Class 10 Science Solutions Nepal

5. Aluminium hydroxide [Al(OH)3], magnesium hydroxide [Mg(OH)2], etc. are used
to reduce hyper-acidity of the stomach.

6. Ammonium hydroxide (NH4OH) is used as a laboratory reagent.

SALT

Let us observe the following chemical reactions.

HCl + NaOH NaCl + H2O

H2SO4 + NaOH NaHSO4 + H2O

In the first reaction, hydrogen of acid is replaced by metal whereas in the second

reaction only one hydrogen of sulphuric acid is replaced by metal. In both the above

reactions, the product is salt.

Salts are those chemical substances which are formed by the replacement of hydrogen of acid by
metal or ammonium radicals.

Generally salts are neutral substances but some may be acidic and some may be basic
in nature. The process by which salts are prepared by the reaction of acid with base is
called neutralization reaction.

Acid + Base Salt + Water

HCl + NaOH NaCl + H2O
H2SO4 + 2KOH K2SO4 + 2H2O

Classification of salts

We have studied that salts are the products of neutralization of acids and bases.
Therefore, we expect salts to have neutral (pH = 7). In fact, solutions of salts may be
neutral or basic or acidic depending upon the nature of the acid and base used. Some
examples of different types of salts are given below.

Salts Parent acid Parent base Nature

NaCl, K2SO4 Strong Strong Neutral
NH4Cl Strong Weak Acidic
CH3COONa, Na2CO3 Weak Strong Basic
CH3COONH4 Weak Weak Neutral

Thus, salts can be classified into neutral, acidic or basic salts depending upon their pH
value and nature of their parent acids and bases.

i) Neutral salts

Salts that are formed when a strong acid is neutralized by a strong base or weak acid by weak
base are called neutral salts. For example, sodium chloride (NaCl), sodium sulphate
(Na2SO4), potassium chloride (KCl), etc.

New Creative Science, Class 10 | 147

ii) Acidic salts

Salts that are formed when a strong acid is neutralized by a weak base are called acidic salts. For
example, ammonium chloride (NH4Cl), aluminium sulphate [Al2(SO4)3], ammonium
nitrate NH4NO3, etc.

iii) Basic salts

Salts that are formed when a weak acid is neutralized by strong base are called basic salts. For
example, sodium acetate (CH3COONa), sodium carbonate (Na2CO3), etc.

Properties of salts

1. Salts are mostly solids.
2. Salts are usually soluble in water but there are certain salts which are not soluble

in water. For example, calcium carbonate, calcium sulphate, magnesium sulphate,
silver chloride, lead chloride, etc.
3. Solution of salts conduct electricity.
4. Solutions of salts may be neutral, acidic or alkaline.
5. Some salts are amorphous whereas some are crystalline.
6. Some salts are white in colour or colourless whereas some are colourful.

Preparation of salts

Salts can be prepared in the following ways:
1. By direct combination of metals and non-metals

Metal + Non-metal Salt

2Na + Cl2 2NaCl

2Fe + 3Cl2 2FeCl3

2. By the reaction of metal with acid

Metal + Acid Salt + Hydrogen

Mg + 2HCl MgCl2 + H2

3. By the reaction of acid with base

Acid + Base Salt + Water

HCl + NaOH NaCl + H2O

HCl + KOH KCl + H2O

4. By the reaction of acid with carbonates

Acid + Carbonates Salt + water + carbon dioxide

HCl + 2CaCO3 CaCl2 + H2O + CO2

Uses of salts

1. Common salt (NaCl) is used in our food and also as preservatives.
2. Washing soda (Na2CO3 . 10H2O) is used to make glasses and chemicals for food

and drink industries.

148 | Acid, Base and Salt

3. Baking soda (NaHCO3) is used as baking powder.
4. Potash alum (phitkiri) (K2SO4 . Al2(SO4)3 . 24H2O) is used for purifying water.
5. Calcium sulphate (gypsum) (CaSO4 . 2H2O) is used in cement and to manufacture

plaster of paris.
6. Silver nitrate (AgNO3) is used for the treatment of sores and infections.
7. Iron sulphate (FeSO4 . 7H2O) is an important constituent of blue–black ink.
8. Copper sulphate (CuSO4 . 5H2O) is used as a fungicide.
9. Ammonium nitrate (NH4NO3) is used to manufacture fertilizers and explosive.

QUESTIONS
# Describe different methods of salt preparation with examples.
# Write down any five uses of salts.
# Define neutral salts, acidic salts and basic salts with examples.

NEUTRALIZATION REACTION

The chemical reaction in which an acid and a base react together to give salt and water is called
neutralization reaction. In neutralization reaction, acid loses its acidic property and
base loses its basic property. Therefore, this reaction is also called acid base rection.

Application of the neutralization reaction

i. Farmers use lime in the soil to neutralize the acidic nature of the soil.
ii. We use antacid (magnesium hydroxide) to reduce the acidity of the stomach.
iii. Formic acid enters into our body when honey bees and ants bite us. To neutralize

the effect of formic acid, we use soap.
iv. Alkalis enters into our body when some insects bite us. To neutralize the effect of

this alkalis, we use acetic acid around the wound.

INDICATORS (Note: In new curriculum of CDC, indicator is not in syllabus.)

Indicators are those chemical substances which help to indicate whether the given substance is
acid or base or neutral by changing its own colour.

Indicators indicate the nature of substances by changing their own colour when they
come in contact with those substances. Indicators do not take part in the chemical
reaction but they show the end point by changing colour. The common indicators are
litmus paper, methyl orange, phenolphthalein etc. The change of colours of common
indicators in acid, base and salt is given below:

New Creative Science, Class 10 | 149

S.N. Indicators Colour in acid Colour in basic Colour in salt
1. Red litmus paper
2. Blue litmus paper solution solution solution
3. Methyl orange
4. Phenolphthalein No change in Changes into blue No change in

colour colour colour

Changes into red No change in No change in

colour colour colour

Changes into red Changes into yellow No change in

colour colour colour

No change in Changes into pink No change in

colour colour colour

Ordinary Indicators

Those indicators which indicate only whether the given substance is acid or base or salt are
called ordinary indicators.

Litmus paper, methyl orange, phenolphthalein are some examples of ordinary
indicators. They are obtained from the parts of plants like flowers, roots, leaves, etc.

Universal Indicators

Those indicators which indicate whether the given substance is acid or base or salt with their
strength are called universal indicators.

They are obtained by mixing two or more ordinary indicators. Universal indicators
change their colour and it is matched with the colour in pH chart to determine the
strength of solution.

Differences between ordinary and universal indicators.

Ordinary indicators Universal indicators

1. They only indicate whether the given 1. They indicate whether the given

substance is acid, base or salt. substance is acid, base or salt with

their strength.

2. They are obtained from the parts of 2. They are obtained by mixing many
plants like leaves, flowers and roots, ordinary indicators, e.g. pH paper.
e.g. litmus paper, methyl orange,
phenolphthalein.

pH

The measure of hydrogen ions concentration in the given solution is called pH.

The solution which has more hydrogen ions concentration will have low a pH value
whereas the solution which has less hydrogen ions concentration will have more pH
value. More hydrogen ions concentration indicates acid solution and low hydrogen
ions concentration indicates base solution.

150 | Acid, Base and Salt

pH scale

The standard scale which is used to measure the hydrogen ions concentration in the solution
is called pH scale.

It ranges from one to fourteen. The middle point of this scale (i.e. 7) indicates the
neutral solution. The points below 7 indicate acid solution and the points above 7
indicate basic solution. One is the strongest acid and fourteen is the strongest base.
In different pH values, there is a different colour. Green colour indicates neutral, red
colour indicates acid and blue colour indicates base.

pH 1 2 34 56 7 89 10 11 12 13 14

Red colour Pink Yellow Green Greenish Light Blue Deep blue
for (Strong colour colour colour Blue colour Blue colour colour Colour for
Acid) for (Strong base)
Neutral

pH meter

The man-made scientific instrument which is used to measure the pH value of the given
solution directly in the number is called pH meter.

In the pH meter, there is a box, rod and wire. In the box, there are different readings.
This box is connected to the rod with the help of a wire. The rod is dipped into the
solution whose pH value is to be measured.

pH
rod

solution

pH value of some substances pH
1
S.N. Compounds 1.2
1. Hydrochloric acid (HCl) 2.5
2. Sulphuric acid (H2SO4) 3
3. Lemon juice 6
4. Juice of apple, vinegar and carbonic acid 7
5. Butter 7.3
6. Ethanol, water, salt and, sugar solution, 8.5
7. Blood of human body 10
8. Baking soda 11.5
9. Ammonium hydroxide (NH4OH) 13
10. Sodium carbonate or washing soda (Na2CO3)
11. Caustic soda or sodium hydroxide (NaOH)

New Creative Science, Class 10 | 151

MODEL QUESTIONS ANSWER

1. How do you measure the pH value of the soil? Describe it in brief.

Ü To measure the pH value of the soil, take an amount of soil as a sample and keep
it into the test-tube containing water. Then shake it well for some time and allow
it for sedimentation. Filter the solution by using a filter paper. Now add a few
drops of universal indicator in the filtrate. The colour obtained is matched with
the colour of pH paper and thus I find out the pH value of the given sample.

2. How do you know that the given acid is weak or strong?

Ü Strong acid undergoes almost complete ionization and gives more concentration
of hydrogen ions. Hence, it is more corrosive and is a good conductor of electricity
in comparison to the weak acid.

3. Organic acids are weak acids. Justify this statement.

Ü Generally organic acids are obtained from living organisms and they undergo
much less ionization in the aqueous solution to give hydrogen ions. Hence, they
are weak acids and a poor conductor of electricity.

4. Hydrochloric acid (HCl) is secreted from the stomach of the animals even it is
inorganic acid. Why?

Ü Hydrochloric acid is also obtained from living organisms but it has no carbon
atom. Hence, it is an inorganic acid.

EXERCISE

1. Define the following terms with examples:

(a) Acid (b) Base (c) Salt (d) Alkalis

(e) pH (f) pH scale (g) Indicators

2. Write two differences between:

(a) acid and base

(b) organic and inorganic acids

(c) ordinary and universal indicators

(d) Bases and alkalis

(e) Strong and weak acids

3. Give reason.

(a) All alkalis are base but all bases are not alkalis.

