New Creative Science Book 9

Corrosion

When the surface of a metal is attacked by gases present in air (O2, CO2 , H2O,
etc.) and water vapour, it is said to corrode and the phenomenon is called corrosion.

Rusting

Corrosion of iron is called rusting. When iron is exposed to moist air for a long
time its surface acquires a coat of a brown and peeling substance called rust, and the
process is called rusting. Rust is mainly hydrated iron (iii) oxide (Fe2O3 . nH2O). Both
air and moisture are needed for rusting.

4Fe + nH2O + 3O2 → 2Fe2O3 . nH2O (Rust)

Role of metals in organisms

Roughly 96 percent of the mass of the human body is made up of just four elements;
they are oxygen, carbon, hydrogen, phosphorus, sulphur and nitrogen. They are the
sources of protein, nucleic acid, lipids, etc. The remaining 4 percent is covered by 20 or
more elements. They are very essential for our body. These essential mineral elements
are usually classified into two main groups according to their concentration in the
animal’s body. They are the macro elements and the microelements (trace elements).
The essential mineral elements that are needed by the body in higher concentration
are called macro elements (Ca, Mg, Na, K) and those that are required by the body
in trace amount are called micronutrients (Fe, Zn, Mn, Cu, I, F, V, Mo, Se, Co, Ni, Si).
All these elements are known as biological inorganic elements. Among these various
mineral elements, most of them are metals. Metals also have a very important role in
the biological activities.

Some of the important functions of the metals in our body are listed below:
i) Metals are essential constituents of the skeletal structures such as bones and
teeth.
ii) Metals play a key role in the maintenance of osmotic pressure, and thus
regulate the exchange of water and solutes within the animal body.
iii) Metals serve as structural constituents of the soft tissues.
iv) Metals are essential for the transmission of nerve impulses and muscle
contraction.
v) Metals play a vital role in the acid-base equilibrium of the body, and thus
regulate the pH of the blood and other body fluids.
vi) Metals serve as essential components of many enzymes, vitamins, hormones, etc.

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Zinc in Enzyme

Zinc is present in the human body as a trace element. It is an important metal
for the biological activities. It is an essential component of more than 80 metallo-
enzymes, including carbonic anhydrase (required for the transport of carbon dioxide
by the blood and for the secretion of HCI in the stomach), glutamic dehydrogenase,
alkaline phosphatase, pancreatic carboxy peptidase, etc. Zinc serves as a cofactor
in many enzyme systems, including arginase, enolase, etc. Zinc plays a vital role in
lipid, protein, and carbohydrate metabolism. It is particularly active in the synthesis
and metabolism of ribonucleic acids (RNA) and proteins. More than 90% of zinc
is found in muscles and bone of the human body. The quantity of zinc is high in
semen, prostate gland and retina of the eyes. Unclear vision with increase in age and
blindness is due to decreased amount of zinc in the retina of the eyes.

Importance of zinc in the human body
i) It helps in cell division, growth and the development of the human body.
ii) It maintains a reproductive capacity both in males and females. It also helps
in regular menstruation in women.
iii) It is an important substance for the treatment of diarrhoea especially in kids. It
also helps in the treatment of common cold, pneumonia and other infections.
iv) It regulates neurons to communicate properly.
v) Zinc helps to protect the skin and mucosal membranes. It also helps in the
healing of wounds and to decrease the inflammation and bacterial growth.
vi) Zinc is necessary to improve cardiovascular health.
vii) It also helps to produce insulin and to prevent us from diabetes.

Importance of Sodium and Potassium ions in a Human Body

Sodium and Potassium ions act as power generators inside the cells of a human
body. Neuron cells are located throughout the nervous system. They transfer
information to perform important tasks such as regulating body temperature,
activating muscles, etc. For example, if you want to move your fingers, your brain
transmits a message to the muscles present in your hand. Neurons transmit that
message. Neurons use ions to communicate. Ions are electrically charged chemicals.
Sodium and potassium are the most important ions present in the nervous system.

Pure water does not conduct electricity. Sodium, potassium and other electrolytes
get dissolved in water. The cells in our body need to transport electrolytes, which
maintain electric impulses. The sodium-potassium pump is an important mechanism
in a human body in which sodium and potassium ions move in and out of the cells to
maintain electric impulses.

198 | Metals

Sodium and potassium ions also maintain the heartbeat between 60 to 100 times
per minute in a healthy human body. Drop in the number of heartbeat below 60
times in a minute indicates the heart is not working properly. Therefore, a special
device called a pacemaker is used in the human heart to restore the heart beat and to
maintain its consistency. A pacemaker is a simple kind of battery which is implanted
in the chest of human body and provides electrical charge through its two small wires
to maintain the heartbeat of a patient. Sodium-potassium pump helps to maintain
the contraction and relaxation of the muscle, balancing the pH value in the cells,
maintaining the body temperature, etc.

Harmful Effects of Mercury

Mercury poisoning is also known as hydrargyria or mercurialism. It is a type
of metal poisoning and the medical condition caused by exposure to mercury or its
compounds. Mercury (Hg) is a liquid metal. Naturally it is present in air, water and
soil in different forms. Elemental mercury and organic mercury compounds (methyl
mercury) are the major substances that affect human health. The main route of
exposure for elemental mercury is by inhalation of the vapour. Mercury may have
toxic effects on the nervous system, digestive system and immune system. It also has
adverse effects on lungs, kidneys, skin and eyes. Exposure to mercury even in little
concentration may cause serious health problems. It is a threat to the development
of a child in the utero and early life. Some of the health effects caused by short-term
exposure to high level mercury vapour are cough, sore throat, shortness of breath,
chest pain, nausea, vomiting, diarrhoea, increase in blood pressure or heart rate,
eye irritation, vision problems, etc. Similarly, long term exposure to mercury causes
anxiety, anorexia, sleeping problem, tremors, change in vision, change in hearing, etc.

Harmful Effects of Lead
Lead is a naturally occurring toxic metal found in the Earth’s crust. Its widespread

use has resulted in extensive environmental contamination, human exposure and
significant public health problems in many parts of the world. Lead is also used in
many products like pigments, paints, solder, stained glass, crystal vessels, ammunition,
ceramic glazes, jewelry, toys, in some cosmetics and traditional medicines. Drinking
water delivered through lead pipes or pipes joined with lead solder may contain lead.
Young children are particularly susceptible to the toxic effects of lead. They can suffer
profound and permanent adverse health effects, particularly the slow development of
the brain and nervous system. Lead also causes long-term harms to adults including the
risk of high blood pressure and kidney damage. Exposure of pregnant women to high
level of lead can cause miscarriage, stillbirth, premature birth, low birth weight, etc.

New Creative Science, Class 9 | 199

ANSWER WRITING SKILLS

1. How do metals occur in nature?
Ü Least reactive metals like gold and platinum are found in free state. Moderately

reactive metals are found in combined state as oxides, sulphides or carbonates.
Highly reactive metals are never found in the Free State.

2. Given an example of metal which
i) is a liquid at the room temperature
ii) can be easily cut with a knife
iii) is the best conductor of heat.
iv) is the poorest conductor of heat

Ü i) Liquid metal is mercury (Hg)
ii) Alkali metals like Lithium (Li), Sodium (Na), Potassium (K), etc. can be cut
with a knife.
iii) Silver (Ag) is the best conductor of heat
iv) Lead (Pb) is the poorest conductor of heat.

3. Explain the meaning of malleable and ductile.
Ü Metals are malleable because they can be beaten into thin sheets. Silver and gold

are the most malleable metals. They are ductile because they can be drawn into
wires after heating. Gold and silver are the most ductile metals. Gold is so ductile
that one gram of good can be drawn into a wire of about 2 kilometre.

4. Which metals do not corrode and why?
Ü Metals such as silver (Ag), gold (Au) and platinum (Pt) do not corrode because

they are very less reactive in nature.

5. State two ways to prevent the rusting of iron.
Ü Two methods used to prevent the rusting of iron are:

i) Galvanization

ii) Formation of alloy with nickel and chromium

6. Name three metals which are found in nature in Free State.
Ü Gold (Au), Silver (Ag) and Platinum (Pt) are the least reactive metals. Hence,

they occur in the nature in free form.

200 | Metals

SUMMARY

” Metals are the elements which are electropositive in nature, malleable, ductile
and good conductors of heat and electricity.

” The elements which are electronegative in nature, non-conductors of heat and
electricity, non-malleable and non-ductile in nature and do not possess luster
are called non-metals.

” 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.

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

” The essential mineral elements that are needed by the body in higher
concentration are called macro elements (Ca, Mg, Na, K).

” Those elements that are required by the body in trace amount are called
micronutrients (Fe, Zn, Mn, Cu, I, F, V, Mo, Se, Co, Ni, Si). All these elements
are known as biological inorganic elements.

” The sodium-potassium pump is an important mechanism in a human body in
which sodium and potassium ions move in and out of the cells to maintain the
electric impulses.

” A pacemaker is a simple kind of battery which is implanted in the chest of
a human body and provides electrical charge through its two small wires to
maintain the heartbeat of a patient.

EXERCISE

1. Define the following terms with examples.

(a) Metals (b) Non-metals (c) Metalloids
(f) Micro elements
(d) Alloys (e) Rusting

(g) Metallic bond (h) Electrons sea

2. What is the meaning of malleable and ductile?

3. What are metalloids? Give any two examples.

4. Copper is used to make an electric wire. Why?

5. Write four differences between physical properties of metals and non-metals.

New Creative Science, Class 9 | 201

6. What are alloys? Give any two examples.
7. Pure iron is not used to make utensils. Why?
8. Write three differences between chemical properties of metals and non-metals.
9. What is meant by rusting? Show the reaction.
10. What is meant by corrosion?
11. Metals are electropositive in nature. Why?
12. Why are alloys formed?
13. Metals are used to make cooking utensils. Why?
14. Define metalloids with two examples.
15. What do you mean by the rusting of iron? How can we prevent it?
16. Silver, gold and platinum are present freely in nature. Why?
17. What is a metallic bond? Explain ductile, malleable and lustrous properties of metal on

the basis of a metallic bond.
18. Describe the role of metals in organisms.
19. Explain the role of zinc in the human body.
20. Explain the importance of sodium-potassium ions in the human body.
21. What is a sodium-potassium pump? Describe the use of a pacemaker.
22. Explain the harmful effects of mercury and lead in the human body.

