Modern Concept Science and Technology 7

Modern Concept Science and Environment - 7 143

Differences between elements and compounds

S.N. Elements S.N. Compounds

1 Element is a pure substance that 1 Compound is a pure substance

cannot be broken down into other that can be broken down into its

simpler substances. constituent elements.

2 An element contains only one 2 A compound contains one, two

type of atoms. or more types of atoms.

3 Atoms are the smallest unit of an 3 Molecules are the smallest unit of

element. a compound.

4 Only 118 elements are discovered. 4 Thousands of compounds have

been discovered.

Molecular Formula

A molecule is formed by the combination of

two or more atoms of the same or different

elements. The symbolic representation of HCl H2O NH3

a molecule is called molecular formula.

For example, the molecular formula of

water is H2O, hydrochloric acid is HCl,
ammonia is NH3, etc. H2O represents one
molecule of water while 2H2O represents
two molecules of water. In one molecule of HCl, there is a chemical combination of

one atom of hydrogen and one atom of chlorine each. Similarly, in one molecule of

water, there are two atoms of hydrogen and one atom of oxygen that are chemically

combined. In a molecule of ammonia, one atom of nitrogen is chemically combined

with three atoms of hydrogen.

The molecular formulae of some compounds is provided in the table below:

Name Molecular Formula Name of the Molecular Formula
compounds

Hydrogen H2 Carbon dioxide CO2

Oxygen O2 Hydrogen chloride HCl

Nitrogen N2 Copper sulphate CuSO4

Chlorine Cl2 Ammonia NH3

Bromine Br2 Sodium hydroxide NaOH

While writing the molecular formula, we normally write the symbol of elements first
and then its number in subscript. For example: two atoms of hydrogen and one atom
of oxygen make one molecule of water. So, the molecular formula of water is H2O.

144 Matter

FACT WITH REASON

2H and H2 are chemically different, why?
2H represents two atoms of hydrogen. Such atoms of hydrogen are very reactive and immediately
combine with each other to form a molecule of hydrogen (i.e., H2 ). That is why atomic hydrogen
(H) is unstable. But, H2 represents a molecule which exists freely in air. That is why molecular
hydrogen (H2) is stable. So, 2H and H2 are chemically different.

11.2 Change in Matter

Heat, pressure and other actions can change the properties of matter. When heat
is supplied to water, it boils and changes into water vapour. Similarly, when you
burn magnesium ribbon in air, it burns with bright white flame and forms ashes of
magnesium oxide. On the basis of effect of change in physical and chemical properties,
there are two types of changes. They are: physical change and chemical change.

Physical Change MEMORY PLUS

Heat an ice cube in a beaker. Ice melts on heating Physical change involves change in
and changes into water. Again, freeze the water in a physical properties of matter like
refrigerator. It changes back into ice. Here, the state physical state.

of ice changes temporarily from solid to liquid and back to solid. Other properties of

ice are not changed. Such type of changes are called a physical changes. The temporary

and reversible change in which no new substance is formed is called physical change.

Examples of physical changes are boiling of milk, melting of wax, melting of metals,

heating of water, cooling water, etc.

ACTIVITY 2

Take a mutton/ pork/ chicken fat from a cold storage. Keep it in a porcelain basin and heat
it with the help of a burner. What do you observe after few minutes? Turn the burner off and
leave for about 15 minutes. What do you see? Discuss in your class about the changes that
you observe in this activity.

Characteristics of a physical change
i) It is a temporary change.
ii) It is reversible in nature.
iii) No new substances are formed.
iv) Properties of matter like taste, odour, etc. are not changed.

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FACT WITH REASON

Melting of iron is a physical change. why?
When iron melts its state changes from solid to liquid but its composition remains the same
without formation of new substances. So, melting of iron is a physical change.

Chemical Change MEMORY PLUS

Take a paper and burn it. After burning, the solid Chemical change involves change in
paper turns into smoke and ashes. Smoke and ashes physical and chemical properties of
have different physical and chemical properties than matter.

that of paper. Can you combine ashes and smoke to make paper again? It is not

possible because this change is a permanent change and cannot be reversed back.

Such type of change is called a chemical change. The permanent irreversible change

in which new substance is formed is called a chemical change. Examples of chemical

change are burning of woods, rusting of iron, burning of fuels, forming of butter and

yoghurt from milk, etc.

ACTIVITY 3

Take a small piece of magnesium ribbon. Hold the ribbon with the help of tongs. Burn it
with the help of a burner. What do you observe? Discuss in your class about the change
that you observe in this activity.

Characteristics of Chemical Change

i) It is a permanent change.
ii) It is generally irreversible in nature.
iii) New substances are formed.
iv) Both physical properties and chemical properties are changed.

FACT WITH REASON

Rusting of iron is a chemical change. Why?
Rusting of iron is a chemical change because it is a permanent reversible change in which new
substance, i.e. rust is formed.

Differences between physical change and chemical change.

S.N. Physical change S.N. Chemical change

1 Physical change is a temporary 1 Chemical change is a permanent
change and therefore is reversible. change and therefore is irreversible.

146 Matter

2 In this change, only physical 2 In this change, both chemical and

properties change. physical properties change.

3 No new substances are formed. 3 New substances are formed.

STEPS EXERCISE

STEP 1

1. Fill in the blanks with appropriate words.
a) ……………… is the amount of matter contained in a body.
b) ……………… is the space occupied by a body.
c) …………, ……… and ……… are the three most common states of matter.
d) ……………… flow from higher level to a lower level because they have
less intermolecular force of attraction.
e) The symbol of ……………… is ‘K’.
f) The molecular formula of ammonia is …………

2. Write True for the correct and False for the incorrect statements.
a) Matter has mass and occupies space.
b) Carbon dioxide is an element.
c) H2 is the symbol of Hydrogen atom.
d) Physical change is irreversible.
e) O is an atom of hydrogen and O2 is a molecule.

STEP 2

3. Answer the following questions in one word.
a) What is the term used for objects having mass and volume?
b) What kind of change is burning of paper?
c) Which one is chemically active: an atom or a molecule?
d) How many naturally occurring elements are there?
e) Write the symbol of potassium.

4. Differentiate between:
a) Atoms and molecules
b) Melting of iron and rusting of iron
c) Physical change and chemical change
d) H and H2

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5. Give reasons.
a) Sodium is an element.
b) Burning of paper is called a chemical change.
c) Melting of iron is a physical change.
d) Sodium chloride is a compound.

STEP 3

6. Answer the following questions
a) What are solids? List any three important properties of solids.
b) Define liquids and mention their three properties.
c) What are gases? Write any three properties of gases.
d) List any two important properties of each physical change and chemical
change.
e) Write the symbol of the following elements.
i) Magnesium ii) Silicon iii) Potassium
f) Write the molecular formula of the following molecules:
i) Copper sulphate ii) Carbon dioxide iii) Ammonia
g) Identify the physical change and chemical change.
i) Burning of paper ii) Heating ice
iii) Boiling an egg iv) Boiling of water
v) Melting of ice vi) Burning of wood
vii) Formation of curd viii) Formation of ice
h) Define element and compound with two examples of each.
i) What is an atom? Why is it neutral in nature?

7. Draw the structure of the following:
a) Molecule of water
b) Molecule of hydrogen
c) Sodium atom

1U48NITMixtureEstimated teaching periods Theory Practical
11 1

12 Mixture

Syllabus issued by CDC Centrifuge machine

 Methods of separating components of mixture (Evaporation, Sublimation,
Centrifuging, Crystallization)

 Uses of mixture
 Solution, dilute solution and concentrated solution
 Unsaturated, saturated and supersaturated solution
 Utilities of solution in our daily life

LEARNING OBJECTIVES

At the end of this unit, students will be able to:
 explain and demonstrate some methods of separating the components of mixture

(evaporation, sublimation, centrifuging and crystallization).
 describe the utilities of mixture.
 define solution and differentiate between dilute and concentrated solution.
 introduce unsaturated, saturated and supersaturated solution and demonstrate them.
 explain the utilities of solution in our daily life.

Key terms and terminologies of the unit

1. Mixture: Mixture is a mass that is formed by mixing two or more
different substances in any proportion by their weight.

2. Homogeneous mixture: The mixture in which mixing components are distributed
uniformly and they cannot be identified by naked eyes is
called a homogeneous mixture.

3. Heterogeneous mixture: The mixture in which mixing components are not distributed
uniformly and can be identified with our naked eyes is called
a heterogeneous mixture.

4. Separation of mixture: The process of separating the individual components of a
mixture by using various methods is called separation of
mixture.

5. Evaporation: Evaporation is the process of changing liquid into vapour
(gas) by heating.

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6. Sublimation: Sublimation is the process in which solids are converted
directly into vapour on heating and gases to solids directly
on cooling without forming liquids.

7. Centrifugation: Centrifugation is a method of separating heavy or
suspended particles from their mixture by rotating the
mixture at a high speed.

8. Crystallization: The process of preparing crystals by cooling hot and
concentrated solution is called crystallization.

9. Crystals: Crystals are the pure substances which have definite
geometrical shape, smooth surface and sharp edges.

10. Centrifuge: A centrifuge is a device that contains a rotator and holders
which rotates at high speed to separate the components of
a mixture.

11. Solution: The homogeneous mixture of two or more substances is
called a solution.

12. Solute: Solute is the substance that gets dissolved into another
substance.

13. Solvent: Solvent is the substance that dissolves the solute.

14. Dilute solution: The solution that contains relatively less amount of solute
in a given amount of solvent is called dilute solution.

15. Concentrated solution: The solution that contains relatively higher amount of solute
in a given amount of solvent is called concentrated solution.

16. Unsaturated solution: The solution that can dissolve more solute at a given
temperature is called an unsaturated solution.

