due to the presence
of three bonds, it is very less reactive at ordinary temperature. But at high temperature, the
bonds between nitrogen atoms break and induce certain chemical reactions.

i. Reaction with hydrogen

Nitrogen combines with hydrogen at about 5000C and 200 to 600 atmospheric
pressure in the presence of iron as a catalyst and molybdenum as a promoter to
give ammonia.

N2 + 3H2 500ºC, 200 to 600 atm. 2NH3
Fe/ Mo

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ii. Reaction with oxygen
Nitrogen combines with oxygen at about 3000°C to give nitric oxide.

N2 + O2 3000º C 2NO

iii. Reaction with metals

Nitrogen combines with metals to give metallic nitrides.

3Ca + N2 Ca3N2 (Calcium nitride)

2Al + N2 2AlN (Aluminium nitride)

3Mg + N2 Mg3N2 (Magnesium nitride)

11.28 Uses of Nitrogen Gas

i. It is used in the manufacture of ammonia gas, nitric acid, nitroglycerine, etc.
ii. It is used in the fuel tanks of aeroplanes to prevent explosion.

iii. It is used in high temperature thermometer to reduce evaporation.

iv. It is used in electric bulbs to provide inert atmosphere.

v. It is used in the manufacture of nitrogenous fertilizers like ammonium nitrate,
ammonium sulphate, etc.

vi. Liquid nitrogen is used as a cooling agent.

Reasonable fact-2

Why is nitrogen filled in electric bulbs?
Nitrogen gas is inactive. It creates pressure inside the bulb which prevents the filament
from burning. So, nitrogen gas is filled inside electric bulbs.

SUMMARY

• The atmosphere is the layer of air that surrounds the earth's crust.

• Air is the mixture of different gases like nitrogen, oxygen, carbon dioxide,
neon, argon, etc.

• In laboratory, hydrogen gas is prepared by the reaction of granulated zinc
with dilute hydrochloric acid or dilute sulphuric acid.

Zn + dil. 2HCl ZnCl2 + H2↑

• Hydrogen is the lightest, colourless, odourless and tasteless gas.

• Hydrogen is used to fill balloons, to make vegetable ghee, to make chemical
fertilizers, to make oxy-hydrogen flame, etc.

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• Oxygen is one of the most important gases in the atmosphere. It occupies about
20.95% of the total volume.

• In laboratory, oxygen gas is prepared by using heat or without using heat.

• Oxygen gas is prepared by the decomposition of potassium chlorate in the presence

of manganese dioxide as a positive catalyst.

2KClO3 MnO2 2KCl + 3O2↑

• Oxygen is also prepared by the decomposition of hydrogen peroxide in the presence

of manganese dioxide as a positive catalyst.

2H2O2 MnO2 2H2O + O2↑

• Oxygen is a colourless, odourless, tasteless and neutral gas.

• Oxygen gas is used by living organisms for breathing. It is also used for burning
substances, making oxyhydrogen flame, etc.

• In the atmosphere, nitrogen constitutes 78.08% of the total volume.

• Nitrogen gas has triple covalent bonds (N ≡ N) between nitrogen atoms. So, it is less
reactive.

• In laboratory, nitrogen gas is prepared by heating the mixture of ammonium
chloride and sodium nitrite in solution state.

NH4Cl + NaNO2 NaCl + 2H2O + N2

• Nitrogen is a colourless, odourless, tasteless and neutral gas.

• Nitrogen gas is lighter than air and slightly soluble in water.

• Nitrogen gas is used to make ammonia, nitric acid, explosives, chemical fertilizers, etc.

• When a burning match stick is inserted inside the gas jar, the match stick gets ex-
tinguished. It proves that the gas is nitrogen. Carbon dioxide gas also extinguishes
the fire. So some amount of lime water is added into the gas jar. If it does not give
milky white colour, it proves that the gas is nitrogen.

• Nitrogen is a diatomic molecule having triple covalent bonds (N≡N). Due to the
presence of three bonds, it is very less reactive at ordinary temperature. But at high
temperature, the bonds between nitrogen atoms break and induce certain chemical
reactions.

CHEMISTRY Oasis School Science - 9 199

Exercise

Group-A
1. What is air? Write down the percentage of carbon dioxide in air.
2. What is the percentage of nitrogen and oxygen in air?
3. Write down the atomic number, atomic weight, molecular formula and molecular weight

of hydrogen.
4. Name the scientist who discovered hydrogen gas.
5. Write any two physical properties of hydrogen gas.
6. What is a catalyst? Write with examples.
7. How is hydrogen gas tested? Write.
8. Write down the melting point and boiling point of hydrogen.
9. Name the scientist who discovered oxygen gas.
10. What is the valency of oxygen? Why?
11. Write down the molecular weight and atomic weight of oxygen.
12. How is oxygen gas tested?
13. What is the percentage of oxygen gas in fresh air?
14. Write any two physical properties of oxygen gas.
15. What is oxyhydrogen flame? Why is it used?
16. Write down the boiling point of oxygen.
17. What is the percentage of nitrogen in air?
18. Write down the valency and atomic weight of nitrogen.
19. Write down any two physical properties of nitrogen.
20. How is nitrogen gas tested? Write.
21. Write down the molecular formula of niter and salt petre.
22. What is Haber's process?
23. Name a catalyst and a promoter which is used for preparing nitrogen gas.
24. Write down the boiling points of nitrogen and oxygen.

Group-B
1. Copper sulphate is used during laboratory preparation of hydrogen gas. Give reason.
2. We use impure zinc during laboratory preparation of hydrogen gas, why?

200 Oasis School Science - 9 CHEMISTRY

3. Conc. sulphuric acid is not used during laboratory preparation of hydrogen gas, why?

4. Hydrogen gas is used to fill balloons, why?

5. Oxygen gas is essential for living beings, why?

6. Why is nitrogen gas filled in electric bulbs?

7. Why is nitrogen gas used in fuel tanks of aeroplanes?

Group-C
1. How is hydrogen gas manufactured in industries? Describe in brief the importance of

oxygen gas for living beings.
2. How is urea prepared by using hydrogen gas?
3. Write down any three uses of nitrogen gas.
4. How can you prove that oxygen gas supports combustion? Describe.
5. Write any three uses of hydrogen.
6. How is nitrogen extracted from air? Describe in brief.
7. Write down the main uses of oxygen gas.
8. How is chemical fertilizer prepared from nitrogen? Describe. What is oxyhydrogen

flame? Why is it used for?

Group-D
1. Describe the method of laboratory preparation of hydrogen gas with a labelled diagram.
2. Describe the method of laboratory preparation of oxygen gas by using heat. Also, draw

well labelled figure.
3. Answer the following questions on the basis of the given figure.

Dilute H2SO4 Delivery tube
Thistle funnel

Cork Gas jar

Woulfe's bottle Beehive shelf
Granulated zinc Water trough

Water

i) Which gas is being collected in the gas jar?

ii) What will happen if this gas is heated with phosphorus? Write with chemical
reaction?

iii) Describe the role of Manganese dioxide in the above process.

CHEMISTRY Oasis School Science - 9 201

4. Study the given figure and answer the following questions.

Hydrogen peroxide
Stopper

Gas jar

Mixture of H2O2 + MnO2 Water trough

i) Which gas is being collected in the gas jar?
ii) Write down the balanced chemical equation of the reaction that takes place in the

above process.
iii) What will happen when this gas is heated with oxygen? Write with chemical

equation.
5. Answer the following questions on the basis of given figure.

Delivery tube

Ammonium chloride Gas gar
+ Water

Sodium nitrite

Beehive shelf

i) Which gas is being collected in the gas jar?
ii) Write down the role of MnO2 in this process.
iii) Write down the chemical equation of the preparation of this gas.

202 Oasis School Science - 9 CHEMISTRY

UNIT12 Estimated teaching periods

Theory 5

Practical 0

METALS

Metals

Objectives

After completing the study of this unit, students will be able to:

• differentiate between metals and non-metals.
• explain the properties of metals and non-metals.
• introduce alloys and metalloids.
• explain the role of metals in living beings (zinc as enzyme, significance of sodium

and potassium ions, negative impacts of mercury (Hg) and lead (Pb) in human
body).

12.1 Introduction

There are altogether 118 elements known till today. It is very difficult to study all these elements
separately. So, on the basis of characteristics, they are divided into three groups, i.e. metals,
non-metals and metalloids. Of the 118 elements, more than 80% of the elements are metals
and the rest of elements are non-metals and metalloids. Elements like iron, copper, aluminium,
silver, gold, etc. are metals. They are good conductors of heat and electricity. Metals are being
used by human beings from pre-historic time. Metals are used for making cooking utensils,
weapons, wires, bodies and parts of vehicles, rods, engines, industrial materials, coins and
many more.

Metals occur in the form of compounds as well as with different types of impurities. They are
separated from various impurities by applying several methods and steps. After the complete
separation, the pure metals are used for different purposes. In this unit, we will discuss the
properties of metals, non-metals and metalloids.