A

B GLOSSARY
C

Malleable : that can be converted into thin sheet
Ductile : that can be converted into thin and long wires
Rust : oxidized compound of iron
Semen : the liquid where sperms are present
Enzyme : the biological catalyst
Alloy : the homogenous mixture of two or more metals



202 | Metals

UNIT

13 CARBON AND ITS COMPOUNDS

About the Scientist Introduction

Edmond Halley Take a burning candle and put a piece of cardboard
just above the flame. After sometime we will see a black
Edmond (or Edmund) coloured spot on the cardboard. Can you guess the
Halley’s father was also chemical nature of this black spot or shoot present on the
called Edmond (or Edmund) cardboard? Yes, it is carbon. The name carbon is derived
Halley. He came from a from the Latin word, carbo. It means the black rock or
Derbyshire family and was shoot. Carbon is one of the most important and widely
a wealthy soap-maker in distributed non-metallic elements. The symbol of carbon is
London at a time when the ‘C’. It exists in both living and non-living things. The body
use of soap was spreading of animals and plants contain carbon in different forms,
throughout Europe. There is like glucose, protein, vitamin, etc. Plastics, detergents,
some confusion over both the dyes, drugs, etc. also contain carbon. In the atmosphere,
date and the year of Halley’s carbon is also present in different compounds like carbon
birth. The confusion over monoxide, carbon dioxide, etc.
the date is simply due to
the change in calendar (29 Catenation property of carbon
October by the calendar of
his time). The confusion over When one kind of many atoms combine together to
the year is less easy to decide, give a long chain, it is called catenation property.
but we take 1656 which
Halley himself claimed as Carbon also has this special property to make a long
the year of his birth. chain of carbon. As a result of this property of carbon,
there is possibility of diversity of organic compounds in
the nature. For example, glucose, protein, vitamin, plastics,
detergents, dyes, drugs, etc. During the formation of these
compounds, carbon can form long straight chains or
branched chains or closed rings. To study these carbonic
compounds, there is a separate branch of chemistry which
is known as organic chemistry. Although, more than one
hundred fourteen elements are discovered till today the
compounds formed from these elements are quite less
than the compounds formed by carbon alone. This is only
possible due to the catenation property of carbon.

New Creative Science, Class 9 | 203

ACTIVITY

Objective
To demonstrate that soot contains carb

Materials required
Aluminium foil, candle, match stick

Procedure
i) Lit a candle and place over a plane surface.
ii) Place a shiny aluminium foil over the lighted candle and observe it.

Observation
The shiny aluminium foil gets coated with black powder, which is called soot. It is a form of carbon.

Conclusion
The black coloured soot contains small particles of carbon.

QUESTIONS >>

# What do you mean by the catenation property of carbon? Explain it with an example.
# Describe about the occurrence of carbon.
# Explain with an activity that soot contains carbon.

Structure of carbon

Symbol of carbon =C

Atomic mass = 12

Atomic number =6 6n
6p
Electronic configuration = 2, 4
Structure of carbon atom
Valency =4

Bonding nature of carbon 0n 0n H
1p 1p HC H
Carbon has six electrons, six
protons and six electrons. According 6n 0n H
to the 2n2 formula, the second shell 6p 1p Methane
of carbon has four electrons. Due to
the presence of these four electrons, 0n
carbon completes it octet either by 1p
gaining or losing or by sharing these
Molecular structure of methane
204 | Carbon and Its Compounds shows the sharing of electrons

four electrons. Carbon having a very small atomic size and more electronegativity,
attracts electrons with strong force. Hence, there is no possibility of gaining and
losing of these four valence electrons. As a result, carbon shows the sharing of four
electrons with other four electrons of the same or different atoms to make the variety
of carbon containing compounds.

Sources of carbon

Carbon is a widely distributed non-metallic element. It is present in the
atmosphere, in living beings and in the earth’s crust. But the summary of some
sources are given in the list.
i) The natural organic compounds like glucose, protein, vitamin, oil, fat, urine,

medicines, silk, etc. contain carbon as one of the elements. From the process of
extraction, we can get carbon.
ii) Man-made chemical compounds and polymers like plastics, detergents, dyes,
drugs, papers, soap, etc. also contain carbon.
iii) Carbon is present as one of the constituents in the inorganic rocks and minerals.
From there, we can get carbon.
iv) Fossil fuels and natural gases like petrol, diesel, kerosene, coal, natural gas, etc.
are also the sources of carbon.
v) Oxides of carbon like carbon monoxide, carbon dioxide, etc. also contain carbon.

Allotropy of carbon

We can see diamond , graphite, coal, charcoal , lamp shoot, etc. These are forms
of carbon. They contain only one element that is carbon. Diamond is the hardest
known substance whereas graphite is a soft substance. But both diamond and graphite
contain carbon atoms only. Therefore, when an element has more than one physical
forms then it is called allotropy. Not only carbon but also some other elements like
sulphur, phosphorus, silicon, etc. also show some extent of allotropic nature in certain
limit. The different physical forms of an element are called allotropes.

All the allotropic forms of carbon are divided into following two groups.
i) Crystalline form: For example diamond, graphite and fullerenes.
ii) Amorphous form: For example coal, coke, charcoal, lamp black, etc.

Carbon

Crystalline Amorphous

Diamond Graphite Charcoal Coal Lamp black

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Diamond

Diamond is a transparent, colourless and
crystalline form of carbon. It is one of the purest
forms of carbon. It has only carbon atoms which
are tetrahedrally arranged to make crystalline solid.
Diamond is formed when pure carbon is subjected
to intense heat and pressure deep inside the earth.
It is separated from the rock. Now-a-days, artificial
diamonds are prepared by heating pure sugar,
charcoal and iron in a graphite crucible at a temperature of 3000°C in an electric
furnace. In Diamond, carbon atoms are linked together by covalent bonds. So, it is
represented by symbol ‘C’. Due to the presence of strong covalent bonding system,
diamond is the hardest and rigid substance on the earth’s surface.

Properties of Diamond
1. Diamond occurs in its native state in nature.
2. It has high density and a high melting point.
3. It is the non-conductor of heat and electricity.
4. It is the hardest natural substance.
5. It is a transparent and colourless solid.
6. It has a high refractive index.
7. It is about 3.5 times denser than water. So, its specific gravity is 3.5.
8. The diamond obtained from the earth surface is transparent to X-rays.
9. Man-made diamond is opaque towards X-rays.

Uses of Diamond
1. It is used in jewellers as it sparkles brilliantly in light.
2. It is used in cutting and drilling instruments.
3. Diamond filters harmful radiations. So, it is used to make radiation proof
windows in space crafts.
4. It is used to make high temperature thermometers.

Graphite Structure of graphite

Another crystalline form of carbon is graphite. Unlike
diamond, it is a soft solid with metallic luster and greasy
to touch. It is a good conductor of heat and electricity. It
is a black and opaque solid. It is made up of only carbon
atoms. So, its symbol is ‘C’. Graphite can be prepared by
heating coke at a high temperature of about 3000°C in an
electric furnace. In graphite, carbon atoms are arranged
in the form of layers of sheets of rings of six atoms. These
layers of carbon are extended in two dimensional patterns.
Each carbon atom in graphite is linked with other three

206 | Carbon and Its Compounds

carbon atoms making three covalent bonds. The fourth electron of carbon remains
free to make multiple bonds. This free electron of multiple bonds can be delocalized.

Properties of graphite
i) It occurs freely in nature.
ii) It is soft and greasy to touch.
iii) It is a black and opaque solid.
iv) It is a good conductor of heat and electricity.
v) Its melting point is 3670°C.
vi) It is 2.2 times denser than water.

Uses of graphite
i) It is used as a lubricant.
ii) Graphite rods are used in the battery and electric furnace.
iii) Graphite is used to make crucible, as it has a high melting point.
iv) Pencil lead is also made of graphite.
v) In nuclear reactors, it is used as a moderator.

Differences between diamond and graphite

Diamond Graphite

1. It is a transparent and colourless 1. It is a black and opaque solid.

solid. 2. It has a low refractive index.

2. It has a high refractive index. 3. It is a soft substance.

3. It is the hardest known substance. 4. It is a good conductor of electricity.

4. It is a bad conductor of electricity. 5. Its melting point is around 3670°C.

5. Its melting point is around 3820°C. 6. It has comparatively low density.

6. It has high density.

Fullerene or Bucky ball

Fullerene is a crystalline form of carbon.
It is a black and non-shiny allotrope of carbon.
Its specific gravity is 1.66 g/cm3. The pure bucky
ball is a bad conductor of electricity but it can
conduct heat. It turns into vapour at about
527°C and it is soluble in benzene.

MEMORY TIPS
 An adult man has 18.5 percentage of carbon.
 SiC (Silicon carbide is a man-made substance, which looks like diamond.
 Phosphorus burns easily when it comes in contact of air.

New Creative Science, Class 9 | 207

Charcoal

Carbon also occurs in amorphous forms. The examples of amorphous forms are
charcoal, coal, lamp black, etc. Charcoal is obtained from the destructive distillation
of various sources like wood, animal, sugar, etc. These sources is heated strongly in
the absence of air to get charcoal. On the basis of source materials, charcoal are of
three types. They are:

a) Wood charcoal: It is obtained from wood.
b) Animal charcoal: It is obtained from animals.
c) Sugar charcoal: It is obtained from glucose or canes sugar.

Coal

Another amorphous form of carbon is coal. It is the cheapest available fuel. It is
obtained from dead, decayed and decomposed parts of plants.

Lamp black

Lamp black contains about 98 to 99 percentage of carbon. It is prepared by heating
carbon rich materials like kerosene, turpentine, petroleum, oil, etc. with incomplete
supply of air. The soot is collected over damp blankets in chambers and obtained by
jerking.

Physical properties of carbon
1. Carbon occurs in nature in amorphous as well as in crystalline solid forms.
2. It is a non-metallic element.
3. Carbon shows different allotropes like diamond, graphite, charcoal, lamp
black coal etc.

