Science 7

Suspend ͗ ŚŽůĚ ŝŶ Ă ƐƚĂƟŽŶĞƌLJ ƉŽƐŝƟŽŶ

Electric generator : a device which produces electricity by using mechanical energy

Motor pump ͗ Ă ŵĞĐŚĂŶŝĐĂů ĚĞǀŝĐĞ ǁŚŝĐŚ ŝƐ ƵƐĞĚ ƚŽ ƉƵŵƉ ůŝƋƵŝĚ

Telegraph : a system for transferring message for a long distance along a wire

Dynamo : a small device which produces electricity by using mechanical
energy

DĂŐŶĞƟĐ ĐŽŵƉĂƐƐ ͗ Ă ĚĞǀŝĐĞ ǁŚŝĐŚ ĐŽŶƚĂŝŶƐ Ă ƐŵĂůů ŵĂŐŶĞƚ ƵƐĞĚ ĨŽƌ ĚĞƚĞĐƟŶŐ
ĚŝƌĞĐƟŽŶ

Main Points to Remember

1. A substance which attracts magnetic substances and rests pointing
north-south directions when freely suspended is called magnet.

2. The property of a magnet is called magnetism.
3. Like poles of magnets repel whereas the unlike poles attract each

other.
4. Magnetic poles always exist in pair, i.e. poles of magnet can never

be separated.
5. The process of losing the magnetic property from a magnet is called

demagnetization.
6. The process of turning a magnetic substance into a magnet is called

magnetization.
7. A magnetic substance can be magnetized by stroking method and

electrical method.

Exercise

1. Choose the best alternative in each case.

a. A freely suspended magnet always comes to rest showing

i. North-south directions ii. East-west directions

iii. North-east directions iv. West- south

b. Which of the following is the natural magnet?

i. Compass ii. Bar magnet

iii. U-shaped magnet iv. Lodestone

Times' Crucial Science and Environment 97 Book 7

c. Which of the following is a temporary magnet?

i. Horse-shoe magnet ii. Bar magnet

iii. Electromagnet iv. U-shaped magnet

d. What is used to protect the magnetic strength?

i. Hammer ii. Metal case

iii. Plastic cover iv. Magnetic keeper

e. How is the strength of the electromagnet increased?

i. Increasing the number of turns in the coil

ii. Using soft iron piece for making the electromagnet

iii. Passing more electricity through the coil

iv. All of the above
2. Answer these questions in very short.

a. What is loadstone?
b. What is demagnetization?
c. Why is a magnetic keeper used?
d. Write down the uses of magnets.

e. Write down the uses of electromagnet.
3. Give reasons:

a. We should not drop a magnet carelessly.
b. A copper nail cannot be turned into an electromagnet.
c. An electromagnet is a temporary magnet.
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e. A soft piece of iron is used to make an electromagnet.
4. Differentiate between:
a. Magnet and magnetic substance
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c. A permanent and a temporary magnet

5. Answer these questions:

a. What is a magnet? Write down its properties.

b. What is demagnetization? What are the methods of avoiding
demagnetization?

Times' Crucial Science and Environment 98 Book 7

c. What is magnetization? Explain the single touch method of
magnetization.

d. How is an electromagnet made? Explain.
e. What things should be remembered while making an

electromagnet?
f. How can you increase the strength of an electromagnet?
g. Write down the uses of magnets.
h. Name some instruments in which an electromagnet is used.
i. Explain the double touch method of magnetization.
6. Diagrammatic questions:
a. Write down the names of magnets shown:


Ō

b. Label the following diagram and answer the questions:


Ō

i) What is the coil of wire wound around the nail called?
ii) What happens if a naked wire is used to make coil?
iii) How can you increase the strength of the electromagnet?
iv) Where are such magnets used?

Project Work

Take some bar magnets and perform different experiments to
demonstrate the properties of a magnet, i.e. directional property,
strength of poles, attraction and repulsion of poles, etc.

Times' Crucial Science and Environment 99 Book 7

Chapter (OHFWULFLW\

10

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϰ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ĞĮŶĞ ƐƚĂƟĐ ĞůĞĐƚƌŝĐŝƚLJ͘
 dĞůů ƚŚĞ ĞīĞĐƚƐ ŽĨ ƐƚĂƟĐ ĞůĞĐƚƌŝĐŝƚLJ ͘
 Explain about current electricity.
 ĞĮŶĞ ĞůĞĐƚƌŝĐ ĐŝƌĐƵŝƚ͘
 Write the symbols used in electric circuit.
 džƉůĂŝŶ ĂďŽƵƚ ƐĞƌŝĞƐ ĐŽŵďŝŶĂƟŽŶ ŽĨ ĐĞůůƐ͘
MIND OPENERS
 Can television, computer, radio, etc work without electricity?
 What are the sources of electricity?
 How many types of electricity do you know?
 What is electric circuit? Discuss.

Introduction

Nowadays electricity is essential part of our daily life. We cannot imagine
our comfortable life without electricity. We need electricity to run television,
computer, iron, water pump, radio, etc. We need electricity to light electric
lamp at night.

Electricity is a form of energy which is produced from electrons. Electrons
are the negatively charged particles present in an atom. They are revolving
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i) Static electricity ii) Current electricity

Static Electricity

Every substance is made up of atoms. Atom contains electrons, protons
and neutrons. Electrons are revolving around the nucleus. In the nucleus,
there are protons and neutrons. Electrons are negatively charged particles
whereas protons are positively charged particles and neutrons are charge
less or neutral. The electrons can travel from one atom to another atom.

Times' Crucial Science and Environment 100 Book 7

When electrons travel from one substance to another, charge is developed in
the substance. The development of charge is the cause for static electricity.
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When a substance loses electrons, it becomes positively charged. When a
substance gains electrons, it becomes negatively charged.

Activity 10.1 To produce static electricity

Materials required:
A plastic ruler, small pieces of paper, etc.
Procedure
Take a plastic ruler. Rub it on your dry hair for a number of times.
After rubbing, bring the ruler near the small pieces of paper. What
do you observe?

Observation
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ruler.

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When the plastic ruler is rubbed on dry hair, electrons transfer from
hair to the ruler. Thus, there will be more number of electrons than
the number of protons in the plastic ruler. Thus, the ruler will be
negatively charged.
When the negatively charged ruler is brought near the paper pieces,
the positively charged particles of the paper will be attracted to the
ruler. Thus, the paper pieces will be attracted.

Conclusion: The plastic ruler gets negatively charged due to the
transfer of electrons from hair to the ruler. Here, static electricity is
developed in the ruler. The attraction of paper pieces to the ruler is
due to static electricity developed.
Static electricity is developed only in insulators. Plastic, glass, wood,
etc are insulators.

Times' Crucial Science and Environment 101 Book 7

Current Electricity

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Current electricity is called current in short. Current is used to run
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a conductor is required. Current electricity is produced by cell, generator
or dynamo. They are called sources of electricity.

Cell

Cell is a source of electricity which converts chemical energy to electrical
energy. Chemical reaction takes place inside the cell and electricity is
produced. Simple cell and dry cell are various types of cells.

Simple Cell &RSSHU %XOE
Simple cell consists of a container &RSSHU ZLUH
of glass or plastic. It contains water :DWHU ZLWK
with few drops of sulphuric acid. Two GLOXWH + 62 ²
plates- one copper plate and another =LQF
zinc plate are dipped into the water.
Copper plate works as positive (+ve) 6LPSOH FHOO
electrode and zinc plate works as
negative (-ve) electrode. Current
is produced inside this cell due to
chemical reaction. When the positive
terminal and negative terminal are
connected with a wire to a bulb, the
bulb glows.

Dry Cell
Dry cell is a commonly used cell. It does not contain any liquid. It contains
a container of zinc. A paste of ammonium chloride surrounds the inner
wall of the container. A mixture of carbon powder and manganese dioxide
is kept inside the container. In the middle, there is a carbon rod with metal
cap.

Inside the cell, chemical reaction occurs. As a result, electrical energy is
produced. Zinc acts as negative terminal and carbon rod acts as positive
terminal of the cell.

When positive terminal and negative terminal of the cell are connected
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Generator and Dynamo %LF\FOH ZKHHO
Generator and dynamo also produce '\QDPR FDS
electricity. They convert mechanical
energy into electrical energy. $[OH
Generally, dynamo is used in bicycle 0DJQHW
to produce small amount of current.
But, generators are used in factories &RLO RI ZLUH
to produce large amount of current.
Dynamo and generator both contain %LF\FOH G\QDPR
a coil and a magnet kept nearer
to each other. When magnet or
coil comes into motion, current is
produced in the coil.

Electric Circuit (OHFWULF FLUFXLW

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FXUUHQW ÁRZV. Electric circuit is made
by a source, conducting wire and a load.
Switch is connected to open or close the
circuit.
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or dynamo is also the source of electricity.
Copper wire is conducting wire. Bulb is
the device which uses electricity. It acts
as load. Switch cuts off the current when
the circuit is not in use.

Times' Crucial Science and Environment 103 Book 7

Activity 10.2 To make an electric circuit

Materials required:
A dry cell, copper wire, bulb, switch and
bulb holder
Procedure:

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bulb in the bulb holder.

b. Connect one copper wire from each side of the holder.
c. Join both wires to the switch then to the cell each at one end.
d. Switch the circuit on and then off. What do you observe?
Observation:
The bulb glows when the switch is on. It does not glow when the
switch is off.
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circuit and the load works. It is called closed circuit.
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WKURXJK LW.
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and the load does not work. It is called open circuit. In other words,
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GLVFRQQHFWLRQ.

Symbols Used in Electric Circuit

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circuit. For making it easier, we use various symbols for denoting them.
Some of the symbols used for various components are as follows.

