science 10

heating to produce ammonia.

(NH4)2SO4 ∆ → 2NH3 + H2SO4
Ammonium sulphate

(NH4)2CO3 ∆ → 2NH3 + H2O + CO2
Ammonium carbonate

2. By heating ammonium salts with strong base

When an ammonium salt is heated with strong alkali solution,
ammonia is produced.

NH4Cl + KOH ∆ → KCl + H2O + NH3↑

Ammonium chloride Potassium hydroxide

(NH4)2SO4 + 2NaOH ∆ → Na2SO4 + 2H2O + 2NH3↑

Ammonium sulphate sodium hydroxide

Laboratory preparation of ammonia gas

Principle

Ammonia gas is prepared in laboratory by heating the mixture of
finely powdered and dry ammonium chloride and calcium hydroxide
(slaked lime) in the ratio 2:1.

2NH4Cl + Ca(OH)2 ∆ → CaCl2 + 2H2O + 2NH3↑
Calcium hydroxide
Ammonium chloride

Thus prepared gas is passed through lime tower to obtain pure
ammonia.

Apparatus required

Hard glass test tube, delivery tube, cork, stand, burner, gas jar, red
litmus paper, etc.

Chemicals required

Ammonium chloride (NH4Cl)
Calcium hydroxide [Ca(OH)2]

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NH4Cl+Ca(OH)2 Ammonia gas

Hard glass CaO

test tube

Burner

Laboratory preparation of ammonia

Procedure

1. Crush the dry solid form of ammonium chloride and calcium
hydroxide separately into very fine powder and mix them in
the ratio 2:1 by mass.

2. Place the mixture in a hard glass test tube and clamp the
test tube on a stand in an inclined position.

3. Fit a delivery tube in a cork and insert the cork into the hard
glass test tube.

4. Insert the free end of delivery tube in an inverted dry gas jar.
The delivery tube is connected to a lime tower in order to get
pure ammonia.

5. Heat the mixture with the flame of burner.
6. Heat initiates the reaction and ammonia gas is produced. It

is collected in the gas jar by downward displacement of air.
Ammonia is collected by downward displacement of air because
it is lighter than air. Ammonia gas is not collected by downward
displacement of water because it is highly soluble in water. Ammonia
dissolves in water forming ammonium hydroxide.

NH3 + H2O → NH4OH
Ammonium hydroxide

The steam produced after the reaction should be liquefied and
collected at the upper part of test tube. If not collected at the upper
part the droplets may fall back to the bottom of test tube and cause
cracking of it. Hence, the hard glass test tube is clamped in the stand
in slanted position to protect from cracking.

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Precautions

1. The apparatus should be made air tight.
2. The hard glass test tube should be clamped in the stand in an

inclined position.
3. The reagents as well as the gas jar should be dry.

Tests of ammonia

1. Ammonia has a characteristic pungent smell. It can be
identified with the help of its pungent odour.

2. When a moist red litmus paper is inserted in the jar containing
the gas, the litmus paper turns blue.

3. When a glass rod dipped in hydrochloric acid (HCl) is brought
in contact of ammonia gas. It forms white fume of ammonium

Manufacchtluorreidoef(NamHm4Col)n.ia gas

Ammonia gas is manufactured in large scale by Haber's process. In
this process, a mixture of hydrogen and nitrogen in the ratio of 3:1
by volume is heated to about 450°C under the pressure of 200-900
atmosphere. Finely divided iron is used as catalyst and a molybdenum
(Mo) is used as promoter in the reaction.

Some metal oxides such as AL2O3, K2O, CaO or MgO can also be used
as promoter in place of molybdenum in Haber's process.

N2 + 3H2 4500C, 200-900 atm 2NH3 + heat
Fe+Mo

The reaction is reversible and exothermic.

Conditions required for Haber's process
1. Temperature of about 4500C and high pressure of about 200-
900 atmosphere should be maintained.
2. Finely powdered iron as catalyst and a metal oxide as a
promoter should be used.
3. Large amount of nitrogen and hydrogen should be used.

Properties of ammonia

Physical properties
1. It is a colourless and tasteless gas with pungent smell. It
causes eye irritation.
2. It is lighter than air.
3. It turns moist red litmus paper into blue.
4. It is neither combustible nor the supporter of combustion.

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5. It is highly soluble in water.
6. It liquefies at -33.4°C and solidifies at -78°C.

Chemical properties

1. Ammonia dissolves in water to give ammonium hydroxide
(ammonia solution).

NH3 + H2O → NH4OH

2. Ammonia reacts with acids to produce ammonium salts.

NH3 + HCl → NH4Cl

2NH3 + H2SO4 → (NH4)2SO4

NH3 + HNO3 → NH4NO3

3. Ammonium hydroxide (ammonia solution) reacts with acid
to give salt and water.

2NH4OH + H2SO4 → (NH4)2SO4 + 2H2O

4. When ammonia is heated with carbon dioxide at about 150°C
under high pressure, urea is produced. Urea is a fertilizer.

2NH3 + CO2 1500C NH2—CO—NH2 + H2O
Pressure urea

5. When ammonia is heated with oxygen, it burns with greenish
yellow. This reaction produces nitrogen and water.
4NH3 + 3O2 ∆ → 2N2 + 6H2O

Uses of ammonia
i) If is used in the manufacture of chemical fertilizers like
ammonium nitrate, ammonium phosphate, urea, etc

ii) Liquid ammonia is used in refrigerators and cold storages.

iii) It is used to develop blue print of maps.

iv) It is used to manufacture different types of industrial
products like nitric acid, plastics, dyes, nylon, rayon, etc

v) It is used to make medicines like ammonium carbonate,
ammonium chloride, etc.

vi) Liquid ammonia is used as laboratory reagent.

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Activity10 .1 To demonstrate that ammonia is highly soluble in water

and basic in nature.

Materials required:

Round bottomed flask, glass tube, beaker, Fountain
stand with clamp etc.
Round
Chemicals required: bottom flask

Ammonia gas, water, phenolphthalein NH3
indicator, etc.

Procedure:

A round bottomed flask filled with

ammonia gas is taken and glass tube Trough

is fitted on it using a cork. The other Water

end of the glass tube is kept within Fountain experiment

the water containing some drops of

phenolphthalein. The glass tube is provided with a jet inside the

round bottomed flask. When ammonia gas it cooled, it creates

low pressure inside the flask, so some water drops rise up in the

flask and form ammonium hydroxide. As a result, more vacuum,

is created inside the flask. Hence, water moves up with pressure

to fill up the vacuum which looks like fountain.

Observation:

Water fountain is observed inside the round bottomed flask
for some time. The water (ammonia solution) inside the round
bottomed flask looks pink.

Conclusion:

Ammonia is highly soluble in water. It is basic in nature because
it turns phenolphthalein pink.

Learn and Write

1. Carbon dioxide gas is used in a fire extinguisher. Why?

Carbon dioxide gas is heavier than air and hence occupies the
lowermost layer in the atmosphere. When carbon dioxide is
supplied over the burning objects, it displaces oxygen and covers
the burning objects, it displaces oxygen and covers the burning
object as that by a blanket. Thus the fire gets extinguished.

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2. Solid carbon dioxide is called dry ice. Why?

Carbon dioxide gets solidified at –78°C. The solid carbon dioxide
melts without wetting other particles like paper, clothes, etc.
Therefore, it is called dry ice.

3. Why are carbon dioxide and ammonia not collected by the
displacement of water?

Both carbon dioxide and ammonia gas are soluble in water.
Therefore, they are not collected in a gas jar by the displacement
of water.

4. Bubbles come out when we open a bottle of soda water. Why?

CO2 gas is dissolved at high pressure in soda water. When we
open a bottle of soda water, the pressure decreases and CO2
comes out in the form of bubbles.

Main points to remember

1. Carbon dioxide gas is prepared in the laboratory by the action
of dilute hydrochloric acid in calcium carbonate.

2. Carbon dioxide is not collected in the gas jar containing water
because it is soluble in water.

3. When carbon dioxide gas is highly compressed or cooled down below
-780C, it is converted into solid form which is known as dry ice.

4. Fire extinguisher is a protective device which produces carbon
dioxide to extinguish fire.

5. In laboratory, ammonia gas is prepared by heating the mixture
of ammonium chloride and slaked lime in the ratio of 2:1.

6. When the mixture of nitrogen and hydrogen in the ratio of 1:3 by
volume is heated in the presence of finely divided iron as catalyst
and a metal oxide as promoter at a temperature of about 4500C
under pressure of about 200-900 atmosphere, ammonia gas is
formed. This process is called Haber's process.

7. The Haber's process involves the reversible and exothermic reaction.
8. Ammonia gas is not collected by downward displacement of

water because it is highly soluble in water.

