Shubharambha Science & Env 6 -2077 press re

Approved by Government of Nepal, Ministry of Education, Curriculum
Development Center (CDC).

Blooming

SCIENCE
&

ENVIRONMENT

Book

6

Authors
Raj Kumar Dhakal
Purushottam Devkota

Shubharambha Publication Pvt. Ltd.

Kathmandu, Nepal

Published by:

Shubharambha Publication Pvt. Ltd.

Kathmandu, Nepal
URL: www.shubharambhapublication.com
E-mail: [email protected]

www.facebook.com/shubharambhapublication

Blooming Science and Environment Book-6

Authors : Raj Kumar Dhakal

Purushottam Devkota

Video Content : Laxmi Nand Dhakal

Layout Design : Ram Malakar

Language Editor : Krishna Prasad Regmi

Copyright © : Publisher

Edition : 2077

© : Publisher

No part of this book may be reproduced or transmitted by means (electronic, photocopying,

recording or otherwise) without prior written permission from the publisher. Any breach

of this condition will entail legal action and prosecution.

What if books could talk to you?

That was the question we asked ourselves.
We believe education should be interactive and enjoyable. We’re living in the IT era
and education is the only sector lagging behind when it comes to integrating new
technologies inside and outside the classroom.
That’s why we teamed with Freelancer Company Pvt. Ltd. and Mr. Laxmi Nand Dhakal
to create an immersive experience to redefine how we learn. With Laxmi Sir’s brains
and the technological excellence of Freelancer Company, we’ve created in-depth video
materials that aid the topics covered in this textbook.
We hope to make learning fun again! With a few clicks, you will be able to learn more

about any topic in this book via practical experiment videos.

Freelancer Company Pvt. Ltd. Laxmi Nand Dhakal
IT Company in Kathmandu Scientist, Teacher, HOD (R&D Dept)
https://creativescienceproject.com
https://freelancercompany.com.np

Freelancer Company took this project Laxmi Nand Dhakal is the creative force
from concept and made it into reality with who made this project possible.
their technical expertise.
His 20+ years of teaching experience along
They handled everything from scripting, with his dedication to the craft of Science
camera work, audio recording, video has added immense value to this project.
editing, website design & development,
QR code generation to the overall We’re proud to have such a talented
management of the project. individual in our team.

S can & Enjoy!

Thank you.

Dinesh Adhikari Shubharambha Publication Pvt. Ltd.

Academic Director Kathmandu, Nepal



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Preface

The series ‘Blooming Science and Environment’ has been brought out as an
indispensable resource for school level students and has intended to provide concise
and comprehensible explanation of key concepts, facts and principles across science
disciplines. Organized around the National Science curriculum prescribed by
Curriculum Development Centre, Sanothimi, Bhaktapur, the series presents solid
overviews of the most commonly encountered school science topics with sound
academic and fun activities.

The clear and accessible definitions, concise language, helpful diagrams and
illustrations and other science activities offered in this series will nonetheless help
teachers understand science concepts to the degree to which they can develop
rich and exciting inquiry approaches to exploring these concepts with students in
the classroom. As the series has been brought out considering the age and other
psychological factors of children, the learning materials in this series appeal to the
sense of the children and they are related to the world of young learners. Activities
with varieties of questions in this series are meant to assess and evaluate the level of
students’ inquisitiveness.

As each unit begins with its objectives and estimated teaching periods which help
teachers to complete the course in time. Moreover, each lesson in the series ends with
Let's Learn, Points to Remember and Relevant Exercises; these sections are meant
to provide good review to students and enhance their ability to solve the exercise
questions. Each lesson has Multiple Choices Questions and Project Work that are
meant to arouse more creativity and interest in the students for better understanding
and adjustment with their scientific world.

Our special thanks goes to Mr. Keshav Lamichane for his support and encouragement
to complete this text book successfully.

We are grateful to teachers, students and principals who shared their valuable
suggestions in materializing this series. Any constructive suggestions and
recommendations for the betterment of this series will be highly acknowledged.

AUTHORS

Contents

Physics
1. Measurement ................................................................................... 7
2. Force ..................................................................................................17
3. Simple Machine ................................................................................25
4. Heat ...................................................................................................34
5. Light...................................................................................................47
6. Sound .................................................................................................57
7. Magnetism..........................................................................................67
8. Electricity ..........................................................................................76
Chemistry
9. Matter ..............................................................................................84
10. Mixture .............................................................................................93
11. Air.....................................................................................................102
12. Metals and Non-Metals....................................................................110
13. Some useful Chemicals ...................................................................117
Biology
14. Living Organism ............................................................................122
a. Plant Life
b. Animal Life
c. Invertebrates
15. Cells ................................................................................................151
16. Life Process in Plants ............................................................ ........161
a. Parts of Plant
b. Plants Physiology
Astronomy & Geology
17. Structure of Earth ...........................................................................178
18. Weather and Climate.......................................................................186
19. The Earth and Space.......................................................................194
Environment Science
20. Environment and Its Balance..........................................................204
21. Environment Degradation and Its Conservation ............................217
22. Environment and Sustainable Development ..................................231
List of Video Experiments .............................................................244

1Chapter Measurement

Learning Outcome Estimated Periods: 5+1

On the completion of this unit, students will be able to:

 define measurement & tell its importance in daily life.
 introduce unit and standard unit
 describe various systems of measurement.
 measure physical quantities like mass, length, time, volume etc.
 identify and use some simple tools of measurement.

Measurement plays an important role to make our life comfortable and without it t
he general life of people is uncomfortable. When we go to the shop to buy 1
Kilogram of sugar, the salesman weighs it by using a physical balance. If he gives
1 Kilogram sugar by estimation without weighing, it will not be accurate. It may be
more or less than the amount of sugar we want.

Estimation is rough in accurate idea of measurement about the quantities like mass,
length and time. In order to take accurate measurement of a physical quantity we
use standard quantity.

The comparison of an unknown quantity with a known quantity is called measurement.

We use different methods and devices to measure substances. We use a scale to
measure length, a beam balance with standard weights to measure mass and a watch
to measure time. So length, mass and time are physical quantities.

The quantities which can be measured easily are called physical quantities.

Measuring Tape Beam balance Watch

Unit

When we buy two kilograms of rice, the shopkeeper uses two ‘one kilogram’ weights
for measurement.

So, to measure two kilogram mass, we have to choose a reference standard mass,
one kilogram. Two kg is double of one kg. Similarly metre and second are reference
units of length and time respectively.

Blooming Science & Environment Book 6 7

A reference standard quantity with respect to which we measure other quantities is
called a unit. It is defined as the fixed quantity used as standard reference to measure
the quantities of same kind. For eg: metre, centimetre are used to measure length and
kilogram, gram, etc are used to measure mass.

If we use our palm to measure the length of our table or bench in the class, it is
found different for different pupil. Palm is a local and non-standard unit of
measurement of length. As the size of the palms varies from person to person, it is
not accurate unit for the measurement. There are other many local units of
measurement used in our country. They are haath, mana, dharni, pathi etc. to measure
length, volume and mass respectively.

Importance of Measurement
1. Measurement is essential in selling and buying goods.
2. It is essential in performing scientific experiments to establish truth about a
physical phenomenon.
3. It is required for global understanding of the quantity of a substance.
4. It is essential in performing different scientific experiments.
5. Measurement of the medicine is a must in the treatment of diseases.

Nowadays standard unit of measurement like metre, kilogram, second, etc are widely
used to measure length, mass, time respectively. They are independent units and are
called basic units.

The unit of measurement which is used by majority of people all over the world is

known a basic unit or standard unit. Scan for practical experiment

There are two types of units. They are:
i) Fundamental Units
ii) Derived Units

Fundamental Unit visit: csp.codes/c6e01

There are some units used in our day to day life which are independent of any other

units. For example the unit of length is ‘metre’ cannot be used as a unit of mass. The

units of mass(kg), length(m) and time(s) are fundamental units.

The units of measurement which are independent of any other units
are called fundamental units.

Derived Units

There are so many units in our daily life which can be derived from

the basic units of mass length and time. The units of area, volume,

velocity, acceleration, force etc are derived units. spring balance

8 Blooming Science & Environment Book 6

The units which are derived from two or more of the fundamental units are called
derived units.