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Times' Crucial Science and Environment 104 Book 7

Combination of cells

A single cell is unable to produce desired current or voltage. Two or more
cells are combined together to get more current or voltage. Combination of
cells is called battery. *URXSLQJ RI WZR RU PRUH FHOOV WRJHWKHU LQ D FLUFXLW LV
FDOOHG FRPELQDWLRQ RI FHOOV. The combination of cells is of two types.

i) Series combination ii) Parallel combination

Series combination
When positive terminal of one cell is connected to negative terminal of
another cell, such combination of cells is called series combination. In a
series combination of cells, the total voltage of the circuit increases on
increasing the number of cells. Hence, the brightness of the bulb increases
on increasing the number of cells in the battery.

___ ___ ___
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Activity 10.3 Voltageandcurrentincreasesinseriescombination

Materials required
Two cells, a torch bulb, bulb holder, connecting wire, etc.
Procedure
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b. Connect the bulb to a cell with a connecting wire. Observe the
brightness of the bulb.

c. Then put two cells instead of one cell.
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___ ___

² ² ² ²

Times' Crucial Science and Environment 105 Book 7

Observation
When two cells are used, the brightness of the bulb increases than
in a single cell.

Advantages of series combination

1. When cells are connected in series combination, the voltage of
the combination increases. If a cell has voltage of 1.5V, two cells
connected in series combination will have voltage of 3V.

2. The current increases when the cells are connected in series
combination.

Parallel combination

When positive terminals of all cells are connected to one point and negative
terminals of all cells are connected to another point, the combination of
cells is called parallel combination of cells.

___

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²
²

___

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²

___

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__ _

__ _

In this combination, the brightness of the bulb does not increase with the
number of cells. The voltage of the combination does not increase with the
increase in the number of cells. But, current increases and the cells work
for longer time.

Water pump ͗ Ă ŵĞĐŚĂŶŝĐĂů ĚĞǀŝĐĞ ǁŚŝĐŚ ŝƐ ƵƐĞĚ ƚŽ ůŝŌ ǁĂƚĞƌ
ŵŵĞƚĞƌ : a device which is used to measure current
Voltmeter : a device which is used to measure voltage
Voltage : the force which pushes current

Main Points to Remember

1. Electricity is a form of energy which is produced from electrons.
2. Static electricity is the electricity which is produced due to change

in the number of electrons in a body.
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of electrons through a conductor.
4. Cell, dynamo, generator, etc are the sources of electricity.

Times' Crucial Science and Environment 106 Book 7

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disconnection.
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8. Series combination is the combination of cells in which positive terminal

of one cell is connected to the negative terminal of another cell.
9. Parallel combination of the cell is the connection of cells in which

negative terminal of all cells are connected to one point and positive
terminal of all cells are connected to another point.

Exercise

1. Choose the best alternative in each case.

a. The form of electricity which is produced due to the rubbing of two
insulators with each other is called

i. Static electricity ii. Current electricity

iii. Positive charge iv. Negative charge

b. Which of the following is the effect of static electricity?

i. Lighting a bulb ii. Ringing of electric bell

iii. Lightning and thunder iv. Operating of television

c. What electrolyte is used in a simple cell?

i. Carbon powder ii. Sulphuric acid

iii. Manganese dioxide iv. All

d. Which of the following is a load in an electric circuit?

i. Bulb ii. Heater

iii. Television iv. All of these

e. If a cell is added in a series combination of cells,

i. The brightness of the bulb increases.

ii. The brightness of the bulb decreases.

iii.The brightness of the bulb remains unaffected.

iv. The total voltage of the circuit decreases.

2. Copy the correct statement and correct the false statements if any.
a Current electricity is the electricity which is produced due to
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Times' Crucial Science and Environment 107 Book 7

c. Series combination of cells increases voltage.
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will be negatively charged.
e. Electrons are positively charged particles revolving around the

nucleus.

3. Answer these questions in short.
a. What is electricity?
b. What is static electricity? How is it produced?
c. What is current electricity? Mention some sources of current electricity.
d. What is an electric circuit? Draw an electric circuit which
contains a cell, a bulb, conduction wire and a switch.
e. What is open circuit?
f. What is series combination of cells? Why is this combination done?
g. What is closed circuit?

4. Draw symbols for:
a. Two cells b. Switch c. Bulb d. Ammeter e. Voltmeter

5. Differentiate between:
i. Series and parallel combination of cells
ii. Static electricity and current electricity

6. Answer these questions:
a. How does a plastic comb become charged? Explain.
b. Describe the structure of dry cell with a labelled diagram.
c. Explain the advantages of series combination of the cells.

7. Diagrammatic questions:
i. An electric circuit which contains a bulb, a switch and two cells
combined in parallel combination.
ii. An electric circuit which contains a bulb, a switch and three
cells combined in series combination.

Project Work

1. Collect about 7/8 used dry cells, bulbs of torch lights, connecting
wires, pins, cardboard paper, etc. Fix the cells in order in the
cardboard paper with the help of pins and construct different
combinations of cells. Then observe the brightness of the bulb in
different cases.

2. Take a dry cell and observe its internal parts.

Times' Crucial Science and Environment 108 Book 7

Chapter 0DWWHU

11

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϭϭ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ĞdžƉůĂŝŶ ŐĞŶĞƌĂů ƐƚĂƚĞƐ ŽĨ ŵĂƩĞƌ ĂŶĚ ƚŚĞŝƌ ƉƌŽƉĞƌƟĞƐ͘
 ƚĞůů ƚŚĞ ŶĂŵĞƐ ĂŶĚ ƐLJŵďŽůƐ ŽĨ ƐŽŵĞ ĐŽŵŵŽŶ ĞůĞŵĞŶƚƐ͘
 ĚĞĮŶĞ ĐŽŵƉŽƵŶĚƐ͕ ĂƚŽŵƐ ĂŶĚ ŵŽůĞĐƵůĞƐ͘
 ĚĞĮŶĞ ŵŽůĞĐƵůĂƌ ĨŽƌŵƵůĂ ĂŶĚ ǁƌŝƚĞ ƚŚĞ ŵŽůĞĐƵůĂƌ ĨŽƌŵƵůĂ ŽĨ ƐŽŵĞ

ĐŽŵŵŽŶ ĐŽŵƉŽƵŶĚƐ͘
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MIND OPENERS
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ŝƐĐƵƐƐ͘

Introduction

All the things that we can see or feel are matters. The matter may be
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KDV GHÀQLWH FRPSRVLWLRQ DQG SURSHUWLHV There are 118 elements discovered
VR IDU $PRQJ WKHP HOHPHQWV RFFXU LQ QDWXUH DQG DUH NQRZQ DV QDWXUDO
HOHPHQWV ZKLOH UHPDLQLQJ HOHPHQWV DUH V\QWKHVL]HG DUWLÀFLDOO\ LQ ODE
DQG DUH NQRZQ DV DUWLÀFLDO HOHPHQWV +\GURJHQ R[\JHQ QLWURJHQ LURQ
VLOYHU JROG FRSSHU HWF DUH VRPH H[DPSOHV RI HOHPHQWV
%XW VFLHQWLVWV KDYH FODLPHG WKDW WKH QXPEHU RI HOHPHQWV GLVFRYHUHG VR IDU
LV PRUH WKDQ LQFOXGLQJ QDWXUDO HOHPHQWV 0RVW RI WKH HOHPHQWV DUH
IRXQG LQ FRPELQDWLRQ ZLWK RWKHU HOHPHQWV LQ QDWXUH EXW VRPH HOHPHQWV
VXFK DV FDUERQ R[\JHQ QLWURJHQ KHOLXP VLOYHU JROG HWF DUH IRXQG LQ IUHH
state also.

Symbol

7KH VKRUW DQG DEEUHYLDWHG IRUP IRU WKH IXOO QDPH RI DQ HOHPHQW LV NQRZQ
DV V\PERO. 7KH V\PEROV RI HOHPHQWV DUH PDLQO\ WDNHQ IURP WKHLU (QJOLVK
QDPHV EXW VRPH HOHPHQWV KDYH V\PEROV IURP WKHLU /DWLQ QDPHV $ 6ZHGLVK
chemist, %HU]HOLXV LQWURGXFHG WKH V\VWHP RI V\PERO LQ 6\PEROV RI
elements may consist of one, two or three letters.
,I WKH V\PERO RI DQ HOHPHQW KDV D VLQJOH OHWWHU LW LV ZULWWHQ LQ FDSLWDO OHWWHU

Times' Crucial Science and Environment 111 Book 7

%XW LI WKH V\PERO RI DQ HOHPHQW KDV WZR OHWWHUV WKH ÀUVW OHWWHU LV ZULWWHQ
LQ FDSLWDO IRUP DQG WKH VHFRQG OHWWHU LV ZULWWHQ VPDOO 6LPLODUO\ LI WKHUH
DUH WKUHH OHWWHUV LQ D V\PERO RQO\ ÀUVW OHWWHU LV ZULWWHQ FDSLWDO DQG WKH
remainings are small.
6\PEROV RI HOHPHQWV IURP ÀUVW OHWWHU RI WKHLU QDPH