Exercise

A. Choose the best alternative.

1. Which gas is prepared by the action of dilute hydrochloric
acid on calcium carbonate?

a. H2 b. O2 c. CO2 d. NH3

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2. What is the percentage of CO2 gas in the atmosphere?

a.0.03% b. 0.3% c. 0.4% d. 0.95%

3. What chemicals are contained in a fire extinguisher?

a. NaHCO3 b. H2SO4 c. NaHCO3 + H2SO4 d. CaCO3

4. What product is obtained when ammonia is heated with

carbon dioxide at about 1500°C under high pressure?

a. Nitric oxide b. Urea

c. Ammonium carbonate d. Nitrogen gas

5. Sal ammoniac

a.NH3 b. (NH4)2SO4 c. (NH4)2CO3 d. NH4Cl

B. Answer these questions in brief.

1. Name the chemicals which are required to prepare carbon
dioxide gas in the laboratory.

2. Name the gas formed when hydrochloric acid is treated with
the pieces of limestone.

3. Name the products of the reaction between carbon dioxide
and burning magnesium.

4. What is dry ice? What is it used for?

5. Give the balanced chemical equation involved in photosynthesis.

6. How can you know whether the gas jar is filled with carbon
dioxide gas in the lab preparation of carbon dioxide?

7. Write down any four uses of carbon dioxide gas.

8. Name two chemicals which are required to prepare ammonia
gas in the laboratory.

9. Write down any two chemical properties of ammonia gas.

10. What is Haber's process? Write with balanced chemical
equations.

11. What are the essential conditions to carry out Haber's
process?

12. How can you know whether the gas jar is filled with ammonia gas?

13. Write down any four uses of ammonia gas.

14. How is ammonium sulphate (fertilizer) prepared from
ammonia?

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15. Which gas is formed when the mixture of sodium hydroxide
and ammonium sulphate is heated? How do you identify the
gas formed in this reaction?

16. Write down the formula and chemical names of limestone,
quick lime, slaked lime and urea.

17. Which gas is used for the following purposes?
(a) To develop blue print of maps.
(b) Fire extinguisher.

C. Give reasons:

1. The mixture of carbon dioxide and water tastes sour.

2. Carbon dioxide is collected by upward displacement of air.

3. Dilute sulphuric acid is not used in place of dilute hydrochloric
acid in the lab preparation of CO2.

4. Carbon dioxide gas extinguishes fire.

5. Solid carbon dioxide is called dry ice.

6. Ammonia gas is not collected by downward displacement of
water.

D. What happens when

1. Limestone is heated strongly?

2. Carbon dioxide is passed through lime water for short time?

3. Carbon dioxide is passed through lime water for long time?

4. A burning magnesium ribbon is introduced into a jar
containing carbon dioxide gas?

5. Ammonia reacts with water.

6. Mixture of ammonia and carbon dioxide is heated to 150°C
under high pressure?

7. A glass rod dipped in dil. HCl is introduced into the jar
containing ammonia gas.

8. Ammonium carbonate is heated?
E. Diagrammatic questions:

1. Draw a labelled diagram of the laboratory preparation of
carbon dioxide gas.

2. Draw a labelled diagram for the preparation of ammonia gas
in laboratory.

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Project Work

Take some lime powder from the market. Add about 2 spoonfuls of
lime powder into a liter of clean water in a trough and stir the mixture
well to prepare lime water. Take a straw or a thin pipe to blow air into
the lime water from your mouth. What will you observe? Explain your
observation with reasons.

Glossary : very bright so that it is difficult to look at
: to put out fire
• Dazzling : having a strong repulsive smell or taste
• Extinguish : syringe, plunger, a narrow pointed opening
• Pungent : spray, spout, jet
• Nozzle : a substance taking part in a chemical reaction
• Fountain
• Reagent

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Chapter

11 Metals
Georgius Agricola

He is known as the pioneer in mineralogy.

Estimated Periods: 8 (7T+1P)

Objectives

At the end of the lesson, students will be able to:
• explain the main metals (iron, aluminium, copper, gold, silver) present in the

nature;

• identify and explain the physical and chemical properties of those metals;

• explain the uses of those metals.

Metals are the electropositive solid elements which are the good
conductors of heat and electricity. All metals (except mercury) are
solid at ordinary temperature. They are malleable and ductile.
Malleability is the property of metals due to which they can be
converted into thin sheet by hammering whereas ductility means the
property of metals to be drawn into wire. The metals are sonorous.
They have high melting and boiling points. Metals have metallic
luster.
The non-metals occur in solid, liquid and gas state. Non-metals
are the electronegative elements which are bad conductors of heat
and electricity. The non-metals do not have metallic luster except
graphite and iodine. They are not malleable and ductile.
The elements which have the properties intermediate between
metals and non-metals are called metalloids. For example, silicon,
arsenic, antimony, germanium, etc. The metalloids have following
characteristics.

a. They are poor conductors of heat and electricity.
b. They have metallic luster.
c. They are not malleable and ductile in general.

Minerals and ores

Minerals are the naturally occurring substances which contain
metals in the form of compounds with impurities. All minerals are
not suitable to extract metals because they may contain very less
amount of metals. Clay (Al2O3, 2SiO2 .2H2O), Cuprite (Cu2O), horn

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silver (AgCl), cryolite (Na3Al F6), feldspar (K Al Si3O8) etc. are
minerals.
The naturally occurring minerals from which metals can be extracted
profitably are called ores. Thus, every ore is mineral but every mineral
is not an ore. For example, Cuprite (Cu2O) is an ore of copper, horn
silver (AgCl) is an ore of silver, magnetite (Fe3O4) is an ore of iron,
etc. They are minerals too.

Difference between minerals and ores:

Minerals Ores

1. Metal may be present 1. Metal is present in comparatively
in more or less amount more amount in ores.
in minerals.

2. All minerals are not 2. Those minerals from which metals
suitable to extract can be extracted are called ores.
metals.

3. All mineral are not ores. 3. All ores are minerals.

Examples: clay, cryolite, Examples: haematite, siderite,
bauxite feldspar etc. bauxite etc.

Metallurgy

The branch of science which deals with the extraction of metal from
the ores and manufacture of metal products is called metallurgy. An
ore may contain a large amount of sand, soil and rocky materials
called gangue. The process of removal of gangue from an ore is called
concentration of ore. There are different steps in the metallurgical
processes. They are crushing of one, pulverization, calcination,
roasting, reduction, refining, etc.

Some important metals

Iron, copper, aluminium, silver and gold are gold are very useful
metal. The occurrence, extraction, properties and uses of these
metals are discussed below:

Iron

Symbol : Fe
Atomic number : 26
Atomic weight : 56

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Valency : 2, 3

Position in the periodic table : Period: 4, Group: VIII, d-block or
transition element

Colour : grey white

Electronic configuration:

Shell K L MN
No of electron 2 8 14 2
1s2,2s22p6,3s23p6,4s2,3d6
Sub-shells

Occurrence

Iron is a reactive metal and is not found in native state. When a
metal exists in free state, it is said to be in native state. It occurs only
in the combined state. It can be found in animal body and in the rocks
as ore. The chief ores of irons are:

1 Haematite Fe2O3
2. Magnetite Fe3O4
3. Siderite FeCO3
4. Limonite Fe2O3.3H2O
5. Iron pyrite Fe2S2

Extraction of iron

Haematite contains the highest percentage of iron. So, it is regarded
as the chief ore of iron. It contains about 72.5% iron. The haematite
ore is collected from the mines and crushed into smaller pieces in
jaw crusher. It is then pulverized into fine powder in stamp mills.
Sand, clay, dust, organic matter, etc are removed from powdered ore
by washing it in water. Iron is a magnetic substance but impurities
present in it are non-magnetic. So, non-magnetic substances are
separated by magnetic separation method. The ore is then mixed
with coke and heated strongly in excess air below the melting point
of iron. This process is called roasting. Thus, the impurities are
removed and iron is obtained in molten form. The molten iron is then
allowed to solidify in a big lump which is called pig iron. The pig iron
is re-melted and poured into mould to get cast iron. The cast iron
contains the highest percentage of carbon and other impurities. It is
further purified to get different varieties of iron.

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Properties of Iron
Physical properties

1. Iron is a shiny grey coloured metal.
2. It melts at about 15000C and boils at about 25000C.
3. It is a good conductor of heat and electricity.
4. Its specific gravity is 7.86.
5. Iron becomes non-magnetic above 7700C.

