SCIENCE

TEXTBOOK FOR CLASS-VII

The Jammu and Kashmir

State Board of School Education
Jammu/Srinagar
Published by:
Secretary, The Jammu & Kashmir State Board of School Education, Jammu/Srinagar

Website: www.jkbose.co.in

C Copyright Reserved: The Jammu & Kashmir State Board of School Education

No Part of this publication may be stored in a retrieval system, transmitted, or reproduced in any
way, including but not limited to photocopy, photograph magnetic or other record without the prior
agreement and written permission of the copyright owner.

Disclaimer
Every effort has been made to supply complete and accurate information.
In case, there is any omission, printing mistake or any other error which might have crept in
inadvertently, neither thee compiler, publisher, printer nor any of other distributers shall take any
legal responsibility.

First Edition : March : 2012

August - 2014

Copies Obtainable from:

The J & K State Board of School Education,
Text Book Store,
Bemina, Srinagar/Rehari Colony, Jammu

FOR FREE DISTRIBUTION

Printed At: Saraswati Art Printers: 8247/2 New Anaj Mandi (Near Filmistan Cinema)
Cinema) Delhi-110006.
 FOREWORD
The days have gone when science and Technology was concerned

only with scientists. Now, everyone should understand the implications of

Science and Technology and have a say in making its right use. To develop,

what we call a scientific culture is the need of hour. A strong foundation in

science is a must to develop this culture. The major contribution of science

lies in developing scientific attitude and propensity for the exploration of the

truth. The Science Curriculum is the tool which helps the student to arrive at

the desired truth. The National Curriculum Framework -2005 (NCF - 2005),

recommends that child's life at school must be linked to its life outside the

school so that tremendous advance made in Science and Technological

literacy affect the human life qualitatively.

th
It is in this context that the present text book of science for Class 7

has been developed. I am sure that it will provide the necessary scientific

and technology literacy, encouraging students in their innovativeness and

creativity thereby enabling them to take decisions and facilitate them to

solve the problem in day to day life. As per the guidelines of NCF-2005,

Contextualization has been done with special reference to local specific

contents in the textbook.

The textbook, it is hoped, will provide our children the basic

knowledge of science and develop their scientific temperament in order to

understand and appreciate different natural phenomenon.

The BOSE gratefully acknowledges the use of material from science

textbook of Class 7th published by National Council of Education

(iii)
Research and Training (NCERT), New Delhi in preparing the text book.
While dedicating this book to the students, I thank the participants

who developed, reviewed the materials in different workshops.

I also take this opportunity to place on record my profound

appreciation to Mr. Malik Gh. Hasan, Director (Academics) JK BOSE,

and Dr. Yasir Hamid Sirwal, Academic Officer, JK BOSE for their

laudable contribution in the preparation and processing of this book.

Comments and suggestions for improvement are welcome.

Dr. Sheikh Bashir Ahmad

Chairman
Jammu & Kashmir
State Board of School Education

(iv)
 ACKNOWLEDGEMENT

At the outset it is indeed laudable to mention the assistance and

valuable inputs/contribution offered by the subject experts for framing the
present science textbook for Class VII. The contents have been developed
in a lucid and exhibitive manner to enable the students to comprehend all
the topics unambiguously.

th
It is opt to record that while dedicating this textbook of Class 7 to the
pupil of State, I acknowledge with gratitude the contribution made by the
experts of the subjects, and for expending their whole hearted support. They
are :