Name of Element Symbol Name of Element Symbol

,LJĚƌŽŐĞŶ H ^ƵůƉŚƵƌ S

ŽƌŽŶ B WŚŽƐƉŚŽƌƵƐ P

ĂƌďŽŶ C sĂŶĂĚŝƵŵ V

EŝƚƌŽŐĞŶ N zƩĞƌŝƵŵ Y

KdžLJŐĞŶ O /ŽĚŝŶĞ I

&ůƵŽƌŝŶĞ F hƌĂŶŝƵŵ U

6\PEROV RI HOHPHQWV IURP WZR OHWWHUV RI WKHLU QDPHV

Name of Element Symbol Name of Element Symbol

,ĞůŝƵŵ ,Ğ ƌŐŽŶ ƌ

>ŝƚŚŝƵŵ >ŝ ĂůĐŝƵŵ Ă

ĞƌLJůůŝƵŵ Ğ ŽďĂůƚ Ž

EĞŽŶ EĞ EŝĐŬĞů Eŝ

DĂŐŶĞƐŝƵŵ DŐ ĂƌŝƵŵ Ă

ůƵŵŝŶŝƵŵ ů ƌŽŵŝŶĞ ƌ

^ŝůŝĐŽŶ ^ŝ ŝŶĐ Ŷ

ŚůŽƌŝŶĞ ů ƌƐĞŶŝĐ As

6\PEROV RI HOHPHQWV IURP WKUHH OHWWHUV RI WKHLU QDPHV

Name of Element Symbol
hŶŶŝůƋƵĂĚƌŝƵŵ hŶƋ
hŶŶŝůƉĞŶƟƵŵ hŶƉ
hŶŶŝůŽĐƟƵŵ hŶŽ

6\PEROV RI HOHPHQWV IURP WKHLU /DWLQ QDPHV

English Name of Element >ĂƟŶ EĂŵĞ Symbol
^ŽĚŝƵŵ EĂƚƌŝƵŵ EĂ
<ĂůŝƵŵ K
WŽƚĂƐƐŝƵŵ

Times' Crucial Science and Environment 112 Book 7

English Name of Element >ĂƟŶ EĂŵĞ Symbol
/ƌŽŶ &ĞƌƌƵŵ &Ğ
ƵƉƌƵŵ Ƶ
ŽƉƉĞƌ Ő
^ŝůǀĞƌ ƌŐĞŶƚƵŵ ,Ő
DĞƌĐƵƌLJ ,LJĚƌĂƌŐLJƌƵŵ Ƶ
'ŽůĚ Wď
>ĞĂĚ ƵƌƵŵ ^Ŷ
dŝŶ WůƵŵďƵŵ ^ď
ŶƟŵŽŶLJ ^ƚĂŶŶƵŵ t
dƵŶŐƐƚĞŶ ^ƟďŶƵŵͬ^ƟďŝƵŵ
tŽůĨƌĂŵ;'ĞƌŵĂŶ ŶĂŵĞͿ

6\PEROV RI HOHPHQWV IURP WKH QDPHV RI VFLHQWLVWV

Name of Element EĂŵĞ ŽĨ ƐĐŝĞŶƟƐƚ Symbol

ƵƌŝƵŵ DĂĚĂŵ ƵƌŝĞ ŵ

ŝŶƐƚĞŝŶŝƵŵ ůďĞƌƚ ŝŶƐƚĞŝŶ Es

EŽďĞůŝƵŵ ůĨƌĞĚ EŽďĞů EŽ

&ĞƌŵŝƵŵ ŶƌŝĐŽ &Ğƌŵŝ &ŵ

Atom

$Q DWRP LV WKH VPDOOHVW SDUWLFOH RI DQ HOHPHQW WKDW FDQ WDNH SDUW LQ D
FKHPLFDO UHDFWLRQ $Q DWRP PD\ RU PD\ QRW H[LVW IUHHO\ LQ QDWXUH (DFK
HOHPHQW LV PDGH XS RI RQO\ RQH NLQG RI DWRPV $OO WKH DWRPV RI WKH VDPH
HOHPHQW KDYH H[DFWO\ VLPLODU IHDWXUHV ,Q VRPH HOHPHQWV DWRPV FRPELQH
WR IRUP PROHFXOHV

$Q DWRP LV DQ H[WUHPHO\ VPDOO VSKHULFDO SDUWLFOH ,W FRQWDLQV VRPH PLFURVFRSLF
SDUWLFOHV LQVLGH LW 7KHVH PLFURVFRSLF SDUWLFOHV DUH FDOOHG VXE DWRPLF SDUWLFOHV.
(OHFWURQ SURWRQ DQG QHXWURQ DUH WKH VXE DWRPLF SDUWLFOHV

GNGEVTQP

RTQVQPU PWENGWU
PGWVTQPU

UJGNN

Structure of an atom

Times' Crucial Science and Environment 113 Book 7

7KH SURWRQV DQG QHXWURQV DUH VLWXDWHG DW WKH FHQWUH RI WKH DWRP FDOOHG
QXFOHXV. 7KH HOHFWURQV UHYROYH DURXQG WKH QXFOHXV LQ GHÀQLWH FLUFXODU SDWKV
known as RUELWV. The orbits are also known as shells. An atom consists of
HTXDO QXPEHU RI HOHFWURQV DQG SURWRQV
D (OHFWURQ
$Q HOHFWURQ LV WKH QHJDWLYHO\ FKDUJHG VXE DWRPLF SDUWLFOH ZKLFK UHYROYHV
DURXQG WKH QXFOHXV 7KH SDWK DORQJ ZKLFK WKH HOHFWURQ UHYROYHV DURXQG WKH
QXFOHXV LV NQRZQ DV RUELW RU VKHOO $Q HOHFWURQ LV GHQRWHG E\ H
$Q HOHFWURQ KDV H[WUHPHO\ VPDOO PDVV ,WV PDVV LV HTXDO WR th the
mass of a K\GURJHQ DWRP.
b. Proton
$ SURWRQ LV D SRVLWLYHO\ FKDUJHG VXE DWRPLF SDUWLFOH ZKLFK LV ORFDWHG DW
WKH QXFOHXV RI DQ DWRP $ SURWRQ LV GHQRWHG E\ S 7KH PDVV RI D SURWRQ LV
HTXDO WR WKH PDVV RI DQ DWRP RI K\GURJHQ
F 1HXWURQ
$ QHXWURQ LV D QHXWUDO VXE DWRPLF SDUWLFOH ZKLFK LV ORFDWHG DW WKH QXFOHXV RI
DQ DWRP. $ QHXWURQ LV GHQRWHG E\ Q 7KH PDVV RI D QHXWURQ LV QHDUO\ HTXDO
WR WKH PDVV RI D SURWRQ +HQFH PDVV RI D QHXWURQ LV QHDUO\ HTXDO WR WKH
mass of an atom of hydrogen.

$Q DWRP FRQVLVWV RI SRVLWLYHO\ FKDUJHG SURWRQV DQG QHJDWLYHO\ FKDUJHG
HOHFWURQV %XW WKH DWRP LV HOHFWULFDOO\ QHXWUDO ,W LV EHFDXVH WKH QXPEHU RI
SURWRQV DQG HOHFWURQV LV HTXDO LQ DQ DWRP DQG KHQFH WKH\ QHXWUDOL]H WKH
charge of each other.

Atomic number (Z)

7KH QXPEHU RI SURWRQV SUHVHQW LQ WKH QXFOHXV RI DQ DWRP LV FDOOHG DWRPLF
QXPEHU ,W LV GHQRWHG E\ ]

,Q DQ HOHFWULFDOO\ QHXWUDO DWRP WKH QXPEHU RI SURWRQV LV HTXDO WR WKH
QXPEHU RI HOHFWURQV +HQFH DWRPLF QXPEHU PD\ DOVR EH GHÀQHG DV WKH
QXPEHU RI HOHFWURQV LQ DQ HOHFWULFDOO\ QHXWUDO DWRP

7KXV

$WRPLF QXPEHU 1XPEHU RI SURWRQV 1XPEHU RI HOHFWURQV
? = S H-

)RU H[DPSOH DWRPLF QXPEHU RI FDUERQ LV ,W PHDQV WKDW FDUERQ KDV
SURWRQV LQ LWV QXFOHXV RU LW KDV HOHFWURQV LQ LWV VKHOOV

(DFK HOHPHQW KDV LWV RZQ DWRPLF QXPEHU 1R WZR GLIIHUHQW HOHPHQWV KDYH
WKH VDPH DWRPLF QXPEHU

Times' Crucial Science and Environment 114 Book 7

Atomic mass (A)

7KH VXP RI SURWRQV DQG QHXWURQV LQ WKH QXFOHXV RI DQ DWRP LV FDOOHG DWRPLF
PDVV ,W LV GHQRWHG E\ $ $WRPLF PDVV LV DOVR NQRZQ DV DWRPLF ZHLJKW
$WRPLF PDVV 1R RI SURWRQV 1R RI QHXWURQV

? $ S Q0
6LQFH WKH PDVV RI DQ HOHFWURQ LV H[WUHPHO\ VPDOO LW LV QHJOHFWHG ZKLOH
FDOFXODWLQJ DWRPLF PDVV
7KH DWRPLF QXPEHU DWRPLF PDVV V\PERO DQG QXPEHU RI VXE DWRPLF
SDUWLFOHV DUH JLYHQ LQ WKH IROORZLQJ WDEOH

Atomic Element Symbol No. of No. of No. of Atomic
No. electrons protons neutrons mass
,LJĚƌŽŐĞŶ H
ϭ ,ĞůŝƵŵ ,Ğ ϭϭ 0 ϭ
2 >ŝƚŚŝƵŵ >ŝ 22 2 4
3 ĞƌLJůůŝƵŵ Ğ 33 4 7
4 ŽƌŽŶ B 44 5 9
5 ĂƌďŽŶ C 55 6 ϭϭ
6 EŝƚƌŽŐĞŶ N 66 6 ϭϮ
7 KdžLJŐĞŶ O 77 7 ϭϰ
8 &ůƵŽƌŝŶĞ F 88 8 ϭϲ
9 EĞŽŶ EĞ 99 ϭϬ ϭϵ
ϭϬ ^ŽĚŝƵŵ EĂ ϭϬ ϭϬ ϭϬ 20
ϭϭ DŐ ϭϭ ϭϭ ϭϮ 23
ϭϮ DĂŐŶĞƐŝƵŵ ů ϭϮ ϭϮ ϭϮ 24
ϭϯ ůƵŵŝŶŝƵŵ ^ŝ ϭϯ ϭϯ ϭϰ 27
ϭϰ P ϭϰ ϭϰ ϭϰ 28
ϭϱ ^ŝůŝĐŽŶ S ϭϱ ϭϱ ϭϲ ϯϭ
ϭϲ WŚŽƐƉŚŽƌƵƐ ů ϭϲ ϭϲ ϭϲ 32
ϭϳ ƌ ϭϳ ϭϳ ϭϴ 35
ϭϴ ^ƵůƉŚƵƌ K ϭϴ ϭϴ 22 40
ϭϵ ŚůŽƌŝŶĞ Ă ϭϵ ϭϵ 20 39
20 ƌŐŽŶ 20 20 20 40
WŽƚĂƐƐŝƵŵ
ĂůĐŝƵŵ

Times' Crucial Science and Environment 115 Book 7

Distribution of electrons in an atom

$V VWXGLHG HDUOLHU WKH SURWRQV DQG QHXWURQV DUH ORFDWHG DW WKH QXFOHXV RI
DQ DWRP 7KH HOHFWURQV UHYROYH DURXQG WKH QXFOHXV LQ RUELWV RU VKHOOV %XW
all the electrons do not lie in the same shell. There are different shells
DURXQG WKH QXFOHXV LQ ZKLFK HOHFWURQV UHYROYH (DFK VKHOO FRQVLVWV RI D
SDUWLFXODU QXPEHU RI HOHFWURQV 7KH GLVWULEXWLRQ RI HOHFWURQV LQ GLIIHUHQW
VKHOOV DURXQG WKH QXFOHXV LV NQRZQ DV HOHFWURQLF FRQÀJXUDWLRQ.