Chemical properties

1. Action with oxygen: When iron is heated in air, it forms
ferrosoferric oxide.

3Fe + 2O2 ∆→ Fe3O4

2. Action with steam: Iron reacts with steam at high
temperature to form ferrosoferric oxide and hydrogen.

3Fe+4H2O ∆→ Fe3O4+4H2↑

3. Action with halogens: When iron is heated with halogens,
it directly combines with them to form halides.

2Fe + 3Cl2 ∆→ 2FeCl3

4. Action with sulphur: Iron, on being heated with sulphur,
forms iron sulphide.

Fe + S ∆→ FeS

5. Rusting: The process of formation of brown layer on the
surface of iron when it is exposed to moist air is called rusting.
The rust is the hydrated form of ferric oxide (Fe2O3. xH2O).

4Fe + 3O2 + xH2O → 2Fe2O3.xH2O (rust)

Uses It is used in the manufacture of rods, wires, pipes, nuts and
1. bolts, nails, etc.
It is used for making household utensils.
2. It is used in making building, bridges, vehicles, etc.
3. It is used to make different types of instruments and weapons.
4. It is used in the manufacture of steel.
5.

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Aluminium

Symbol : Al

Atomic number : 13

Atomic weight : 27

Valency :3

Position in the periodic table : Period 3, Group IIIA, P-block
element

Colour : Silvery white

Electronic configuration:

Shells K LM
No of electrons 2 83
1s2, 2s22p6, 3s23p3
Sub-shells

Occurrence

It is the most abundant metal on the earth's crust. It is always found
in combined state in nature and it does not occur in native state. The
main ores of aluminium are:

1. Bauxite Al2O3. 2H2O
2. Felspar K(AlSi3O8)
3. Cryolite Na3Al F

Extraction of aluminium

Bauxite (Al2O3.2H2O) is the chief and cheap ore of aluminium. The
ore is crushed into powdered form. The powdered ore is heated at
high temperature with sodium carbonate in the presence of carbon
dioxide gas. The strong heating converts bauxite into aluminium
oxide (alumina). Then aluminium oxide is electrolyzed to get about
99% pure aluminium.

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Properties

Physical properties
1. It is a silvery white and light metal.
2. It is highly malleable and ductile.
3. It is good conductor of heat and electricity,
4. Its melting point is 6600C and boiling point is 18000C.
5. Its specific gravity is 2.7.

Chemical properties

1. Action with air and water: Pure aluminium is not affected
by air and water. But impure aluminium reacts with moist
oxygen to form aluminium oxide. Since aluminium oxide
forms thin and hard layer on its surface, air and water have
very less effect on aluminium.
4Al + 3O2 → 2Al2O3 (moist)

2. Action with halogens

Aluminium reacts with halogens (Cl, Br, I) to form halides.
2Al + 3Cl2 → 2AlCl3
2Al + 3Br2 → 2AlBr3
3. Action with nitrogen: When aluminium is strongly heated
with nitrogen, aluminium nitride is formed.

2Al + N2 ∆→ 2AlN (Alminium nitride)

Uses

1. Aluminium is a rusting resistant light metal. So, it is used
for making body of aeroplane, cars, buses, etc.

2. Aluminium foil is used for wrapping foods, chocolates,
photographic film, medicines, etc.

3. It is used in making different alloys.
4. Electric cables are made from aluminium.
5. It is used for making coins.
6. Powdered aluminium is mixed in oil to form paint.

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Copper (a coinage metal)

Symbol : Cu

Atomic number : 29

Atomic weight : 63.5

Valency : 1, 2

Colour : Brownish red

Position in the periodic table : Period 4, Group IB, d-block

element.

Electronic configuration:

Shell KL MN
No of electron 2 8 18 1
1s2,2s22p6,3s23p6,4s1,3d10
Sub-shells

Occurrence

Copper is found in native as well as in combined state in nature. In
combined state, it occurs as ores in the following forms:

1. Copper pyrite or chalcopyrite CuFeS2
2. Copper glance or chalcocite Cu2S

3. Azurite [2Cu CO3. Cu(OH)2]

4. Malachite [Cu CO3. Cu(OH)2]
5. Cuprite Cu2O

Extraction of copper

Copper pyrite or chalcopyrite (CuFeS2) is the chief ore of copper.
The copper pyrite ore is crushed into powdered form and then

concentrated by froth flotation process. Froth floatation is the process

of concentration of ore by agitating the mixture of ore, pine oil and

water by blowing air. This process drives sulphide ore on the top as

froth and impurities settle at the bottom. The concentrated ore is

then roasted in a blast furnace by passing hot air.

The roasted ore is then mixed with coke and sand. The mixture is

heated in a furnace to remove some impurities. Then the ore is further

heated strongly in a furnace called Bessemer converter by blowing a

blast of hot air whereby about 99.4% pure copper is obtained in liquid

state.

The molten copper thus obtained is called blister copper. This copper

is further purified by electrolysis.

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Properties

Physical properties
1. It is a hard and red brownish metal.
4. Its specific gravity is 8.93.
5. Its melting point is 10830C and boiling point is 23500C.
3. It is a good conductor of heat and electricity.
2. It has a good degree of malleability and ductility.

Chemical properties

1. Action with air: When copper is heated with air, it gives

cupric oxide (black). If it is heated at the temperature above

11000C, cuprous oxide (red) is formed.

2Cu + O2 ∆ 2CuO
< 1100°C

black (cupric oxide)

4Cu + O2 ∆ 2Cu2O
> 1100°C

red (cuprous oxide)

2. Action with halogens: Copper directly combines with
halogens to form halides on heating.

Cu + Cl2 ∆→ CuCl2
3. Action with sulphur: When copper is heated with sulphur,

copper sulphide is formed.

2Cu + S → Cu2S
4. Action with other salt solution: Copper can displace the

less reactive metals such as silver, gold and platinum from
their respective salt solution.

Cu + 2AgNO3 → Cu(NO3)2 + 2Ag↓

Uses It is used to make household utensils such as cooking utensils,
1. boilers, water pots etc.
It is used for making electric wires and other appliances.
2. It is used to make coins. So, it is also known as coinage metal.
3. It is used for electroplating and electrotyping
4. Copper salts are used as insecticides and germicides.
5. It is used for making alloys such as brass, bronze, etc.
6.

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Silver (a coinage metal)

Symbol : Ag

Atomic number : 47

Atomic weight : 107.88 (=108)

Valency :1

Position in the periodic table : Period; 5, Group 1B, d-block
(transition element).

Colour : Lustrous white

Electronic configuration

Shells K LMN O
No. of electrons 2 8 18 18 1
1s2,2s22p6,3s23p6,4s2,3d10,4p6,5s1,4d10
In sub-shells

Occurrence

It occurs in native as well as combined state. In combined form, silver
occurs as follows:

1. Argentite or silver glance Ag2S

2. Silver copper glance (AgCu)2S

3. Horn silver AgCl

4. Ruby silver or pyrolite 3Ag2S.Sb2S3

Extraction of silver

Argentite (Ag2S) is the main are of silver. So, silver is usually extracted
from argentite by leaching process. Since the process involves the use
of sodium cyanide solution, it is also known as cyanide process. The
crushed and ground ore is concentrated by froth flotation process.
The concentrated ore is then treated with sodium cyanide solution
and heated in a furnace in the presence of air. This turns the ore into
sodium argento-cyanide solution. Then, zinc is added to the argento
cyanide solution to displace silver in the form of precipitate. The
silver is separated by filtration and is further purified by electrolysis.

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Properties
Physical properties

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

Chemical properties

1. Action with sulphur: Silver, on heating with sulphur,
produces silver sulphide.

2Ag + S ∆→ Ag2S

Silver sulphide

2. Action with halogens: When silver is heated with halogens,
silver halides are formed.

2Ag + Cl2 ∆→ 2AgCl (white)

Silver chloride

2Ag + Br2 ∆→ 2AgBr (pale yellow)

Silver bromide

2Ag + I2 → 2AgI (yellow)

Silver iodide

Uses It is used for making valuable utensils, coins and jewellery.
1. It is used for silver plating.
2. It is used in the manufacture of silver nitrate which is a very
3. useful laboratory reagent.
It is used for silvering mirrors and filling teeth.
4. Silver bromide (AgBr) is used in photography.
5.

Gold (a coinage metal)

Symbol : Au
Atomic number : 79
Atomic weight : 197.2
Valency : 1, 3

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Position in the periodic table : Period 6, Group IB, d-block
(transition element).

Colour : Lustrous yellow

Electronic configuration

Shells K L MNOP
No. of electrons 2 8 18 32 18 1
1s2,2s22p6,3s23p6,4s2,3d10,4p6,5s2,4d10,5p6,6s1,

4f14,5d10

Occurrence

Gold is mostly found in native state because it is a noble metal which
does not react readily with other elements. It is usually found in
nature mixed with quartz rocks (reef gold) or in alluvial sand. In
combined state, it occurs as calverite (AuTe2).