1. Mr. A.K. Sen, Ex-Director (Academics), J&K State BOSE.

2. Ms. Sushma Verma, Ex. Deputy Director (Academics)-JD , J&K State BOSE.
3. Dr. Jyoti Malhotra, Lecturer , GHSS, Rehari, Jammu .
4. Mr. Baljeet Singh, Ex. Academic Officer, J&K State BOSE.
5. Dr. Arif Jan, Academic Officer, J&K State BOSE.
6. Mr. Dinesh Kumar Mansotra, Sr. Lecturer, DIET, Samba.
7. Mr. P.D. Sharma, Sr. Lecturer, GHSS, Vijaypur, Samba.
8. Ms. Nitu Mahajan, Lecturer, GHSS, Panthal, Reasi.
9. Ms. Verinderjeet Kour, Lecturer, GHSS, Salehar, R.S. Pura, Jammu.
10. Ms. Charoo Sawhney, Lecturer, GHSS, Khour, Jammu.
11. Dr. Saima Qadir, Lecturer, GHSS, Dangarpur, Sopore, Kashmir.
12. Dr. Neelofar Jabeen, Master, GHS, Chattabal, Qamarwari, Srinagar, Kashmir.
13. Ms. Nighat Gulzar, Teacher, GHSS, Panzan, Budgam, Kashmir.
14. Mr. ShabirAhmad Sirwal , Master, Zone Kishtwar.
15. Ms. Mudasira Yaseen, Teacher, GHS(G), Zaindar Mohalla, Srinagar, Kashmir
16. Ms. Sanam Bashir, Teacher, GMS, Aloocha Bagh, Srinagar, Kashmir.
17. Mr. Ranjeet Singh Manhas, Academic Officer, J&K State BOSE.
18. Ms. Nazia Rashid Purra, Academic Officer, J&K State BOSE.
19. Mr. Naseer Ahmad, Central Academics, J&K State BOSE.
20. Mr. Jameel Ahmad, Central Academics, J&K State BOSE.

(v)
I am highly thankful to the Academic Division/CDR Wing, J and K State
BOSE for their contribution in preparing this book of Science. I also place
on record my profound appreciation for the contribution made by
Dr. Yasir Hamid Sirwal, Academic Officer, J&K State BOSE in preparing
and processing this Science textbook and making available local specific
material for the children of the state. The services of Ms. Gomti Sharma &
Ms. Sadhana (Computer Designers, Jammu) and Publication Division,
J&K State BOSE for composing, designing and printing of this textbook is
highly acknowledged.
Every effort has been made to keep this book error free. As there is
always scope for improvement, any comment and suggestion will be
gratefully acknowledged.

Malik Gh. Hasan

Director (Academics)

Jammu & Kashmir

State Board of School Education

(vi)
 CONTENTS
Foreword iii-iv

Acknowledgement v-vi

1. Nutrition in Plants 1-11

2. Nutrition in Animals 12-25

3. Fibre to Fabric 26-39

4. Heat 40-54

5. Acids, Bases and Salts 55-67

6. Physical and Chemical Changes 68-78

7. Weather, Climate and Adaptations

of Animals to Climate 79-93

8. Winds, Storms and Cyclones 94-111

9. Soil 112-125

10. Respiration in Organisms 126-140

11. Transportation in Animals 141-161

and Plants

12. Reproduction in Plants 162-181

13. Motion and Time 182-201

14. Electric Current and Circuits 202-220

15. Light 221-239

16. Water 240-260

17. Forests : Our Lifeline 261-277

18. Waste Water Story 278-290

(viii)
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

1 NUTRITION IN PLANTS

N
utrition is the fundamental life The nutrients enable living
process because all other organisms to build their bodies, to grow, to
processes stem from it. Energy repair damaged parts of their bodies and
gained through nutrition is used to provide the energy to carry out life
maintain other life processes. In Class VI processes. Nutrition is the mode of
you have learnt that food is essential for taking food by an organism and its
all living organisms. You have also learnt utilization by the body. The mode of
that carbohydrates, proteins, fats, nutrition in which organisms make food
vitamins and minerals are components of themselves from simple substances is
food. These components of food are called autotrophic (auto = self; trophos =
necessary for our body and are called nourishment) nutrition. Therefore, plants
nutrients. are called autotrophs. Animals and most
All living organisms require food. other organisms take in ready made food
Plants can make their food themselves prepared by the plants. They are called
but animals including humans cannot. heterotrophs (heteros = other).
They get it from plants or animals that eat NUTRITION
plants. Thus, humans and animals are
directly or indirectly dependent on plants.
Autotrophic Heterotrophic
Nutrition Nutrition
Yasir wants to know e.g., Green Plants e.g., all animals
how plants prepare
[Producers of food] including man
their own food.
and non-green
plants
1.1 MODE OF NUTRITION IN PLANTS
Plants are the only organisms that Saba wants to know why
can prepare food for themselves by using our body cannot make food
from carbon dioxide, water
water, carbon dioxide and minerals. and minerals like plants do
These raw materials are present in their
Now where the food factories of
surroundings.

