Science and Environment 10

5. The given figure shows the laboratory preparation of ammonia gas. Answer the follow-
ing questions after observing the given figure.

i) Write the balanced chemical reaction of laboratory preparation of ammonia gas by
this method.

ii) Why is the mouth of hard glass test tube inclined downward?
iii) Which litmus paper (red or blue) can help to confirm that the gas jar is filled with

ammonia gas?
6. Answer the following questions based on the given diagram.

Delivery
tube

dil.HCl

Woulfe’s
bottle

Pieces of
CuCO3

i) Which gas is being collected in the gas jar?
ii) What happens when some lime-water is put in the gas jar?
iii) Write down the balanced chemical equation of the chemical reaction in the forma-

tion of the given gas.

CHEMISTRY Oasis School Science - 10 193

UNIT11 Estimated teaching periods

Theory 6

Practical 2

METALS

Gold

Objectives

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

• define metals and state their properties.
• define minerals and name the ores of different metals (iron, aluminium,

copper, silver and gold).
• describe the physical and chemical properties of iron, aluminium, copper, silver

and gold.
• explain the uses of the above metals.

11.1 Introduction

Metals are elements (except hydrogen) which form electropositive ions by losing electrons.
Metals are good conductors of heat and electricity. They are malleable and ductile. Therefore,
metals are widely used in our daily life. Among the many metals, iron, aluminium, copper,
silver and gold are commonly used in our day-to-day life. Iron and steel are used in construction
works, industries, for making vehicles, cooking utensils, weapons, etc. Aluminium is
extensively used for making household utensils, coins, bodies and parts of aeroplanes, ships,
etc. Copper is widely used for making electric wires, household utensils, coins, etc. Similarly,
silver and gold are also used for making ornaments, medals, coins, idols, etc.

In this unit, we will study the occurrence, ores, extraction, properties and uses of some
common metals: iron, aluminium, copper, silver and gold.

11.2 Minerals

Minerals are those naturally occurring chemical substances Fact File - 1
which contain metals in some amount. For example,
limestone, slate, kaolin, haematite, etc. All minerals are All minerals are not ores but
not suitable for extracting metals because some of them all ores are minerals.

contain very little metal but some contain more amounts

of metals. That is why certain minerals are suitable for extraction of metals. Such minerals are

called ores.

11.3 Ores

Those minerals from which metals can be extracted conveniently and profitably are called ores.
An ore contains a good percentage of metal and there are few impurities in it. For example,

ore /ɔː/ - the mineral form which a metal can be extracted

194 Oasis School Science - 10 CHEMISTRY

magnetite, cuprite, bauxite, etc. All ores are minerals, but all minerals are not ores.

Differences between Minerals and Ores

S.N. Minerals S.N. Ores
1. They contain metals in more amount.
They contain metals in more or less 1.
2. some amount. From all ores, we can extract metals.

3. From all minerals, we cannot extract 2. All ores are minerals.
metals.

All minerals are not ores. 3.

11.4 Metallurgy

Metallurgy is the process by which we can get pure metals from their ores. Metallurgy involves
several steps. The main steps are given below:

i. Crushing of ore: This step is used to convert big pieces of ores into smaller ones.

ii. Powdering of ore: In this step, pieces of ores are converted into powder form.

iii. Concentration of ore: In this step, unwanted earthy substances like soil, sand, limestone,
etc. are removed.

iv. Calcination: By this process, carbonate and hydroxide ores are strongly heated in limited
air below the melting point of a metal to get metallic oxides.

v. Roasting: By this process, sulphide ores are strongly heated in the presence of excess air
below the melting point of metal to get metallic oxides.

vi. Smelting: In this process, we get free metals from their oxides.

vii. Refining of metal: Here, we obtain pure metal by using different types of refining
methods like oxidation, distillation, evaporation, electrorefining, etc.

Iron, aluminium, copper, silver and gold are some important metals used in our daily
life. The occurrence, extraction, properties and uses of these metals are described below:

11.5 Iron

Symbol Fe
Atomic number 26
Atomic weight 56
Valency 2 or 3
Electronic configuration 1s2, 2s2 2p6, 3s2 3p6,3d6, 4s2
Position in periodic table Period = 4, Group = 8

Block = d – Block

Occurrence

Iron is one of the reactive metals. So, it does not occur in a free state in nature. It forms different
types of compounds, like oxides, sulphides, chlorides, hydroxides, carbonates, etc. A little
amount of iron is present in the haemoglobin of our blood.

CHEMISTRY Oasis School Science - 10 195

Ores of Iron

1. Haematite Fe2O3 (chief ore) Fig. 11.1 Haematite ore
2. Magnetite Fe3O4
3. Siderite FeCO3
4. Limonite Fe2O3 . 3H2O
5. Iron pyrite Fe2S3

Among the different ores of iron, haematite contains about 72.5% of iron. It is an easily
available ore. So iron is generally extracted from this ore.

Extraction of iron

Iron is mainly extracted from haematite ore. Haematite ore is collected from ore mines and
crushed into smaller pieces. Those pieces are ground to make a fine powder. Sand, clay, dust,
etc. are removed from the powdered ore by washing it in water. Iron is a magnetic substance,
and the impurities present in it are non-magnetic substances. Thus, non-magnetic dirts are
separated by the electromagnetic separation method. Now, the ore is mixed with coke and
heated strongly in a blast furnace in the presence of excess air below the melting point of
iron. Afterwards, molten iron is obtained, which is 93-95% pure. This iron is further purified
according to need.

Types of iron on the basis of percentage of carbon

S.N. Types of iron Percentage of Characteristics
carbon
1. Cast Iron 2.5 to 4.5% It is hard iron and its melting point is 1200°C.
2. Wrought Iron It is soft iron and its melting point is 1500°C.
3. Steel 1.2 to 2.5% It is hard iron and its melting point is 1300°C.
0.5 to 1.2 %

Physical Properties of Iron
1. Iron is a shiny and gray white, i.e., ash coloured metal.
2. Its specific gravity is 7.86.
3. Its melting point is 15000C and boiling point is 25000C.
4. It is a good conductor of heat and electricity.
5. It is malleable and ductile.
6. It becomes non-magnetic when heated above 7700C.

blast furnace /blɑːst ˈfɜːnɪs/ - a large structure like an oven in which iron ore is melted in order to extract the metal
196 Oasis School Science - 10 CHEMISTRY

Uses of Iron
1. Iron is used to make different types of household utensils.

2. It is used for making rods, pipes, wires, bolts, materials for building construction,
bridges, parts of vehicles, railway tracks, tools, weapons, etc.

3. It is used as a catalyst in various chemical reactions.
4. It is used in the manufacture of steel.

11.6 Aluminium Al
13
Symbol 27
Atomic number 1s2, 2s2 2p6, 3s2 3p1
Atomic weight 3
Electronic configuration Period – 3, Group - 13
Valency Block = p – Block
Position in periodic table

Occurrence

Aluminium is the most abundant metal on the earth's crust. It does not occur in a free state. In
combined state, it is present in different types of compounds, like oxides, fluorides, sulphates,
etc. Aluminium is highly malleable and ductile. Hence, it is used to make foils in packing and
wires of electricity.

Ores of Aluminium

1. Bauxite Al2O3.2H2O (chief ore)
2. Cryolite Na3AlF6
3. Felspar K(AlSiO3.O8)

Extraction of aluminium Fig. 11.2 Bauxite ore

Aluminium is mainly extracted from bauxite ore. First of all, bauxite ore is collected and

crushed into smaller pieces. The pieces of ore are powdered by grinding in a pulverizing

machine. The powdered ore is treated with concentrated sodium hydroxide to get sodium

meta aluminate (NaAlO2). Now the mixture is filtered to remove impurities. Sodium meta
aluminate thus obtained is mixed with dilute hydrochloric acid to produce aluminium

hydroxide [i.e., Al(OH)3]. Here, aluminium hydroxide is separated, dried and heated strongly
to form aluminium oxide, i.e., alumina (Al2O3). The molten alumina is further purified by
electrorefining.

CHEMISTRY Oasis School Science - 10 197

Physical properties of aluminium

1. Aluminium is a bluish-white metal.
2. It is highly malleable and ductile.
3. It is a good conductor of heat and electricity.
4. Its specific gravity is 2.7.

5. Its melting point is 6600C and boiling point is 18000C.

6. It is a light metal.

Reasonable Fact - 1

Though aluminium is a quite reactive metal, it does not react with water, why?
Ans: Though aluminium is a quite reactive metal it does not react with water. This is due
to the presence of an inert aluminium oxide layer on its surface which is formed when
aluminium combines with the oxygen of air. This thin but strong layer prevents the reaction
of aluminium with water.

Reasonable Fact - 2

Aluminium metal is used in making bodies and parts of aeroplanes, why?
Ans: Being a light and rust free metal, aluminium is used for making bodies and parts of
aeroplanes.

Reasonable Fact - 3

Aluminium is used for making silver paint and mirros, why?

Ans: Aluminium powder is used for making silver paint because of its silvery appearance. Since
aluminium is a good reflector, it is deposited on glass to make mirrors.

Uses of aluminium
1. Aluminium is used to make household utensils, body parts of vehicles and aeroplanes.
2. Aluminium foil is used for wrapping foods, cigarettes, pharmaceutical products, etc.
3. It is used for making coins, alloys and overhead electric cables.
4. It is used for making silver paint, mirrors, photo frames, etc.

11.7. Copper

Symbol Cu
Atomic number 29
Atomic weight
Valency 63.57
Electronic configuration 1 or 2
Position in periodic table 1s2, 2s2 2p6, 3s2 3p6, 3d10, 4s1
Period – 4, Group - 11
Block – d – Block

198 Oasis School Science - 10 CHEMISTRY

Occurrence

Less amount of copper is found in a free state in nature. But maximum amount of it is found
in a combined state in the form of sulphides, oxides and carbonates.

Ores of copper

1. Copper pyrite (Chalcopyrite) CuFeS2 (Chief ore)

2. Cuprite Cu2O

3. Chalcocite (copper glance) Cu2S

4. Malachite Cu(OH)2.CuCO3

5. Azurite [Cu(OH)2.2CuCO3] Fig. 11.3 Chalcopyrite ore

Extraction of copper

Copper is extracted from its chief ore, i.e., copper pyrite or chalcopyrite. First of all, copper
pyrite is collected and crushed into smaller pieces. The pieces of ore are converted into a fine
powder with the help of a pulverizing machine. The powdered ore is concentrated by the
froth-floatation process to remove the impurities. After concentration, the ore is roasted in
blast furnace to convert copper sulphide into copper oxide. During the roasting, sulphur
escapes out in the form of sulphur dioxide (SO2). The unoxidised copper sulphide (CuS) and
oxidised copper oxide (CuO) are mixed together and passed in the same furnace. Now, this
mixture is heated strongly in the absence of air to obtain about 99.4% pure molten copper,
which is called blister copper. The blister copper is further purified by electrorefining.