Extraction of gold

Gold is extracted from alluvial or sandy soil rich in gold. The alluvial
sand containing gold is mixed with water and run along a sluice. A
sluice is an inclined channel provided with cavities and crosswire
strips called riffles. When a strong water current moves along the
sluice, it takes away sand and gravel but the heavier gold particles
are retained in the cavities. Gold is then recovered from the cavities.

Properties

Gold is the most malleable and ductile metal. So, it is also known as
the king of all metals.

Physical properties

1. It is a shinning yellow metal.
2. It is a good conductor of heat and electricity.
3. It is highly malleable and ductile.
4. It specific gravity is 19.3.
5. Its melting point is 1063°C and boiling point is 2530°C.

Chemical properties

1. Gold is noble or non-reactive metal so, it is not attacked by air
and water.

Times' Crucial Science Book - 10 216

2. Reaction with acid:

No single acid (either dilute or concentrated) can affect gold.
But a mixture of concentrated hydrochloric acid and nitric acid
dissolves gold forming auric chloride. The mixture of concentrated
hydrochloric acid and nitric acid in the ratio of 3:1 by volume is
called aquaregia (Kingly water). Aquaregia dissolves gold due to
formation of nascent chlorine.

The reaction takes place in two steps.

3HCl + HNO3 → NOCl + 2H2O + 2Cl

Nitrosyl chloride

2Au + 6Cl → 2AuCl3
3. Action with halogens: Gold on being heated with halogens
forms halides.

2Au+3Cl2 ∆ → 2AuCl3

Uses

1. It is used for making jewellery, statues, etc,

2. It is used for making coins and medals.

3. It is used for filling teeth.

4. Compounds of gold are used in photography and medicines.

5. It is used for gold plating.

Learn and Write

1. Iron becomes brown colour when exposed to moist air. Why?
When iron is exposed to moist air, the iron reacts with oxygen
forming hydrated ferric oxide which is brown in colour.
4Fe + 3O2 + xH2O → 2Fe2O3. xH2O

2. Aluminium is used to make body of aeroplanes. Why?
Aluminium is light metal. It does not get rusted. Therefore, it is
used for making the body of aeroplanes.

3. Gold is called the king of all metals. Why?
Gold is the most malleable and ductile metal. It does not get
rusted and remains in the native form even it gets exposed to
various chemicals. Therefore, gold is called the king of all metals.

217 Times' Crucial Science Book - 10

Main points to remember

1. Metals are the electropositive solid elements which are good
conductors of heat and electricity.

2. Non-metals are the electronegative elements which are bad
conductors of heat and electricity.

3. Metalloids are the elements whose properties are intermediate
between metals and non-metals.

4. Minerals are the naturally occurring substances which contain
metals.

5. The naturally occurring minerals from which metals can be
extracted profitably are called ores.

6. The branch of science which deals with the extraction of metals
from the ores and manufacture of metal products is called
metallurgy.

7. A brief summary of ores, physical constants and main uses of
metals is given below:

S.N Metal Chief ores minerals Metal Physical Applications
extracted constants (Main uses)
from (Physical
(chiefore) properties) Iron is used to
manufacture:
1. a. Haematite (Fe2O3) Colour : shiny
grey a. steel
Iron (Fe) b. Magnetite (Fe3O4)
State : Hard b. rods, wires,
Z : 26 c. Siderite (FeCO3) solid pipes, nuts and
bolts, nails etc.
A : 56 d. Limonite M.P: 1500°C
c. instrument and
Valency: 2,3 (Fe2O3.3HO2) B.P : 2500°C weapons.

Period : 4 e. Iron pyrite (FeS2) Haematite Specific gravity d. household
Group: 8 (Fe2O3) : 7.86 utensils.
f. copper pyrite
(CuFeS2) Conductivity: e. buildings, bridges,
Good vehicles etc.
Conductor

Times' Crucial Science Book - 10 218

2. Aluminum a. Bauxite Colour: Silvery Aluminium
(Al) (Al2O3.2H2O) white is used to
Z:13 b. Cryolite (Na3AlF6) manufacture:
A: 27 c. Felspar (KAl State : Hard
Valency: 3 Si3O8) solid a. paints.
Period : 3
Group :13 Bauxite M.P: 660°C b. electrical
(Al2O3.2H2O) wires, body of
B.P : 1800°C aeroplane, cars,
buses etc.
Specific gravity
: 2.7 c. aluminium
foils for wrapping
Conductivity : foods, medicines
Good conductor etc.

d. coins.

e. electric cables,
alloys etc.

3. Cupper (Cu) a. Copper pyrite Colour: Red Copper is used to
brownish manufacture :
Z : 29 or chalcopyrite Copper
A:63.57 (CuFeS2) pyrite or State : Hard a. electric wire
chalcopyrite solid and other
b. copper glance or appliances.
M.P: 1083°C
Valency: 1,2 chalcocite (Cu2S) (CuFeS2) b. household
B.P : 2350°C utensils such as
Period : 4 c. Cuprite (Cu2O) cooking utensils,
Specific gravity water pots etc.
Group : 11 d.Malachite [CuCO3. : 8.93
Cu(OH)2]

Conductivity : c. coins.
Good conductor
d. alloys such as
brass, bronze etc.

4. Silver (Ag) a. Argentite or silver Argentite or Colour :Shiny Silver is used to
Z:47 glance (Ag2S) silver glance white manufacture:
A:107.88 (Ag2S)
Valency : 1 b. Horn silver (AgCl) State : Hard a. jewellery,
Period : 5 solid coins and
Group : 11 c. Silver copper valuable utensils.
glance [(AgCu)2S] M.P: 960°C
b. silver plate
d. Ruby silver or Specific gravity articles.
pyrolite (Ag2Sb2S3) : 10.5
c. silver nitrate.
Conductivity :
Good d. silver bromide,
which is used
Conductor in photography.
Silver is also
used for silvering
mirrors and
filling teeth.

5. Gold (Au) a. Alluvial sand Alluvial sand Colour: Gold is used in
Z:79 (Soil) Lustrous making:
A:197.2 yellow
b. Quartz rocks a. jewellery,
State: Hard statues etc.
solid
Valency : 1,3

Period : 6

Group : 11

219 Times' Crucial Science Book - 10

Exercise

A. Choose the best alternative.

1. The process in which carbonate and hydroxide ores are
strongly heated in limited supply of air below the melting
point of metal is called

a. Calcination b. Roasting c. Reduction d. Refining

2. What is the chief ore of iron?

a. Siderite b. Magnetite

c. Haematite d. Limonite

3. Metal used for making the body of aeroplanes, cars, buses, etc

a. Iron b. Copper

c. Steel d. Aluminium

4. Which of the following is a coinage metal?

a. Copper b. Silver c. Gold d. All of these

5. Metal mainly found in native state in nature

a. Silver b. Gold c. Copper d. Sodium

B. Answer these questions in brief.
1. Write down electronic configuration of iron in terms of sub-shells.
2. Name any two ores of iron.
3. Which metal is obtained from haematite?
4. Which metal is extracted from magnetite ore?
5. What is rusting? How does iron get rusted? Write the
molecular formula of rust.
6. Write down two properties of aluminium that make it suitable
for building body parts of an aeroplane.
7. Aluminium is very reactive metal. Why don't the foods in
aluminium pots react with pots?
8. What metal is found in chalcocite?
9. Write down any four uses of copper.
10. Name the metal obtained from argentite.
11. What happens when copper is heated with oxygen? Explain
with balanced chemical equations.
12. Name the metals which can be extracted from argentite and

Times' Crucial Science Book - 10 220

chalcopyrite.
13. What is aquaregia? Name the element found in aquaregia

which can dissolve gold.
14. Write down balanced chemical equation for the reaction

between gold chloride and copper.
15. Write down any two properties of gold that make it suitable

for making jewellery and ornaments. Give reasons.
16. Name the element found in aquaregia which reacts with

gold. What compound is formed by the reaction between
the element and the gold? Write molecular formula of the
compound.
17. Name any three ores of aluminium

18. Write down any four uses of gold.

19. Mention any two properties of iron that make it suitable for
making pots and pans.

C. Give reasons.

1. A moist iron piece left in air becomes reddish brown.

2. Gold is found in native state but not iron.

3. Gold is called the king of all metals.

D. What happens when?

1. Iron reacts with copper sulphate solution?

2. Aluminium is treated with alkali solution in the presence of
oxygen.

3. Aluminium is heated with nitrogen gas.

E. Write down differences between:

1. Ores and Minerals 2. Metals and Metalloids

3. Calcination and Roasting 4. Haematite and Azurite

221 Times' Crucial Science Book - 10

Project Work

Study the uses of different metals at your home and write down
their physical properties and uses.