(b) Ammonium chloride is an acidic salt.

(c) Sodium hydroxide is a strong base.

4. Define acids. Write down any four examples of acids.

5. Write any four characteristics of acids.

6. Write down any four uses of acids.

152 | Acid, Base and Salt

7. Define base with some examples.
8. Write down any three methods of base preparation with a chemical equation.
9. What are alkalis? Why is it said that all alkalis are base?
10. What do you understand by neutralization reaction? Describe it with examples.
11. Write down any five uses of base.
12. Define salt. Describe in brief the acidic and basic salts with examples.
13. Write any five uses of salts.
14. What are indicators? How are ordinary indicators prepared? Describe them in

short.
15. What is the main difference between ordinary and universal indicators?
16. What are pH, pH scale and pH meter?
17. How do you measure the pH value of soil? Describe it in brief.
18. Complete the given equations and balance them.

(a) HCl + NaOH
(b) NH4OH + HCl
(c) Al2O3 + H2O
(d) NaOH + H2SO4
(e) CuO + H2SO4
19. Complete the table.

Indicators Acid Colour Change Salt
Base
Red litmus paper
Blue litmus paper
Methyl orange
Phenolphthalein

A

B GLOSSARY
C

Various : several different
Aqueous : containing water
Corrosive : tending to destroy sth by chemical action

Concentration : a lot of something in one place (no. of molecules present per unit volume of solution)



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UNIT

10 Some Gases

About the Scientist Ammonia p=1
n=0
Antoine-Laurent de Lavoisier Molecular formula : NH3
(1743 – 1794) Molecular weight : 17 p=7
n=7
Born to a wealthy family in Nature: Basic
Paris, Antoine Laurent Lavoisier p=1
inherited a large fortune at the n=0
age of five with the passing of his
mother. He attended the College INTRODUCTION p=1
Mazarin in 1754 to 1761, n=0
studying chemistry, botany,
astronomy, and mathematics. Ammonia is a compound gas which has one nitrogen atom
His education was filled with the and three hydrogen atoms. They are bonded together by
ideals of the French. covalent bonding. Lavoisier first prepared ammonia gas by
heating ammonium chloride and calcium hydroxide and its
Lavoisier also demonstrated the chemical composition was studied by Barthecol and Davy.
role of oxygen in the rusting of
metal, as well as oxygen’s role Ammonia is a lighter gas. Amount of this gas is present in
in animal and plant respiration. air, soil and rainwater. Since it is highly soluble in water,
Working with Pierre-Simon atmospheric ammonia is converted into ammonium
Laplace, Lavoisier conducted hydroxide when it comes in contact with water. In
experiments that showed that combined state, it is present in different types of nitrogenous
respiration was essentially a slow compounds like ammonium chloride, ammonium sulphate,
combustion of organic material ammonium phosphate, etc.
using inhaled oxygen. Lavoisier’s
explanation of combustion General methods of preparation of ammonia gas
disproved the phlogiston theory,
which postulated that materials 1. By heating ammonium salts
released a substance called
phlogiston when they burned. Ammonium salts like ammonium chloride, ammonium

sulphate, ammonium carbonate, etc. give ammonia gas

after heating.

(NH4)2 CO3 ∆ 2NH3 ↑ + CO2 + H2O

(Ammonium carbonate) (Ammonia)

(NH4)2 SO4 ∆ 2NH3 + H2SO4

(Ammonium sulphate)

2. By heating ammonium salts with strong base

When ammonium salts like ammonium chloride, ammonium
sulphate, ammonium carbonate, etc. react with strong base
like sodium hydroxide, potassium hydroxide, etc then they
give ammonia gas.

154 | Some Gases

NH4Cl + KOH ∆ KCl + H2O + NH3 ↑

(NH4)2 SO4 + 2KOH Na2SO4 + 2H2O + 2NH3↑

Laboratory preparation of ammonia gas

Principle

In the laboratory, ammonia gas can be prepared by heating a mixture of ammonium
chloride and calcium hydroxide in the ratio of 2 : 1.

2NH4Cl + Ca(OH)2 CaCl2 + 2H2O + 2NH3 ↑

Apparatus required ii) Delivery tube iii) Gas Jar
i) Hard glass test tube
iv) Bunsen burner v) Stand vi) Red litmus paper

Chemicals required
i) Ammonium chloride – NH4Cl
ii) Calcium hydroxide – Ca (OH)2

Ammonia gas

Gas jar

Burner

Delivery tube Red litmus paper

Laboratory preparation of Ammonia Gas

Procedure

The mixture of ammonium chloride and calcium hydroxide is prepared in the ratio
of 2: 1 and kept within a hard glass test tube. All the apparatus as are arranged
according to the given figure. Heat is supplied with the help of Bunsen burner. When
both chemicals react together, they produce ammonia gas which is passed through the
delivery tube and collected in the gas jar by downward displacement of the air.

Precautions
1. The apparatus should be made airtight.
2. The hard glass test tube should be slightly inclined towards its mouth.
3. Ammonia gas is collected by the downward displacement of air.
4. Uniform heat should be supplied.

New Creative Science, Class 10 | 155

Test of ammonia gas
1. Ammonia is a basic gas so it turns moist red litmus paper into blue colour.

2. It forms white fumes of ammonium chloride (NH4Cl) when the glass rod
dipped in hydrochloric acid (HCl) is brought in contact with this gas.

3. We can identify ammonia gas due to its pungent smell.

Manufacture of ammonia gas

For commercial use, ammonia gas is manufactured in a large scale by using Heber’s

process. In this process, 3 : 1 ratio of hydrogen and nitrogen is heated strongly at about

500°C temperature and under 200 to 600 atmospheric pressure in the presence of iron

catalyst and molybdenum promoter.

N2 + 3H2 Fe (catalyst), Mo(Promoter) 2NH3
500°C, 200-600 atm

Conditions required for Heber’s process

1. 500°C temperature and 200-600 atmospheric pressure should be maintained.

2. Powdered iron as a catalyst and molybdenum as a promoter should be used.

3. High concentration of nitrogen and hydrogen should be used.

Properties of ammonia gas

A) Physical properties
1. It is a colourless gas with a pungent smell.
2. It is basic in nature so it turns red litmus paper into blue.
3. It is lighter than air.
4. It is highly soluble in water to give ammonium hydroxide.

B) Chemical properties

1. Reaction with water: Ammonia is highly soluble in water to give ammonium

hydroxide. The resultant solution of ammonium hydroxide is basic in nature.

NH3 + H2O NH4OH (Ammonium hydroxide)
Ammonium hydroxide reacts with acid to give salt and water. For example,

ammonium hydroxide reacts with hydrochloric acid to give ammonium chloride

and water.

NH4OH + HCl NH4Cl + H2O
2. Reaction with acids: Since, ammonia is a basic gas so it reacts with acids to give

salt. For example, ammonia gives ammonium chloride with hydrochloric acid

and ammonium sulphate with sulphuric acid.

NH3 + HCl NH4Cl

2NH3 + H2SO4 (NH4)2SO4

3. Reaction with carbon dioxide (CO2): ammonia reacts with carbon dioxide to
give urea.

2NH3 + CO2 1500°C NH2CONH2 + H2O

Urea

156 | Some Gases

4. Combustibility: Ammonia is a non-combustible gas and it does not support in
combustion but it burns in oxygen to give nitrogen and water.

4NH3 + 3O2 2N2 + 6H2O

Uses of ammonia gas

1. Ammonia is used in the manufacturing of nitrogenous fertilizers like urea,
ammonium phosphate, ammonium sulphate, etc.

2. Liquid ammonia is used as a cooling agent in the refrigerator.
3. It is used in manufacturing nitric acid, washing soda, plastics, etc.
4. It is used as a cleaning agent to remove oil, grease, fat, etc.
5. It is used to develop blue prints of a map.

ACTIVITY

Objective: To show that ammonia is highly soluble in water and Ammonia with

basic in nature. water

Materials required: round bottom flask, water trough, stand,

phenolphthalein, etc.

Procedure: We take a round bottom flask

containing ammonia gas and fit it with a delivery

tube. The lower end of the delivery tube is within the Stand
water trough with a few drops of phenolphthalein.
Water
The delivery tube carries a jet inside the round

bottom flask. Now, ammonia gas cools down inside Fountain Experiment
the round bottom flask creating low pressure.

Due to difference in the pressure of the round bottom flask and water trough, the water rises in the flask

and forms ammonium hydroxide that is basic in nature. At this time, more vacuum is created inside the

round bottom flask. Hence, water rushes up with high pressure to fill the vacuum, which appears like a

fountain. Now the whole flask becomes pink.

Conclusion: The above activity proves that ammonia is highly soluble in water and basic in nature.

MODEL QUESTIONS ANSWER

1. Why do you take moist red litmus paper near the mouth of the gas jar during
the preparation of ammonia?

Ü We take moist red litmus paper near the mouth of the gas jar to test whether the
gas jar is filled with ammonia gas or not. We know that ammonia is a basic gas.
When it comes in contact with water, it gives ammonium hydroxide (NH4OH)
so it turns the red colour of litmus paper into blue.

2. Why do we collect the ammonia gas in the inverted gas jar?

Ü Ammonia is lighter than air, so it is collected in the inverted gas jar displacing
the air downward.

New Creative Science, Class 10 | 157

3. Sometimes, we use a lime tower (CaO) during the preparation of ammonia gas.
Why?

Ü Lime or calcium oxide (CaO) absorbs the moisture of ammonia gas. As a result,
we get pure ammonia gas.

4. We should make the hard glass test tube slightly inclined during laboratory
preparation of ammonia gas. Why?

Ü When ammonium chloride and calcium hydroxide react together, they give
water as one of the products. This water is liquefied and collected at the bottom
of the test tube and may cause the cracking. So, to protect it from the cracking of
hard glass test tube it should be slanted.

5. What will happen when kerosene is kept in place of water during the fountain
experiment?

Ü Because kerosene does not form the ammonium hydroxide with ammonia and
so it does not give the pink coloured fountain.

EXERCISE

1. Write down the principle of the laboratory preparation of ammonia gas with a
balanced chemical equation and draw a well-labeled diagram of the apparatus
arrangement.