12.2 Metals

Metals are those electropositive elements which are good conductors of heat and electricity.
They form electropositive ions by losing electron/s. Examples: Copper, gold, iron, aluminium,
sodium, mercury, calcium, zinc, etc.

a. Physical properties of metals

1. Physical state: Most of the metals exist in solid state at normal temperature but mercury
is found in liquid state.

metalloid /ˈmetlɔɪd/ - the substance having the properties of both metal and non-metal
lustre /ˈlʌstə/ - the shining quality of a surface

CHEMISTRY Oasis School Science - 9 203

2. Hardness: Most of the metals are hard but lithium, sodium and potassium are soft.

3. Density: Most metals have high density except lithium, sodium and potassium.

4. Lustre: Pure metals have brilliant metallic lustre, e.g. gold has a yellow shine and silver
has a white shine.

5. Conductivity: Metals are Ductile
good conductors of heat
and electricity. Therefore, High melting Lusture
metals are used for making point and
cooking utensils and
electric wires. boiling point

6. Malleability: The property

of a metal due to which

it can be beaten into thin Solid state Physical Malleable
sheets is called malleability. except Hg Properties of
Most of the metals are
malleable except lithium, Metals

sodium, potassium, and

mercury.

7. Ductility: The property Hard and Good
of a metal due to which it brittle conductor
can be drawn into a long of heat and
wire is called ductility. electricity
Most metals are ductile
High
density

except lithium, sodium,

potassium and mercury. Fig. 12.1

8. Melting points and

boiling points: Hard metals with high density have high melting and boiling points but

soft metals with low density have low melting and boiling points.

Hard metals Melting point Boiling point Soft metals with Melting point Boiling point
with high low density
density 15000C
10830C 25000C 1. Lithium (Li) 1800C 13260C
1. Iron (Fe) 9600C 23500C 2. Sodium (Na) 97.50C 8800C
19550C 3. Potassium (K) 72.50C 7570C
2. Copper (Cu)

3. Silver (Ag)

9. Electric charge: Metals lose electrons from their valence shell and form electropositive ions.

NaCl Na+ + Cl– Reasonable fact-1

KCl K+ + Cl– Why are metals used for making
cooking utensils? Give reason.
Na2SO4 2Na+ + SO4– – Metals are malleable and good conductor
Cu+ + + SO4– – of heat and electricity. So, they are used
CuSO4 for making cooking utensils.



204 Oasis School Science - 9 CHEMISTRY

b. Chemical properties of metals

1. Reaction with oxygen: When metals are heated with oxygen, they form corresponding

metal oxides. Examples: ∆ 2Na2O
∆ 2 K2O
4Na + O2 ∆ 2 MgO
∆
4 K + O2 2CaO

2 Mg + O2

2Ca + O2

2. Reaction with hydrogen: Some active metals like sodium, potassium, calcium, etc. react

with hydrogen and form unstable hydrides. Examples:

Na + H2 burn 2 NaH (Sodium hydride)

K + H2 burn 2 KH (Potassium hydride)

Ca + H2 burn CaH2 (Calcium hydride)

3. Reaction with acids: Most of the active metals react with acids and produce salt and
hydrogen gas. Examples:

Zn + dil. HCl ZnCl2 + H2

Mg + dil. HCl MgCl2 + H2
Zn + dil. H2SO4 ZnSO4 + H2
MgSO4 + H2
Mg + dil. H2SO4

Some important metals with their symbol, atomic number, atomic weight and valency
are given below:

S.No. Metals Symbol Atomic Atomic Valency
number weight
1. Lithium Li 1
2. Sodium Na 3 7 1
3. Magnesium Mg 11 23 2
4. Aluminium Al 12 24 3
5. Potassium K 13 27 1
6. Calcium Ca 19 39 2
7. Iron Fe 20 40 2, 3
8. Copper Cu 26 56 1, 2
9. Zinc Zn 29 63 2
10. Silver Ag 30 65 1
11. Gold Au 47 108 1, 3
79 191
12. Mercury Hg 1, 2
80 201

CHEMISTRY Oasis School Science - 9 205

12.3 Non-metals Reasonable fact-2

Non-metals are those electronegative elements Why are metals used for making
which are bad conductors of heat and electricity. electric wires? Give reason.
Examples: Oxygen, nitrogen, sulphur, chlorine, Metals are ductile and good conductor of
iodine, etc. electricity. So, they are used for making
electric wires.
Properties of Non-metals

1. They are electronegative in nature, i.e. they gain electrons during chemical
reaction.

2. They are bad conductors of heat and electricity except graphite.

3. They are non-malleable and non-ductile in nature.

4. They do not have metallic lustre except diamond and iodine.

5. They are present in solid, liquid and gaseous state.

6. They do not produce clinking sound. So they are non-sonorous in nature.

12.4 Differences between Metals and Non-metals

S.N. Metals S.N. Non-metals

1. Metals are electropositive in nature. 1. Non-metals are electronegative in
nature.

2. Metals are malleable. 2. Non-metals are non-malleable.

3. Metals are ductile. 3. Non-metals are non-ductile.

4. They are good conductor of heat and 4. Non-metals are poor conductor of

electricity. heat and electricity except graphite.

5. Most metals exist in solid state at 5. Non-metals exist in all three states at

room temperature except mercury. room temperature.

6. They possess metallic lustre except 6. They do not contain metallic lustre

lithium. except iodine and graphite.

7. They are generally hard except 7. They are generally soft except

sodium and potassium. diamond.

8. They form alloy with other metals. 8. They generally do not form alloys

with other metals.

9. Metals form basic oxides. 9. Non-metals form acidic oxides.

10. Metals react with acid to give salt and 10. Non-metals usually do not form salt

hydrogen gas. and hydrogen gas.

11. Metals generally do not combine 11. Non-metals generally form stable

with hydrogen. If they combine hydrides.

with hydrogen, they form unstable

hydrides.

alloy / ˈ æ l ɔ ɪ / - a homogeneous mixture of two or more metals or metals and non-metals
brittle /ˈbrɪtl/ - hard but easily broken

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12.5 Alloy

The homogeneous mixture of two or more metals or metals and non-metals is called alloy. The
molten mass of two or more metals or non-metals when mixed completely, forms homogenous
mixture. On cooling this mixture, we get a solid mass which is called alloy. The alloy which is
formed by mixing a metal and mercury is called amalgam. The melting point of alloy is always
lower than its component metals. But it has greater hardness and more brittleness.

Properties of alloys

1. Alloys are generally harder and stronger than their components.

2. They have metallic properties like malleability and ductility.

3. They are good conductors of heat and electricity.

4. They are more brittle than their components.

5. They have generally low melting point than that of their components.

Some alloys and their components

S.N. Alloys Components

1. Brass Copper (70%) and Zinc (30%)

2. Bronze Copper (88%) and Tin (12%)

3. Bell metal Copper (80%) and Tin (20%)

4. Artificial gold (Rold gold) Copper (90%) and Aluminium (10%)

5. Stainless steel Iron (89.4%), Chromium (10%), Manganese (0.35%)
and Carbon (0.25%)

Brass Bronze Bell metal Rold gold Steel
Fig. 12.2
Activity 1

• Take a few iron nails or a piece of iron. Keep it in a moist place and observe it after 3-4
days. What do you observe?

You can see a reddish-brown layer on the surface of the iron nails.

The formation of reddish-brown scales or powder on the surface of iron when it
comes in contact with moist air is called rusting. As a result of rusting, weight of
metal increases. To protect iron from rusting, we apply several methods like painting,
forming alloys, galvanizing, etc.

x4Fe + H2O + 3O2 x2Fe2O3 . H2O (Rust)

CHEMISTRY Oasis School Science - 9 207

12.6 Metalloids

The elements having the characteristics of both metals and non-metals are called metalloids.
For example, silicon, arsenic, antimony, germanium, etc. They are kept in the border line of
metals and non-metals. They are also called semiconductors.

Properties of metalloids
1. Metalloids are poor conductors of heat and electricity.

2. They have lustre, i.e. shiny nature.

3. They do not have malleability and ductility.

4. They form alloys.

12.7 Role of Metals in Organisms

Generally, six types of non-metals, viz. carbon (C), hydrogen (H), nitrogen (N), oxygen (O),
phosphorus (P) and sulphur (S) are found in the bodies of living organisms. Similarly, different
types of metals are also found in bodies of living beings. These metals include sodium (Na),
potassium (K), calcium (Ca), zinc (Zn), magnesium (Mg). These metals and non-metals are
found in the form of compounds. Substances like protein, nucleic acid, lipids, etc. are formed
from these elements, which are also known as biological inorganic substances. These elements
have a great role in the bodies of living organisms. Among the above mentioned metals, Na,
Mg, K and Ca are found in large amount whereas metals like Mn, Fe, Co, Cu, Zn and Mo are
found in small amounts.

12.8 Zinc in Enzyme

Zinc is a very important metal though it is found in small amount. About 300 enzymes in
human body contain zinc. About 2-3 gram of zinc is found in human body. Zinc is found in
almost all organs of human body. It is found in cytoplasm, cells, tissues, bones, organs, etc.
About 90% of zinc of the body is found in muscles and bones. A significant amount of zinc
is found in prostate gland and semen. Similarly, a large amount of zinc is found in retina
which decreases with age and finally the person cannot see things clearly. In the body of living
beings, zinc is found in the form of compounds and ions.

Role of zinc in human body

1. In human body, zinc is essential for development of embryo to increase height and
weight of the body.

2. Zinc is essential for development of bones.
3. It is essential to regulate menstrual cycle in women.
4. It is essential to increase sex power/fertility in men.
5. It is essential to treat anorexia, psoriasis and neurodermitis.
6. It is essential to increase immune system.
7. It is essential to taste food iterms and smell things.