The unit of velocity is meter per second (m/s) which is obtained from metre (length)
and second (time), so it is derived unit.

Differences between Fundamental and Derived units

S.N. Fundamental Units S.N. Derived Units

1. These are the units of 1. These are the units of derived

fundamental quantities. quantities.

2. These units are independent of 2. These units are obtained from one
each other. or more fundamental units. These

Examples: metre, kilogram, depend upon each other.

second, ampere, Kelvin, mole Examples: Newton, joule, Watt,

and candela. Pascal etc.

Physical quantities can be measured by using various systems of units. The main
systems are described below.

MKS System

If length is measured in metre, mass is measured in kilogram and time is measured in second,
it is called MKS System. It is also called Metric System of units.

CGS System

The system of measurement in which length is measured in centimetre, mass is measured
in gram and time is measured in second is known as CGS system. It is also called French
system of units.

FPS system

If length is measured in foot, mass in pound and time in second, it is called FPS system.
It is British system of units to measure physical quantities.

SI system

The improved and extended version of MKS system of units is SI system. This system
includes MKS system as well as units of heat, light, electricity, temperature,etc.
‘The Eleventh’ general convention on weights and measurement introduced this

system in 1960 AD in france.

The SI unit of fundamental quantities are given below:

Length - metre (m) Current - Ampere (A)

Mass - Kilogram (Kg) Amount of substance - Mole (Mol)

Time - Second (s) Luminous intensity (Brightness of light) - Candela (cd)

Temperature - Kelvin (K)

Blooming Science & Environment Book 6 9

Measurement of Length

The distance between any two points is called as length. SI unit of length is metre.
The length of a bench, height of a tower, length of table etc are measured in meter.
If you want to measure length of your school belt, which unit will you use? Will
you use meter? No, it is because you need smaller unit to measure it. We measure
such things in smaller units such as centimetre and millimetre. These units are sub-
multiples of meter.

Measuring tape, meter scale and ruler are some of the common measuring devices.
Our instrument box contains a 15 cm ruler. A measuring tape is easy to handle
because it can be rolled up after its use.

All measuring instruments such as meter scales and measuring tapes are accurate copies
of the standard meter which is accepted all over the world. Some of the instruments used
to measure length are given below in the diagrams.

Meter rod Measuring tape Measuring tape 15 cm long
(small) (big) (ruler) scale

Activity 1

Collect different types of scales. Draw the diagrams and mention their uses

Name of the Scale Uses
15 cm long scale of geometry box.
1 metre long iron meter (cloth shop)
2 metre long iron tape (carpentry)

1/2 metre long cloth or plastic tape

150 cm long cloth or plastic tape (tailoring)
C. onclusion:

According to the shape the scales are also given various names. To measure small
length scale is used and tape is used to measure long distance. Long tape is coiled
to carry easily. A long strong metal rod is used to measure cloth. The scale in the
geometry box is made up of strong plastic. It is used to draw straight lines.

For measuring the small distances or lengths, the metre is considered too big unit
submultiples of metre are used. These are as centimetre (cm), millimetre (mm).

10 Blooming Science & Environment Book 6

Metric Table of Length

10 millimetre (mm) = 1 centimetre (cm)

10 centimetre (cm) = 1 decimetre (dm)

10 decimeter (dm) = 1 metre (m)

10 metre (m) = 1 decametre (dac)

10 decametre (dac) = 1 Hectometremetre (Hm)- Heca or Hecta

10 Hectometremetre (Hm) = 1 Kilometre (km)

In a meter scale, each bigger unit is 10 times more than the smaller unit. Similarly
each smaller unit is 10 times smaller than bigger unit e.g.:

1 cm = 10mm and 1 mm = 1/10cm

For measuring very large distance, the metre is considered too small unit. Kilometre
is used to measure large distance between two places. For example, the distance
between Kathmandu and Pokhara is measured in kilometre (km) which is about 200
km

Method to Measure the Length Correctly

Place the ruler on the sheet of paper as shown in the figure. Your eye must be exactly
above the ruler otherwise you will not get an accurate reading.

mm 1 cm 2 3 4 5 6 7 8 9 10 11 12 13 14 151/16’’ 1 2 3 4 5 6

Accurate measurement of Length:
The following precautions should be taken while using various instruments for
measuring length.
1. The scale should be placed along the length to be measured.
2. Your eye must be fixed in line where the measurement is to be done.
3. Make sure that ends of the scale are not worn out.
4. Measure the length of an object using different positions of the scale and then

take the average of these measurements.
Ways of writing symbols:
a) Same symbol is used for singular and plural both. E.g. 1 metre (1m), 10 metre

(10m) etc.
b) We do not use full stop at the end of the symbol.

Blooming Science & Environment Book 6 11

e.g. 10 mililitre (10mm) Right
10 millilitre (10mm) Wrong

Activity 2

Make a group of five-five students and measure the following and fill in the table
given below.

Length Breadth Thickness/Height Circumference Outer Diameter

Desk
Table
Book
Classroom
Ball
Carramboard
Blackboard

Measurement of Mass

Quantity of matter contained in a body is called its mass. Kilogram (Kg) is the SI
unit of mass. Mass of a body is usually measured by means of a balance. The most
commonly used balance is a beam balance. It consists of a horizontal beam supported
at the center and two similar pans suspended at both sides of the beam at equal
distances from the centre of the beam as shown in given figure. The object whose
mass is to be determined is placed in one of the pans and standard weights are placed
in the other pan till the beam is perfectly horizontal. The mass of the object to be
weighed becomes equal to the standard mass.

The fundamental unit of kilogram alone is not sufficient to measure mass of different
objects Therefore, we use the multiples and submultiples of kilogram.

Beam balances Triple beam balance

For measurement of rice, pulses, sugar, etc at shops, you may use kilogram as unit. If
you want to measure the mass of small objects or small amounts of vegetables, you need
a smaller unit of mass. For this, you can use gram(g) which is one thousand of a kilogram.
A small tablet of medicine or valuable material like gold, diamond, etc are measured

12 Blooming Science & Environment Book 6

in a still smaller unit i.e. milligram (mg). To measure the mass of large bodies like the
bodies of buses, truck, etc., we use a still large unit i.e. metric ton (toner).

Multiples and submultiples of kilogram Scan for practical experiment

10 milligram (mg) = 1 centigram (cg) visit: csp.codes/c6e02

10 centigram = 1 decigram (dg)

10 decigram = 1 gram (g)

10 gram = 1 decagram (dag)

10 decagram = 1 hectogram (hg)

10 hectogram = 1 kilogram (kg)

100 kilogram = 1 quintal

10 quintal = 1 metric ton

The most commonly used units of mass are gram, kilogram, quintal
and metric ton. Weight of an object is the pulling force of the
earth, which pulls the object towards its center. Its unit is ‘N’. It is
measured by spring balance and varies from place to palce.

Weight = mass(m) × aceleration due gravity(g)

=m×g

Measurement of Time

Time is the interval between two events. In ancient time, people didn’t have watch.
By studying regular events such as sunset, sunrise, change in seasons, etc. they used
to calculate time. They called the time interval between two consecutive full moons
as one month and the time interval between two consecutive sunrises or sunsets as
a day.

Nowadays,people use a watch to measure time. There are different types of watches
such as digital watch, quartz watch, pendulum watch, stop watch, etc. to measure
time. The digital watch and the quartz watch give the accurate time. A stop watch can
be started or stopped according to our desire and is used to measure the time taken
by the events.

Stop watch Pendulum clock Digital watch

The SI unit of time is second. We also use bigger units such as minute, hour, day,

Blooming Science & Environment Book 6 13

year, etc. to measure the longer period of time. These bigger units of time are called
multiples of second.

We also use smaller units of time such as microsecond and millisecond to measure the
smaller period of time. These are called sub-multiples of second.

We know that the earth rotates about its own axis as well as it revolves around the
sun. The time taken by the earth to rotate once about its own axis is called a day.

If a day is equally divided into 24 equal parts, each parts is called an hour. If one
hour is subdivided into 60 equal parts, each part is called a minute. If one minute is

subdivided into next equal parts, each part is a second. One second may be defined
1
as the 86,400 th part of a solar day.