Chemical properties of carbon

i) Combustion in air

In excess air, carbon gives carbon dioxide and in limited air it gives carbon
monoxide.

C + O2 Heat CO2 (Excess air)
2C + O2 Heat CO (Limited air)

ii) Reducing nature of carbon

Carbon can reduce metallic oxides in free metals. For example:

ZnO + C Heat Zn + CO

PbO + C Heat Pb + CO

208 | Carbon and Its Compounds

iii) Reaction with stem

Carbon reacts with water vapour to give water gas.

C + H2O CO + H2

iv) Reaction with metals

Carbon reacts with metals to give metal carbides. For example:

2C + Ca CaC2

(Calcium carbide)

Organic and Inorganic compounds

The carbon containing compounds which are obtained from the nature or
made by artificial methods are called organic compounds. Methane, ethane, alcohol,
protein, carbohydrates, fat, etc. are the examples of organic compounds. In ancient
time, people believed that all organic compounds were obtained from only living
organisms or from their parts. But in 1828 AD. F. Wohler of German chemist had
synthesized urea in the laboratory by heating ammonium cyanate. After that the old
concept of organic compounds had been changed.

NH4CNO D NH2 – CO – NH2

(Ammonium cyanate) (urea)

The branch of chemistry which deals with the organic compounds is called
organic chemistry.

There are many compounds which do not contain carbon atom. They contain
other elements other than carbon. They are called inorganic compounds. For example,
common salt, limestone, copper sulphate, lime water, etc. They are generally obtained
from minerals. The branch of chemistry which deals with the compounds of elements
other than carbon is called inorganic chemistry.

Differences between organic and inorganic compounds

Organic compounds Inorganic compounds

1. Organic compounds contain carbon 1. Inorganic compounds do not

atoms in their molecular structure. contain carbon atoms in their

molecular structure.

2. There is covalent bonding in the 2. There is electrovalent bonding in

organic compounds. the inorganic compounds.

3. They are generally combustible. 3. They are generally non-combustible.

New Creative Science, Class 9 | 209

4. They have a low melting and boiling 4. They have a high melting and boiling

point. point.

5. They are soluble in organic solvents. 5. They are soluble in inorganic
solvents.

6. They are insoluble in an inorganic 6. They are insoluble in organic

solvent. solvents.

7. They do not give opposite ions in 7. They give opposite ions in water.
water.

ANSWER WRITING SKILLS

1. CaCO3, Na2CO3, CO2 and CO contain carbon even they are inorganic
compounds, why ?

Ü In CaCO3, Na2CO3 the opposite ions are combined together as a result of
electrovalent bonding and there is no hydrogen atoms. So, they are inorganic
compounds. CO and CO2 have carbon atoms but no hydrogen atoms. Therefore,
traditionally they are called inorganic compounds.

2. What is water gas? Write its use.
Ü The mixture of carbon monoxide and hydrogen gas is called water gas. It is

obtained by the reaction of carbon with steam.
C + H2O → CO + H2

It is used in industries as a source of heat.

3. What do you mean by carbon monoxide poisoning?

Ü Carbon monoxide combines with haemoglobin in blood to form a cherry red
poisonous compound called carboxy haemoglobin. It inhibits the oxygen
carrying capacity of blood. This is known as carbon monoxide poisoning.

4. How do we make lead pencil from graphite? Describe in brief.

Ü For making lead pencils, graphite is crushed to powder and then mixed with
clay to form a paste. The paste is converted into thin sticks, which after drying
forms the core of a lead pencil.

SUMMARY

” Carbon is a solid non-metallic element.
” Carbon is present inside as well as outside the living body.
” Carbon occurs in crystalline as well as in amorphous forms.
” Diamond and graphite are the examples of crystalline forms of carbon.
” Carbon shows covalent bonding.
” Carbon shows catenation property. It means it makes a long chain of carbon

atoms.
” Diamond is the hardest known substance.

210 | Carbon and Its Compounds

” Diamond is a non-conductor, transparent and a colourless substance.
” Diamond is a precious crystalline solid.
” Graphite is a soft, non-transparent and colourless substance.
” Graphite is a good conductor of electricity.
” Carbon containing compounds are called organic compounds.
” Inorganic compounds do not contain carbon atoms.

EXERCISE

1. What are the different sources of carbon? Write in brief.
2. Write two differences between diamond and graphite
3. What is the allotropy nature of carbon? What are allotropes of carbon?
4. What do you mean by catenation property? Which elements show this property?
5. Explain the bonding nature of carbon.
6. Write down any three physical properties of carbon.
7. Write down three chemical properties of carbon.
8. Write two differences between organic and inorganic compounds.
9. What is organic chemistry? Name any four organic compounds.
10. Describe the structure of diamond with its three uses.
11. Describe the structure of graphite with its three uses.
12. Give reason that carbon dioxide is an inorganic compound.
13. Define inorganic chemistry with any four examples.
14. Give a suitable reason that diamond is a bad conductor of electricity whereas

graphite is a good conductor.
15. Write short notes on a fullereane/bucky ball.

16. Write down the balanced chemical equations.
(a) When carbon reacts with hot steam?
(b) When carbon reacts with calcium?
(c) When ammonium cyanate is heated?
(d) When carbon reacts with the stem of water?
(e) When lead oxide reacts with carbon?
(f) When carbon reacts with oxygen?

A

B GLOSSARY
C

Catenation : property of linking together

Allotropy : physical forms of elements

Carbo : black coloured substance



New Creative Science, Class 9 | 211

UNIT

14 WATER

About the Aquifer Introduction

Ogallala Aquifer Water is the most essential substance second to air. It
is the most abundant substance in the earth. About three
The Ogallala Aquifer is a fourths parts of the earth is covered with water. About 97%
shallow water table aquifer of water is present in the ocean. It has more percentage of
located beneath the Great salt. Thus, ocean water is not fit for drinking. Water is used
Plains in the United States. in every aspect of our life. For bathing, cooking, washing,
It is one of the world’s largest drinking, etc. Plants absorb food and minerals from the
aquifers. It underlies an area soil. To circulate these minerals and foods, they need water.
of approximately 174,000 Photosynthesis is not possible in the absence of water. Our
sq metre. It covers eight body contains about 70% of water. Apart from this, fruits
states of the USA. It was and vegetables have sufficient amount of water in them. The
named in 1898 by geologist watermelon contains 90% water. Therefore, water is a very
N. H. Darton from its type essential substance which cannot be replaced by any other
locality near the town of substances. In this unit, we will discuss about the sources of
Ogallala, Nebraska. About drinking water, its physical and chemical properties, types
27% of the irrigated land in of hardness of water and their effects.
the United States overlies the
aquifer. It yields about 30% Occurrence of water
of the ground water used
for irrigation in the United Water exists normally in the liquid state in seas, rivers,
States. streams, underground and lakes. In higher Himalayas and
southern and northern Polar Regions of the earth, water
occurs in solid state. It is in the form of ice and snow. In the
atmosphere, water is found in gaseous state as a vapour.
The presence of vapour in air makes it moist and humid.

Chemical composition of water

Chemically water is composed of hydrogen and
oxygen elements in the ratio of 2:1. Before the time of Henry
Cavendish, water was supposed to be an element. Later in
1783, Henry Cavendish, an English scientist showed that
water is the compound formed due to the combination of
two elements, viz; hydrogen and oxygen. The molecule of
water is represented by the molecular formula H2 O.

Hydrogen + Oxygen → Water molecule

2H2 + O2 → 2H2O

212 | Water

Water resources

1. Surface water resources

i. Sea and ocean

About 97 percentage of water is present in the sea
and ocean. It contains a large amount of salt. So, it is
unfit for drinking. It can be used to generate electricity.
But, it requires the presence of tides.

ii. River, spring, pond, lake, etc.

The main important water resources are rivers, springs, lakes, ponds, etc. We can
use this water for various purposes like drinking, irrigation, to generate electricity, to
run industries, for house hold activities, for fun, enjoyment, etc.

River Spring Lake Pond

2. Ground water resources

The water which is present below the earth’s
surface is called ground water. It is due to the
percolation of the rain water. The area above the
ground water has porous stones, silt, sand and
loosely packed soil. Such type of area is called an
aquifer. In an aquifer, a large amount of water
is stored. It is hundreds of times more abundant
than the water of rivers, lakes, ponds, springs,
etc. The water level below the earth’s surface is
called water table. Ground water is free from
dust, insects, etc. but it contains minerals, germs, gas, etc. Ground water moves from
a higher level to a lower level. Thus, sometimes it comes out from the springs, lakes,
etc.

Physical properties of water

i) In a pure state, water is a clear, colourless, tasteless and odourless liquid. In a big
mass like the ocean, water is bluish green in colour.

ii) Water is a bad conductor of heat and electricity.
iii) At 760 mm in Hg atmospheric pressure, water boils at 100°C and freezes at 0°C.

Ice has less density than water, so it floats on water.

New Creative Science, Class 9 | 213

iv) Water shows anomalous behaviour. When we heat

water from 0°C to 4°C, it starts to contract. The

contraction is highest at 4°C. Then, the expansion of

water takes place on heating further. Thus, water has

the highest density at 4°C.

v) Water can dissolve large number of substances, so it is

also known as universal solvent.

vi) It has highest specific heat capacity (4200 J/kg°C). capillary action of water

vii) Water is a neutral liquid.

viii) Water vapour present in air helps in the rusting of metal surfaces.

ix) Water is decomposed into hydrogen and oxygen gas by the process of electrolysis.

x) Water molecules get attracted to each other. It is called the cohesive property of

water. Similarly, they are also attracted to the other molecules. It is called the adhesive

property of water.

xi) Due to surface tension and the adhesive and cohesive property of water, the

water surface becomes concave.

xii) Between water and glass, there is strong adhesive property compared to the

cohesive property of water. Thus, the water surface becomes concave and moves

up in the thin capillary.

MEMORY TIPS

 In ice, there are large numbers of intermolecular spaces. In these spaces, there
remains air, so ice becomes lighter than water and floats on water surface.

 Mercury has a strong cohesive force of attraction, so its surface becomes
convex.