Physical properties of copper
1. It is a hard reddish brown metal.
2. It is a good conductor of heat and electricity.
3. It is malleable and ductile.
4. Its specific gravity is 8.95.

5. Its melting point is 10830C and boiling point is 2350° C.

Uses of copper
1. Copper is used to make household utensils, like cooking utensils, boilers, kettles, etc.
2. It is used to make electric wires and cables.
3. It is used for electroplating and electrotyping.
4. Copper salts are used as insecticides, fungicides and germicides.
5. It is used for making alloys like brass, bronze, etc.
6. It is used to make coins.

pulverize /ˈpʌlvəraɪz/ - to crush sth into fine powder

CHEMISTRY Oasis School Science - 10 199

7. Copper is used to make different types of alloys. Some common alloys of copper with
their composition and uses are given below:

Alloys Composition Uses

1. Brass Cu + Zn To make nut bolts, condenser tubes and medals

2. German Silver Cu + Zn + Ni To make utensils and bells

3. Bronze Cu + Zn + Sn To make household utensils and coins

4. Gun metal Cu + Sn + Zn + Pb To make ball bearings and parts of machines

5. Bell metal Cu + Zn To make bells and decorative items.

11.8 Silver

Symbol Ag
Atomic number
Atomic weight 47
Valency 107.88
Electronic configuration 1
Position in periodic table 1s2, 2s2 2p6, 3s2 3p6, 3d10 , 4s2, 4p6, 4d10, 5s1
Period – 5, Group - 11
Block = d – Block

Occurrence

Silver is a less reactive metal. It occurs in both free and combined state. In combined state, it
occurs in the form of sulphide and chloride.

Ores of Silver

1. Argentite (silver glance) Ag2S
2. Horn silver AgCl

3. Silver copper glance (AgCu)2S
4. Ruby silver (Pyrolite) 3Ag2S.Sb2S3

Fig. 11.4 Argentite ore

Extraction of silver

Silver is extracted from Argentite ore. The ore is crushed and pulverized to get a fine powder.
It contains sulphur, so it is concentrated by the froth-floatation process. The concentrated ore
is mixed with sodium cyanide and heated in a furnace in the presence of air to get sodium
argento-cyanide. Now, zinc is added to the argento-cyanide solution to displace silver in the
form of a silver precipitate. Then, silver is obtained by filtration, and it is further purified by
electrorefining.

alloy /ˈalɔɪ/ - a substance formed by mixing two or more metals or metals and non-metals

200 Oasis School Science - 10 CHEMISTRY

Physical properties of silver
1. It is a shiny white metal.
2. It is a good conductor of heat and electricity.
3. It is malleable and ductile.
4. Its specific gravity is 10.5.
5. Its melting point is 960°C and boiling point is 1955°C.

Uses of silver
1. Silver is used to make jewelry and other valuable ornaments.
2. It is used to make coins, medals, idols, statues, etc.
3. It is used for silver plating.
4. Silver salt (like silver bromide- AgBr) is used in photography.
5. Silver alloy is used for silver mirror and for filling teeth.

6. Silver nitrate and other silver compounds are used as laboratory reagent.

11.9 Gold

Symbol Au

Atomic number 79
Atomic weight 197.2
Valency 1 or 3
Electronic configuration 1s2, 2s2 2p6, 3s2 3p6, 3d10,4s2 4p6 4d10, 4f14, 5s2 5p6 5d10, 6s1
Position in periodic table Period – 6, Group - 11
Block – d – Block

Occurrence

Gold is a less reactive metal. So, it is found in a free state in nature. It is found in reef gold
mixed with quartz or alluvial soil eroded by the river.

Ores of gold

Gold is present in alluvial sand or alluvial soil or quartz veins and calaverite (AuTe2).

Extraction of gold

Gold is extracted from alluvial soil or sand rich in gold. The gold
containing soil is mixed with water and run on a sluice. The particles
of gold get trapped in the cavities of the sluice, which is separated
from the sand.

Fact File - 2 Fig. 11.5 Calaverite ore

Gold is a less reactive metal. Therefore, it is found in a free state in nature.

alluvial /əˈluːvɪəl/ - made of sand and soil that is left by rivers or floods
sluice /sluːs/ - a sliding gate for controlling the flow of water

CHEMISTRY Oasis School Science - 10 201

Physical properties of gold
1. Gold is a yellow shining metal.
2. It is a good conductor of heat and electricity.
3. It is a heavy metal with specific gravity 19.3.
4. Its melting point is 1063°C and boiling point is 2530°C.

Fact File - 3

Gold is a less reactive metal, so it does not react with common chemical reagents like
air, water, acids, etc. However, it gets dissolved in aqua regia. A mixture of 3:1 ratio of
concentrated hydrochloric acid and concentrated nitric acid is known as aqua regia. It is
also called kingly water because it dissolves gold to give gold chloride (AuCl3).

Reasonable Fact-4

Gold is found in a pure state in nature but not iron, why?

Ans: Gold is a noble metal. It does not react with air, water, acids and other chemicals in
normal temperature and pressure. So gold is found in a pure state. But iron combines with
air, acids and other chemicals in ordinary condition to form various types of compounds.
So iron is not found in a pure state in nature.

Reasonable Fact-5

Why is gold called noble metal or neutral metal?
Ans: Gold does not react with air, water, acids and other chemicals in normal temperature
and pressure. So gold is called a noble metal or neutral metal.

Uses of gold

1. Gold is used for making jewellery, statues and other ornaments.
2. It is used for making medals, coins, etc.
3. It is used for gold plating.
4. It is used for making a gold leaf electroscope.
5. It is used for filling teeth.
6. Compounds of gold are used in the laboratory, medicines and photography.

11.10 Occurrence of Metals in Nepal

Different types of metals are found in different parts of Nepal. A brief description of metals
found in Nepal is given below:

Metals Ores Districts
1. Iron Magnetite
Lalitpur, Tanahun, Bhojpur, Ramechhap,
2. Copper Haematite Pyuthan, Chitwan
Chalcopyrite
Copper glance Udayapur, Dhading, Makawanpur,
Solukhumbu

202 Oasis School Science - 10 CHEMISTRY

3. Gold Sandy alluvial soil, free gold Rapti, Mustang, Kathmandu
4. Magnesium
5. Cobalt Magnesite Udayapur, Dolakha
6. Calcium
Cobaltite Palpa, Gulmi
7. Bismuth
8. Lead Limestone Kathmandu, Udayapur, Dhading,
Makawanpur

Bismuth Makawanpur (Bhimphedi)

Lead deposit Lalitpur, Ganesh Himal (Rasuwa)

SUMMARY

• Metals are electropositive elements that are malleable, ductile, shiny and a good
conductor of heat and electricity.

• Minerals are naturally occurring chemical substances which have metals in some
amount.

• Ores are those minerals which contain metals in a large quantity.
• Metallurgy is the process by which we get metal from their respective ores.
• Metals are widely used in our daily life. Iron, aluminum, copper, silver and gold are

the most common metals that we use.
• Metals are used for making utensils, weapons, vehicles, buildings, bridges,

ornaments, etc.

• The ores of some metals are given below:

Metal Ores
Iron
Haematite (Fe2O3)
Aluminium Magnetite (Fe3O4)
Siderite (FeCO3)
Copper Limonite (Fe2O3.3H2O)
Bauxite (Al2O3. 2H2O)
Silver Cryolite (Na3AlF6)
Gold Felspar [(K(AlSIO3. O8)]
Copper pyrite or chalcopyrite (CuFeS2)
Chalcocite or copper glance (Cu2O)
Malachite [Cu(OH)2. CuCO3]
Argentite (Ag2S)
Horn silver (AgCl)

Alluvial soil or Alluvial sand or Quartz veins and Reef gold

• Silver, copper and gold are called coinage metals because they are used to make coins.
• A mixture of 3:1 ratio of concentrated HCl and concentrated HNO3 is called aqua

regia or kingly water.

CHEMISTRY Oasis School Science - 10 203

Exercise9. Zinc Lalitpur, Ganesh Himal (Rasuwa)
Zinc deposit

Group-A

1. Name any two ores of iron.

2. Write any two physical properties of iron.

3. Name the chief ores of aluminium.

4. Write any two physical properties of iron.

5. Name the chief ores of copper.

6. Write any two physical properties of copper.

7. Name any two ores of silver.

8. Write any two physical properties of silver.

9. Where and in which state is gold found in nature?

10. Write any two physical properties of gold.

11. Name the metal that can be obtained from the given ores:

i) Calverite ii) Limonite

12. Name the metal that can be obtained from the given ores:

i) Pyrolite ii) Haematite

13. In which parts of Nepal are given metals found? Write.

i) Iron ii) Gold

14. In which parts of Nepal are given metals found? Write.

i) Magnesium ii) Cobalt

15. Which metal is obtained from bauxite?

16. Name a metal which can be obtained from argentite.

17. Which metals can be extracted from magnetite and chalcopyrite?

Group-B

1. Iron is used for making cooking utensils, why?

2. Aluminium is used for making body parts of aeroplanes, why?

3. Copper is used for making electric wires, why?

4. Gold is called an inert metal, why?

5. Write any two differences between iron and aluminium.

6. Why are gold and silver used for making ornaments?

7. Why aluminimum tools are not affected by air and water?

8. Aluminum is used to make parts of an aeroplane. Give any two reasons.

204 Oasis School Science - 10 CHEMISTRY

9. Aluminum is a very reactive metal. However, the foods in aluminium pots don’t react
with the pots? Give reason.

10. State any two properties of copper that make it suitable for making pots and pans.
Group-C

1. Write any three uses of iron.
2. Write down the major uses of aluminum.
3. What are the uses of copper?
4. Write any three uses of silver.
5. Write down the main uses of gold.
6. Write any three utilities of metals in our daily life.

Group-D
1. Write down the electric configuration of iron and mention the position of iron in the

modern periodic table.
2. How is iron extracted? Describe in brief.
3. How is gold extracted? Describe in brief?
4. Arrange aluminum, iron, gold, silver and copper in the increasing order of their melting

points and boiling points.
5. Write a short note on occurrence of metals in Nepal.