The time taken by the earth to revolve once around the sun is called one year. The earth

takes about 365 1 days to revolve once around the sun. Hence, one year equals 36541
4

days.

Metric Table of Time
60 seconds (s) = 1 minute
60 minutes(min) = 1 hour
24 hours (hr) = 1 day
7 days = 1 week

365 days = 1 year

Main Points to Remember

1. Measurement is the basic skill of all scientific study and experimentation.

2. Unit is a must in every measurement.
3. A unit, which always has the same measurement of every person is called standard

unit.
4. The standard unit for measurement of length is a ,metre (m), mass is a kilogram

(kg) and time is a second (s) in MKS system of measurement.
5. CGS and FPS are other systems of measurement.
6. The unit m, kg and s are called fundamental units.
7. Derived units depend on two or more fundamental units.
8. Length is measured using the ruler or other suitable devices.
9. Mass is measured by using beam balance in Kg.
10. The interval between two events is called time.
11. Time is measured using clocks and watches.

14 Blooming Science & Environment Book 6

PRO J ECTWORK

1. Measure the length, breadth, and height of your room and find the volume of air
inside the room.

2. Measure the length, breadth and height of your science book and find its volume.
Show the measurements and calculation to your teacher.

Exercises

1. Fill in the blanks:
a. The three fundamental units are .............., .............. and ..............
b. The standard unit of length is …………………..
c. A gram is a ………………. of a kilogram.
d. One second time is equal to........................ th part of a solar day.

2. Match the following:
Distance between two places temperature
Mass of a body second
Volume kilogram
Length of a book litre
Time centimeter
Hotness of body kilometer

3. State whether the following statements are true or false:
a. Liquids are not measured by their volume.
b. Time is measured by using watch.
c. Water does not have any shape.
d. Measuring cylinder is used to find the mass of objects.

4. Answer the following questions:
a. What is meant by measurement?
b. Define. Why is it necessary to have standard units of measurement?
c. What are the fundamental units used in Science?
d. What are SI units? Define derived units.
e. What precautions should be taken while buying something?
f. How is a metre related to kilometre?
g. Name three physical quantities whose units are used as basic units.
h. What unit of length should be used to express the distance between
Kathmandu and Pokhara? Suggest the way to measure the distance between
the Sun and the Earth?
i. Name the SI unit of time and define it.

Blooming Science & Environment Book 6 15

5. Write the differences between:

a. Mass and weight

b. Fundamental and derived unit

6. Mass can be measured in local units like dharni, pau, etc. Discuss
the advantages of using kilogram as a standard unit of mass over the
local units of mass.

7. SI units are used for the scientific works, why?

8. Why do we need standard units? Write importance of measurement.

9. Convert the followings:

a. 150cm into m b. 5 kg into g

c. 40s into min d. 2km into cm

e. 4.5 kg into g f. 100 min into s

g. 665 hr into s h. 560 hr into days

i. 40gm into kg j. 20mm into m

Answers:

(a) 1.5m (b) 5000g (c) 0.67min (d) 2x105cm (e) 4500g
(j) 0.02m
(f) 6000s (g) 2.39x106sec (h) 23.33 days (i) 0.04kg

Glossary

Local : Confined to a particular region

Tola, Pau, dharni : Local units of measurement of mass

Circumference : The length of the line bounding a circle.

Diameter : Line passing from one side of a circle or sphere to the other
side through the center (thickness in center of a circle)

Measurement : It is a basic scientific skill.

Measuring cylinder : device to measure volume of liquid

Newton : Unit of force

Standard Unit : The unit which is acceptable to all the people as a basic unit
of measurement.

Unit : Certain standard used to measure physical quantity.

Fundamental unit : Unit which is independent of other units.

Mass : The amount of substance contained in the object

16 Blooming Science & Environment Book 6

2Chapter Force

Learning Outcome

On the completion of this unit, students will be able to: Estimated Periods: 5+1
 define force and demonstrate some effects of force.
 explain the change in the state by the application of force.
 define rest and motion.
 define different types of motions with examples.

Force

Force is an external agent which changes or tends to change the position of body. It
is required to do works. The force, push or pull generally causes displacement. The
work is done when sufficient push or pull force is applied and the displacement takes
place. If the force is not enough to cause displacement, the work is not done. The
force of stretch or squeeze changes the shape or size of the object. The gravitational
force of the earth pulls every object to the surface of the earth.

Scan for practical experiment

Fig: Push and pull
The SI unit of force is ‘ newton’ which is written as ‘N’

1N = 1 kg.m/s2

Effects of Force visit: csp.codes/c6e03

Force can move a body at rest or can change the speed of a moving body or can
change the direction of a moving body. For example, a stone is thrown vertically
upwards. Its speed slowly decreases and eventually stops after reaching a certain
height and thereafter it begins to fall. Here, the gravitational force stops motion
changes the speed and the direction of motion of the stone. Thus, force when applied
on bodies produces a various effects. Some effects are discussed below:

1. A force can change the speed of a moving body: When you are pedaling a

bicycle, someone pushes you from behind. Will the cycle move faster or slower?
What will happen if your cycle is pulled back instead? The speed changes in both
cases. Thus a force changes the speed with which a body is moving.

Blooming Science & Environment Book 6 17

2. A force can change the direction of moving body: What happens when you
hit a moving cricket ball with your bat? The direction of the ball changes. A
hockey player strikes the running ball to change its direction. The football player
kicks the moving ball to change its direction. Thus a force changes the direction
in which the body is moving.

3. A force can change the position(state) of a body: Why does a football
move away on the ground when you kick it? It moves because you have applied
force on it. When you catch the football you stop its motion by exerting a force
on it. Thus a force can make a body move and also can stop a moving body.

4. A force can change the shape and size of a body: Take sponges and press it.
The shape of the sponge changes on pressing. Thus a force changes the size and
shape (dimension) of the body.

How to define force?

Force is push or pull, which can make a body move, stop a moving body, change the
direction of motion of a body, change the shape of the body and change the speed of
the moving body. Force is an external agent which changes or tends to change the
position of a body.

Force is calculated from the product of mass and acceleration. Its unit is Newton (N).

F = m × a. where m is mass in kg and a is acceleration in m/s2.

Rest and Motion

Sometimes we wait for our friends at the bus stop. We sleep at night, we sit on the
bench of classroom. In such case we don’t change our position with respect to the
surrounding. We are in the state of rest . So, a body is said to be at rest if it does not
change its position with respect to its surrounding.

Vehicles run on the roads. Birds fly in the sky, water flows in the river. In all those
cases, they change their position with respect to the surrounding. A body is said to be
in motion if it changes its position with respect to the fixed point or time. Or A body
is said to be in motion if it is changing its position relative to some other objects. For
example, a car moving on a road is said to be in motion with respect to the roadside
buildings. Rest and motion are relative terms. We can’t say the state of motion or rest
of any body without comparing it with surrounding. If we are on the seat of a moving
bus, we are at rest with respect to other passengers. But we are in motion with respect
to the homes, trees and poles at the same time.

Differences between Rest and Motion

Rest Motion

1. A body is said to be at rest if it does 1. Abody is said to be in motion if it changes
not change its position with respect to its its position with respect to its surrounding.
surrounding.

2. Houses, trees, mountain etc. are the 2. Moving car, flying aeroplane,

examples of it. walking dog, etc. are the examples of it.

18 Blooming Science & Environment Book 6

Types of Motion

There are several types of motion. Some of them are given below

1. Linear Motion: The motion in which an object moves in straight line is called
linear motion. It is also called translatory motion.

Examples: a bullet fire from a gun, a boy sliding down a slope, a ball rolling on
ground etc.

Linear motion

Activity

Tie a small pebble on a rope and allow it to fall down
from the terrace of your home. You will see the rope
being straight to the ground. Again drop another
pebble from the same place. It falls on the same way.
The motion of pebbles in both cases is linear motion.

2. Circular Motion: The motion in which an object moves along a circular path
is called circular motion.

Examples: a bull in a crushing mill, people in
roteping, etc.

Scan for practical experiment

Activity visit: csp.codes/c6e04

Tie a small piece of stone on the rope and rotate it
around the arm. What about the piece of stone? You will
see that the stone rotate in circular motion. It means that
the distance of this stone is always the same to the finger.