NUTRITION IN PLANTS 1
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the plants are located: whether food is

made in all parts of plants or only in
certain parts? How do plants obtain raw Saba wants to know what is so
materials from their surroundings? How special about the leaves that they
can synthesise food but other
do they transport them to the food parts of the plant cannot.
factories of the plants?
The leaves have a green pigment
1.2 PHOTOSYNTHESIS - FOOD
called chlorophyll. It helps leaves to
MAKING PROCESS IN PLANTS
Leaves are the food factories of capture the energy of sunlight. This

plants. The synthesis of food in the plants energy is used to synthesise (prepare)

occurs in leaves. Therefore, all the raw food from carbon dioxide and water.

materials must reach there. Water and Since the synthesis of food occurs in the

minerals present in the soil are absorbed presence of sunlight, it is called

by the roots and transported to the leaves. photosynthesis (photo : light; synthesis

Carbon dioxide from air is taken in : to combine). So we find that chlorophyll,

through the pores present on the surface sunlight, carbon dioxide and water are

of the leaves. These pores are necessary to carry out the process of

surrounded by 'guard cells'. Such pores photosynthesis. It is a unique process on

are called stomata [Fig. 1.1 (c)]. the earth. The solar energy is captured by
the leaves and stored in the plant in the
form of food. Thus, sun is the ultimate
Yasir wants to know how water source of energy for all living
and minerals absorbed by roots
reach the leaves. organisms.
Can you imagine life on earth
without photosynthesis !
Water and minerals are
transported to the leaves by the vessels In the absence of photosynthesis
which run like pipes throughout the roots, there would not be any food. The survival
the stem, the branches and the leaves. of almost all living organisms directly or
They form a continuous path or passage indirectly depends upon the food made by
for the nutrients to reach the leaf. the plants. Besides, oxygen which is
essential for the survival of all living

NUTRITION IN PLANTS 2
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Besides leaves, photosynthesis also takes place in other green parts of the plant -
in green stems and green branches. The desert plants have scale or spine-like
leaves to reduce loss of water by transpiration. These plants have green stems
which carry out photosynthesis. e.g. cactus
sunlight
organisms is produced during 6CO2 + 6H2O C6H12O6 + 6O2
cholorophyll

photosynthesis. In the absence of Light energy

photosynthesis, life will be impossible on
the earth.
Chlorophyll

Carbon Chlorophyll
dioxide in leaf

Oxygen Water and

minerals

Guard cells Stoma Fig.1.2: Diagram showing

photosynthesis
(b) A section through a leaf

(a) Leaf Guard cells Yasir has observed some

plants with deep red, violet or
brown leaves. He wants to
know whether these leaves
also carry out photosynthesis.

Stomatal opening During photosynthesis, oxygen is

released. The carbohydrates ultimately
(c) Stomata
get converted into starch. The presence
Fig. 1.1
of starch in leaves indicates the
During photosynthesis, chlorophyll occurrence of photosynthesis. The starch
containing cells of leaves (Fig.1.1), in the is also a carbohydrate.
presence of sunlight, use carbon dioxide
and water to synthesise carbohydrates Activity 1.1
Take two potted plants of the same
(Fig.1.2). The process can be
kind. Keep one in the dark (or in a black
represented by an equation:

NUTRITION IN PLANTS 3
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

box) for 72 hours and the other in the Synthesis of Plant food other
sunlight. Perform iodine test with leaves than carbohydrates
of the both plants as you did in Class VI. You have just learnt that plants
Record your results. Now leave the pot synthesize carbohydrates through the
which was earlier kept in the dark, in the p r o c e s s o f p ho t os y n th e si s . T h e
sunlight for 3-4 days and perform the carbohydrates are made of carbon,
iodine test again on its leaves. Record hydrogen and oxygen. These are used to
your observations in your notebook. synthesize other components of food
The leaves other than green also such as proteins and fats. But proteins are
have chlorophyll. The large amount of nitrogenous substances which contain
red, brown and other pigments mask the nitrogen. From where do the plants obtain
green colour (Fig.1.3). Photosynthesis nitrogen?
takes place in these leaves also. Recall that nitrogen is present in
abundance in gaseous form in the air.
However, plants cannot absorb nitrogen
in this form. Soil has certain bacteria that
convert gaseous nitrogen into a usable
form and release it into the soil. These
soluble forms are absorbed by the plants
along with water. Also, you might have
seen farmers adding fertilizers rich in
Fig.1.3: Leaves of various colours nitrogen to the soil. In this way the plants
fulfil their requirements of nitrogen along
You often see slimy, green patches
with the other constituents. Plants can
in ponds or in other stagnant water
then synthesize components of food
bodies. These are generally formed by
other than carbohydrates such as
the growth of organisms called algae.
proteins and fats.
Can you guess why is algae green in
1.3 OTHER MODES OF NUTRITION IN
colour? They contain chlorophyll which PLANTS
gives them the green colour. Algae can There are some plants which do
also prepare their own food by not have chlorophyll. They cannot
photosynthesis. synthesize their food. How do they