Glossary : grinded, broken down into pieces

• Crushed : a piece without any particular shape
• Lump
• Calcination : to heat an ore supplying very less oxygen
• Extraction
: taking out or separating a desired substance
• Reduction from others (e.g. a metal from an ore)

• Alluvial : process of removing oxygen from a metal
chemically
• Native form
: consisting of, or formed by sediment deposited
by flowing water

: element form, uncombined form

Times' Crucial Science Book - 10 222

Chapter Hydrocarbon

12 and

Its Compounds Friedrich Kekulé

Friedrich August Kekulé was a

German organic chemist. He known

for proposing the structure of

benzeEnset.imated Periods: 5 (4T+1P)

Objectives

At the end of the lesson, students will be able to:
• define hydrocarbons;

• explain various types of hydrocarbons and their compounds.

The compounds which are formed by the chemical combination of
carbon and hydrogen are called hydrocarbons. The hydrocarbons are
called organic compounds. The branch of chemistry which deals with
hydrocarbons and their derivatives is called organic chemistry. The
organic compounds consist of covalent bonds between carbon and
hydrogen or carbon and carbon. Because of co-valency, a carbon atom
can form a chain with other carbon atoms. Hence, a number of carbon
atoms can combine with each other to form a chain of carbon atoms.
The property of carbon to form covalent bonds with its own atoms is
called catenation.

Naming of hydrocarbons

The organic compounds can be known by two kinds of names-common
or trivial name and scientific or IUPAC name. The name of a simple
hydrocarbon involves the use of word root and suffix. The word root
is based upon the number of carbon atoms in the molecule.

a) The word root according to number of carbon atoms is given
below:

No. of C-atoms Word root
Meth
C1 Eth
C2 Prop
C3 But
C4 Pent
C5

223 Times' Crucial Science Book - 10

C6 Hex
C7 Hept
C8 Oct
C9 Non
C10 Dec

b) The word root is followed by a primary suffix. The primary
suffix is based on the number of bonds between the carbon
atoms.

Hydrocarbon Type of bond Suffix
Alkane Single (C–C) – ane
Alkene Double (C=C) – ene
Alkyne Triple (C≡C) – yne

For example

CH3 — CH2 – CH3
Word root: Prop (because there are 3 carbon atoms)

Primary suffix: ane (because there are single bonds)

Therefore, the name of the compound = Prop + ane = Propane.
c) Ifthereisfunctionalgroupinacompound,thenameofthecompound

consists of word root, primary suffix and secondary suffix.

Types of hydrocarbons

The hydrocarbons can be divided into two types based on the kind of
bond present between the adjacent carbon atoms. They are: saturated
hydrocarbons and unsaturated hydrocarbons.
1. Saturated hydrocarbons
The hydrocarbon in which the adjacent carbon atoms are linked
by a single covalent bond is called saturated hydrocarbon. Such
hydrocarbons are also called alkanes. For example, methane (CH4),
ethane (C2H6), propane (C3H8), etc.
The general formula of saturated hydrocarbon is CnH2n+2 where 'n'
represents the number of carbon atoms. For example, if the saturated
hydrocarbon has 1 carbon atom, according to the formula Cn+H2n+2=
C1H2×1+2= CH4 (Methane). If 2 carbon atoms are present, then C2H2×2+2
= C2H6 (ethane and so on).
Some more examples of alkanes with their molecular formula,
structural formula and IUPAC (International Union of Pure and
Applied Chemistry) name are given below:

Times' Crucial Science Book - 10 224

S.N Name Molecular Condensed Structural formula
formula formula

H

1. Methane CH4 CH4 HC H
(C1) H

HH

2. Ethane C2H6 CH3CH3 HC C H
(C2) HH

HHH

3. Propane C3H8 CH3CH2CH3 HC C C H
(C3) HHH

4. Butane C4H10 CH3CH2 HHHH
(C4) CH2CH3 HC C C C H

HHHH

5. Pentane C5H12 CH3CH2CH2 HHHHH
(C5) CH2CH3 HC C C C C H

HHHHH

6. Hexane C6H14 CH3CH2CH2 H H H H HH
(C6) CH2CH2CH3 HC C C C CC H

H H H H HH

7. Heptane C7H16 CH3CH2CH2 H H H H HH H H
(C7) CH2CH2 HC C C C CC C
CH2CH3
H H H H HH H

8. Octane C8C18 CH3CH2CH2 H H H H HH H H
(C8) CH2CH2CH2 HC C C C CC C C H
CH2CH3
H H H H HH H H

9. Nonane C9C20 CH3CH2CH2 H H H H HH H H H
(C9) CH2CH2CH2 HC C C C CC C C C H
CH2CH2CH3
H H H H HH H H H

225 Times' Crucial Science Book - 10

CH3CH2CH2 H H H H HH H H H H

10. Decane C10H22 CH2CH2CH2 H C C C C C C C C C C H
(C10)
CH2CH2CH2 H H H H HH H H H H

CH3

The alkanes are also known as paraffins because they are chemically
less reactive.

2. Unsaturated hydrocarbons

The hydrocarbons in which the adjacent carbon atoms are linked

by multiple (double or triple) covalent bonds are called unsaturated

hydrocarbons. For example, ethene (C2H4), propene (C3H6), ethyne
(C2H2), etc. Unsaturated hydrocarbons are of two types.

a. Alkenes (olefins) b. Alkynes (acetylenes)

a. Alkenes

The hydrocarbons in which the two carbon atoms are linked by double
covalent bonds are called alkenes. The alkenes are also known as
olefins. The general formula of alkenes is CnH2n where 'n' represents
the number of carbon atoms.
The molecular formula, condensed formula, structural formula and
IUPAC names of some alkenes are given the below:

S.N Name Molecular Condensed Structural
formula formula formula

Ethene HH
(Ethylene)
1. C2H4 CH2=CH2 C =C

HH

HH H

2. Propene C3H6 CH3CH=CH2 H C C = C
3. Butene C4H8
4. Pentene C5H10 HH

CH3CH2 HH H
CH=CH2
H C C C= C

HHH H

HH H H H
CH3CH2CH2 H C C C C = C
CH=CH2
HH H H

Times' Crucial Science Book - 10 226

b. Alkynes

The hydrocarbons in which two carbon atoms are connected by triple
covalent bonds are called alkynes. The general formula of alkyne
is CnH2n-2. The molecular formula, condensed formula, structural
formula and the IUPAC name of first four members of alkynes are
given below:

S.N Name Molecular Condensed Structural
formula formula formula

1. Ethyne C2H2 CH ≡ CH H – C ≡ C–H
(acetylene)
H

2. Propyne C3H4 CH3C ≡CH H C C ≡ C H

H

3. Butyne C4H6 CH3CH2 HH C≡C H
C ≡ CH HC C

HH

4. Pentyne C5H8 HH H
CH3CH2CH2 H C C C C ≡ C H

C ≡ CH
HH H

Functional group

An atom or group of atoms bonded to a carbon atom which determines
the chemical properties of an organic compound is called functional
group. Some examples of functional groups are given in the table.

S.N Name of functional Symbol Structure Class of organic
group compounds
– OH –O–H alcohol
1. Hydroxyl –O– –O– ether
aldehyde
2. Ethereal O
ketone
3. Aldehyde – CHO CH
O Carboxylic acid
4. Keto – CO –
C
5. Carboxyl – COOH O

C OH

227 Times' Crucial Science Book - 10

Alkyl group

A group of atoms (radical) derived from alkanes by removing one
hydrogen atom is called alkyl group or alkyl radical. It is represented
by R in short form.

Alkane −H → Alkyl group.

Examples: Methane: CH4 – H = CH3 (Methyl group)
Ethane: C2H6 – H = C2H5 (ethyl group) and so on.

Homologous series

A series of organic compounds having same functional group and
two successive members differing by a CH2 unit is called homologous
series. Each member of a homologous series is called homologue.
All the members of a homologous series can be represented by the
same general formula. For example, the general formula of alcohol is
CnH2n+1OH homologous series of alcohol is:

CH3– OH Methanol
CH3–CH2–OH Ethanol
CH3–CH2–CH2–OH Propanol
CH3–CH2–CH2–CH2–OH Butanol
CH3–CH2–CH2–CH2–CH2–OH Pentanol

Characteristics of homologous series
1. All the members of a homologous series have same functional group.
2. They can be represented by the same general formula.
3. Two adjacent members of a homologous series differ by a –CH2 unit.
4. They have similar chemical properties.
5. They can be prepared by same general methods of preparation.

Some important hydrocarbons

Methane, ethane, propane and butane are some important
hydrocarbons.

Methane (CH4)

It is the simplest hydrocarbon and occurs as a colourless gas. It is
found in the gaseous state at room temperature. It is also called marsh
gas because it is formed by the decomposition of organic matter in
marshy areas. Methane is also found in natural gas, petroleum and
coal mines, bio-gas etc.