CHEMISTRY Oasis School Science - 10 205

UNIT12 Estimated teaching periods

Theory 4

Practical 1

HYDROCARBON AND

ITS COMPOUNDS Methane

Objectives

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

• define hydrocarbons and explain their forms.

• explain the structure and uses of some organic compounds (methane,
ethane, propane, butane, alcohol, glycerol and ether).

12.1 Introduction

Compounds which are formed by the combination of carbon and hydrogen are called

hydrocarbons. For example, methane (CH4), ethane (C2H6), propane (C3H8), ethene (C2H4),
ethyne (C2H2), etc. These compounds are formed by bonding between carbon and hydrogen.
So they are called hydrocarbons. The main sources of hydrocarbons are petroleum and natural

gas. Hydrocarbons are classified into two groups. They are:

a) Saturated hydrocarbons b) Unsaturated hydrocarbons

12.2 Saturated Hydrocarbons

The hydrocarbons in which carbon atoms are connected by a single covalent bond are called

saturated hydrocarbons. They are also called alkanes. For example, methane (CH4), ethane
(C2H6), propane (C3H8), etc. The general formula of saturated hydrocarbons is CnH2n+2 where 'n'
represents the number of carbon atoms. In an alkane, the suffix is 'ane'. Some more examples

of alkanes with their molecular formula, structural formula and IUPAC name are given below:

S.N. No. of carbon Moleular Structural formula IUPAC name
1. atoms formula Methane
CH4 H
1 (Meth) I Ethane
H–C–H
2. 2 (Eth) C2H6 I
H
HH
II
H–C–C–H
II
HH

alkane /ˈælkeɪn/ - a saturated hydrocarbon having a single covalent bond between carbon atoms

206 Oasis School Science - 10 CHEMISTRY

3. 3 (Prop) C3H8 HHH Propane
Butane
4. 4 (But) C4H10 III Pentane
H–C–C–C–H Hexane
5. 5 (Pent) C5H12 Heptane
II I Octane
6. 6 (Hex) C6H14 HHH Nonane
HHHH Decane
7. 7 (Hept) C7H16 IIII

8. 8 (Oct) C8H18 H–C–C–C–C–H
IIII
9. 9 (Non) C9H20 HH H H

10. 10 (Dec) C10H22 H HH H H
I I II I
H–C–C–C–C–C–H
I I II I
HHHH H
H HHHHH
I II II I
H–C–C–C–C–C–C–H
I I II II
H H H H HH
H H HH H H H
I IIII II
H–C–C–C–C–C–C–C–H
I II II I I
H HH H H H H
H H H HHH H H
I I I IIII I
H–C–C–C–C–C–C–C–C–H
I I II II II
H H H H H H HH
H H H H HH H H H
I I II III II
H–C–C–C–C–C–C–C–C–C–H
I I I I IIIII
HHHHHHHHH
HHHHHHHHHH
II I II II II I
H–C–C–C–C–C–C–C–C–C–C–H
II I I II II II
HHHHHHHHHH

Saturated hydrocarbons, i.e. alkanes are chemically less reactive. So, they are also called
paraffins (para-less, affins-reactivity).

12.3 Unsaturated Hydrocarbons

The hydrocarbons in which carbon atoms are connected by a multiple (either double or triple)
covalent bond are called unsaturated hydrocarbons. For example, ethene (C2H4), propene
(C3H6), ethyne (C2H2), propyne (C3H4), etc. Unsaturated hydrocarbons are of two types.

a) Alkenes b) Alkynes

CHEMISTRY Oasis School Science - 10 207

a) Alkenes: The unsaturated hydrocarbons in which any two carbon atoms are connected
by a double covalent bond are called alkenes. The general formula of alkene is CnH2n
where 'n' represents the number of carbon atoms. The suffix of alkenes is -ene.

The molecular formula, structural formula and IUPAC name of some alkenes are given
below:

S.N. No. of carbon Molecular Structural formula IUPAC
name
atoms formula Ethene
Propene
1. 2 (Eth) C2H4 HH
C=C Butene

HH Pentene

2. 3 (Prop) C3H6 H H Hexene
I
H–CI –CI = C Heptene
HH H
Octene
3. 4 (But) C4H8 HI HI H Nonene
Decene
H–C–C–C=C
III
HHH H

4. 5 (Pent) C5H10 HI HI HI H

H–C–C–C–C=C
IIII
HHHH H

5. 6 (Hex) C6H12 HHH H H
III I
H–C–C–C–C–C=C
IIII I
HHHH H H

6. 7 (Hept) C7H14 HHH HH H
III II
H–C–C–C–C–C–C=C
IIII I I
HHHH H H H

7. 8 (Oct) C8H16 H H H H HH H
I I I I II
H–C–C–C–C–C–C–C =C
IIII I II
HHHH H HH H

8. 9 (Non) C9H18 HH H H H HH H
II I I I II
H–C–C–C–C–C–C–C–C=C
IIIII I II
HHHHH H HH H

9. 10 (Dec) C10H20 HHH H H H HH H
III I I I II
H–C–C–C–C–C–C–C–C–C=C
IIIIII I II
HHHHHH H HH H

208 Oasis School Science - 10 CHEMISTRY

Alkenes are also called olefins because they react with chlorine and produce oil-like
substances.

b) Alkynes: The unsaturated hydrocarbons in which any two carbon atoms are connected
by a triple covalent bond are called alkynes. The general formula of alkyne is CnH2n-2. The
suffix of alkynes is '-yne'.

The molecular formula, structural formula and IUPAC name of some alkynes are given
in the table below:

S.N. No. of Molecular Structure IUPAC
carbon atoms formula name
1. 2 (Eth) H–C ≡ C–H Ethyne
2. C2H2 Propyne
3 (Prop) C3H4 H
I Butyne
3. 4 (But) C4H6 H – C–C ≡ C – H
I Pentyne
4. 5 (Pent) C5H8 H
Hexyne
5. 6(Hex) C6H10 HH
II Heptyne
6. 7 (Hept) C7H12 H – C–C–C ≡ C – H
II Octyne
7. 8 (Oct) C8H14 HH

HHH
III
H – C–C–C–C ≡ C – H
III
HHH

HHHH
IIII
H – C–C–C–C–C ≡ C – H
IIII
HHHH

HHHHH
IIIII
H – C–C–C–C–C–C ≡ C – H
IIIII
HHHHH

H HHH HH
I III II
H – C–C–C–C–C–C–C ≡ C – H
I III II
H HHH HH

8. 9 (Non) C9H16 H HHH HH H Nonyne
I III II I
H – C–C–C–C–C–C–C–C ≡ C–H
I III II I
H HHH HH H

CHEMISTRY Oasis School Science - 10 209

9. 10 (Dec) C10H18 H H H H HH HH Decyne
I I I I II II
H – C–C–C–C–C–C–C–C–C ≡ C–H
I I I I II II
H H H H HH HH

12.4 IUPAC System

The full form of IUPAC is International Union of Pure and Applied Chemistry. This system has
been introduced by scientists to bring uniformity in naming organic and inorganic compounds.
In this system, one compound has only one name to avoid errors in understanding a particular
compound.

The process of naming hydrocarbons in the IUPAC system is given below:

(i) The number of carbon atoms in a hydrocarbon is indicated by using the given stems:

One carbon atom is indicated by writing 'Meth', two carbon atoms by 'Eth', three by
'Prop', four by 'But', five by 'Pent', six by 'Hex', seven by 'Hept', eight by 'Oct', nine by
'Non' and ten carbon atoms are indicated by writing 'Dec'.

(ii) A saturated hydrocarbon containing single bond between carbon atoms is indicated by
writing '-ane' after the stem.

(iii) An unsaturated hydrocarbon containing a double covalent bond is indicated by writing
'-ene' after the stem.

(iv) An unsaturated hydrocarbon containing a triple covalent bond is indicated by writing
'-yne' after the stem.

For example
HH H
II I

H–C–C–C–H
I II

H HH

No. of carbon atoms = 3

∴ Stem = Prop

Type of bond = single covalent = ane

∴ The name of the given hydrocarbon = Prop + ane = propane
HH
II

H–C=C–C–C–H
IIII

HHHH
No. of carbon atoms = 4
∴ Stem = But

Type of bond = Double covalent = ene

∴ The name of the given hydrocarbon = But + ene = Butene

210 Oasis School Science - 10 CHEMISTRY

12.5 Functional Group

A functional group is an atom or group of atoms that determine the chemical properties of
a hydrocarbon. For example, hydroxyl (– OH), ether ( – O –), aldehyde (– CHO), etc. Some
functional groups with their symbol, structure and compounds are given below:

S.N. Name of functional Symbol Structure Organic compounds
group

1. Hydroxyl –OH – OH Alcohol

2. Carboxylic acid –COOH O Acid
II
– C – OH

3. Ether –O– –O– Ether

4. Aldehyde –CHO O Aldehyde
II

–C–H

5. Keto –CO– O Ketone
II

–C–

6. Amino –NH2 H Amine
I

–N–H

12.6 Alkyl Radical

The group of atoms formed by removing one hydrogen from an alkane is called alkyl radical.
Its general formula is CnH2n+1. For example, methyl (CH3+) radical is formed by removing one
hydrogen atom from methane (CH4). Similarly, ethyl (C2H5+) radical is formed by removing
one hydrogen atom from ethane (C2H6), etc.

12.7 Homologous Series

A homologous series is a group of organic compounds having similar structures and chemical
properties in which the successive compounds differ by -CH2 group. All the members of a
homologous series can be represented by the same general formula, and they can be prepared
by similar methods. For example,

CHEMISTRY Oasis School Science - 10 211

The first five members of the homologous series of alkanes are given below:

Common name Molecular Structural formula Condensed formula
1. Methane CH4
formula (CnH2n+2) H
CH4 I CH3CH3
H–C–H
2. Ethane C2H6 I
H

HH
II
H–C–C–H
II
HH

3. Propane C3H8 HHH CH3CH2CH3
III
H–C–C–C–H
III
HHH

4. Butane C4H10 HHH H CH3CH2CH2CH3
III I
H–C–C–C–C–H
II I I
HH H H

5. Pentane C5H12 HHH H H CH3CH2CH2CH2CH3
III I I
H–C–C–C–C–C–H
II I I I
HH H H H

12.8 Some Important Organic Compounds and Their Uses
a) Methane (CH4)

Methane is the first member of hydrocarbons. It is the simplest aliphatic hydrocarbon.
It occurs in gaseous state at room temperature. Methane is also called marsh gas be-
cause it is formed by the decomposition of organic matter within water in marshy places.
Methane is found in natural gas, petroleum, coal mines and biogas.