Chemical properties of water

i) Water is a bad conductor of electricity. But, if impurities are present in water, it gets
ionized into hydronium (H3O+) and hydroxyl ion (OH-) and conduct electricity.

2H2O → H3O+ + OH-
ii) Water has hydronium (H3O+) and hydroxyl (OH-) ions. So, it shows amphoteric

property. In base, water gives hydronium (H3O+) ion and in acid water gives
hydroxyl (OH-) ion.

NH3 + H2O → NH4+ + OH-
HCl + H2O → H3O+ + Cl-
iii) Water reacts with active metals like lithium, sodium, potassium, calcium, etc. to
liberate hydrogen gas.

2Li + 2H2O → 2LiOH + H2
Ca + 2H2O → Ca(OH)2 + H2

214 | Water

iv) Water reacts with metallic and non-metallic oxides, carbides, nitrides, etc. This is
called hydrolytic reaction.

Mg3N2 + 6H2O → 3Mg (OH)2 + 2NH3

Solvent property of water

i) Water has a high dielectric constant. It can dissolve most of the ionic chemical
compounds. It can dissolve sodium chloride, potassium chloride, potassium
nitrate, calcium chloride, ammonium chloride, etc. But, in some chemical
compounds, there is a strong force of attraction. So, water cannot dissolve such
chemical compounds. For example, silver chloride, barium sulphate, calcium
fluoride, etc.

ii) Water can dissolve polar covalent compounds like hydrochloric acid, sulphuric
acid, alcohol, urea, etc. In these compounds, there is polarity. These polarities are
attracted to the opposite poles of water as water is a polar molecule. As a result,
water can dissolve most of the polar covalent compounds.

iii) Water cannot dissolve nonpolar covalent compounds like methane, carbon tetra
chloride, etc.

Uses of water

i) Water is used for different kinds of household activities, like cooking, washing,
bathing, drinking, etc.

ii) It is used for the purpose of irrigation.
iii) It is used to run industries.
iv) It is used for the chemical reactions, jet cutting, to refine metals, oil, etc.
v) It is used to generate hydroelectricity.
vi) It is used for entertainment like rafting, boating, swimming, etc.
vii) It is used for fishing.

Types of water

While we bath or wash our clothes, sometimes we feel the soap producing lather
easily while sometimes it does not. When we use river water or stream water, we
need to use more soap to wash our clothes. If we use distilled or rain water, it is very
easy to use soap and to wash clothes. This is because water present in rivers and
streams produces less lather than the rain or distilled water. Depending upon the
amount of lather produced with soap, water is of two types.

1. Soft water
The water that produces lather with soap easily is known as soft water. Rain water

and distilled water are the examples of soft water. This water has very less impurities.
It does not contain dissolved calcium and magnesium sulphates, bicarbonates and
chlorides, as these salts make water hard.

New Creative Science, Class 9 | 215

2. Hard water

The water that does not produce lather with soap easily is called hard water. Very
little or no lather is produced by the hard water. River water, pond water, sea water,
etc. are the examples of hard water. This water contains various salts of calcium and
magnesium like bicarbonates, sulphates, chlorides, etc. The mineral water we drink
is hard water.

Hardness of water

The soluble salts of calcium and magnesium like magnesium sulphate (MgSO4),
magnesium bicarbonate [Mg(HCO3)2 ], magnesium chloride (MgCl2), calcium
bicarbonate [Ca (HCO3)2], calcium chloride (CaCl2), and calcium sulphate(CaSO4), etc.
are responsible to make water hard. Hardness of water is of two types.

i) Temporary hardness of water
ii) Permanent hardness of water

i) Temporary hardness of water

If water contains soluble salts of calcium and magnesium like calcium bicarbonate
[Ca(HCO3)2] and magnesium bicarbonate [Mg(HCO3)2 ], it is known as temporary
hardness of water. Thus, temporary hardness of water is caused by bicarbonates of
magnesium and calcium.

Removal of temporary hardness of water

Temporary hardness of water can be removed by the following methods.

a. By boiling
Temporary hardness of water is removed on boiling water. When water is heated,
the soluble salts like calcium and magnesium bicarbonates decompose into their
respective carbonates. This is shown below.

Calcium heated Calcium + + Carbon dioxide
bicarbonate → carbonate Water + CO2

Ca(HCO3)2 CaCO 3 + H 2O

Magnesium bicarbonate heated Magnesium carbonate + Water + Carbon
dioxide

Mg(HCO3)2 heated MgCO3 + H 2O + CO2

b. By treating with lime water {Ca(OH)2}

When we add lime in the hard water, the calcium and magnesium bicarbonates

change into their respective carbonates, which are not soluble in water. The chemical

reaction is as shown below.

216 | Water

Magnesium bicarbonate + Lime water heated Magnesium carbonate + Water +
Calcium carbonate

Mg(HCO3)2 + Ca(OH)2 heated MgCO3 + 2H2O + CaCO3

ii) Permanent hardness of water

The water becomes permanently hard if chlorides and sulphates of magnesium

and calcium are present in it. Salts causing permanent hardness of water are calcium

chloride (CaCl2), magnesium chloride (MgCl2), calcium sulphate (CaSO4) and
magnesium sulphate (MgSO4 ).

Removal of permanent hardness of water

Permanent hardness of water can be removed by the following ways.

a. By treating with sodium carbonate (Na2CO3)

When sodium carbonate is used in hard water, the sulphate and chloride salt of
magnesium and calcium change into their respective insoluble carbonates.

Calcium chloride + Sodium carbonate Calcium carbonate + Sodium chloride
CaCl2 (washing soda)
CaCO3 NaCl
(Na2CO3)

Magnesium + Sodium carbonate Magnesium carbonate + Sodium chloride
chloride (Na2CO3) MgCO3
MgCl2 NaCl

Calcium sulphate+ Sodium carbonate Calcium carbonate + Sodium sulphate
CaSO (Na2CO3)
4 CaCO3 Na2SO4

Magnesium + Sodium carbonate Magnesium carbonate + Sodium sulphate
sulphate
(Na CO ) MgCO3 Na2SO4
MgSO4 23

b. By Permutit process (ion exchange process)

Permutit is the synthesized zeolite.
Zeolite is formed from the oxides
of sodium, aluminium, sand and
water. Gravel is packed on the base of
permutit. On passing water from the
layer of permutit through gravel packet
in a tower, the permutit reacts with
magnesium and calcium sulphates
and chlorides to form their respective
permutits like calcium permutit and
magnesium permutit. After the formation of calcium and magnesium permutit, the
permutit becomes inactive. This is activated by using sodium chloride (salt) solution.

New Creative Science, Class 9 | 217

The chemical reactions can be shown as,
Calcium salt + Sodium permutit → Calcium permutit + Sodium salt
Magnesium salt + Sodium permutit → Magnesium permutit+ Sodium salt
Calcium permutit + Sodium chloride → Sodium permutit + Calcium chloride
Magnesium permutit + Sodium chloride → Sodium permutit + Magnesium chloride

Uses of hard water
i) Hard water is used for drinking purposes, e.g. mineral water.
ii) Beverages are prepared by using hard water.
iii) Calcium salts present in hard water help to make the bones strong.

Drawbacks of hard water
i) Hard water decreases the quality and colour of clothes and makes them
dull.
ii) The hard insoluble solid is formed on the base of water boiling utensils. This
decreases the lifespan of the boiler.

ANSWER WRITING SKILLS

1. Hard water does not produce lather with soap. Why?
Ü Hard water contains soluble salts of calcium and magnesium like calcium

bicarbonate, magnesium bicarbonate, calcium sulphate, magnesium sulphate,
calcium chloride and magnesium chloride. These soluble salts decrease the effect
of soap to produce lather. So, hard water does not produce lather with soap.

2. What happens when lime water reacts with calcium and magnesium bicarbonates?
Ü When lime water reacts with calcium and magnesium bicarbonates, these soluble

salts get converted into insoluble salt resulting in their respective carbonates and
water.

3. What is water jet cutter?
Ü When we pass water with high pressure, it can cut metals, wood, rubber, etc. It

is known as water jet cutter.

4. How is it possible to move water strider insects over the surface of water?
Ü Due to surface tension, water makes a thin elastic membrane over its surface. As

a result, water strider insects can move over the surface of water.

5. It is not possible for living beings to live in the Dead Sea. Why?
Ü Water of Dead Sea has more than 37.5 percentage of salt. Thus, in this water, it

is not possible for live living beings to live. Its density is so high density that no
man sinks there.

218 | Water

SUMMARY

” Water is the most abundant substance in the earth.
” The human body contains 70% of water by volume.
” Water exists in all three states: solid (ice), liquid (water) and gas (water vapour)
” Water is a compound of hydrogen and oxygen. Two parts of hydrogen and

one part of oxygen combine to form water.
” Water is a universal solvent, which has the highest density at 4°C.
” Hard water does not produce lather easily with soap but soft water easily

produces lather with soap.
” Treating with lime water (calcium hydroxide) and boiling removes the

temporary hardness of water.
” Sodium carbonate (washing soda) and permutit process is used to remove the

permanent hardness of water.
” Water is used for various household activities, irrigation, entertainment,

industries, generating hydroelectricity, etc.

EXERCISE

1. Fill in the blanks.

(a) _________ of the earth is covered with water.

(b) Water is a_____________ solvent.

(c) Two parts of ___________ combine with one part of ____________to form water.

(d) Water boils at ___________ at normal pressure.

(e) Beer is made from _____________ water.

2. State whether the following statements are true or false.

(a) Water is an element.

(b) Water vapour in air makes it humid.

(c) Water is a neutral liquid.

(d) Calcium bicarbonate and calcium sulphate are present in soft water.

(e) Permutit method is used to convert hard water into soft water.

