Shubharambha Science & Env 6 -2077 press re

Activity

To observe the rectilinear propagation of light
Materials required: Three cardboards, a candle, matchbox

Observe Hole

Cardboard

Candle

Procedure

1. Take three cardboards of same shape and size

2. Make a hole in each of them at the same heights.

3. Arrange the boards vertically in such a way that all the holes are at the
same height and in a straight line.

4. Place a lighted candle at one end of the outer cardboard in such a way
that the flame of the candle will be at the same height of the holes.

5. Look through the hole from the other end. Do you see the flame of the
candle?

6. Move the central cardboard slightly so that its hole is not in the straight
line with the others. Do you see the candle flame this time?

Observation

We see the candle flame from the other side before moving the central cardboard but
we cannot see the candle flame from other side after moving the central cardboard as
the holes of all the cardboards do not lie in a straight line.

Conclusion

From this activity we can conclude that light in a medium always passes through a
straight line. This phenomenon is called rectilinear propagation of light.

Ray and Beam of Light

We have seen that light travels in a straight line. (a)
The straight line along which light travels is called (b)
a ray of light. It is denoted by a straight line with
an arrowhead. The arrowhead gives the direction of Fig: Ray and Beam of Light

propagation of light.

The collection of rays of light is called the beam of light.

Blooming Science & Environment Book 6 51

A beam of light is of three types.

(i) Parallel: If all the rays of a beam are parallel, then it is called parallel beam of
light. Fig. (a).

(ii) Convergent: If all the rays of the beam come to a point, then it is called
convergent beam. Fig. (b)

(iii) Divergent: If all the rays of the beam spread away from each other, then it is
called the divergent beam. Fig. (c)

Scan for practical experiment

(a) Parallel beam (b) Convergent beam (c) Divergent beam

Fig: Light beams visit: csp.codes/c6e10

Shadow

While walking in the sun you must have seen a dark thing, which walks on the road
along with you. This dark thing is your shadow.

All the opaque objects make shadow. A translucent object produces a light shadow
and a transparent object does not cast a shadow at all.

Shadows are formed when the objects block the light coming from its source.

Activity

Switch on a torch in a dark room and point it A
towards the wall of your room. The rays of light B
fall on the wall, which is shown by straight line in
the given fig. Now, place an object AB in between Fig: Formation of a shadow
the torch and the wall. The object AB blocks the
rays in between A and B. The portion of the wall
directly behind the object AB does not receive
any light. Thus, a dark shadow of the object AB is
formed on the wall.

The concept that light travels in a straight line is responsible for the formation of a
shadow. The dark shadow is umbra and bright shadow is pen umbra.

Reflection of Light Reflected ray

Are you familiar with mirrors?

In our home we use a plane mirror as a looking Torch Incident ray mPliarrnoer
glass. Plane mirror is a flat, smooth glass plate

with one of its a face silvered. Fig: Reflection of light

52 Blooming Science & Environment Book 6

Activity

Take a torchlight and switch on it and allow the light from it to fall on the mirror
surface of a plane mirror

What will happen?

The ray of light returns to the same medium.

When a beam of light travelling through one medium falls on a smooth surface, the
light returns towards the same medium. This phenomenon of returning back of the
light in the same medium is called reflection of light.

Rays of light that are incident are called incident rays while those that are sent back
are called reflected rays.

We see an object when it reflects light to our eyes. The amount of light reflected by an
object depends upon its surface. Hard, smooth and shiny surfaces are good reflectors
of light. But the rough and dull surfaces are poor reflectors of light.

The phenomenon of returning of light rays when they strike the surface of a body is

called the reflection of light. N Norman ray

When the reflected light enters our eyes,we A B

can see the object that reflects the light. When

mirror is placed in sunlight, reflects most of Reflected ray
the light falling on it. Rays of light that an Incident ray

incident are called incident rays while those O Plane mirror

that are sent back are called reflected rays.

Pinhole Camera Fig: Reflection of light

It is the optical device which forms the actual the resulting
person image
inverted image of the objects. It consists the pinhole

of light proof box having a small hole at

one side, through which light is made to

pass inside a box where inverted image

of the object is formed. it works on the

principle of rectilinear propagation of light.

Main Points to Remember

1. Light is a form of energy, which enables us to see things around us.
2. An object, which gives out light, is called source of light.
3. There are two types of sources of light:
(i) Natural sources of light
(ii) Artificial sources of light

Blooming Science & Environment Book 6 53

4. The objects, which have their own light, are called luminous bodies.
The objects, which do not have their own light, are called non-luminous bodies.

5. An object, which allows most of the light to pass through it is called
transparent object. An object, which allows only a part of the light to pass
through it is called translucent object.

6. An object which does not allow light to pass through it is called opaque object.
7. Light travels in straight line, it is called rectilinear propagation of light.
8. The straight line along which light travels is called a ray of light. The

collection of rays of light is called beam of light.
9. Shadows are formed when the objects block the light coming from its surface.
10. The phenomenon of returning back of light in the same medium is called

reflection of light.

PRO J ECTWORK

Make your room dark. Beat a duster or a rug so that dust flies in your room. Now, light
a torch and focus the beam on the wall. Study the beam of light between the torch and
the wall. You can see the path of light. Also study the edge of the beam. Is it straight
or curved? Draw a figure.

Exercises

1. Fill in the blanks:

a. ………………. is the most important sources of light on the earth.
b. ………………. is a form of energy which gives the sensation of vision.
c. Lamp, electric bulb, etc are ……………. sources of light.
d. Bodies through which light can pass easily and through which we can see

clearly are called ………………….. substances.
e. The study of light is called …………………..

2. Tick (√) for the correct and (x) for the incorrect statements.

a. The moon is a luminous body.
b. The moon is an artificial source of the light.

54 Blooming Science & Environment Book 6

c. All shining heavenly bodies are luminous.

d. Transparent bodies do not have shadow.

e. Light always travels in a straight line.

3. Classify the following into natural and artificial sources of light:

Sun, firefly, tube light, burning candle, glowing electric bulb, moon

4. Classify the following into luminous and non-luminous bodies:

Sun, star, chair, firefly, table, pencil, pen, tree, tube light, burning candle, book

5. Define:

a. Light c. Transparent object b. Rectilinear propagation of light
d. Shadow e. Reflection of light

6. Write the differences between:

a. Luminous and non-luminous bodies
b. Natural and artificial sources of light

7. Answer the following questions:

a. What is light? Why do we need light.

b. How do you prove that the light travels in a straight line?

c. Books, stones, etc. form their shadows in the light. Why?
d. A firefly can be visible in dark. Why?
e. Name any four natural sources of light.
f. Name any four artificial sources of light.
g. Define reflection of light.

h. What is shadow? What types of objects form shadow?

i. What is rectilinear propagation of light?
j. Define transparent and opaque objects with examples.

Blooming Science & Environment Book 6 55

8. Draw the diagram of:

a. Any two natural sources of light.
b. Any two artificial sources of light
c. Any two luminous bodies.

dG. loAsnsyatwryo non-luminous bodies
9. Explain an activity to show that light travels in a straight path.
Intense : Very strong

Fluorescent : Substance producing bright light by using radiation.

Visible : that can be seen

Invisible : that cannot be seen

Light : an energy which helps to see things

Luminous : the bodies which have their own light

Non-luminous : the bodies which do to have their own light

Transparent : the object which allows light to pass through it.

Translucent : the object which allows a part of light to pass through it

Opaque : the objects which do not allow the light to pass through it

Reflection : to get back, to bounce off

Shadow : region of no light due to opaque object in the way of light

56 Blooming Science & Environment Book 6

6Chapter Sound

Learning Outcome Estimated Periods: 4+1
On the completion of this unit, students will be able to:

 define sound and tell sources of sound.
 introduce wave
 demonstrate transmission of sound in different mediums.
 demonstrate sound produced according to the nature and vibration of objects.

Introduction

You like to close your ears when an aeroplane passes over you. You feel uncomfortable
when a dog barks nearby. You turn on radio and enjoy its music. You know the changes
of classes in your school when the bell rings. In all of these example you take help of
your ears which receive the sound and make it respond to the sound. Sound is a form
of energy which is received with our ears and produces sensation of hearing.

Sources of Sound

The objects which produce sound are called sources of sound. If you place your
finger on your throat while you are speaking, you can feel something moving. When
you touch the front part of a radio that’s been turned on, you feel something moving.
When the guitar is being played, the strings are set into motion. In all of these
examples, there is to and fro motion of the objects, and the sound is produced. Sound
is produced by the vibration of the sounding body.

Different instruments that produce the sound are given below:

Flute

Tuning fork Drum

Scan for practical experiment

Bell Guitar

Fig: Sources of sound visit: csp.codes/c6e11

Blooming Science & Environment Book 6 57

Activity

To observe that sound is produced by vibration

Materials required: A tuning fork, a rubber pad, a water
trough and water.