2. Write any three physical and three chemical properties of ammonia gas.
3. What is Heber’s process of the industrial preparation of ammonia gas? Describe

it in brief.
4. What are the uses of ammonia gas? Write down any four.
5. What happens when? Give balanced chemical equation:

(a) Ammonia reacts with carbon dioxide.
(b) Ammonia reacts with water.
(c) Ammonia reacts with sulphuric acid.
(d) Ammonia reacts with nitric acid.
6. Give reasons.
(a) Moist and red litmus paper is taken near the mouth of the gas jar.
(b) Ammonia gas does not pass through water.
(c) Ammonia gas is collected in the inverted gas jar.
(d) Ammonia is a compound gas.

158 | Some Gases

Carbon dioxide p=8 p=6 p=8
Molecular formula: CO2 n=8 n=6 n=8
Molecular weight: 44
Nature: Acidic

INTRODUCTION

Carbon dioxide is a compound gas which has one carbon atom and two oxygen atoms
bonded together by covalent bond. It is present free as well as in combined state in
the nature. 0.03 percentages of carbon dioxide is present in the atmosphere. It comes
in the atmosphere due to burning of fuel, respiration by organisms, volcanic eruption,
etc. In combined state, it is present in carbonates, bicarbonates, etc. Carbon dioxide is
an important gas for photosynthesis.

General methods of preparation of carbon dioxide

1. By the combustion of carbon containing compounds
Carbon dioxide is obtained by the combustion of carbonic compounds like methane,

ethane, carbohydrates, etc.

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

2. By the reaction of acid with carbonates and bicarbonates
Acids react with carbonates and bicarbonate of different types of metals to give carbon

dioxide.

CaCO3 + 2HCl CaCl2 + H2O + CO2
Ca(HCO3)2 + 2HCl CaCl2 + 2H2O + 2CO2

Laboratory preparation of carbon dioxide gas

Principle

In the laboratory, carbon dioxide gas can be prepared by the reaction of dilute
hydrochloric acid with calcium carbonate (or marble or limestone).

CaCO3 + 2HCl ii. CaCl2 + H2O + CO2 iv. Delivery tube
Thistle funnel iii. Gas Jar
Apparatus required
i. Woulfe’s bottle

Chemicals required

i. Calcium carbonate or limestone or marble (CaCO3)
ii. Dilute hydrochloric acid (dil. HCl)

New Creative Science, Class 10 | 159

Thistle funnel
Dilute Hydrochloric acid

Delivery tube

Woulfe’s bottle

Gas jar

Carbon dioxide

Calcium carbonate (marble chips)

Laboratory preparation of carbon dioxide gas

Procedure

Take a Woulfe’s bottle and keep some pieces of marble in it and arrange all the
apparatuses as shown in the diagram. Pour dilute hydrochloric acid with the help of
a thistle funnel until it covers the marble pieces and lower end of the thistle funnel.
Now, the chemical reaction occurs between the marble and acid producing carbon
dioxide gas. This gas is collected in the gas jar by the upward displacement of air,
passing through the delivery tube.

Test of Carbon dioxide gas

1. We take a burning matchstick near the mouth of the gas jar. If the burning matchstick

extinguishes, it conforms that the gas jar contains the carbon dioxide gas.

2. Carbon dioxide is an acidic gas, so it turns blue colour of litmus paper into red.

3. Carbon dioxide turns lime-water into milky white colour when it is passed

through it. The milky white colour is due to the formation of insoluble calcium

carbonate (CaCO3). CaCO3 ↓+ H2O
CO2 + Ca(OH)2
(Calcium carbonate)

When carbon dioxide is allowed to pass for a long time then it produces soluble

calcium bicarbonate. As a result of this, milky white colour disappears.

CaCO3 + H2O + CO2 Ca(HCO3)2 (Calcium bicarbonate)

Precautions

1. Woulfe’s bottle should be airtight.

2. Carbon dioxide should be collected by the upward displacement of air.

3. The end of the thistle funnel should be dipped in the solution.

4. The end of the delivery tube should not touched the solution.

Manufacture of carbon dioxide gas

Carbon dioxide is manufactured by heating calcium carbonate (or limestone or

marble). As a result, quick lime (or calcium oxide) is also produced.

CaCO3 ∆ CaO + CO2

160 | Some Gases

Properties of carbon dioxide gas

A) Physical properties
1. Carbon dioxide is a colourless, odourless and tasteless gas.

2. It is soluble in water to produce carbonic acid (H2CO3).
3. It is acidic in nature. So, it turns blue litmus paper into red.

4. It is a heavier gas.

5. It is a non-combustible gas and also does not support in the combustion.

Dry ice

When carbon dioxide is cooled down below –78°C, it converts into solid form which is known
as dry ice. Dry ice melts without wetting the papers, cloths, etc. It is used in the
refrigerators as a cooling agent.

B) Chemical properties

1. Reaction with water: Carbon dioxide gives carbonic acid (H2CO3) when it is
dissolved in water.

CO2 + H2O H2CO3 (Carbonic acid)
2. Reaction with ammonia: Carbon dioxide reacts with ammonia to give urea,

which is used as a fertilizer.
CO2 + 2NH3 1500°C NH2 – CO – NH2 + H2O
3. Reaction with magnesium: Carbon dioxide reacts with magnesium to produce

magnesium oxide and carbon.
CO2 + 2Mg ∆ 2MgO + C↓

(Magnesium oxide) (Carbon)

4. Reaction with alkali: Carbon dioxide reacts with alkali solution of sodium

hydroxide to give sodium carbonate and water.

CO2 + 2NaOH Na2CO3 + H2O
5. Reaction with limewater: Carbon dioxide reacts with limewater to produce

insoluble calcium carbonate.

CO2 + Ca(OH)2 CaCO3 ↓+ H2O
If more amount of carbon dioxide is passed through this solution, soluble calcium

bicarbonate is obtained.

CaCO3 + H2O + CO2 Ca(HCO3)2

Calcium bicarbonate

6. By photochemical reaction: Green plants use carbon dioxide gas in the presence

of sunlight and water to produce carbohydrate (glucose).
light
6CO2 + 6H2O Chlorophyll C6H12O6 + 6O2

(Glucose)

Uses

1. It is used as a fire extinguisher.

2. Solid form of carbon dioxide (i.e. dry ice) is used as a cooling agent in the

refrigerator.

3. It is used in aerated drinks like soda water, coca cola, beer, etc.

4. It is used to manufacture urea.

New Creative Science, Class 10 | 161

5. Green plants use carbon dioxide for photosynthesis process.
6. It is used to purify sugarcane juice.

FIRE EXTINGUISHER

A fire extinguisher has a metallic cylinder which Knob

contains two sections. The inner most section is Nozzle for gas

made up of a glass bottle containing concentrated Wire gauze

sulphuric acid and the outer section is made by Concentrated H2SO4

a metallic cover. Outside the glass vessel, there

is saturated solution of sodium bicarbonate. At

the top of the glass vessel, there is a knob. When Saturated sodium
this knob is pressed inside, the vessel breaks and bMiceatrablolincactyelinder
sulphuric acid comes out. Now, this acid reacts

with sodium bicarbonate producing carbon

dioxide gas. This produced carbon dioxide is sprayed over fire.

2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2

MODEL QUESTIONS ANSWER

1. Why do we collect carbon dioxide gas by the upward displacement of air?
Ü Carbon dioxide is a heavier gas. So, it is collected down to the gas jar by the

upward displacement of air.

2. Why does carbon dioxide extinguish fire?
Ü Carbon dioxide covers the burning flame making itself just like a blanket. As a

result of this, it does not allow oxygen gas to enter and finally puts out the fire.

3. We do not use dilute sulphuric acid in place of dilute hydrochloric acid during
the laboratory preparation of carbon dioxide. Why?

Ü Dilute sulphuric acid forms calcium sulphate when it reacts with calcium
carbonate. This calcium sulphate is insoluble and remains as an outer layer over
the marble chips which covers the remaining part of marble and does not allow
further reaction. Hence, we do not use dilute sulphuric acid in place of dilute
hydrochloric acid.

4. Carbon dioxide is not collected in the gas jar passing it through water. Why?
Ü Carbon dioxide is slightly soluble in water to give carbonic acid. So, we do not

collect it by passing it through water.

5. Give a suitable reason why bubbles come out when we open a soda water
bottle.

Ü During the manufacturing of soda water, CO2 is dissolved at a high pressure. As
we open the lid of the bottle, pressure decreases and excess CO2 comes out in the
form of bubbles.

162 | Some Gases

EXERCISE

1. Write the principle of the laboratory preparation of carbon dioxide gas with a
balanced chemical equation and draw a well-labeled diagram.

2. Write any two physical properties, two chemical properties and two uses of
carbon dioxide gas.

3. How do you test the carbon dioxide gas? Explain any two methods in brief.

4. Describe the working mechanism of the fire extinguisher in brief.

5. How is carbon dioxide manufactured in a commercial scale? Explain briefly.

6. Write any four chemical properties of CO2 with a balanced chemical equation.
7. Write any four uses of carbon dioxide gas.

8. Write the precautions needed during the laboratory preparation of CO2.
9. Draw the molecular structure of CO2.
10. Give reason.

(a) Lime water becomes milky white when CO2 is passed through it.
(b) Generally CO2 occurs in the lower places like caves, mine, deep well, etc.
(c) CO2 is collected by the upward displacement of air.
(d) We do not use dilute sulphuric acid in place of dilute hydrochloric acid.

(e) A glass vessel is used to keep sulphuric acid inside the fire extinguisher.

(f) A burning matchstick is extinguished when CO2 is passed over it.