212 Oasis School Science - 10 CHEMISTRY

H Methane Fact File - 1
I
H–C–H • Methane is also called marsh gas
I as it is found in marshy places.
H

Methane

Uses of methane
1. It is used as a fuel in the form of LNG (liquified natural gas).
2. It is used in the manufacture of hydrogen (H2), chloroform (CHCl3), formaldehyde
(HCHO), carbon tetrachloride (CCl4), methyl alcohol (CH3OH), etc.
3. It is used to make carbon black which is used in rubber industries.
4. It is used to make printing ink and paints.

b. Ethane (C2H6)

Ethane is the second member of alkane series. It is a saturated hydrocarbon. It occurs in
natural gas and petroleum mines.

HH Ethane
II
H–C–C–H
II
HH

Ethane

Uses of ethane
1. It is used as a source of heat for cooking purpose in the form of biogas.
2. It is used for making shoe polish, printers' ink, ethanol, diethyl ether, etc.

c. Propane (C3H8)

Propane is the third member of alkane series. It is a saturated hydrocarbon which occurs
in natural gas and petroleum mines. Propane is a highly inflammable gas.

HH H Propane Fact File - 2
II I
H–C–C–C–H Propane (C3H8) is highly
II I inflammable. So, it is used as a
HH H fuel in lighters.

Propane

inflammable /ɪnˈflaməb(ə)l/ - flammable

CHEMISTRY Oasis School Science - 10 213

Uses of propane
1. It is used as a fuel in lighters.
2. It is used in petroleum industries for cooling purpose.

d. Butane (C4H10)
Butane is the fourth member of alkane series. It is a saturated hydrocarbon which occurs

in petroleum mines.

HH H H
II I I
H–C–C–C–C–H
II I I
HH H H

Butane Butane

Uses of butane

1. Butane gas is used as a source of heat in the form of LP gas as this gas liquefies easily
under pressure.

2. It is used in rubber industries as a raw material.

12.9 Isomers and Isomerism

Isomers are organic compounds having the same molecular formula but different structure
and properties. Isomerism is the existence of two or more different organic compounds having
the same molecular formula but different structures and properties. Isomerism is possible
only with hydrocarbons having four or more carbon atoms. For example, n-Butane and iso-
butane are two isomers of butane.

Name Molecular Structural formula Condensed formula
i) n - Butane formula
HH H H CH3–CH2–CH2–CH3
C4H10 II I I
H–C–C–C–C–H CHI 3
II I I CH3 – CH – CH3
HH H H

ii) iso-Butane C4H10 H
I
H–C–H
H H
I I I

H–C–C–C–H
I II
H HH

isomerism /ˈaisəmərizəm/ - the existence of two or more isomers of a compound
214 Oasis School Science - 10 CHEMISTRY

12.10 Alcohol

Alcohol is an organic compound which contains hydroxyl group (OH). Alcohols are
derivatives of alkanes because they are formed by substitution of hydrogen atom of an alkane
by hydroxyl group.

For example,

H –H H
I +OH I
H–C–H H – C – OH
I I
H H

Methyl alcohol or methanol

Types of Alcohol

Depending on the number of hydroxyl groups, there are different types of alcohol. But in this
unit, we study three types of alcohol:

a. Monohydric alcohol Reasonable Fact-1

Alcohol having only one hydroxyl group (-OH) Why is methyl alcohol called
monohydric alcohol?
is called monohydric alcohol. It is formed by the
replacement of one hydrogen atom of an alkane Ans: Methyl alchol consists of only one
by one hydroxyl group. hydroxyl group (-OH). So, it is called

For example, Methyl alcohol monohydric alcohol

H –H H
I +OH I
H–C–H H – C – OH
I I
H H

(Methane) (Methyl alcohol or methanol)

HH –H HH
II +OH II
H–C–C–H H – C – C – OH
II II
HH HH

(Ethane) (Ethyl alcohol or ethanol)
b. Dihydric alcohol

Alcohol having two hydroxyl groups (–OH) in one compound is called dihydric alcohol.
It is formed by the replacement of two hydrogen atoms from two carbons of ethane by
two hydroxyl groups. For example, Ethyl glycol

HH –2H HH
II +2OH II
H–C–C–H H–C–C–H
II II
HH OH OH

(Ethane) (Ethylene glycol)

CHEMISTRY Oasis School Science - 10 215

c. Trihydric alcohol

Alcohol having three hydroxyl groups in one Reasonable Fact-2
compound is called trihydric alcohol. It is formed by
the replacement of three hydrogen atoms from three Why is glycerol called trihydric
carbons of propane by three hydroxyl groups. For alcohol?
example, Glycerol
Ans: Glycerol consists of three
hydroxyl (OH) groups. So, it is

HHH –3H called a trihydric alcohol
III +3OH
HH H
H–C–C–C–H II I
I II H–C–C–C–H
H HH I II
OH OH OH

(Propane) (Glycerol)

12.11 Some Important Alcohols

a. Methyl alcohol or Methanol (CH3– OH)
It is the first member of monohydric alcohol which is formed by the replacement of one

hydrogen from methane by one hydroxyl group.

H H –H H
I I +OH I
H – C – OH H–C–H H – C – OH
I I I
H H H

(Methanol) (Methane) (Methanol)

Uses of methyl alcohol Fact File - 3

1. Methyl alcohol is used as fuel because it Ethyl alcohol, or ethanol, is used
produces a large amount of heat without in alcoholic drinks.
smoke. So, it is used in a spirit lamp.

2. It is used to manufacture perfumes, dyes,
paints, synthetic fibre, etc.

3. It is used to dissolve fats, oil, paints, varnish, etc.

4. It is used to make different types of compounds like methyl chloride,
formaldehyde, etc.

b. Ethyl alcohol or Ethanol (C2H5OH)
It is the second member of monohydric alcohol which is formed by the replacement of

one hydrogen from ethane by one hydroxyl group. It is commonly known as alcohol.

HH HH HH
II II II
H – C – C – OH H – C – C – H –H H – C – C – OH
II I I +OH I I
HH HH HH

(Ethanol) (Ethane) (Ethanol)

216 Oasis School Science - 10 CHEMISTRY

Uses of ethyl alcohol

1. Ethyl alcohol is used in alcoholic beverages for drinking purpose.

2. It is used in thermometer as a thermometric liquid.

3. It is used as a fuel.

4. It is used to make medicines, paint, soap, varnish, synthetic rubber, etc.

5. It is used to dissolve fat, oil, paints, resin, etc.
6. It is used in hospitals to clean wounds and utensils.

7. It is used as laboratory reagent to make various compounds, like ether, chloroform,
iodoform, etc.

c. Glycerol (Trihydric alcohol)

The word glycerol is derived from "glyceros" which means sweet. It is formed by the

replacement of three hydrogen atoms from three carbons of propane by three hydroxyl

groups. Glycerol is a colorless liquid a having a sweet taste. It dissolves in water but not in
ether.

C3H5(OH)3 HHH CH2OH – CHOH – CH2OH
III
(Molecular formula) H–C–C–C–H (Condensed formula)
I II
OH OH OH

(Structural formula)

Fig. Glycerol

HHH –3H HH H
III +3OH II I
H–C–C–C–H H–C–C–C–H
III III
HHH OH OH OH

(Propane) (Glycerol)

Fact File - 4

• The word glycerol has been derived from the Greek word glyceros which means
'sweet' in taste.

• The IUPAC name of glycerol is propane 1, 2, 3 triol.

Uses of glycerol
1. Glycerol is used as a sweetening agent in confectionery, beverages and medicines.
2. It is used in the manufacture of soaps and cosmetics of good quality.
3. It is used for the preservation of fruits and tobacco.
4. It is used in the preparation of printing inks and stamp pad inks.
5. It is used in lip guards, face creams, etc. to protect the skin from being dry.

varnish /ˈvɑːnɪʃ/ - a liquid that is painted onto wood, metal, etc.

CHEMISTRY Oasis School Science - 10 217

12.12 Ether

An organic compound which has oxygen in between two alkyl groups is called ether. Its
condensed formula is R–O–R (where R=alkyl group). Diethyl ether is commonly known as
ether. It is a colorless volatile liquid. It is insoluble in water but soluble in alcohol. Ether is
extracted from alcohol by removing water with the help of conc. sulphuric acid.

Examples of ether

Dimethyl ether (or methoxy methane)

CH3– O – CH3 Or HH
II
H–C–O–C–H
II
HH

(Dimethyl ether
or

(Methoxy methane)

Diethyl ether or ethoxy ethane (C2H5–O–C2H5)

CH3– CH2 – O – CH2 – CH3 Or HH HH
II II
H–C–C–O–C–C–H

II II
HH HH

(Diethyl ether)
Uses of ether Or

(Ethoxy ethane)

1. It is used as a local anaesthetic agent during minor surgery.

2. It is used as an organic solvent.

3. It is used for the purification of organic compounds.

4. It is used as a refrigerant for cooling purpose.

12.13 Glucose

The word glucose has been derived from the Greek word glukus which means sweet in taste.
Glucose is a crystalline white powder which dissolves easily in water. It is a carbohydrate and
monosachharide sugar. Its chemical formula is C6H12O6. It helps our body to produce ATP. Our
body utilizes ATP to release energy. Glucose is also called dextrose.

Glucose is found in fruits and honey. It helps to transport free sugar in the blood as a source
of energy to perform various activities inside the cell of living beings, and it has a great role in
metabolism. Glucose is both useful and harmful for living beings.

High blood sugar causes swelling of different body parts. Similarly, low blood sugar is also
harmful for our body. Both conditions are harmful for human beings.

volatile /ˈvɒlətaɪl/ - that changes easily into a gas

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SUMMARY

• Compounds which are formed by the combination of carbon and hydrogen
are called hydrocarbons.

• Hydrocarbons in which carbon atoms are connected by a single covalent
bond are called saturated hydrocarbons.

• Hydrocarbons in which carbon atoms are connected by a multiple (either
double or triple) covalent bond are called unsaturated hydrocarbons.

• Unsaturated hydrocarbons in which any two carbon atoms are connected by
a double covalent bond are called alkenes.

• Unsaturated hydrocarbons in which any two carbon atoms are connected by
a triple covalent bond are called alkynes.

• A functional group is an atom or group of atoms that determine the chemical
properties of a hydrocarbon.

• Homologous series is the group of organic compounds having similar
structures and chemical properties in which the successive compounds differ
by – CH2 group.

• Isomers are organic compounds having the same molecular formula but a
different structure and properties.

• Alcohol having only one hydroxyl group (-OH) is called monohydric
alcohol.