Blooming Science & Environment Book 6 19

3. Rotatory Motion: The motion in which a body does not change its position
and moves about an axis is called rotatory motion. A body moves about a fixed
axis without changing its position. A potter’s wheel, a spinning top, , a merry
go-round, motion of a spinning wheel, flywheel of a sewing machine, etc are
the examples of the rotatory motion.

4. Oscillatory Motion: When an object moves forward and backward again and

again, the motion of the object is called oscillatory motion. Examples: pendulum

of clock, child on a cradle, a body on a swing, etc. Scan for practical experiment

visit: csp.codes/c6e05

Activity

Tie a small round stone to one end of a string and tie the other end
of the thread to a hook fixed on the wall. The stone will hang freely.
Let it come to rest. When the hanging stone is perfectly at rest, give
a gently push.

What will you see?

The stone moves equal distance forward and backward again B A C
and again.

This is an example of oscillatory motion.

5. Random Motion: When an object does not show any Random Motion
regular motion, the motion of the object is called random
motion. These types of motion have no direction and no
sequence of time.

Some examples of random motion are:

(i) Movement of a football player on the play ground

(ii) Movement of a butterfly round a flower

20 Blooming Science & Environment Book 6

(iii) Movement of house-fly or mosquito
(iv) Movement of dust particles
6. Spiral Motion: When an object shows both the rotatory and linear motion at
the same time, the motion of the object is called spiral motion.
Some examples of spiral motion are:
i) A driller used by a carpenter has both the rotatory

and linear motion at the same time.
ii) The rotation of the earth in its axis and around the

sun has both rotatory and linear motion at the same
time.
iii) The motion of a cricket ball thrown by a bowler has spiral motion.

7. Vibratory Motion: Rapid to and fro motion is called
vibratory motion. Examples are:

(i) string of guitar when plucked
(ii) wings of a mosquito or butterfly when flying.

Main Points to Remember

1. A body is said to be in motion if it changes its position with respect to its
surrounding bodies.

2. If a body does not change its position with respect to its surrounding bodies, it
is said to be at rest.

3. Push or pull is called force.
4. Force can change the shape, motion and direction of the body.
5. The different types of motion are translatory, circular, curvilinear, rotatory,

spiral, vibratory, oscillatory, etc.
6. The motion of a body along a straight line is called linear motion.
7. If the direction of the motion changes continuously, it is called curvilinear

motion.
8. The motion of a body in a circular path is called circular motion.

Blooming Science & Environment Book 6 21

9. The motion of a body having both linear and rotatory motion simultaneously
is called spiral motion.

10. If a body moves about a fixed axis, the motion is called rotatory.

11. If a body moves forward and backward about its mean position, the motion is
called oscillatory.

12. The very fast oscillatory motion is called vibratory motion.

PRO J ECTWORK

1. Make your own simple pendulum by tying a stone or a cork or a pendulum
bob to a string and the other end of the string on a fixed hook suspend the
bob on a risid support.Now set the pendulum bob to swine carefully through
a certain angle. Find out the number of oscillanons before coming to rest and
write about oscillatory motion

2. Collect the names of different moving objects that you see around. Name the
type of motion and study about the effects of force acting on the body.

Exercises

1. Fill in the blanks.

a) Motion of the earth round the sun is ………………… motion.

b) A tree does not change its position with respect to its ………

c) The motion of a merry-go-round is ……………… motion.

d) …………………. can make a moving object move faster.

e) In …….. motion, an object does not show any regular motion.

2. Match the following:

Column A Column B

A bullet fired from a rifle random motion

A pendulum of a wall clock linear motion

Rotation of the earth around the sun rotatory motion

Motion of the potter’s wheel spiral motion

Movement of a housefly oscillatory motion.

3. Choose the correct answer.

a) The agent which pulls or pushes an object is called

22 Blooming Science & Environment Book 6

(i) motion (ii) energy
(iii) force (iv) gravitation

b) While driving a bicycle which of the following motion does not take place?

(i) linear motion (ii) oscillatory motion

(iii) circular motion (iii) spiral motion

c) Which of the following is not the effect of force?

(i) change in the shape of an object

(ii) change in the direction of object

(iii) change the state of an objects

(iv) none of them

d) In a linear motion a object always move in

(i) a straight line (ii) a circular path

(iii) a random way (iv) a curved path

e) What is the motion of a child sitting on a merry-go-round?

(i) linear (ii) circular

(iii) rotatory (iv) random

4. Tick () mark on the right statement and cross mark (×) on the
wrong.

a. Force is not necessary to state the motion of an object.

b. A tree does not change its position with respect to its surroundings.

c. The unit of force is Newton.

d. A child sliding down the slope has circular motion.

e. The unit of speed is m/s.

5. Answer these questions.

a) What is force? Write its unit.

b) What is pulling force?

c) What is pushing force?

d) What is rotatory motion? Give 2 examples.

e) Define linear motion with 2 examples.

f) Give two examples of oscillatory motion.

Blooming Science & Environment Book 6 23

g) What are the effects of force? Explain.
h) Explain the term rest and motion with suitable examples.
i) What is circular motion? Give three examples.
j) What is spiral motion? Give three examples.
k) Rest and motion are relative terms, why?
6 . Show the differences between
a. Rest and Motion
b. Pushing force and Pulling force
c. Circular motion and Rotatory motion
d. Linear motion and Spiral motion
e. Oscillatory motion and Random motion

Glossary

Linear motion : the motion of a body in a straight line.

Circular motion : the motion of a body in a circular path.

Rotatory motion : the motion of a body around its own axis.

Spiral motion : the simultaneous rotatory and linear motion in a body.

Oscillatory motion : the forward and backward motion about a fixed
position.

Pendulum : an irregular motion in a body.

Squeeze : press something from both sides

Pedaling : using or moving something by force of foot

Spinning : turning around, rotating freely

24 Blooming Science & Environment Book 6

3Chapter Simple Machine

Learning Outcome Estimated Periods: 2+1

On the completion of this unit, students will be able to:
 define simple machine.
 name different simple machines used in daily life.
 describe uses of simple machine.
 tell examples of various simple machines.
 classify the different types of simple machine

Introduction

Different kinds of work such as lifting a bucket full of water from a well, moving
heavy objects, opening a lid of a tin can etc. are done in our daily life. Some works
are done easily by hands, while others need the use of devices or instruments. For
instance, a pulley is used to lift water from a well, a crowbar is used to move a heavy
rock, spoon handle is used to open the lid of the can, scissors are used for cutting etc.
These devices are machines but unlike complex machines, they do not contain many
parts. Such machines are called simple machines.

Human beings have been using machines since time immemorial. Today, various types
of machines are used in our everyday life. The simplest machines such as levers, pulleys,
screws, wheel and axles, wedges and inclined planes etc to the most complicated machines
and engines make our works easier. In fact, complex machines such as sewing machine, a
bicycle or tractors are the combination of a few simple machines such as levers, pulleys,
screws etc. So, the device which has simple structure and makes our work easier, faster
and convenient way is called simple machine.

Advantages of Simple Machines
A simple machine is used because it helps us to do different works easily and
conveniently. The simple machines have mainly the following advantages:

Blooming Science & Environment Book 6 25

1. A simple machine multiplies the force and it makes our work easier.

Activity

To study that a simple machine makes the work easier.

Materials required: A meter scale, two different weights and a triangular wooden
block and pivot.

Method: Take a meter scale. Place it over a triangular pivot so that the shorter length
of the scale lies on one side of the pivot and the longer one on the other side. Place
a heavier weight(100g) and place it on the shorter side from the pivot. Starting from
the closed to the pivot go on increase the distance of 50g weight from the pivot. What
do you find? You see that the 50g weight, it lifts the load of 100g if placed at suitable
distance from the pivot.

This activity shows that a smaller effort can lift a heavy load with the help of a simple
machine. This means a machine multiplies the applied force and makes work easier.

2. A simple machine changes the direction of applied force.

The direction of force can be changed with the help of a machine.
This is explained in the discussion of a pulley. By applying a force
in one direction, load can be moved in another direction. This
enables us to apply the force in convenient direction.