A

B GLOSSARY
C

Uniform : not varying, the same all times

Fume : smoke, gas, etc. smelling strong

Pungent : having a strong taste or smell

Combustion : a chemical process in which substances combine with the oxygen releasing flame of fire



New Creative Science, Class 10 | 163

UNIT

11 Metals

About the Scientist INTRODUCTION

Joseph John Thomson The smallest particle of a substance is called an element and
(1856) there are only one hundred twelve elements known till now.
These elements have their own specific characteristics. On
Joseph John Thomson was born the basis of their common features, they have been classified
in Cheetham Hill, a suburb of into three groups, metals, non-metals and metalloids. Out of
Manchester on December 18, these three groups, metals are more in numbers than non-
1856. He enrolled at Owens metals and metalloids. More than 80 elements are metals
College, Manchester, in 1870, out of 112 elements. Metals are solid mineral substances
and in 1876 entered Trinity that are usually hard and electro-positive elements, which
College, Cambridge as a minor are good conductors of heat and electricity. Non-metals are
scholar. Thomson’s early interest those electronegative elements which are bad conductors
in atomic structure was reflected of heat and electricity while the metalloid elements consist
in his Treatise on the Motion of both the features of metals and non-metals.
Vortex Rings which won him
the Adams Prize in 1884. His We will discuss in detail about these elements, three groups
Application of Dynamics to of elements and their features.
Physics and Chemistry appeared
in 1886, and in 1892 he had his MEMORY TIPS
Notes. All the 112 known elements have been put in three groups
according to their common characteristics i.e. electro-positive
164 | Metals elements-metals, electronegative elements- non-metals and
having both features of metals and non-metals- metalloids.

METALS

Metals are those elements which are electro-positive in nature,
malleable, ductile and a good conductor of heat and electricity.

Sodium (Na), Potassium (K), Magnesium (Mg), Calcium
(Ca), Gold (Au), Silver (Ag), Mercury (Hg), Nickel (Ni), Iron
(Fe), Copper (Cu), etc. are some examples of metals.

NON-METALS

Those elements which are electronegative in nature, do not possess
lustre, which are not good conductors of heat and electricity, which
are not malleable and ductile are called non-metals.

Hydrogen (H), Oxygen (O), Nitrogen (N), Chlorine (Cl), Bromine (Br), Sulphur (S),
Phosphorus (P), Carbon (C) etc. are some examples of non-metals.

METALLOID

Besides metals and non-metals, there is a third category of elements, which show the
properties of both metals and non-metals. These elements are called metalloids. Boron
(B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb) and tellurium (Te) are
the examples of metalloid.

MINERALS

In nature, there are many chemical substances which contain metals along with other
elements. These substances are called minerals. In minerals, there may be high or low
quantity of metals. Hence, all minerals are not suitable to extract metals.

Minerals are those chemical substances which contain metals more or less in amount.

ORES

On the earth’s crust, there are many types of minerals but only some minerals are
suitable to extract metals for commercial purposes. These minerals are called ores. A
metal, may have many ores but only some ores are used in the metallurgical process
to extract the metal.

Ores are those minerals which are used to extract metals for commercial purposes.

METALLURGY

Metallurgy is the entire process to separate pure metals from their respective ores.

The metallurgical process employed for the extraction of metal, depends upon its
physical and chemical properties and also up the impure elements mixed with it. This
process takes the following steps.

CRUSHING AND GRINDING

In this step, the big lumps of ores are crushed and ground into small pieces and then
into powdered form.

Concentration

In this step, unwanted earthly impurities mixed with the powdered ore are removed
through gravity separation, froth floatation, magnetic separation as well as chemical
separation process, etc.

a. Froth Floatation: This method is mainly applicable to sulphide ores. The
powdered ore is mixed in water with little pine oil in a tank. Then compressed
air is passed to agitate mixture. The impurities remain at the bottom and ore
comes to the surface. The froth is skimmed off and washed with water. Thus, the
pure ore in obtained.

New Creative Science, Class 10 | 165

b. Gravity separation: This method is applicable when there are lighter impurities
and heavier ores. The powdered ore is washed with current of water. Impure
lighter particles are washed away and heavier ore particles are left behind.

c. Magnetic separation : If the ore is magnetic by nature, this method is applied.
The crushed and ground powdered ore is dropped on the moving belt of the
magnetic roller. As a result, magnet pulls magnetic elements and makes a
separate heap and non-magnetic elements from another heap.

d. Chemical separation : If there are different chemical properties, this method is
applied.

EXTRACTION OF METALS

Separation of metal in a free state is called extraction. The metal is separated from
the concentrated ore. Free metal is obtained through the reduction of oxides. If the
compound is not an oxide, it is changed into oxide form first with high heating. It can
be done by passing excess or limited air. But it should be sufficient to melt the ore.

Calcination

In calcination, the compound is heated excessively with a limited supply of air at a high
temperature to melt it.

Roasting

In roasting process, sulphide ores are converted into oxides by excessive heating with
excess air.

Reduction of Metal Oxides

In this process, combined metals are converted into separate free metals. To convert
reduced oxides into free metals, coke, carbon monoxide, hydrogen, etc. are used. If the
reduction process is done only by using coke, the process is called smelting.

Refining

The last stage of separation is called refining. The crude metal which may contain
impurities is subject to various refining methods to get pure metal is called refining. Generally,
purification is done by an electrolytic process.
In this process, an impure metal is used as anode, a piece of pure metal as cathode and
a solution of soluble salt as electrolyte. Now, a pure metal is collected at the cathode
when an electric current is supplied to it.

166 | Metals

IRON

Symbol: Fe Atomic number: 26 Atomic weight: 55.84 Valency: 2 and 3

Electronic Configuration

Shell KL M N
2
No. of electrons 2 8 14 4s2

Orbitals 1s2 2s2 2p6 3s2 3p6 3d6

Occurrence

Iron is an element. It is a hard and strong metal that is used to make steel. It is also
found in small quantities in blood and food.

Position of iron in periodic table

Iron is a transitional element. It has two outer shells which are incomplete. In its last
shell, there are two electrons. So, its position in periodic table should be in the second
group. But, its position in periodic table is the fourth period and eighth group. It does
not show similarities with the elements of the second group. It shows two valency.
After losing two electrons, it becomes ferrous ion (Fe++) and after losing three electrons
it becomes ferric ion (Fe+++).

Extraction

Iron is hardly found in a free state. It is found as a compound state because of its high
reactive features. It takes reaction with other elements. The main ores in which iron is
found are listed below:

Ores of aluminium

i. Magnetite Fe3O4 ii. Red haematite Fe2O3
iii. Siderite or iron carbonate FeCO3 iv. Iron pyrite Fe2S3
v. Limonite Fe2O3 3H2O

As extraction is a process to obtain something from something. Iron is not found freely

and it is found in different ores. Its main ore is haematite and it contains 72.5% iron.

The following process is done to obtain iron.

a. Crushing and grinding: Haematite ore is crushed and powdered.

b. Concentration: After crushing and making powder, the impurities such as clay,
sand and other dirts are removed by washing it with water.

c. Magnetic process: After concentration, it is separated from non-magnetic
elements through the magnetic separation process.

d. Roasting: The obtained ore is mixed with coal and roasted strongly by passing
hot air. The excess heat helps to change iron carbonate, (FeCO3) into its oxide
form and to drive away moisture, sulphur dioxide, carbon dioxide, etc.

e. Smelting: In this process, the ore is mixed with limestone and coke in the ratio
8 : 1 : 4 and smelted in a blast furnace. As a result, probably 93 to 95% pure iron
is obtained.

New Creative Science, Class 10 | 167

f. Purification: The last stage is to purify the crude iron by oxidation method.
The remaining parts like carbon, sulphur, and silicon impurities get oxidised to
their oxides and are removed from crude iron, and the purified iron is ready for
different purposes.

Physical properties of iron

1. Pure iron looks Grey white with shining.
2. It possesses 7.8 specific gravity.
3. It is a good conductor of heat and electricity.
4. It melts at 1535°C and boils at 2450°C.
5. Pure iron is malleable and ductile.
6. It becomes a strong magnet.

Classification of Iron

On the basis of impurity found in iron, it can be classified into three groups.
1. Pig Iron: It contains 2 to 3% of carbon and 2 to 5% other impure elements such

as sulphur, silicon, phosphorus manganese, etc. It is the most impure iron. It is
melted at 1200°C and can be cast in any shape, so it is called cast iron as well.

2. Wrought iron: It is the purest iron containing only 0.12 to 0.25% of carbon.

3. Steel: It contains 0.5 to 1.6% of carbon. It is hard iron. It melts at 1300°C.

Uses of Iron

1. It is used for different purposes in life such as to make household utensils, roads,
wire, means of transport, building bridge, weapons, tools, etc

2. It is called black gold.
3. It is the foundation of modern development and civilization.
4. It is called the father of steel.
5. All the construction activities depend on iron.

ALUMINIUM

Symbol: Al Atomic number: 13 Atomic weight: 27 Valency: 3

Electronic configuration

Shell KL M
3
No. of electrons 2 8 3s2 3p1

Orbitals 1s2 2s2 2p6

Occurrence

Aluminium is found in a combined state in Bauxite, Felspar, Cyolite and Alum stone.
It looks bluish white and is found most abundantly on the earth’s crust. Among these
ores, Bauxite is the chief one, which contains a large amount of aluminium.

168 | Metals

Position of aluminium in periodic table

Aluminium has three electrons in its last shell. So, its position in the periodic table is
the third period and the third group. It shows similarities with third group elements.
After losing three electrons, it becomes aluminium ion (Al+++).

Ores of aluminium

i. Bauxite (Al2O3. 2H2O) ii. Cryolite (Na3AlF6)
iii. Felspar (K(AlSIO3.O8))

Extraction

Aluminium is mainly found in the bauxite ore that contains silica (SiO2) and ferric
oxide (Fe2O3) as its impurities. The pure aluminium is obtained through the following
process.

a. Grinding: The big lumps of bauxite ore are crushed into small pieces and ground
into powdered form.

b. Concentration: The powdered ore of impure aluminium is mixed with sodium
carbonate and heated in the presence of carbon dioxide gas to get aluminium
hydroxide [Al (OH)3]. After this, the solution is diluted with water, and some
hydrochloric acid is added, which gives precipitate of aluminium hydroxide.
Now, it is strongly heated to get pure alumina (Al2O3).

c. Refining: At last through electrolytic process, almost 99% of pure aluminium is
obtained.

Physical properties of Aluminium

1. Its colour is bluish white.
2. In its pure form it shines.
3. It is a light metal.
4. Its specific gravity is 2.7.
5. It is a good conductor of heat.
6. It is also a good conductor of electricity.
7. Its melting point is 600°C.
8. Its boiling point is 1800°C.
9. It is malleable and ductile.

Uses of Aluminium

Aluminium is a very important metal for modern development activities as well as for
other different purposes. Some of them are given below:
1. As it is a good conductor of electricity, it is used to make electric transmission

wires.
2. It is used to make different types of household utensils, picture frames, etc.