208 Oasis School Science - 9 CHEMISTRY

8. It is essential to prevent pneumonia, diarrhoea and other infectious diseases.

9. It is essential to cure wounds and form skin cells.

12.9 Importance of Sodium and Potassium Ions

Among the different metals found in human body, sodium and potassium play a significant
role. Those metals are found in the form of ions inside and outside cells. Nervous system can
work only due to the presence of metallic ions as they contain charges. Various metabolic
activities occur in the body due to the exchange of ions in cells. When sodium ions present
outside the cell enter the cells, potassium ions leave the cell. This process occurs at the same
time which is called sodium-potassium pump. This process is very important for human body.
Sodium-potassium pump is essential to exchange information between neurons and brain, to
regulate heart beat and body temperature, to keep muscles sound, to control pH of solutions
in the cells, etc. Various disorders like migraine, muscle spasm, paralysis, etc. occur in the
body due to irregularity in sodium and potassium pump. Therefore, there should be proper
balance in sodium and potassium ions in the human body.

12.10 Harmful Effects of Mercury and Lead

a. Mercury
The poisonous effect of mercury in human body is called hydrargyria or mercurialism.

One drop of mercury may block blood vessels and cause death of the victim. The
compounds of mercury damage the brain. Similarly, they weaken the ability to speak,
hear and see things. Mercury also affects the foetus. The compounds of mercury pass
easily through placenta and affect the growth and development of the foetus adversely.
Mercury also affects the development of child's brain adversely.

b. Lead
Lead (Pb) affects almost all the organs of human body. It spreads throughout the

body like other useful metals. It affects the brain adversely. Symptoms like headache,
abdominal pain, change in behaviour, lack of brain development, etc. occur in children.
Blood cannot combine with oxygen due to the presence of lead which causes anaemia.
Lead accumulates in bones which affects the formation of blood cells in bone marrow.
It also affects calcium absorption by bones which weakens them. Therefore, we should
avoid the food items containing lead.

CHEMISTRY Oasis School Science - 9 209

SUMMARY

• Metals are electropositive elements which are malleable, ductile and good
conductors of heat and electricity.

• Non-metals are electronegative elements which are non-malleable and non-ductile.

• The homogeneous mixture of two or more metals or metals and non-metals is called
alloy.

• The elements having the properties of both metals and non-metals are called
metalloids.

• Metals can be converted into thin sheet on hammering. This property is called
malleability.

• Metals can be converted into thin and long wires. This property is called ductility.

• Metals are good conductors and non-metals are bad conductors of heat and
electricity.

• Metalloids are poor conductors of heat and electricity.

• Various types of metals like Na, K, Zn, Ca, Fe, Mg, Cu, etc. and non-metals like C,
H, N, O, P and S are found in the bodies of living organisms.

• Zinc is an essential metal which is found in about 300 enzymes. It is essential
for growth and development of embryo, to treat various diseases like anorexia,
psoriasis, neurodermitis, etc.

• Zinc helps to increase the immunity, to increase fertility of males and regulate
menstrual cycle in female.

• Mercury and lead are harmful metals for human body. We should avoid the food
items containing mercury and lead.

Exercise

Group-A
1. What are metals? Give any two examples.
2. What are non-metals? Give any two examples.
3. What are metalloids? Write any two examples.
4. Write any two physical properties of metals.
5. Write down the atomic number, atomic weight and valency of given metals:
i) Lithium ii) Magnesium iii) Potassium iv) Iron v) Zinc vi) Gold
6. Name the metal which is found in liquid state at normal temperature.
7. Name any two soft metals.

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8. What is ductility? What is its advantage?
9. Name any two metal oxides which are not basic oxides.
10. Name a non-metal which is found in liquid state at ordinary temperature.
11. Name a non-metal that forms electropositive ion.
12. Name any two metals having high density.
13. Name any two metals having low density and low melting point.
14. Name a non-metal having more density.
15. Name a lustrous non-metal.
16. Name a non-metal which conducts electricity.
17. Name a metal which cannot be beaten into a sheet.
18. Name any two metals which are malleable.
19. Name any two metals which are not ductile.
20. What is conductivity of metals?
21. Write down the melting point of the given metals:
– silver – iron – copper – potassium
22. Name two metals and two non-metals found in the bodies of living beings.
23. What is meant by sodium-potassium pump?

Group-B
1. Differentiate between metals and non-metals.
2. Why is copper called a metal? Give any two reasons.
3. Why is carbon called a non-metal? Give any two reasons.
4. Why is silicon called a metallioid?
5. Write any two differences between metals and metalloids.
6. Why are iron and copper used for making cooking utensils? Give two reasons.
7. Write any two differences between non-metals and metalloids.
8. Why are non-metals not suitable for making cooking utensils and electric wires?
9. Differentiate between metals and alloys in any two points.
10. Why is copper used for making electric wires? Give two reasons.

Group-C
1. Write any three uses of metals.
2. What happens when the solution of silver nitrate is electrolysed? Write. Name a lustrous

non-metal.
3. Write a short note on 'Zinc in enzyme.' Name a non-metal that forms electropositive ion.
4. List the harmful effects of mercury and lead in human body. Name a non-metal which is

good conductor of heat and electricity.

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5. Describe in brief the role of zinc in human body. Name any two metals which malleable.

6. Describe in brief the role of metals in human body. Name any two metals which
malleable.

Group-D

1. Complete the given chemical equations:

i) Mg + H2 ........................ ii) Na + HNO2 ............... + H2

iii) H2 + K ...................... iv) K + .................. K2 SO4 + H2

2. What happens when?

i) Sodium reacts with hydrochloric acid

ii) Potassium sulphate is electrolysed

iii) Copper sulphate is electrolysed

iv) Magnesium chloride is electrolysed

3. Complete the given ionic equations. Differentiate between malleability and ductility.

NaCl + ................. + Cl-

CuSO4 Cu+ + + ..............

4. Describe in brief the role of sodium and potassium ions in the bodies of living beings.

5. What is the reason behind that the melting and boiling point of iron is more than that of
sodium? Write a short note on non-metals.

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UNIT13 Estimated teaching periods

Theory 5

Practical 0

CARBON AND ITS Diamond

COMPOUNDS

Objectives

After completing the study of this unit, students will be able to:
• introduce carbon and its compounds.
• explain the physical and chemical properties of carbon.
• explain the allotropes of carbon.
• differentiate between organic and inorganic compounds.

13.1 Introduction

Carbon is one of the most important and unique non-metallic elements. The word carbon has
been derived from the Latin word 'carbo', which means shoot or charcoal. Carbon is widely
distributed on the earth in free as well as in combined state. In free state, it is present in
diamond, graphite, charcoal, coal, etc. whereas in combined state, it is present in carbon
monoxide, carbon dioxide, carbonates, carbohydrates, proteins, fats, nucleic acids, petroleum,
natural gas, etc. The bodies of living beings contain carbon and its compounds in abundant
quantity. When we burn these carbon containing compounds, we get black shoot, smoke,
charcoal, etc.

Carbon occurs in different forms with different physical properties which are called allotropes.
Diamond is one of the hardest allotropes which is transparent, brilliant and precious whereas
graphite is another soft, slippery, black and greasy allotrope of carbon.

Activity 1

Objective : To prove sugar contains carbon. Water droplets
Sugar
Materials required : Sugar, hard glass test tube and Burner

source of heat (Bunsen burner) Fig. 13.1

Procedure : Keep some sugar in the hard

glass test tube and heat with the

help of Bunsen burner.

abundant / ə ˈ b ʌ n d ə n t / - in large quantities
allotrope /ˈælətrəʊp/ - one of the different forms in which a chemical element exists

CHEMISTRY Oasis School Science - 9 213

Observation
1. Initially at about 186°C sugar melts and gives yellowish syrup.
2. On further heating, it turns into a brownish mass with good smell which is called caramel.
3. At final stage, the mass is converted into black matter called charcoal, i.e. carbon.
Conclusion
The above activity shows that sugar contains carbon.

13.2 Structure of Carbon Atom

The nucleus of carbon atom consists of six protons and six neutrons. Six electrons revolve
around the nucleus in two orbits, viz. K and L. The shell K consists of two electrons whereas

the shell L consists of four electrons.

Symbol = C

Atomic number = 6

Atomic mass = 12

Electronic configuration

Shell K L 6p+
No. of electrons 2 4 6n0

Position in periodic table: Period – 2, Group – IVA

Fig. 13.2 Structure of carbon atom

13.3 Nature of Carbon

Carbon has four electrons in its valence shell. So, carbon attains stable electronic configuration
in the following ways:

a. By gaining four electrons in the valence shell

b. By losing four electrons from the valence shell

c. By sharing four valence electrons with other atoms

Carbon atom has small atomic size and more electronegativity. So it attracts electrons strongly
towards its nucleus. Therefore, loss or gain of four electrons by carbon atom is not possible.
As a result, carbon shares its valence electrons with other atoms to attain stable electronic
configuration. Hence, it forms four covalent bonds as shown in the given structure.

caramel /ˈkærəmel/ - burnt sugar used for adding colour and flavour to food

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1p+

H
6p+ Or H C H

1p+ 6n0 1p+

H
Methane

1p+

Fig. 13.3 Molecular structure of methane



Carbon shows mutual sharing of its four electrons with other carbon atoms or atoms of other
elements to form a large number of covalent compounds. Carbon is one of the unique elements
which can join with each other to form a long carbon chain which is called catenation property
of carbon. Due to this property of carbon, a large number of carbon compounds are found
in nature. In fact, the number of carbon compounds is more than the number of compounds
formed from other elements. This is the reason why we have a separate branch of chemistry to
study carbon compounds or hydrocarbons which is called organic chemistry.