3. A simple machine increases the speed of doing work.

A piece of work becomes faster by the use of simple machines. For example, we can
consider a sewing machine. If we try to rotate the wheel ‘W’ of the sewing machine,
by applying force the wheel itself, we cannot rotate it very fast. But when the effort
is applied to the handle H, the rate of rotation can be increased. Sometimes a work is
needed to be done quickly. Usually the work which needs little effort can be done
faster. Another example, little effort is needed to cut cloth than to cut metal sheet.
The ordinary scissors which are used to cut clothes has longer Scan for practical experiment
blade than that used to cut metal sheet. So, ordinary scissors
can cut clothes faster.

A sewing machine Metal cutting scissors visit: csp.codes/c6e06

26 Blooming Science & Environment Book 6

4. A simple machine supports in doing unsafe and dangerous jobs.

Machines help us to do certain works which are otherwise unsafe and dangerous. A
burning coal from the coal stove can be lifted by using a pair of fire tongs. We use a
pair of tongs to pick the nettle leaf.

Types of Machine

According the structure and the principle of working, simple machines are classified
into six types:

1. Lever 2. Pulley 3. Wheel and axle

4. Inclined plane 5. Screw 6. Wedge

1. Lever

A lever is a rigid bar, straight or curved, which is free to turn about a fulcrum. The
distance between the fulcrum and the load is called the load arm and the distance
between the effort and the fulcrum is called the effort arm of the lever. When the
effort ‘E’ is applied at some convenient point on the lever, it is made available to
overcome a resistance ‘L’ at another point. It is based on the principle of moment.
Principle of moments states that for an equilibrium condition, the moment of the
effort about the fulcrum must be equal and opposite to the moment of load (weight)

about it. So that, we have,

effort second class levers effort
load
effort load

load

pivot fulcrum fulcrum
effort

Effort × Effort arm = Load × Load arm (This is also called principle of lever)

Different types of levers and their examples

Types of Lever Position of Fulcrum Examples
First Class lever L, F and E
Pair of scissors, beam balance,
Second Class Lever F, L and E pliers, handle of pump, sea-saw
Third Class Lever F, E and L
Bottle opener, wheel barrow, nut
cracker

Fire tongs, knife, shovel

Blooming Science & Environment Book 6 27

2. Pulley

Pulley is a metallic or wooden circular disc, which has
groove along its circumference over which a rope can
pass easily. Load is generally attached at one end of the
rope and effort is applied at another end. Pully can be
classified in 3 category:
i) Fixed pulley:
Pulley which does not change its position is called fixed pulley.
ii) Movable pulley:
A Single movable pulley is generally not used in practice, as it is inconvenient
to apply the effort in the vertical direction. For the sake of convenience,
one fixed pulley is added. So that, the effort is conveniently applied in downward
direction.
iii) Mixed (combined) pulley:
It is made by combination of a fixed and a movable pulley. As it magnifies the
force applied and changes the direction, it is more convenient to use.

Scan for practical experiment

visit: csp.codes/c6e07

Fixed pulley Movable pulley Mixed (combined)puley

3. Wheel and Axle

The wheel and axle is very common in many types of machinery and everyday life.
In a car, for example, the steering wheel and the handles of sewing machine, moving
the paddle of bicycle and using the screw driver to turn the screw are all wheel and
axle. In our everyday life, we use door handle, spanner and screw driver, bicycle
pedal, windlass and handle of the sewing machine. All these machines use the wheel

and axle principle.

Fig:Wheel and axle

28 Blooming Science & Environment Book 6

A wheel and axle is a combination of two cylinders of different radii, fitted one into
the other, the bigger one being called the wheel and the smaller one, the axle. Both
the wheel and axle rotate and are without groove at the circumference.

4. Inclined plane

A sloping surface along which a heavy load can be pushed
up with less effort is called an inclined plane. An inclined
plane is simply a sloppy surface over which a load can
be pushed or pulled up. A plank of wood is often used to
load the heavy barrels up onto a truck as in figure below.
It is difficult to raise the heavy loads vertically by lifting
because it needs more force. When the load is pushed
or pulled along an inclined plane, less effort is required and becomes easier. The
steeper the inclined plane the greater is the effort required to lift the load. Roads
in the hills, ladders, ramps, etc are some examples of inclined plane. It should be
remembered that the distance travelled by a load along the inclined plane is greater
than the distance when the load is lifted vertically.

5. Screw

The screw is a special case to an inclined plane, which has been
rolled up. A screw consists of a hard metal rod having well cut
spiral threads on its surface. The distance between successive
threads of the screw is called the pitch.

When one rotation is given to the screw it moves a vertical Fig: Screws
distance equal to the distance of two successive threads. This

is the principle of the screw. The principle of action of the screw is similar to that

of inclined plane. The screw is a simple machine formed by rolling up the inclined

plane.

6. Wedge Wedge

Any sharp instrument which helps us to cut the things is called
wedge. It is a simple machine with a triangular shape, which
is used to split an object apart. A wedge is actually an inclined
plane, which can be of metal or a piece of wood. It has a sharp
and thin edge on side and it gets thicker as it reaches to the other
side. Wedge is helpful in many ways such as to split woods apart, Fig: Wedge
to cut the vegetable and papers etc. knife, blade, axe, chisel, etc.

Blooming Science & Environment Book 6 29

Main Points to Remember

1. A simple machine is a device that helps to do work more easily and more
conveniently that could be done by hand.

2. Load is the thing, which is carried or lifted by a machine.
3. We use simple machines because they -
a. Multiply the applied force
b. Change the direction of force
c. Increase the speed of doing work

d. Help us in doing unsafe and dangerous work

4. The force with which the load is carried or lifted by using a machine is called
the effort.

5. Lever, the pulley, inclined plane, wheel and axle, screw and wedge are the
simple machines.

6. As lever is a rigid bar which is free to turn about a point called fulcrum.
7. Levers are of three types according to the positions of the effort, load and

fulcrum.
8. Load × Load arm = Effort × Effort arm is the principle of lever.

PRO J ECTWORK

Collect the different tools used in house. Classify them into different types of simple
machines and mention their use also.

S.No Name of tools Types of simple machines use
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

30 Blooming Science & Environment Book 6

Exercises

1. Fill in the blanks:

a) In a machine the force applied is called ………………………. and the
force overcome is called the ………………..

b) Machines are used to gain …………….. change the direction of ................
and to gain ………………..

c) Six types of simple machines are …………., ……………., ....................,
…………….. and ………………..

d) A ……………….. is a rigid bar, which is free to turn about a fixed point.

e) The point of support in a lever is called its …………………

f) The more steep the ……………………… is the more force we need to
push up a load.

g) The wheel and ……………………… form a simple machine.

h) The principle of the screw is based on the principle of the ……………..

i) The pulley changes the …………………… of the force.

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

a. In the second class lever the fulcrum is in between the load and the effort.

b. Pulleys change the direction of force.

c. A pulley fixed on a well helps in drawing more water with less effort.

d. Levers make the work easier.

e. Beam balance is a simple machine.

f. The point supports the lever is called its fulcrum.

3. What kind of simple machine is each of the following?

a. Beam balance b. Pair of scissors

c. Roller skates d. Wheel with a wire going around its grooved rim

e. Pair of pliers f. Nut cracker

g. Bottle opener h. Wheel barrow

i. Knife j. Nail

Blooming Science & Environment Book 6 31

4. Answer the following questions:
a. What is meant by a simple machine?
b. What are the purposes of using simple machine?
c. What is a lever? Draw a lever and label it.
d. What are the various classes of levers? Give 2/2 examples of each.
e. A pair of scissors designed for cutting cloth has blades that are longer than
the handles. Scissors designed for cutting metal have blades shorter than
the handles. Explain.
f. Why is it easy to open the lid of the tin with the help of spoon?
g. What is pulley? Describe a type of pulley with a neat sketch and a suitable
example.
h. Name the simple machine, which changes the direction of force.
i. Draw a diagram of wheel and axle and give two examples of this type of
simple machines.
j. What is an inclined plane? Write any two uses of inclined plane. Write two
examples of inclined plane.
k. Define screw with any 2 examples.
l. Define wedge. Give any 3 examples.

5. Write short notes on:
a. pulley b. wheel and axle d. inclined plane
6. Two methods of using a crowbar are shown in the figures below.

Study them and answer the following questions:

a. In which lever, work can be done fast?
b. In which lever, load can be lifted by using less force?