NUTRITION IN PLANTS 4
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

survive and from where do they derive about it and discuss with your teacher.
nutrition? Like humans and animals such
plants depend on the food produced by Saba wants to know whether
the other plants. They use the mosquitoes, bed bugs, lice and
leeches that suck our blood are
heterotrophic mode of nutrition. Look at also parasites.
Fig.1.4. Do you see yellow tubular
structures twining around the stem and Have you seen or heard of plants
branches of a tree? This is a plant called that can eat animals? There are a few
Cuscuta (Amarbel). It does not contain plants which can trap insects and digest
chlorophyll. It takes ready made food from them. Is it not amazing? Such plants may
the plant on which it is climbing. be green or of some other colour. Look at
the plant in Fig.1.5. The pitcher-like
structure is the modified part of the leaf.
The apex of the leaf forms a lid which can
open or close the mouth of pitcher. Inside
the pitcher there are hair which are
directed downwards. When an insect
lands in the pitcher, the lid closes and the
trapped insect is digested by the digestive
juices secreted in the pitcher. Such
in sect-eating plan ts are called
insectivorous plants.
It is possible that such plants do
not get all the required nutrients from the
soil in which they grow?
Fig.1.4: Cuscuta (Amarbel) on host plant

The plant on which they climb is Yasir is confused. If the

pitcher plant is green and
called a host. Since it deprives the host of carries out photosynthesis, then
valuable nutrients, it is called a parasite. why does it feed on insects?

Are we and the other animals also

parasites on the plants? You should think

NUTRITION IN PLANTS 5
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Lid You may have also seen fluffy umbrella-

like patches growing on rotting wood
during the rainy season (Fig.1.6). Let us
find out what type of nutrients they need to
survive and from where they get them.

Activity 1.2
Take a piece of bread and moisten
it with water. Leave it in a moist warm
place for 2-3 days or until fluffy patches
Leaf modified appear on it (Fig.1.7). These patches may
into pitcher
Fig.1.5: Pitcher plant showing lid and pitcher be white, green, brown or of any other
colour. Observe the patches under a
1.4 SAPROTROPHS microscope or a magnifying glass.
You might have seen packets of
mushrooms sold in the vegetable market.

Fig.1.7: Fungi
growing on bread

Write down your observation in your

Fig.1.6: Packet of mushrooms, a mushroom
growing on decayed material notebook. Most probably you will see
cotton like thread spread on the piece of
bread.
Yasir wants to know how
These organisms are called fungi.
these organisms acquire
nutrients. They do not have They have a different mode of nutrition.
mouths like animals do. They are They secrete digestive juice on the dead
not like green plants as they lack
chlorophyll and cannot make food and decaying matter and convert it into a
by photosynthesis. solution. Then they absorb the nutrients
from it. This mode of nutrition in which