Take a water trough. Fill about two third part of the trough
with water. Take a tuning fork and strike it on the rubber
pad so that it starts to produce sound. Now dip the tip of
the vibrating prongs of tuning fork just on the surface of Vibration produces sound
water as shown in figure. You will see the disturbance
in water. This disturbance is due to the vibration of the prongs of the tuning fork. If
a tuning fork which is not sounding is placed in water, it does not disturb the water
because it is not in vibration. This experiment shows that sound is produced by the
vibration of objects.

In all the instruments, sound is produced due to the vibration of different parts. Some of
the common examples are given below in the table:

Instruments Vibration parts
Guitar Strings
Turning fork Prongs
Bell Body of the bell
Drum Stretched leather
Flute Air inside the pipe

A mosquito produces sound due to the vibration of its wings. Air vibrates inside a flute,
a mouth organ and a whistle to produce sound.

What is a tuning fork?

A tuning fork is a convenient source of the sound for the laboratory. It is a U-shaped part
with two arms called the prongs. If one of the prongs is struck against a rubber pad, it
gets vibrated. Due to the vibration of the prong the sound is produced.

Loudness of Sound

If a drum is stroke gently, a soft sound is heard. If it is stroke hardly, loud sound is
heard. The greater the back and forth movement of the body, the louder is the sound it
produces.Loudness is related to the energy in the sound wave. A sound is louder when it
is transmitted with more energy.

58 Blooming Science & Environment Book 6

Activity

Materials required: A drum, drum stick, rice or other grains

Procedure:

1. Sprinkle some rice or other grains on a drum.

2. Strike the drum gently

3. What do we notice?

Now, strike the drum hardly. What do we notice? We find
that grains of rice dance slowly on the drum in the first case
and violently in the latter case. That is, back and forth motion
of the rice grains is slow if the drum is beaten gently and we
hear the soft sound. The motion of the rice grains is more if
the drum is beaten hardly and we hear the loud sound. Thus,
loudness of the sound depends on the degree of back and forth movement of the body.

When a drum is beaten gently, is the sound soft or hard? Do the grains jump low or
high? When the drum is beaten harder, is the sound produced soft or hard? Do the
grains jump low or high? In which case is the back and forth movement more?

Pitch (Sharpness of Sound)

The sharpness or shrillness of sound is called pitch. The nature and quality of
sound wave depends upon the mode of frequency that the source produces. Some
vibrating sources produce sharp sound and some others produce the dull sound.If a
body vibrates fastly, more sharp sound is heard. Different substances have different
sharpness of sound. If sounding body is small, sharpness of sound is more. Similarly
if the string of source is thin it gives sharp sound.

Activity

Materials required: Guitar

Procedure: Guitar

1. Take a guitar and pluck its thin wire softly. Listen the sound
produced.

2. Now, tight the screw to stretch the wire. Repeat the activity 1, listen to the sound
produced.

Does the sharpness of the sound produced change or not? You will find that sharpness
of the sound of the plucking wire increases as it is stretched gradually. This activity
confirms that when a wire is stretched the sharpness of sound produced by it increases.

Blooming Science & Environment Book 6 59

Acute and Dull Sound

We hear different types of sound. Some of them are acute or shrill sound and some
of them are dull sound. A woman’s voice is generally more acute than a man’s voice.
Buzzing of a mosquito is an acute sound whereas the roaring of a lion is a dull sound.
The thinner wires of the guitar give out acute sound while the thicker wires of the
guitar give out dull sound.

Activity

Take some rubber bands. Tie them up in a board Pin
with fixed nails as shown in the figure. Pluck the
rubber bands and hear the sound produced by them.

Now make a conclusion about the production of Rubber
acute and dull sound from this activity.

The result of this activity is: Rubber bands across the nails

When the wire is more stretched, the acuteness of the sound increases,

When the wire is less stretched, the acuteness of the sound decreases,

When the length of wire is increased, the acuteness of the sound decreases.

When the length of wire is decreased, the acuteness of the sound increases.

Transmission of Sound

If a body vibrates, it makes the adjacent air molecules to vibrate. These molecules,
in turn, transfer their vibrations to other molecules and so on. When these vibrations
reach our ears, we hear the sound. The phenomenon due to which the sound travels
from one place to another is called transmission of sound.

Sound needs material medium for its transmission. The medium may be any of solid,
liquid and gas. The sound travels the fastest in solid medium and the slowest in the
gaseous medium. Sound cannot travel through vacuum.

Wave

A wave is a disturbance in a medium which Showing bell sound wave
carries energy from one point to another without
there being a contact between the two points.
A wave is produced by the vibrations of the
particles of the medium through which it passes.
For example: water waves, light waves, sound
waves, radio waves etc.

When a bell rings, sound waves are produced which move away from the bell
through the air and reach to our ears, here, only the air molecules vibrate and the
sound energy travels through the vibrations of the molecules of air but the air does
not move. There are two types of wave.

60 Blooming Science & Environment Book 6

i. Transverse wave
ii. Longitudinal wave

i. Transverse Wave Vibrations of D
particles
The wave in which the particles of the
medium vibrate up and down at right angles C A
to the direction of propagation of the wave B Direction of wave

is called a transverse wave. Transverse wave is possible only in solids and liquids. In

a transverse wave, when the vibrating particles move upward, a hump is formed.

This hump is called crest. When the vibrating particles move downward a hollow is

formed. This hollow is called trough. Crest Crest Crest

The examples of transverse wave are water

wave, waves produce on a rope, light waves

and radio waves, etc. Trough Trough Trough

ii. Longitudinal Wave Showing crest and through

The wave in which the particles of the medium vibrate to and fro (back and forth) in
the same direction in which the wave propagates is called a longitudinal wave.

Greater Less Greater Less CR C R C R
density density density density

In a longitudinal wave the vibrations causing the wave are in the same direction as
the wave itself.

Longitudinal wave is possible in all three mediums i.e. in solid, liquids and gasses.
Longitudinal wave travels in the form of compressions and rarefactions. Compression
is the part of the longitudinal wave in which particles of the medium coming close
together and rarefaction is the part of the longitudinal wave in which the particles
of the medium getting further apart. In the figure, C represents the position of the
compression and R represents the position of the rarefaction.

The examples of longitudinal wave are sound wave, the wave produced in a spring,
etc.

Propagation of Sound

We are able to hear the sound in presence of three components;

a. The sources of sound (any vibrating object)
b) Medium for transmission

c) The receiver (ears)

Sound is propagated in the form of longinidinal wave. It needs material medium to
propagate. It can propagate in solid, liquid or gas medium but it can not propagate in
vacuum. That's why sound is also known as mechanical wave.

Blooming Science & Environment Book 6 61

Transmission of Sound in Solid

Activity

1. Take a wooden stick and press your ear at one end of it.
2. Tell a friend to knock gently at the other end.
3. You will be able to hear the sound very clearly.
This shows that sound can travel through solids.

Activity

1. Take two tin cans.
2. Fix a paper at one end of the tin can. Tie a thread to the bottom of the can and pass

the thread to the other end of another tin can.

3. Let the next tin can be held by your friend at a certain distance, staining the thread
straight.

4. Use this to talk to your friend. This activity also proves that sound can travel
through solids.

The above experiment shows that sound propagates through solids. The speed of
sound in steel is about 5200 m/s.

62 Blooming Science & Environment Book 6

Transmission of Sound in Liquids

Activity

1. Take a plastic bucket of about 10 litres
capacity.

2. Fill it with water.

3. Place a bell in the water such that it should
not touch the walls of the bucket.

4. Strike the bell with a hammer. A very weak
sound may be heard.

5. Now, touch the bell with the walls of the bucket and strike it again with hammer.

6. A louder sound may easily be heard.

This shows that sound can travel through liquid also.

The speed of sound in water is about 1500m/s

Transmission of Sound in Gases

The sound travels in gases. The sound we hear is transmitted through the air. Air is
a material medium. The speed of sound in air is very less than solid and liquid. The
speed of sound in air is about 332 m/s only.

Activity

1. Take a balloon filled with water.
2. Hold it against one of your ears.
3. Close your other ear firmly with your hand.
4. Slowly tap the balloon on the other side.
You will be able to hear the sound clearly. This shows that

sound can travel through liquids.

Medium is required for the transmission of sound

Activity

To show that sound requires a medium to travel. Fig: Bell Jar
1. Take an electric bell hung inside a bottle.
2. The bottle is sealed by a stopper.
3. The lower end of the bottle is connected to a vacuum pump

which is used to extract air from the bottle.
4. Put the switch of the bell on so that it rings. You can hear the

bell.
5. Now start the pump. You will notice that as the air gets removed

from the bottle, the sound reaching you becomes more and
more faint. Ultimately, you cannot hear the sound at all.
Sound, therefore, requires a medium to travel.