13.4 Sources of Carbon

Carbon occurs in different forms in nature. The major sources of carbon are as follows:
a. All organic compounds which are obtained from living organisms contain carbon.

b. Rocks containing carbonate, minerals, petrol, natural gases contain carbon as one of the
constituents.

c. Carbon monoxide, carbon dioxide, etc. contain carbon as one of the elements.

The various forms (sources) of carbon in the form of element, compound and gas are given
below:

Carbon (in the form of compounds)

Carbon (in the form Organic Inorganic Carbon (in the form of
of element) compounds compounds gas)

1. Coal 1. Carbohydrate 1. Carbonates 1. Carbon dioxide
2. Coke
3. Charcoal 2. Protein 2. Bicarbonates 2. Carbon monoxide

4. Graphene 3. Fat (ghee, oil) 3. Carbides (e.g. 3. Hydrocarbon gases (e.g.

CaC2, SiC, etc.) methane, ethane, propane,
butane, LPG, CNG, etc.)

4. Petrol 4. Minerals

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5. Graphite 5. Diesel 5. Rocks
6. Diamond 6. Urine
7. Vitamins
8. Silk
9. Paper
10. Soap
11. Wool

13.5 Physical Properties of Carbon

1. It is present in amorphous and crystalline solids.

2 It is a non-metallic element.

3. It shows different allotropes.

13.6 Allotropy of Carbon

The different forms of an element having similar chemical properties but different physical
properties are called allotropes and the characteristic by virtue of which carbon exists in
various forms in nature is called allotropy.
Carbon is a non-metallic element which occurs in different physical forms. Diamond, graphite,
coal, charcoal, etc. are the allotropes of carbon. Among them, some exist in crystalline form like
diamond and graphite and some in amorphous form like coal, charcoal, coke, etc.

Allotropes of Carbon

Crystalline forms Amorphous forms
Diamond Coal
Graphite or black lead Coke
Fullerenes Charcoal
Lamp black

Lampblack is the form of carbon which can be obtained from the flame of the kerosene lamp. It
is used to make black ink. Similarly, it is also used as collyrium (gajal).

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a. Diamond

Diamond is one of the purest forms of carbon. It is non-conductor, transparent, colourless
and precious crystalline solid. It is the hardest substance known. It is insoluble in all
ordinary solvents. It is used for making ornaments, cutting glass, drilling hard rocks, etc.

CC
C

CC

(a) Fig. 13.4 Structure of diamond (b)

In a diamond crystal, each carbon atom is combined to four other carbon atoms by
covalent bonds. Hence all the four valence electrons of each carbon atom are used up in
the bond formation without leaving free electron/s. As a result, diamond cannot conduct
heat and electricity. Therefore, diamond is a bad conductor of heat and electricity.

Properties of Diamond

i. Diamond is the purest allotrope of carbon. In its purest form, diamond is a
colourless, lustrous, crystalline solid.

ii. It is the hardest substance known. Its specific gravity is 3.52 and its refractive index is 2.415.

iii. Natural diamond is transparent to X-rays whereas artificial diamonds are opaque.
This property is used for distinguishing natural and artificial diamonds.

iv. It is a non-conductor of electricity and is insoluble in all liquids.

v. It gets converted into graphite when heated at about 1800°C.

vi. When it is heated in the presence of excess air and at very high temperature, it
burns to from carbon dioxide.

vii. Diamond has extraordinary brilliance.

Fact File-1

Diamond is the hardest substance known so far.

Uses of Diamond

i. Diamond is used for making valuable jewellery due to its extraordinary brilliance.
ii. It is used extensively for cutting, grinding and polishing as it is the hardest

substance known.

iii. It is also used for drilling hard rocks.

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b. Graphite

Graphite is a soft and the purest form of carbon. It is dark grey and crystalline powder
with metallic lustre. It has free mobile electrons. So it is a good conductor of heat and
electricity. Graphite occurs in hexagonal layers. One layer can slip over the surface of
another layer.

Fact File-2

Graphite is a non-metal
which can conduct heat
and electricity.

Fig. 13.5 Structure of graphite

In a graphite crystal, each carbon atom is connected to only three other carbon atoms by
covalent bonds. The fourth valence electron of each carbon atom is free to move. As a
result, graphite can conduct heat and electricity. Therefore, graphite is a good conductor
of heat and electricity.

Properties of graphite

i. Graphite is a soft and greasy non-metal.

ii. It is dark grey in colour and has a metallic lustre.

iii. It crystallizes in the hexagonal form and has a specific gravity of 2.2 which is much
lower than that of diamond.

iv. Unlike diamond, it is a good conductor of heat and electricity.

v. Its melting point is 3527°C.

Uses of graphite

i. Graphite is used for making lead pencils, electrodes and electric furnaces.

ii. It is also used as a lubricant for machinery.

iii. It is used as a coating for iron to prevent rusting.

iv. In nuclear reactors, it is used as a moderator as it absorbs neutrons and helps in
controlling reactions.

v. It is also used in electrotyping.

Differences between Diamond and Graphite

S.N Diamond S.N Graphite

1. It is the hardest allotrope of carbon. 1. It is soft and slippery allotrope of
carbon.

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2. It is a bad conductor of heat and 2. It is a good conductor of heat and

electricity. electricity.

3. It is a transparent crystalline 3. It is a dark grey and opaque

substance. substance.

4. Its specific gravity is 3.52. 4. Its specific gravity is 2.2.

13.7 Chemical Properties of Carbon

a. Combustion in air

Carbon burns in excess air to give carbon dioxide gas.

C + O2 ∆ CO2

If the amount of oxygen is insufficient, it forms carbon monoxide.

2C + O2 2CO

b. Reducing nature of carbon

Carbon is a good reducing agent. It reduces less reactive metallic oxides into free
metal.

PbO + C ∆ Pb + CO
ZnO + C ∆ Zn + CO



c. Reaction with steam

When carbon is strongly heated with steam at about 900–10000C, a mixture of
carbon monoxide and hydrogen gas is obtained which is called water gas.

C + H2O 900 – 1000ºC CO + H2 (water gas)

Note:

The mixture of carbon monoxide and hydrogen (CO + H2) is called water gas. It
is used in industries as a source of heat.

d. Reaction with calcium oxide (CaO)

When carbon reacts with calcium oxide or lime, it gives calcium carbide and
carbon monoxide.

3C + CaO CaC2 + CO

(Calcium carbide)
e. Reaction with metal

Carbon reacts with calcium and forms calcium carbide.

2C + Ca CaC2

(Calcium carbide)

13.8 Organic and Inorganic Compounds

In ancient time, scientists believed that organic compounds are produced within the body of
living beings by the natural process. They also believed that formation of organic compounds
takes place under the influence of vital force and they cannot be prepared in laboratory. But

CHEMISTRY Oasis School Science - 9 219

in 1828 AD, German chemist Friedrich Wohler synthesized urea in the laboratory by heating

ammonium cyanate.

NH4CNO ∆ NH2 – CO – NH2

Ammonium cyanate (Urea)

Here, ammonium cyanate is an inorganic compound whereas urea is an organic compound.
This experiment displaced the vital force theory of organic compounds. Thereafter many
organic compounds were synthesized artificially in the laboratory. The compounds formed
by reaction of carbon with elements like hydrogen, oxygen, nitrogen, etc are called organic
compounds. Examples: Methane, ethane, propane, butane, alcohol, ether, glycerol, etc. The
branch of chemistry in which we study about organic compounds is called organic chemistry.

The compounds which are derived from minerals are called inorganic compounds. They
contain other elements except hydrocarbon. For example, water, sodium chloride, calcium
carbonate, hydrochloric acid, etc. The branch of chemistry in which we study about inorganic
compounds is called inorganic chemistry.

Note:
There are certain compounds like CO2 and CO that contain carbon but are traditionally
called inorganic compounds. Compounds like CaCO3, Na2CO3, etc. also contain carbon
atom but they have electrovalent bond and they do not have hydrogen. So these compounds

are called inorganic compounds.

Differences between Organic and Inorganic compounds

S.N. Organic compounds S.N. Inorganic compounds

1. Carbon containing compounds 1. Compounds of elements other than

are called organic compounds. hydrocarbon are called inorganic

compounds.

2. They have covalent bond. So they 2. They have electrovalent bond. So they are

are called covalent compounds. called electrovalent compounds.

3. They have low melting and 3. They have high melting and boiling point.
boiling point.

4. They are soluble in organic 4. They are soluble in water.
solvents like ether, benzene, etc.

5. They burn easily. 5. They do not burn easily.

6. They ionize. 6. They do not ionize.

7. They have colour and odour. 7. They do not have colour and odour.

organic /ɔːˈɡanɪk/ - connected with the organs of plants and animals

220 Oasis School Science - 9 CHEMISTRY

Reasonable fact-1 Reasonable fact-2

Diamond is a bad conductor of heat and Graphite is a good conductor of heat
electricity, why? and electricity, why?
In a diamond crystal, each carbon atom is In a graphite crystal, each carbon atom is
combined to four other carbon atoms by connected to only three other carbon atoms
covalent bonds. Hence all the four valence by covalent bonds. The fourth valence
electrons of each carbon atom are used up electron of each carbon atom is free to move.
in the bond formation without leaving free As a result, graphite can conduct heat and
electron/s. As a result, diamond cannot conduct electricity due to presence of free electrons.
heat and electricity. Therefore, diamond is a Therefore, graphite is a good conductor of
bad conductor of heat and electricity. heat and electricity

SUMMARY

• Carbon is a solid non-metallic element which is present on the earth's crust in free
as well as in combined state.