New Creative Science, Class 10 | 169

3. It is used for making aluminium foils.
4. Different parts of aircrafts, ships, cars, buses, etc. are made from aluminium.
5. It is used to make alloys and paints.
6. It is also used to make coins.
7. Aluminium foil is used for wrapping foods, pharmaceutical products, biscuits,

chocolates, cigarettes, etc.

8. It is used in metallurgical operations as a reducing agent.

COPPER

Symbol : Cu Atomic number: 29 Atomic height: 63.57 Valency: 1 and 2

Electronic configuration N
1
Shell KL M 4s1

No. of electrons 2 8 18

Orbitals 1s2 2s2 2p6 3s2 3p6 3d10

Occurrence and Ores

Copper can be found both in a free state as well as a combined state. In a combined
state, it is found in copper glance, copper pyrite, (chalcopyrite) Cuprite and malachite.

Position of copper in periodic table

Copper is a transitional element. In its last shell, there is one electron. So, its position in
the periodic table should be one. But, its position in the periodic table is fourth period
and eleventh group (IB). It shows two valency. After losing one electron, it becomes
cuprous ion (Cu+) and after losing two electrons, it becomes cupric ion (Cu++).

Ores of copper
i. Cuprite (Cu 2O)
ii. Copper pyrite or chalcopyrite (CuFeS2)
iii. Chalcocite or copper glance (Cu2S)
iv. Malachite (Cu (OH) 2.CuCO3)

Extraction of Copper

The main source of copper is chalcopyrite (CuFeS2) ore. To extract copper from this
ore, the following steps are taken.

a. Crushing and grinding: The chalcopyrite ore is crushed into small pieces and it
is further ground into powdered form.

b. Concentration of ore: In this process, the impurities of copper are removed
through the froth floatation process.

170 | Metals

c. Roasting: To obtain copper oxide, the concentrated powdered ore is heated
strongly with sufficient air in the blast furnace to change it into sulphide. After
that, copper oxide is obtained.

d. Molten state: To obtain copper oxide, further heat is supplied in the same
furnace in the absence of air and then copper metal is formed. This form of
copper is called blister copper, which is 99.4% pure. The remaining impurities
such as Ag, Au, Ni, Zn, Pb, etc. are removed at the last stage.

e. Refining: The 99.4% pure blister copper is further purified by electrolytic
process. Now, the pure copper is ready for different purposes.

MEMORY TIPS

All metallic oxides are base but only some metallic oxides are soluble in water to give
hydroxides The molten mass of copper, which is obtaind after releasing different types of
gasses during the process of its extraction is called blister copper. It is about 99% pure.

Physical properties of Copper

1. It is a reddish brown metal.
2. It is a good conductor of electricity.
3. It is a good conductor of heat.
4. It is malleable and ductile.
5. Its specific gravity is 8.95.
6. It melts at 1083°C.
7. It boils at 2350°C.

Uses of copper

1. It is used for making electrical cables and other electrical appliances.
2. It is used to make coins, utensils, containers, etc.
3. Copper salts are used as germicides, insecticides, (fungicides) and colouring

materials.
4. It is also used for making alloys.

Some alloys of copper

Alloys Composition Uses
For making nut bolts, condenser tubes and
1. Brass Cu and Zn medals
For making utensils and bells
2. German silver Cu, Zn and Ni
3. Bronze For making household utensils and coins
4. Gun metal Cu, Zn and Sn For making ball bearings and parts of
5. Bell metal Cu, Sn, Zn and machines
Pb For making bells and decorative items.
Cu and Sn

New Creative Science, Class 10 | 171

SILVER

Symbol: Ag Atomic number: 47 Atomic weight: 107.88 Valency: 1

Electronic Configuration

Shell KL M N O
No. of electrons 1
Orbitals 28 18 18 5s1

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10

Occurrence and Ores

Silver is a d-block element. It belongs to group 1B of the periodic table. It is a white
metal. It is found both in free and combined states.

Position of silver in periodic table

Silver is a transitional element. In its last the shell, there is one electron. So, its position
in the periodic table should be one. But, its position in periodic table is fifth period and
eleventh group (IB). It shows one valency. After losing one electron it becomes silver
ion (Ag+).

Ores of silver

i. Argentite (Silver glance): Ag2S ii. Silver copper glance: (Ag.Cu)2S
iii. Ruby silver (pyrolite): 3 Ag2S. Sb2S3 iv. Horn silver: AgCl

Extraction of silver

Argentite ore is the main ore of silver. The steps of extraction are as given below.

a. Crushing and grinding: First, the big lumps of argentite ores are crushed into
small pieces and then they are ground into powdered ore.

b. Concentration: With the help of the froth floatation process, it is concentrated.

c. Reaction with sodium cyanide: The powdered ore is treated with sodium
cyanide solution and heated in a furnace in the presence of air. It forms argento
cyanide solution.

d. Action with zinc: To get clear solution of sodium argento cyanide, zinc is added
and silver is precipitated through filtration.

e. Refining: The obtained silver is further purified by electrolysis process.

Physical properties of Silver

1. It is highly malleable and ductile.
2. Its specific gravity is 10.52.
3. It is an excellent conductor of heat and electricity.
4. Its melting point is 956°C.
5. Its boiling point is 1955°C.
6. It is a shining white metal.

172 | Metals

MEMORY TIPS
Silver does not react with dilute hydrochloric acid and dilute sulphuric acid.

Uses of Silver

1. Different types of ornaments are made.
2. Coins and utensils are made.
3. It is used for silver plating.
4. It is used for filling teeth.
5. It is used for silvering mirrors.
6. It is used in photography.
7. Silver leaf is used in medicines and sweet metals for decoration as well as

medical values.

GOLD

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

Electronic configuration

Shell KL M N O P
1
No. of electrons 2 8 18 32 18 6s1
3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10
Orbitals 1s2 2s2 2p6

Gold is the most prestigious and precious metal. It is a d-block element, which belongs
to 1B group of the periodic table.

Occurrence and Ores

Gold is an inert metal. It is non-reactive. So, it is found in a free state either mixed
with quartz or alluvial soil. It is also found in a combined state as sulphide. It is also
found inside the rock. Its main sources are alluvial soil or alluvial sand or quartz veins and
calverite.

Position of gold in periodic table

Gold is a transitional element. In its last shell, there is one electron. So, its position in
the periodic table should be one. But, its position in the periodic table is sixth period
and eleventh group (IB). It shows two valency. After losing one electron, it becomes
aurous ion (Au+) and after losing three electrons, it becomes auric ion (Au+++).

Process of extraction

Gold is extracted mainly from alluvial soil, which is rich in gold. First of all, the alluvial
soil containing gold is stirred in a current of water on a zinc or iron pan by giving a
rotatory motion. In this process, sands, gravels and unwanted particles are removed.
Other impure lighter particles are washed away over the edge whereas gold particles

New Creative Science, Class 10 | 173

are left behind. In this way, gold is extracted from the alluvial soil.

Physical properties of Gold

1. It is yellow in colour.
2. It is a highly shining metal.
3. It is a good conductor of heat and electricity.
4. Its specific gravity is 19.3.
5. It is highly malleable and ductile.
6. It is the least reactive metal.

Uses of Gold

1. Gold is used the mainly for making ornaments.
2. It is used in manufacture of gold leaf electroscope.
3. It is used for gold plating over other metals.
4. Its compounds are used in photography and medicines.
5. Golden coins and other valuable articles are also made.

Occurrence of metals in Nepal

Metal Ores Districts

Iron Haematite, magnetite, limonite, Lalitpur, Chitwan, Ramechhap, Tanahau,
etc. Pyuthan, Bhojpur, etc.
Copper
Gold Chalcopyrite, Copper glance, etc. Udaipur, Dhading, Solu, Makawanpur, etc.
Cobalt
Lead or Zinc Alluvial soil Kathmandu, Mustang, etc.
Bismuth
Magnesium Cobaltite Gulmi, Palpa, etc.

Deposit of lead or zinc Lalitpur, Ganesh himal, etc.

Bismuth Makawanpur

Magnetite Dolakha, Udaipur

MODEL QUESTIONS ANSWER

1. Why does aluminium not react with dilute as well as concentrated nitric acid?

Ü Aluminium reacts with oxygen to form aluminium oxide (Al2O3). This oxide
layer of aluminium adhers to the outer surface of the aluminium objects and

protects the aluminium from the corrosion.

2. How does aquaregia react with gold?

Ü Aquaregia is a mixture of 3 : 1 ratio of concentrated hydrochloric acid and
concentrated nitric acid. This mixture furnishes nascent chlorine when it is
heated. Hence, this nascent chlorine reacts with gold to give gold chlorine.

{3HCl + HNO3 ∆ NOCl + 2H2O + 2Cl} × 3

(Aquaregia) 2AuCl3 Auric chloride

2Au + 6Cl

174 | Metals

2Au + 3HNO3 + 9HCl 2AuCl3 + 3NOCl + 6H2O

3. An iron rod becomes reddish brown colour when it is kept in the moist place.

Why?

Ü When an iron rod comes in contact with moist air, it slowly forms hydrated
ferric oxide (i.e.rust). Hence, it turns reddish brown over its surface.

4Fe + 3O2 + nH2O 2 Fe2O3.nH2O rust
4. What is blister copper?

Ü During the extraction of copper, when cuprous sulphide reacts with cuprous
oxide, it forms copper and sulphur dioxide. This sulphur dioxide tries to escape
out from the molten copper in the form of bubbles. The copper of this stage is
called blister copper.

EXERCISE

1. Write two important ores of the given metals.
Iron, Aluminium, Copper, Silver

2. Write any two differences between ores and minerals.
3. Define metallurgy and explain the extraction of aluminium in brief.
4. Write any three physical properties of iron, aluminium, copper, silver and gold.
5. Write the name of metals which are obtained from the given ores.

(a) Bauxite (b) Cuprite (c) Argentile (d) Alluvial soil (e) Malachite
6. Which metal do you get from quartz veins?
7. Define coinage metals. Which metals are kept within this group?
8. Give reason:

(a) Aluminium is used to make foils for food covering.
(b) Copper is used to make electric wires.
(c) Silver, gold and copper are called coinage metals.
(d) Gold occurs freely in the nature.