Times' Crucial Science Book - 10 228

H

HC H

CH4 H
Condensed formula
Structural formula

Uses of methane
1. It is used to make printing ink and paints.
3. It is used as a cooking fuel in the form of LPG (Liquefied
Petroleum Gas).
2. It is used to make carbon black which is needed in rubber
industries.
4. It is used in the manufacture of hydrogen.
5. It is used in manufacture of methyl alcohol (CH3OH), chloroform
(CHCl3), formaldehyde (HCHO), carbon tetrachloride (CCl4), etc.

Ethane (C2H6)

It is the second member of homologous series of alkanes which occurs
in natural gas and petroleum mines. It is a colourless gas.

HH

HC C H

CH3–CH3 HH
Condensed formula
Structural formula of ethane

Uses

1. It is used as a cooking fuel.
2. It is used to make different types of compounds.

Propane (C3H8)

It is the third member of homologous series of alkanes. It is found in
petroleum mines. It is a colourless gas.

HHH

HC C C H

CH3–CH2–CH3 HHH

Condensed formula Structural formula of propane

Uses

1. It is used as a fuel in closed bottles such as gas lighter.

229 Times' Crucial Science Book - 10

Butane (C4H10)

It is a colourless gas which can be liquefied at room temperature
under high pressure. It is also found in petroleum mine. It has two
isomers: n - butane and isobutane.

HHH

HC C C H

HHHH HH

CH3 – CH2 – CH2 – CH3 HC C C C H HC H

HHHH H

Butane n- butane Isobutane

The organic compounds having same molecular formula but different
structural formula are called isomers. The property of the organic
compounds to have isomers is called isomerism. The isomers have
different physical and chemical properties.

Uses

Butane and iso-butane are the main constituents of liquefied
petroleum gas.

Alcohol

Alcohols are the organic compounds which contain hydroxyl (– OH)
group as the functional group. They are the derivatives of alkanes
which are formed by replacing hydrogen atoms of alkane by hydroxyl
(OH) group.

For example:

CH – H CH3 – OH
4 + OH

Methane Methyl alcohol

–H

CH3CH3 + OH CH3CH2OH

Ethane Ethyl alcohol

Naming of alcohol

The IUPAC name of a simple alcohol involves three parts- word root,
primary suffix and secondary suffix.

For example: CH3CH2OH
Common name: Ethyl alcohol

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For IUPAC name:

Word root = Eth (as there are 2 C atoms)

Primary suffix = ane (as there is single bond between C atoms)

Secondary suffix = ol ('ol' represents alcohol)

Hence, IUPAC name CH3CH2OH = Eth + ane + ol

= Ethanol

Activity12 .1 Write down the IUPAC name of:

a. CH3OH b. CH3CH2CH2OH c. CH3CH2CH2CH2OH

Types of alcohols

Depending upon the number of hydroxyl groups in a molecule, there
are three types of alcohol.

a. Monohydric alcohol

The alcohol which contains only one hydroxyl group (-OH) in a molecule
is called monohydric alcohol. It is formed by the replacement of one
hydrogen atom of an alkane by one hydroxyl group.

For example, CH3 – OH
Methyl alcohol
–H

CH4 + OH
Methane

The other examples are:

CH3 – CH2 – OH CH3–CH2–CH2–OH CH3–CH2–CH2–CH2–OH

Ethyl alcohol Propyl alcohol Butyl alcohol

b. Dihydric alcohol

The alcohol which contains two hydroxyl groups (-OH) in a molecule
is called dihydric alcohol. It is formed by the replacement of two
hydrogen atoms each from one carbon of ethane by two hydroxyl
groups.

HH HH

HC C H –2 H HC C H
+2 OH

HH OH OH

Ethane Ethylene glycol

231 Times' Crucial Science Book - 10

c. Trihydric alcohol

The alcohol which contains three hydroxyl groups in a molecule is
called trihydric alcohol. Glycerol, a trihydric alcohol is formed when
three hydrogen atoms of propane are replaced by three OH groups.
For example,

HHH HH H

HC C C H –3 H HC C C H
HHH +3 OH OH OH OH

Propane Glycerol (glycerine)

Some commercially important alcohols

Methyl alcohol (CH3OH)

It is a monohydric alcohol which contains a single carbon atom in a
molecule. Its IUPAC name is methanol. It is a colourless and highly
poisonous liquid. Drinking methyl alcohol causes blindness.

H

CH3OH H C OH
H
Methanol (condensed formula)
Methanol (Structural formula)
Uses

1. It is used as fuel because it produces large amount of heat
without smoke. Hence, it is used in sprit lamp.

2. It is used for the preparation of methylated spirit.
3. It is used to manufacture perfume.
4. It is used as a solvent for paints, varnishes, oils etc.
5. It is used to make methyl chloride, formaldehyde etc, which

is an important fuel.

Ethyl alcohol (C2H5OH)

It is a colourless liquid with distinct alcoholic smell and intoxicating
effect. It has a burning taste. Its IUPAC name is ethanol. It is easily
soluble in water. In general, the term 'alcohol' is understood as ethyl
alcohol.

HH

H C C OH

HH

Ethyl alcohol (ethanol)

Times' Crucial Science Book - 10 232

Uses

1. It is used in alcoholic beverages for drinking purpose because
of its intoxicating effect.

2. It is used to make medicines, soaps, synthetic rubber etc,
3. It is used as solvent for fat, oil, paints, etc.
4. It is used in thermometer as a thermometric liquid.
5. It is used as fuel.

Glycerol or Glycerine [C3H5 (OH) 3]

Glycerol is a colourless thick liquid with sweet taste. It is soluble in
water but insoluble in ether. Glycerol is a trihydric alcohol which is
formed by replacing three H atoms (one from each carbon atom) of
propane by three OH groups. It is produced by the hydrolysis of fat
or oil in the presence of alkali.

H HH CH2OH

HC C C H or, CHOH

OH OH OH CH2OH

Uses Glycerol

1. It is used in the manufacture of soaps and cosmetics.
2. It is used as a sweetening agent in confectionery, beverages
and medicines.
3. It is used in the manufacture of printing inks and stamp pad
inks.
4. It is used for preservation of fruits and tobacco.
5. It is used as a lubricant.
6. It is used as medicine to protect skin from being dried.

Glucose

Glucose is a white crystalline powder with sweet taste. It is also
known as dextrose and is an instant source of energy. Its molecular
formula is C6H12O6. It is readily soluble in water. It is one of the
monosaccharide forms of carbohydrates. The other monosaccharides
are fructose and glactose. Glucose is directly absorbed into the blood
through small intestine. It is used by the cells of our body to produce
ATP (Adenosine Triphosphate). Our body utilizes ATP for energy.

233 Times' Crucial Science Book - 10

H H OH H H

CH2OH C C C C C
OH OH H OH O

Structure of glucose

Glucose is found in honey and fruits. It is also produced in our
intestines due to the digestion of carbohydrates. Glucose is the main
source of energy for our body. It has an important role in metabolic
activities in the body. Glucose is essential as well as harmful for the
organisms.

High level of glucose in the blood can result in the swelling of the
body. Similarly, the low blood glucose level is also harmful to our
body.

Learn and Write

1. Propane is a saturated hydrocarbon. Why?

A molecule of ethane contains three carbon atoms. All carbon
atoms are linked by a single bond. Therefore, propane is a
saturated hydrocarbon.

2. Alkanes are also called paraffins. Why?

Alkanes are chemically less reactive. Therefore, they are called
paraffins.

3. Methane is called marsh gas. Why?

Methane is formed naturally by the decomposition of organic
matter under water in marshy area. Therefore, it is found in
marshy area and is called marsh gas.

4. Glycerol is trihydric alcohol. Why?

Glycerol is formed by the displacement of 3 hydrogen atoms of
propane by 3OH radicals one form each carbon atom. Due to
the presence of 3OH radicals, glycerol is called trihydric alcohol.

H HH H HH

–3H HC C C H

H C C C H +3OH– OH OH OH
H HH
Glycerol
Propane

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Main points to remember

1. The compounds which are formed by the chemical combination
of carbon and hydrogen are called hydrocarbons.

2. The hydrocarbons and their derivatives are called organic compounds.
3. The branch of chemistry which deals with the hydrocarbons

and their derivatives is called organic chemistry.
4. The hydrocarbons in which the adjacent carbon atoms are linked

by a single covalent bond are called saturated hydrocarbons.
5. The hydrocarbons in which the adjacent carbon atoms are

linked by multiple (double or triple) covalent bonds are called
unsaturated hydrocarbons.
6. An atom or a group of atoms bonded to a carbon atom which
determines the chemical properties of an organic compound is
called functional group.
7. A group of atoms or a radical derived from alkanes by removing
one hydrogen atom is called alkyl group or alkyl radical.
8. A series of organic compounds having same functional group
and two successive members differing by a - CH2 unit is called
homologous series.
9. The organic compounds having same molecular formula but
different structural formula are called isomers.
10. A group of organic compounds which contain hydroxyl group (–OH)
as the functional group is called alcohol.
11. Glucose is a white crystalline powder with sweet taste. It is also
known as dextrose and is an instant source of energy.