• Glycerol is a colorless liquid having a sweet taste.
• An organic compound having oxygen in between two alkyl groups is called

ether.
• Glucose is a white crystalline powder that dissolves in water. Its chemical

formula is C6H12O6. It is found in fruits and honey.

CHEMISTRY Oasis School Science - 10 219

Exercise

Group-A
1. What is a hydrocarbon?
2. Give any two examples of hydrocarbons.
3. How many types of hydrocarbon are there? Name them.
4. What is the full form of IUPAC?
5. What is methane? Where is it found?
6. Where is propane gas found in nature?
7. What are isomers?
8. What is glycerol?
9. Write down two properties of glycerol.
10. What is glucose?
11. Write the molecular formula of glucose.
12. Where is glucose found?
13. What type of hydrocarbons are called paraffins?
14. Which alcohol is used to manufacture formaldehyde? Write its name.
15. Write full form of L.P.G.
16. Draw structural formula of ethyl alcohol.
17. What is homologous series?
18. Write down the structural formula of butane.
19. Give the structural formula of ethyl alcohol.

Group-B
1. What is isomerism? Write with an example.
2. Write any two differences between saturated hydrocarbon and unsaturated hydrocarbon.
3. Write any two differences between propane and propene.
4. Write any two differences between methane and ethane.
5. Write any two differences between ethyne glycol and glycerol.
6. Write any two differences between alcohol and glycerol.
7. Butane is called a saturated hydrocarbon, why?
8. Methane is called a hydrocarbon, why?
9. Propene is called an unsaturated hydrocarbon, why?

220 Oasis School Science - 10 CHEMISTRY

10. Glusose is both useful as well as harmful for animals. Justify this statement.

11. What happens when the amount of glucose becomes more or less than the required
amount?

12. Acetylene is an unsaturated hydrocarbon. Write down its cause on the basis of its
structural formula.

Group-C
1. Write any three uses of methane gas.

2. Write down the structural formula and one use of ethane.

3. Write any three uses of each methyl alcohol and ethyl alcohol.

4. Identify the given compounds and write any one use of each:

HH CHI 3 OH OH
II iii) CH3 – CH – CH3 II
i) H – C – H ii) H – C – OH iv) H – C – C – H
I I II
H H HH

5. Write any three uses of glycerol.

6. Write down the utility of glucose.

7. Write the structural formula of the compound formed by replacing a hydrogen atom
with OH group from ethane.

8. State the name and three uses of the compound whose structural formula is given below:
HH
II

H – C – C – OH
II
HH

9. Write any three uses of methane gas.

Group-D
1. Mention the method of naming hydrocarbons.

2. What are the compounds having the following structural formula? Write the types of
hydrocarbon on the basis of bond.

HH HH H
II II I
i) H – C = C – C ii) H – C – C – C – OH
III
HHH

CHEMISTRY Oasis School Science - 10 221

3. Write the name of compound and its structural formula which is formed by displacement
of three hydrogen atom with three hydroxide radical from propane through various
chemical reactions.

4. What are the compounds of the following structural formula? Write the type of

hydrocarbon on the basis of the bond.

HH H
II I
a) H – C – C – C – H b) H – C = C – H
III
HHH

5. A certain hydrocarbon has a structural formula as shown:

HH H
II I
H–C–C=C–H
I
H

i) Is this a saturated hydrocarbon or unsaturated hydrocarbon?

ii) If the above mentioned hydrocarbon is made to react with plenty of hydrogen a
new hydrocarbon will be formed. Name and draw the structural formula of the
hydrocarbon formed in this way.

6. Write the name and structural formula of the compound which is formed by connecting
ethane by hydroxyl radical. Give one example of trihydric alcohol and also mention its
structural formula.

7. Give the structural formula of Glycol and write with reason if it is saturated or not. Write
down the structural formula of the alkyne having four carbons. Name the hydrocarbon
formed by reacting above hydrocarbon with sufficient hydrogen. Also, Write one use of
the newly formed hydrocarbon.

222 Oasis School Science - 10 CHEMISTRY

UNIT13 Estimated teaching periods

Theory 10

Practical 0

MATERIALS USED
IN DAILY LIFE

Objectives

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

• define cement, glass, fibers, ceramics, soaps, detergents, fertilizers and insecticides.
• explain the manufacturing methods and uses of the above chemicals in our daily life.
• explain the importance of nutrients, i.e. nitrogen, phosphorus and potassium in

growing plants.
• introduce different types of fertilizers.
• explain chemical pollution, its effects and control measures.

13.1 Introduction

In our surroundings, there are various types of chemical substances, which may be natural
or man-made. These substances are used by human beings to fulfill their basic needs of food,
shelter, clothing and health. In ancient times, only natural substances were there, and men
used these substances to meet their requirements. But nowadays with the development of
science and human knowledge, a large number of chemical substances like cement, glass,
soaps, plastics, detergents, medicines, fertilizers, pesticides, dyes, fibers, etc. have been
produced. By the use of those natural as well as man-made chemical substances, our lives
have become easier, more comfortable and luxurious.

13.2 Cement

Cement is a fine gray powder of calcium silicate and calcium aluminate, which becomes hard
when mixed with water and dried for some time. It is an important material for the construction
of buildings, bridges, roads, dams, walls, etc.

Manufacture of cement

1. Raw materials of cement

The raw materials that are used for manufacturing the cement
are as follows:

(i) Limestone CaCO3 (2/3 part) Fig. 13.1 Cement
(ii) Special type of clay Al2O3 . SiO2 (1/3 part)
(iii) Gypsum
CaSO4 . 2H2O (Only about 2 – 3%)

CHEMISTRY Oasis School Science - 10 223

Reasonable Fact-1

Why is gypsum added to cement? Give reason.
Ans: Gypsum is added to cement to slow down the initial setting of cement when water is
added. The slow setting of cement helps us in two ways:
(i) It is easier to work with slow setting cement. (ii) Such cement leads to its greater hardening.

Reasonable Fact-2

Cement sets hard when mixed with water.

Ans: Cement sets hard when mixed with water due to hydration, i.e. a chemical reaction in
which the compounds in cement form chemical bonds with water molecules and become
hydrates or hydration products.

2. Formation of cement slurry: The raw materials of cement are crushed separately and
ground to make a fine powder. The powdered limestone and clay are mixed in the ratio
of 2:1 along with water to make a paste called cement slurry.

3. Formation of cement clinker: The cement slurry is passed through a tall rotary kiln. It
has a temperature of about 1400°C to 1600°C and a height of about 150 m. At this high
temperature, limestone and clay react together. As a result, cement is produced in the
form of small pea-sized and red colored balls called cement clinkers.

4. Formation of cement powder: To improve the quality of cement and setting time, 2–3%
of gypsum (CaSO4. 2H2O) and some iron oxides are mixed with the cement clinker. Then
it is passed into a grinder to obtain cement. It is necessary to keep the cement in a dry
place to protect it.

Uses of cement

1. To make cement mortar: The mixture of cement, sand and water is known as
cement mortar. It is used for plastering walls, joining bricks, stones, etc.

2. To make cement concrete: The mixture of cement, sand, water and gravel is known
as cement concrete. It is used for roofing, flooring of buildings and making pillars.

3. To make reinforced cement concrete (RCC): The mixture of cement, sand, water
and gravel having an iron framework inside it is called RCC. It is used for making
roofs and pillars of buildings, dams, bridges, tunnels, gutters, etc.

Some cement factories in Nepal

S.N. Name of Cement Factories Location
1. Udayapur Cement Factory Jaljale, Udayapur
2. Hetauda Cement Factory Hetauda, Makawanpur
3. Triveni Cement Factory Bharatpur, Chitwan
4. Bishwakarma Cement Factory Mukundapur, Nawalparasi

slurry /ˈslʌri/ - a thick liquid consisting of water mixed with cement

224 Oasis School Science - 10 CHEMISTRY

5. Ambe Cement Pvt. Ltd. Birgunj, Parsa

6. Nepal Ambuja Cement Udhyog Pvt. Ltd. Kamhariya, Rupandehi

7. Nepal Shalimar Cement Pvt. Ltd. Simara, Bara

8. Jagadamba Cement Industries Pvt. Ltd. Gonaha, Bhairahawa

9. KEPY Cement Industries Ltd. Naubise, Dhading

10. Brij Cement Pvt. Ltd. Bhairahawa, Rupandehi

13.3 Glass

Glass is a metallic silicate of various metals. It is a hard, transparent, amorphous and
supercooled liquid. It is an important industrial material which is used in our daily life. We
use glass for making windowpanes of houses, cars, buses, etc. It is also used for making
laboratory equipment, lenses, mirrors, etc. Glass is prepared by heating a mixture of silica,
sodium carbonate and calcium carbonate in a furnace.

Characteristics of glass

1. Glass is a hard, transparent Fact File - 1
homogeneous mixture of various
In fact, glass is not a solid but a
metallic silicates.

2. It does not have a fixed composition supercooled liquid because molecules
and particular formula. of glass flow very slowly like the
molecules of a liquid.

3. It does not have a fixed melting point.

4. The properties of glass depend on the chemicals added during its manufacture.

Types of glass

Depending on the composition, glass is of the following types:

1. Quartz glass

It is a pure crystalline glass which is prepared by heating silica at about 16000C and then
cooling the product. It is also called silica glass.

Pure silica (SiO2) 1600 0C Quartz glass

Characteristics
Quartz glass is very strong. It is insoluble in water and most of the acids. It is not affected

by chemical reagents and has very low coefficient of thermal expansion. So, when red
hot quartz glass is kept in cold water, it does not crack.

Uses

It is used for making electrical devices, laboratory appliances like crucibles, basins, etc.
and colorful gems.

2. Water glass

Sodium silicate, or potassium silicate, is called water glass. It is prepared by heating
silica with sodium carbonate or potassium carbonate at about 800°C and cooling the

CHEMISTRY Oasis School Science - 10 225

product. It is easily soluble in water. So, it is called water glass.

SiO2 + Na2CO3 800 0C Na2 SiO3 + CO2↑

(Sodium silicate)

SiO2 + K2CO3 800 0C K2 SiO3 + CO2↑

(Potassium silicate)

Characteristics

Water glass dissolves in water. This glass is fireproof.

Uses Fig. 13.2 Silica garden
Water glass is used for making fireproof materials, silica

garden, gums, glue and paste.