32 Blooming Science & Environment Book 6

Glossary

Simple Machine : a simple device that makes work easier and faster.

Lever : a rigid bar free to move around a point.

Pulley : a circular wheel with a groove on its rim for rope.

Wheel and axle : a type of simple machine with two cylinders.

Inclined plane : sloping surface.

Screw : a simple machine with a highly curved inclined plane.

Wedge : a simple machine consisting of two inclined planes.

Load : object to be lifted.

Effort : the force applied to lift the object.

Rigid : Very strict and difficult to change.

Knob : A round handle.

Steering : The machinery of a vehicle, used to control the direction it goes in.

Groove : A long narrow cut in the surface of something hard.

Plank : A long narrow flat piece of wood.

Multiplier : Somebody or something that multiplies or increases

Pile : a hand tool to grip nails or something

Delicate : something that is easily damaged or broken

Sake : benefit, welfare

Tweezer : an instrument for holding small objects

Blooming Science & Environment Book 6 33

4Chapter Heat

Learning Outcome Estimated Periods: 5+1

On the completion of this unit, students will be able to:
 define heat and temperature.
 identify various sources of heat and its uses.
 demonstrate the effects of heat in daily life
 explain cause and effects of absorption of heat.
 explain uses of heat in daily life
 measure temperature by using thermometer.

Introduction

In winter we like to sit in the sun or near the heater and wear warm clothes to give
warmth to our body.

We cannot see heat but we can feel heat. To find out whether an object is hot or cold,
we touch it gently with our fingers.

Heat is a form of energy which gives the sensation of warmth to our body. It is
produced from total kinetic energy of molecules of a body. The SI unit of heat is
Joule (J) and is measured by caloriemeter.

Activity

Take a kettle with its lid. Fill it half with water. Fit a small cork on the nozzle of the
kettle lightly. Heat the water of the kettle for some time. As the water gets heated, you
will notice that the cork is blown off by the steam.

What do you learn from this activity? Wa t e r
vapour
This activity shows that heat is a form of Cork
energy. Due to this energy, work is done to
push the cork. Kettle
Heater
Similarly, we have seen that lid of pressure
cooker lifts up and down during the Boiling water and blown cork
cooking of food. Inside the pressure cooker,
water is converted into steam due to the
heat supplied. The steam in turn gives the
pressure to the lid of the cooker or cork of
the kettle.

34 Blooming Science & Environment Book 6

What happens if the hole of the lid of pressure cooker is closed?
James watt invented steam engine using the energy of the steam. In a steam engine,
coal is burnt to produce heat. The heat so produced turns water into steam. Steam
under pressure pushes the piston of the engine and makes the piston move. Thus heat
produced by burning of coal is converted into energy to turn the wheels of a train.
Thus, heat is a form of energy, which has the ability to do work.
Sources of Heat
The main sources of heat which we are using in our daily life are given below
a) The Sun: The sun is the major source of heat. It gives us heat and light. All the

animals and plants of the earth get heat from the sun. Plants use heat to prepare
food and animals eat the plants. The life on the earth would be impossible
without the heat of the sun.

Scan for practical experiment

visit: csp.codes/c6e08

Fig: Plants prepare food using sunlight and animal eats plants
b) Fossil Fuel: Heat can be produced by burning of fossil fuel like, diesel, petrol,

LPG, coal, kerosene, etc. These substances are called fuel. Fuel are useful
source of heat for us. Bus, train, truck, van, aeroplane use petrol, diesel, coal,
etc. as fuel.
c) Bio-Fuel : The heat energy is obtaoned from biomass fuel like bio-gas,
dry cakes of animal dung, straw, hay, wood, etc. The energy obtained from
biological raw materials is called as bio-fuel energy. This form of energy is
used for cooking, warming the rooms in winter, etc. in villages of our country.
Some people generate the bio-gas by collecting dung in a specially made pid
and use for various purposes.

d) Electricity: Electricity is also one of the major source of heat energy. Various
devices convert electric energy into heat energy and used for various purpose.

Blooming Science & Environment Book 6 35

You have seen electric heaters. When electric current is passed through the
heater, heat is produced in it. In this case electrical energy is changed to heat
energy. Electric iron and electric kettle are heated due to electricity.

Electric Heater Electric Iron Electric Kettle

Activity

On a sunny day, take a magnifying glass. Move the
lens closer or further away to focus the sunlight on a
piece of paper just below the lens. If the sunlight is
focused for a while, the paper begins to burn.

What do you learn from this activity?

Effects of heat
We use heat for different purposes. When heat is given to a body there are various
changes in the body. The changes in the body due to the heat given to it are called
effects of heat on the body. Some effects of heat are discussed below:
1. Heat increases the temperature of a body.
When heat is supplied to a body, it becomes hot. A knife kept outside in the sun for
somtime becomes hot. Staying outside in the sun makes us feel hot. Heat given to
water in a pot makes water very hot. In this way the supplied heat on a body increases
the hotness of that body.

2. Heat changes the state of matter.

For example, when ice is heated it changes into liquid (water) and on further heating
the water it changes into the gaseous form (steam).

Activity

To study the change of state due to heat

Materials required: a beaker, a tripod stand, a burner or lamp,
and ice pieces.

Take some ice pieces in a beaker. Put the beaker on a tripod
stand. Heat gently with a burner or spirit lamp. After heating
sometime, you will get water present in the beaker. On heating the water further to
its boiling point, you will see water vapour releasing out of the beaker. This activity
shows that heat changes the state of matter from solid to liquid and from liquid to gas.

36 Blooming Science & Environment Book 6

Ice Heat Water Heat Steam
(Solid) (Liquid) (Gas)

In hot seasons, the level of water in the pond, lake, sea, etc is found to be decreased.
This is because the heat from the sun changes the water into water vapour forming
the clouds. When the cloud becomes cold, it again changes into water and falls as
rain.

3. Heat causes the expansion of body.

When a body is heated its size or volume increases. This upper fixed
property is called expansion. All the matter expand on heating point
whether it is solid, liquid or gas. When a body is cooled the
reverse takes place i.e. it contracts. boiling
water

Activity

To study the expansion of solid.(Ball and Ring Experiment)

Materials required: stand, Grabsand’s ball and ring apparatus, burner.

Take a ball and ring apparatus that consists of a ball suspended in a string and a ring.
See that the ball can just pass through the ring when not heated. Heat the ball over a
flame for sometime and then try getting it through the ring. It is found that the ball no
longer passes through the ring. On cooling the ball again, passed through the ring.
This shows that the ball does not pass through the ring when it is hot and passes easily
when it is cold.

Conclusion: Stand

Chain

This experiment shows Ring
that the solid expands on Grabsand’s ball
heating and contracts on
cooling

(a) Before heating (b) After heating

Fig: Ball and ring experiment

Blooming Science & Environment Book 6 37

Activity

To study the expansion of liquid

Materials required: A round bottomed flask, a rubber cork, a glass tube, stands and
a burner.

Stand Glass tube

B
A

Cork

Round-bottomed flask

Tripod stand
Burner

Fig: Expansion of liquid

Take a round bottomed flask. Fill it completely with coloured water. Insert a rubber
cork filled with a narrow glass tube into the flask so that some water rises a short way
up the tube. Mark the level of the water in the tube. Now heat the flask keeping on a
tripod stand. Observe the level of the water in the tube. You will notice that the level
of water first falls down and then rises up. The level of water initially is in A in the
given figure. When heated, the level falls below A at first because of the expansion of
the flask. After that the water expands and its level rises up in the tube and reaches
B. Now remove the burner. After a while, you will see the level of water in the tube
decreasing.

Conclusion:

This experiment shows that liquid expands on heating and contracts on cooling.

Note
Water shows unusal behaviour when heated from 0oC to 4oC i.e instead of expansion it
contracts. But beyound this range (0oC to 4oC), it shows normal behaviours ie. it starts
expanding as like other liquid. This property is seen only in water.

38 Blooming Science & Environment Book 6

Activity

To study the expansion of gases.
Materials required: A round bottomed flask, a rubber cork, a stand, a beaker, a candle
and a glass tube.