Blooming Science & Environment Book 6 63

Speed of Sound

Sound travels through air at a speed of about 332 m/s. This means if you shout, your
friend standing 332 metres away from you, would hear your shout after 1 second.

In solids and liquids, the molecules are much closer together than in air. The vibrations
are therefore, transferred faster to other molecules in solids and liquids than in air.
Therefore, the speed of sound in solids and liquids is more than the speed of sound
in air. In fact, sound travels at a speed of about 1500 m/s in water and at 5200 m/s
in steel.

Medium Speed in m/s Medium Speed in m/s
Air 332 Steel 5000 to 7000
Wet air 400 Wood 4000 to 5000
Water 1500 Rubber 30 to 70
Copper 3700 Glass 5000 approx.

Main Points to Remember

1. Sound produces the sensation of hearing.
2. Sound is produced when a body vibrates.
3. Sound may be loud or faint.
4. Shrillness or flatness of sound is called its pitch.
5. A shriller sound is said to have high pitch.
6. The pitch of sound depends on the rate of vibration of a sounding body which

changes according to the size of the body.
7. The velocity of sound in air is about 332 m/s, in water is about 1500 m/s and in

steel is about 5200 m/s.
8. The wave in which the particles of the medium vibrate up and down at right

angles to the direction of propagation of the wave is called a transverse wave.
9. The wave in which the particles of the medium vibrate to and fro (back and

forth) in the same direction in which the wave propagates is called a longitudinal
wave.
10. Sound is propagated in the form of longinidinel wave for which meterial
medium is needed for the propagation of sound.

PRO J ECTWORK

1. Beat a drum and see vibration on it. Vibration will not be seen clearly. Put some
wheat or rice grains on the surface of drum and beat again, you will see grains move
up and down. It shows that drum is vibrating. It proves that a vibrating body
produces sound.

2. Stretch the rubber bands on the plane surface with the help of nail. Tighten some of
the rubber bands and loose few of them. Now, observe the sound produced by tight
and loose rubber bands by plucking them.

64 Blooming Science & Environment Book 6

Exercises

1. Fill in the blanks:

a. A vibrating source can produce ……………..
b. A …………….. is essential for the transmission of sound.
c. The ………………. of sound is called pitch of sound.
d. Pitch increases as the ……………. increases.
e. Pitch of sound depends upon ……………..
f. The velocity of sound in water is ……………..

2. Write ‘T’ for true and ‘F’ for false statements

a. A tuning fork is not a source of sound.
b. Sound is a form of energy.
c. A medium is not essential for the transmission of sound.
d. Males have high pitch of sound.
e. A vibrating body does not produce sound.

3. Match the following:

Sound sharper sound

A vibrating body louder sound

Thinner wire of guitar form of energy

Roaring of a lion produces sound

4. Answer the following questions:

a. What is sound?
b. How is sound produced?
c. Name different types of sound that we hear in our daily life.
d. How does a mosquito produce sound?
e. Which part of the mosquito produces sound?

Blooming Science & Environment Book 6 65

f. What part of the drum produces sound?

g. How can you know the vibration of the tuning fork?

h. What happens when an object produces sound?

i. Why does the sound vary when the rubber band is stretched?

j. Draw the diagram of four objects that produced sound.

k. Describe an experiment to show that pitch of the sound increases with
increase in length of the object.

l. Describe an experiment to show medium is needed for the propagation of
sound.

m. Describe an experiment to show that the sharpness of sound increase as
vibration increases rapidly.

n. What is longitudinal wave?

o. Define transverse wave.

p. Write velocity of sound in air, water and glass.

Glossary

Tuning fork : an instrument to produce sound.

Vibration : fast side to side or upward and downward motion.

Loudness : sound depends on the displacement of vibration.

Pitch : the sharpness of sound.

Amplitude : the maximum displacement of particles.

66 Blooming Science & Environment Book 6

7Chapter Magnetism

Learning Outcome Estimated Periods: 4+1
On the completion of this unit, students will be able to:

 define a magnet and tell the properties of a magnet.
 describe magnetic and non-magnetic substances.
 explain and find field of magnet.
 explain and demonstrate magnetic poles in magnet.

Nearly 2000 years ago, a man of Magnesia accidentally found a type of stone, which
could attract iron. Magnesia was a city in ancient Asia Miner. They named this rock
“Magnesia” after the place of discovery. It is also found that when this stone was
suspended freely with a fine thread, it always showed north and south direction itself.
People used this property of the stone to locate the direction. Thus, they gave a name
‘Leading Stone’. The word gradually changed to ‘load stone’. Every magnet has its
own magnetic power due to which it can attract iron pieces.

Magnetic and Non-magnetic Substances

Activity

Collect many small objects like steel pin, comb, pencil, book, cork, glass, knitting
needle, 1 rupee coin, etc. Take a magnet and touch the collected objects with it.

Which of them are attracted by magnet and which of them are not?
Complete the following table:

S. No. Objects Attracted by magnet Not attracted by magnet

The above activity clearly shows that a magnet cannot attract all objects. A magnet
attracts only some metals like iron, steel, nickel and cobalt. Magnet does not attract
other metals. A magnet does not attract other materials like wood, book, glass, copper,
brass, plastic, etc.

Blooming Science & Environment Book 6 67

Thus depending upon the effects of a magnet all the substances are divided into two
types.

(i) Magnetic Substances: Those substances which are attracted by magnet are
called magnetic substances. Iron, cobalt and nickel are examples of magnetic
substances.

(ii) Non-magnetic substances: Those substances which are not attracted by a
magnet are called non-magnetic substances. Wood, plastic, copper, paper etc,
are examples of non-magnetic substances.

Magnetic Materials

Faraday showed that all substances are affected by magnet. Substances like iron,
nickle and cobalt are strongly attracted by a magnet and are known as ferromagnetic
substances. Substances like manganese, platinum and oxygen show feeble attraction
and are known as paramagnetic substances. Substances like bismuth, antimony,
phosphorous, zinc, mercury, lead, tin, water and copper are repelled by magnets and
are known as diamagnetic substances.

Natural and Artificial Magnet

The magnet which is obtained from nature is called natural magnet. The loadstone is
an example of natural magnet.

Scan for practical experiment

Fig: Artificial magnets in different shapes visit: csp.codes/c6e12

The magnet, which can be made from magnetic substance is called artificial magnet.
Artificial magnets are available in various shapes and sizes. The different shapes
of magnets are (i) Bar magnet (ii) U-shaped magnet (iii) Horse - shoe magnet (iv)
Cylindrical magnet (v) Magnetic needle, etc.

Differences between Natural and Artificial Magnet

Natural Magnet Artificial Magnet

1. It is found in nature. 1. It is man made.

2. Its attracting power is very low. 2. Its attracting power is very high.

3. Loadstone is an example of it. 3. Bar magnet, rod magnet, horseshoe
magnets are examples of it.

68 Blooming Science & Environment Book 6

Properties of a Magnet

1. Directive Property

When a magnet is suspended freely, its one end always points to the north direction
and other end to the south direction. This property of magnet is called the directive
property.

Activity

Materials required: Stand, thread, bar magnet

Procedure Wooden stand
Thread
1. Take a bar magnet and tie a thread at the middle of
it. Suspend it horizontally in a stand to move freely. N

2. When the magnet comes at rest, push it slightly to S Bar magnet
move and note the direction to which the ends point
at rest. Freely suspended magnet

The end of the magnet which points towards the north, is
called the north pole and the other end is called the south
pole.

Repeat the same activity with an iron piece of the same shape. Does it rest in north
and south as a magnet?

2. Attractive Property

A magnet attracts magnetic substances like iron, cobalt, nickel, steel and their alloys.
This property of a magnet is called the attractive property.

Activity

Materials required: Iron filings, saw dust, bar magnet, paper

Procedure

1. Mix up some iron filings with saw dust. Move a bar
magnet over the mixture. You will find that the iron filings
are attracted by the magnet.

Food and chemical industries use magnets to separate iron
particles, which may get mixed accidentally into their products. This helps to get safe
food. In many factories, magnets help to lift the heavy weights and to separate iron
pieces from a heap of waste materials.

Blooming Science & Environment Book 6 69

3. Like poles repel and unlike poles attract

The north pole pushes away the north pole and pulls the south pole, i.e. like poles
repel and unlike poles attract.

Activity

Take two bar magnets. Suspend one magnet freely by a piece of thread. After a while
the magnet will come to rest pointing the north-south direction. Bring the north pole of
other bar magnet near the south pole of the suspended magnet, it attracts. Bring south
pole near south pole, it repels. This property is called law of magnet.

SN N
S

N

N
S
Like poles repel and unlike poles attract

4. The magnetic force is more at the ends of a magnet and negligible at its
middle.

A magnet has more magnetic force at its ends and less magnetic force at its middle.