7KH GLIIHUHQW VKHOOV RI DQ DWRP FDQ EH VKRZQ DV

R ./0
P

-

P

P

P

P

(KI &KHHGTGPV UJGNNU QH CP CVQO

7KH GLVWULEXWLRQ RI HOHFWURQV LQ GLIIHUHQW VKHOOV LV JLYHQ E\ WKH IROORZLQJ UXOHV

7KH PD[LPXP QXPEHU RI HOHFWURQV WKDW FDQ EH SODFHG LQ HDFK VKHOO LV
given by 2n2 UXOH ZKHUH Q LV WKH QXPEHU RI VKHOOV RU RUELWV )RU H[DPSOH

)RU WKH N VKHOO Q

+HQFH WKH QXPEHU RI HOHFWURQV ZLOO EH Q2

ð 2



)RU WKH / VKHOO Q

+HQFH WKH QXPEHU RI HOHFWURQV Q2

ð 2



Times' Crucial Science and Environment 116 Book 7

6LPLODUO\ IRU 0 VKHOO Q

+HQFH WKH QXPEHU RI HOHFWURQV Q2

[ 2

DQG VR RQ

7KH RXWHUPRVW RUELW RI DQ DWRP FDQQRW KDYH PRUH WKDQ HOHFWURQV DQG
WKH RUELW QH[W WR LW FDQQRW KDYH PRUH WKDQ HOHFWURQV ,W LV NQRZQ DV
%RKU %XU\ UXOH.

7KH HOHFWURQLF FRQÀJXUDWLRQ RI HOHPHQWV RI DWRPLF QXPEHU ³ LV JLYHQ EHORZ

1. Hydrogen

Symbol: H R
Atomic No.: 1
1
No. of p+: 0
No. of n0: 1
No. of e—: 1
Atomic mass:

(OHFWURQLF &RQ¿JXUDWLRQ *[FTQIGP

Shell: K
No. of electrons: 1

2. Helium

Symbol: He R
Atomic No.: 2 P
*GNKWO
No. of p+: 2
No. of n0: 2 Book 7
No. of e—: 2
Atomic mass: 4

(OHFWURQLF &RQ¿JXUDWLRQ

Shell: K
No. of electrons: 2

Times' Crucial Science and Environment 117

3. Lithium

Symbol: Li R
Atomic No.: 3 P

No. of p+: 3 .KVJKWO
No. of n0: 4
No. of e—: 3
Atomic mass: 7

(OHFWURQLF &RQ¿JXUDWLRQ L
1
Shell: K
No. of electrons: 2

4. Beryllium

Symbol: Be R
Atomic No.: 4 P

No. of p+: 4
No. of n0: 5
No. of e—: 4
Atomic mass: 9

(OHFWURQLF &RQ¿JXUDWLRQ $GT[NNKWO

Shell: K L
No. of electrons: 2 2

6LPLODUO\ WKH HOHFWURQLF FRQÀJXUDWLRQ RI VRPH RWKHU HOHPHQWV LV

R R R R
P P P P

$QTQP %CTDQP 0KVTQIGP 1Z[IGP
118 Book 7
Times' Crucial Science and Environment

R R R R
P P P P

(NWQTKPG 0GQP 5QFKWO /CIPGUKWO

R R R
P P P

#NWOKPKWO 5KNKEQP 2JQURJQTWU

R R R
P P P

5WNRJWT %JNQTKPG #TIQP

R R
P P

2QVCUUKWO %CNEKWO

Times' Crucial Science and Environment 119 Book 7

Compound

$ FRPSRXQG LV D SXUH VXEVWDQFH ZKLFK LV IRUPHG E\ WKH FKHPLFDO FRPELQDWLRQ
RI WZR RU PRUH HOHPHQWV LQ GHÀQLWH SURSRUWLRQ E\ ZHLJKW )RU H[DPSOH
ZDWHU FDUERQ GLR[LGH FRPPRQ VDOW DPPRQLD VXJDU HWF DUH FRPSRXQGV
7KH SURSHUWLHV RI FRPSRXQGV DUH WRWDOO\ GLIIHUHQW IURP WKRVH RI WKH HOHPHQWV
IURP ZKLFK WKH\ DUH PDGH 7KH QXPEHU RI FRPSRXQGV LV YHU\ ODUJH LQ
FRPSDULVRQ WR WKH QXPEHU RI HOHPHQWV 7KHUH DUH PLOOLRQV RI FRPSRXQGV
GLVFRYHUHG VR IDU 7KH FRPSRXQGV DUH PDGH RI PROHFXOHV

'L൵HUHQFHV EHWZHHQ (OHPHQW DQG &RPSRXQG

Element Compound

ϭ͘ Ŷ ĞůĞŵĞŶƚ ŝƐ ĐŽŵƉŽƐĞĚ ŽĨ ŽŶůLJ ŽŶĞ ϭ͘ ĐŽŵƉŽƵŶĚ ŝƐ ĐŽŵƉŽƐĞĚ ŽĨ ƚǁŽ Žƌ

ƚLJƉĞ ŽĨ ĂƚŽŵƐ͘ ŵŽƌĞ ŬŝŶĚƐ ŽĨ ĂƚŽŵƐ͘

Ϯ͘ dŚĞ ƚŽƚĂů ŶƵŵďĞƌ ŽĨ ĞůĞŵĞŶƚƐ ŝƐ Ϯ͘ dŚĞ ŶƵŵďĞƌ ŽĨ ĐŽŵƉŽƵŶĚƐ ŝƐ ǀĞƌLJ

ƐŵĂůů͘ ůĂƌŐĞ͘

ϯ͘ dŚĞ ƐŵĂůůĞƐƚ ƉĂƌƟĐůĞ ŽĨ ĂŶ ĞůĞŵĞŶƚ ϯ͘ dŚĞ ƐŵĂůůĞƐƚ ƉĂƌƟĐůĞ ŽĨ Ă ĐŽŵƉŽƵŶĚ

ŝƐ ĂƚŽŵ Žƌ ŵŽůĞĐƵůĞ͘ ŝƐ ŵŽůĞĐƵůĞ͘

ϰ͘ džĂŵƉůĞƐ͗ ŚLJĚƌŽŐĞŶ͕ ŽdžLJŐĞŶ͕ ϰ͘ džĂŵƉůĞƐ͗ tĂƚĞƌ͕ ŽŵŵŽŶ ƐĂůƚ͕
ĐĂƌďŽŶ͕ ĞƚĐ͘ ĂŵŵŽŶŝĂ͕ ĞƚĐ͘

Molecule

$ PROHFXOH LV WKH VPDOOHVW SDUWLFOH RI D FRPSRXQG RU DQ HOHPHQW ZKLFK
KDV LQGHSHQGHQW H[LVWHQFH. 7KHUH LV GLIIHUHQFH EHWZHHQ WKH PROHFXOH RI DQ
HOHPHQW DQG WKDW RI D FRPSRXQG 7KH PROHFXOHV RI DQ HOHPHQW DUH PDGH XS
RI RQH RU PRUH DWRPV RI WKH VDPH NLQG ZKHUHDV WKH PROHFXOHV RI D FRPSRXQG
DUH PDGH XS RI WZR RU PRUH DWRPV RI GLIIHUHQW NLQG

Valence Electrons

$Q DWRP FRQVLVWV RI GLIIHUHQW VKHOOV 7KHVH VKHOOV KDYH D GHÀQLWH HOHFWURQ
KROGLQJ FDSDFLW\ 7KH RXWHUPRVW VKHOO RI DQ DWRP FDQQRW KROG PRUH WKDQ
electrons.