• Carbon atom has six electrons, six protons and six neutrons. Its valency is 4.

• Carbon is mainly obtained from living organisms, organic compounds, carbon
dioxide, limestone, etc.

• Carbon shows allotropy. Diamond, graphite, coal, charcoal, etc. are the allotropes of
carbon.

• The occurrence of a single element in two or more forms is called allotropy.

• Diamond is an allotrope of carbon which is the hardest substance known. It is
transparent and colourless. It is used for making jewellery, cutting metals and
glasses, drilling hard rocks, etc.

• Graphite is a soft and slippery allotrope of carbon. It is an opaque, dark grey and
shiny substance. It is a good conductor of heat and electricity. It is used for making
leadpencils, lubricants, electrodes, etc.

• The chemical compounds which are obtained from living organisms and contain
carbon as one of the elements are called organic compounds.

• The chemical compounds which are obtained from minerals and do not contain
hydrocarbon are called inorganic compounds.

• The branch of chemistry in which we study about inorganic compounds is called
inorganic chemistry.

• The branch of chemistry in which we study about organic compounds is called
organic chemistry.

CHEMISTRY Oasis School Science - 9 221

Exercise

Group-A
1. Define organic chemistry and inorganic chemistry.
2. What are organic compounds? Give any two examples.
3. Define inorganic compounds with any three examples.
4. Write down any two properties of carbon.
5. What is a hydrocarbon? Give any two examples.
6. Write down the position of carbon in the modern periodic table.
7. What are the different sources of carbon that are found in nature?
8. What is catenation?
9. What is covalency? Write.
10. List the allotropes of carbon.
11. What is a crystalline substance? Give any two examples.
12. What type of substance is called an amorphous substance? Give any two examples.
13. What is a saturated hydrocarbon?
14. Define unsaturated hydrocarbon.
15. Write any two properties of diamond.
16. Write any three properties of graphite.
17. Write any two properties of amorphous carbon.
18. What is homologous series?
19. Define isomer and isomerism.
20. Name any two crystalline substances.
21. Name any two amorphous substances.
22. Name the type of bond found in inorganic compounds.

23. What is water gas? Give its formula.

Group-B
1. Differentiate between organic compounds and inorganic compounds.
2. Methane is called organic compound but carbon dioxide is called inroganic compound.

Give reason.
3. Differentiate between diamond and graphite.
4. Diamond cannot conduct electricity but graphite can,why?
5. Why is graphite used for making lubricants?

Group-C
1. What happens when carbon is burnt in air? Write with chemical equation. Write down

the position of carbon in the Modern periodic table.

222 Oasis School Science - 9 CHEMISTRY

2. Write down the methods of naming hydrocarbons with an example. What happens
when carbon is burnt in sufficient oxygen?

3. Write any three properties of graphite.

4. What happens when carbon is burnt in insufficient oxygen? Write with the chemical
equation. Name any two amorphous substances.

5. What is water gas? Why is it used? Name the type of bond found in organic compounds.

6. Write any three uses of diamond.

7. Write any three uses of graphite.

8. Write any three properties of diamond.

Group-D

1. Write any two difference between diamond and graphite. Complete the given chemical
equations.

i) C + ............. CO ii) C + H2O .................+ H2

2. Write any two differences between saturated in unsaturated hydrocarbons. Which of the
following compounds are saturated hydrocarbons? Why?

3. What happens in the following conditions?
i) When carbon is heated with water
ii) When carbon reacts with lead oxide
iii) When copper oxide reacts with carbon
iv) When carbon is burnt in insufficient oxygen

4. Describe the structure and properties of graphite with a labelled figure.

5. Write any two chemical properties of carbon with chemical equations.

6. What is meant by allotrophy of carbon? Explain.

7. Describe the nature and sources of carbon.

CHEMISTRY Oasis School Science - 9 223

UNIT14 Estimated teaching periods

Theory 4

Practical 2

Water River

Objectives

After completing the study of this unit, students will be able to:

• describe the sources, properties and uses of water.
• explain the methods of removing hardness of water with chemical equations.

14.1 Introduction

Water is one of the most important and abundant substances needed for living beings. It
covers approximately 70% of the earth's surface. All living beings need water to survive. Not
only is it present around us but is also inside our body. Water makes up about 70% of human
body. We can survive for a month without food but cannot live more than a weak without
water. Therefore, we should drink water every day.

Water is essential for conducting various chemical reactions that occur inside the body. It is
used to digest food, absorb nutrients and transport them to various body parts, and remove
waste products from the body. Similarly, water is required to transport raw materials from
root to leaves for photosynthesis. The prepared food is also transported to different parts of
plants from leaves with the help of water.

About 97% of the water present on the earth is found only in the oceans. It consists of a lot of
salt dissolved. So it is unfit for drinking. The dead sea contains about 33.7% of salt. So it is too
salty and hence organisms cannot survive in dead sea. But living beings float on dead sea due
to high density of sea water.

In this unit, we will study the sources of water, properties and uses of water and methods of
removing hardness of water.

14.2 Sources of Water

The sources from which we get water are called sources of water. From these sources we get
water for drinking, cooking, bathing, irrigating, washing, cleaning, etc. The major sources of
water are given below:

224 Oasis School Science - 9 CHEMISTRY

1. Surface water sources: The sources of water that are found on the surface of the earth are
called surface water resources. They can be classified as follows:

a Rain: Rain is a very important source of water. It is the purest form of water. Rain water
can be stored in dams and later used for various purposes.

b Rivers lakes and ponds: Rivers, lakes and ponds are other sources of surface water.
Rivers are formed from the melting of snow lying on the Himalayas. Similarly, rivers,
ponds and lakes are also formed from rains. The rivers like Koshi, Gandaki, Narayani,
Karnali and Mahakali are the main rivers of Nepal. Phewa lake, Shey Phoksundo lake,
Tilicho, etc. are some famous lakes of Nepal. Similarly, many ponds are found in different
parts of the country. These sources of water are very useful for human beings. The water
obtained from these resources is used for drinking, bathing, cleaning, running factories,
generating hydroelectricity, etc.

Karnali river Phewa Lake Tau Daha

Fig. 14.1

c Glaciers: Glaciers are other surface water sources found in the Himalayas. They contain
water in solid state. When the snow or ice melts due to the heat of the sun, glaciers are
formed. Glacial ice is the largest reservoir of freshwater on the earth. Khumbu is the
biggest glacier and Langtang is the longest glacier in Nepal.

Khumbu glacier Langtang glacier

Fig. 14.2

d Oceans: Oceans are the biggest sources of surface water on the earth. The ocean (Sea)
water contains a lot of salts dissolved in it due to which it is not fit for human use and
irrigation. Ocean water is used for transportation.

Fig. 14.3 Oasis School Science - 9 225
CHEMISTRY

2. Ground water sources: The sources of water

which are found below the surface of the

earth are called ground water sources. Some

of the rain water which falls on the earth seeps

through the soil and goes down under the

surface of the earth. Ultimately this water is

stopped by some hard rocks and collects there.

This underground water can be taken out by

digging well in the ground. An underground

layer of permeable rock, sediment, or soil that

yields water is called an aquifer. Aquifers

can range from a few square kilometers to

thousand square kilometers in size. They Fig. 14.4

contain thousand times more water than that

present in river, lakes and ponds. Ogallala

aquifer is the largest aquifer on the earth which is spread about 450,000 km2 in portions

of eight states of United States of America. The level of water under the earth's surface is

called water table. The underground water may contain impurities like germs, decayed

part of plants and animals, soil and sand particles, gases, etc. The underground water

does not become stagnant and may come out of the earth's surface in the form of spouts,

fountains, etc.

Activity 1

• Observe various sources of water in your locality.
• What are the uses of these water sources? Prepare a short report and submit to your

science teacher.

14.3 Physical Properties of Water

1. Pure water is colourless, odourless and tasteless.
2. It exists in solid, liquid and gaseous states.
3. Pure water is transparent.
4. It is a universal solvent.

5. Pure water is a bad conductor of electricity.

6. Its boiling point is 100 0C and freezing point is 0 0C.

14.4 Chemical Properties of Water

1. Pure water does not conduct electricity. But the water having dissolved substance like
salts, acids, etc. conducts electricity.

2. Water reacts with active metals like Li, Na, Ca, etc. and forms base and hydrogen gas.

2H2O + 2Li 2LiOH + H2
2H2O + 2Na 2NaOH + H2
2H2O + Ca Ca(OH)2 + H2
a layer of rock or soil that can absorb and hold water
aquifer /ˈaekwɪfə(r)/ -

226 Oasis School Science - 9 CHEMISTRY

3. Water decomposes acids, bases and salts into their corresponding ions.
HCl +H2O H+ + Cl–
NaOH +H2O Na+ + OH–
NaCl +H2O Na+ + Cl–

14.5 Solvent Property of Water

Water is a universal solvent. It dissolves various substances like Sodium Chloride (NaCl),
Calcium Chloride (CaCl2), Sodium Nitrite (NaNO3), Copper Sulphate (CuSO4), etc. Different
types of acids, bases, and salts, etc. dissolve in water. Most of the organic compounds and
covalent compounds do not dissolve in water. But the covalent compound like HCl, alcohol,
glucose, urea, etc. dissolve in water. However, covalent compounds like carbon tetrachloride
(CCl4), methane (CH4), ether (CH3-O-CH3), etc. do not dissolve in water.