17. Saturated solution: The solution that cannot dissolve more solute at given
temperature is called a saturated solution.

18. Supersaturated solution: The saturated solution at higher temperature that gives solute
back in the form of crystals is called a supersaturated solution.

12.1 Introduction

Mixture is the substance that is formed by the combination of two or more different
substances at any proportion by their weight. Examples of mixture are: sugar and
water, salt and water, paper, cloth, food, cold drinks, etc. Mixtures can be made from
both pure and impure substances. But, a mixture itself is an impure substance as it
contains mixing components in any proportion by their weight.

150 Mixture

In most of the cases, the components of a mixture retain their original properties. So,
they can be separated by using available techniques.

FACT WITH REASON

Why is mixture an impure substance?
Mixture is formed by the combination of two or more substances at any ration by their weight. There
does not form a new substance after mixing two or more substances. So, it is an impure substance.

There are two types of mixtures. They are homogeneous mixture and heterogeneous
mixture. The mixtures in which mixing components are distributed uniformly and
they cannot be identified with our naked eyes are called homogeneous mixtures.
Examples are : mixture of lemon juice, salt in water, mixture of sugar in water, etc.

The mixture in which components are not distributed uniformly and can be identified
by our naked eyes is called heterogeneous mixture. Examples are: mixture of sand
and water, mixture of water and metals filings, mixture of pebbles and water, etc.

In mixtures, one state of matter can also mix with MEMORY PLUS
another state of matter. Some of the common types
of mixtures that include the mixing of different states In a mixture, the mixing components
of matter are: do not lose their identity.

Mixture types Mixtures
Solid-liquid Common salt solution, sugar solution, etc.
Liquid-liquid Water and alcohol, water and ink

Solid-gas Smoke
Gas-gas Air
Solid-solid Alloys
Liquid-gas Aerated soft drinks

Reason for Separating the Components of a Mixture

We separate the components of a mixture in our daily MEMORY PLUS
life for various purposes. We separate tea leaves
from tea. We filter water to separate tiny sediments Colloid is also a type of mixture.
It is a transitional type of mixture

from it. We remove husk from rice or wheat or between homogeneous mixture and
flour by using handpicking, winnowing or sieving. heterogeneous mixture. Examples of
We separate butter from curd using our domestic colloids are: butter, ice cream, paint,
techniques of centrifugation. In some mixtures, the milk, etc.

mixing components are the impurities that we do not need. While in other cases,

the mixing components are useful but we need one of the mixing components in

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relatively pure form. Therefore, the three major reasons for separation of components
of the mixture are:
1. To remove the unnecessary components or the impurities.
2. To separate harmful substances and get useful substance.
3. To get pure or relatively pure substances.

12.2 Methods of Separation of Components of Mixture

The process of separating the individual components of the mixture by using various
methods is called separation of mixture. Depending upon the nature of mixing
components, both physical and chemical methods are used to separate the components
of mixture. The main principle of separation of mixture is that different components
of a mixture have different properties. Based on the properties of the components of
mixture, the methods of separation should be selected.

Some of the physical methods of separation of mixtures are evaporation,

sedimentation and decantation, filtration, crystallization, distillation, centrifugation,

chromatography, etc. In this unit we will discuss about evaporation, sublimation,

centrifugation and crystallization in brief.

Evaporation Steam

Evaporating dish

Evaporation is the process of changing liquid

into vapour (gas) by heating. It is one of the easy Water
processes to separate solid-liquid homogeneous

mixtures. This method is applied when liquids have

lower vaporizing temperature than that of solid. Stand

Mixtures of salt and water, water and sugar, water

and alum, etc. can be separated by this method.

When we evaporate the liquid of such mixtures, gas

escapes out and the solid remains as a residue.

Evaporation is used for removing salt from sea Evaporation of water

water. For this purpose, salt water is brought to shallow ponds and left to vaporize.

The heat of the sun gradually evaporates water from the mixture and salt is left behind.

The common salt we eat every day comes for similar process.

FACT WITH REASON

Evaporation is used to separate salt from water, why?
Water has lower vaporizing temperature than that of common salt. Which makes it possible to
remove water in the form of vapour leaving salt behind. So, evaporation is used to separate salt
from water.

152 Mixture

ACTIVITY 1

OBJECTIVE : To separate salt from salt solution (mixture). Steam

MATERIAL REQUIRED Evaporating
Porcelain basin/ Evaporating dish, tripod stand, Burner, Wire dish
gauze, salt, water, glass rod
Salt and water

PROCEDURE Stand
1. Take some distilled water in a porcelain basin.

2. Add some salt in it and stir with the help of glass rod.

3. Place the basin above the wire gauze on the burner as

shown in the figure.

4. Heat the solution till a little amount of water remains in the basin.

5. Turn off the burner and observe after few minutes.

OBSERVATION

The remaining little water also evaporates from the porcelain basin and salt remains there.

CONCLUSION

Water is evaporated and salt is left behind as a residue. In this way, we can separate water

and salt solution by evaporation.

ACTIVITY 2

Under the strict guidance and supervision of your teacher, separate copper sulphate from the
solution of copper sulphate and water.

Sublimation

When ice is heated, it changes into water. When water is further heated, it changes into
vapour. It means, on heating solids, they first change into liquids and then into gases.

There are some solids that directly change into gases (vapour) on heating. This
process is called sublimation. Thus, sublimation is a process in which solids are
converted directly into gases (vapour) on heating and gases to solids directly on
cooling without forming liquids. Those substances that show process of sublimation
are called sublimates. Examples of substances are camphor, naphthalene, ammonium
chloride, etc. Sublimation is applied usually in solid-solid mixtures where one of the
components of the mixture is a sublimate. Examples of such mixtures are sand and
camphor, sand and naphthalene, salt and ammonium chloride, etc.

FACT WITH REASON

Sublimation is used to separate a mixture of camphor and salt, why?
Camphor is a substance which directly changes into vapours on heating and vapour changes into
solid on cooling. So, sublimation is used to separate camphor from sand.

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ACTIVITY 3

OBJECTIVE : To separate the mixture of salt and camphor.
MATERIAL REQUIRED
Porcelain basin or china dish, tripod stand, burner, wire
gauze, salt and camphor mixture, wet cotton, funnel,
match stick
PROCEDURE

1. Take a mixture of salt and camphor in a
porcelain basin.

2. Invert a funnel over the mixture on the basin.
3. Loosely plug the end of the tube of funnel with wet cotton.
4. Place the basin above the wire gauze on a tripod stand.
5. Turn on the burner to heat the apparatus as shown in the given figure.
OBSERVATION
The camphor converts into white smoky vapour on heating. It rises up into the inverted funnel
and then collected in the wet plug. The wet plug cools the vapour of the camphor and camphor
gets solidified. Salt is left behind in the porcelain basin.
CONCLUSION
Camphor gets collected at the inner wall of funnel and salt is left behind. In this way, we can
separate salt and camphor from their mixture by sublimation.

Centrifugation

Centrifugation is the method of separating heavy or suspended particles from their
mixture by rotating the mixture at a high speed. This method can be applied only to
those mixtures in which one of the components of the mixture is relatively heavier.
Examples of such mixtures are: milk, chalk powder in water, muddy water, blood, etc.
This process is used in dairy industries to separate cream from milk. In medical
laboratories, blood cells and plasma are separated by this method.

A centrifuge is a device that contains a rotator and MEMORY PLUS
holders, which rotates at a high speed to separate
the components of a mixture. Holder holds the test Plasma, which is one of the important
tubes or vessels in which the mixture is kept. When constituent of human blood, is
centrifuge is turned on, the rotator rotates at a high separated from the blood by using
speed. The force of rotation acts very high in heavier centrifugation.

particles. Due to the combined effect of rotational force and gravity, heavier particles

settle down at the bottom of the test tube and lighter particles settle over them. The

lighter particles are usually separated by decantation.

FACT WITH REASON

Why is milk centrifuged?
Milk is centrifuged to separate fat from it which has different density than that of milk.

154 Mixture

ACTIVITY 4

OBJECTIVE : To separate the mixture of chalk powder and water.
MATERIAL REQUIRED
Centrifuge, test tubes, beaker, chalk powder and water
PROCEDURE

1. Prepare a mixture of chalk powder and water in a beaker.
2. Transfer the mixture into some test tubes.
3. Place the test tubes in the test tube holder in the centrifuge.
4. Switch on the centrifuge.
5. Turn it off after a couple of minutes.
OBSERVATION
The chalk powder settles down at the bottom of the test tube when rotated at a very high
speed in the centrifuge. Water remains above the chalk powder.
CONCLUSION
Upon centrifugation, the heavier substance like the chalk powder settles at the bottom and
lighter substance like the water remains at the top. In this way, we can separate chalk powder
and water from their mixture by centrifugation.

Crystallization

The process of preparing crystals by cooling a hot and concentrated solution at room
temperature is called crystallization. This process is used to separate the components
of mixture if the soluble component of the mixture can occur as crystal. Crystal is the
pure substance which have definite geometrical shapes, smooth surface and sharp
edges. Mixtures like salt solution, copper sulphate solution, sugar solution, etc. can be
separated by using crystallization processes.

Crystals can be formed by evaporating the solvent in a saturated solution. When

about half of the solvent is evaporated, the solution is cooled down. On cooling down,

the crystals are then obtained from the mother MEMORY PLUS
liquor. The residual solution that remains after
crystallization is called mother liquor. 1. Some crystals like emeralds are
formed when magma cools very
Slow cooling of a hot saturated solution gives large slowly.

crystals. Intrusive igneous rocks are formed by 2. Have you seen a thread in the
slow cooling of magma. They have relatively large crystal of sugar candy or ‘mishri’?
crystals that are easy to see. In order to grow large Presence of thread in the crystal
crystals, a seed crystal is tied on a piece of thread means the small crystal of ‘mishri’
and is submerged in the supersaturated solution. A was suspended on a thread in the
seed crystal is a small single crystal that we put in a supersaturated solution to grow
large crystals.

supersaturated solution to grow a large crystal.