NUTRITION IN PLANTS 6
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

organisms take in nutrients in solution present in the air. When they land on wet
form from dead and decaying matter is and warm things, they germinate and
called saprotrophic nutrition. Plants grow. Now, can you figure out how we can
which use saprotrophic mode of nutrition protect our things from getting spoiled?
are called saprotrophs. Some organisms live together and
Fungi also grow on pickles, share shelter and nutrients. This is called
leather, clothes and other articles that are symbiotic relationship. For example,
left in hot and humid weather for long certain fungi live in roots of trees. The tree
time. provides nutrients to the fungus and, in
return, receives help from it to take up
Saba is keen to know
water and nutrients from the soil. This
whether her beautiful shoes,
which she wore on special association is very important for the tree.
occasions, were spoiled by fungi
In organisms called lichens, a
during the rainy season .She
wants to know how fungi appear chlorophyll-containing partner, which is
suddenly during the rainy
season. an alga and a fungus live together. The
fungus provides shelter, water and
minerals to the alga and in return, the alga
provides food which it prepares by
Yasir says once his photosynthesis.
grandfather told him that his
wheat fields were spoiled by a
fungus. He wants to know if 1.5 HOW NUTRIENTS ARE
fungi cause diseases also.
REPLENISHED IN THE SOIL
Saba told him that many fungi Have you seen farmers spreading
like yeast and mushrooms are
useful ,but some fungi manure or fertilizers in the field, or
cause diseases in plants, gardeners using them in lawns or in pots?
animals and humans .
Some fungi are also used Do you know why they are added to the
in medicines.
soil?
You learnt that plants absorb
mineral nutrients from the soil. So, their
During the rainy season they spoil amount in the soil keep on declining.
many things. Ask your parents about the Fertilizers and manures contain plant
menace of fungi in your house. nutrients such as nitrogen, potassium,
The fungal spores are generally

NUTRITION IN PLANTS 7
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

phosphorus, etc. These nutrients need to association is of great significance for the
be added from time to time to enrich the farmers. They do not need to add nitrogen
soil. We can grow plants and keep them fertilizers to the soil in which leguminous
healthy if we fulfil the nutrient requirement plants are grown.
of plants. In this chapter you learnt that most of the
Usually crops require a lot of plants are autotrophs. Only a few plants
nitrogen to make proteins. After the adopt other modes of nutrition like
harvest, the soil becomes deficient in parasitic and saprotrophic. They derive
nitrogen. You learnt that though nitrogen nutrition from other organisms. All
gas is available in plenty in the air, plants animals are categorised as heterotrophs
cannot use it in the manner they can use since they depend on plants and other
carbon dioxide. They need nitrogen in a animals for food. Can we say that the
soluble form. The bacterium called i ns ect i vor o u s pl an t s a re p a rt i al
Rhizobium can take atmospheric nitrogen heterotrophs ?
and convert it into soluble form. But
Rhizobium cannot make its own food. So
it lives in the roots of grams, peas, moong,
beans and other legumes and provides
them with nitrogen. Most of the pulses
(dals) are obtained from leguminous
plants. In return, the plants provide food
and shelter to the bacteria. They thus,
have a symbiotic relationship. This

Autotrophic Insectivorous Photosynthesis

Chlorophyll Nutrient Saprotrophs
Heterotrophs Nutrition Saprotrophic
Host Parasite Stomata

NUTRITION IN PLANTS 8
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

What you have learnt

§ All organisms take food and utilize it to get energy for growth and maintenance of their bodies.
§ Green plants synthesise their food themselves by the process of photosynthesis. They are
autotrophs.
§ Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of
food.
§ Chlorophyll and sunlight are the essential requirements for photosynthesis.
§ Complex chemical substances such as carbohydrates are the products of photosynthesis.
§ Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
§ Oxygen is produced during photosynthesis .
§ Oxygen released in photosynthesis is utilized by living organisms for their survival.
§ Fungus derive nutrition from dead, decaying matter. They are saprotrophs. Plants like Cuscuta are
parasites. They take food from the host plant.
§ A few plants and all animals are dependent on others for their nutrition and are called heterotrophs.

EXERCISES
1. Why do organisms need to take food?
2. Distinguish between a parasite and a saprotroph?
3. How would you test the presence of starch in leaves?
4. Give a brief description of the process of synthesis of food in green plants?
5. Show with the help of a sketch that the plants are the ultimate source of food.
6. Fill in the blanks:
(a) Green plants are called ................since they synthesis their own food.
(b) The food synthesized by the plants is stored as ................ .
(c) In photosynthesis solar energy is captured by the pigment called ................. .
(d) During photosynthesis, plants take in ...............and release.............. .
7. Name the following :
(I) A parasitic plant with yellow, slender and tubular stem.
(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.
(iii) The pores through which leaves exchange gases.
8. Tick the correct answer:
(a) Amarbel is an example of:

NUTRITION IN PLANTS 9
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(i) Autotroph (ii) Parasite (iii) Saprotroph (iv) Host