14.6 Uses of Water

1. Water is used for drinking, cooking, bathing, washing, cleaning, etc.
2. Water is used to run factories.
3. Water is used for irrigation.
4. Water is used to generate hydroelectricity.
5. Water is used by green plants for photosynthesis.
6. Water is used for swimming, rafting, boating, etc.
7. Water is used to produce various substances, metals and oil.
8. Water is used for jet cutting, i.e. the process of cutting wood, rubber, etc. by passing

water in very high pressure.

9. Water is used in laboratory to make solution.

14.7 Types of Water

On the basis of salts of calcium and magnesium, water is classified into two types, viz. soft
water and hard water.

Soap is used to wash clothes. Whenever we get enough amount of foam or lather by applying
a little soap, we say that the water is soft. But water from some sources like rivers, ponds,
lakes, instead of producing foam, forms sticky particles. Such water is called hard water.

Hardness of water is due to the presence of soluble salts of calcium and magnesium, viz.
chloride, sulphate and bicarbonate salts of calcium and magnesium.

The water that does not contain chloride, sulphate and bicarbonate salts of calcium and
magnesium is called soft water. It produces lather with soap easily. Rain water and distilled
water are some examples of soft water.

The water that contains the chloride, sulphate and bicarbonate salts of calcium and magnesium
is called hard water. It does not produce lather with soap easily. So hard water leads to wastage
of soap. The water of wells, rivers, oceans, etc. is hard.

CHEMISTRY Oasis School Science - 9 227

On the basis of salts dissolved, hardness of water is of two types:
i. Temporary hardness ii. Permanent hardness

i. Temporary hardness
The hard water containing bicarbonate salts of calcium and magnesium is called tempo-

rary hard water. Such type of water is tasty while drinking and makes our bones healthy.
This type of hardness can be removed easily.

Removal of temporary hardness of water

Temporary hardness of water can be removed easily by boiling the water or treating with
lime-water.

a. By boiling water

When the temporary hard water is boiled, the soluble bicarbonate salts of calcium and
magnesium get converted into water insoluble bicarbonate salts and settle down at the
bottom of the container. These insoluble salts can be filtered away.

Calcium bicarbonate heat Calcium carbonate + Water + Carbon dioxide
Ca(HCO3)2 ∆ CaCO3 + H2O + CO2↑

Magnesium bicarbonate heat Magnesium carbonate + Water + Carbon dioxide
∆ MgCO3 + H2O + CO2↑
Mg(HCO3)2

b. By treating with lime-water

Temporary hardness of water can also be removed by adding lime water or slaked lime
into the hard water. Calcium hydroxide, i.e. lime water reacts with bicarbonate of calci-
um and magnesium and forms insoluble calcium carbonate which makes the water soft.
This method is called Clark's method.

Calcium bicarbonate + Calcium hydroxide Calcium carbonate + Water

Ca(HCO3) 2 + Ca(OH)2 2CaCO3 + 2H2O

Magnesium bicarbonate + Calcium hydroxide Calcium carbonate + Water + Magnesium hydroxide

Mg(HCO3)2 + 2Ca(OH)2 2CaCO3 + 2 H2O + Mg(OH)2

ii. Permanent hardness

The hard water containing chloride and sulphate salts of calcium and magnesium is
called permanent hard water.

Removal of permanent hardness of water

Permanent hardness of water can be removed by treating the hard water with
washing soda and permutit process.

a. By treating hard water with washing soda

When permanent hard water is treated with washing soda or sodium carbonate, the
salts present in it change into carbonates and water becomes soft. The chemical reactions
involved in this process are given below:

Calcium chloride + Sodium carbonate Calcium carbonate + Sodium chloride

CaCl2 + Na2CO3 CaCO3 + 2NaCl

228 Oasis School Science - 9 CHEMISTRY

Calcium sulphate + Sodium carbonate Calcium carbonate + Sodium sulphate

CaSO4 + Na2CO3 CaCO3 + Na2SO4

Magnesium chloride + Sodium carbonate Magnesium carbonate + Sodium chloride

MgCl2 + Na2CO3 MgCO3 + 2NaCl

Magnesium sulphate + Sodium carbonate Magnesium carbonate + Sodium sulphate

MgSO4 + Na2CO3 MgCO3 + Na2SO4

b. By permutit process

In permutit process, the permanent hard water Hard water Sodium chloride

is passed through sodium aluminosilicate Zeolite
Column
(Na2Al2SiO8) or sodium zeolite (Na2–Z). Soft water
When hard water passes through the zeolite

or permutit, the calcium and magnesium ions

of hard water get replaced by sodium ions of

permutit. As a result, water becomes soft.

The chemical reactions involved in permutit Finegravel

method are given below: Fig. 14.5 Permutit process to remove hardness of water



Sodium zeolite + Calcium chloride Calcium zeolite + Sodium chloride

Na2–Z + CaCl2 Ca – Z + 2NaCl
Magnesium zeolite + Sodium chloride
Sodium zeolite + Magnesium chloride

Na2 – Z + MgCl2 Mg–Z + 2NaCl
Calcium zeolite + Sodium sulphate
Sodium zeolite + Calcium sulphate

Na2 – Z + CaSO4 Ca–Z + Na2SO4

Sodium zeolite + Magnesium sulphate Magnesium zeolite + Sodium sulphate

Na2–Z + MgSO4 Mg–Z + Na2SO4

Activity 2

To demonstrate that temporary hardness can be removed by boiling water

• Take a beaker and put some water into it.
• Add one spoon of calcium bicarbonate or magnesium bicarbonate into the water and

stir with a glass rod.
• Now, add a few drops of shampoo or solution of soap into the beaker and observe

whether lather is formed or not.
• The water does not produce lather. It proves that the water is hard.
• Now, boil the water in the beaker and allow it to cool.
• Again, add a few drops of shampoo or solution of soap and stir with a glass rod.

Observe whether lather is formed or not. The water produces lather with soap after
boiling. It proves that temporary hardness of water can be removed by boiling.

CHEMISTRY Oasis School Science - 9 229

Activity 3

To demonstrate that permanent hardness of water can be removed by adding washing
soda

• Take a beaker and put some water into it. Add some calcium chloride or magnesium
chloride into it and stir.

• Now add 2-3 drops of shampoo or solution of soap into the beaker and stir it with a
glass rod. The water does not produce lather with soap as it is a hard water.

• Now, add some sodium carbonate into the beaker and stir the mixture with a glass rod.

• Again, put a few drops of solution of soap and stir. Observe whether the water forms
lather with soap or not.

• After adding sodium carbonate or washing soda, the water produces lather with
soap. This activity proves that permanent hardness of water can be removed by
using washing soda.

SUMMARY

• Water is one of the most important and abundant substances needed by living
beings. It covers approximately 70% of the earth's surface.

• The dead sea contains about 33.7% of salt. So it is too salty and hence organisms
cannot survive in dead sea. But living beings float on dead sea due to high density
of sea water.

• The sources from which we get water are called sources of water. From these sources
we get water for drinking.

• The sources of water which are found below the surface of the earth are called
ground water sources.

• An underground layer of permeable rock, sediment, or soil that yields water is
called aquifer.

• Pure water is colourless, odourless and tasteless.

• Water exists in solid, liquid and gaseous states.

• Water reacts with active metals like Li, Na, Ca, etc. and forms base and hydrogen
gas.

• The water that does not contain chloride, sulphate and bicarbonate salts of calcium
and magnesium is called soft water.

• The water that contains the chloride, sulphate and bicarbonate salts of calcium and
magnesium is called hard water.

• The hard water containing bicarbonate salts of calcium and magnesium is called
temporary hard water.

• The hard water containing chloride and sulphate salts of calcium and magnesium
is called permanent hard water.

230 Oasis School Science - 9 CHEMISTRY

Exercise

Group-A
1. What is water? Name any two sources of water.
2. What are sources of water? List the sources of water found on the earth.
3. Name any two surface water sources.
4. What is underground water? How does it come on the surface?
5. What is aquifer?
6. What is "water table"?
7. Write any two physical properties of water.
8. What is meant by "solvent property of water"?
9. Name any two ionic compounds that do not dissolve in water.
10. Name any two covalent compounds that dissolve in water.
11. Write any two utilities of water.
12. What is soft water?
13. What is hard water?.
14. Name any four chemical substances found in hard water.
15. What is temporary hardness of water?
16. Name any four chemical substances found in hard water.
17. What is permanent hardness of water?
18. What is Clark's method?
19. What is permutit it method?
20. What is brine? Why is it used?

Group-B
1. What is meant by cohesive property of water?
2. What is meant by adhesive property of water?
3. Write any two differences between rain water and sea water.
4. How can you identify soft water and hard water using a soap?
5. Differentiate between hard water and soft water.

CHEMISTRY Oasis School Science - 9 231

6. Differentiate between temporary hard water and permanent hard water.

7. Why is water called universal solvent?
Group-C

1. What is underground water? How does it come on the surface? Write any two utilities
surface water sources.

2. What happens when sodium metal is kept in water? Write with a balanced chemical
reaction. What is soft water? Write with one example.