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ACTIVITY 5

OBJECTIVE : To prepare the crystals of copper sulphate from copper sulphate solution
MATERIAL REQUIRED
Tripod stand, wire gauze, glass rod, copper
sulphate, distilled water, two beakers, burner
PROCEDURE

1. Take some distilled water in a beaker.
Add copper sulphate in the water and
stir with a glass rod.

2. Keep on adding copper sulphate till no
more of it dissolves in the water. As a result, saturated solution of copper sulphate is
prepared.

3. Heat the saturated solution further on adding more copper sulphate to make a
supersaturated solution.

4. Pour the solution into another beaker. Use a glass rod to suspend a thread into the
solution.

5. Leave the beaker undisturbed for a few days.
OBSERVATION
Light blue copper sulphate crystals are seen attached to the suspended thread.
CONCLUSION
In this way, we can prepare the crystals of copper sulphate from its solution.

ACTIVITY 6

Boil water and add potash alum continuously until it dissolves. Cool the solution in a small
basin. Suspend a thread into the solution. Do not disturb the solution for some days. Write
what you observe. Show your findings to the teacher.

Uses of Mixture

i) Plants absorb the mixture of water and minerals and use them for photosynthesis.

ii) Mixtures of various chemical substances are used for making medicines,
cosmetics, dyes, fabrics, etc.

iii) Mixture of carbon dioxide, sugar and water along with other additives are used
for manufacturing cold drinks.

iv) We make our food in the form of mixture.

v) Mixtures of cement, water, sand and gravel are used for construction purpose.

156 Mixture

12.3 Solution

The homogeneous mixture of two or more substances is called a solution. Examples
of solutions are: sugar solution, salt solution, solution of copper sulphate, soft drinks,
alcohol, etc. In fact, a solution is a homogeneous mixture of solute and solvent.

Solution = Solute + Solvent

Solute is a substance that gets dissolved into another MEMORY PLUS
substance. Normally, solutes are solids. The amount
of solutes is less than that of solvent. Solvent is the Water is called a universal solvent
substance that dissolves the solute. For example, because it can dissolve most of the
in a sugar solution, sugar is a solute and water is a organic substances in it.

solvent. Similarly, in copper sulphate solution, copper sulphate is a solute and water is

a solvent. In coca cola, carbon dioxide gas and sugar are solutes and water is a solvent.

Differences between solute and solvent.

S.N. Solute S.N. Solvent

1 Solute is a substance that gets 1 Solvent is a substance that

dissolved into another substance. dissolves the solute.

2 Relatively solute is less in amount 2 Relatively solvent is more in

than the solvent. Example: sugar in amount than the solute. Example:

sugar solution. Water is a solvent in sugar solution.

Dilute solution and Concentrated Solution

If two or more beakers contain same amount of solvent
in them, solutes determine the strength of the solution.
In chemical language, strength of the solution is known
as concentration of solution. On the basis of amount of
solutes, solution can be of two types. They are dilute
solution and concentrated solution. The solution which Dilute solution Concentrated solution
contains relatively less amount of solute in a given amount of solvent is called dilute
solution. Similarly, the solution which contains relatively higher amount of solute
in a given amount of solvent is called concentrated solution. The words dilute and
concentrated are relative terms. We cannot say that a solution is dilute or concentrated
unless we compare with another solution with the same amount of solvent. In colourful
solutions, concentrated solutions look darker than the dilute solutions.

Modern Concept Science and Environment - 7 157

In the given figure, there are two beakers which MEMORY PLUS
contain 500 ml water each. Beaker A contains 1
spoon of salt and Beaker B contains 2 spoon of salt The dilute and concentrate are relative
dissolved in water. Therefore, we can say that terms. One solution may be dilute
Beaker A has dilute (less concentrated) solution and with respect to one kind of solution
Beaker B has concentrated (more concentrated and may be concentrate with respect
solution) solution. another kind of solution.

Differences between dilute solution and concentrated solution

S.N. Dilute solution S.N. Concentrated solution

1 The solution which contains 1 The solution which contains

relatively less amount of solute in relatively higher amount of solute

a given amount of solvent is called in a given amount of solvent is

dilute solution. called concentrated solution.

2 Dilute solution has relatively less 2 Concentrated solution has

density. relatively more density.

ACTIVITY 7

Tell your friend to take 20 ml of tap water in two separate beakers each. Ask him to add one
spoonful of copper sulphate in one of the beakers and four spoonful of the same solute in
another beaker. Let him stir the solutions firmly. Do not observe his procedure. After stirring,
observe these two beakers and explain which solution is dilute and which is concentrated?
How do you find out the concentration just by observing? Can you tell the concentration in case
of lemon juice dissolved in water? Why/Why not?

ACTIVITY 8

Take two similar glasses with half-filled water in them. Take two lemons and cut them into 2
parts each to make 4 pieces of lemon. Squeeze a piece in one glass and remaining 3 pieces in
another glass. Taste water from both glasses. Which one tastes sourer? Which one of them is a
dilute solution and which one of them is a concentrated solution?

Unsaturated, Saturated and Supersaturated Solution

On the basis of dissolving ability of a solvent, there are three types of solutions. They are:

Unsaturated solution Saturated solution Supersaturated solution

158 Mixture

a) Unsaturated solution
The solution which can dissolve more solute at the given temperature is called
unsaturated solution. To make an unsaturated solution, take a certain volume of
water and add some solute into it spoon by spoon. The solute is easily dissolved
by the solvent. Hence, it is an unsaturated solution.

FACT WITH REASON

Unsaturated solution can dissolve solute easily. Why?

Unsaturated solution has enough intermolecular spaces among the solvent molecules. So, solute molecules
can fit easily. Hence, unsaturated solution can dissolve solute easily.

b) Saturated solution

On adding solute continuously in an unsaturated
solution, a time comes when solution cannot
dissolve any more solute at that temperature.
This is called saturated solution. Thus, the
solution which cannot dissolve any more solute
at that temperature is called saturated solution. In this case the solvent cannot
dissolve any more solute because all the gaps between the solvent molecules
(i.e., intermolecular space) are already filled.

FACT WITH REASON

Saturated solution cannot dissolve more solute. Why?

Saturated solution cannot dissolve more solute because the intermolecular spaces among the molecules
are already occupied by the solute molecules.

c) Supersaturated solution

When a saturated solution is heated, the solution can dissolve more amount of
solute in it. It is because on increasing the temperature, the molecules of solvent
move apart from each other and thus more gaps are created for the solutes
to dissolve. If we stop increasing the temperature, the added solutes do not
dissolve and crystallize out. This condition of a solution is called supersaturated
solution. The saturated solution at higher temperature that throughout solute
crystals on adding more solute is called a supersaturated solution.

Methods for Identification of Unsaturated, Saturated and Supersaturated
Solution

The three solutions shown in the given figure are of copper sulphate solutions. Add
some more copper sulphate in all of these beakers and stir. Does the added solute
dissolve completely? Keep on adding the solute and stir them firmly. The solution
that dissolves more copper sulphate is an unsaturated solution.

Modern Concept Science and Environment - 7 159

Unsaturated solution Saturated solution Supersaturated solution

But, if not even a small amount of solute is dissolved MEMORY PLUS
after stirring for a while, the solution is saturated. It
means there is already a lot of solute dissolved in it. A saturated solution becomes
unsaturated on heating and becomes
On cooling the solution at room temperate, if it supersaturated on cooling.
gives copper sulphate crystals at its bottom, then
the solution is called supersaturated. It means more
solute has been added to the saturated solution.

FACT WITH REASON

Supersaturated solution throughout the solute in the form of crystals. Why?

In supersaturated solution, the intermolecular spaces of the solvent molecules are already occupied by the

solute. So, if we add more solute, the solute molecules cannot get spaces to fit inside. So, they sediment in

the form of crystals.

Uses of solution

1. Roots of plants absorb water and mineral in the form of solution.

2. Most of the cold drinks are the solution containing water, sugar, gases or any
soluble additives.

3. Digestion and absorption of food occurs in the form of solution.

4. Solutions are used in food industries, metal industries, medical and
pharmaceutical industries, cosmetics and other industries.

5. Saline solution for patients is widely used to maintain ion concentration and
body fluids in patients.

STEPS EXERCISE

STEP 1

1. Fill in the blanks with appropriate words.
a) Mixing components are evenly distributed and cannot be seen by naked
eyes in ……………… mixture.
b) ……………… is applied when liquids have lower vaporizing temperature
than that of solid.

160 Mixture

c) Examples of ……………… are camphor, naphthalene, ammonium
chloride, etc.

d) A ………………is a device that contains a rotator and holders and that
rotates at a high speed to separate the components of a mixture.

e) ……………… are the pure substances having definite geometrical shape
and sharp edges.

2. Write True for the correct and False for the incorrect statements.
a) Mixture is an impure substance.
b) In sugar solution, water is a solute and sugar is a solvent.
c) Centrifuge separates cream from milk.
d) Crystals have definite geometrical shapes.
e) Unsaturated solution cannot dissolve more amount of solute at a given
temperature.

STEP 2

3. Answer the following questions in one word.
a) What kind of mixture is salt solution?
b) Which one is solute if few drops of water is mixed in a glass of alcohol?
c) What is the term used for solution which has relatively higher amount of
solute in it?
d) Which method is better to separate the mixture of water and copper
sulphate?
e) Which term is used for the homogeneous mixture of solute and solvent?