7KH RXWHUPRVW VKHOO RI DQ DWRP LV NQRZQ DV YDOHQFH VKHOO 7KH QXPEHU RI
HOHFWURQV SUHVHQW LQ WKH YDOHQFH VKHOO RI DQ DWRP DUH FDOOHG YDOHQFH HOHFWURQV

Valency

7KH FRPELQLQJ FDSDFLW\ RI DQ DWRP ZLWK DQRWKHU DWRP WR IRUP D PROHFXOH
LV FDOOHG YDOHQF\. 7KH YDOHQF\ RI DQ HOHPHQW LV UHSUHVHQWHG LQ QXPEHUV
VXFK DV ««« HWF 7KH YDOHQF\ RI DQ HOHPHQW LV GHWHUPLQHG
E\ WKH QXPEHU RI LWV YDOHQFH HOHFWURQV ,I WKH YDOHQFH VKHOO RI DQ DWRP LV
FRPSOHWHO\ ÀOOHG LW GRHV QRW KDYH FRPELQLQJ FDSDFLW\ +HQFH WKH YDOHQF\

Times' Crucial Science and Environment 120 Book 7

RI VXFK HOHPHQW LV ]HUR )RU H[DPSOH KHOLXP QHRQ DUJRQ HWF KDYH ]HUR
valency. These elements do not combine with other elements to form
FRPSRXQGV DQG KHQFH WKHVH DUH FDOOHG LQHUW JDVHV.
7KH YDOHQF\ RI DQ HOHPHQW RU UDGLFDO LV GHWHUPLQHG E\ WKH QXPEHU RI
hydrogen or chlorine atoms that can combine with an atom of that element.
)i s1R3DU aH L[nQDd FPsRoSPOoHPn R.YQD OVHDQOFW \ 1RID &R[O \ JLVH Q Y2D O HLQQ FZ\ DRWIH QU L W+UR2J2H Q L V 1 LYQD DOHPQFP\R RQIL DV R G1LX+P3

Valency of some common elements:

Atomic No. Name of Symbol Valency
ϭ Element H
ϭ
,LJĚƌŽŐĞŶ 0
ϭ
2 ,ĞůŝƵŵ ,Ğ 2
3
3 >ŝƚŚŝƵŵ >ŝ 4
3
4 ĞƌLJůůŝƵŵ Ğ 2
ϭ
5 ŽƌŽŶ B 0
ϭ
6 ĂƌďŽŶ C 2
3
7 EŝƚƌŽŐĞŶ N 4
8 KdžLJŐĞŶ O 3
2
9 &ůƵŽƌŝŶĞ F ϭ
0
ϭϬ EĞŽŶ EĞ ϭ
2
ϭϭ ^ŽĚŝƵŵ EĂ

ϭϮ DĂŐŶĞƐŝƵŵ DŐ

ϭϯ ůƵŵŝŶŝƵŵ ů

ϭϰ ^ŝůŝĐŽŶ ^ŝ

ϭϱ WŚŽƐƉŚŽƌƵƐ P

ϭϲ ^ƵůƉŚƵƌ S

ϭϳ ŚůŽƌŝŶĞ ů

ϭϴ ƌŐŽŶ ƌ

ϭϵ WŽƚĂƐƐŝƵŵ K

20 ĂůĐŝƵŵ Ă

Times' Crucial Science and Environment 121 Book 7

$PRQJ WKH DERYH HOHPHQWV VXOSKXU KDV WKH YDOHQF\ DQG DOVR 6LPLODUO\
nitrogen sometimes has 5 valency.

Valency of some other elements

S. No. Name of Element Symbol Valency
2
ϭ ŝŶĐ Ŷ 2
ϭ
2 ĂƌŝƵŵ Ă ϭ
ϭ
3 ƌŽŵŝŶĞ ƌ
4 /ŽĚŝŶĞ I

5 ^ŝůǀĞƌ Ő

Variable valency

Some elements have valency of more than one kind. This is known as YDULDEOH
YDOHQF\. 7KH YDULDEOH YDOHQF\ RI VRPH FRPPRQ HOHPHQWV LV JLYHQ EHORZ

S. No. Name of Element Symbol Valency
ϭ /ƌŽŶ Fe Ϯ͕ ϯ

2 ŽƉƉĞƌ Ƶ ϭ͕ Ϯ

3 DĞƌĐƵƌLJ ,Ő ϭ͕ Ϯ

4 'ŽůĚ Ƶ ϭ͕ ϯ

5 >ĞĂĚ Wď Ϯ͕ ϰ

6 dŝŶ ^Ŷ Ϯ͕ ϰ

Radical

$Q DWRP RU JURXS RI DWRPV FDUU\LQJ QHJDWLYH RU SRVLWLYH FKDUJH ZKLFK
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7KH\ DUH

6LPSOH UDGLFDOV 7KHVH UDGLFDOV DUH FRPSRVHG RI VLQJOH DWRP )RU
H[DPSOH + &O– 1D , O– – &U , etc.

&RPSRXQG UDGLFDOV 7KHVH UDGLFDOV DUH FRPSRVHG RI WZR RU PRUH
DWRPV )RU H[DPSOH 624– – &23– – 1+4 2+– 123– , etc.

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7KH\ DUH

Times' Crucial Science and Environment 122 Book 7

(OHFWURSRVLWLYH UDGLFDOV 7KHVH UDGLFDOV FDUU\ SRVLWLYH FKDUJH ( J
+ 1D 0J &D , Al )H )H , Ag 1+4 , etc.

(OHFWURQHJDWLYH UDGLFDOV 7KHVH UDGLFDOV FDUU\ QHJDWLYH FKDUJH
( J 2+– &O– , O– – SO4– – &23– – etc.

Valency of Radicals

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9DOHQF\ RI VRPH FRPPRQ UDGLFDOV LV JLYHQ EHORZ

S. No. Name of Radicals Symbol Valency

ϭ ŚůŽƌŝĚĞ ů ϭ

2 KdžŝĚĞ O2

3 ^ŽĚŝƵŵ EĂ ϭ

4 DĂŐŶĞƐŝƵŵ DŐ 2

5 ^ƵůƉŚĂƚĞ SO4 2
6 ^ƵůƉŚŝƚĞ SO3 2
7 ^ƵůƉŚŝĚĞ
S2

8 ŝƐƵůƉŚĂƚĞ HSO4 ϭ
9 EŝƚƌĂƚĞ NO3 ϭ
ϭϬ EŝƚƌŝƚĞ NO2 ϭ
ϭϭ EŝƚƌŝĚĞ 3
N

ϭϮ ĂƌďŽŶĂƚĞ CO3 2
ϭϯ ŝĐĂƌďŽŶĂƚĞ HCO3 ϭ
ϭϰ ,LJĚƌŽdžŝĚĞ OH ϭ

ϭϱ ŵŵŽŶŝƵŵ NH4 ϭ
ϭϲ ƵƉƌŽƵƐ Ƶ ϭ

ϭϳ ƵƉƌŝĐ Ƶ 2

ϭϴ &ĞƌƌŽƵƐ &Ğ 2

ϭϵ &ĞƌƌŝĐ &Ğ 3

20 ŝŶĐ Ŷ 2

1RWH The charges of radicals are not shown for the ease in reading and
PHPRUL]LQJ

Times' Crucial Science and Environment 123 Book 7

Molecular Formula

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ZKLFK VKRZV WKH DFWXDO QXPEHU RI DWRPV SUHVHQW LQ LW LV FDOOHG PROHFXODU
IRUPXOD )RU H[DPSOH PROHFXODU IRUPXOD RI ZDWHU LV +22 PROHFXODU
IRUPXOD RI R[\JHQ LV 22 PROHFXODU IRUPXOD RI K\GURJHQ LV +2, etc.
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LQ D PROHFXOH

+RZ WR ZULWH PROHFXODU IRUPXOD"

:ULWLQJ WKH PROHFXODU IRUPXOD RI HOHPHQWV LV HDV\ EHFDXVH WKHUH DUH VLPLODU
NLQGV RI DWRPV LQ DQ HOHPHQW %XW ZH VKRXOG EH FDUHIXO ZKLOH ZULWLQJ
PROHFXODU IRUPXOD RI FRPSRXQGV
)ROORZLQJ VWHSV VKRXOG EH IROORZHG ZKLOH ZULWLQJ WKH PROHFXODU IRUPXOD RI
FRPSRXQGV
Step 1: :ULte down the symbols of the combining atoms or radicals

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1 +
Step 2: :ULWH GRZQ WKH YDOHQF\ RI HDFK DWRP RU UDGLFDO RQ LWV WRS

31

1 +
Step 3: 5HZULWH WKH V\PEROV DQG H[FKDQJH WKHLU YDOHQFLHV



1+

1+3 ,W LV WKH PROHFXODU IRUPXOD RI DPPRQLD

,I RQH RI WKH YDOHQFLHV LV PXOWLSOH RI DQRWKHU WKH FRPPRQ YDOHQF\ LV
UHPRYHG H J FDUERQ GLR[LGH



&2

&2

7KH FRPSRXQG UDGLFDOV DUH HQFORVHG E\ EUDFNHWV LI QHFHVVDU\ H J

DPPRQLXP VXOSKDWH



1+ 62

11++4 26S2O 4

Times' Crucial Science and Environment 124 Book 7

6RPH PRUH H[DPSOHV DUH JLYHQ EHORZ

:DWHU +\GURJHQ 2[\JHQ 0HWKDQH &DUERQ +\GURJHQ

+2
&+

+ 2 &+

/LPHVWRQH RU 0DUEOH &DOFLXP FDUERQDWH



&D &2

&D&2
+\GURFKORULF DFLG +\GURJHQ &KORULQH



+ &O

+&O

Molecular formula of some common compounds

S. No. Name of the Compound Molecular Formula
ϭ tĂƚĞƌ
2 ĂƌďŽŶ ĚŝŽdžŝĚĞ H2O
3 ^ƵůƉŚƵƌŝĐ ĂĐŝĚ CO2
4 EŝƚƌŝĐ ĂĐŝĚ H2SO4
5 ŽŵŵŽŶ ƐĂůƚ ;ĞĚŝďůĞ ƐĂůƚͿ HNO3
6 YƵŝĐŬ >ŝŵĞ ; ĂůĐŝƵŵ ŽdžŝĚĞͿ EĂ ů
7 ĂůĐŝƵŵ ĐŚůŽƌŝĚĞ
8 ĂůĐŝƵŵ ĐĂƌďŽŶĂƚĞ ĂK
9 ^ůĂŬĞĚ >ŝŵĞ ;>ŝŵĞ ǁĂƚĞƌͿ
ϭϬ >ĂƵŐŚŝŶŐ ŐĂƐ ;EŝƚƌŽƵƐ ŽdžŝĚĞͿ Ă ů2
ϭϭ ĂƵƐƟĐ ƐŽĚĂ Ă K3
ϭϮ ĂƵƐƟĐ ƉŽƚĂƐŚ Ă;K,Ϳ2
ϭϯ ^ƵůƉŚƵƌ ĚŝŽdžŝĚĞ N2O
ϭϰ ŵŵŽŶŝĂ EĂK,
ϭϱ DĞƚŚĂŶĞ
KOH