3. Ordinary glass or soda-lime glass

The homogeneous mixture of sodium silicate and calcium silicate is called ordinary

glass. It is also called soft glass as it melts at low temperature. This glass is prepared

by heating a mixture of 50% silica, 25% pieces of glass, 15% sodium carbonate and 10%

calcium carbonate at about 1500°C in a tank furnace. In ordinary glass, limestone helps

to make the solution insoluble and glass pieces help in melting.

2 SiO2 + Na2CO3 + CaCO3 1500 0C Na2SiO3.CaSiO3 + 2CO2

(Sodium silicate and calcium silicate)

When lead monoxide is added during the manufacture of ordinary glass, it becomes lead
silicate glass. Lead monoxide increases the refractive index of glass and decreases the
transparency. So, it is used for making lenses, prisms, etc.

Characteristics

Ordinary glass melts at low temperature, and it is insoluble in water.

Uses

Ordinary glass is used in the manufacture of simple bottles, windowpanes, glass sheets,
laboratory apparatus, etc.

4. Hard glass

The homogeneous mixture of potassium silicate and calcium silicate is called hard glass.
This glass is obtained by heating a mixture of silica, potassium carbonate and calcium
carbonate at a high temperature. It is also called potash lime glass.

2 SiO2 + K2CO3 + CaCO3 ∆ K2 SiO3.CaSiO3 + 2CO2

(Potassium silicate and calcium silicate)

Characteristics

It is hard and does not melt at ordinary temperature.

Uses

Hard glass is used for making laboratory apparatus like beakers, hard glass test tube,
electric bulb, tube light, etc.

226 Oasis School Science - 10 CHEMISTRY

5. Borosilicate glass or pyrex glass

The homogeneous mixture of sodium silicate, calcium silicate and boron silicate is called

Borosilicate glass or Pyrex glass. This glass is obtained by heating a mixture of silica,

sodium carbonate, calcium carbonate and boric oxide at a high temperature. The effect

of change in temperature is less in Borosilicate glass due to the presence of boron silicate.
∆
5 SiO2 + Na2CO3 + CaCO3 + B2O3 Na2SiO3.CaSiO3.B2(SiO3)3 + 2CO2

(Sodium silicate, calcium silicate

and boron silicate)

Characteristics

This glass is hard and does not melt at ordinary temperature. It is stronger than ordinary
glass. It is more resistant to heat and chemicals.

Uses

Borosilicate glass is used for making laboratory apparatus like test tubes, flasks, beakers,
ovenwares, ampoules and other pharmaceutical containers.

6. Lead crystal glass

The homogeneous mixture of potassium silicate and lead silicate is called lead crystal
glass. This glass is also called flute glass or optical glass. This glass is prepared by heating
a mixture of silica, potassium carbonate and lead monoxide at a high temperature.

2 SiO2 + K2CO3 + PbO ∆ K2 SiO3. Pb SiO3 + CO2

(Potassium silicate and lead silicate)

Characteristics

Lead crystal glass has a high refractive index due to the presence of lead silicate.

Uses

Lead crystal glass has a high refractive index. So, this glass is used for making lenses,
prisms, electric bulbs, TV screens, spectacles, expensive drinking glasses, radar tubes,
etc. It is also used to cut off UV–radiation. 


7. Colored glasses

Simple or ordinary glasses can be made colorful by adding certain metal oxides to the
molten mass during the preparation of glass.

Certain metal oxides impart a particular color to the glass. So, the selection of the metal
oxide depends on the color of our choice. Some of the metal oxides and the color imparted
by them are given below:



S.N. Metallic oxide Colour imparted to the glass

1. Cobalt oxide Blue
2. Nickel oxide Black
3. Chromium oxide Green

CHEMISTRY Oasis School Science - 10 227

4. Manganese oxide Purple
5. Copper oxide Red
6. Ferric oxide Yellow / Brown
7. Tin oxide Milky white

Reasonable Fact-3

Why is boric oxide added while prepa;ring ordinary glass?
Ans: Boric oxide is added while preparing ordinary glass to reduce the effect of
increase and decrease in temperature.

Reasonable Fact-4

Why is lead crystal glass used for making expensive glassware?
Ans: Lead crystal glass shows an extraordinary sparkle as it has a high refractive
index. So it is used for making expensive glassware (like decoration pieces).

Uses
Colored glasses are used for making sunglasses, disco light signals, artificial gems, etc.

Differences between Soft glass and Hard glass

S.N. Soft glass S.N. Hard glass
1.
The homogeneous mixture of 1. The homogeneous mixture of
sodium silicate and calcium potassium silicate and calcium silicate
silicate is called soft glass. is called hard glass.

2. It has less thermal resistance. 2. It has high thermal resistance.

3. It is used for making window 3. It is used for making heat resistant
panes, mirrors, etc. equipment.

13.4 Ceramics Fig. 13.3 Ceramic utensils

"Ceramics" is derived from the Greek word 'Keramos'
which means potter's clay. Ceramics is a type of clay
which contains the compounds of carbon, hydrogen,
nitrogen, oxygen and silica. It is used to make cups,
plates, dishes, etc. The clay mainly contains hydrated
alumina silica (Al2O3.SiO2.2H2O). This may also
contain other substances like limestone, magnesium
carbonate, oxides of manganese and iron. The pure
white clay is called kaolin, or China clay. It is used
for making cups, plates, dishes, etc.

furnace /ˈf¨ːnɪs/ - a large substance like an oven

228 Oasis School Science - 10 CHEMISTRY

Steps for making ceramic products

In order to make ceramic materials, the clay is crushed, ground and sieved to obtain fine clay.
The clay is mixed with water to make a paste and then cast into different shapes. The objects
of various shapes are allowed to dry in sunlight for several days. After drying, the products
are heated in a furnace. At high temperature, the soil hardens due to chemical reaction and
becomes porous. A little amount of salt is added to make the objects shiny. Some objects of
ceramics are coated with oxides of tin or lead and are heated again. The coat of tin oxide
or lead oxide melts and forms a thin layer over their surface. This process is called glazing.
Glazing makes the articles smooth, attractive and waterproof. Color and polish are also added
in order to make the ceramic items more attractive.

Characteristics of ceramics
1. Ceramics is a poor conductor of heat and electricity.
2. It can withstand high temperature.
3. It is resistant to the action of chemicals.

4. It is hard and brittle.

Uses of ceramics
1. Ceramics is used in making crockery, like cups, bowls, plates, dishes, etc.

2. Being a poor conductor of electricity, it is used in electrical appliances.

3. It is used in household pottery.

4. Glazed ceramics is used to make bathroom tiles, roof tiles, bricks, sinks, commodes, etc.

13.5 Soap and Detergent

Soap and detergent are man-made cleansing agents which are used in our daily life for bathing
and washing clothes, cleaning dishes, etc.

Soap

Soap is a cleansing agent prepared by heating fat or oil with sodium hydroxide. It is used
to clean our body, clothes, utensils and several other household objects. Chemically soap is a
sodium salt of higher fatty acid that has cleansing property in water. For example, sodium sterarate
(C17 H35 COONa), sodium palmitate (C15H31 COO Na), sodium oleate (C17 H33 COO Na), etc.

Simple soap is prepared by heating vegetable oil of olive, coconut, cotton seeds with sodium
hydroxide (NaOH). Similarly, quality soap is prepared by heating animal fat (mutton) with
sodium hydroxide or potassium hydroxide. The process by which soap is prepared is called
saponification. During saponification, sodium chloride is added in the solution to bring the
soap in precipitation because sodium chloride increases the ionic product and decreases the
solubility product. Soap having less density floats on the surface of the solution. Now it is
collected and kept into moulds to get the soap cakes. Sodium carbonate or starch is added to
make the soap hard. Different types of perfumes, colors, antiseptics and bleaching materials
are also added in the soap.

antiseptic /æntɪˈseptɪk/ - a substance that helps to prevent infection in wounds by killing bacteria

CHEMISTRY Oasis School Science - 10 229

C1 7H 35 COO – CI H2 ∆ 3(CS o17dH iu3m 5 CsteOaOratNe)a + CH2 – OH
C17H35 COO – CH + 3NaOH CH – OH

I
C17H35 COO – CH2

(Glyceryl stearate) CH2 – OH

[From animal fat] (Glycerol)

Detergents

Detergents are synthetic petrochemicals obtained from hydrocarbons which are more
soluble than soap. For example: Sodium lauryl sulphate, alkyl benzene sulphonate, sodium
pyrophosphate, etc.

A detergents are sodium salts of long chain benzene sulphonic acid, which are mostly non-
biodegradable with more cleansing property. A detergent is one of the cheap and popular
cleansing agents made from hydrocarbons of petroleum by-products.

Detergent is also called soapless soap because it has cleansing property like a soap but does not
contain the chemicals that are found in the soap. Owing to the following reasons detergents
are better than soap.

1. Synthetic detergents have a stronger cleansing action than that of soap.

2. They can be used even with hard water but soap is insoluble in it.

3. Synthetic detergents are prepared from the hydrocarbons as petroleum by-products. So,
they are cheaper than soap.

4. Hard water having large amounts of calcium and magnesium ions gives insoluble
precipitate, i.e., scum with soap but not with detergent.

Detergent powders or washing powders are synthetic powders which contain synthetic
detergents (15 – 30%), sodium carbonate, sodium silicate, sodium sulphate and a little
amount of bleaching agents like sodium perborate. To make more popular and attractive,
perfumes are also added in those powders.

Differences between Soaps and Detergents

S.N. Soaps S.N. Detergents

1. Soaps are sodium salts of higher 1. Detergents are sodium salts of long

fatty acids, e.g., sodium palmitate. chain benzene sulphonic acid, e.g.,

sodium pyrophosphate .

2. Soaps are insoluble in hard water. 2. Detergents are soluble in hard water.

So, they have less cleansing action. So, they have more cleansing action.

3. They are mostly biodegradable. 3. They are mostly non-biodegradable.

So, they do not cause water So, they cause water pollution.

pollution.

4. They are prepared from the fat of 4. They are prepared from petroleum

animals or plants. by-products.

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13.6 Monomer and Polymer

A polymer is a very large and complex molecule formed by the combination of many simple
and small molecules called monomers. A simple organic compound which can combine in a
large number to form a polymer is called monomer. The process by which a large number of
simple monomers are combined together to give a polymer is called polymerization. Ethene,
vinyl chloride, ethyne, glucose, amino acid, etc. are some examples of monomers whereas
polythene, polyvinyl chloride, cellulose, protein, etc. are some examples of polymers.