4. Differentiate between:
a) Solute and solvent
b) Evaporation and sublimation
c) Concentrated solution and dilute solution
d) Unsaturated solution and saturated solution
e) Unsaturated solution and supersaturated solution

5. Give reasons.
a) Evaporation is used to separate salt and water.
b) Milk is centrifuged.

Modern Concept Science and Environment - 7 161
c) Sublimation is used to separate camphor from salt from the mixture of

camphor and salt.
d) Water is called a universal solvent.
e) Centrifugation is not applicable to separate the mixture of sugar and water.
f) Saturated solution cannot dissolve more solute?
6. Identify the methods of separation of mixture shown below. Also write down
one example of mixture to separate by using these methods each.

a) b) c) d)

STEP 3

7. Answer the following questions
a) What is mixture? Write any four importance of mixture.
b) Define evaporation and sublimation.
c) How is salt produced from sea water?
d) What kind of mixtures is separated by centrifugation?
e) Define sublimate with two examples.
f) Explain sublimation process of camphor and sand with a diagram.
g) Explain in brief about the crystallization of copper sulphate with a diagram.
h) Explain the meaning of concentrated and dilute solutions with examples.
i) Define solution. What are saturated, unsaturated and supersaturated
solutions?
j) Define centrifugation. What is a centrifuge?

8. Name the best method for the separation of the following mixtures:
a) Water and salt
b) Camphor and sand
c) Blood cells and plasma

162 M etals EasntimdaNteodnte-amcehtinaglpseriods Theory Practical
UNIT 4 2

13 Metals and Non-metals

Syllabus issued by CDC Gold

 Metal and properties of metals
 Non-metal and properties of non-metals
 Alloys and their properties
 Some useful alloys (brass and bronze)
 Some useful non-metals (sulphur and iodine)

LEARNING OBJECTIVES

At the end of this unit, students will be able to:
 introduce metals and non-metals and differentiate between them.
 define alloys with examples.
 explain the properties and uses of some useful alloys (brass, bronze) and non-metals

(sulphur and iodine).

Key terms and terminologies of the unit

1. Metals: Metals are mostly hard and shiny substances that are good conductor
of heat and electricity. Examples: iron, silver, gold, copper, etc.

2. Non-metals: Non-metals are mostly soft substances that are bad conductor of heat
and electricity. Examples: carbon, hydrogen, sulphur, etc.

3. Metalloids: Elements that show properties of both metals and non-metals are called
metalloids. Examples: silicon, germanium, etc.

4. Alloy: An alloy is a homogeneous mixture of two or more metals or sometime
metals and non-metals. Examples: brass, bronze, steel, etc.

5. Malleability: The property of a metal to be beaten into a thin sheet is called
malleability.

6. Ductility: The property of a metal to be drawn into thin and long wires is called
ductility.

7. Conductors: The substances which which allow electric current to pass through
them are called conductors. Examples metals

8. Insulator: The substances which do not allow electric current to pass through
them are called insulators. Examples non-metals

Modern Concept Science and Environment - 7 163

13.1 Introduction

We use variety of substances in our daily life. They occur in different forms like
solids, liquids and gases. Some of them are hard and others are soft. Some of them
conduct heat and electricity and others do not. Some of them are opaque, some are
translucent and others are transparent. We can also differentiate them on the basis of
their appearance. Some of them are shiny while some are dull.

Elements are divided into three broad groups namely metals, metalloids and non-
metals. Sodium, magnesium, potassium, calcium, iron, nickel, copper, zinc, etc. are
metals. Similarly, silicon, germanium, arsenic, etc. are metalloids. Chlorine, bromine,
oxygen, neon, carbon, etc. are some of the examples of non-metals. In this unit, we
will discuss about the characteristics of metals, non-metals and metalloids.

Metals MEMORY PLUS

Metals are generally hard and shiny substances Metals that are liquids at room
which are good conductor of heat and electricity. temperature are mercury (Hg) and
Elements like gold, copper, sodium, magnesium, gallium (Ga). Bromine is a liquid non
calcium, tin, iron, etc. are examples of metals. metal at room temperature.

If you observe the utensils in your kitchen, most of them are shiny, hard and difficult to
break. They also produce a tinkling sound when you hit them gently with a hammer.
They have high melting point. So, we use them for cooking food. Metals are very
strong and do not break into pieces easily. So, they are also used for making buildings,
bridges, weapons, etc. Some metals are also used for making jewelleries, idols, coins,
etc. Metals like iron and aluminium are widely used for making engines, weapons etc.

Properties of metals

i. Most of the metals are hard and strong.

ii. They have high melting and boiling points.

iii. They are good conductor of heat and
electricity.

iv. Metals possess a metallic lustre (i.e., shine). Malleable Ductile

v. They are malleable (i.e. metals can be converted into thin sheets when beaten).

vi. They are ductile (i.e. metals can be drawn into wires).

vii. They are sonorous (i.e. metals produce tinkling sound on hitting.

FACT WITH REASON

Copper is used for making electrical wires. Why?
Copper is used for making electrical wires because it is malleable, ductile and good conductor of
electricity.

164 Metals and Non-metals

Non-metals

Non-metals are the generally soft substances which are bad conductor of heat and
electricity. Examples of non-metals are sulphur, iodine, chlorine, carbon, oxygen,
nitrogen, phosphorous, etc. Non-metals have different uses in our daily life. Hydrogen,
which is a non-metal, is used to prepare vegetable ghee. Carbon is used for making
electrodes in a cell. Nitrogen is used by plants to synthesize protein. Oxygen is the
most important non-metal (gas) that we need for respiration.

Properties of Non-metals

i. Non-metals are relatively soft in comparison to metals and they occur as solids,
liquids or gases.

ii. Non-metals are bad conductor of heat and electricity (except grahite which
conducts heat and electricity).

iii. Non-metals do not have metallic lustre and are dull.

iv. Non-metals are neither malleable nor ductile. Hard non-metals are brittle in
nature (i.e. breaks into pieces).

v. Non-metals usually have low melting and boiling points.

vi. Non-metals do not produce tinkling sound on hitting.

ACTIVITY 1

Take some connecting wires, a cell, a plug in switch and a bulb. Insert different pieces of
substances in the plug like a piece of iron, paper, plastic, wood and glass to make the circuit
closed. Does the bulb glow? What type of substances glow the bulb and what type do not glow
the bulb? Draw a conclusion.

ACTIVITY 2

Take a small amount of phosphorous and place it in a paper. Also take a metallic plate. Hit
both the phosphorous and metallic plate with the hammer. Which produces metallic tinkling
sound?

ACTIVITY 3

Burn a candle. Take a spoon and heat its one end. Does the heat transfer to your fingers? Again,
take a stick, wood, plastic, etc. to do the same. Do they conduct heat? Write down which
substances conduct heat and which do not.

Metalloids MEMORY PLUS

Those elements that show properties of both metals Silicon is the eighth most abundant
and non-metals are called metalloids. Examples element in the earth by weight. It is
of metalloids are silicon, germanium, arsenic, almost never found as a pure or free
antimony, etc. element in the naturally.

Modern Concept Science and Environment - 7 165

Metalloids are used widely to make semi-conductors. These semiconductors are
mainly used in electronic devices like radios, mobile phones, televisions, etc.

Differences between metals and non-metals.

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

1 Metals are usually present in solid 1 Non-metals occur in all three physical

state. states i.e. solid, liquid and gas.

2 They have high melting and boiling 2 They usually have low melting and

point. boiling point.

3 They possess metallic lustre. 3 They do not possess metallic lustre.

4 They are malleable and ductile. 4 They are usually brittle in nature.

5 They are good conductor of heat 5 They are bad conductor of heat and

and electricity. electricity.

Alloys MEMORY PLUS

An alloy is a homogeneous mixture of two or more Electrum is a  naturally occurring
metals  or metals and non-metals. An alloy may be alloy  of gold and silver with small
a solid solution. While making an alloy, the metals amounts of copper and other metals.
are melted and mixed in a certain ratio. Brass, bronze, It was also called as ‘white gold’ by the
stainless steel, etc. are the examples of alloys. Alloys ancient Greeks. It was used in the past
are used for making coins, medals, idols, household for making coins, drinking vessels and
utensils, etc. Some examples of alloys and their ornaments.
constituents are mentioned in the table below.

S.N. Alloys Constituents

1 Brass Zinc and copper

2 Bronze Tin and copper

3 Steel Iron and carbon

4 Stainless steel Iron, chromium, manganese and carbon

Properties of Alloys

1. Alloys have more strength than their individual components.

2. They are harder like metals.

3. They show metallic lusture.

4. They are good conductor of heat and electricity.

5. They can be brittle or malleable.
6. Rusting does not occur in alloys.

166 Metals and Non-metals

FACT WITH REASON

Generally cooking utensils are made up of alloys. Why?
Generally, cooking utensils are made up of alloys because alloys do not rust and they are good
conductor of heat.

Differences between metalloids and alloys

S.N. Metalloids S.N. Alloy

1 Elements that show properties of both 1 An  alloy  is a mixture of  two or more

metals and non-metals are called metalloids. metals or metals and non-metals.

2 Metalloids are semi-conductors. 2 Alloy is a good conductor of electricity.
Examples: silicon Example: bronze

Some Useful Alloys

a) Brass

Brass is a metallic alloy composed of about

85% copper and 15% zinc. It is yellow,

somewhat similar to gold in colour but is

duller than gold. It has higher malleability

than zinc or copper. It has low melting point Brass

of about 900°C. It is resistant to corrosion. Brass is used to make decorative items,

utensils, coins, statues, etc. Locks, gears, doorknobs, ammunitions, valves, etc.

are manufactured from brass. It is also used in plumbing, musical and electronic

instruments.

b) Bronze

Bronze is a metallic alloy composed of about

90% copper and 10% tin. It is reddish brown in

colour. It is hard but brittle. Its melting point is

about 9500C. It also resists corrosion. It is widely

used in boat and ship fittings, propellers and

submarines as it can resist salt water corrosion.