SO2
NH3
CH4

Times' Crucial Science and Environment 125 Book 7

Physical and Chemical Change

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:H REVHUYH VHYHUDO FKDQJHV LQ RXU GDLO\ OLIH )RU H[DPSOH ERLOLQJ ZDWHU
PHOWLQJ LFH RU LFH FUHDP EXUQLQJ FDQGOH JHUPLQDWLQJ VHHGV KDWFKLQJ HJJV
HWF $OO WKH FKDQJHV DURXQG XV FDQ EH FDWHJRUL]HG LQWR WZR W\SHV- SK\VLFDO
FKDQJH and FKHPLFDO FKDQJH.
3K\VLFDO &KDQJH
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7KH SK\VLFDO FKDQJH LV D WHPSRUDU\ FKDQJH

,FH :DWHU

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PDWWHU 7KH RWKHU H[DPSOHV RI SK\VLFDO FKDQJH DUH DV IROORZV

D &KDQJH RI ZDWHU LQWR ZDWHU YDSRXU
b. Dissolving salt in water
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SHUPDQHQW FKDQJH DQG JHQHUDOO\ LW FDQQRW EH UHYHUVHG
7KXV D FKHPLFDO FKDQJH LV D SHUPDQHQW FKDQJH LQ ZKLFK D QHZ VXEVWDQFH
ZLWK HQWLUHO\ QHZ SURSHUWLHV LV IRUPHG

Times' Crucial Science and Environment 126 Book 7

Examples:
D )RUPDWLRQ RI \RJKXUW IURP PLON
E %XUQLQJ RI FRDO
F 5XVWLQJ RI LURQ
G *URZWK RI D EDE\ LQWR \RXQJ
H %DNLQJ RI EUHDG IURP ÁRXU HWF

$OO WKH FKHPLFDO UHDFWLRQV DUH WKH H[DPSOHV RI FKHPLFDO FKDQJHV
'LIIHUHQFHV EHWZHHQ SK\VLFDO FKDQJH DQG FKHPLFDO FKDQJH

6 1R 3K\VLFDO &KDQJH &KHPLFDO &KDQJH

1. Physical change is a change in which &KHPLFDO FKDQJH LV D FKDQJH LQ
QR QHZ VXEVWDQFH LV IRUPHG ZKLFK D QHZ VXEVWDQFH LV IRUPHG

2. ,W LV D WHPSRUDU\ FKDQJH ,W LV D SHUPDQHQW FKDQJH

3. 0HOWLQJ RI LFH PDJQHWL]DWLRQ RI PDJQHW 5XVWLQJ RI LURQ EXUQLQJ RI SDSHU
HWF DUH H[DPSOHV RI WKLV FKDQJH HWF DUH H[DPSOHV RI WKLV FKDQJH

/ŶƚĞƌŵŽůĞĐƵůĂƌ ƐƉĂĐĞ ͗ ƐƉĂĐĞ ďĞƚǁĞĞŶ ŵŽůĞĐƵůĞƐ
DĞƚŚĂŶĞ ŐĂƐ ͗ ĐŽůŽƵƌůĞƐƐ ŐĂƐ ǁŚŝĐŚ ŝƐ ƉƌŽĚƵĐĞĚ ĨƌŽŵ ĚĞĐĂLJŝŶŐ ŵĂƚĞƌŝĂůƐ
DŝĐƌŽƐĐŽƉŝĐ ͗ ǀĞƌLJ ƐŵĂůů
'ĞƌŵŝŶĂƟŽŶ ͗ ĚĞǀĞůŽƉŵĞŶƚ ŽĨ ƉůĂŶƚ ĨƌŽŵ ƐĞĞĚ

Main Points to Remember

$ VXEVWDQFH ZKLFK LV PDGH XS RI RQO\ RQH NLQG RI PROHFXOHV LV
FDOOHG SXUH VXEVWDQFH

$Q LPSXUH VXEVWDQFH FRQVLVWV RI WZR RU PRUH NLQGV RI PROHFXOHV

$Q HOHPHQW LV D SXUH VXEVWDQFH ZKLFK LV PDGH RI VDPH NLQG RI DWRPV

7KH SDUWLFOHV ZKLFK DUH SUHVHQW LQVLGH DQ DWRP DUH FDOOHG VXE DWRPLF
SDUWLFOHV (OHFWURQ SURWRQ DQG QHXWURQ DUH WKH VXE DWRPLF SDUWLFOHV

7KH QXPEHU RI SURWRQV SUHVHQW LQ WKH QXFOHXV RI DQ DWRP LV NQRZQ
DV DWRPLF QXPEHU

7KH WRWDO VXP RI SURWRQV DQG QHXWURQV SUHVHQW LQ WKH QXFOHXV RI DQ
atom is known as atomic mass.

7KH VPDOOHVW SDUWLFOH RI DQ HOHPHQW ZKLFK FDQ WDNH SDUW LQ D
chemical reaction is known as atom.

$ PROHFXOH LV WKH VPDOOHVW SDUWLFOH RI D FRPSRXQG RU DQ HOHPHQW
ZKLFK KDV LQGHSHQGHQW H[LVWHQFH

Times' Crucial Science and Environment 127 Book 7

7KH GLVWULEXWLRQ RI HOHFWURQV LQ GLIIHUHQW VKHOOV RI DQ DWRP LV NQRZQ
DV HOHFWURQLF FRQÀJXUDWLRQ

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as radical.

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ZKLFK EHKDYHV DV D VLQJOH XQLW LQ D FKHPLFDO UHDFWLRQ LV FDOOHG UDGLFDO

$ SK\VLFDO FKDQJH LV D WHPSRUDU\ FKDQJH LQ ZKLFK QR QHZ VXEVWDQFH
is formed.

$ FKHPLFDO FKDQJH LV D SHUPDQHQW FKDQJH LQ ZKLFK D QHZ VXEVWDQFH
ZLWK HQWLUHO\ QHZ SURSHUWLHV LV IRUPHG

Exercise

&KRRVH WKH EHVW DOWHUQDWLYH LQ HDFK FDVH

D 7KH VPDOOHVW SDUWLFOH RI DQ HOHPHQW WKDW WDNHV SDUW LQ D FKHPLFDO
reaction is

L $WRP LL 0ROHFXOH LLL 3URWRQ LY 1XFOHXV

E :KDW NLQG RI FKDQJH LV WKH WXUQLQJ RI PLON LQWR \RJXUW"

L &KHPLFDO FKDQJH LL 3K\VLFDO FKDQJH

iii. State change iv. Self change

F +RZ PDQ\ HOHPHQWV KDYH EHHQ GLVFRYHUHG VR IDU"

i. 105 ii. 109 iii.112 iv. 118

G $XUXP PHDQV LLL 6LOYHU LY 0HUFXU\
L &RSSHU LL *ROG

H :KDW LV WKH PROHFXODU IRUPXOD RI FRPPRQ VDOW"

L +22 LL 1+3 LLL &22 LY 1D&O

$QVZHU WKHVH TXHVWLRQV LQ YHU\ VKRUW

D :KDW LV PDWWHU"

E +RZ PDQ\ HOHPHQWV KDYH EHHQ GLVFRYHUHG VR IDU"

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G :ULWH GRZQ WKH DWRPLF QXPEHUV RI QLWURJHQ DQG VRGLXP

H :KDW GRHV WKH V\PERO ·0J· UHSUHVHQW"

I :KDW LV WKH DWRPLF PDVV RI R[\JHQ"

Times' Crucial Science and Environment 128 Book 7

J :KDW GR \RX PHDQ E\ + DQG +2"
K :KDW LV WKH GLIIHUHQFH EHWZHHQ &R DQG &2"
L :KDW LV D V\PERO"
M :ULWH down the symbols of nitrogen and neon.

'HÀQH

D $WRP E 6XE DWRPLF SDUWLFOHV F (OHFWURQ
I 0ROHFXOH
G 3URWRQ H 1HXWURQ L 9DOHQF\

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DQG

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/L 1D $O 1 3 6 $U

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D (OHPHQW DQG FRPSRXQG
E $WRP DQG PROHFXOH
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G &RPSRXQG DQG PL[WXUH
e. Physical change and chemical change

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D :KDW LV D OLTXLG" :ULWH GRZQ LWV SURSHUWLHV
E 'HÀQH FRPSRXQG ZLWK H[DPSOHV

Times' Crucial Science and Environment 129 Book 7

F :KDW LV D UDGLFDO" ([SODLQ LWV W\SHV
G ([SODLQ SK\VLFDO FKDQJH ZLWK H[DPSOHV
H :KDW LV D FKHPLFDO FKDQJH" :ULWH GRZQ DQ\ ÀYH H[DPSOHV RI

chemical change.
I :KDW LV D PL[WXUH" *LYH H[DPSOHV

:ULWH GRZQ WKH PROHFXODU IRUPXOD RI IROORZLQJ FRPSRXQGV E\

FULVV FURVV PHWKRG

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D 0J&O2 E $J123 F +2S
d. SO2 H 0J&23 I 1D+&23
K +2SO4
g. Al2(SO4 3

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S S S S
Q Q Q Q

S S S S
Q Q Q Q

Project Work

1. Take some water in a beaker and heat it. After sometime, the water
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Times' Crucial Science and Environment 130 Book 7

Chapter

12 0L[WXUH

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϱ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ĞdžƉůĂŝŶ ĂŶĚ ĚĞŵŽŶƐƚƌĂƚĞ ƚŚĞ ŵĞƚŚŽĚƐ ŽĨ ƐĞƉĂƌĂƟŶŐ ŚŽŵŽŐĞŶĞŽƵƐ