3. Match the following.

Group A Group B
Mineral water
Distilled water soft water
Calcium bicarbonate
Calcium sulphate Ca(HCO3)2
Lime water Ca(OH)2
hard water

CaSO4

New Creative Science, Class 9 | 219

4. Differentiate between:
(a) Hard water and soft water.
(b) Temporary hardness and permanent hardness.

5. Answer the following questions.
(a) How is water molecule formed? Show it with a chemical reaction.
(b) Why is water known as a universal solvent?
(c) What types of water are based on the presence or absence of soluble salts?
(d) Define soft and hard water with examples.
(e) Name the soluble salts that cause the hardness of water.
(f) List the uses and drawbacks of hard water.
(g) Write down the uses of water?
(h) Discuss the process to remove the temporary hardness of water.
(i) What is washing soda? How does it remove the permanent hardness of water?
(j) Discuss the physical properties of water.
(k) What are the sources of surface and ground water?
(l) Describe the chemical properties of water.
(m) Explain the solvent property of water.
(n) Name the chemical compounds with formula which are present in hard water.

A

B GLOSSARY
C

Essential : required / necessary
Abundant : existing in large quantity
Su cient : as needed, as required
Drawback : disadvantage or problem

Aquifer : the surface of land with rocks, sand and soil which store water

Cohesive property : the attractive property among the same molecules

Adhesive property : the attractive property among the di erent molecules



220 | Water

UNIT

15 CHEMICAL FERTILIZERS USED IN
AGRICULTURE

About the Scientist Introduction

Friedrich Wohler Farmers use different chemical substances in their
field. These chemical substances are used to grow and
Urea was first discovered yield more crops. If farmers do not use these chemical
in human urine by H.M. substances, the production of the crops gets affected badly,
Rouelle in 1773. which does not compensate the growing population of the
world. These chemical substances are called fertilizers.
It was synthesized in 1828 Basically, there are two types of fertilizers; they are organic
by Friedrich Wohler. It was fertilizers or natural fertilizers and inorganic fertilizers
the first or chemical fertilizers. In this unit, we will discuss about
different types of organic and chemical fertilizers, their
organic compound to be sources and uses.
synthesized from inorganic
starting materials. Fertilizers

The Wöhler synthesis Fertilizers are those water soluble chemical or organic
substances, which contain essential nutrients for the fast
was the conversion of growing of plants. They help plants, fruits and vegetables
for their healthy growth and production. Plants need
ammonium cyanate two types of nutrients for their healthy growth. They are
macro nutrients and micro nutrients. Macro nutrients
into urea. This chemical include nitrogen, phosphorus and potassium whereas
micro nutrients include boron, magnesium, iron, zinc,
reaction was discovered sulphur, etc. Regular production of different types of
crops, fruits and vegetables decreases these nutrients in
in 1828 by Friedrich soil. Thus, different types of fertilizers help to maintain
the fertility (nutritive elements) of the soil. They are used
Wöhler. It was an attempt in the soil for plants, vegetables, fruits, etc. There are two
types of fertilizers.
to synthesize ammonium
1. Chemical fertilizers
cyanate. It is considered the 2. Organic fertilizers

starting point of modern 1. Chemical fertilizers

organic chemistry. Chemical fertilizers are those water soluble chemical
substances which are prepared through chemical reactions.

New Creative Science, Class 9 | 221

They are also called inorganic fertilizers. These inorganic fertilizers contain mainly
nitrogen, phosphorus and potassium elements. Plants need these elements for their
growth, development and seed production. We can divide chemical fertilizers into
three groups on the basis of elements containing in them.

a. Nitrogenous fertilizers

In these fertilizers, nitrogen (N) is present as a
chief element. For example;

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

b. Potassium containing fertilizers

These fertilizers mainly supply potassium to plants. For example,

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

c. Phophrus containing fertilizers

These fertilizers contain mainly phosphorus elements. For example,
i. Bone meal
ii. Triple super phosphate 3Ca(H2PO4)2
iii. Ammonium phosphate (NH4)3 PO4
iv. Calcium super phosphate Ca (H2PO4)2 2CaSO4

2. Organic fertilizers

Those fertilizers which are obtained from the decayed and decomposed parts

of plants, animals or their waste products are called organic fertilizers. They are

also called natural fertilizers or manure. They are obtained from the natural process.

Organic fertilizers are very suitable for crops and plants. Because they supply all the

essential nutritive elements to the plants. Besides, there is no side effect. There are

two types of organic fertilizers.
i) Green organic fertilizer: Green organic fertilizer is obtained from small, soft
and delicate plants. When green plants are grown, ploughed and mixed in
the soil to provide essential nutrients to plants and crops, this is called green
organic fertilizer.
ii) Animal organic manure: Animal organic fertilizer is obtained from dead
animals. When animals die, they are buried under the soil. After a few
months, the dead body gets decayed and decomposed with the help of fungi
and bacteria. This type of fertilizer does not contain nitrogen, phosphorus
and potassium. Thus, it is better to use animal organic fertilizer by mixing
inorganic fertilizer.

222 | Chemical Fertilizers Used in Agriculture

iii) Compost manure: Compost manure is a
natural fertilizer which is prepared from
dead, decayed and decomposed parts
of animals and plants or their waste
products. To prepare compost manure,
mixture of dead plants, animals or their
waste products are kept in the pit of soil.
Sometimes, lime is also added to it. After
3 to 5 months, due to microorganisms, it
gets decomposed and manure is ready to use. It increases the fertility of the
soil but it has a low concentration of Nitrogen, Phosphorus and Potassium.

Advantages of organic fertilizers
i) Organic fertilizers store water in the soil and increase the fertility of the soil.

ii) They don’t pollute air, water and soil and also minimize soil erosion.

iii) Due to organic fertilizers, the products have no side effect on humans and
animals.

iv) Even with the long term use of organic fertilizers, they do not destroy the
soil composition.

v) Due to organic fertilizers, vegetables, fruits, crops, etc. become tasty and healthy.

Disadvantages of organic fertilizers
i) Organic fertilizers don’t supply enough nitrogen, phosphorus and potassium
to the growing plants.

ii) They are less soluble in water.

iii) They are very difficult to transport form one place to another.

iv) They produce a foul smell in the surroundings.

v) They produce methane gas during their manufacturing. This gas is
responsible for the greenhouse effect.

Differences between organic and chemical fertilizers

Organic fertilizers Chemical fertilizers

1. Organic fertilizers are called natural 1. These fertilizers are called

manure. artificial fertilizers.

2. They don’t supply enough nitrogen, 2. They contain enough nitrogen,

phosphorus and potassium to the growing phosphorus and potassium

plants. elements.

3. They are prepared from plants, animals 3. They are prepared through

or natural waste. chemical process.

4. They don’t pollute air, water and soil. 4. They pollute air, water and soil.

5. Plants absorb them very slowly. 5. Plants absorb them very quickly.

6. The products have no side effect on 6. The products create side effects on

humans and animals. body human beings and animals.

New Creative Science, Class 9 | 223

Significance of Nitrogen (N), Potassium (P) and Phosphorous
in fertilizers

Nitrogen

Nitrogen is one of the most important and essential nutrients for plants and
crops. It fulfils the following needs of the plants.

i. It helps in the fast growth of plants.
ii. It helps in the formation of protein, protoplasm and chlorophyll in plants.
iii. It helps to develop more flowers, fruits and seeds.

The deficiency of nitrogen in plants makes leaves yellow, slow growth of the
plant and its size and a little production of flowers, fruits and seeds.

Potassium
i. With the help of potassium fertilizers, plants make food through the
photosynthesis process.
ii. It also helps to synthesize protein, fat, sugar, cell division, growth of leaves,
flowers and fruits, etc. in plants.
iii. It helps to resist different types of diseases.

The deficiency of potassium in plants reduces the production of food in plants. Its
deficiency decreases the production of protein, fat, sugar, etc. in plants. The growth of
leaves, flowers, fruits, etc. will be very less. Its deficiency also causes decrease in the
disease resistant capacity.

Phosphorus
i. The roots of plants are developed with the help of this fertilizer.
ii. With the help of phosphorus, ripening of fruits and healthy development of seeds
take place.
iii. Cell division and development of buds are done in plants by the phosphorus
elements

The deficiency of phosphorus reduces the development of roots, buds and
stems in plants. The ripening of fruits and seeds, is retarded due to the deficiency of
phosphorus. Its deficiency also causes decrease in the disease resistant capacity.

Three groups of fertilizer

Fertilizers can be divided into three groups according to the number of basic
nutrients supplied.

(a) Single fertilizers

When the fertilizers supply only one basic nutrient out of three basic nutrients
i.e. nitrogen, phosphorus or potassium are called single fertilizers. Calcium nitrate,
potassium sulphate, potassium chloride are its examples.

224 | Chemical Fertilizers Used in Agriculture

(b) Mixed fertilizers
These fertilizers supply more than one basic nutrient. Example: potassium

nitrate, ammonium phosphate, etc.

(c) Complete fertilizers (NPK fertilizer)
Those fertilizers which supply three basic nutrients i.e. nitrogen, phosphorus

and potassium are called complete fertilizers. They are also called NPK fertilizer.

Advantages of using chemical fertilizers

i) Chemical fertilizers are easy to store, transport and use.
ii) They are highly soluble in water. Therefore, plants can absorb them easily.
iii) Chemical fertilizers are rich in certain elements like nitrogen, phosphorus,

potassium, etc.
iv) They enhance the fertility of the soil.

Disadvantages of using fertilizers

The main disadvantages are listed below.
i) Chemical fertilizers pollute air, water and soil.
ii) Due to chemical fertilizers, the products have side effects on humans and
animals.
iii) Long term use of organic fertilizers destroys the soil composition.
iv) They make the soil acidic or basic.
v) Due to chemical fertilizers, the vegetables, fruits, crops, etc. do not have any
taste.

Effects of chemical fertilizers on the environment

Nowadays due to the rapid growth of population, fast and unorganized
urbanization, there is a shortage of natural products in the market. People are trying
to earn money within a short period. For this, they are using such types of fertilizers
which help in the fast and higher production of crops, vegetables and fruits. The use of
excessive chemical fertilizers leads to air, water and soil pollution. When nitrogenous
fertilizers are mixed in water sources, they in the help unusual and rapid growth of
aquatic plants. These plants use-up the oxygen mixed in water. As a result, there is a
shortage of oxygen in water. Thus, aquatic animals die due to the lack of oxygen. If
small children drink nitrogen-containing water, their growth stops and they become
become dwarfs.