It is also used for making bronze sculptures, Bronze

top-quality bells, medals, clips, electrical connectors and springs.

FACT WITH REASON

Bronze is used in ship fittings. Why?
Bronze is used in ship fittings because it is tough and can resist salt water corrosion.

Modern Concept Science and Environment - 7 167

Differences between brass and bronze.

S.N. Brass S.N. Bronze

1 Brass is a metallic alloy of copper 1 Bronze is a metallic alloy of

and zinc. copper and tin.

2 It is yellow in colour. 2 It is reddish brown in colour.

Some Useful Non-metals

a) Sulphur

Sulphur is a non-metal. Its symbol is ‘S’. It is Sulphur powder
odourless, tasteless and light yellow element. It
occurs naturally in the form of solid in both free MEMORY PLUS
and combined state. It is the most important Vulcanization is a chemical process
non-metal in the chemical industries because it for converting natural rubber into
is used for manufacturing sulphur compounds more durable materials by the
like sulphuric acid, sulphites, etc. Medicinally addition of sulphur.
it is used to manufacture sulpha drugs. It is also
used for the production of matches, vulcanized
rubber, dyes and gunpowder. Firecrackers are
filled with gunpowder. Sulphur is also used as
an important ingredient for the manufacturing
of fungicide.

b) Iodine

Iodine is a volatile non-metal. Its symbol is ‘I’.

It is a blue black solid at room temperature.

Iodine  was  first  extracted from seaweed

residue. It is slightly soluble in water. Iodine

is one of the important trace elements needed

for human body. It has a growth controlling

and metabolic function. The deficiency of

iodine in the diet of a pregnant women retards Iodine

the mental growth of a fetus. Iodine deficiency also causes goitre. A goitre is a

swelling in the neck resulting from an enlarged thyroid gland. Iodised salt is the

major source of iodine for us. Open and sunlight exposed salts contain no or less

iodine. So, we should not consume such salts.

Iodine along with potassium iodide is dissolved in alcohol solution to make
tincture of iodine. It is used as an antiseptic and disinfectant. A disinfectant kills
microorganisms and antiseptic prevents the growth of microorganisms. Iodine
is also used to make iodex ointment and iodex balm. Iodex ointment contains

168 Metals and Non-metals

4.7% iodine which is commonly used as topical antiseptic. Iodex Balm is an
ayurvedic pain relief balm. It provides warm and peaceful effect that relieve pain.
Compounds of iodine are used in photography, making dyes, germicides, etc.

FACT WITH REASON

We should use Iodised salt. Why?
Iodised salt contains iodine. It is an important nutrient in our body for physical and mental
development. The thyroid gland in our body uses iodine to make thyroid hormone. If the salt is kept
open for long time or cooked at higher temperature then the volatile iodine might evaporate entirely.

STEPS EXERCISE

STEP 1

1. Fill in the blanks with appropriate words.
a) Metals possess shiny property called metallic …………
b) ………… is a non-metal which is used for making electrodes.
c) Metalloids are widely used for making…………
d) ………… does not occur in alloys.
e) ………… is an alloy used for making medals.
f) ………… is a liquid non-metal.

2. Write True for the correct and False for the incorrect statements.
a) Metals have high melting point.
b) Non-metals occur in different states.
c) Sulphur is a metalloid.
d) Alloys are the mixtures of two or more metals.
e) Steel is an example of metalloid.
f) Metalloids only have the properties of metals.

STEP 2

3. Answer the following questions in one word.
a) What kind of property allows metal to be beaten into thin sheets?
b) What is the shining property of a metal called?
c) Name an alloy formed by mixing copper and tin.

Modern Concept Science and Environment - 7 169

d) Which metal is liquid at normal temperature and pressure?
e) What is the name of a non-metal that is a good conductor of electricity?

4. Write any two differences between:
a) Metals and non-metals
b) Brass and bronze
c) Metalloids and alloys

5. Give reasons.
a) Copper is used to make electrical wires.
b) Cooking utensils are made up of alloys.
c) Bronze is used in ship fittings.
d) We should use iodised salt.
e) Iodized salts must be packed.

STEP 3

6. Answer the following questions
a) In which major three groups elements are divided?
b) What are metals? Write down any four examples.
c) Write down any four properties of metals.
d) What are non-metals? Write down any four exampls.
e) What are metalloids? Write down any three examples.
f) What are alloys? Write down any three examples.
g) For what purpose brass and bronze are used?
h) Mention any two properties each of sulphur and iodine.
i) List two important uses each of sulphur and iodine.
j) Write the composition of each of brass and bronze.

7. Name the metal or non-metal or alloy used in:
a) Sulfa drugs
b) Antiseptic or disinfectants
c) Ship fittings

8. Write the name of metals, non-metals and metalloids found or used in your
daily life and list their uses.

170 S ome U sEestfimualteCdhteeamcihcinaglpseriods Theory Practical
UNIT 5 1

14 Some Useful Chemicals

Syllabus issued by CDC Dettol

 Some useful chemicals
– Phenol and its uses
– Dettol and its uses
– Detergent and its uses
– Chemical fertilizers and their uses

LEARNING OBJECTIVES

At the end of this unit, students will be able to:
 introduce phenol, dettol, detergent and chemical fertilizers.
 tell the uses of phenol, dettol, detergent and chemical fertilizers.

Key terms and terminologies of the unit

1. Useful chemicals: All those chemical substances that are synthesized in the
laboratory and industry for our use are called useful chemicals.

2. Phenol: Phenol is an aromatic organic compound of alcohol group.

3. Dettol: Dettol is an antiseptic and disinfectant liquid made up of a
chemical called chloroxylenol.

4. Detergent: Detergent is a synthetic cleansing agent in the form of liquid or
powder. It is capable of dissolving dirt and oil.

5. Chemical fertilizers: Chemical fertilizers are water soluble chemical substances
that are added in the soil to increase fertility of soil.

6. Compost manure: Compost manure is the organic fertilizer that is made from a
mixture of different types of dead and decayed organic wastes.

14.1 Introduction

Chemicals are our friends in this scientific era. All those chemical substances that are
synthesized in the laboratory or industry for our use are called useful chemicals. Our
day starts from the use of chemicals and ends also with the use of chemicals. The soap
that we use for bathing and washing is a chemical substance. The toothpaste that we

Modern Concept Science and Environment - 7 171

use to brush our teeth, the boot polish that we use to shine our shoes, etc. are also
chemicals. The processed foods and chocolates also contain different types of edible
chemicals. Paints, fertilizers, antiseptic liquids, detergents, etc. are also the examples
of chemicals. Some chemicals are useful while some are harmful. If not handled
properly, harmful chemicals may harm or kill us. In this unit, we will discusses some
of the important chemicals that we use widely in our daily lives.

Some chemicals

Phenol

Phenol is an aromatic organic compound of alcohol group. It has a
distinct odour. It is slightly soluble in water at room temperature but
highly soluble in hot water. Phenol is manufactured from coal tar which
is a fossil fuel (petroleum product). It has disinfectant property. It is a
useful chemical substance which is used to clean and disinfect floors
and toilets in hospitals, clinics, laboratories, schools and at homes. A
concentrated solution of phenol is corrosive and may corrode our skin.

FACT WITH REASON

Why should we use concentrated phenol carefully?
A concentrated solution of phenol is corrosive. Its concentrated solution corrodes human skin
and eyes. So, we should use phenol carefully.

Uses of Phenol
1. Phenol is used for cleaning working desk in medical and biological laboratories.
2. It is used to clean wounded parts.
3. It is used to sterilize surgical instruments in hospitals and laboratories.
4. It is used to clean toilets.
5. It is also sprayed at insect breeding sites to get rid of insects.

Dettol

Dettol is an antiseptic and disinfectant liquid which is manufactured
from a chemical called chloroxylenol. A disinfectant is a chemical that is
used to kill microorganisms in floors, toilets, etc. Likewise, an antiseptic

172 Some Useful Chemicals

is a chemical that prevents the growth of microorganisms. Dettol is a light yellow
liquid which has characteristic odour. It dissolves in water to form a milky white
emulsion.

Like Phenol, Dettol is used in hospitals and homes. Dettol should be used very
carefully as it can cause adverse health impacts if inhaled or ingested.
Uses of Dettol
1. Dettol is most commonly used as an antiseptic liquid to clean cuts and wounds.
2. It is mixed with water for bathing.
3. It is also used for washing clothes especially of babies.
4. It is also used as a cleansing agent to maintain sanitation in basins, tables, floors, etc.
5. It is also used for pest control purposes.

Differences between Phenol and Dettol

S.N. Phenol S.N. Dettol

1 Phenol is an aromatic organic 1 Dettolis anantisepticanddisinfectant

compound of alcohol group. liquid made up of chloroxylenol.

2 Pure phenol is colourless. 2 Dettol is yellowish brown in colour.

Detergent

Detergent is a synthetic cleansing agent in the form of liquid or
powder which is capable of dissolving dirt and oil. Detergents are
usually organic compounds with minerals in them. Detergents are
also called surfactants as they act on the surface of the materials
and dissolve dirt and oil. Detergents are readily soluble in water.
They have particular odour and colour based on their composition.
Detergents do not contain salts as like that in soap. But it shows the properties of soap.
So, detergent is also called a soapless soap. Detergents contain non-biodegradable
substances that cause water pollution. Plants get affected if we discharge water
containing detergent in the roots of plants. So, we should use biodegradable detergents
as far as possible.

FACT WITH REASON

Many countries banned the phosphate containing detergents. Why?