A

B GLOSSARY
C

Malleable : that can be compressed or hit into different shapes

Metallurgy : scientific study of metals and their use

Commercial : connecting with the buying and selling

Lump : a piece of sth without particular shape

Alluvial : made of sand and earth



New Creative Science, Class 10 | 175

UNIT

12 Hydrocarbons and their Compounds

About the Scientist INTRODUCTION

Edmond The chemical compounds formed by the combination of
(1656) carbons and hydrogens are called hydrocarbons.

Edmond (or Edmund) Halley’s In hydrocarbon, the four valencies of carbon are satisfied by
father was also called Edmond other carbon and hydrogen atoms. For example, methane
(or Edmund) Halley. He came (CH4), ethane (C2H6), propane (C3H8), ethene (C2H4), etc.
from a Derbyshire family and Petroleum materials and natural gases are the main sources
was a wealthy soap-maker in of hydrocarbons. They are classified into the following two
London at a time when the use of groups:
soap was spreading throughout 1) Saturated Hydrocarbon
Europe. There is some confusion 2) Unsaturated Hydrocarbon
over both the date and year of
Halley’s birth. The confusion 1. Saturated hydrocarbons (or alkane)
over the date is simply due to the
change in calendar (29 October Those hydrocarbons in which carbon atoms are bonded
by the calendar of his time). The together by a single covalent bond are called saturated
confusion over the year is less hydrocarbons or alkane.
easy to decide, but we give 1656
which Halley himself claimed as Methane (CH4), ethane (C2H6), propane (C3H8), etc. are the
the year of his birth. examples of saturated hydrocarbons. The general formula of
alkane is CnH2n+2 where ‘n’ indicates the number of carbon
atoms. To write the name of alkane, we add the suffix “ane”.
Some examples of alkane with their IUPAC name and
structure are given below:

S.N. No. of Molecular Structure IUPAC
carbon formula Name
atoms

1. 1 (Meth) CH4 Methane

2. 2 (Eth) C2H6 Ethane

3. 3 (Prop) C3H8 Propane

176 | Hydrocarbons and their Compounds

4. 4 (But) C4H10 Butane

5. 5 (Pent) C5H12 Pentane

6. 6 (Hex) C6H14 Hexane

7. 7 (Hept) C7H16 Heptane

8. 8 (Oct) C8H18 Octane

9. 9 (Non) C9H20 Nonane

10. 10 (Dec) C10H22 Decane

MEMORY TIPS
The full name of IUPAC is the international union of pure applied chemists.

2. Unsaturated hydrocarbons

Those hydrocarbons in which carbon atoms are bonded together by multiple (double or triple)
covalent bonds are called unsaturated hydrocarbons.

Some examples of unsaturated hydrocarbons are ethene (C2H4), propene (C3H6),
ethyne (C2H2), propyne (C3H4), etc. Unsaturated hydrocarbons are further divided
into two groups.

(i) Alkene
(ii) Alkyne

New Creative Science, Class 10 | 177

(i) Alkene

The unsaturated hydrocarbon in which carbon atoms are bonded together by double covalent
bonds is called alkene.

Examples of alkene are ethene, propene, butane, etc. The general formula of alkene is
CnH2n, where ‘n’ indicates the number of carbon atoms. While naming the alkene we
add ‘ene’ at the end of number of carbon atoms.
Some more examples of alken with their IUPAC name and structure are given below

S. No. of Molecular Structure WPAC
N. carbon atoms formula Names

1. 2 (Eth) C2H4 Ethene

2. 3 (Prop) C3H6 Propene

3. 4 (But) C4H8 Butene

4. 5 (Pent) C5H10 Pentene

5. 6 (Hex) C6H12 Hexene

6. 7 (Hept) CH Heptene
7 14

7. 8 (Oct) C8H16 Octene

178 | Hydrocarbons and their Compounds

8. 9 (Non) C9H18 Nonene

9. 10 (Dec) C10H20 Decene

(ii) Alkyne

The unsaturated hydrocarbon in which carbon atoms are bonded together by triple covalent
bonds is called alkyne.

Examples of alkyne are ethyne, propyne, butyne, etc. The general formula of alkyne
is CnH2n – 2 where ‘n’ indicates the number of carbon atoms, while writing the name of
alkyne, we add ‘yne’ at the end of number of carbon atoms.

Some more examples of alkyne with their IUPAC name and structure are given
below:

S.N. No. of Molecular Structure IUPAC
carbon formula Name
atoms

1. 2(Eth) C2H2 H —C ≡ C—H Ethyne

2. 3(Prop) C3H4 Propyne

3. 4(But) CH Butyne
46

4. 5(Pent) C5H8 Pentyne

5. 6(Hex) C6H10 Hexyne

6. 7(Hept) C7H12 Heptyne
New Creative Science, Class 10 | 179

7. 8(Oct) C8H14 Octyne

8. 9(Non) C9H16 Nonyne

9. 10(Dec) C10H18 Decyne

MEMORY TIPS

In alkene and alkyne, the first member has two carbon atoms. There is no possibility of
methane and methyne.

Differences between saturated and unsaturated hydrocarbons

Saturated hydrocarbons Unsaturated hydrocarbons

1. In these hydrocarbons, carbon 1. In these hydrocarbons, carbon atoms

atoms are bonded by a single are bonded by multiple bonds.

covalent bond.

2. Saturated hydrocarbon has only 2. Unsaturated hydrocarbons has two

one group which is alkane. groups, which are alkene and alkyne.

For example: methane ethane, For example: ethene, ethyne, propene,
propane, etc. propyne, etc.

Differences between alkene alkyne Alkyne

Alkene In alkyne, carbon atoms are bonded
1. In alkene, carbon atoms are bonded 1. by triple covalent bonds.
The general formula of alkyne is
by double covalent bonds. CnH2n – 2.
2. The general formula of alkene is 2.
For example: ethyne, propyne, etc.
CnH2n.
For example: ethene propene, etc.

ALKYL RADICALS

The radical which is obtained after removing one hydrogen atom of the alkane is called alkyl
radical. For example, methyl radical (CH3+) is obtained after removing one hydrogen
atom from methane(CH4), similarly ethyl radical (C2H5+) is obtained after removing
one hydrogen atom from ethane (C2H6) . Generally, alkyl radical are indicated by R. Its
general formula is CnH2n+1, where n indicates the number of carbon atoms.

180 | Hydrocarbons and their Compounds

FUNCTIONAL GROUP

In alcohol, chemical properties depend upon hydroxyl group and in amine, chemical
properties depend upon amine (–NH2) group. Here, in organic compounds, there are
some atoms or group of atoms in which chemical properties the whole compound
depend. They are called the functional group.

Atoms or group of atoms on which chemical properties of compounds depend are called
functional groups.

Some more examples of functional group with their symbol and structure are as
given below:

S.N. Name of functional group Symbol Structure Organic
compounds
1. Hydroxyl - OH - OH alcohol
acid
2. Carboxylic acid - COOH O ether
|| aldehyde
3. Ether -O- - C - OH
ketone
4. Aldehyde (formyl) - CHO -O-
amine
5. Keto - CO - O
||
6. Amino - NH2 -C-H

O
||
-C-

H
|
-N-H

IUPAC SYSTEM

There are different systems of nomenclature of the organic compounds. Among
them, the IPUPAC (International Union of Pure and Applied Chemistry) system of
nomenclature is widely accepted. To write the name of the organic compounds based
on IUPAC system, the following points should be remembered.

1. Word root

The longest chain with functional group is called the word root. On the basis of the
number of carbon atoms it is denoted as:

New Creative Science, Class 10 | 181

Number of carbon atom Word root
C1 Meth
C2 Eth
C3 Prop
C4 But
C5 Pent
C6 Hex
C7 Hept
C8 Oct
C9 Non
C10 Dec

2. Suffix

Suffix is written along with the word root. For example; in pentane, pent is a word
root and ane is a suffix. For example, in root CH3 – CH3, the word root is eth because
it has two carbon atoms. Similarly, the suffix is ane. So, the name of this compound
is ethane. Some more examples of alkanes with their IUPAC names are given below.

Structure of hydrocarbon Word root IPUAC name
Meth Methane
CH4 Eth Ethane
CH3 – CH3 Prop Propane
CH3 – CH2 – CH3 But Butane
CH3 – CH2 – CH2 – CH3 Pent Pentane
CH3 – CH2 – CH2 – CH2 – CH3 Hex Hexane
CH3 – CH2 – CH2 – CH2 – CH2 – CH3 Hept Heptane
CH3 – CH2 – CH2 – CH2 – CH2 – CH2 – CH3

HOMOLOGOUS SERIES

When organic compounds of the same group are arranged on the basis of the increasing
molecular weight then we get a series which is called homologous series. The members
of homologous series have the same functional group, structural formula and they
show the similar chemical properties.

The series of organic compounds which have the same functional group but two successive

members differ by CH2 group, are called homologous series.

For example: CH3 – OH methanol

CH3 – CH2 – OH ethanol

CH3 – CH2 – CH2 – OH propanol

182 | Hydrocarbons and their Compounds

Characteristics of homologous series

1. All the members of the same series have the same functional group.
2. They have the same general formula.
3. Every two successive members of homologous series differ by CH2 group.
4. All the members of homologous series have the same general method of

preparation.
5. They have similar chemical properties.

Some hydrocarbons and their compounds

Methane (CH4)

It is the simplest and first member of saturated hydrocarbon. It is obtained by the
decomposition of organic matters in swamps or marshy places, so it is also known as
marsh gas. It is also present in coal mines, gobar gas and bio-gas.

CH4 `

Molecular formula of methane Structural formula of methane

Uses of methane

1. Methane is an important gaseous fuel because it produces a large amount of

heat energy on burning.

2. It is used in the form of LPG for domestic use.

3. It is used in the manufacturing of different types of industrial chemicals like

methyl chloride (CH3Cl), chloroform (CHCl3), carbon tetrachloride (CCl4),
methanol (CH3OH), etc.
4. It is used in the manufacturing of carbon, printing ink, water gas (CO + H2),
hydrogen gas, etc.

MEMORY TIPS
LPG = Liquefied Petroleum Gas

Ethane (C2H6)
It is the second member of saturated hydrocarbon which is slightly heavier than
methane but it also occurs with methane in natural gas, petroleum, coal, gas, etc.