Round-bottomed flask

Stand Candle

Glass tube
Beaker

Air bubbles

Fig: Expansion of gas

Take a round bottomed flask. Fit a narrow glass tube with the help of an air-tight
rubber cork. Fix the flask in a stand so that the tube points downwards as shown in
figure. The tip of the glass tube is immersed in the coloured water kept in a beaker.
Warm the flask gently over the flame of a burning candle. You will see air bubbles
coming out of the tube from the water. This shows that air expands on heating. Now
allow the flask to cool. The water is seen rising up the tube. When cooled, the air
inside the flask contracts and takes less volume. To fill the volume left by contraction
the water rises up the tube.

Conclusion:

This experiment shows that the gas expands on heating and contracts on cooling.

The cables stretched between two lamp posts sag below during the hot seasons due
to their expansion. We use a wet piece of cloth soaked in hot water to open the lid of
a bottle when it gets tightly fitted and becomes difficult to open. When we hold the
lid with hot piece of cloth, it expands and becomes easier to open. Mercury is used
in a thermometer to measure temperature. The principle of expansion of mercury is
used to construct a thermometer. The incidents mentioned above are some different
examples of expansion to which we are familiar in our daily life.

Blooming Science & Environment Book 6 39

Uses of Heat

Heat is very useful to us. Some of its uses are as follows:

1. To cook food: Food is cooked by burning wood, kerosene, cooking gas, etc.
An electric heater is also used for the same purpose.

2. To keep our body warm in winter: By burning wood, coal, etc. we receive
heat and feel warmth in winter. Electric heater, kerosene heater, etc. are also
used to get heat. In the cold countries, hot water is circulated through black
pipes in the rooms to get heat.

3. To run factories: Brick factories, cement factories, etc. consume a large
amount of heat which is obtained either by burning of wood or coal or by
electricity. By burning fuels the required heat can be obtained for running the
factories.

Goldsmiths and blacksmiths also use heat. Heat energy is required in mine for
extracting metals from the ores.

4. To run vehicles: Buses, trucks, cars, motorbikes, etc. run when fuels like
petrol or diesel are kept inside the engine and provide heat to the engine.

Besides these, heat is used for many other proposes like drying clothes, pressing
clothes, etc.

Uses of the Solar Energy
Solar energy has been used for drying clothes, food and for obtaining salt from the
sea water. Solar cooker, solar heater, solar cell, etc. use solar energy to generate heat
for various purposes. Solar cell converts solar energy into electric energy.
We are receiving heat and light from the sun continuously without any cost. The plants
prepare their food in the presence of sunlight. Animals and human depend on the
plants for food. Thus, the sun is the main source of energy.
The sun is a renewable source of energy. Fuels like wood, petroleum products, fossil
fuels are limited. One day, these fuels will be emptied and should depend on the
renewable sources of energy like wind energy, water energy, solar energy, etc. These
sources do not cause any pollution. The artificial satellites also use solar energy.

Absorption of Heat

A body becomes hot when it absorbs heat energy and becomes cold when it loses
heat energy. Heat is a form of energy which is transfered from hot medium (object)
to cold medium(object). Different coloured objects absorb heat energy in different
extent black bodies absorb heat energy in highest extent whereas white bodies
absorbs the least amount of heat energy.

40 Blooming Science & Environment Book 6

Activity

To show that black objects are good heat absorbers.

Material Required: Two aluminium mugs one painted with black colour and the
other with white colour, thermometers, water, paper pieces, etc.

Method:

i) Fill about half water in two aluminium mugs with black and white.

ii) Fix a thermometer in each with the help of a paper piece by covering the mouth
of mug.

iii) Keep both the beakers outside in the susshines for about half an hour.

Observe the temperature reading shown by both thermometers and draw your
conclusion about the good absorbers of heat.

Thermometer Thermometer
Paper
Paper

Balck mug White mug
Water Water

Some applications of absorption of heat

* Generally utensils with black and rough surface are prefered in cooking.

* Black pipes are used in solar panels.

* We prefer to wear dark and black coloured clothes in winter season.

Temperature

When we touch a piece of ice, we feel cold. This is because the heat flows from our
hand to the ice. The ice is at a lower temperature than our hand. This example suggests
that temperature tells us how hot or cold a body is. Therefore, the temperature is
the degree of hotness or coldness of a body. The SI unit of temperature is Kelvin
(K). Other commonly used units of temperature are degree Celsius (oC) and degree
Fahrenheit (oF).

By touching, we can get a rough idea about how hot or how cold a body is. But our
sense of touching always does not work well. That's why we use a special device to
mesure the temperture.

Blooming Science & Environment Book 6 41

Thermometer

The instrument used to measure the temperature of a body is called thermometer.
When a body is heated, it expands, and when cooled it contracts. This is the principle
of a thermometer.

Bulb Mercury Capillary Scale Glass stem

-10 0 10 20 30 40 50 60 70 80 90 100 110 oC

Fig: Laboratory thermometer

A commonly used thermometer consists of a long narrow tube with a uniform fine
bore in it from one end to another. Its one end is sealed and the other is attached
with a small cylindrical bulb. The bulb is filled with mercury or alcohol. The narrow
tube is enclosed with a thick glass stem. There is a scale on the surface of the glass
stem which helps to read the recorded temperature. To measure the temperature of
the hot water in a beaker, its bulb is dipped into the water. The mercury in the bulb
expands and rises in the capillary. The level upto which the mercury rises reads the
temperature of the water.

Note
The liquid used in a thermometer is called thermometric substance. The thermometer
in which liquid used as thermometric substance is called liquid thermometer.
Mercury and alcohol are thermometric liquids.

Clinical Thermometer

The thermometer used to measure human body temperature is called the clinical
thermometer. It is actually a short-range mercury thermometer. It is generally
calibrated only from 35oC to 42oC. That’s why, it cannot be used to measure the
temperature of the boiling water i.e. 100oC.

Bulb Constriction Scale

35 36 37 38 39 40 41 42 43 oC

Fig: Clinical thermometer

The clinical thermometer has a small constriction or kink just above its bulb. It helps
in taking correct reading because the mercury easily passes up through this kink
when the temperature rises, but it does not lower down through the kink when the
temperature falls. Thermometer needs a jerk to fall the mercury back in the bulb. The
normal human body temperature is 37oC or 98.6oF in our body.

42 Blooming Science & Environment Book 6

Differences between Heat and Temperature

Heat Temperature

1. It is a form of energy that gives 1. It is a degree of hotness or coldness of
sensation of warmth. a body.

2. It is measured by using caloriemeter. 2. It is measured by thermometer.

3. Its SI unit is Joule. 3. Its SI unit is Kelvin.

Main Points to Remember

1. Heat is a form of energy which is produced from total kinetic energy of
molecules of a body.

2. The SI unit of heat is Joule and it is measured by caloriemeter.

3. The changes in the body due to the heat given to it are called effects of heat on
the body.

4. When a body is heated its size or volume increases. This property is called
expansion.

5. The temperature is the degree of hotness or coldness of a body. The SI unit
of temperature is Kelvin (K). Other commonly used units of temperature are
Celsius (oC) and Fahrenheit (oF).

6. The liquid used in a thermometer is called thermometric substance. The
thermometer in which liquid used as thermometric substance is called liquid
thermometer. Mercury and alcohol are thermometric liquids.

7. The thermometer used to measure human body temperature is called the clinical
thermometer.

8. The normal body temperature is 37oC or 98.6oF in our body.

9. The black bodies are food absorbers of heat and the white bodies absorb least
heat energy.

PRO J ECTWORK

Take a bottle made of plastic. Pour some hot water into it. Close the mouth of the
bottle with cork. Keep the bottle in a bucket containing cold water. Write what happens
to the bottle. What can you prove from the experiment?