Phosphates in detergents when get mixed in water bodies, they lead to a harmful algal bloom.
These algae suck the dissolved oxygen from water and cause a deficiency of oxygen for other
aquatic plants and animals. Thus, many countries have banned the use of phosphates containing
detergent, including the European Union and the United States.

Modern Concept Science and Environment - 7 173

Uses of Detergents

1. Detergents are mostly used for laundry purposes like washing clothes and
utensils.

2. Detergents are used as fuel additives to prevent fouling in engines.
3. They are used for washing the floors and walls.

FACT WITH REASON

Detergents are also called surfactants, why?
Detergents are also called surfactants because they have surface active chemicals that dissolve
dirt and oil.

Chemical Fertilizers

The water soluble chemical substances that are added in the soil to increase fertility
of soil are called chemical fertilizers. Chemical fertilizers provide the minerals needed
in the soil. Examples of such minerals are nitrogen, potassium, phosphorus, etc. It
results increase in the productivity of crops.

FACT WITH REASON

Chemical fertilizers are widely used in agriculture, why?
Chemical fertilizers are widely used in agriculture because they dissolve quickly in water and are
easily absorbed by plants. As a result the productive of crops increases.

Compost manure is an organic fertilizer that is made

from the dead, decayed and decomposed organic

wastes. Compost manure may not provide the

minerals required by the plants quickly as like the

chemical fertilizers. Due to this reason, chemical

fertilizers are widely used. Urea, NPK fertilizer,

DAP, calcium phosphate, etc. are some of the

examples of chemical fertilizers. However, the MEMORY PLUS

excess and prolonged use of chemical fertilizers Our urine can be used in place of
can destroy the composition of soil and its fertility. organic fertilizer as it contains nitrogen,
phosphorus and potassium in it.
FACT WITH REASON

Why is compost manure better than chemical fertilizer?
Compost manure is better than chemical fertilizers because:
i) It does not alter the natural composition of soil.
ii) It does not pollute air, water and soil.
iii) It increases fertility of soil in long run.

174 Some Useful Chemicals

There are many minerals needed by the plants for their healthy growth and
development. However, nitrogen, phosphorous and potassium are the chief ones.

Importance of nitrogen in plants

Nitrogen is a main element for protein synthesis in plants. It is essential for the growth
of plants. It also increases the biomass of plant, help in photosynthesis and other vital
functions. Lack of nitrogen in the soil causes early drop of leaves, early maturation,
lack of proper growth and yellowing of leaves. Chemical fertilizers like urea, NPK
(Nitrogen Phosphorus Potassium), DAP (Diammonium phosphate), ammonium
sulphate, etc. provides nitrogen to plants.

Importance of phosphorus in plants

In plants, phosphorus encourages formation of roots and their growth. Phosphorus
increases formation of flowers and fruits. It also helps the development of quality
seeds. Phosphorus is essential for maintaining healthy and strong plants. It increases
ripening time of fruits. The lack of phosphorous in the soil causes less development
of fruits, seeds and roots. The use of phosphorus fertilizers prevents these problems
in the plants and also help in proper development of leaves and buds. Chemical
fertilizers like DAP, calcium super phosphate, ammonium phosphate, bone meal, etc.
provide phosphorous to the plants.

Importance of potassium in plants

Potassium is very important mineral for plant immunity. Deficiency of potassium in
the soil decreases immunity of plants, loss of chlorophyll from leaves, decrease in size
and quality of food grains, stunted growth and so on. Use of potassium in soil can
avoid these problems. Chemical fertilizers like potassium sulphate, potassium nitrate,
NPK, potassium chloride, etc. provide potassium to the plants.

FACT WITH REASON

Plants grow better when we use NPK fertilizer. Why?
Plants grow better when we used NPK fertilizer because it supplies all the three necessary nutrients
viz. nitrogen, phosphorous and potassium to the plants compared to other fertilizers.

Differences between chemical fertilizer and compost manure.

S.N. Chemical fertilizers S.N. Compost manure

1 Chemical fertilizers are the water 1 Compost manure is the natural or

soluble chemical substances that organic fertilizer that is made from

are used to increase the fertility of dead, decayed and decomposed

the soil. organic wastes.

2 Chemical fertilizers increase the 2 Compost manure does not change

acidity of soil. the acidity of the soil.

Modern Concept Science and Environment - 7 175

ACTIVITY 1

Prepare the list of chemicals that are used at your home. Also mention one use of each.

Differences between the role of nitrogen and potassium in plants.

S.N. Role of nitrogen in plants S.N. Role of potassium in plants

1 Nitrogen is necessary for growth 1 Potassium is necessary to increase

and development of plant body. disease resistance in plants.

2 Nitrogen is used for formation of 2 Potassium is used for proper size

plant body as it is the main source and quality of grains.

of protein.

STEPS EXERCISE

STEP 1

1. Fill in the blanks with appropriate words.
a) …...…… are the friends of scientific era.
b) Phenol is an organic compound of …...…… group.
c) Dettol is mixed with water for …...…….
d) …...…… are mainly used in laundry.
e) Nitrogen is a main element for ……………synthesis.
f) Deficiency of ……………….. in soil causes immunity problem in plants.

2. Write True for the correct and False for the incorrect statements.
a) Chemicals can be harmful to us if not used properly.
b) Phenol is widely used for cleaning toilets.
c) Dettol is an anticeptic liquid.
d) All detergents are non-biodegradable.
e) Urea is an example of compost manure.
f) Bone meal is an example of phosphorus fertilizer.

STEP 2

3. Answer the following questions in one word.
a) Name a chemical product which has disinfectant property.
b) Which chemical fertilizer gives nitrogen, potassium and phosphorus?
c) Deficiency of which fertilizer in soil causes decrease in immunity of plants?
d) Which group of chemical do phenols belong to?
e) Which element is necessary for protein synthesis in plants?

176 Some Useful Chemicals

4. Differentiate between:
a) Phenol and Dettol
b) Chemical fertilizers and organic manure
c) Role of nitrogen in plants and role of potassium in plants.

5. Give reasons.
a) We should use concentrated phenol carefully.
b) Detergents are also called surfactants.
c) Chemical fertilizers are widely used in agriculture.
d) Compost manure is better than chemical fertilizer.
e) Plants grow better when we use NPK fertilizer.

6. Complete the following table with the chemicals that are used at your home
or locality.

English name of Nepali Elements/ Major uses
chemical name Compounds

STEP 3

7. Answer the following questions
a) What are chemicals? Why should we use chemicals in a proper way?
b) What is phenol? List any two properties and two uses of phenol.
c) What is Dettol? Mention any two important uses of Dettol.
d) What is a detergent? Write its uses.
e) What are chemical fertilizers? Write any any five examples.
f) Define compost manure? Why is it better than chemical fertilizer?
g) Write down the importance of nitrogen in plants.
h) Explain the importance of phosphorus for plants.
i) Write down the importance of potassium for plants.
j) Write deficiency symptoms of nitrogen in plants.
k) List any two effects of deficiency of phosphorous in plants.
l) What are the symptoms shown by the plants that lack potassium? Write
any two points.
m) Give any three examples of nitrogen, phosphorus and potassium containing
fertilizers each.

UNIT Estimated teaching periods TheorMyoderPnraCcotniccaelpt Science and Environment - 7 177
61
15
Living Beings: Animal Life

Syllabus issued by CDC Peacock

 Vertebrates
 – Cold-blooded animals
 – Warm-blooded animals
 Pisces - Characteristics and examples
 Amphibia - Characteristics and examples
 Reptilia - Characteristics and examples
 Aves - Characteristics and examples
 Mammalia - Characteristics and examples
 Life cycle of frog

LEARNING OBJECTIVES

At the end of this unit, students will be able to:
 classify vertebrates and explain their characteristics.
 describe the life cycle of frog with a neat and labelled figure.

Key terms and terminologies of the unit

1. Cold blooded animals: Those animals whose body temperature changes according
to the environmental temperature are called cold blooded
animals.

2. Warm blooded animal: Those animals whose body temperature does not change
according to the environmental temperature are called
warm blooded animals.

3. Hibernation: Hibernation is a winter sleep of animals to save themselves
from the extreme cold.

4. Aestivation: Aestivation is a summer sleep of animals to save themselves
from hot and arid conditions.

5. Oviparous animals: Animals that reproduce by laying eggs are called oviparous
animals.

6. Viviparous animals: Animals that reproduce by giving directly birth to the young
ones are called viviparous animals.

178 Living Beings: Animal Life

7. Vertebrates: Those animals that have backbone (vertebral column) i n their body are
called vertebrates.

8. Pisces: The gill-bearing vertebrate aquatic and cold blooded animals are called
pisces.

9. Amphibia: The cold blooded vertebrate animals that live both in water and on land
to complete their life cycle are called amphibia.

10. Reptilia: The cold blooded crawling vertebrates which show respiration through
lungs are called reptilia.

11. Aves: The warm blooded vertebrate animals which have wings and feather on
their body are called called aves.

12. Mammalia: The warm blooded vertebrate animals which have mammary glands in
their females are called called mammals.

13. Life cycle: The series of stages through which an organism pass is called life cycle.

15.1 Introduction

The earth is home to many living beings. There are variety of plants and animals
living on the earth. This variety of animals living on the earth is more familiar to us.
Animals show many similarities and dissimilarities amongst each other. To make the
study easier, faster and more convenient, animals are classified into different groups
and sub-groups. They are as follows.

Cold blooded and Warm blooded Animals

a) Cold Blooded Animals MEMORY PLUS

Those animals whose body temperature Cold blood animals are also known as
poikilothermic animals.
changes according to the environmental

temperature are called cold blooded animals. Cold blooded animals cannot

maintain their body temperature constant. It changes with the environmental

temperatures. During summer season, their body temperature increases

according to the environmental temperature and during winter, the body

temperature gets decreased. Examples of cold blooded animals are fish, frog,

snakes, lizards, etc.