Activity N

Materials required: Some pins, a bar magnet S
Procedure

1. Take some pins.
2. Roll a bar magnet over it.

Where does the maximum number of pins stick?

We find that the most of the pins remain stuck at the ends of the magnet. Thus, the
magnetic force is greater at the ends of the magnet than in the middle.

5. Magnetic poles always exist in pair.

If a bar magnet is broken into two pieces, it is noticed that each piece behave as
magnet. It means, new poles are formed at the broken ends as shown in the figure.
If the breaking process is continued, each such broken part behaves as a magnet,
how tiny it may be. This means, every magnet has two poles. These poles cannot be
separated.

70 Blooming Science & Environment Book 6

Activity

Materials required: Razor blade, bar magnet. N

Procedure S
1. Take a half piece of razor blade as shown in

the figure

2. Place it on a table

3. Rub it with the one end of the bar magnet in a
single direction

4. Repeat the process for 40 to 50 times. Now
the blade becomes a magnet. We can test it by using the bar magnets.

5. Break the blade carefully into two parts and test it again.

We will find that each piece of the blade has two opposite poles. We can break the blade
into smaller pieces but we cannot separate the poles. This shows that the magnetic
poles always exist in pair.

Magnetic length and Length of magnet

The region at each end of a magnet where the external magnetic field is strongest is
called magnetic pole. It lies a little inside the end of the bar magnet from its end at
both sides.

The distance between two ends of a magnet is called length of a magnet and
the distance between two poles of a magnet is called magnetic length. The magnetic
length is little less than the real length of a magnet. Theoretically, the magnetic length
of a bar magnet is nearly 0.84 times that of its length.

Test of a Magnet

Method 1

To test whether a given iron bar is a magnet or not, N-pole of a magnet is taken close
to one end of the iron bar. Notice whether there is attraction or repulsion (Fig. a).
Now the above activity is repeated by using the S-pole of the bar magnet close to the
same end of the iron bar and observe whether there is attraction or repulsion (Fig. b).
If there is attraction in both the ends, the iron bar is just a magnetic material. If there
is repulsion at the end it is sure that( fig. c) the iron bar is a magnet. Thus, repulsion
is the surest test for the magnetism.

N S S

S N N
(a) The end is attracted by
(b) The end is attracted by (c) The end is repelled by the
the north pole the south pole south pole

Blooming Science & Environment Book 6 71

Method 2 S

Tie the given iron bar at its middle with silk or nylon thread and
suspend it freely. If it comes at rest pointing the north-south
directions, move it gently to disturb the direction. If it remains in N
N-S direction again and again, the unknown iron bar is a magnet. If
it points different directions, the bar is not a magnet.

Magnetic Field

Magnetic substances are attracted

strongly by a magnet near to it. If it is kept N S
gradually away from such substances,

attractive magnetic force also decreases

in the same way. Beyond a certain region

of magnetic field around the magnet, it has no influence on magnet substances. The

space around a magnet, where magnetic force can be felt by a magnetic body is

called magnetic field of the magnet.

Activity

To find the magnetic field of a magnet.

Materials required: a bar magnet, a magnetic compass and a white sheet

Procedure:

i) Put a white sheet of paper on a table and a bar magnet on it.

ii) Draw the outline of magnet with pencil and keep a compass near one
end of bar magnet

iii) The compass needle is affected by the magnetic force of bar
magnet. Now, slowly move the compass away from the magnet fill
the compass needle shows no effect on it.

iv) Repeat the activity at different positions to get a closed area
surrounding a magnet. The compass is not affected by the magnetic
force beyond the magnetic field

NS

72 Blooming Science & Environment Book 6

Demagnetisation

The process by which a magnet loses its magnetic properties is called demagnetisation.
The conditions are:
1. If a magnet is dropped frequently.
2. If a magnet is hammered.
3. If a magnet is heated.
4. If poles are not covered by keeper

Uses of Magnets

Magnets are very essential for us in our daily life. Ancient people also used magnets
to find out direction. Some important uses of magnets in modern days are as given
below.
1. They are used in factories for lifting heavy masses of iron and steel.
2. They are used in scientific devices such as electric motors, dynamos, telephones,
electric bells, speakers of radio and television sets, etc.
3. They are used to separate the magnetic substances such as iron, steel etc. from
the other non-magnetic substances such as brass, aluminum, copper, etc.
4. They are used in hospitals to remove tiny iron or steel particles from the eyes or
wounds of patients.
5. They are used for making magnetic compasses, magnetic toys and discs for the
recording of computer programmes.
6. They are used to separate the magnetic materials from the food stuffs.

Main Points to Remember

1. Magnet is a substance that attracts magnetic substances.
2. The magnet which is found on the earth is natural and the one which is made by
man is called artificial magnet.
3. Those substances which are attracted by magnet are called magnetic substances
and those which are not attracted by magnet are called non-magnetic substances.
4. Magnet always points to north and south direction.
5. Magnets have two poles north and south.
6. Like poles repel and unlike poles attract.
7. Magnetic poles always exist in pair.
8. Magnetic poles cannot be separated by breaking.
9. The region upto where magnet can attract another magnet and magnetic
substances is called magnetic field.
10. The process by which a magnet loses its magnetic power is called demagnetisation.

Blooming Science & Environment Book 6 73

PRO J ECTWORK

Suspend a bar magnet with a piece of thread. Bring one pin near to it. Magnet attracts
the pin. Again bring another pin to the attracted pin, it also gets attracted by it, bring
another pin. Also this pin gets attracted, why does it happen? Detach magnet from pin
and see whether other pins are attracted by first pin or not. Why does it happen? This
property is called magnetic induction.

Exercises

1. Fill in the blanks:

a. ………….. is a natural magnet.
b. Iron, nickel and …………. are the magnetic substances.
c. Magnet has two poles …………… and ……………..
d. Like poles ………….. and unlike poles ……………..
e. Magnetic poles always exist in ………………………

2. Write ‘T’ for true and ‘F’ for false statements:

a. A freely suspended magnet always points to north and south direction.
b. A magnet has minimum magnetic force at its poles.
c. A magnet attracts all substances.
d. Magnetic poles can be separated by breaking.
e. The attractive property of magnet is called magnetism.

3. Match the following:

Loadstone repel
Plastic non-magnetic substance
Horse-shoe magnet natural magnet
Iron magnetic substance
Unlike poles artificial magnet

4. Answer the following questions:
a. What is a magnet? Name a natural magnet.
b. List out the properties of a magnet.

74 Blooming Science & Environment Book 6

c. How do you find the poles of magnet?
d. How do you prove magnet has only two poles?
e. List out the types of magnet.
f. What is magnetic field?
i. Can we separate poles of a magnet?
j. How do you show that the magnetic strength is greater at the poles?
k. How do you identify whether a given rod is a magnet or not?
l. What is demagnetisation? List any four ways of demagnetisation.

Glossary

Magnet : material body with property of attraction. E.g. iron, cobalt,
etc.

Magnetic substance : substance that is attracted by magnet.

Non-magnetic substance : substance that is not attracted by magnet.

Magnetic compass : device used to point out direction.

Alloy : homogenous mixture of two or more metals.

Magnesia : a place near ancient Greece.

Navigator : Aperson who finds his position or the position of his aircraft, etc

Repulsion : The force by which objects tend to push each other away

Blooming Science & Environment Book 6 75

Chapter Electricity

8

Learning Outcome Estimated Periods: 2+1
On the completion of this unit, students will be able to:

 introduce electricity and identify sources of electricity.
 demonstrate and explain simple electric circuit.
 introduce and demonstrate conductors, insulators and semi-conductor.
 explain the uses of electricity.

Electricity

Electricity is our good servant as it helps us in heating, cooking, drying things,
telecommunication, transportation, etc. Electricity is a type of energy. It can be
converted easily into other forms by using electrical appliances. For example, an
electric lamp converts it into light energy, a heater converts it into heat energy and
a radio converts it into sound energy. It is very important source of energy for us.
Our modern lifestyle is heavily dependent on the numerous technological inventions
which cannot work without electricity.

Sources of electricity

Any device that produces electricity is the source of electricity. The most common
sources of electricity are:

i. Cell ii. Photo cell iii. Generators or dynamos

Out of above sources of electricity, only cell is described here.

Cell

Cell is the source of electricity. Group of + -+ -
cells is known as battery. Cell produces
small amount of electricity. Cells are Fig: Cell
portable i.e. they can be carried from one
place to another easily.