(b) The plant which traps and feeds on insects is:
(I) Cuscuta (ii) China rose (iii) Pitcher plant (iv) Rose
9. Match the items in Column I with those in Column II:
Column I Column II
Chlorophyll Bacteria
Nitrogen Heterotrophs
Amarbel Pitcher plant
Animals Leaf
Insects Parasites
10. Mark 'T' if the statement is true and 'F' if it is false:
(i) Carbon dioxide is released during photosynthesis. (T/F)
(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)
(iii) The product of photosynthesis is not a protein. (T/F)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
11. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for photosynthesis?
(i) Root hair (ii) Stomata (iii) Leaf veins (iv) Sepals
12. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) Roots (ii) Stem (iii) Flower (iv) Leaves
13. Tick Mark (ü) the Correct Choice :
(i) Which one of the following is an insectivorous plant?
(a) Lichen (b) Venus fly trap (c) Mushrooms (d) Yeast
(ii) Two different organisms living together and both benefitting from each other, are known as
(a) Saprophytic (b) Symbiotic (c) Parasitic (d) Heterotrophs
(iii) Tiny pores on the surface of leaves are
(a) Lamina (b) Stomata (c) Chlorophyll (d) Leaf scale
(iv) Which of the following is the green colour pigment in leaves:
(a) Protoplast (b) Chloroplast (c) Chlorophyll (d) Anthocyanin

NUTRITION IN PLANTS 10
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Extended Learning - Activities and Projects

1. Project
Take a potted plant with broad leaves. Take two strips
of black paper and cut out a small square in their
centres. Cover a part of two leaves with these papers
and secure them with paper clips (Fig 1.8).Keep the
plant in the sunlight for 2-5 days. Observe the
difference in the colour of the covered and the
uncovered portions on the one leaf. Perform iodine Fig.1.8: Experiment to test the
test on this leaf. occurance of photosynthesis
Did the two parts show any difference in results? Now take second leaf. Remove the strip and
expose the covered part to the sunlight for 2-3 days and do the iodine test again. Describe your
observations.
2. Visit a green house if there is one near your place. Observe how they raise plants. Find out
how they regulate the amount of light, water and carbon dioxide to grow the plants.
3. Try growing a sweet potato just in water. Describe your experiment and observations.
You can read more on the following website:
Www.phschool.com/science/biology_place/biocoach/photosynth/overview.htm

DO YOU KNOW?
Light is so important for plants that their leaves grow in many patterns so
as to catch the most sunlight.

NUTRITION IN PLANTS 11
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2 NUTRITION IN ANIMALS

N
utrition in animals is altogether simpler substances is called digestion.
different from plants as plants 2.1 DIFFERENT WAYS OF TAKING FOOD
can prepare their own food by The mode of taking food into the body
the process of photosynthesis but varies in different organisms. Bees and
animals cannot. Animals get food from humming-birds suck the nectar of plants,
plants, either directly by eating plants or infants of human and many other animals
indirectly by eating animals that eat feed on mother's milk. Snakes like the
plants. Some animals eat both plants and python swallow the animals they prey
animals. Recall that all organisms upon. Some aquatic organisms filter tiny
including humans require food for growth, food particles floating nearby and feed
repair and functioning of the body. upon them.
Animal nutrition includes nutrients Activity 2.1
requirement, mode of intake of food What is the type of food and mode

and its utilization in the body. of feeding of the following animals? Write
You have studied in class VI that down your observations in the given
food consists of many components. Try to table. You may find the list of modes of
recall and list them below: feeding given below in the table helpful.
1. ____________________
2. ____________________
3. ____________________ Table 2.1: Various modes of feeding
4. ____________________ Name of Kind of Mode of
animal food feeding
5. ____________________ Snail
6. ____________________ Ant
The components such as Eagle
carbohydrates are complex substances. Humming-bird
These complex substances cannot be Lice
utilized as such. So they are broken down Mosquito
Butterfly
into simpler substances. The breakdown
House fly
of complex components of food into

NUTRITION IN ANIMALS 12
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(Scraping, Chewing, Siphoning, Capturing buccal cavity (2) food pipe or

and Swallowing, Sponging, Sucking etc.) oesophagus (3) stomach (4) small
intestine (5) large intestine ending in
Amazing fact the rectum and (6) the anus. Is it not a
Starfish feeds on animals covered by very long path ? These parts together
hard shells of calcium carbonate. form the alimentary canal (digestive
After opening the shell, the starfish tract). The food components gradually
pops out its stomach through its
get digested as food travels through the
mouth to eat the soft animal inside
the shell. The stomach then goes back compartments of the alimentary canal.
into the body and the food is slowly
digested.