Exercise

A. Choose the best alternative.

1. The property of carbon to form cavalent bonds with its own
atoms is called

a. Catenation b. Hydration

c. Hydrocarbon d. Organic chemistry

2. Which of the following is an unsaturated hydrocarbon?

a. C2H4 b. C2H6 c. C3H8 d. C5H12
3. Acetylene

a.C2H4 b. C2H2 c. CH4 d. C2H6

235 Times' Crucial Science Book - 10

4. The group of organic compounds which contains hydroxyl

(−OH) group

a. Alkane b. Ether c. Glycerol d. Alcohol

5. Which of the following is a dihydric alcohol?

a. Ethylene glycol b. Glycerol

c. Ethyl alcohol d. None of these

B. Answer these questions in brief.
1. What are hydrocarbons? Give examples.
2. Define saturated and unsaturated hydrocarbons with two
examples of each.
3. Write down the structural formula of butane and heptane.
4. Write down the structural formula of ethylene and acetylene.
5. What are paraffins? Give examples.
6. Define olefins with examples.
7. What is meant by homologous series? Give an example.
8. What is a functional group? Give any four examples.
9. What do you mean by alkyl group?
10. What is hydroxyl radical? Write down the structural formula of
glycerol.
11. Write down the structural formula of ether. Also state its two uses.
12. What are isomers? Give an example. Do the isomers have same
properties?
13. Write down structural formula of ethyl alcohol. Also state it's any
three uses.
14. What is methanol? Write down its structural formula and two uses.
15. Write down the general formula that represents alkanes.
16. Define alkyne with examples.
17. Name the organic gas which is used to fill lighter.
18. What are the main constituents of LPG? Write their structural
formula.

C. Give reasons.
1. Methane is also known as marsh gas.

2. Methyl alcohol is not used for drinking purpose.

3. Ethanol is used for drinking purpose,

4. Methanol is used as fuel in spirit lamp.

5. Ethylene glycol is a dihydric alcohol.

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D. Write down differences between:
1. Organic and Inorganic compounds
2. Saturated and Unsaturated hydrocarbons
3. Ethylene glycol and Glycerol.
4. Monohydric and Dihydric alcohol.

E. Conceptual questions.
1. (i) Name the compound whose structural formula is given
below.

HHH

HC C C H

HHH

(ii) Which compound is formed if one hydrogen from each
carbon atom is replaced by OH group?

(iii) Write any two uses of the compound thus formed.

2. Write down the name and three uses of the compound whose
structural formula is given below:

H H OH H H

CH2OH C C C C C
OH OH H OH O

3. Write down the name and uses of following compounds:

HHHH HH

i. H C C C C H ii. H C C OH

HHHH HH

Project Work

Consult books in a library and prepare the homologous series (Writing at
least ten members) of the following compounds:

a. Alkanes b. Alkenes c. Alkynes d. Alcohol
e. Ether f. Aldehydes g. Ketones h.Carboxylic acids

237 Times' Crucial Science Book - 10

13ChapterMaterials Used

in daily Life
Joseph Aspdin
Joseph Aspdin was an English
cement manufacturer who obtained
the patent for Portland cement on 21
OctoEbesrti1m8a2t4ed Periods: 10 (8T+2P)

Objectives

At the end of the lesson, students will be able to:

• explain the composition and uses of cement, glass, fibre, ceramics,
plastics, soap, detergent and insecticides;

• explain the types and uses of nitrogen, phosphorus and potassium
fertilizers;

• explain importance of compost manure in agriculture;
• explain chemical pollution, their effects and control measures.

Applied chemistry is the branch of chemistry which applies physical
and chemical processes for the transformation of raw materials into
the useful products. The industries include cement industry, glass
industry, fertilizer production industry, plastics industry, pulp and
paper industry, soap and detergent industry, etc. The industrial
chemistry enables human beings to experience the benefits of
chemistry when we apply it in the production of useful products. When
we apply chemistry in the transformation of materials and energy
to make usable products, this results in growth of food production,
improvement in health and hygiene, shelter and clothing.
In this chapter, we shall discuss about some industrial products such
as cement, glass, ceramics, plastics, fibres, fertilizers, etc.

Cement

Cement is a mixture of calcium silicate and calcium aluminate in the
form of fine grey powder, which binds sand, gravel and bricks when
treated with water and dried for some time.

Manufacture of cement

Cement is manufactured by heating a mixture of limestone and a special
type of clay which consists of oxides of aluminium and silicon (Al2O3.
SiO2) in the ratio of 2:1 by mass at the temperature of about 16000C.

Times' Crucial Science Book - 10 238

1. Raw materials required

Limestone (CaCO3): Two-thirds of total mass
Clay containing alumina and silica (Al2O3.SiO2): One-third of
total mass

Gypsum (CaSO4.2H2O ): About 2-3% of total mass.
2. Steps involved

The process of manufacture of cement involves three principal
steps:
a. Crushing and grinding
b. Strong heating (burning)
c. Final grinding (powdering)

Crushing and grinding

The raw materials, i.e., limestone and clay are crushed separately.
Then two-third part of crushed limestone and one third part of clay
containing alumina and silica are mixed and ground into fine power.
The powdered material is mixed with water during grinding to make
a soapy mixture called slurry.

Strong heating

The cement is then History of Cement Production
passed through tall

rotatory kiln, which England: 1825

has a temperature Germany: 1855

of about 1400°C to Belgium: 1855

1600°C. A kiln is a USA: 1872

cylindrical furnace India: 1904

which is made of steel Nepal: 1976 (Hetauda Cement Factory)

and lined with fire

bricks. The slurry

materials undergo

chemical change while passing downwards from the top of the kiln

due to high temperature of the kiln.

At the high temperature, limestone decomposes into calcium oxide
and carbon dioxide. Calcium oxide combines with alumina (Al2O3)
and silica (SiO2) to form calcium aluminate and calcium silicate
respectively. The mixture of calcium aluminate and calcium silicate
takes the form of small balls called cement clinker. The cement

239 Times' Crucial Science Book - 10

clinker is the mixture of calcium aluminate and calcium silicate in
the form of small reddish balls.

Final grinding

The cement clinker is cooled and mixed with 2-3% of gypsum
(CaSO4.2H2O). The mixture is then crushed into fine powder. Thus
produced fine powder is called cement. Gypsum increases the setting
time of the cement. It increases the quality of cement.

3. Handling and storage of cement

We should not store cement in damp or moist place because it easily
absorbs water and gets hardened itself inside the sack. Thus, it
becomes useless. The cement should also be protected from rainwater
during transportation.

Cement products

Mortar: The mixture made by blending fine sand and water with
cement is called mortar. It is used to construct and plaster the walls.
Concrete: The uniform mixture of sand, gravel, cement and water
is known as concrete. It is used in flooring and roofing of buildings.
Reinforced cement concrete (RCC): The concrete having an iron
framework inside it is called reinforced cement concrete.

Uses of cement
a. Mortar is used to construct walls of buildings because it holds the
bricks, stones, etc together. It is also used for plastering the walls.
b. Cement is used for the construction of buildings, roads, bridges, dams etc.
c. Concrete is used for flooring and roofing of buildings. It is also used
for making pillars.
d. Reinforced cement concrete is used for making roofs and pillars.

Cement factories of Nepal
There are several cement factories in Nepal such as Hetauda cement
factory (Makwanpur), Udaypur cement factory (Udaypur), Triveni
cement factory (Bharatpur), etc.

Glass

An amorphous, hard, transparent and homogeneous mixture of
silicates of different metals is called glass. It is considered as super
cooled liquid. Chemically it is the silicate of metals. The main raw
material required for the production of glass is silica (Silicon dioxide,
SiO2 )and is the main source of silica. It is also found in quartz. Silica

Times' Crucial Science Book - 10 240

and compounds of certain metals react to form silicates.

Characteristics of glass
1. Glass is a hard, transparent, amorphous and homogeneous
mixture of metallic silicates.
2. It does not have fixed composition and particular formula.
3. It does not have fixed melting point.
4. Glass is a super cooled liquid because molecules of glass flow
very slowly like the molecules oil liquid.

Therefore, windowpanes of old house are thicker at the lower parts.