CH3 – CH3 or

Structural formula of ethane

New Creative Science, Class 10 | 183

Uses of ethane
1. It is used as a gaseous fuel along with methane to produce a large amount of

heat energy on burning.
2. It is also used as a laboratory reagent to produce other different compounds.
Propane (C3H8)
It is the third member of saturated hydrocarbon. It occurs in natural gas, LPG, petroleum
mine, etc. It is used as a fuel, a refrigerant and to produce other compounds, etc.

CH3 – CH2 – CH3 or

Structural formula of propane

Butane (C4H10)
Butane is the fourth member of saturated hydrocarbon, which occurs in natural gas,
petroleum mines, etc. It is used in the manufacturing of synthetic rubber, gaseous fuel
and other compounds.

CH3 – CH2 – CH2 – CH3 or

Structural formula of butane

MEMORY TIPS
In butane, there are two structures n- butane and iso-butane which are also called isomers.

n-Butane iso-Butane

Isomers of butane

ALCOHOLS

Hydroxyl derivatives of alkane are called alcohol.

In alcohol, hydroxyl group (–OH) is present attached to the alkane. It is obtained by
the substitution of hydrogen of alkane by hydroxyl group.

—H
+ OH

Methane Methanol

184 | Hydrocarbons and their Compounds

Some examples of alcohols Structural formula Name
S.N. Molecular formula Methanol

1 CH3 – OH

2 C2H5 – OH Ethanol

3 C3H7 – OH Propanol

4 C4H9 – OH Butanol

5 C5H11 – OH Pentanol

Types of alcohol

On the basis of the number of hydroxyl groups present, there are three types of alcohol.

(a) Monohydric alcohol: Those alcohols which have one hydroxyl group in their
structure are called monohydric alcohols.

They are obtained by the replacement of one hydrogen from alkane by hydroxyl
group.

—H
+ OH

Methane Methanol

(b) Dihydric alcohol: Those alcohols which have two hydroxyl groups in their
structure are called dihydric alcohols.

They are formed by the replacement of two hydrogen atoms from alkane by two
hydroxyl groups.

New Creative Science, Class 10 | 185

— 2H
+ 2OH

Ethane Ethyl glycol or glycol

(c) Trihydric alcohol: The alcohols which have three hydroxyl groups in their
structure are called trihydric alcohols.

They are obtained by replacing three hydrogen atoms of alkane by three
hydroxyl groups.

— 3H
+ 3OH

Propane Glycerol

SOME ALCOHOLS

Methyl alcohol or methanol (CH3 – OH)

It is the first member of monohydric alcohol, which is obtained by replacing one
hydrogen of methane by one hydroxyl group.

—H
+ OH

Methane Methanol

Uses of methanol
1. It is used as a fuel because it produces a large amount of heat without smoke.
2. It is used as an organic solvent for fats, oils, paints, etc.
3. It is used to manufacture perfume, dyes, medicine, synthetic fabrics, etc.
4. It is used for dry cleaning.
5. It is used as a moisturising agent in cosmetic items.

Ethyl alcohol or ethanol (C2H5 – OH)

It is the second member of monohydric alcohol, which is obtained by replacing one
hydrogen of ethane by one hydroxyl group. It is the earliest representative of the
monhydric alcohol.

— 2H
+ 2OH

Ethane Ethanol

186 | Hydrocarbons and their Compounds

Uses of ethyl alcohol
1. It is used for drinking as an alcoholic beverage.
2. It is used as a fuel in sprite lamps and stoves.
3. It is a thermometric liquid, which is used in an alcoholic thermometer.
4. It is used to dissolve fat, oil, paints, etc.
5. It is used in medicines.
6. It is used as a preservative liquid to preserve biological specimens.

Glycerol or Trihydric alcohol

It is the simplest trihydric alcohol. The word glycerol is derived from glyceros which
means a sweet taste. It is formed by replacing three hydrogens of propane by three
hydroxyl groups. It is present in animal and plant fats. It is also prepared by the
hydrolysis of fat or oil.

— 3H
+ 3OH

Propane Glycerol

Uses of glycerol
1. It is an important sweetening agent in confectionery, beverages and medicines.
2. It is used in the manufacturing of printing ink, stamp pad inks, soaps, cosmetics,

etc.
3. It is used as a preservative to preserve fruits, tobacco, etc.
4. It is used as a lubricant.

Ether

Ether is a group of organic compounds which has oxygen atom between two alkyl
groups. It is represented by R – O – R, where ‘R’ is the alkyl group like CH3, C2H5, etc.

Some examples of ether
i. Dimethyl ether or methoxy methane

CH3 — O — CH3 or

ii. Diethyl ether or ethoxy ethane

C2H5 — O — C2H5 or CH3 — CH2 — O — CH2 — CH3

New Creative Science, Class 10 | 187

iii. Ethyl methyl ether or methoxy ethane

CH3 — O — C2H5 or

MEMORY TIPS
Diethyl ether is simply known as ether.

Uses of ether
1. It is used as a general local anaesthetic agent during minor operation.
2. It is used to purify organic compounds by extraction.
3. It is used as an organic solvent.
4. It is used as a cooling agent.

Glucose

The word glucose was derived from the Greek word glukus means sweet. Its molecular
formula is C6H12O6. It is a white crystalline solid which is soluble in water. It is a
monomer of carbohydrate. So, it is also called monosaccharide sugar or dextrose. It
is the simplest sugar because it is one of the smallest units of carbohydrates, which
has the characteristics of the carbohydrates. It is present in honey, nectar, etc. It is
produced during photosynthesis in plants and is used to produce ATP in the body.
Glucose circulates in the blood of animals as blood sugar. It is used in the cells as a
source of energy and also helps in the metabolism.

The normal concentration of sugar in the blood of a normal person is 0.1 percentage.
But its value may increase in some people suffering from diabetes. When glucose
combines with oxygen, it produces carbon dioxide and water. It is called oxidation of
sugar. In this process a large amount of energy is released, which is used to sustain
life. Some patients, who are suffering from low blood sugar are supplied glucose as a
primary energy source in the body. This is because it requires no digestion and is often
provided intravenously in the hospital.

MODEL QUESTIONS ANSWER
1. What is LPG? Which chemicals are present in it?
Ü LPG means liquefied petroleum gas. It is an important gaseous fuel which is the

mixture of mostly n- butane and iso-Butane.
2. Define isomers with examples.
Ü Those organic compounds which have the same molecular formula but are differ

in their structure are called isomers. For example; n-butane and iso-Butane.

n-Butane iso-Butane
Isomers of butane

188 | Hydrocarbons and their Compounds

3. Write two differences between alkene and alkyne

S.N. Alkene S.N. Alkyne

1. Those hydrocarbons in which 1. Those hydrocarbons in which

carbon atoms are bonded together carbon atoms are bonded together

by double covalent bonds are called by triple covalent bonds are called

alkene. alkyne.

2. The general formula of alkene is 2. The general formula of alkyne is

CnH2n where ‘n’ indicates number CnH2n – 2 where ‘n’ indicates number
of carbon atoms. of carbon atoms.

For example: ethene (C2H4), propene For example: ethyne (C2H2),
(C3H6), etc. propyne (C3H4), etc.

4. Why does carbon make covalent bond?

Ü Carbon has four electrons in its valence shell. So, it shares these four electrons
with other same or different atoms making four covalent bonds.

EXERCISE

1. Define the following terms with examples:

(a) Hydrocarbons (b) Saturated hydrocarbon

(c) Unsaturated hydrocarbon (d) Homologous series

2. Write two differences between the following:

(a) saturated and unsaturated hydrocarbons

(b) alkane and alkene

(c) alkene and alkyne

3. Write structure and two uses of each:

(a) Methane (b) Ethane (c) Propane (d) Ethene

(e) Ethyne (f) Methanol (g) Ethanol (h) Dimethyl ether

(i) Glycol (j) Glycerol (k) Glucose

4. What happens when three hydrogens of propane are replaced by three hydroxyl
groups? Write the structure of this resultant compound with its two uses.

5. What happens when two hydrogens of ethane are replaced by two hydroxyl
groups? Write the structure of this resultant compound with its two uses.

A

B GLOSSARY
C

Swamp : very wet or covered land with water with plants
Marshy : always soft and wet land

Anaesthetic : a drug that makes a person or animal unable to feel



New Creative Science, Class 10 | 189

UNIT

13 Materials Used in Daily Life

About the Scientist INTRODUCTION

Sir Humphry Davy All living beings depend on different types of materials,
goods, things or substances for their survival. There is a
Sir Humphry Davy was a regular interaction between living beings and non-living
Cornish chemist and physicist, things. We human beings are also the important part of this
well known for his contribution environment. We need to use different types of living as well
to the field of electro-chemistry. It as non-living things and substances for our existence and
is said that Davy discovered the development. Our every essential things like food, shelter,
elements magnesium, calcium, clothing, health, medicine, education, recreation, etc. are
strontium, and barium through supplied and fulfilled by natural and artificial substances.
the process of electrolysis. Davy In the earlier stage of human life and civilization, human
is also famous for having sniffed beings used to depend on natural things more and more
nitrous oxide (“laughing gas”) in but with the development of the human mind, science and
1800. knowledge, they develop so many things for their daily
use and survival. Gradually, the human being has become
and made its life much more artificial. Now, it is beyond
imagination to think human life can't be continued without
man-made materials such as synthetic foods, medicines,
constructional substances such as cement, iron, steel, means
of transport, educational materials, means of communication,
recreational materials, fertilizers, pesticides, dyes, fibres,
different types of liquids, means of immunization, drugs, etc.
All these things have made human life civilized, advanced,
speedy, easy and comfortable.

Here in this unit, we will study about different materials,
which are being used in our daily life.

CEMENT

Cement is an important construction material, which is used
to construct buildings, roads, bridges, dams, walls, etc. It is
very fine powder with grey colour. It becomes hard when it
is mixed with water and left out for some time.

The fine grey powder of calcium silicate and calcium aluminate
which becomes hard and strong when it is mixed with water and
left out for some time is called cement.