Cells are of two types: a. Simple cell b. Dry cell

Simple Cell

Simple cell is used to get small amount of current. It converts chemical energy into
electrical energy. It consists of vessel containing dilute sulphuric acid with copper

76 Blooming Science & Environment Book 6

plate and a zinc plate dipped in it. The copper plate is at +- Voltameter
higher potential. The zinc plate is at low potential. When Electrode
two plates are connected by conducting wire, the bulb Cu Zn
connected in it glows. Copper plate is called positive
terminal and zinc plate is the negative terminal. Dilute H2SO4

Dry Cell Fig: Simple Cell

Dry cell is portable. Dry cell also converts chemical energy
into the electrical energy. It consists of ammonium chloride in dry
form so it cannot spill and does not have to be kept upright. This
makes it easy to carry from one place to another.

A dry cell consists of a cylindrical zinc container with a paste of
ammonium chloride in its inner wall. A carbon rod surrounded by
a compressed mixture of carbon powder and manganese dioxide is
placed in a clothbag. This cloth bag is placed in the zinc container. Fig: Dry Cell
The open end of zinc container is sealed with wax or plastic to prevent the drying up
of the electrolyte. The zinc vessel acts as a negative terminal and the carbon rod with
brass cap acts as a positive terminal. Dry cells are used in torch-lights, radio, camera
etc. Simple cell and dry cell convert chemical energy into the electrical energy.

Photo Cell

Photo cells are sources of electricity; they convert light energy into electrical
energy. Photo cells are used in solar calculators and in other solar equipment. When
sunlight falls on the photo cells of a calculator, electricity is produced, enabling the
calculator to work. In remote areas photo cells are widely used nowadays.

Scan for practical experiment

Solar panel Photo cell Solar bulb

Dynamo visit: csp.codes/c6e13
Dynamo or generator is a device

which converts mechanical energy

into electrical energy. Hydro

electricity is also generated by using

generators. It produces large amount

of electricity. A dynamo used in

bicycle produces small amount of electricity. It was invented by Micheal Faraday. It

works by under the principle of electromagnetic induction.

Blooming Science & Environment Book 6 77

Electric Circuit bulb

We need electric current for various purposes. An

electric current requires path to flow. The path through

which electric current flows is referred as electric

circuit. A simplest circuit is a continuous path for the

flow of electric current. A circuit consists of wires,

electric loads like bulb and a source like a battery. cell key

Every electric circuit needs an electromotive force to drive the current through the

circuit, which is provided by the sources like cell or battery.

Closed Ciruit and Open Circuit

An electric circuit can be opened or closed using a switch. Look at the following
diagrams. In figure (a), the switch is open. The current is not flowing in the circuit
and hence the bulb is not glowing. Such circuit is called open circuit. Circuit is said
to be open when no current flows through the circuit.

(a) (b)

In figure (b) the switch is closed (i.e. on). The circuit is not broken and it is a complete
circuit. The current flows in a circuit only if it is closed. The conductor (wire) is used
to carry current from the source. So, if the wire is broken in the circuit, it cannot
carry the electric current. To get current for any purpose like running an electrical
device, a closed circuit has to be set up. Some circuits are very simple while others
are complicated. Circuit used in radio, transistor, television, computer is a closed
circuit. The circuit from which current flows and bulb glows is called closed circuit.
The circuit in which positive and negative terminals of a cell are directly connected
to each other is called short circuit. It causes accidents in buildings and factories. So
it is very harmful. It is mostly occurred in old wiring of old houses.

Conductors, Insulators and Semi-conductors
Some substances allow electricity to flow through them easily. The substances that
allow electricity to flow through them easily are called conductors. Copper, silver,
aluminum, brass, etc. are conductors.
The substances which do not allow the current to pass through them are called

78 Blooming Science & Environment Book 6

insulators. Glass, wood, plastic etc. are insulators.

Both conductors and insulators are important in handling electricity. Conductors are
used to pass the electric current whereas insulators are used to make outer covering
of those conductors. It protects the users from the electric shock.

The substances which can pass electricity partially are called semi-conductors.
Silicon and germanium are examples of semi-conductors.

Activity

To test a given material as conductor or insulator.

Materials required : Dry cell, one torch bulb, three pieces of wire each 25cm, cork
and coin.

Procedure : bulb switch

1. Make a circuit using one torch bulb, a cell and wire XY
leaving a gap between points X and Y as shown in the cell
following figure.

2. Connect each substance in turn in the gap X and Y.

3. Observe the bulb. If the bulb glows the substance is a conductor. If it does not
glow, the substance is an insulator.

4. Record your observation in the table.
Observation :

S.N Substance Does the bulb glow? Conductor or insulator
Conductor
1. Copper wire Yes Insulator

2. Wood No

3. Iron nail

4. Aluminum spoon

5. Paper

6. Plastic scale

7. Eraser

8. Pencil

9. Stick

10. Piece of cloth

Conclusion : The bulb glows when the conductors are connected in the gap of the
circuit. The bulb does not glow when the insulators are connected in the gap of the
circuit.

Blooming Science & Environment Book 6 79

Uses of Electricity

Electricity is an unavoidable helper in our life. It is used to operate appliances like
electric bulbs, radio, heater, television, fan, device of communication and materials
of entertainment etc. Imagine the condition of load shedding. A how difficult our life
was. Some of the uses of electricity are:

1. Light: Electricity is used to produce lights. We use filament bulb and
fluorescent lamps CFL and LED bulbs in our houses

2. Heat: Electric kettle is used to warm up water. We use electric iron to press
clothes in our daily life. Electric heater is used to cook food and warm up the
room. These appliances contain nichrome wire inside. Nichrome wire has a
high resistance.

When electric current flows through the nichrome wire, it becomes red hot and
emits heat and light. This heat is used to warm up water, cook food and press
clothes.

3. Electricity is used to run various electronic devices such as TV, radio, computer,
calculator, watch, transistor etc.

4. It is also used to run electric motor, electric bell, electric vehicles etc. Electric
motors are used in pump set, trolley bus, fan etc.

5. Modern light producing appliances and instruments cannot work without
electricity.

Main Points to Remember

1. Electricity is the energy possessed by electric current.

2. Any device that produces electricity is called source of electricity. There are
three major sources of electricity: cell, photo cell and dynamo or generator.

3. A cell is a device that converts chemical energy into electrical energy. There
are two types of cell: simple cell and dry cell.

4. Photo cell converts light energy into electrical energy.

5. Dynamo or generator is a device used to convert mechanical energy into
electrical energy.

6. The continuous conducting path through which an electric current flows is
called electric circuit.

7. An electric circuit consists of a source, conducting wires, switch and load.

8. There are two types of circuits they are open circuit and closed circuit.

80 Blooming Science & Environment Book 6

9. The substances that allow electricity to flow through them easily are called
conductors.

10. The substances that do not allow electricity to flow through them easily are
called non-conductors or insulators.

12. The circuit in which ‘positive’ and ‘negative’ terminals of a cell are directly
connected to each other is called short circuit.

PRO J ECTWORK

To make own cell by using cow dung.
i) Take some cow dung in a small plastic.
ii) Make a thin paste by mixing some water and stirring it.
iii) Take a copper plate and zinc plate and dip into the paste.
iv) Connect these two plates with the help of coducting wires and connect these
with a galvanometer.
v) The deflection in the galvanometer shows that electricity is produced and
flowing through conductor wires.

Galvanometer

Conductor wire

Copper plate Zinc plate

Paste of cow dung
Plastic vessel

Exercises

1. Full in the blanks.
a. Bulb glows in ......................... circuit.
b. Due to ......................... circuit, huge amount of current flows in the circuit.
c. A photo cell converts ......................... energy into......................... energy.
d. A drawing of an electrical circuit with standard symbols is called
.........................
e. The substance which allows the flow of electric current is .........................
f. The device which converts electrical energy into ......................... energy is

Blooming Science & Environment Book 6 81

the bulb.
g. ......................... is required to run the electrical devices.
h. Two or more cells combine to form a .........................
i. Dynamo converts ......................... energy to ......................... energy.
2. Make a tick (√) against true and a cross (×) against false statements.

a. Plastic and paper are conductors.
b. A short circuit is a useful circuit.
c. Photo cell works during day.
d. An electric bulb converts light energy into electrical energy.
e. Aluminum and copper are the examples of conductors.
f. Simple cell contains dilute nitric acid.
g. Electric current flows in a closed circuit.
h. Dynamo produces smaller amount of current than generator.
i. Insulators are not important in electricity.
3. Select the best alternative.

a. Which of the following is used for heating?

i. Copper wire ii. Nichrome wire

iii. Gold wire iv. Aluminum wire

b. Which one is used to produce maximum amount of electricity?

i. Photo cell ii. Simple cell

iii. Generator iv. Dry cell

c. Which one is conductor?

i. Plastic ii. Rubber

iii. Copper iv. Wood

d. The one which is not needed to complete the electric circuit?

i. Compass ii. Cell

iii. Bulb iv. Switch

4. Answer these questions.

a. Name any two devices that convert electrical energy into light energy.
b. Why are the conducting wires at homes covered with plastic?
c. What is an electric circuit? Classify it.
d. Write the symbol of (i) bulb (ii) a battery (iii) connecting wire (iv)

resistance.
e. What is source of electricity?
f. Define conductors and insulators with examples.
g. What is short circuit? It is harmful, why?
h. Define semi-conductors with examples.