Buccal cavity
Mouth
Salivary gland
Oesophagus

Fig.2.1: Starfish

2.2 DIGESTION IN HUMANS Liver

Stomach
We take in food through the mouth, Gall bladder

digest and utilize it. The unused parts of

the food are defecated. Have you ever Pancreas

wondered what happens to the food

Small
inside the body? The food passes through intestine
a continuous canal called alimentary Large
intestine
canal (Fig. 2.2) which begins at the
buccal cavity and ends at the anus. Appendix Rectum
Anus
The canal can be divided into various
Fig.2.2: Human digestive system
compartments: (1) the mouth or the The inner walls of the stomach, the small

NUTRITION IN ANIMALS 13
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Milk teeth and permanent teeth

The milk set contains 20 teeth whereas permanent set consists of 32 teeth. Do you
remember about falling of your teeth some years ago? The first set of teeth grows
during infancy and they fall off at the age between six to eight years. These are termed
as milk teeth. The second set that replaces them are the permanent teeth. The
permanent teeth may last throughout life or fall off during old age or due to some dental
disease. The teeth that appear in two sets are described as diphydont.
intestine and the various glands, down mechanically into small pieces.
associated with canal such as salivary Each tooth is rooted in the separate
glands, the liver and the pancreas socket in the gums. Such embedded
secrete digestive juices. The digestive teeth are called thecodont (Fig. 2.3). Our
juices convert complex substances of teeth vary in appearance and perform
food into simpler ones. The digestive tract different function. Accordingly they have
and the associated glands together different names (Fig. 2.3).
constitute the digestive system.
Now, let us know what happens to
the food in different parts of the digestive Molar
tract.

Yasir is fascinated by the

highly coiled small intestine seen Premolar
in Fig 2.2 . He wants to known its
length. Would you like to make a
wild guess? We have given its
approximate length on page 17.
Just imagine how such a long
Canine
structure is accommodated in a
small space within our body !

The Mouth and Buccal Cavity Incisor

Food is taken into body through

the mouth. The process of taking of food
into the body is called ingestion. We
Fig.2.3: Arrangement of teeth and different
chew the food with our teeth and break it type of teeth

NUTRITION IN ANIMALS 14
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 2.2 a change in colour in the test tubes?

Wash your hands. Look into the Discuss the result with your classmates
mirror and count your teeth . Use your and your teacher. The saliva breaks
finger to feel the teeth. How many kinds of down the starch into sugars.
teeth could you find? Take a piece of an
apple or bread and eat it . Which teeth do
you use for biting and cutting, and which
ones for piercing and tearing? Also find
out the ones that are used for chewing
and grinding ?
Record your observations in Table 2.2

Table2.2
Iodine solution
Type of teeth Number of teeth Total
Lower jaw Upper jaw
Cutting and
biting teeth
Water
Piercing and
tearing teeth
Chewing and Boiled rice
grinding teeth
A Boiled and chewed rice B
Fig.2.4: Effect of saliva on starch
Our mouth has the salivary glands
which secrete saliva. Do you know the The tongue is a fleshy muscular
action of saliva on food? Let us find out. organ attached at the back to the floor of
buccal cavity. It is free in the front and can
Activity 2.3 be moved in all directions. Do you know
Take two test tubes. Label them 'A' the function of the tongue? We use our
and 'B'. In test tube ‘A' put one tongue for talking.
teaspoonful of boiled rice; in test tube 'B'
keep one teaspoonful of boiled rice after
chewing it for 3-5 minutes. Add 3-4ml of
water in both the test tubes (Fig. 2.4).
Now pour 2-3 drops of iodine solution in
Fig.2.5: Regions of the
each test tube and observe. Why is there tongue for different tastes

NUTRITION IN ANIMALS 15
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Sweets and tooth decay