Monomer, polymer and polymerization can be illustrated by the given example of PVC.

n[CH2 = CHCl] Polymerization [– CH – CH2 – CH – CH2—]n
II

Cl Cl

Vinyl chloride Polyvinyl chloride (PVC)
(Monomer) (Polymer)

On the basis of the mode of formation, there are two types of polymers. They are:
1. Natural polymer: They are found in nature, e.g., wool, silk, protein, cellulose

natural rubber, starch, etc.
2. Synthetic or man-made polymer: They are made by man, e.g., polythene,

polystyrene, nylon, PVC, artificial rubber, etc.

13.7 Plastics

Plastics are the artificial materials made by the polymerization of carbon containing monomers
like ethene, vinyl chloride, etc. They are cheap, light and available in different shapes, sizes
and colors. They are solid at room temperature but most of them become liquid or semi-
solid on heating. Hence, they can be recycled and remoulded into any desired shape. Most
of the plastics are made from polymeric synthetic resins, whereas a few are based on natural
substances, such as cellulose derivatives. The monomers needed for producing maximum
amounts of plastics are extracted from petroleum substances.

Plastic materials are widely used in our daily life because of the following properties of plastics:
1. They are light and can be moulded into any desired shape.
2. They are cheap, durable and long lasting.
3. They are resistant to acids, alkalis and other chemicals.
4. They are a bad conductor of heat and electricity.
5. It can be colored easily and made transparent.

6. They do not rot and corrode.

Classification of plastics
Plastics are mainly of two types.

a) Thermoplastic
b) Thermosetting plastic

flexible /ˈfleksəbl/ - something which can be bent without breaking
corrode /kəˈrəʊd/ - to destroy something slowly by chemical action

CHEMISTRY Oasis School Science - 10 231

a) Thermoplastic

Plastics which melt on heating and become solid on cooling are called thermoplastics.

Thermoplastics are usually elastic and soft. They become liquid or semi-solid on heating.
So, we can give different shapes and sizes according to the requirement. They are used for
making buckets, pipes, bags, ropes, etc. The main types of thermoplastics are polythene,
polyvinyl chloride (PVC) and polystyrene. Thermoplastics can be remoulded again and
again by heating. Some thermoplastics with their characteristics and uses are given below:

i) Polythene (Polyethylene)

A thermoplastic which is formed by the polymerization of
many ethylene molecules is called polythene. This type of
plastic is very cheap.

n(CH2 = CH2) Polymerization (– CH2 – CH2 – )n

Ethylene (ethene) Polyethylene (Polythene)

Characteristics Fig. 13.4 Polythene
1. It is tough, strong but flexible.
2. It is a bad conductor of heat and electricity.
3. It is resistant to various chemicals.

Uses
1. Polythene is used for making bottles, buckets, pipes, toys, packing materials, etc.

2. It is used for insulating electric wires.

ii) Polyvinyl chloride (PVC)

A thermoplastic which is formed by the polymerization of many vinyl chloride

(CH2 = CHCl) molecules is called polyvinyl chloride.
n(CH2 = CHCl2) Po lymerization ( – CH2 – CH – CH2 – CH –)n

II

Cl Cl
(Polyvinyl choride)
Uses

1. PVC is used for insulating electric wires.

2. It is used for making rain coats, curtains, hand bags,
bottles, cover for motor car seats, buckets, covering
for suitcase, gramophone records, etc.

iii) Polysterene

A thermoplastic which is formed by the Fig. 13.5 PVC
polymerization of many styrene molecules is called
polysterene. It is a hard, transparent and light
plastic material.

Uses

1. Polysterene is used for making toys, thermos-flasks, ceiling tiles, pipes,
thermocol, etc.

2. It is used as an insulator.

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b) Thermosetting plastics

Plastics which do not become soft on heating and cannot be remoulded again and again
are called thermosetting plastics. This type of plastics hardens more but does not melt on
heating. So, it is used for making heat resistant and non-conducting materials. For
example, Bakelite, melamine, etc.

i) Bakelite: Thermosetting plastics formed Fig. 13.6 Thermosetting plastic
by the condensation and polymerization of
formaldehyde and carbolic acid (Phenol) are
called Bakelite. It is a blackish brown, hard
and brittle substance.

Bakelite is used for making handles of pressure
cookers, kettles, plugs, buttons, switches and
other electrical fittings.

ii) Melamine: A thermosetting plastic which is used mainly for laminated coatings is
called melamine. It can be coloured easily. It is used to make cups, plates, bowls,
saucers, etc.

Reasonable Fact-5

Why is PVC called a thermoplastic? How does it differ from Bakelite?

Ans: PVC melts on heating. So, it is called a thermoplastic. PVC can be changed into various
shapes by heating, but Bakelite cannot be changed into various shapes by heating because
bakelite does not melt on heating.

Reasonable Fact- 6

Give the reason for using thermosetting plastic to cover the handle of a pressure cooker.
Ans: Thermosetting plastic is a heat resistant and non-conducting material. It does not
change its shape on heating. It hardens more on heating instead of melting. So thermosetting
plastic is used to cover the handle of a pressure cooker.

Differences between Thermoplastics and Thermosetting plastics

S.N. Thermoplastics S.N. Thermosetting plastics

1. They become soft on heating. 1. They do not become soft on heating.

2. They can be changed into desired 2. They cannot be changed into desired
shapes. shapes.

3. They are soft, weak, elastic and 3. They are hard, strong, non-elastic
less brittle. Examples: Polythene, and more brittle. Examples: Bakelite,
polyvinyl chloride (PVC), etc. melamine, etc.

Common uses of plastics
1. Plastics are used as insulators as they are bad conductors of heat and electricity.

CHEMISTRY Oasis School Science - 10 233

2. They are used for making parts of vehicles instead of metals.

3. They are used for making pipes, bags, seat covers, water tanks, water bags, etc.

4. They are used for making surgical instruments, medicine cover, medicine bottle, etc.

5. They are used for making packing materials, kitchenwares, laboratory equipment, etc.

Demerits of plastics

Plastics are commonly used man-made chemical substances. Their excessive use leads to
severe problems. Some of them are :
1. They are non-biodegradable. So, they cause water and soil pollution.
2. Some of them catch fire easily and produce a poisonous fume, which causes air
pollution.

13.8 Fibers

Fibers are thread-like substances which are long, strong and elastic. They are used to make
ropes, clothes, nets, etc. They are polymers consisting of one or more than one type of
monomers. There are two types of fibers:

a) Natural fibers

b) Artificial fibers

a) Natural fibers

Naturally occuring fibers are called natural fibers. Cotton, wool, silk, linen, etc. are some
examples of natural fibers. They are mainly used for making clothes. Natural fibers are
of two types:
i. Plant fibers: Fibers which are obtained from plants are called plant fibers. For
example, cotton, jute, hemp, bombax, etc. Jute fibers are used for making sacks,
bags, ropes, etc. Cotton is used for making clothes as it is soft and absorbs water.

ii. Animal fibers: Fibers which are obtained from animals are called animal fibers.
Wool (which is obtained from sheep, goat, rabbit, etc.) and silk (which is obtained
from silkworms) are important animal fibers. They are used to make different
types of clothes.

Advantages of natural fibers

1. The clothes made by natural fibers like cotton are more comfortable for wearing in
the summer season.

2. They protect our body against cold and keep us warm.
3. Cotton clothes absorb our body sweat.

Disadvantages of natural fibers
1. They do not retain their creases.
2. They are easily attacked by insects.
3. They do not dry easily after washing.

pulp /pʌlp/ - a soft substance that is made by crushing wood

234 Oasis School Science - 10 CHEMISTRY

4. They are short, heavy and less durable.
5. Cotton and woollen clothes wrinkle after washing.
6. They are very expensive for common people.

b) Artificial fibers
Man-made fibers are called artificial fibers. There are two types of artificial fibers. They are:

(i) Recycled fibers (ii) Synthetic fibers
(i) Recycled fibers: Artificial fibers which are made from natural substances are

called recycled fibers. Rayon is one of the best examples of recycled fiber, which
is formed from cellulose, pulp, sodium hydroxide, sulphuric acid and carbon
disulphide. Rayon looks like silk in appearance, so it is also called artificial silk.

Uses of recycled fibers
i. They are used in the manufacture of fabrics, i.e., textiles.
ii. Long rayon filaments are used in the tyre industry to make tyre cords, caps, etc.
iii. Rayon and wool are mixed together for making carpets.
iv. They have less sticking power, so they are used for dressing wounds and to make

bandages.

(ii) Synthetic fibers: Fibers which are made artificially by chemical process are called
synthetic fibers. Examples: Acrylene, nylon, polyster, terylene, olefin, crestan,
orlan, etc.

Nylon: It is a type of synthetic polymer which is formed by repeating the amides
group (–CO–NH–). Hence, it is also called polyamide fiber.

Characteristics of nylon
1. It is a strong and elastic fiber.
2. It does not wrinkle and is not attacked by insects.
3. It absorbs less water and dries up easily.
4. It is light and has low melting point.

Uses of nylon
Nylon is used for making carpets, socks, tyres, dresses, fishing nets, parachute ropes, etc.

Terylene: It is a synthetic fiber which is formed by repeating ester molecules. Polyester,
kodel, fortel, etc. are the examples of terylene fibers. They easily regain their original
shape after getting wrinkled.
Characteristics of a terylene
1. Terylene is a strong, flexible, durable and wrinkle-resitant fiber.
2. It absorbs less amount of water. So, it dries quickly.
3. It is resistant to chemicals and biological agents like moths, moulds, etc.

CHEMISTRY Oasis School Science - 10 235

Uses of terylene
It is used for making textiles, suit, etc. A suits is made when cotton fibers (terycot) and

wool (terywool) are bound together.

13.9 Insecticides

Man-made poisonous chemical compounds that are used to kill or control harmful insects are
called insecticides. In our surroundings, several insects and pests are present. Among them,
some are benificial whereas some are harmful. Some insects harm plants, crops, domestic
animals, human beings, etc. Therefore, poisonous chemicals are manufactured to control
them. Those chemicals either kill or disturb the life cycle of harmful insects and decrease their
number. On the basis of the chemical nature, there are two types of insecticides. They are:
i. Organic insecticides: They are carbon containing man-made chemical compounds

which are used to kill or control harmful insects. These compounds mainly contain
carbon, hydrogen, oxygen and any other important elements like chlorine, phosphorus,
etc. Depending on the elements present, there are three types of organic insecticides.
They are:

(a) Chlorinated organic insecticides: These organic insecticides contain chlorine as
an additional element. They are stable with long and broad effects. Examples:
BHC (Benzene hexachloride), DDT (Dichloro diphenyl trichloro ethane), Aldrin,
Dialdrin, Methoxychlor, etc. Their effect remains for a long time.