82 Blooming Science & Environment Book 6

i. Why is electricity considered as our good friend?
j. How does closed circuit differ from short circuit?
k. List various uses of electricity in our daily life.
l. Describe a simple cell with diagram.
m. Draw an electrical circuit with an electrical cell, bulb and an OFF switch.
n. Draw and electric circuit containing a cell, wire, a switch and an electric

bulb using symbols.
o. Draw and label a diagram of dry cell.
5. Differentiate between.

a. Simple cell and photo cell
b. Closed circuit and open circuit
c. Conductors and non-conductors
d. Electric device and source of electricity

Glossary

device : tool

spin : turn round and round, rotate

spill : flow out from a container

twist : bend

appliance : electrical devices

sealed : packed with special cover that is broken while opening,

sake benefit, support

irreversible : impossible to reverse or undo

CFL : compact flourescent lamp

LED : light emitting diode

Blooming Science & Environment Book 6 83

Chapter Matter

9

Learning Outcome

On the completion of this unit, students will be able to: Estimated Periods: 8+2

 define matter and tell the physical properties of matter.

 explain different states of matter and their interrelationship.

 demonstrate change of states of matter and tell their uses.

 define elements, compounds and mixtures and classify them.

Matter

There are many substances around us. These substances have weight and occupy
space. Chalk, glass, plastic, iron, paper, wood, salt, etc are matters. Our body also has
many different kinds of matter.

The world around us is filled with numerous materials. Matter has mass and occupies
space. They may be in the form of solid, liquid or gas. They may be living or
non-living. They may be pure or impure substances. They may be natural or artificial.

A stone is solid, occupies space and has mass. The gas inside the balloon occupies
space and has mass.

Any substance, in which no other substances are mixed, is called a pure substance. If
a substance is mixed with other substances, it is called an impure substance.

Some of these are book, pen, chair, wood, glass, iron, soda, salt, alum, brick, sugar,
bicycle, rope, bag, mirror, table, cotton, water, kerosene, oil, butter, ghee, plastic,
rubber, etc. All the substances around us are made up of different materials. They can
be recognized because of certain characteristics they have. But, all of them have two
common properties. They are; a) they have mass and b) they occupy space.

Matter is anything that occupies space and has mass.

The total quantity of matter present in a body is its mass. The mass of an object
depends upon the number of molecules present in it and average mass of the
molecules. Generally the heavier objects have more mass and lighter objects have
less mass.

84 Blooming Science & Environment Book 6

Similary a matter occupies the space. the total space occupied by a body is called its
volume. In general, the bigger objects have more volumme and smaller objects have
less volume.

We can find the mass of an objects by weighing it in a beam balance whereas volume
of objects is found by different ways. i.e. liquid displacement method (irregular
objects) and using particulart algebraic formulae (regular object)

Fig : Measuring of mass Fig : Air has weight h

b
l

Fig : v= l×b×h

Scan for practical experiment

visit: csp.codes/c6e14

Fig : Volume of water Fig : Liquid displacement method

Properties of Matter

These matters have their own properties. The solubility of substance, transparency,
brittleness, combustibility, colour, odour, etc., are some of the properties of these
matter. Here, we will be able to find out these properties with the help of various
activities.

1. Solubility Spoon
Salt Glass rod
Collect some substances like sand, salt, sugar,
alum, etc. from surroundings. Take a half Glass
glass of water. Add a sample of each collected Salt solution
substance in water and stir with a glass
rod or spoon for about five minutes. The substance
that dissolves in the water breaks into smaller

Blooming Science & Environment Book 6 85

particles and begins dissolving in water. Some Spoon
of the substances dissolve readily in hot water

than in cold water. So, it is advisable to use Sand Glass rod
hot water to perform this activity. We find

that particles of the substances like soda, salt,

alum and sugar slowly disappear and these

substances are said to be dissolved in the Glass
water. So these substances are called soluble

substances. Thus, those substances which

dissolve in water are called soluble substances. Sand water
Again, take a half glass of water, add a spoonful mixture

of collected substance like sand, kerosene, etc. in it and stir. The particles of sand

remain at the bottom of the glass and suspended in the water. But the kerosene is

found on the surface of the water. So, these substances are called insoluble substances.

Substances like salt, alum and sugar dissolve in water but the substances like grease
and oil do not dissolve in the same liquid. Only particular substances dissolve in the
particular liquid.

2. Transparency Torch

Take a book, a wooden board, a thin plastic Wooden board
sheet and a glass. Hold each of them in front of a Torch
glowing torch turn-by-turn at dark. We are unable
to see the light of torch when we hold the wooden
board or a book. If the white plastic sheet or glass
is put in front of torchlight, we can see light. Now,
the substances like wooden board and book are
opaque substances while the thin white plastic
sheet and glass are called transparent substances.

We can find out the transparency of liquid also by Glass
putting it in a test tube.

3. Brittleness

Take a substance such as a piece of glass on a
hard surface of a stone or iron plate. Hit it with
the hammer. It breaks into small pieces. If a piece
of plastic sheet is hit, it does not break into pieces,
rather the plastic sheet gets depressed where it is
hit. The substances like glass, brick, etc. break into
pieces when hit are called brittle.

86 Blooming Science & Environment Book 6

4. Combustibility

Hold a spoonful of sugar and pieces of iron
near the flame of candle with the help of long
forceps turn by turn and observe what happens.
We will notice that the sugar starts burning, but
a piece of iron does not burn. The substances
like wood, paper, kerosene, sugar, oil, etc. which
burn easily are called combustible substances.
The substances like piece of brick, iron, etc.
which do not burn are called non-combustible
substances.

5. Colour

Usually most of the substances have their own colour such as white, black, brown,
green, pink, red, orange, yellow, etc. The substances can be recognized by their
typical colour. For example, the colour of copper sulphate is dark blue. The colour of
a solid substance can be said by observing them. While the colour of liquid substance
can be distinguished easily after taking it in a test tube.

6. Odour

Most of the substances may have smell. Nose is a sense organ
that has numerous nerve cells. The odour from the substance is
carried to the brain through the olfactory nerves and the brain
determines the type of smell. Smell is described as a character
of sense organ or nose.

States of Matter

Matter exists in three states. These states are solid, liquid and gas.

Solid

Solid substances have their own shape and fixed volume. Marbles, coin, glass are
solid matter.

Liquid

Liquid matter has no fixed shape but has fixed volume. It takes the shape of the
container in which it is placed. Water, petrol, kerosene are liquid matters.

Gas

Gas has no fixed shape and volume. It also takes the shape of the container in which
it is placed. But the gas can be compressed. Air is gas matter.

Solid and liquid have fixed volume so they cannot be compressed but gas can be
compressed.

Blooming Science & Environment Book 6 87

Differences between solid, liquid and gas

Solid Liquid Gas
They have fixed shape They do not have fixed They do not have fixed
shape shape.
They have fixed volume. They do not have fixed
They cannot flow. They have fixed volume. volume.
They cannot be They can blow
compressed They can flow.
They cannot be They can be compressed.
Change of State compressed
Solid

There are some substances that can be changed from one Sublimation FSuosliiodnification
state to another. This change of state takes place only
under certain conditions. During their change of state, Gas Vaporisation Liquid
heat plays a very important role. Some substances give
heat while other need heat during their change of state. Condensation
Change of state

The molecules in a solid substance are in compact form and the space between them
is very less. The space between the molecules is known as intermolecular space.
When solid substance is heated, the intermolecular space increases and changes into
liquid. Liquid on heating changes into gaseous state.

Fusion or Melting

The process of changing solid into liquid on heating is called melting.

Solid Heat Liquid

Vapourization
The process of changing liquid into gas on heating is called vapourization.

Liquid Heat Gas

Condensation
The process of changing gas into liquid on cooling is called condensation.

Liquid cooling solid

88 Blooming Science & Environment Book 6

Sublimation

The process of changing a solid into vapour directly without changing into liquid on
heating is called sublimation.

Solid Heat Gas

Types of Matter

There are different types of matter in nature. Generally the matters are of twp types;
pure and impure. The pure substances are called elements and compounds whereas
impure substances, are called mixtures.

Matter

Pure substances Mixtures

Elements Compounds Homogenous Heterogenous

Element and Compound

Pure substances and the mixture are made from elements. Just as the walls of the
houses are made from the bricks, the substances are also made from elements. The
elements cannot be divided into other simple elements. For examples, hydrogen is an
element. We cannot get other element from hydrogen.