ŵŝdžƚƵƌĞ ďLJ ƉƌŽĐĞƐƐ ƐƵĐŚ ĂƐ ĞǀĂƉŽƌĂƟŽŶ͕ ĚŝƐƟůůĂƟŽŶ͕ ĐĞŶƚƌŝĨƵŐŝŶŐ ĂŶĚ
ĐƌLJƐƚĂůůŝnjĂƟŽŶ͘
 ĞdžƉůĂŝŶ ƚŚĞ ƵƟůŝƚLJ ŽĨ ŵŝdžƚƵƌĞƐ͘
 ĚŝīĞƌĞŶƟĂƚĞ ďĞƚǁĞĞŶ ĚŝůƵƚĞ ĂŶĚ ĐŽŶĐĞŶƚƌĂƚĞĚ ƐŽůƵƟŽŶ͘
 ĞdžƉůĂŝŶ ƵŶƐĂƚƵƌĂƚĞĚ͕ ƐĂƚƵƌĂƚĞĚ ĂŶĚ ƐƵƉĞƌƐĂƚƵƌĂƚĞĚ ƐŽůƵƟŽŶƐ͘

MIND OPENERS
 tŚĂƚ ĚŽ LJŽƵ ŵĞĂŶ ďLJ ŚŽŵŽŐĞŶĞŽƵƐ ŵŝdžƚƵƌĞ͍
 tŚĂƚ ŝƐ ŵĞĂŶƚ ďLJ ĐŽŵƉĞŶĞŶƚƐ ŽĨ ŵŝdžƚƵƌĞ͍
 ĂŶ LJŽƵ ƐĞƉĂƌĂƚĞ ƚŚĞ ŝŶĚŝǀŝĚƵĂů ĐŽŵƉŽŶĞŶƚƐ ŽĨ Ă ŵŝdžƚƵƌĞ͍ ,Žǁ͍

ŝƐĐƵƐƐ͘

Introduction

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KHWHURJHQHRXV PL[WXUH.

Homogeneous Mixture

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H\HV +HQFH RQO\ VLQJOH FRPSRQHQW LV VHHQ )RU H[DPSOH D PL[WXUH RI VXJDU

Times' Crucial Science and Environment 131 Book 7

DQG ZDWHU D PL[WXUH RI VDOW DQG ZDWHU HWF DUH KRPRJHQHRXV PL[WXUHV ,Q
WKH PL[WXUH RI VDOW DQG ZDWHU VDOW JHWV GLVVROYHG LQ ZDWHU DQG LW FDQQRW EH
VHHQ +HQFH ZH VHH RQO\ ZDWHU D VLQJOH FRPSRQHQW LQ WKH PL[WXUH

Activity 12.1 To produce a homogeneous mixture

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KRPRJHQHRXV PL[WXUH

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Heterogeneous Mixture

$ PL[WXUH LQ ZKLFK WKH SDUWLFOHV RI WKH FRPSRQHQWV DUH VHHQ LQ GLIIHUHQW
SKDVHV LV FDOOHG KHWHURJHQHRXV PL[WXUH. ,Q VXFK PL[WXUH WKH SDUWLFOHV RI
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VDQG UHPDLQV LQ VROLG SKDVH DQG ZDWHU UHPDLQV LQ OLTXLG SKDVH 6R ZH FDQ
VHH ERWK WKH FRPSRQHQWV ZLWK RXU QDNHG H\HV 7KXV D PL[WXUH RI VDQG DQG
ZDWHU LV D KHWHURJHQHRXV PL[WXUH

Times' Crucial Science and Environment 132 Book 7

Activity 12.2 To produce a heterogeneous mixture

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$ JODVV VSRRQ D JODVV URG VDQG ZDWHU HWF
3URFHGXUH
7DNH D JODVV DQG ÀOO WZR WKLUGV RI LW ZLWK ZDWHU 7KHQ DGG D VSRRQIXO

of sand into it.
6WLU WKH PL[WXUH ZLWK D JODVV URG IRU VRPH PLQXWHV
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7KH DPRXQW RI VDQG GRHV QRW GHFUHDVH ZKLOH VWLUULQJ ,W UHPDLQV WKH
VDPH %RWK WKH VDQG DQG ZDWHU LQ WKH PL[WXUH DUH VHHQ ZLWK RXU
naked eyes.

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7KH VDQG SDUWLFOHV GR QRW GLVVROYH LQ ZDWHU DQG WKH\ FDQ EH VHHQ
ZLWK RXU QDNHG H\HV 7KXV WKH PL[WXUH RI VDQG DQG ZDWHU LV D
KHWHURJHQHRXV PL[WXUH

Separation of Mixtures

7KH SURFHVV RI VHSDUDWLQJ WKH FRPSRQHQWV LQ SXUH VWDWH IURP WKHLU PL[WXUH
LV NQRZQ DV VHSDUDWLRQ RI PL[WXUH. 7KH PL[WXUHV FDQ EH VHSDUDWHG E\ XVLQJ
GLIIHUHQW PHWKRGV %XW DOO WKH PHWKRGV RI VHSDUDWLRQ RI PL[WXUH DUH EDVHG
RQ WKH SULQFLSOH WKDW µGLIIHUHQW FRPSRQHQWV RI D PL[WXUH KDYH GLIIHUHQW
SURSHUWLHV µ
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FKRLFH RI D SDUWLFXODU PHWKRG GHSHQGV XSRQ WKH QDWXUH DQG FRPSRVLWLRQ
RI WKH PL[WXUH 6RPH RI WKH FRPPRQ PHWKRGV XVHG LQ WKH VHSDUDWLRQ RI
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WKH JLYHQ PL[WXUH LV HYDSRUDWHG LQ DQ RSHQ YHVVHO ZKHUHE\ WKH OLTXLG
FRPSRQHQW WXUQV LQWR YDSRXU DQG WKH VROLG LV OHIW EHKLQG 7KH SURFHVV RI
HYDSRUDWLRQ LV XVHG WR VHSDUDWH FRPPRQ VDOW IURP LWV VROXWLRQ

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7KH VROLG VXEVWDQFH REWDLQHG E\ FRROLQJ WKH YDSRXU LV NQRZQ DV VXEOLPDWH

7KH SURFHVV RI VXEOLPDWLRQ LV XVHG WR VHSDUDWH YRODWLOH VXEVWDQFHV IURP
QRQ YRODWLOH LPSXULWLHV RU YLFH YHUVD 7KH VROLG VXEVWDQFHV ZKLFK FDQ EH
FKDQJHG GLUHFWO\ LQWR YDSRXU RQ KHDWLQJ DUH FDOOHG YRODWLOH VXEVWDQFHV.
)RU H[DPSOH LRGLQH, FDPSKRU, DPPRQLXP FKORULGH, QDSKWKDOHQH, etc
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FKDQJHG GLUHFWO\ LQWR YDSRXU RQ KHDWLQJ DUH FDOOHG QRQ YRODWLOH VXEVWDQFHV
)RU H[DPSOH FRPPRQ VDOW FDOFLXP FDUERQDWH VXJDU LURQ FRSSHU VDQG HWF

Activity 12.3 To separate sand and camphor from their mixture

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3URFHODLQ EDVLQ IXQQHO WULSRG VWDQG EXUQHU ZLUH JDX]H ZHW FRWWRQ
RU ZHW ÀOWHU SDSHU HWF

3URFHGXUH :HW FRWWRQ
7DNH D SURFHODLQ EDVLQ DQG SXW

WKH PL[WXUH RI VDQG DQG FDPSKRU
into it.

3OXJ WKH KROH RI IXQQHO IURP )XQQHO
inside with some cotton or a 3URFHODLQ
SLHFH RI ÀOWHU SDSHU DQG LQYHUW EDVLQ
WKH IXQQHO RYHU WKH PL[WXUH
0L[WXUH RI
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RI ÀOWHU SDSHU RU FRWWRQ IURP
RXWVLGH 7ULSRG VWDQG

%XUQHU

Times' Crucial Science and Environment 134 Book 7

3ODFH WKH SURFHODLQ EDVLQ DORQJ ZLWK WKH IXQQHO RQ ZLUH JDXJH
RYHU D WULSRG VWDQG

+HDW WKH EDVLQ ZLWK WKH KHOS RI EXUQHU RU VSLULW ODPS JHQWO\ IRU
VRPH PLQXWHV

5HPRYH WKH EXUQHU DQG WDNH RXW WKH IXQQHO IURP SRUFHODLQ EDVLQ
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KHDWLQJ :KHQ WKH YDSRXU FRPHV LQ FRQWDFW ZLWK WKH FRROHG LQQHU
ZDOOV RI WKH IXQQHO LW FRQGHQVHV EDFN WR LWV VROLG VWDWH
7KXV FDPSKRU DQG VDQG DUH VHSDUDWHG IURP WKHLU PL[WXUH E\ WKH
SURFHVV RI VXEOLPDWLRQ

Distillation

7KH SURFHVV RI HYDSRUDWLRQ RI OLTXLG RQ KHDWLQJ IROORZHG E\ FRQGHQVDWLRQ
RI WKH YDSRXU LQWR OLTXLG LV NQRZQ DV GLVWLOODWLRQ. 7KLV PHWKRG LV XVHG WR
VHSDUDWH D VROYHQW LQ SXUH VWDWH IURP LWV VROXWLRQ ,W FDQ DOVR EH XVHG WR
VHSDUDWH WKH PL[WXUH RI WZR PLVFLEOH OLTXLGV which have different boiling
SRLQWV 7KH OLTXLGV ZKLFK JHW PL[HG ZLWK HDFK RWKHU WR IRUP VROXWLRQ DUH
FDOOHG PLVFLEOH OLTXLGV. $OFRKRO DQG ZDWHU DUH PLVFLEOH OLTXLGV %XW ZDWHU
and kerosene are QRQ PLVFLEOH OLTXLGV EHFDXVH WKH\ UHPDLQ LQ GLIIHUHQW
OD\HUV LI WKH\ DUH PL[HG

Activity 12.4 7R VHSDUDWH VDOW DQG ZDWHU LQ SXUH VWDWH IURP
salt solution

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$ UHWRUW D UHWRUW VWDQG EHDNHU EXUQHU
WULSRG VWDQG ZLUH JDXJH FRQLFDO ÁDVN
ÀOWHU SDSHU HWF

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WKH WULSRG VWDQG 6XSSRUW WKH UHWRUW ZLWK WKH KHOS RI UHWRUW VWDQG

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3ODFH D FRQLFDO ÁDVN UHFHLYHU DW WKH HQG RI VLGH WXEH RI WKH UHWRUW
:UDS WKH VLGH WXEH ZLWK ZHW SLHFH RI ÀOWHU SDSHU RU FRWWRQ

&ORVH WKH RSHQLQJ RI UHWRUW ZLWK D FRUN DQG KHDW LW ZLWK EXUQHU
.HHS WKH ÀOWHU SDSHU RU FRWWRQ ZHW E\ DGGLQJ GURSV RI ZDWHU WLPH WR WLPH

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FRQGHQVHU VLGH WXEH RI WKH UHWRUW 7KH FRQGHQVHG ZDWHU LV WKHQ
FROOHFWHG LQ D UHFHLYHU FRQLFDO ÁDVN )LQDOO\ VDOW UHPDLQV LQ WKH
retort and the water is collected in the receiver.