Types of glass

The properties of glass depend upon the proportion of components
added to silica during their production. Some important types of
glass are given below:

1. Quartz glass

It is a pure crystalline glass. It is prepared by heating silica to
about 1600°C and then cooling the product.

Pure silica (SiO2) 1600°C → Quartz glass
Characteristics

a. It is very hard.
b. It is not affected by water and acids.
c. It remains unaffected even at high temperature. Even red

hot quartz glass when placed in cold water does not crack.

Uses
a. It is used in making electrical devices.
b. It is also used in making coloured quartz (gems).
c. It is used for making different types of laboratory appliances
such as crucible, basin, etc.

2. Water glass
The glass made of sodium silicate or potassium silicate is called
water glass. It is produced by heating silica with sodium carbonate
or potassium carbonate at about 800°C. Since this glass is soluble in
water, it is known as water glass.

SiO2 + Na2CO3 800°C → Na2SiO3 + CO2

Sodium silicate

SiO2 + K2CO3 800°C → K2SiO3 + CO2

Potassium silicate

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Characteristics
It is not affected by fire but is soluble in water.

Uses It is used for making fireproof materials.
a. Solution of water glass is used for making gums, pastes and
b. adhesives.
It is used for making silica garden.
c.

3. Ordinary glass (Soft glass or soda lime glass)

The fused homogeneous mixture of sodium silicate and calcium
silicate is called ordinary glass. It is obtained by heating the mixture
of 50% silica, 25% pieces of glass, 15% sodium carbonate and 10%
calcium carbonate at about 1500°C.

2SiO2 + Na2CO3 + CaCO3 + glass pieces 1500°C → Na2SiO3.CaSiO3 + 2CO2

(50%) (15%) (10%) (25%) (Sodium silicate and calcium silicate)

Ordinary glass

During the manufacture of ordinary glass, limestone is added to make
glass insoluble in water. The broken glass pieces help in melting of
the mixture. Then the glass articles are made using the molten mass.
The articles are then cooled slowly. The process of slow cooling of
prepared glass articles is called annealing.

If lead monoxide is added during manufacture of ordinary glass, it
reacts with silica to form lead silicate glass. Lead monoxide increases
the refractive index of glass and decreases the transparency. So, it is
used for making prism, lens, glass slab, etc.

Characteristics

It is insoluble in water. Ordinary glass melts at low temperature and
hence it is called soft glass.

Uses

It is used in the manufacture of simple bottles, light bulbs,
windowpanes, glass sheets, glass tubes, etc.

4. Hard glass

The glass prepared from the fused homogeneous mixture of potassium
silicate and calcium silicate is called hard glass. The hard glass is
prepared by heating the mixture of silica, potassium carbonate and
calcium carbonate at high temperature. The hard glass is also called

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potash lime glass.

2SiO2 + K2CO3 + CaCO3 ∆ → K2SiO3.CaSiO3 + 2CO2

Potassium silicate and calcium silicate

Characteristics
a. It melts at very high temperature.
b. It is hard and strong glass.

Uses

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

Differences between soft glass and hard glass

Soft glass Hard glass

1. It is the mixture of sodium 1. It is the mixture of potassium

silicate and calcium silicate. silicate and calcium silicate.

2. It melts at low temperature. 2. It melts at high temperature.

3. It is prepared by heating the 3. It is prepared by heating the

mixture of silica, calcium mixture of silica, calcium

carbonate, sodium carbonate carbonate and potassium

and pieces of glass. carbonate.

5. Borosilicate glass (Pyrex glass)

The homogeneous mixture of sodium silicate, calcium silicate and
boron silicate is called borosilicate glass. It is also known as pyrex
glass. The borosilicate glass is produced by heating the mixture of
sodium carbonate, calcium carbonate, silica and boric oxide at high
temperature.

5SiO2 + Na2CO3 + CaCO3 + B2O3 ∆ → Na2SiO3.CaSiO3.B2(SiO3)3 + 2CO2

Borosilicate glass
(Sodium silicate, Calcium silicate and Boron silicate)

Characteristics
a. It is resistant to chemicals and heat.
b. The presence of boron silicate makes it very hard.

Uses
High temperature resistant apparatus are made from borosilicate
glass. The apparatus include test tubes, flasks, beakers, condensers

243 Times' Crucial Science Book - 10

and kitchen wares.
6. Lead crystal glass
The glass obtained by melting the homogeneous mixture of potassium
silicate and lead silicate is called lead crystal glass. It is obtained by
heating the mixture of silica, potassium carbonate and lead monoxide
at high temperature. It is also known as flute glass.

2SiO2 + K2CO3 + PbO ∆ → K2SiO3.Pb SiO3 + CO2

Potassium silicate and lead silicate
(Lead crystal glass)

Characteristics
a. It has high refractive index.
b. It is hard and insoluble in water, acid, alkali, etc,

Uses

It has high refractive index. So, it is used for making lens, prisms,
electric bulbs, etc.

7. Coloured glass

The glasses of different colours are prepared by adding different
metallic oxides to the mixture of raw materials of the ordinary glass.

Sn Metallic oxide used Colour of the prepared glass
1. Cobalt oxide Blue
2. Nickel oxide Black
3. Chromium oxide Green
4. Manganese oxide Purple
5. Cuprous oxide (Cu2O) Red
6. Selenium oxide Red
7. Ferric oxide [Fe(III) oxide] Yellow or brown
8. Tin oxide Milky white

Uses

Coloured glass is used for making sunglasses, signals for automobiles,
artificial gems, etc. It is also used for decorative purposes.

Ceramics

A special type of clay containing the compounds of carbon, nitrogen,
silica and oxygen is called ceramics. The word ceramics is derived
from the Greek word 'keramos' which means potter's clay. Ceramics,

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itself is the science of pottery and is related to the production of large
number of ceramic products as ceramics industries. Chemically,
ceramics is mainly the hydrated aluminium silicate (Al2O3,
SiO2.2H2O). It may contain other substances such as magnesium
carbonate, limestone powder, iron oxide and manganese oxide. Pure
white soil used in ceramics is called kaolin, which is used to make
cups, plates, etc.

Method of making ceramic pots
a. The clay is separated from gravel and pebbles and is crushed
and grinded into very fine powder. It is then sieved.

b. The fine powder is mixed with water and is turned into
shapable paste.

c. It is given a desired shape and is dried in sunlight for some days.

d. The dried pots are then heated at high temperature in special
furnace called kiln. At high temperature, the soil hardens
due to chemical reaction and becomes porous.

e. A small amount of fine salt powder is sprayed on the ceramic
pots in the furnace when it is hot. It makes them non-porous,
smooth, water proof and shiny. This process is called glazing.

f. Colour and polish are also added in order to make the ceramics
attractive.

Characteristics of ceramics
1. They can withstand high temperature.
2. They are not affected by acid, alkali, and other chemicals.
3. They are hard, attractive and brittle.
4. Ceramics is poor conductor of heat and electricity.

Uses The ceramic cups, bowls, plates, dishes, etc are quite useful.
1. They are used to make vessels that need strong heating.
2. Glazed ceramics is used to make bathroom tiles, sinks, etc.
3. They are used for lining the inner surface of furnaces.
4. They are used to make artificial teeth.
5. Being poor conductor, it is used in electrical appliances.
6.

245 Times' Crucial Science Book - 10

Polymers and Plastics

A polymer is a very large molecule that is formed by linking a large
number of small molecules together. The starting small molecules
which are used to make polymer are called monomers. For example,
ethylene, vinyl chloride, tetrafluoroethene, etc are monomers.

The process of combination of simple monomeric molecules to form a
giant polymer is called polymerization. Generally, polymerization is
carried out in the presence of catalyst.

The properties of the polymer are quite different from those of the
monomers. For example, polythene is a polymer which is obtained
from the polymerization of ethene gas (CH2 = CH2).

n(CH2 = CH2) polymeriztion → [CH2– CH2]n

ethene Polythene

(monomer) (Polymer)

Polymers can be categorized into two types: natural polymers and
synthetic polymers.

Natural polymers: The polymers which are available in nature are
called natural polymers. Silk, wool, proteins, starch, cellulose, etc are
examples of natural polymers.

Synthetic polymers: The polymers which are produced under
artificial conditions as per human need are called synthetic polymers.
Plastic, synthetic fibres (terylene, polyester, nylon) etc are examples
of synthetic polymers.

Plastics

Plastics are synthetic polymers which are prepared by the
polymerization of organic monomers. The raw materials for most
plastics are the chemicals obtained from crude oil. Besides these,
small quantities of other substances are often added to modify their
properties. The plastic goods are widely used due to their following
properties of plastics:

a. It is light, durable and easy to carry.

c. It can be moulded into any desired shape.

b. It is cheap and is available in different shape, size and colour.

e. It is resistant to acids, alkalis and corrosion.

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