An element is the simplest substance, which cannot be broken down into simpler
substances by any physical and chemical means. Similarly, element cannot be
formed from other substances. Oxygen, nitrogen, iron, sodium, calcium etc are
some examples of elements. Elements are pure substances because they cannot be
broken down into simpler substances by any physical and chemical means. There
are 118 elements discovered so far. Among them 92 are natural and remaining are
synthesized in laboratory. The lightest element known is hydrogen.

A pure substance formed by chemical combination of two or more elements in fixed
proportion by weight is called a compound. These compounds are made up of more
than one element. There are many compounds in nature which are formed by the
elements existing in nature. Some examples of compound are water, carbondioxide,
soap, sugar, salt, etc.
a) Water is made by chemical combination of two parts of hydrogen and one part
of oxygen.
b) Common salt (Edible salt) is made by one part of sodium and one part of
chlorine
c) Carbon dioxide is made by one part of carbon and two parts of oxygen.

Blooming Science & Environment Book 6 89

Misture

When two or more substances are kept together, a mass of substances is formed in
which the components do not react with each other. When such new substances is
formed it contains the properties of each component. For example, when we mix salt
and sand, they do not lose their properties. They remain together but do not undergo
any chemical change. We use many such substances in our daily life.

A mass formed by mixing two or more substances is called a mixture.

The mixing substances of mixture are called components. In a mixture, the
components can be mixed in any proportion.

Main Points to Remember

1. In the surroundings we find different substances. They are made of different
materials.

2. The substances found in our surroundings have their own properties.

3. Solubility, transparency, fragility, flammability, etc. are some of the properties
of the substances.

4. The substances have their own colour and odour.

5. The substances can be classified on the basis of their properties. Grouping of
substances on the basis of their properties is known as classification.

6. Matter has mass and volume.

7. Matter exists in three states: solid, liquid and gas.

8. Solids have fixed shape and volume. Liquids have fixed volume but they do not
have fixed shape or size. Gases have no fixed shape and volume but they have
mass and weight.

9. An element is a distinct kind of matter which can neither be broken down into
simpler substances nor be made from simpler substance by simple chemical
means.

10. Compound is formed by the combination of two or more elements in fixed
proportion. They are formed due to chemical reaction.

11. Conversion of solid into liquid is known as fusion or melting. For example,
when ice is heated, immediately it begins to change into liquid.

12. Conversion of liquid to gas is known as vaporization. For example, when water
is heated, it changes into vapour, called steam.

13. Conversion of gas to liquid is known as condensation or qualification. For
example, if water-steam is cooled, immediately we can see the water droplets.

14. Conversion of liquid to solid is known as solidification. When temperature
of water is below 0oC, it will change into ice. Ice is the solid form of water.
The process of converting solid into gas by heating is known as sublimation.
Example; camphor, iodine, etc.

15. Elements and components are pure forms of matter where as mixtures are
impure forms of matter.

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PRO J ECTWORK

Collect some substances from your surroundings like edible salt, sugar. ghee, turmeric
power, fitkiri, sand, edible, soda, washing power, soil, kerosene etc. Mix these in water
turn by turn and stir to observe whether these are soluble or insoluble in water. Make
a table showing soluble and insoluble substances in water.

Exercises

1. Fill in the blanks with suitable words.

a. A matter has .............................. and ..............................

b. The .............................. of matter present in a body is called its mass.

c. The substances like glass, water and white plastic sheet are ......................

d. The gases do not have fixed .............................. and ..............................

e. A .............................. is made by chemical combination of two or more
elements.
2. Choose the best alternative among the given.

a. Which of the following elements exist in liquid state at normal temperature?

i) oxygen ii) Nitrogen

iii) Iron iv) Mercury

b. Which of the following is not soluble in water?

i) Milk ii) Alcohol

iii) Kerosene in) Water colour

c. How many elements have been discovered till now?

i) 92 ii) 118

iii) 109 iv) 115

d. Sublimation process occurs in ..............................

i) Camphor ii) Salt

iii) Alum iv) Sugar

e. What is the process of changing solid into gas called?

i) Vapourization ii) Evaporation

iii) Sublimation iv) Fusion

3. Answer the following questions:

a. What is matter ? What properties must be there to be a matter?
b.
Give any two examples of each of the matter with following properties:

i) Transparent ii) Opaque

iii) Brittle iv) Combustible

v) Non-combustible vi) having odour

Blooming Science & Environment Book 6 91

c. Whay does a solid change into liquid on heating? Expalin in brief.

d. What is sublimation? Write down any two examples of matter that
sublimate.

e. Why is water called a compound?
4. Define the following:

a. Element b. Compound

c. Mixture d. Condensation

f. Fusion

5. Write down the main points of different between:

a. Element and compound.
b. Compound and mixture.
c. Melting and freezing point.
d. Solid and liquid.

e. Ecaporation and Condensation.

Glossary

Matter : a thing that occupies shape and has mass.
Element
: pure form of matter made up of one type of small
Compound components.

Molecule : pure substance made up of two or more elements by
chemical combination.
Atom
Combustible : tiny components present in matter that can exist
Compressible independently.
Odour
Transparent : smallest possible unit of an element.

: capable of catching fire

: that can be squeezed into a small space.

: smell

: something through which light passes.

92 Blooming Science & Environment Book 6

10Chapter Mixture

Learning Outcome

On the completion of this unit, students will be able to: Estimated Periods:8 +1

 introduce mixture and explain homogeneous and heterogeneous mixture.
 tell uses of different types of mixtures.
 explain and demonstrate some simple methods to separate the components of

mixture(sedimentation and decantation, filtration, winnowing, seiving,
evaporation and magnetic separation.

Introduction

We find various objects around us. These objects are characterized by their own
sizes and forms. Due to this, they can be distinguished from their surroundings. Such
objects are called bodies. For example, book, copy, newspaper, etc. are made of
paper. Chair, table, window, door, etc. are made of wood. Bag, bucket, raincoat, etc.
are made of plastics.

Paper, wood, plastic, soil, stone, iron, water, oil, etc. are called substances. Everything
is made up of substance. A substance has definite properties and composition.

Thus, substance is one that is made up of only one kind of molecules and has definite
composition and properties. It has fixed melting point, boiling point and density.
Water and kerosene are two different substances. They have their own properties.
Some properties of them may be similar or dissimilar. For example, both are found
in liquid state and are transparent. Water can dissolve more substances but kerosene
cannot.

Pure and Impure Substance

A pure substance is that substance which is made up of only one kind of molecules
and has fixed composition and properties, e.g. pure water. It is very difficult to get
pure water because some air and other soluble matters are found dissolved in it.

Impure substance is that which is made up of two or more kinds of molecules and has
no definite composition and properties. The impure substance is called mixture, eg.
salt in water, sand in water, husk in rice, soda water, etc.

Blooming Science & Environment Book 6 93

Mixture

Activity

Take four glasses and name A, B, C and D. Take the glass A and fill half of it with
water and put a spoonful of salt into it. In the glass B, put one spoonful of salt and one
spoonful of sand. In the glass C, put one spoonful of salt and one spoonful of sugar. In
the glass D, fill half of it with water and put one spoonful each of salt and sugar into
it. Stir all the glasses with a glass rod properly. Now different substances are mixed
together in the glasses and the mass obtained in each glass is called mixture.

A BC D

(a) Salt in water (b) Salt and sand (c) Salt and sugar (d) Water, salt and sugar

Therefore, the mass of substances obtained on mixing two or more substances in any
proportion is called a mixture. The substances which take part in the formation of
mixtures are called components of mixture. The properties of each of the components in
a mixture remain unchanged. The components of a mixture may be present in any of the
three states, i.e. solid, liquid or gas.

Depending upon the nature of the components of the mixture, there are two types of
mixtures. They are homogeneous mixture and heterogeneous mixture.

In glass A and D, the particles of sugar, salt and water are very small and not seen by
our naked eyes. Water is liquid and on stirring it mixes with salt and sugar. Thus the
components in glass A and glass D form homogeneous mixture. In glass B and C, the
particles are bigger and can be seen by our naked eyes. Thus components in glass B
and C form heterogeneous mixture.

Result of the above activities is given in the table below:

Components Types of Mixture

Glass A Water and salt Homogeneous

Glass B Sand and salt Heterogeneous

Glass C Salt and sugar Heterogeneous

Glass D Water, sugar and salt Homogeneous

1. Homogeneous Mixture

Take half of a beaker of water. Put one teaspoonful of salt into it. Stir it gently with a
glass rod. The salt dissolves in water. The salt particles are completely mixed in the

94 Blooming Science & Environment Book 6

water so that the salt particles cannot be seen with naked eyes. Thus obtained mixture
of salt and water is called homogeneous mixture.

Therefore, the homogeneous mixture is also mass of two different substances in
which component particles are equally distributed and cannot be seen through naked
eyes.

The homogeneous mixture is also called solution. Some other
examples of this mixture are sugar solution, alcohol and water,
soda water, etc.