190 | Materials Used in Daily Life

The chemical reaction which involves during cement manufacturing is given below.
Calcium carbonate + Aluminium oxide+ Silica = Calcium silicate + Calcium aluminate
CaCO3 +Al2O3 + SiO2 → CaSiO3 + CaAl2O3

Raw materials of cement

Cement is manufactured by using the following raw materials.
1. Limestone (or calcium carbonate) – CaCO3 (2/3 parts)
2. Special type of clay – Al2O3. SiO3 (1/3 parts)

MEMORY TIPS
About 2-3 percentage of gypsum (CaSO4. 2H2O) and some iron oxides are added to the
cement to improve the quality and to slow down the setting time of the cement.

Steps of cement manufacturing

1. Formation of cement slurry: The raw materials of cement i.e. limestone and
special type of red soil are crushed in a crusher and then ground into very fine
powder. The powder raw material is mixed together in the ratio of 2 : 1 and
then mixed with water to make paste like soapy mixture, which is called cement
slurry.

2. Formation of cement clinker: The mixture of above raw materials is fed
into a rotatory kiln (It is tall and slanted tower with about 1400°C to 1600°C
temperature). When the mixture goes up in the tower, it undergoes chemical
change. As a result of the chemical change, limestone decomposes into calcium
oxide and carbon dioxide. The calcium oxide combines with aluminium oxide
of special type of soil and silica to form calcium silicate and calcium aluminate.
This calcium silicate and calcium aluminate occurs in a pea-sized black ball-like
structure which is also called cement clinker.

MEMORY TIPS
Pea-sized balck ball-like structure of calcium silicate and calcium aluminate is called cement
clinker.

3. Formation of cement powder: About 2-3% of gypsum and cement clinker is
mixed and ground again to make fine powder. This powder is called cement.

MEMORY TIPS
Chemically cement is the complex mixture of 4 types of compounds i.e. dicalcium silicate,
tricalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite.

New Creative Science, Class 10 | 191

Uses of cement

1. To make cement mortar: The mixture of cement, sand and water which is used for
the plastering purpose of a wall, to join bricks and stones is called cement mortar.

MEMORY TIPS Cement mortar
Cement + Sand + Water

2. To make cement concrete: The mixture of cement, sand, water and gravel,
which is used for roofing, flooring and making pillars is called cement concrete.

MEMORY TIPS Cement concrete
Cement + Sand + Water + Gravel

3. To make reinforced cement concrete (RCC): The mixture of cement, sand,
water and gravel, which is present in the framework of iron rods during making
of pillar, roof and floor is called RCC.

MEMORY TIPS RCC
Cement + Sand + Water + Gravel + Iron rods

4. Cement is the most important construction material for present days. Hence, it
is used to make roads, buildings, bridges, dams, walls, monuments, etc.

Some important cement factories of Nepal

SN Name of the cement factory Location
1. Udayapur Cement Factory Udayapur

2. Hetauda Cement Factory Hetauda, Makawanpur
3. Bishawakarma Cement Factory Mukundapur, Nawalparasi
4. Triveni Cement Factory Bharatpur, Chitwan

QUESTIONS

# Define cement based on its chemical composition and write down its three uses.
# Define cement mortar, cement concrete, cement clinker, RCC and cement slurry.

GLASS

The homogeneous mixture of different types of metallic silicates which is hard transparent and
amorphous in nature is called glass.

Glass is one of the important man-made industrial materials which has been used in
houses, vehicles, factories, lens, mirror, laboratory, equipments, etc.

MEMORY TIPS

Glass is not a solid but it is a super cooled liquid because their molecules move up to down
like the molecules of liquid with very slow speed.

192 | Materials Used in Daily Life

Characteristics of glass

i. Glass is a homogeneous mixture of different types of metallic silicates.
ii. It is hard, transparent and supercooled liquid.
iii. It is bad conductor of heat and electricity.
iv. It does not react with acid, base, salt and other chemicals.
v. The properties of glass like MP, BP, etc. depend upon its composition.

Types of glass

1. Quartz glass (or silica glass)

The glass which is obtained after heating pure silica up to 1600°C is called quartz glass.
Pure silica 1600°C Quartz glass

Characteristics

It is very hard and crystalline glass. It does not dissolve in water, acid, alkali and other
chemicals. It has more thermal resistant power.

Uses

It is used to make electrical appliances, laboratory equipments, gems, coloured quartz,
etc.

2. Water glass

The glass which is obtained after heating the mixture of sodium carbonate with silica or

potassium carbonate with silica at about 800°C is called water glass.

Na2CO3 + SiO2 800°C Na2SiO3 + CO2

Sodium silicate

or K2CO3 + SiO2 800°C K2SiO3 + CO2

Potassium silicate

Characteristics

This glass gets dissolved in water so it is also known as water glass.

Uses
It is used for making fireproof materials, silica garden, gums, glue, paste, etc.

MEMORY TIPS
Chemically water glass is potassium silicate or sodium silicate.

3. Ordinary glass (or soft glass or soda glass)

The glass which is obtained after heating the mixture of sodium carbonate, calcium carbonate
and silica at high temperature is called ordinary glass.

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

Sodium silicate and calcium silicate

New Creative Science, Class 10 | 193

The actual composition of ordinary glass is 50% silica, 25% pieces of glass, 15% sodium
carbonate and 10% calcium carbonate.

Characteristics
It has very low thermal resistant power and it is insoluble in water.

Uses
It is used to make lens, prism, simple bottles, windowpanes, glass sheets, laboratory
equipment, etc.

MEMORY TIPS

i. Chemically ordinary glass is the homogenous mixture of sodium silicate and calcium
silicate.

ii. When lead monoxide is added to the mixture of ordinary glass, it becomes lead silicate
glass which has high refractive index and less transparency.

iii. Calcium carbonate makes the ordinary glass insoluble and pieces of glass decrease
the melting point of the mixture.

4. Hard glass (or potass lime glass)

The glass which is obtained after heating the mixture of potassium carbonate, calcium carbonate,
and silica at high temperature is called hard glass.

K2CO3 + CaCO3 + 2SiO2 1500°C K2SiO3 . CaSiO3 + 2CO2

Potassium silicate and calcium silicate

Characteristics

It is hard with high thermal resistant power, insoluble in water, acid, alkali and other
chemicals.

Uses

It is used for making different types of laboratory equipment like beakers, hard glass
test-tube, electric bulb, tube light, etc.

MEMORY TIPS

Chemically hard glass is the homogeneous mixture of potassium silicate and calcium
silicate.

5. Borosilicate glass (or Pyrex glass)

The glass which is obtained after heating the mixture of sodium carbonate, calcium carbonate,
boron oxide and silica at a high temperature is called borosilicate glass or Pyrex glass.

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

Sodium silicate, Calcium silicate and Boron silicate

Characteristics

It is hard and does not melt at an ordinary temperature.

194 | Materials Used in Daily Life

Uses

It is used to make the superior quality glass of laboratory equipment like beakers,
hard glass test tube, electric bulb, tube light, etc.

MEMORY TIPS

i. Chemically borosilicate glass is the homogeneous mixture of sodium silicate, calcium
silicate and boron silicate.

ii. Due to presence of boron silicate, it is strong and hard.

6. Lead crystal glass

The glass which is obtained after heating the mixture of potassium carbonate, lead monoxide
and silica at a high temperature is called lead crystal glass.

K2CO3 + PbO + 2SiO2 K2SiO3.PbaSiO3+ 2CO2

Potassium silicate and lead silicate

Characteristics

Due to the presence of lead silicate, it has high refractive index and less transparency.

Uses

Since it has high refractive index, so it is used to make lens, prism, electric bulb,
spectacles, radar tube, expensive drinking glasses, etc.

MEMORY TIPS

i. Chemically lead crystal glass is potassium silicate and lead silicate.
ii. It is also known as optical glass.
iii. It also cut off the ultra violet radiation.

7. Coloured glass

Coloured glasses are obtained by adding different metallic oxides of the respective
colours in the molten mass of raw materials of the glass. The different metallic oxides
with their respective colours are given in the table.

S.N. Metallic oxides Colour

1. Nickel oxide Black
2. Cobalt oxide Blue
3. Copper oxide Red
4. Chromium oxide Green
5. Iron oxide Yellow/Brown
6. Manganese oxide Purple
7. Tin oxide Milky white

Uses

They are used to make sunglasses, windowpanes, traffic signals, disco light, artificial
gems, etc.

New Creative Science, Class 10 | 195

Different types of glasses and their composition.

Glass Composition
Silica glass Silica
Water glass Silica and sodium carbonate or potassium carbonate
Ordinary glass Silica(50%), broken glass (25%), sodium carbonate(15%), calcium
carbonate(10%)
Borosilicate glass Silica, sodium carbonate, calcium carbonate and boric oxide
Hard glass Silica, potassium carbonate and calcium carbonate
Lead crystal glass Lead monoxide, potassium carbonate and mixture of ordinary glass

SOAP AND DETERGENT

Soap and detergent are the man-made chemical substances, which are used to remove
the dirty things like oils, greases, ink, paint, etc. from the clothes, pots, body, etc.

Soap

Sodium salt of long chain of fatty acid which has cleansing property in water is called soap. For
example: sodium oleate (C17H33COONa), sodium palmitate (C15H31COONa), Sodium
laurate (C11H23COONa), Sodium stearate (C17H35COONa), etc.

Raw materials of soap

There are mainly two raw materials of soap. They are
1. Fat (animal or plant)
2. Sodium hydroxide (NaOH)
3. Sodium chloride (NaCl)

The soap prepared from the animal fat has a high quality whereas the soap prepared
from the plant fat i.e. oil of olive, coconut, cotton seeds, etc. has a low quality.

The process by which soap is prepared from fat and sodium hydroxide is called

saponification.

C17 H35 CO O — 2 CH
C17 H35 CO O
C17 H35 CO O | H + 3 NaOD H 3 C17 H35 CO O Na + 2 —CH O H
—C |

| (Sodium stearate) CH — O H

— 2 CH |

(Glyceryl stearate) CH2 — O H
[From animal fat] (Glycerol)

During soap preparation, the mixture of fat and sodium hydroxide is heated with
constant stirring. When mixture becomes semi-solid or paste-like structure, it is
allowed to cool down. Some amount of sodium chloride is added to the mixture to
bring the soap in precipitate form. Sometimes, a little amount of starch or sodium
carbonate is also added to make the soap hard. Different types of perfumes, colours,
antiseptic, and bleaching materials are also added to increase the quality of soap.

196 | Materials Used in Daily Life