MEMORY TIPS

In Fewa lake of Pokhara, there is high deposition of nitrogenous fertilizers. Due to
this reason, different kinds of aquatic plants are growing rapidly.

New Creative Science, Class 9 | 225

Precautions while using fertilizers
i) We should take training from the J.T.A on how to use fertilizers.
ii) Before using fertilizers, the soil must be tested.
iii) Fertilizers should not be used randomly and on excessive amount.
iv) They should be used properly, in proper time as well as in appropriate
quantity.
v) Nitrogenous fertilizers should be used very carefully and should not be kept in
wooden dust, coal, dry leaves or fuel because they have easy burning feature.
vi) Overuse of fertilizers damages plants.
vii) We should use a mask, gloves while using fertilizers.
viii) We should keep them away from the reach of children, animals, etc.
ix) We should not keep them near edible things, foods or water.
x) We should change our dress after using fertilizers. Hands, the mouth and
legs should be washed with soap properly.

ANSWER WRITING SKILLS

1. It is better to use organic fertilizers instead of chemical fertilizers in the field.
Why?

Ü Organic fertilizers don’t pollute air, water and soil. Due to organic fertilizers, the
products have no side effect on humans and animals. Even with the long term
use of organic fertilizers, they do not destroy the soil composition. Vegetables,
fruits, crops, etc. grown in organic fertilizers become tasty and healthy. Thus, the
use of organic fertilizers is better than that of chemical fertilizers.

2. What should be done to reduce the acidity and basicity of the soil?
Ü To reduce the acidity, we use agricultural lime (calcium hydroxide). Similarly, to

reduce the basicity, we use calcium sulphate, calcium chloride, sulphuric acid,
hydrochloric acid, urea, etc.

3. How do organic fertilizers help to increase the greenhouse effect?
Ü Organic fertilizers are obtained by the decomposition of dead bodies. During

their decomposition, methane gas is released. It is a greenhouse gas and it
increases the greenhouse effect.

4. What are the aerobic and anaerobic methods of decomposition?
Ü The decomposition of the dead bodies in the presence of oxygen is called aerobic

decomposition. Similarly, the decomposition of the dead bodies in the absence of
oxygen is called anaerobic decomposition.

SUMMARY

” Fertilizers are those water soluble chemical or organic substances which
contain the essential nutrients for growing plants.

” Chemical fertilizers are those water soluble chemical substances which are
prepared through chemical reactions. They are also called inorganic fertilizers.

226 | Chemical Fertilizers Used in Agriculture

” Those fertilizers which are obtained from the decayed and decomposed parts
of plants, animals or their waste products are called organic fertilizers. They
are also called natural fertilizers or manure.

” When green plants are grown, ploughed and mixed in the soil to provide
essential nutrients to plants and crops, this is called green organic fertilizer.

” Animal organic fertilizer is obtained from dead animals.

” Compost manure is a natural fertilizer which is prepared from dead, decayed
and decomposed parts of animals and plants or their waste products.

” Those fertilizers which supply three basic nutrients i.e. nitrogen, phosphorus,
and potassium are called complete fertilizers or NPK fertilizers.

EXERCISE

1. Define fertilizers? Why is it necessary to use fertilizers?
2. Classify fertilizers with examples.
3. What are organic fertilizers?
4. What are inorganic fertilizers or chemical fertilizers? Write any three examples.
5. What are green organic fertilizers, animal organic fertilizers and compost fertilizers?
6. Write down any three advantages and three disadvantages of organic fertilizers.
7. Write down any three advantages and three disadvantages of chemical fertilizers.
8. What are single, double and mixed fertilizers?
9. What is NPK fertilizer? Why is it called a complete fertilizer?
10. Write down any three differences between organic and chemical fertilizers.
11. Describe the manufacturing of the compost manure?
12. Write down any three examples of nitrogenous, phosphorus and potassium containing

fertilizers.

13. Write down the importance of nitrogen, phosphorus, and potassium elements for the
growing plants.

14. What happens when there is lack of nitrogen, phosphorus, and potassium elements for
the growing plants?

15. Write down the effects of chemical fertilizers on the environment.
16. What precautions should be taken while using chemical fertilizers?

A

B GLOSSARY
C

Organic fertilizer : the fertilizer which is obtained from the decayed and decomposed parts of

the animals and plants

NPK : the fertilizer which contains nitrogen, phosphorus and potassium

Complete fertilizers : the fertilizers which supply all the required elements

Nitrogenous : the chemical which contains nitrogen

Bone meal : the ash of bone is called bone meal



New Creative Science, Class 9 | 227

UNIT

16 CLASSIFICATION OF LIVING BEINGS

About the Scientist Introduction

Carolus Linnaeus There are a number of plants and animals around us.
(1707-1778) They are different from one another in one or more aspects.
It is impossible to study each of these species at their
Carolus Linnaeus (Karl individual level. Due to it, plants and animals are classified
Von Linne) was born in into different groups so that they can be easily studied.
Sweden and was a doctor Thus, the classification can be defined as the process of
by profession. He was grouping organisms into different groups according to
interested in the study of their similarities and differences.
plants. At the age of 22,
he published his first paper Carolus Von Linnaeus was the first person to divide
on plants. While serving the whole living world into two kingdoms. They are the
as a personal physician plant kingdom and the animal kingdom. He was the
of a wealthy government first person to give the scientific names of the organisms.
official, he studied the Hence, Carolus Von Linnaeus is also known as the father
diversity of plants in his of taxonomy.
employer’s garden. Later,
he published 14 papers and Taxonomy
also brought out the famous
book Systemae Nature from Taxonomy is the branch of biology which deals with
which all fundamental the identification, nomenclature and the classification of
taxonomical researches have living beings. Carolus Linnnaeus introduced the Binomial
taken off. His system of System of Nomenclature in 1758 A.D.
classification was a simple
scheme for arranging plants Binominal System of Nomenclature
so as to be able to identify
them again. The way of giving scientific names to living organisms
is called nomenclature.

The system of giving two names of each organism i.e.
a generic name and a specific name is called the Binomial
System of Nomenclature. The first name (generic name)
must be started with a capital letter and the second name
(special name) must be started with a small letter. Both of
the names should be typed in the italic font or should be
underlined while hand written. Some of the examples are
given below.

228 | Classification of Living Beings

English name Scientific name
Man Homo sapiens
Mustard Brassica campestris
Mushroom Agaricus campestris
Frog Rana tigrina
Maize Zea mays
Potato Solanum tuberosum
Cobra Naja naja
Tiger Panthera tigris

Categories of classification

In the process of classification, organisms are placed into different groups or
categories known as taxa. First, the organisms are grouped into kingdoms which are
further classified into divisions or phyla, division into sub-divisions, sub-division
into classes, class into orders, order into families, family into genus and finally genera
into species. The characters of the living organisms become more and more similar as
we move from the kingdom towards the species.

Genus

The group of closely related species is called genus. For example: Panthera is a
genus for lion, tiger, cat, etc.

Species

It is a group of closely related individuals which are similar to each other in many
aspects like anatomy, physiology and behaviour. They can be interbred to produce
the fertile progeny.

Importance of classification

i) It makes the study of living organisms easy, fast and scientific.
ii) It helps to provide the scientific names for all living beings.
iii) It helps to understand evolution.
iv) It provides the relationship among organisms.
v) It brings uniformity in the study of living organisms all over the world.

QUESTIONS >>
# Why is the classification of living organisms necessary?
# Who is known as the father of Taxonomy and why?

New Creative Science, Class 9 | 229

Five kingdom system of classification

An American taxonomist R.H. Whittaker proposed the most recent classification
of organisms in 1969 AD. It is popularly known as ‘five kingdom system of
classification’. According to this classification, the five kingdoms are:

(i) Monera (ii) Protista (iii) Fungi (iv) Plantae (v) Animalia

Kingdom Monera

In the Monera kingdom, there are only unicellular prokaryotic organisms. In
these organisms, there is a cell without a well-developed nucleus. In the nucleus
there is only DNA (Deoxy ribonucleic acid). These organisms may be autotrophs and
heterotrophs. For examples, bacteria, azobacter, blue green algae, etc.

Kingdom Protista

In the Protista kingdom, there are only unicellular eukaryotic organisms. In
these organisms, there is a cell with a well-developed nucleus. These organisms may
be autotrophs and heterotrophs. For examples, amoeba, paramecium, euglena, etc.

Characteristics of Protista
i) They are unicellular, microscopic organisms, which may be free living or

parasitic.

ii) They are mainly found in water and moist places.

iii) Respiration and excretion take place through the general body surface.

iv) Locomotion takes place either by cilia (Paramecium), special structures like
flagella (Euglena) and pseudopodia (Amoeba). Some of them do not have any
locomotory organs (Plasmodium).

v) Some of them cause different types of diseases.
Example: Entamoeba causes cholera and dysentery, plasmodium causes malaria,
trypnosoma causes sleeping sickness, etc.

Paramecium Amoeba Euglena Entamoeba
230 | Classification of Living Beings

MEMORY TIPS

Euglena is a single celled animal which has a chloroplast. So, it can prepare its own
food.

Kingdom Fungi

In the kingdom fungi, there are unicellular and multicellular eukaryotic
organisms, which do not have chlorophyll in their cells. They have a thallus body.
They are heterotrophic organisms. They mostly grow in dead and decayed organic
matters. Some major characteristics of the kingdom fungi are given below:
i) They are found in moist and dark places, where organic matters are found in

abundance.
ii) They do not have chlorophyll. So, they cannot make their own food. Due to this,

they are also known as heterotrophs.
iii) Their cell wall is made up of fungus cellulose or chitin.
iv) They store their food in the form of glycogen.
v) They are not green in colour.
vi) They may be unicellular or multicellular.

Example: mushroom, mucor, yeast, penicillium, etc.

Yeast Mucor Mushroom

Kingdom Plantae

All kinds of multicellular autotrophic plants are kept in the kingdom Plantae.
They are green coloured plants as they have chlorophyll in their cells. For example,
mustard, maize, pea, pinus, cycas, etc.

Kingdom Animalia

All kinds of multicellular heterotrophic animals are kept in the kingdom
animalia. For example, man, cow, frog, fish, etc.