(b) Organophosphate insecticides: These organic insecticides contain phosphorus as
an additional element. They are less stable, biodegradable but highly toxic to man
and other animals. Examples: malathion, parathion, phosdrin, etc.

(c) Carbamate insecticides: These organic insecticides contain amino group (–NH2).
They are less harmful. Examples: Begon, Termic, etc.

ii. Inorganic insecticides: Insecticides which are made from minerals are called inorganic
insecticides. In their compounds, they contain other elements except carbon. They are
mainly used to protect vegetables, fruits, cotton and other plants. Examples: calcium
arsenate, lead arsenate, fluoride, lime sulphur, etc.
Characteristics of good insecticides
i. They should be easily bio-degradable.

ii. They should be harmless to human beings, animals, birds, fishes and plants.

iii. They should not leave long term effect.

iv. They should not leave harmful deposits in the food crops, blood, tissue, etc.

v. They should not kill useful insects which help in pollination, dispersal of seeds,
etc.

vi. They should not pollute water, air and soil.

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Advantages of insecticides
i. They are used to kill or control harmful insects.
ii. They kill germs and protect from infection of diseases.
iii. They kill harmful insects that damage crops.

Disadvantages of insecticides
i. Most of the insecticides are non-biodegradable. So, they cause air, soil and water

pollution.
ii. Some insecticides, which are used in fruits and crops, leave harmful deposits in them.
iii. Insecticides kill not only harmful insects but also some useful ones.
iv. Powdered insecticides (like DDT) harm human beings, animals, birds and plants.

Precautions while using insecticides
i. They should be stored away from the reach of children.
ii. The name of insecticides, targeted organisms, quantity, etc. should be labeled

clearly.
iii. During manufacture and use of powdered insecticides, a mask should be used.
iv. Gloves, mask and apron should be used while spraying insecticides and after

spraying or dusting, hands should be washed properly with soap and water.
v. We should use little quantity of insecticides.

Effects of DDT
i. DDT is a very fine powdered insecticide. So, it causes air, water and soil pollution.
ii. Covering of bird's egg (the shell) becomes thin and weak.
iii. DDT when deposited in the lung of animal causes lung diseases.
iv. It is deposited on the surface of leaves, which reduces the rate of photosynthesis

and transpiration.

13.10 Fertilizers

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 purpose of continuous use of soil and to
maintain crop production, it is necessary to use the fertilizers. A good fertilizer, or complete
fertilizer, provides essential elements to the growing plants as well as nourishes the micro-
organisms. On the basis of the chemical nature, there are two types of 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.

CHEMISTRY Oasis School Science - 10 237

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 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, a 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.

ii. Chemical fertilizers: 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 the element present, there are three
types of chemical fertilizers.

a) 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]

Importance of nitrogen (Nitrogenous fertilizer)
It 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 less development of
flowers, fruits and seeds. Leaves become yellow, and flowers do not bloom properly.

b) 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

wither / ˈwɪðə / - to dry up and die
238 Oasis School Science - 10 CHEMISTRY

Importance of phosphorus (Phosphorus fertilizer)

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

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

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

Importance of potassium (Potassium fertilizer)

It 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 fertilizers

S.N. Organic Fertilizers S.N. Chemical Fertilizers

1. They are obtained from dead, 1. They are man-made inorganic
decayed and decomposed parts substances.
of animal and plant or their waste
products.

2. They are not soluble or less soluble 2. They are soluble in water.
in water.

3. They do not supply sufficient 3. They supply sufficient amounts of
amounts of nitrogen, phosphorus nitrogen, phosphorus and potassium to
and potassium to the growing the growing plants.
plants.

4. Plants absorb them very slowly. 4. Plants absorb them very fast.

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

a. Single fertilizers: 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: Fertilizers which supply more than one basic nutrient are called mixed
fertilizers. Examples: Potassium nitrate, ammonium phosphate, etc.

c. Complete fertilizers (NPK fertilizers): 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.

Disadvantages of using fertilizers

We should not use excessive amounts 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 the available oxygen in water and create an
oxygen deficiency in water. So, aquatic animals die due to lack of oxygen. Similarly, when
children drink water containing nitrogen, they become dwarfs.

CHEMISTRY Oasis School Science - 10 239

Precautions while using fertilizers

i. We should not use excessive amounts of fertilizers which may damage the plants.
ii. Nitrogenous fertilizers due to their easy burning nature cause fires when they

come in contact with wooden dust, coal, dry leaves, etc.
iii. Hydroscopic fertilizers like urea should be stored away from moist places.

iv. Chemical fertilizers should be stored away from the reach of children.

v. They should be used after testing the soil.

Reasonable Fact-7

Organic fertilizer is better than chemical fertilizer. Give two reasons.
Ans: Organic fertilizer is better than chemical fertilizers because of the following
reasons:
• Organic fertilizers provide all the necessary elements to the plants, and plant prod-

ucts produced by using organic fertilizer are tasty, nutritious and healthy, but plant
products produced by using chemical fertilizers affect our health.

• Organic fertilizers do not cause chemical pollution, but chemical fertilizers
cause chemical pollution.

13.11 Chemical Pollution

The pollution created by unwanted and excessive use of chemical substances is called chemical
pollution. The different types of useful and useless chemicals which are obtained from organic
and inorganic substances like fertilizers, insecticides, soaps, detergents, plastics, fibers, etc.
are polluting the environment everyday. So, contamination of unwanted chemicals in the
environment is called chemical pollution.

Causes of chemical pollution

Various factors are directly and indirectly involved in chemical pollution. Among them,
some major factors are:

i. The use of insecticides and fertilizers: Chemical fertilizers and insecticides constitute
major chemical pollutants. These chemicals cause water, air and soil pollution. Most of
them are non-biodegradable, so their effect remains for a long time. Insecticides like
DDT cause water, air and soil pollution. Our environment has also been polluted by
toxic insecticides like aldrin, dieldrin and heavy metals like lead, cobalt, mercury, etc.
Nitrogenous fertilizers, when washed by rain water, reach the water body. Due to the
presence of nitrogen element, aquatic plants develop more rapidly and reduce oxygen
concentration of water. Thus, aquatic animals die due to more BOD (Biological Oxygen
Demand) value.

ii. Household wastes and plastics: Different types of solid wastes of food, vegetables,
clothes, ceramics, detergents, soaps, plastics, etc. also cause chemical pollution.
The non-biodegradable nature of some chemicals like plastics, detergents, etc. is creating
a severe problem in the environment. So, it is necessary to recycle plastics in order to
avoid pollution by plastic materials.

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Reasonable Fact-8

Why is plastic considered the major cause of chemical pollution?
Ans: Plastics are considered the major cause of chemical pollution becuase plastics are
non-biodegradable substances which remain on the earth's surface for a long time without
decomposing. When plastic is thrown everywhere, it causes environmental pollution. When
plastics are burnt, they emit poisonous gases, which affect the health of living organisms.

Reasonable Fact-9

Environmentalists call for avoiding the use of plastics. Why?
Ans: Plastic is a non-biodegradable substance which remains on the earth's surface for a long
time without decomposing. When plastic is thrown everywhere, it causes environmental
pollution. When plastics are burnt, they emit poisonous gases which affect the health of
living organisms. So environmentalists have called for avoiding the use of plastics.

iii. Smoke from vehicles and factories: The products of combustion like carbon dioxide,
carbon monoxide, sulphur trioxide, etc. are the major air pollutants. These gaseous
pollutants come from industries and vehicles. When these gases combine with water,
they give different types of acids like sulphuric acid, nitric acid, carbonic acid, etc. They
come down in the form of rain called acid rain. Acid rain damages the plants, animals,
soil, etc. Carbon dioxide, methane, ozone, etc. also result in the greenhouse effect, which
ultimately causes global warming.

Fig. 13.7 Smoke from industries

iv. Coloring materials of foodstuff: To attract customers as well as users, different types of
colors are used in foodstuffs. All the colors are made from chemical compounds. Most
of these compounds harm our health directly or indirectly and cause short term or long
term effects.

v. Dyes and detergents: Dyes like peroxide, hypochloride, sodium hydroxide and other
bleaching agents, which are released from different industries like leather, textile, carpet,
etc. also cause chemical pollution. They destroy the natural quality and composition of
water. Detergent is another non-biodegradable cleansing agent, which remains in water
for a long time and makes the water unsuitable for drinking.

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vi. Metallic particles: Automobiles and industries release different types of metallic particles
like lead, chromium, cadmium, mercury, arsenic, etc. When these metals are inhaled by
human beings, animals, birds and fishes, directly or indirectly, they suffer from various
diseases.

Control of chemical pollution

Chemical pollution can be minimized or controlled in the following ways:

i. Population growth and over urbanization should be controlled.

ii. The overuse of insecticides and chemical fertilizers should be avoided.

iii. Production and use of non-biodegradable substances should be discouraged.

iv. Solid wastes like plastics, clothes, glasses, carpets, ceramics, etc. should be
managed in a proper way.

v. Use of colors, dyes in foodstuffs should be stopped.

vi. Toxic gases which are released by industries should not be allowed to mix in the
air.

vii. Industries should be located away from a human settlement.

viii. People should be made aware about chemical pollution and its effects.

13.12 Ways to Get Rid of Chemical Pollution

Plastics are the main agents of chemical pollution. We should use chemical fertilizers only after
testing soil. The waste materials produced from industries and automobiles should be disposed
properly. The harmful gases released from industries and automobiles should be changed into
harmless gases before releasing them into the atmosphere. Household biodegradable wastes
should be used to produce compost manure. We should be careful while using insecticides
and pesticides. We should use edible colors in food items. These activities help to reduce
environmental pollution caused by different chemical substances.

Biodegradable and Non-biodegradable Solid wastes and their
Management

The solid wastes that decay and decompose due to action of microorganisms are called
biodegradable wastes. Animal dung, wastes from kitchens, wastes form fruits and vegetables,
etc. are examples of biodegradable wastes. Similarly, the solid wastes that do not decay and
decompose due to action of microorganisms are called non-biodegradable wastes, e.g. waste
glasses, plastics, pieces of metals, etc. The amount of solid wastes is increasing day by day
in urban areas. These wastes pollute the environment. Therefore, we should manage solid
wastes properly to reduce environmental pollution.

First of all, the solid wastes should be collected in separate bins. The biodegradable and non-
biodegradable wastes should be managed on the basis of their nature.

Biodegradable wastes should be used to prepare compost manure. Non- biodegradable wastes
should be recycled and reused as far as possible. Remaining wastes should be disposed
properly using proper methods.

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