3. Write down the utility of brine. Describe in brief the importance of water in our body.

4. How is the permanent hardness of water removed by using washing soda? Write with
chemical equations.

5. Which methods are used to remove temporary hardness of water? Write any two
chemical properties of water.
Group-D

1. How is temporary hardness of water removed? Write with chemical equations.

2. Describe any two methods for removing permanent hardness of water.

3. What is permutit method? Write in brief. Draw a neat and labelled figure showing
permutit method.

4. Write short notes on:

i. Surface water sources

ii. Ground water sources

232 Oasis School Science - 9 CHEMISTRY

UNIT 15 Estimated teaching periods

Theory 5

Practical 0

Chemical fertilizers Chemical fertilizers
used in agriculture

Objectives

After completing the study of this unit, students will be able to:

• introduce chemical fertilizers and state their types with examples.
• describe the uses of nitrogen, phosphorus and potassium fertilizers.

15.1 Introduction

Farmers use a variety of organic and inorganic substances to increase the fertility of soil. These
substances are called fertilizers. These substances supply nutrients which are essential for the
growth and development of plants. Fertilizers are those water soluble substances which are
used in the soil to increase crop production by supplying essential nutrients. When the same
types of plants are grown for a long time, the fertility of soil decreases. So, for the purpose of
continuous use of soil and to maintain crop production, it is necessary to use the fertilizers. A
good fertilizer or complete fertilizer always provides essential elements to the growing plants
as well as nourishes the micro-organisms.

Fig. 15.1 Chemical fertilizers

The population of the world is increasing at a high rate but the productivity of crops is
decreasing which results in food crisis. Therefore, a variety of fertilizers should be used to
increase the productivity of crops.

fertilizer /ˈfəːtɪlʌɪzə/ - a substance added to soil to make plants grow more successfully

CHEMISTRY Oasis School Science - 9 233

Fertilizers enhance the growth and development of plants. Plants need three main
macronutrients, viz. Nitrogen (N), Phosphorus (P) and Potassium (K), three secondary
macronutrients, viz. calcium (Ca), magnesium (Mg) and sulphur (S) and micronutrients like
copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), boron (B), etc. These
macronutrients and micronutrients are found in soil which are absorbed by roots of green
plants.

In this unit, we will study the fertilizers used in agriculture, types of fertilizers, organic or
inorganic fertilizers, chemical fertilizers, their types with examples and effects on plants due
to lack of these fertilizers in brief.

15.2 Types of Fertilizers

Fertilizers are classified in many ways. On the basis of source or chemical nature, fertilizers
are of two types, viz. (i) organic fertilizers and (ii) inorganic fertilizers or chemical fertilizers.

i) Organic Fertilizers

Fertilizers which are obtained from dead, decayed and decomposed parts of animals and
plants or their waste products are called organic fertilizers or manure. Organic fertilizers
are soil suitable fertilizers because they provide all the essential elements to the growing
plants without changing the composition of soil. There are two types of organic fertilizers
or manures.

a. Green manure: Green manures are the green plants which are grown, ploughed
and mixed in the soil to provide essential nutrients to the growing plants. Green
manures supply essential elements which are required for the growing plants and
also check soil erosion. The leguminous and non-leguminous plants are grown,
ploughed and decomposed to get organic matter which is also called humus.

b. Compost manure: Compost manure is an organic fertilizer which is made from
dead, decayed and decomposed parts of animals and plants or their waste
products. To prepare compost manure, mixture of dead plants, animals or their
waste products are kept in a pit with altering layers of soil. Sometimes, little
amount of lime is also added to the mixture. Due to microbial action, the mixture
gets decomposed into compost manure. It is used in the soil to provide essential
elements for the growing plants.

Advantages of Organic Fertilizer

The main advantages of organic fertilizer are given below:

i) It increases the fertility of soil.

ii) It increases water retaining capacity of the soil.

iii) It helps to control soil erosion.

iv) It helps to control environment pollution.

v) It does not affect the quality of soil.

234 Oasis School Science - 9 CHEMISTRY

Disadvantages of Organic Fertilizer
The major disadvantages of organic fertilizer are as follows:
i) It does not dissolve completely in water. So plants cannot absorb it easily.
ii) It does not contain all nutrients required for plants.
iii) It is difficult to collect and transport due to its large mass.

(a) Green manure Fig. 15.2 (b) Compost manure

ii) Inorganic Fertilizers or Chemical Fertilizers

The man-made chemical (or inorganic) substances which are added to the soil to
increase crop production by supplying essential elements are called chemical fertilizers.
Chemical fertilizers (or inorganic fertilizers) supply mostly Nitrogen (N), Phosphorus
(P) and Potassium (K) as the chief elements. They are needed for growth, development
and seed production. On the basis of element present, there are three types of chemical
fertilizers. They are (i) Nitrogenous fertilizers (ii) Phosphorus fertilizers and (iii)
Potassium fertilizers.

Nitrogenous fertilizer Potassium fertilizer Phosphorus fertilizer

Fig. 15.3

1. Nitrogenous fertilizers: Fertilizers which contain nitrogen are called nitrogenous
fertilizers. For example,

i. Urea [NH2CONH2]
ii. Ammonium sulphate [(NH4)2SO4]
iii. Ammonium nitrate [NH4NO3]
iv. Calcium cyanide [Ca(CN)2]

CHEMISTRY Oasis School Science - 9 235

Importance of nitrogen (Nitrogenous fertilizer)
Nitrogen helps in the formation of protein, protoplasm and chlorophyll in the plants. It

is essential for rapid growth and to yield more crops. Deficiency of nitrogen results in
poor development of flowers, fruits and seeds. Leaves become yellow and flowers do not
bloom properly.

2. Phosphorus fertilizers: Fertilizers which contain phosphorus are called

phosphorus fertilizers. For example,

i. Ammonium phosphate [(NH4)3PO4]
ii. Calcium super phosphate [Ca(H2PO4)2.2CaSO4]
iii. Triple super phosphate [3Ca(H2PO4)2]
iv. Bone meal

Importance of phosphorus (Phosphorus fertilizer)

Phosphorus helps in the ripening of fruits and development of seeds. It is also important in
synthesis of protein, cell division and growth of leaves and buds. Phosphorus also helps to
resist diseases.

3. Potassium fertilizers: Fertilizers which contain potassium are called potassium
fertilizers. For example,

i. Potassium chloride (KCl)
ii. Potassium nitrate
iii. Potassium sulphate (KNO3)
iv. Potassium carbonate (K2SO4)
(K2CO3)

Importance of potassium (Potassium fertilizer)

Potassium helps in photosynthesis and growth of flowers. It also helps in protein
synthesis, cell division, food production, etc. Due to deficiency of potassium, leaves and
buds wither and immunity is also reduced.

Differences between Organic fertilizers and Chemical (inorganic) fertilizers

S.N. Organic Fertilizers S.N. Chemical (Inorganic) Fertilizers
They are man-made inorganic
1. They are obtained from dead, 1. substances.
decayed and decomposed parts
of animal and plant or their waste They are soluble in water.
products.
They supply sufficient amount of
2. They are not soluble or less soluble 2. nitrogen, phosphorus and potassium to
in water. the growing plants.

3. They do not supply sufficient 3. Plants absorb them very fast.
amount of nitrogen, phosphorus
and potassium to the growing
plants.

4. Plants absorb them very slowly. 4.

236 Oasis School Science - 9 CHEMISTRY

15.3 Groups of Fertilizers

According to the number of basic nutrients supplied, there are three groups of fertilizers. They are:

a. Single fertilizers: The fertilizers which supply only one basic nutrient, i.e. nitrogen
or phosphorus or potassium are called single fertilizers. Examples: Calcium nitrate,
potassium chloride, potassium sulphate, etc.

b. Mixed fertilizers: The fertilizers which supply more than one basic nutrient are called
mixed fertilizers. Examples: Potassium nitrate, ammonium phosphate, etc.

c. Complete fertilizers (NPK fertilizers): The fertilizers which supply all the basic
nutrients, i.e. nitrogen, phosphorus and potassium are called complete fertilizers. They
are made by mixing two or more than two single fertilizers or mixed fertilizers.

15.3 Groups of fertilizers

15.4 Disadvantages of Using Fertilizers

We should not use excessive amount of chemical fertilizers because it causes water and soil
pollution. When nitrogenous fertilizers reach the water body, they cause rapid growth and
development of aquatic plants. They use up available oxygen of the water and create deficiency
of oxygen in water. So, aquatic animals die due to the lack of oxygen. Similarly, when children
drink nitrogen containing water, they become dwarf.

15.5 Precautions While Using Fertilizers

i. We should not use excessive amount of fertilizers which may damage the plants.
ii. Nitrogenous fertilizers having easy burning nature cause fire when they come in

contact with wooden dust, coal, dry leaves, etc.
iii. Hydroscopic fertilizers like urea should be stored away from the moist places.
iv. Chemical fertilizers should be stored away from the reach of the children.

v. They should be used after testing the soil.

15.6 Advantages of Inorganic/Chemical Fertilizers

The major advantages of chemical fertilizers are as follows:
i. Chemical fertilizers are easy to collect and transport from one place to another.
ii. They increase the fertility of soil.
iii. They contain most of the nutrients essential for growth and development of plants.
iv. They are water soluble. So, they can be absorbed by plants easily.