Solution

Solution is a homogeneous mixture which is formed by Salt solution
mixing suitable solid in liquid or liquid in liquid. The size of
the particles of the components in solution is very small, it
is also defined as the homogeneous mixture of solvent and
solute, for example salt and water form salt solution. In this
example salt is a solute as it gets dissolved in water while
water is a solvent as it dissolves the solute.

Solution = Solute + solvent

2. Heterogeneous Mixture

Take half of a beaker of water. Put two spoonful of sand
into it. Stir it properly with a glass rod. The sand particles
are dispersed throughout the water. In the sand water, the
sand particles can be seen with our naked eyes because the
particles are larger enough to see them. The obtained mixture
of the sand and water is called heterogeneous mixture.

Heterogeneous mixture is a mass of different substances in Sand water
which the particles of components of the mixture are not
equally distributed and can be seen with naked eyes. Some
common examples of this mixture are muddy water, smoke,
rice coats in rice, etc.

Differences between Homogeneous and Heterogeneous mixture

Homogeneous mixture Homogeneous mixture

1. It is the type of mixture in which 1. It is the type of mixture in which

components of mixture are uniformly components of mixture are not

distributed. uniformly distributed.

2. Components of the mixture cannot 2. Components of mixture can be seen

be seen with naked eyes. Eg. Sugar with naked eyes. Eg. Muddy water,

solution, salt solution etc. mixture of rice and husk etc.

Blooming Science & Environment Book 6 95

Methods of Separating Mixture

Mixture contains various types of components. Separation of the components of a
mixture is done for the following purposes:

a. To remove undesirable components such as stone from wheat and rice etc.

b. To remove a harmful components such as insects from grains.

c. To obtain a useful component such as separating butter from milk and sugar from
sugarcane.

In order to separate components of mixture, some characteristic property of one
component that is different from others is used. For example, in a mixture of sulphur
and iron filings, magnet is used to separate the iron filings from the mixture. Magnet
will not attract the sulphur. Similarly to separate a mixture of common salt and sand,
we use the property of common salt. That is, common salt is soluble in water whereas
sand is not. Thus to separate the component of mixture, the common physical methods
of separation are described below:

1. Sieving

Sieving is the method to separate particles of different Sieving
sizes. Undesirable particles can be separated from
grains by this method. The size of holes in the sieves
depends upon the size of particles. The sieve is
basically a wire mesh fixed tightly in a frame.

Activity

1. Take mixture of flour and barn.

2. Take a sieve.

3. Put the above mixture on the sieve and move it.
Observation:

The fine particles of flour easily pass through the holes of the wire mesh. The barn
grains being larger remain on the wire mesh. The flour is separated from the barn
by sieving.

By using a large number of sieves each with a wire mesh of different size, it becomes
possible to separate a mixture of solids of different sizes.

2. Winnowing

Winnowing is the process of separating light solid Winnowing
particles from heavier solids. Wheat or rice grains are

separated from the husk by winnowing. Wheat grains and

husk are different in weights, husk is lighter than wheat.

When the mixture is allowed to fall down from a height,

96 Blooming Science & Environment Book 6

the wind carries the lighter husk some distance away and the heavy wheat
grains fall vertically down to the ground. Hence, two different heaps of light
and heavy substances are formed.
3. Filtration
When one component of a mixture is soluble in water and other component
is insoluble in water, the soluble component gets dissolved and insoluble one
is separated by filtering the solution. The process of separating soluble or
insoluble solid particles from the mixtures by passing it through filter paper is
called filteration.

Residue

Filtration

filtrate

How can we separate the sand and water from the mixture of sand and water? What
is the difference between the features of sand and water? Sand cannot pass through
the tiny pores through which water can pass. Do the following experiments and see
the result. Separate the mixture of sand and water using a fine cloth or a filter paper.

Fit the filter paper on the cone. Pour the mixture of sand and water into it. Then the
sand particles remain on the filter paper called residue and the water passes through
the filter paper called filtrate.

4. Sedimentation and Decantation

This method is used to separate a heterogeneous mixture of solid and liquid.
The mixture is allowed to settle down for sometime. Solid particles will settle
at the bottom of the container. This is called sedimentation. After this, the
solution is poured to the another vessel. This separates the liquid from solids.
This process is known as decantation.

Scan for practical experiment

Decanation visit: csp.codes/c6e15

Blooming Science & Environment Book 6 97

5. Evaporation

This method is used to separate a homogeneous mixture Evaporation
of solid and liquid. Homogeneous mixture is placed in
a evaporating dish and heated. Solvent vaporizes and
the solute remains in disc. Mixture of salt and water can
be separated by this method. The liquid in the mixture
is evaporated off into the air and is not recovered.

6. Magnetic separation

Magnetic separation is the process of separating
magnetic substances with the help of the magnet. wood dust
This method is used to separate magnetic Iron filings
materials from non-magnetic materials. It is used
Magnet

to separate iron filing from wood dust. It can also

be used to separate magnetic pieces from the Iron+wood dust
garbages.

7. Sublimation

The process in which a solid changes directly into vapour when it is heated is
called sublimation.

The solid obtained by cooling down the vapour, is known as the sublimate. Iodine,
camphor, naphthalene and ammonium chloride are substances that produce a
sublimate when cooling their gaseous versions.

Activity

To separate a mixture of two solids by sublimation process.

Materials required: Wire gauze, burner, a dish, a funnel, cotton,
iodine and sand.

Procedure:

• Take a mixture of sand and iodine powder.

• Mix it well and put the mixture in a dish. Fig: Sublimation
• Invert a glass funnel over it.

• Plug the top of the tunnel with wet cotton wool.

• Heat the mixture gently till white fumes are seen rising over the moisture.

What happens?

A dark purple, fine and shiny powder-like substance collects inside the funnel. After
it becomes cool, scrape the inner wall of the funnel to collect the condensed iodine
powder. The sand is left behind in the dish.

98 Blooming Science & Environment Book 6

Main Points to Remember

1. A substance is said to be pure if it has no any substance mixed into it.

2. A substance is said to be impure, if it has two or more than two substances
mixed in it.

3. A mixture is a substance which consists of two or more than two substances.

4. In homogeneous mixture, the particles of the component can not be seen with
naked eyes.

5. In heterogeneous mixture, the particles of the component can be seen with
naked eyes.

6. Common method of separation of mixtures are sieving, winnowing, filtration,
sedimentation and decantation, evaporation, distillation and magnetic
separation.

7. Sieving is the method to separate the particles of the different sizes.
8. Winnowing is the process of separating light solid particles from heavier solid.
9. Filtration is the process in which insoluble substances are separated from the

mixture with the help of filter paper.
10. Sedimentation and decantation are applied to separate the heterogeneous

mixture of solid and liquid.
11. Evaporation is the process of separating the liquid of a mixture by converting

it into vapour.
12. Sublimation is the process of separating sublimate from a mixture.
13. Magnetic separation is the process of separating magnetic substances with the

help of the magnet.

PRO J ECTWORK

Make a list of some mixtures used at your home and explain a process to separate
components from any one mixture that is used at your home or you have seen.

Exercises

1. Select the best alternative:

a. A mixture of sand and salt can be separated by using:
i. Dissolving in water and filtering the mixture.
ii. Magnetic separation
iii. Winnowing

Blooming Science & Environment Book 6 99

b. A mixture of sand and iron fillings can be separated by:

i. Magnetic method ii. Sieving iii. Distillation

c. Which of the following is the homogeneous mixture?

d. i. Sugar and flour ii. Water and salt iii. Muddy water

How can you separate wheat from husk?

i. By winnowing ii. By sedimentation iii. By magnetic method

e. Sublimation is a process which can be followed by

i. Comphor ii. Water iii. Salt

2. State whether the following statements are ‘True’ or ‘False’

a. A pure substance is a mixture.
b. The solid substance left after filtration is called residue.

c. Distillation is the process of evaporation followed by condensation.

d. By decantation one can remove insoluble impurities.
e. Solution is homogeneous mixture of solute and solvent.
3. Answer the following questions:

a. What is a mixture? Classify it.
b. Define pure and impure substances with examples.

c. Differentiate between homogeneous and heterogeneous mixture.

d. Name two methods of separating various components from a heterogeneous
mixture.

e. How will you separate pure water from a solution of salt and water?

f. A mixture of iron filing and sulfur powder is given. How will you separate
them from the mixture?

g. What is winnowing?

h. What is sieving? Mention the use of sieving in our everyday life.
i. What is filtration?
j. Define evaporation. Mention its uses.
4. Which of the following two substances are mixed together to form
homogeneous and heterogeneous mixture?

i. Water ii. Kerosene ii. Oil
iv. Sugar
iv. Sand v. Salt

5. Define the following:

a. sedimentation b. decantation

c. impure substance d. magnetic separation

e. suspension f. colloids
g. solution h. sublimation

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