Flowering and non-flowering plants

The plants which do not bear flowers and seeds are called cryptogams or non-
flowering plants. They are the simplest and primitive plants. They contain chlorophyll

New Creative Science, Class 9 | 231

in their cells. Therefore, they are autotrophs in nature. For example, spirogyra, moss,
riccia, fern, etc. Similarly, those plants which bear flowers and seeds are called
phanerogams or flowering plants. They are more advanced than cryptogams. For
example, maize, wheat, cycas, pinus, etc.

Classification of plants

The kingdom plantae is divided into three divisions. They are:
(1) Algae (2) Bryophyta (3) Trachaeophyta

MEMORY TIPS

Thallophyta: They are primitive plants. Their root, stem and leaf are not clearly
differentiated i.e. their plant body is thallus. They may or may not contain
chlorophyll.

1) Division: Algae (L- alga = seaweed)
i) They may be unicellular or multicellular.
ii) They are green in colour as they contain chlorophyll.
iii) They have chlorophyll in their body. So, they make their own food. Due to
this, algae are also known as autotrophs.
iv) Their cell wall is made up of cellulose.
v) They store their food materials in the form of starch.
vi) They are found in water or in moist places.
Example: volvox, spirogyra, chlamydomonas, anabaena, nostoc, ulothrix,
etc.

Spirogyra Volvox Chlamydomonas Ulothrix Nostoc

Differences between algae and fungi

S.N. Algae S.N. Fungi

i. They are found in well lighted i. They are found in dark places.

areas.

ii. They are autotrophs. ii. They are heterotrophs.

iii. They have chlorophyll. iii. They do not have chlorophyll.

iv. They store their food in the form of iv. They store their food in the form of

starch. glycogen.

232 | Classification of Living Beings

v. Their cell wall is made up of v. Their cell wall is made up of chitin.

cellulose. Example: mushroom, mucor, etc.

Example: spirogyra, volvox, etc.

MEMORY TIPS

Eicher (1883) has divided plant kingdom into two sub-kingdoms – cryptogams and
phanerogams.

QUESTIONS >>
# Why is chlamydomonas kept in the plant kingdom although it can move like an animal?

ACTIVITY

Keep a piece of bread in a warm and moist place for 2-3 days. After 2-3 days, observe the cottony
substance developed on the bread. Transfer the cottony substance on a clean glass slide and add
a drop of cotton blue indicator on it. Cover it with a cover slip after putting a drop of glycerin on it
and observe it under a microscope.

2) Division: Bryophyta (Gr, Bryon = a mass)

i) They grow in moist, cool and shady places.
ii) These plants are essentially terrestrial but they require water for every step

in their life cycle and for fertilization. So, they are also known as amphibian
plants.
iii) Their vascular tissues (xylem and phloem) are completely absent.
iv) They contain chlorophyll and produce their own food. Hence, they are
autotrophs.
v) Their main body part is green, flat and thallus. They remain attached to the
substratum by the hair like structures called rhizoids.
Examples: Riccia, Marchantia, Moss (Funaria), Anthocerous, etc.

Riccia Marchantia Moss Anthoceros

QUESTIONS >>
# Why are bryophytes also called amphibian plants?

New Creative Science, Class 9 | 233

3) Division: Tracheophyta

In this division, mostly there are well developed plants. In these plants, there is
well developed xylem and phloem. They are further divided into three sub-divisions.
They are:
a) Pteridophyta b) Gymnosperm c) Angiosperm

a) Sub- division: Pteridophyta (Gr- Pteron = feather, phyton = plant)
i) This division includes first vascular plants i.e. they have vascular tissues
(xylem and phloem) in their body.
ii) They are the most developed non-flowering plants.
iii) They have feather-like leaves.
iv) The plant body is completely differentiated into roots, stem and leaves.
v) They reproduce through spores.
vi) They have distinct alternation of generation.
Example: fern, lycopodium, horsetail, equisetum, azola, etc.

Fern Lycopodium Marsilea Equisetum

QUESTIONS >>
# Why are pteridophytes also called the most advanced cryptogams?

b) Sub- division: Gymnosperm (Gr- Gymno = naked, sperm = seed)

Gymnosperms have the following distinct characteristics:
i) They are vascular plants which produce naked seeds i.e. seeds are not

enclosed within the fruits.
ii) They do not bear fruit.
iii) They bear cones instead of flowers. So, they are also known as conifers.
iv) They form the evergreen forest.

234 | Classification of Living Beings

v) True vessels are absent in their xylem.
vi) Leaves are small and needle shaped.
vii) They are found in extreme climate (extreme cold or dry). They are also

known as xerophytes. Examples: Pinus, Cycas, Cedrus, Ephedra, Taxus,
Ginkgo.

Texus Cycas Fir Cedrus

MEMORY TIPS

Xerophytes are the plants that grow in extreme climatic condition which is either
too cold or too hot. They have developed certain adaptational characters in their
body to survive in such condition.

QUESTIONS >>
# Why are gymnosperms called conifers?
# Why doesn’t pinus bear true fruit?

c) Sub- division: Angiosperm (Gr- Angeion = case, sperm = seed)
They are highly developed flowering plants, which are characterized by the
following features:
i) They are the vascular plants, in which the seeds are protected (covered)
inside the ovaries.
ii) They bear true fruits or pods and flowers.
iii) True vessels are present in their xylem.
iv) They are mostly bisexual and some are unisexual too.
v) They are found in water, moist places and dry land.

On the basis of the number of cotyledons in their seeds, angiosperms are divided
into two classes. They are monocotyledons and dicotyledons.

Class: Monocotyledon

Characteristics:
i) They bear a single cotyledon in their seeds.
ii) They have fibrous/adventitious root system.

New Creative Science, Class 9 | 235

iii) They have long and narrow leaves with a parallel venation.
iv) Their vascular bundles are scattered in the stem.
v) They have trimerous flowers.
Examples: maize, oat, rice, barley, sugarcane, bamboo, etc.

Maize Rice Sugarcane Bamboo

Class: Dicotyledon

Characteristics:
i) They have two cotyledons in their seeds.
ii) They bear the tap root system.
iii) They have broad and short leaves with a reticulate venation.
iv) Vascular bundles are arranged in a ring system.
v) They have tetramerous or pentamerous flowers.
Examples: gram, pea, bean, mustard, sunflower, etc.

Bean Pea Sunflower Gram

QUESTIONS >>
# Why do angiosperms bear fruit whereas gymnosperms do not?
# Why do we think dicots are the most advanced flowering plants?

MEMORY TIPS

The flower in which the number of parts in each whorl is three or its multiple is
called trimerous, e.g; in most monocots. The flower in which each whorl is four
or five or their multiple is called tetramerous or pentamerous, respectively, e.g. in
dicots.
More than two cotyledons are found in plants like oranges, lemons, etc.

236 | Classification of Living Beings

ACTIVITY

(1) Soak some seeds of green gram, wheat, maize and pea. As they become tender, try to split
the seeds. Do all the seeds break into two nearly equal halves?

(2) Identify them as monocot or dicot.

(3) Now, look at their roots, leaves and flowers. Try to point out the differences among them.

Differences between monocots and dicots

S.N. Monocots S.N. Dicots

1. They bear only one cotyledon in 1. They bear two cotyledons in their

their seeds. seeds.

2. They have a fibrous root system. 2. They have a tap root system.

3. Leaves are long and narrow with a 3. Leaves are short and broad with

parallel venation. reticulate venation.

4. They have trimerous flowers. 4. They bear tetramerous or
pentamerous flowers.

5. Vascular bundles are scattered. 5. Vascular bundles are arranged in a
ring.

6. Secondary growth does not occur. 6. Secondary growth occurs.
Example: sugarcane, bamboo, Example: soyabean, mustard, apple,
maize, wheat, etc. mango, etc.

Differences between Gymnosperm and Angiosperm

S.N. Gymnosperm S.N. Angiosperm

1. They bear naked seeds and do not 1. Seeds are enclosed inside a seed

bear fruits. coat and bear fruits or pods.

2. They bear cones. 2. They bear flowers.

3. They are mostly unisexual. 3. They are mostly bisexual.

4. Xylem does not consist of true 4. Xylem consists of true vessel.

vessel. Example: maize, pea, bean, etc.

Example: pine, cedrus, cycas, etc.

Classification of Animals

All kinds of multicellular animals are kept under the kingdom Animalia. These
animals have different shapes, sizes and structure. Among them some animals have
a notochord and a backbone in their body, they are called vertebrates. For example,
human beings, cows, frogs, rabbits, etc. Similarly, some animals do not have a no-
tochord and a backbone in their body. They are called invertebrates. For examples,
sponge, hydra, insects, etc.

New Creative Science, Class 9 | 237

Classification of Invertebrates

The animals which do not have a notochord and a backbone in their body are
called invertebrates. They are simple and primitive animals. The invertebrates are
again divided into eight phyla.

(1) Phylum Porifera (Gr- Porus-pore, ferre-to bear)

The phylum Porifera includes plant-like animals. Thus, they are commonly
called sponges. The main characteristics of these animals are given below.

i) They are mostly marine but demospongiae is a fresh water-living creature.
ii) They are the first multicellular animals.
iii) Some of them are vase- like and some are flat, globular or irregular shaped.
iv) They are attached to the substratum and cannot move throughout their life.

So, they are also called sessile.
v) They have two layers of skin. So, they are also known as diploblastic ani-

mals.
vi) Their body bears a number of small pores (ostia) with a single large opening

called the osculum on the top.
vii) The current of water along with food enters through ostia and comes out

from the body through osculum.
viii) They possess an internal skeleton consisting of tiny calcareous or siliceous

spicules or the fine sponging fibres. These structures make the body rigid.
Example: sycon, spongilla, euspongia, euplectella, etc.

Spongilla Euplectella Sycon Euspongia

QUESTIONS >>
# Why are poriferons called sessile?
# Why is the body of poriferons rigid?

(2) Phylum- coelenterata (Gr- koils-hollow, enteron- gut)

They are also known as cnidarians as they have cnidoblasts in their body. The
main characteristics of coelenterate are given below.

i) Their body encloses a single cavity called the gastro-vascular cavity or
coelenteron.