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The water collected in the receiver after distillation is known as distillate
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Crystallization

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W\SHV 7KH\ DUH L DPRUSKRXV VROLG LL FU\VWDOOLQH VROLG

$PRUSKRXV VROLG

7KH VROLG LQ ZKLFK SDUWLFOHV DWRPV RU PROHFXOHV DUH QRW DUUDQJHG LQ UHJXODU
JHRPHWULF SDWWHUQ LV FDOOHG DPRUSKRXV VROLG 3ODVWLF ZRRG VDQG VRLO HWF
DUH DPRUSKRXV VROLGV $PRUSKRXV VROLG LV DOVR FDOOHG QRQ ²FU\VWDOOLQH VROLG

Times' Crucial Science and Environment 136 Book 7

&U\VWDOOLQH VROLG

7KH VROLG LQ ZKLFK WKH DWRPV RU PROHFXOHV DUH DUUDQJHG LQ D UHJXODU JHRPHWULF
SDWWHUQ LV FDOOHG FU\VWDOOLQH VROLG 6RGLXP FKORULGH FRSSHU VXOSKDWH VXJDU
DOXP SKHQRO HWF DUH FU\VWDOOLQH VROLGV 7KH FU\VWDOOLQH VROLGV DUH PDGH XS
of crystals. $ FU\VWDO LV D VROLG VXEVWDQFH ERXQGHG E\ SODQH IDFHV WKDW PHHW
DW VKDUS HGJHV WR IRUP D UHJXODU JHRPHWULF VKDSH There are different kinds
RI FU\VWDOV RQ WKH EDVLV RI WKHLU VKDSH DQG VL]H 7KH\ DUH FXELF WHWUDJRQDO
RUWKRUKRPELF PRQRFOLQLF WULFOLQLF KH[DJRQDO HWF

KH[DJRQDO HWF

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9DULRXV VKDSHV RI FU\VWDOV NRFKLWUD

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VROYHQW VR WKDW WKH VROXWLRQ EHFRPHV VDWXUDWHG DW KLJKHU WHPSHUDWXUH 7KH
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IURP WKH VROXWLRQ DQG JHWV GHSRVLWHG DV EHDXWLIXO FU\VWDOV DW WKH ERWWRP RI
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Activity 12.5 To separate copper sulphate crystals from its solution

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&RSSHU VXOSKDWH VROXWLRQ D SURFHODLQ EDVLQ D WULSRG VWDQG ZLUH
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5HPRYH WKH EXUQHU DQG SODFH WKH SURFHODLQ
EDVLQ LQ D FRRO SODFH IRU PLQXWHV ,I
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WKH ZDWHU WURXJK EXW WKH IDVWHU FRROLQJ
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RQ D ÀOWHU SDSHU 7KH OLTXLG OHIW RQ WKH SURFHODLQ EDVLQ DIWHU UHPRYLQJ
the crystals is called PRWKHU OLTXRU.
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Centrifuging
Activity 12.6 To separate a mixture by centrifuging.

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FHQWULIXJLQJ LV GHÀQHG DV D SURFHVV RI &RYHU
VHSDUDWLQJ YHU\ ÀQH VXVSHQGHG VROLG RU
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FOHDU OLTXLG UHPDLQV DW WKH XSSHU OHYHO 7KHVH WZR OD\HUV DUH WKHQ VHSDUDWHG
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Utility of Mixtures

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DUH VXPPDUL]HG EHORZ

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WKH\ DUH XVHG
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DV ZHOO DV LRGLQH WR RXU ERG\

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sŽůĂƟůĞ ͗ ĞĂƐŝůLJ ĞǀĂƉŽƌĂƟŶŐ ŽďũĞĐƚ

DŝƐĐŝďůĞ ͗ ƚŚĞ ƐƵďƐƚĂŶĐĞƐ ǁŚŝĐŚ ŐĞƚ ŵŝdžĞĚ ĞĂƐŝůLJ

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Main Points to Remember

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WKH VDPH SKDVH LV NQRZQ DV KRPRJHQHRXV PL[WXUH

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DV HYDSRUDWLRQ

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PDFKLQH DW KLJK VSHHG LV NQRZQ DV FHQWULIXJLQJ

Exercise

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D 7KH PL[WXUH LQ ZKLFK WKH FRPSRQHQWV RI WKH PL[WXUH FDQ EH VHHQ
VHSDUDWHO\ LV FDOOHG

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L &DPSKRU LL ,RGLQH

LLL $PPRQLXP FKORULGH LY $OO RI WKHVH

c. Alcohol and water are
L 0LVFLEOH OLTXLGV LL ,PPLVFLEOH OLTXLGV

LLL 9RODWLOH OLTXLGV LY $OO RI WKHP

Times' Crucial Science and Environment 140 Book 7

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Times' Crucial Science and Environment 141 Book 7

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Times' Crucial Science and Environment 142 Book 7

Chapter

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ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϰ

OBJECTIVES

At the end of the lesson, the students will be able to :
 ĚĞĮŶĞ ƐŽůƵƚĞ͕ ƐŽůǀĞŶƚ ĂŶĚ ƐŽůƵƟŽŶ͘
 ĚŝƐƟŶŐƵŝƐŚ ďĞƚǁĞĞŶ ĚŝůƵƚĞ ĂŶĚ ĐŽŶĐĞŶƚƌĂƚĞĚ ƐŽůƵƟŽŶ͘
 ŝŶƚƌŽĚƵĐĞ ĂŶĚ ĚŝƐƟŶŐƵŝƐŚ ƵŶƐĂƚƵƌĂƚĞĚ͕ ƐĂƚƵƌĂƚĞĚ ĂŶĚ ƐƵƉĞƌ ƐĂƚƵƌĂƚĞĚ

ƐŽůƵƟŽŶƐ͘
 ĞdžƉůĂŝŶ ƚŚĞ ƵƐĞƐ ŽĨ ƐŽůƵƟŽŶƐ͘

MIND OPENERS
 tŚĂƚ ĂƌĞ ƐŽůƵƚĞ ĂŶĚ ƐŽůǀĞŶƚ͍
 tŚĂƚ ŝƐ ƚŚĞ ŚŽŵŽŐĞŶĞŽƵƐ ŵŝdžƚƵƌĞ ŽĨ ƐŽůƵƚĞ ĂŶĚ ƐŽůǀĞŶƚ ĐĂůůĞĚ͍
 tŚĂƚ ŝƐ ƚŚĞ ƐŽůƵƟŽŶ ĐĂůůĞĚ ŝĨ ƚŚĞƌĞ ŝƐ ĞdžĐĞƐƐ ĂŵŽƵŶƚ ŽĨ ƐŽůƵƚĞ͍
 ĂŶ LJŽƵ ƚĞůů ƚŚĞ ƵƐĞƐ ŽĨ ƐŽůƵƟŽŶƐ͍ ŝƐĐƵƐƐ͘

Introduction

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Solvent

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Solute Solvent

ϭ͘ ƐŽůƵƚĞ ŐĞƚƐ ĚŝƐƐŽůǀĞĚ ŝŶ ƚŚĞ ƐŽůǀĞŶƚ͘ ϭ͘ ƐŽůǀĞŶƚ ĚŝƐƐŽůǀĞƐ ƚŚĞ ƐŽůƵƚĞ͘

Ϯ͘ /ƚƐ ĂŵŽƵŶƚ ŝƐ ůĞƐƐ ŝŶ ĐŽŵƉĂƌŝƐŽŶ ƚŽ Ϯ͘ /ƚƐ ĂŵŽƵŶƚ ŝƐ ƌĞůĂƟǀĞůLJ ŵŽƌĞ ŝŶ Ă

ƚŚĂƚ ŽĨ ƐŽůǀĞŶƚ ŝŶ Ă ƐŽůƵƟŽŶ͘ ƐŽůƵƟŽŶ͘

ϯ͘ ƐŽůƵƚĞ ŝƐ ŐĞŶĞƌĂůůLJ ŝŶ ƐŽůŝĚ ƐƚĂƚĞ͕ Ğ͘Ő͘ ϯ͘ ƐŽůǀĞŶƚ ŝƐ ŐĞŶĞƌĂůůLJ ŝŶ ůŝƋƵŝĚ ƐƚĂƚĞ͕

ƐĂůƚ͕ ƐƵŐĂƌ͕ ĂůƵŵ ĞƚĐ͘ Ğ͘Ő͕͘ ǁĂƚĞƌ͕ ĂůĐŽŚŽů͕ ĞƚĐ͘

Dilute and Concentrated Solution

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Activity 13.1 To prepare dilute and concentrated solution

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in glass B.
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Unsaturated, Saturated and Super Saturated Solution

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Times' Crucial Science and Environment 146 Book 7