CHEMISTRY Oasis School Science - 9 237

15.7 Disadvantages of Inorganic/Chemical Fertilizers

(i) Chemical fertilizers cause environment pollution.
(ii) They increase acidity or alkalinity of soil.
(iii) They affect the quality of soil.

Activity 1

• Pay a visit to your locality and meet some local farmers.
• Ask the technique of making compost manure and green manure to the farmers.
• Prepare a short report and submit to your science teacher.
• Also, prepare a list of inorganic or chemical fertilizers that are used in your locality.

SUMMARY

• Fertilizers are the organic or inorganic substances which are used in soil to increase
crop production by supplying essential nutrients.

• On the basis of source or chemical nature, there are two types of fertilizers. They are
organic fertilizers and inorganic or chemical fertilizers.

• Fertilizers which are obtained from dead, decayed and decomposed parts of plants
and animals are called organic fertilizers.

• The man-made inorganic or chemical substances which are added to soil increase
crop production are called inorganic or chemical fertilizers.

• Nitrogenous, phosphorus and potassium fertilizers are the main inorganic fertilizers

• The fertilizers containing all three types of nutrients, viz. nitrogen (N), phosphorous
(P) and potassium (K) are called NPK fertilizers.

• The chemical fertilizers containing nitrogen are called nitrogenous fertilizers, e.g.
urea, ammonium sulphate, ammonium nitrate, etc. These fertilizers help in the
formation of protein, protoplasm and chlorophyll in plants.

• The chemical fertilizers containing phosphorous are called phosphorous fertilizers,
e.g. ammonium phosphate, calcium super phosphate, triple super phosphate, etc.
These fertilizers helps in ripening of fruits and development of seeds.

• The fertilizers containing potassium are called potassium fertilizers, e.g. potassium
chloride, potassium, sulphate, potassium nitrate, etc. These fertilizers help in
photosynthesis and growth of flowers.

• On the basis of number of basic nutrients supplied, there are three types of
fertilizers. They are single fertilizers, mixed or double fertilizers and complete or
NPK fertilizers.

• Excessive use of chemical fertilizers causes water and soil pollution. Therefore, we
should reduce the over use of chemical fertilizers.

238 Oasis School Science - 9 CHEMISTRY

Exercise

Group-A
1. What is a fertilizer? Why is it used?
2. What are types of fertilizers? Write.
3. How many types of organic fertilizers are there?
4. What is green organic fertilizer?
5. What are two advantages of organic fertilizers.
6. What is inorganic fertilizer? Write with one example.
7. What is meant by NPK fertilizer?
8. What are nitrogenous fertilizers?
9. What are phosphorus fertilizers?
10. Name any two chemical fertilizers rich in potassium.

Group-B

1. Differentiate between organic fertilizers and inorganic fertilizers.

2. Organic fertilizers are better than inorganic/chemical fertilizers, why?

3. Differentiate between green organic fertilizers and animal organic fertilizers.

4. NPK fertilizer is considered as a complete fertilizer, why?

5. Write any two differences between nitrogenous fertilizers and potassium fertilizers.
Group-C

1. Write any three advantages of inorganic fertilizers.

2. What are types of fertilizers? Write. Write any two disadvantages of inorganic fertilizers.

3. Write any three advantages of organic fertilizers.

4. How many types of organic fertilizers are there? What are they? Write any two
disadvantages of chemical fertilizers.

5. What effects in plants can be seen due to lack of potassium? Write. Write down the
importance of nitrogen for plants.
Group-D

1. Write down the importance of nitrogen for plants. Differentiate between green organic
fertilizer and chemical fertilizer in two points.

2. Describe in brief the importance of phosphorous for plants. Differentiate between green
organic fertilizer and animal organic fertilizer in two points.

3. Describe in brief the importance of potassium for plants. Differentiate between
nitrogenous fertilizer and phosphorus fertilizer in two points.

4. Write down the precautions while using chemical fertilizers. Differentiate between
potassium fertilizer and phosphorus fertilizer in two points.

5. Write a short note on 'Use of chemical fertilizers and its impact on environment."

CHEMISTRY Oasis School Science - 9 239

Compulsory Science

Part 3 : Biology
Scope and sequence of the subject matter

Area Unit Syllabus
Living Beings 1. Classification • Classification of non-flowering and

of Plants and flowering plants (upto-sub division) and
Animals invertebrates and vertebrates (upto class)
• Life cycle of mosquito and harmful effects

2. Adaptation of •Concept of adaptation of plants and
Organisms animals

• Introduction to microorganisms (bacteria,
fungi, viruses and protozoa) and disease
caused by them

3. System • Inter-relationship among cell, tissue,
organ and system

• Types of plant tissue and location

Life Processes in Living 4. Skeletal System • Functions

Beings of Human Body • Classification of bones

Evolution 5. Sense Organs • Sense organs in human body and their
functions
Nature and 6. Human
Environment Nutrition • Human digestive system, respiratory
system and transpiration (introduction
7. Evolution and importance)

8. Nature and • Human digestive system, respiratory
Environment system and transpiration (introduction
and importance)

• Factors affecting plants and animals in
environment

• Effect of climate change
• Autotrophism and heterotrophism
• Human dependency on other organisms

(flood, cloth, shelter)

240 Oasis School Science - 9 BIOLOGY

UNIT 16 Estimated teaching periods

Theory 8

Practical 3

CLASSIFICATION OF

PLANTS AND ANIMALS Carl Von Linnaeus

Objectives

After completing the study of this unit, students will be able to:
• classify plants upto class, invertebrates upto phylum and vertebrates upto

class and explain their characteristics with examples.
• explain the life cycle of mosquito with a neat and labelled figure.
• list the adverse effects of mosquito bite on human beings.

A. Classification of Plants and Animals

16.1 Introduction

The earth is inhabited by millions of plants and animals. It is estimated that there are about
10 million species of organisms on the earth, but only one third of them have been identified
and described to date. The organisms are not only enormous in number but also present in
a considerable diversity of body structure, habits and modes of life. Visualizing such a vast
number of organisms it would be almost impossible to study each and every plant and animal
separately at the individual level. Therefore, different kinds of organisms are arranged in an
orderly and systematic manner into various groups under the species on the basis of their
similarities and differences. Then, species are arranged into higher and higher categories like
genus, family, order, class, phylum, etc. This process is called classification. Thus, classification
can be defined as the method of arranging living organisms into various groups on the basis
of similarities and differences. In classification, the similarities and differences between
organisms are identified and then the organisms having similar characters are placed in the
same group. Biological classification attempts to group living organisms on the basis of how
closely related they are. In fact, there is no need of knowing each and everything about all
living organisms for understanding the living world. We can study a few representatives from
each group which would give us an idea of all members of that group.

16.2 Importance of Classification

1. It helps us in identification and grouping of various organisms. It makes the study of
living organisms easy and systematic.

classification /ˌklasɪfɪˈkeɪʃn/ - the process of grouping of living organisms on the basis of similarities and differences
diversity /daɪˈvɜːsəti/ - a range of many organisms that are very different from each other

BIOLOGY Oasis School Science - 9 241

2. It helps us understand the relationship among different groups of organisms.
3. Classification projects a picture of all life forms at a glance.

4. It gives us the idea about the evolution of organisms.

16.3 Taxonomy: The Science of Classification and Nomenclature

Taxonomy or Systematic Biology is defined as the branch of biological science that deals with
the nomenclature and classification. Taxonomy is concerned with naming and systematically
arranging different species of organisms into closely related groups on the basis of their
relationship. A Swedish scientist Carolus Von Linnaeus (1707-1778 AD) is considered as the
father of taxonomy because he developed the Binomial System of Nomenclature and system
of classification. In 1735 AD, he published a book, Systema Nature, in which he mentioned the
binomial names and the method of classification. The tenth edition of this book published in
1758 AD is still the basis of modern classification.

16.4 Nomenclature: Scientific Naming of Organisms

Nomenclature is the way of providing a scientific name for every living organism. Common
vernacular names for the same organism vary from place to place. For example, the bird which
is known as 'Bhangero' in Nepal is known by different names in different countries. It is called
'Gauraiya' in India, House sparrow in England, Suzune in Japan, Pardal in Spain, Musch in
Holland and so on. These names may not be understood elsewhere. Thus, a need was felt to
assign a particular organism with an internationally acceptable name. Therefore, a simplified
system of naming organisms known as 'Binomial System of Nomenclature' was proposed by
Carolus Linnaeus.

Binomial System of Nomenclature

In Biology, every living being is given two proper names. The first name is the genus to
which the organism belongs whereas the second name is the species to which it belongs. For
example, the scientific name of frog in binomial system is Rana tigrina in which Rana is the
genus, i.e. generic name and tigrina is the species, i.e. specific name. Thus, Binomial System
of Nomenclature can be defined as the scientific method of assigning two names, i.e. generic
name and specific name to an organism.

In Binomial system, both names are usually Greek (Gk.) or Latin (L.) or have Latin endings.
The scientific names are unique, understood and followed all over the world. They are not
changed easily and are guided by a set of rules stated in the International Code of Biological
Nomenclature (ICBN).

S.N. Organisms Scientific names
(in Binomial system)
1. Human being Homo sapiens
2. Frog Rana tigrina
3. Mustard plant Brassica campestris

taxonomy /tækˈsɒnəmi/ - the scientific process of classifying living beings

242 Oasis School Science - 9 BIOLOGY