Shark Rohu Salamander Cobra Frog

Modern Concept Science and Environment - 7 179

Cold blooded animals are affected by the variation of environmental temperature.

Most of the cold blooded animals undergo hibernation and aestivation. It is

because they cannot bear extreme cold and hot conditions. Hibernation is a

winter sleep of animals to save themselves from the extreme cold conditions. It

usually lasts for a long time. Some animals hibernate for the whole winter.

Aestivation is a summer sleep of animals to save themselves from hot and arid

conditions. It usually lasts for a short time;

sometimes for a day as nights are cooler MEMORY PLUS

compared to days. Animals like snails, The animals belonging to classes
earthworm, bees, salamanders, frog, toads, Pisces, Amphibia and Reptilia are cold
lizards, crocodiles, snakes, turtles etc. undergo blooded animals.

hibernation and aestivation.

FACT WITH REASON

Cold blooded animals go for aestivation or hibernation, why?
Body temperature of cold blooded animals changes with the environmental temperature.
They go for hibernation to save themselves from extreme cold. Similarly, they go for
aestivation to save themselves from extreme hot and arid conditions.

b) Warm Blooded Animals MEMORY PLUS

Those animals whose body temperature does The normal body temperature of
not change according to the environmental human is 370C or 98.60F. It remains
temperature are called warm blooded animals. constant in spite of change in
Examples of warm blooded animals are birds, weather conditions. Our body
dogs, cats, monkey, human beings etc. Warm- organs do not work properly if the
blooded animals require a lot of energy to temperature increases above or
maintain a constant body temperature. They below 98.60F. We should protect our
use their internal energy to cool the body body from extreme hotness and
coldness.

during summer and to heat the body during winter. Thus, they maintain a

constant body temperature.

Usually, warm blooded animals do not go for hibernation and aestivation. But,
small birds, kangaroo, mouse, bats, bears, etc. go for hibernation.

Pigeon Parrot Peacock

180 Living Beings: Animal Life

Elephant Tiger Bear

Differences between cold blooded animals and warm blooded animals

S.N. Cold blooded animals S.N. Warm blooded animals

1 Those animals whose body 1 Those animals whose body

temperature changes according temperature does not change

to the environmental temperature according to the environmental

are called cold blooded animals. temperature are called warm

blooded animals.

2 Hibernation is more common in 2 Hibernation is less common in

these animals. Examples: frog, these animals. Examples: man,

fish, salamander, etc. dog, bear, etc.

FACT WITH REASON

Snakes are not seen during winter season. Why?
Snakes are cold blooded animals. They go for hibernation during extreme cold to protect
themselves. So, snakes are not seen during winter season.

ACTIVITY 1

Look at your surroundings. List any five cold blooded and five warm blooded animals
found in your place.

Oviparous and Viviparous Animals

a) Oviparous Animals

Animals that reproduce by laying eggs are called oviparous animals. Examples
of oviparous animals are insect, fish, frog, snake, crocodile, bird, etc. Female
oviparous animals lay eggs. Usually the smaller animals lay more eggs but only
few eggs can survive. Larger animals lay less number of eggs and most of them
survive. Young ones of oviparous animals develop inside the eggs and hatch out.

Fish Frog Crocodile Pigeon

Modern Concept Science and Environment - 7 181

FACT WITH REASON

Frog is an oviparous animal. Give reason.
Frog is an oviparous animal because the female frog lays eggs in water.

a) Viviparous Animals
Animals that reproduce by giving directly birth to the young ones are called
viviparous animals. Examples of viviparous animals are dog, bat, cat, mouse,
lion, human being, etc. Viviparous animals give birth to only few young ones.
In most of the cases, the young ones in viviparous animals get developed inside
the womb of the female animals.

Rhino Cow Dog Tiger

FACT WITH REASON

Why are mammals called viviparous animals?
Mammals give direct birth to their young ones. So, they are called viviparous animals.

ACTIVITY 2

Mention any four oviparous and four viviparous animals present in your surrounding.

15.2 Vertebrates

Those animals that have backbone (vertebral column) in their body Vertebral column
are called vertebrates. A backbone is a long skeletal structure in
the back of the vertebrates which is made up of small bones called
vertebrae. Backbone runs from skull to pelvis. Fish, frog, turtle, snake,
pigeon, bat, cow, human beings, etc. are some examples of vertebrates.
Vertebrates belong to a phylum called Chordata. All chordates do not
have backbone.

Vertebrates are divided into five major classes. They are:

a) Pisces b) Amphibia c) Reptilia d) Aves

e) Mammalia

182 Living Beings: Animal Life

a. Pisces

The gill-bearing vertebrate aquatic and cold blooded animals are called Pisces.
Examples of Pisces are: salmon, tuna, rohu, eel, etc.

Seahorse Shark Rohu

Major characteristic features of the animals belonging to class Pisces are mentioned
below:

(i) They are aquatic animals.

(ii) They breathe through gills.

(iii) They have two chambered heart.

(iv) They are oviparous.

(v) They are cold blooded animals.

(vi) They have streamlined body. Streamlined body reduces water resistance and
helps them to float in water.

(vii) Their body is covered with scales and waxy skin to prevent themselves from
decaying.

(viii) They have fins for swimming and caudal fin for changing direction and balancing
body.

ACTIVITY 3

Get a fish from cold storage or an aquarium store. Study its external body features and
sketch its diagram.

b. Amphibia

The cold blooded vertebrate animals that live both in water and on land to complete
their life cycle are called Amphibia. Class Amphibia consists of amphibians. Examples
of some amphibians are hyla, frog, salamander, toad, etc.

Frog Toad Salamander Hyla

Modern Concept Science and Environment - 7 183

Some of the major characteristic features of the animals belonging to class Amphibia
are mentioned below:
(i) They live both in water and on land to complete their life cycle.
(ii) They have three chambered heart.
(iii) They are oviparous.
(iv) They are cold blooded animals.
(v) They breathe through gills and moist skin in water. While, they breathe through

lungs on land.
(vi) They have pointed anterior body part and wide posterior body part. It allows

them to reduce water resistance while swimming.
(vii) Their body is covered with glands and rough scales.
(viii) They have strong and longer hind limbs for hopping on the ground.
(ix) They have webbed feet for swimming in water.

FACT WITH REASON

Why is a frog kept in the class Amphibia?
Frog is kept in the class Amphibia because it needs water to complete its life cycle but lives
on land.

ACTIVITY 4

Observe any two amphibians. Describe their external body structure and draw them
in your copy.

c. Reptilia

The cold blooded crawling vertebrates which show respiration through lungs are
called Reptilia. The animals present in the class Reptilia are called reptiles. Examples
of reptiles are snake, turtle, crocodile, alligator, etc.

Wall lizard Tortoise Crocodile Snake

Some of the major characteristic features of the animals belonging to class Reptilia are
mentioned below:

(i) Most of the reptiles live on land and some of them live in water.

184 Living Beings: Animal Life

(ii) They have three chambered heart.
(iii) They are oviparous.
(iv) They are cold blooded animals.
(v) They breathe through lungs.
(vi) They have reduced limbs or no limbs.
(vii) Their body is covered with dry, rough and/or spiny scales.

FACT WITH REASON

Snakes are called reptiles, why?
Snakes are called reptiles because they crawl on the ground and have three chambered heart.

d. Aves

The warm blooded vertebrate animals which have wings and feather on their body
are called called aves. Examples of birds are pigeon, crow, sparrow, swallow, ostrich,
hen, parrot, etc.

Giant Hornbill Koel Crow

Saras (crane)

Sparrow

Danphe Peacock

Some of the major characteristic features of the animals belonging to class Aves are
mentioned below:
(i) Most of aves are adapted for flying.
(ii) They breathe through lungs.
(iii) They have four chambered heart.
(iv) They are oviparous.
(v) They are warm blooded animals.
(vi) They have streamlined or boat shaped body for flying in the air.

Modern Concept Science and Environment - 7 185

(vii) Their body is covered with fluffy and light feathers. Feathers make them warm
and light in weight.

(viii) Their fore limbs are modified into wings for flying.
(ix) They have toothless beak.
(x) They have pneumatic (hollow porous) bones. Pneumatic bones make them light

for flying.

ACTIVITY 5

Observe a bird and list its four major external features.

e. Mammalia

The warm blooded vertebrate animals which have mammary glands in their females
are called called mammals. Examples of mammals are: mouse, rat, bat, dolphin,
whale, rabbit, monkey, squirrel, dog, cat, human beings, etc.

Bat Kangaroo Squirrel

Ghoral Tiger Great Tibetan Sheep

Elephant Yak Rhinoceros

Some of the major characteristic features of animals belonging to the class Mammalia
are mentioned below:

(i) Most of the mammals live on land but some animals like the dolphin and whale
live in water.

(ii) They have a pair of external ears. MEMORY PLUS
(iii) Their body is covered with hairs.
(iv) Their body is divided into head, neck and 1. All mammals except spiny ant
eaters and pangolins have teeth in
trunk. them.
(v) They breathe through lungs.
2. Duck-Billed Platypus and the spiny
ant eater are mammals but lay eggs.

186 Living Beings: Animal Life

(vi) They have four chambered heart.
(vii) They are viviparous and show parental care.
(viii) They are warm blooded animals.
(ix) The females of mammals have mammary glands in their body which produces

milk to nourish their young ones.