Blooming Science & Environment Book 6 43

Exercises

1. Fill in the blanks:

a. Heat is a form of ……………..
b. Heat gets transferred from ………… end to ………….. end
c. Solids ……………… on heating.
d. It ……………. on cooling.
e. Main source of heat is ………………..
f. …………………….. discovered the steam engine.
g. …………….. is released when food is oxidized.
h. ………………. is required to keep our body warm.
i. Solids ……………… on heating and ………….. on cooling.
j. The degree of hotness or coldness of a body is called the …………
k. ……………… is used to measure temperature of a body.
2. State whether the following statements are True or False:

a. There is no importance of heat in our daily life.
b. Gas expands the least on heating.
c. Solid contracts on cooling.
d. Liquid also expands on heating.
e. Clothes dry quickly on the cool area.
f. Celsius is unit of temperature.
g. Mineral fuel is the main source of heat.
h. Celsius is the instrument to measure temperature.
i. The interior of the earth is very hot.
j. Heat energy is required to keep the body warm.
3. Match the following:

Heat source of heat
Temperature energy
Friction Celsius
Thermometer hotness and coldness
Sun heat energy

44 Blooming Science & Environment Book 6

4. Choose the correct answer:

a. Which one is the natural source of heat?

i. Forest ii. Coal

iii. Sun iv. Heat of the interior of the earth.

b. Thermometer is used to measure -

i. Heat energy ii. Temperature

iii. Hot and cold iv. Coldness

c. What happens to the cells when the temperature drops?

i. Becomes active ii. Becomes inactive

iii. Grows iv. Nothing happens

d. Which is the main source of heat?

i. Coal ii. Fire

iii. Sun iv. Electricity

e. Which of the following is not the use of heat?

i. Cooking food ii. Running vehicle

iii. Drying clothes iv. Running windmill

f. Which of the following is not fuel?

i. Petrol ii. Coal

iii. Kerosene iv. Mud

g. What is the boiling point of water?

i. 40ºC ii. 50ºC

iii. 100ºC iv. 150ºC

h. Which device is used to measure temperature?

i. Thermometer ii. Round bottom flask

iii. Heater iv. Manometer

5. Answer the following questions:

a. What is heat? Write unit of heat.
b. What is the source of heat? Make a list of different sources of heat.
c. Write any four effects of heat.
d. How do we maintain heat in our body?
e. What is temperature? What are the units of temperature?
f. What is a thermometer? What is normal temperature of human body?
g. How can we prove that solid expands on heating?
h. Does gas expand on heating? Explain
i. Out of solid, liquid and gas which expands the most when heated?

Blooming Science & Environment Book 6 45

j. How do we utilize heat in our daily life?
k. Distinguish between heat and temperature.
6. Differentiate between

a. Heat and Temperature
b. Expansion and Contraction
7. Give reason

a. Expansion gap is left in the railway tracks.
b. When we rub our hands we feel hot.
c. Gas expands more than liquid on heating.
d. Dead body is cool.
e. We wear woollen clothes in winter.

8. Label the given parts. D E F
AB C

-10 0 10 20 30 40 50 60 70 80 90 100 110oC

Glossary

Heat : a form of energy

Temperature : degree of hotness and coldness of a body.

Oxidation : the process of breaking down food in body with the help of oxygen
to release energy.

Matter : thing occupies space and has mass.

State : form of matter.

Expansion : increase in volume due to heat.

Thermometer : a device to measure temperature of body.

Degree Celsius : unit of measurement of temperature.

Kelvin : unit of measurement of temperature

Mercury : an element

Fuel : material to produce heat

Kink : narrow neck present in thermometer.

LPG : Liguified Petroleum Gas

46 Blooming Science & Environment Book 6

5Chapter Light

Learning Outcome Estimated Periods: 5+1
On the completion of this unit, students will be able to:

 define light and tell various sources of light.
 differentiate luminous from non-luminous objects with examples.
 to explain and demontrate features and uses of transparent, opaque and

translucent objects.
 describe and demonstrate rectilinear propagation of light.

Light

Light is of great importance in our daily life. Even though we do not need light at
daytime we need light at night. At dark night nothing is visible because there is no
light. We cannot see at night. Light is the source of energy which helps us to see
things around us. We see objects only when our eyes received light from the object.
To be able to see something light is essential.

Light is a form of energy which gives the sensation of vision. The branch of science
which deals with the study of light and other various activities related to light is
called optics.

Sources of Light

The bodies which give light energy are called the sources of light. They are classified
into natural sources and artificial sources.

Natural Sources

They emit light naturally. Some of the natural sources of light are the sun, moon,
stars, firefly, etc.

The Sun

The sun emits light itself. It is the most important source of light on the earth. The
light from the sun travels through the space at the speed of 3,00,000 km/s and reaches
to the earth in about 8 minutes and 20 seconds.

Firefly Sun Stars

Blooming Science & Environment Book 6 47

The Moon
The moon does not emit light itself, but it reflects the light coming from the sun. The
light from the moon is cool and pleasant.

The Stars
Eventhough the stars are bigger and brighter than the sun, they appear tiny twinkling
sources of light during night because they are very far away from us.

Firefly

During the night, we can see fireflies which emit light from their tail end, and hence
they look pretty. The light from firefly (junkiri) is not so intense that enables us to
see the objects.

Artificial Sources

Man has made several artificial sources of light so that he/she can see and work in
dark. The first man-made source of light was fire. Oil-lamps, candles, gas lamps,
electric bulbs, fluorescent lamps, etc. are some examples of man-made or artificial
sources of light. Now, the most widely used artificial source of light is electricity.

Scan for practical experiment

Burning candle Burning lamp Glowing Bulb

visit: csp.codes/c6e09

Luminous and Non-luminous objects

On the basis of emission of light objects can be divided into two groups:

a. Luminous objects and

b. Non-luminous objects

a. Luminous Objects

Luminous objects are those objects, which emit their own light. For example, the
sun, star, lighted candle, glowing bulb, etc are luminous objects. All these substances
give out their own light. Sun is the natural source of light. It emits its own light. Even
though it is very far from us, still it gives light and heat. Star has also got its own
source of energy to emit light. At night time, stars are visible to us as small twinkling
dots. The other like glowing bulbs, matches,etc. are artificial sources of light. They
are man-made so they are called artificial sources of light.

48 Blooming Science & Environment Book 6

Sun Stars Candles Bulb

b. Non-luminous Objects

Non-luminous objects are those objects, which do not emit their own light. Such as
moon, chair desks, books, pens and clothes etc are non-luminous sources. Moon is a
non-luminous object. But we all know that at night moon emits light. Well, then how
does it emit light? The moonlight, which we actually receive, is the reflected light of
sun. The non-luminous objects are seen in presence of light from any source.

Earth Table Pen

Activity Sun light

Place a plane mirror towards the sunlight. Mirror Fig: Mirror
reflects light in another direction. You can send
sunlight into classroom using plane mirror. Is plane
mirror a luminous body? No, it is not. It reflects
light of sun. Similarly, moon is non-luminous body.
Moon reflects sunlight towards earth.

Differences between Luminous and Non-luminous Objects

Luminous Objects Non-luminous Objects

1. Luminous objects are those objects, 1. Non-luminous objects are those objects,

which can emit their own light. which do not emit their own light.

2. For example, the sun, star, lighted 2. Such as moon, chair, desks, books, pens,
candle, glowing bulb, etc are clothes etc. are non-luminous objects.
luminous objects.

Blooming Science & Environment Book 6 49

Transparent, Translucent and Opaque Objects

Objects can be classified into three groups depending on the amount of light they
allow to pass through them. They are transparent, translucent and opaque.

Transparent Objects

Objects which allow light to pass through them easily are known as transparent
objects. Such as clear glass, water, air, thin plastic sheet, etc. are transparent objects.

Translucent Objects

Objects which allow light to pass through them partially but we cannot see clearly
through are known as translucent objects. Such as greased paper, thin polythene
sheets, tracing paper, ground glass, etc. are translucent objects.

Opaque Objects

Objects which do not allow light to pass through them at all are known as opaque
objects. Such as wood, bricks, stone, etc. are opaque objects.

Activity

Separate the following objects into transparent, translucent and opaque.

Glass piece book

Colourful polythene brick

Coloured glass oiled paper

Tracing paper table

Differences between Transparent, Translucent and Opaque Objects.

Transparent Objects Translucent Objects Opaque Objects

These are the objects These are the objects These are the objects

through which light passes through which light passes through which light does

easily and completely. partially. not pass.

We can see through them We can see partially We cannot see through
easily. through them. them.

Glass, water, air, etc. are Tracing paper, polytheneer Wood, iron, brick etc are
transparent. are translucent. opaque.

Rectilinear Propagation of Light

Light in any one medium always travels in a straight line. This phenomenon of light
is called rectilinear propagation of light.

50 Blooming Science & Environment Book 6