238 | Classification of Living Beings

ii) They have a mouth but no anus.

iii) The mouth often bears slender, flexible processes called the tentacles which
help them to capture food.

iv) Their body wall is supplied with special stinging cells called cnidoblasts or
nematocyst for offence and defense purpose.

v) They are mostly aquatic.
Examples: hydra, sea-anemone, corals, obelia, jellyfish, etc.

Hydra Sea anemone Jellyfish Coral

QUESTIONS >>
# What are the functions of tentacles?
# What is the function of cnidoblasts?

(3) Phylum-Platyhelminthes (Gr. Platys-flat; helmins-worm)

It includes the bilaterally symmetrical flat worms. The main characteristics of
these animals are given below.

i) The animal body is soft and has a leaf-like or ribbon-like structure.

ii) Most of them are parasite and few are free living. The parasitic animals are
attached to their hosts by hooks and suckers.

iii) They are the triploblastic animals (that means they have three layers of
skin).

iv) Their body does not have a cavity or coelom.

v) The digestive system is incomplete.

vi) The excretory system includes flame cells (protonephridia).

vii) They are mostly hermaphrodite (bisexual) i.e. both male and female sex
organs are present in the same animal.

Examples: planarian, liver fluke, tapeworm, blood fluke, etc.

Liver fluke Planarian Blood fluke Tapeworm

New Creative Science, Class 9 | 239

QUESTION >>
# What do you mean by hermaphrodite animals?

(4) Phylum Aschelminthes or Nematoda or Nemathelminthes

They are the cylindrical, unsegmented and triploblastic animals. The main
characteristics of these animals are given below.

i) Their body length varies from microscopic to several centimetres.
ii) The body wall is covered with a tough and resistant cuticle.
iii) They have a pseudocoelom (false coelom) in their body.
iv) They have a mouth and an anus with a complete digestive system.
v) Sexes are generally separate.
vi) They are mostly parasitic and some are also free living.

Examples: ascaris , pinworm, hookworm, filarial worm, etc.

Ascaris Hookworm Pinworm

(5) Phylum- Annelida (L-annulus = ring)

They are the cylindrical, segmented and triploblastic animals. The main
characteristics of these animals are given below.

i) The body is divided into segments or circular ring-like grooves called
annuli.

ii) Locomotion takes place with the help of parapodia or setae.
iii) Their body cavity is a true coelom.
iv) The alimentary canal is complete.
v) The excretory organs are metanephridia.
vi) They may be unisexual or hermaphrodite.

Example: earthworm, leech, nereis, etc.

Leech Earthworm Nereis
240 | Classification of Living Beings

(6) Phylum-Arthropoda (Gr- arthros- jointed, Podos-foot)

Phylum Arthropoda is the largest phylum of the animal kingdom. It includes about
900,000 species. They are found in all types of habitats like air, water and soil. Similarly,
they breed a number of times and in each breeding, they produce hundreds of offspring.
So, this phylum includes a large number of species. The main common characteristics of
these animals are given below.

i) The body is externally segmented.

ii) The body may be divided into two regions; cephalothorax (jointed head and
thorax) and abdomen, or three regions; head, thorax and abdomen.

iii) They bear jointed appendages (legs).

iv) Exoskeleton is made of a thick chitinous cuticle. This hard cuticle restricts
the growth. Thus, this cuticle gets changed periodically during their growth.
This process is called moulting or ecdysis.

v) Their body cavity contains blood. It is called haemocoel.

vi) Respiration takes place by gills, trachea, book-lungs, book-gills, etc.

Examples: prawn, lobster, spider, ant, butterfly, millipede, centipede,
cockroach, etc.

Butterfly Lobster Crab Centipede

Millipede

Prawn Cockroach Ant Spider

This phylum is further divided into four classes. They are:

a) Crustacea b) Insecta c) Arachnida d) Myriopoda

Class: Crustacea
i) They are mostly aquatic.

ii) The body is divided into two parts i.e. head and thorax. These are fused to
form cephalothorax.

New Creative Science, Class 9 | 241

iii) Respiration takes place by gills or through the general body surface.

iv) The head of a crustacea bears a pair of compound eyes and five pairs of
appendages.
Examples: prawn, lobster, crayfish, crab, etc.

Prawn Lobster Crab

Class: Insecta

i) They are mainly terrestrial.

ii) The body is divided into head,

thorax and abdomen.

iii) The head of an insecta bears a pair

of compound eyes and a pair of

antenna. Butterfly Cockroach
iv) Breathing takes place with the

help of trachea.

v) They bear three pairs of legs and one or two pairs of wings.

Examples: butterfly, ant, silverfish, cockroach, etc.

Class: Arachnida
i) The body is divided into

cephalothorax and abdomen.
ii) They have four pairs of legs.
iii) They do not have compound eyes.

Example: spider, scorpion, mite, etc.

Class: Myriopoda Spider Scorpion
i) The body is elongated and divided

into head and trunk.
ii) They are mostly terrestrial.
iii) They have many pairs of jointed legs.
iv) They have simple eyes.

Example: centipede, millipede, etc.

Centipede Millipede

(7) Phylum Mollusca (L-Mollis = soft)

They are the animals having a soft body.
i) They have a soft and unsegmented body without external appendages.

242 | Classification of Living Beings

ii) The body is usually differentiated into three regions; anterior head, visceral
mass and foot.

iii) Mantle covers the body.
iv) In most cases, a calcareous shell is secreted from the mantle which covers

the body.
v) They are unisexual.

Examples: chiton, pila, limax or slug, snail, octopus, unio, squid, cuttlefish,
etc.

Slug Squid Snail

Octopus cuttlefish Pila

(8) Phylum Echinodermata (Gr- echinos- spiny, derma-skin)

The animals having spiny skin are kept under the phylum Echinodermata. They
are completely marine and lie at the bottom.

i) The shape of these animals may be star-like, cylindrical, melon-like or disc-
like or flower- like.

ii) The body surface is covered by the calcareous spines.
iii) They do not bear a head.
iv) Peculiar tube feet (podia) are developed for the locomotion.
v) They have water-vascular systems in their body.
vi) Their sexes are separate.

Examples: starfish, brittle star, basket star, sea-urchin, sand dollar, sea-
cucumber, feather star, etc.

Starfish Brittle star Sea urchin Sea cucumber

New Creative Science, Class 9 | 243

Classification of vertebrates

Vertebrates

Those animals which have a notochord and a backbone in their body are called
vertebrates. Some examples of vertebrates are human beings, cows, frogs, rabbits, etc.
All the vertebrates are kept under the phylum chordate.

Phylum: Chordata (Gr: chorda – string)
The common features of the phylum chordate are given below:
i) They have a notochord at the embryonic stage. It persists throughout the life
in lower organisms whereas it is replaced by a backbone in higher animals.
ii) A dorsal hollow nerve cord develops in their embryonic stage.
iii) They have gill clefts (slits).
iv) Their heart is ventral.
v) They have a post anal tail.

The phylum Chordata is again divided into five classes:

(i) Pisces (ii) Amphibians (iii) Reptiles (iv) Aves (v) Mammals

i) Class: Pisces (Fishes)
They are commonly known as fish and characterized by the following features:
i) They are completely aquatic, either marine or fresh water.
ii) They have a streamlined body and their skin is covered with scales.
iii) Respiration takes place through gills.
iv) They are oviparous (egg laying) and have external fertilization.
v) They have paired and unpaired fins for locomotion.
vi) They have a two-chambered heart,
Examples: Rohu, mandarin fish, flying fish, dog fish, electric ray, sting ray,
sea–horse, etc.

Mandarin fish Angler fish Labeo rohita (rahu) Flying fish

Electric ray Sting ray Dog fish Seahorse

244 | Classification of Living Beings

MEMORY TIPS

 The skeleton of marine fishes is made up of entirely cartilage whereas fresh
water fishes have a bony skeleton.

 Classes pisces, amphibians, reptiles are poikilothermic or cold-blooded
animals and classes aves and mammals are homoeothermic or warm-blooded
animals.

ii. Class: Amphibia (Gr. Amphi–double, bios-life)

They are the vertebrates which live both on land and in water. They are the first
land vertebrates. They inhabit in damp places and breed in fresh water. They have the
following features.

i) They have moist skin without scales.
ii) Respiration takes place through gills, lungs, skin, etc.
iii) The heart is three-chambered with two auricles and one ventricle.
iv) They are oviparous and have external fertilization.
v) They have two pairs of limbs without claws for locomotion,

Examples: frog (Rana), toad (Bufo), tree frog (Hyla), salamander (Salamandra)

Rana tigrina Salamander Toad Hyla (tree frog)
(common frog)

iii. Class: Reptilia (Latin: repre = to crawl)

They are the first true land vertebrates, which crawl on the ground. They have
the following major characteristics:

i) They are mostly terrestrial animals and live in warmer regions. Some are
aquatic and they also return to land for breeding.

ii) Their body is covered with horny scales.
iii) They have two pairs of pentadactyl limbs.
iv) They have teeth in their mouth except for a tortoise and a turtle.
v) Respiration takes place through lungs only (therefore aquatic animals come

on the surface for breathing).
vi) They have a three-chambered heart but the crocodile has a four-chambered

heart.
vii) They are oviparous and have internal fertilization.

Examples: wall lizard (Hemidactylus), chameleon, cobra (Naja) tortoise,
turtle (Chelone), crocodile, snake, etc.

New Creative Science, Class 9 | 245

Chameleon

King cobra Turtle

wall lizard (hemtdactylus) Flying lizard (Draco) Salamander

iv. Class: Aves (birds)

They are found both on land and in water. Most of them spend their time in air
as well. They have the following features:

i) Their body is streamlined or aerodynamic and covered with feathers.
ii) They have a pair of wings which help them to fly.
iii) The endoskeleton is bony but delicate and light.
iv) The mouth is surrounded by a horny beak adopted for various purposes.

They do not have teeth.
v) Respiration takes place through lungs.
vi) The hind limbs support the body in which scales are present, which shows

that birds are developed from the reptiles.
Examples: parrot, sparrow, crow, pigeon, duck, etc.

Parrot Sparrow Pigeon

Crow Eagle Duck
246 | Classification of Living Beings