Differences between pigeon and bat

S.N. Pigeon S.N. Bat

1. Pigeon has wings and feathers to 1. Bat has patagium to fly and hair in
fly. its body.

2. Pigeon lays egg and hatch its 2. Bat gives direct birth to its young
young ones. ones.

FACT WITH REASON

Why do female mammals have mammary glands?
Female mammals have mammary glands to feed their baby with essential nutrients.

Differences between Aves and Mammalia

S.N. Aves S.N. Mammalia

1 The warm blooded vertebrate 1 The warm blooded vertebrate

animals which have wings and animals which have mammary

feather on their body are called glands in their females are called

called aves. called mammals.

2 Aves lay eggs with hard shell. 2 Most mammals give direct birth
Examples: hen, sparrow, etc. to their young ones.

Examples: human, cow, horse, etc.

15.3 Frog Male frog Female frog

Frog is a cold blooded amphibian. Its scientific
name is Rana tigrina. Its body is divided into
head and trunk. Its anterior part is pointed and
posterior part is wide. It contains a pair of fore
limbs and hind limbs. The hind limbs are longer
than the fore limbs. Frogs have webbed feet which
help them to jump into the water and swim. They
breathe through moist skin inside water and

Modern Concept Science and Environment - 7 187

lungs on land. The tadpoles breathe with the help of gills. Frogs prefer to live near
water sources like ditches, ponds, lakes or river.

Life cycle of a frog Tadpole

The series of stages through which an Metamorph
organism pass is called life cycle. The life
cycle of a frog is completed in three stages. Eggs
But, before that, we need to understand
how frog reproduces.

Frog reproduces during the rainy season.

Male frogs go near the water bodies and

produce a croaking sound. This is also

known as sex call. Actually, by producing

this sound, the males are calling the females Frog (adult)

for mating. Female frogs follow the sound Lifecycle of frog

and reach the males. Male frog holds the female frog tightly and female releases eggs

in water. The male frog also releases sperms in water. Now, fusion of eggs with sperms

takes place in water. In this way external fertilization takes place in frog.

Frog undergoes three distinct stages during its life cycle. They are: eggs, tadpole and
adult frog.

a) Egg 

A frog can lay hundreds to thousands of eggs

at a time. A floating clump of eggs is called frog

spawn. Not all eggs hatch into young ones. Some

eggs are eaten by aquatic animals while some

are destroyed by sunlight. The rest of the eggs

survive. When sperms of the frog meet the eggs,

they get fertilized. The fusion of a sperm and an Eggs of frog
egg is called fertilization. The fused structure

formed after fertilization is called zygote. The zygote divides continuously

and forms an embryo. The embryo takes nutrients from the yolk and develops

organs and gills in about 21 days.

b) Tadpole

After its 21 days of development, the embryo Tadpole of frog
leaves its jelly shell and attaches itself to a weed
in water. This quickly becomes a tadpole.  The
tadpoles grow until they are big enough to

188 Living Beings: Animal Life

swim freely in water.  This can take from 3 days to 3 weeks, depending on the
type of frog.  They eat very small plants that are present in water. Tadpoles are
always in danger because they can be eaten by other organisms.

After about five weeks, the tadpole begins to change. It starts to grow
hind limbs first and then forelimbs.  Bulges appear behind their heads
where the forelimbs are growing. Lungs also begin to develop. They start
to wiggle on the surface to breathe in air.  The tail makes tadpole possible
to swim around and catch food.  They eat plants and decaying animal
matter.  Some tadpoles also eat eggs of frogs and other small tadpoles.
Over time, the tadpole becomes like a frog. They shed their skin and lips. Their
mouth widens and loses its horny jaws. The tail becomes much smaller and the
legs grow. The lungs are almost functioning at this point.

c) Adult Frog

Eleven weeks after the eggs are laid, a fully

developed frog with lungs and legs emerges

from the water. This frog will live mostly on

land with occasional swimming in water. The

tiny frogs begin to eat insects and worms.

Male frogs live near the moist places or near

water sources. When they grow up, they start Adult frog

crocking to attract females. And again, males

and females mate. The females produce eggs and thus the life cycle continues.

STEPS EXERCISE

STEP 1

1. Fill in the blanks with appropriate words.
a) ……… have backbone in their body.
b) Phylum ……… is the phylum of vertebrates.
c) A crocodile lies in the class ………
d) Snakes are ……… blooded animals.
e) ……… is an oviparous animal.
f) Mammary glands of mammals produce ……… for their young ones.

Modern Concept Science and Environment - 7 189

2. Write True for the correct and False for the incorrect statements.
a) Aestivation is usually a short sleep during summer.
b) Frogs undergo hibernation.
c) A turtle is an amphibian.
d) Birds have pneumatic bones in their body.
e) Reptiles have a pair of external ears.
f) Young ones of mammals develop in the womb of females.

STEP 2

3. Answer the following questions in one word.
a) What is the term used for summer sleep?
b) Which class of vertebrates does hen belong to?
c) What type of fertilization takes place in frogs?
d) Name a classes of vertebrates with homeothermic animals.
e) Give an example of an oviparous animal.

4. Differentiate between:
a) Warm blooded animals and cold blooded animals
b) Hibernation and aestivation
c) Amphibian and reptiles
d) Oviparous animals and viviparous animals
e) Bat and pigeon

5. Give reasons.
a) Animals are classified into different groups.
b) Cold blooded animals go for aestivation or hibernation.
c) Frog is an oviparous animal.
d) Mammals are called viviparous animals.
e) Snakes are reptiles.
f) Frog is kept in a class Amphibia.
g) Female mammals have mammary glands.

190 Living Beings: Animal Life

6. Identify the classes of animals shown below and write one of the most
important feature of that animal.

a) b) c) d) e)

STEP 3

7. Answer the following questions
a) What are cold blooded animals? Write any three examples.
b) What are warm blooded animals? Write any three examples.
c) Name the different classes of vertebrates with three examples of each.
d) List out any four important features of animals in the class Pisces.
e) List out any four important features of animals in the class Amphibia.
f) What are the characteristic features of Reptiles? List any four.
g) What are aves? What makes the birds adapted for flying mode of life? Give
any four reasons.
h) What are mammals? List out any four major features of mammals.
i) What is life cycle?
j) How does a tadpole develop?
k) What do you mean by hibernation? Write any four examples of animals
that hibernate.
l) Which class of the vertebrates shows the following features? Name the
class and give any two examples of such animals.
i) It has moist skin to respire on the land and webbed feet for swim-
ming in water.
ii) Its fore limbs are modified into wings for flying.
iii) It has scales on the body and respires through gills.
iv) It has modified scales on the body and respires through lungs.
m) Write any two major characteristics of the following animals:
i) Crow ii) Dog iii) Salmon

8. Draw a labelled diagram to show life cycle of frog and explain the different
stages.

UNIT Estimated teaching periods TheoMryoderPnraCcotniccaepl t Science and Environment - 7 191
61
16
Living Beings: Plant Life

Syllabus issued by CDC Lotus

 Classification of plants
 Cryptogams and its divisions
 Phanerogams and its divisions
 Structure of a flower

LEARNING OBJECTIVES

At the end of this unit, students will be able to:
 classify non-flowering and flowering plants and state their characteristics.
 explain the structure of a flowering plant with a labelled figure.
 describe the structure of a flower.

Key terms and terminologies of the unit

1. Cryptogams: Cryptogams are the non-flowering plants which reproduce without
seeds.

2. Phanerogams: Phanerogams are the flowering plants which reproduce through
seeds.

3. Thallophytes: Those plants whose body cannot be differentiated into leaves,
stem and roots are called thallophytes.

4. Thallus: A plant body that cannot be differentiated into leaves, stem and
roots is called thallus.

5. Algae: Algae are the group of autotrophic green thallus plants.

6. Fungi: Fungi are the group of heterotrophic non-green thallus plants.

7. Bryophytes: Bryophytes are the cryptogams without vascular bundles. They
are found in wet and shady places and depend on water for sexual
reproduction.

8. Pteridophytes: Pteridophytes are the cryptogams with vascular bundles. They
have feather like leaves.

9. Angiosperms: Angiosperms are the phanerogams which have seeds enclosed
inside fruits.

192 Living Beings: Plant Life

10. Gymnosperms: Gymnosperms are the phanerogams which have naked seeds.

11. Monocotyledons: Angiosperms with one cotyledon in their seeds are called
monocotyledons.

12. Dicotyledons: Angiosperms which have two cotyledons in their seeds are called
dicotyledons.

13. Venation: The arrangement of veins and veinlets in the leaf lamina is called
venation.

14. Flower: Flower is the reproductive part of the plant.

15. Calyx: The group of sepals that forms the outermost whorl of a flower is called
calyx.

16. Corolla: The colourful part of the flower which is formed by the group of
petals is called corolla. It forms the second whorl of a flower.

17. Androecium: The group of stamens or male reproductive parts that forms the
third whorl of a flower is called androecium.

18. Gynoecium: The carpel (pistil) or group of carpels that forms the innermost
whorl of a flower is called gynoecium.

19. Unisexual flower: The flower that contains only one reproductive part (either male or
a female part) is called a unisexual flower.

20. Bisexual flower: The flower that contains both male and the female reproductive
parts in the same flower is called a bisexual flower.

21. Pollination: The process of transfer of pollen grains from anther of androecium
to stigma of gynoecium is called pollination.

22. Self-pollination: The transfer of pollen grains from anther to stigma of the same
flower or different flowers of the same plant is called self-

pollination.

23. Cross pollination: The transfer of pollen grains from anther to stigma of the different
flowers of different plants of the same species is called cross-

pollination.

24. Fertilization: The process of fusion of male gamete (sperm) with the female
gamete (egg) to form a zygote is called fertilization.

25. Zygote: Zygote is a diploid cell formed from the fusion of a male and a
female gamete.

26. Embryo: An embryo is a multicellular structure formed from the growth of a
zygote.