Normally bacteria are present in our mouth but they are not
harmful to us. However, if we do not clean our teeth and mouth after
eating, many harmful bacteria also begin to live and grow in it. These (a)
bacteria break down the sugars present from the leftover food and
release acids (see Chapter 5 to know what an acid is). The acids
gradually damage the teeth (Fig. 2.6).This is called tooth decay. If it is
not treated in time, it causes severe toothache and in extreme cases (b)
results in tooth loss. Chocolates, sweets, soft drinks and other sugar
products are the major culprits of tooth decay.
Therefore, one should clean the teeth with a brush or datun and
(c)
dental floss (a special strong thread which is moved between two
teeth to take out trapped food particles) at least twice a day and
rinse the mouth after every meal. Also, one should not put dirty
fingers or any unwashed object in the mouth. We should get our teeth (d)
checked by a dentist every six months. Fig.2.6: Gradual decay of tooth
Sometimes when you eat in a hurry, talk or laugh while eating you may cough,
get hiccups or a choking sensation. This happens when food particles enter the
windpipe. The windpipe carries air from the nostrils to the lungs. It runs adjacent to the
food pipe. But inside the throat, air and food share a common passage. Then how is
food prevented from entering the windpipe? During the act of swallowing a flap like
valve closes the passage of the windpipe and guides the food into the food pipe. If by
chance food particles enter the windpipe, we feel chocked, get hiccups or cough.
Besides, it mixes saliva with the food Activity 2.4
during chewing and helps in swallowing 1. Prepare a separate sample each of
food. We also taste food with our tongue. (i) sugar solution (ii) common salt
It has taste buds that detect different solution (iii) lemon juice and (iv) juice
tastes of food. We can find out the position of crushed neem leaf or bitter gourd.
of different taste buds by the following 2. Blindfold one of your classmates and

activity. ask her/him to take out the tongue and

keep it in straight and flat position.

NUTRITION IN ANIMALS 16
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

3. Use a clean toothpick to put the above Look at Fig.2.2. The food-pipe
samples one by one on different areas runs along the neck and the chest. Food
of the tongue as shown in Fig. 2.5. is pushed by movement of the walls of the
Use a new toothpick for each sample. food-pipe. Actually this movement takes
4. Ask the classmate which areas of the place throughout the alimentary canal
tongue could detect the sweet, salty, and pushes the food downwards (Fig
sour and bitter substances. 2.7). At times the food is not accepted by
5. Now write down your observations our stomach and is vomited out. Recall
and label Fig 2.6. the instances when you vomited after
Repeat this activity with other
eating and think of the reason for it.
classmates.
Discuss with your parents and teacher.
The Food Pipe / Oesophagus
The passage of food back into buccal is
The swallowed food passes into
called regurgitation.
the food-pipe or oesophagus.
The Stomach
The stomach is a thick-walled
Saba wants to know how
food moves in the opposite bag. Its shape is like a flattened U and it is
direction during vomiting.
the widest part of the alimentary canal. It
receives the food-pipe at one end and
opens into the small intestine at the other.
The inner lining of the stomach
Food
secretes mucous, hydrochloric acid (HCl)
and digestive juices. The mucous
Oesophagus protects the lining of the stomach. The
acid kills many bacteria that enter along
with the food and makes the medium in
Stomach the stomach acidic and helps the
digestive juices to act. The digestive
juices break down the proteins into
simpler substances.
Fig.2.7: Movement of the
food in the oesophagus The Small Intestine
of the alimentary canal The small intestine is highly coiled
and about 7.5 metres long. It receives

NUTRITION IN ANIMALS 17
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

secretions from liver and pancreas. into simple sugars as glucose, fats into
Besides, its wall also secretes juices. fatty acids and glycerol, and proteins into
The liver is reddish brown gland amino acids.
situated in the upper part of the abdomen Absorption in the small intestine
on the right side. It is the largest gland in The digested food can now pass
the body. It secretes bile juice that is into the blood vessels in the wall of
stored in a sac called gall bladder (Fig. intestine. This process is called
2.2). The bile juice plays an important role absorption. The inner walls of the small
in digestion of fats. intestine have thousands of finger-like
The pancreas is a large cream outgrowths called villi (singular villus).
coloured gland located just below the Can you guess what the role of villi could
stomach (Fig 2.2). Pancreatic juice acts be in intestine? The villi increase the
on carbohydrates which get broken down surface area for absorption of digested

The working of the stomach was

discovered by a strange accident . In 1882, a
man named Alexis St. Martin was badly hit by
a shot gun. The bullet had seriously damaged
the chest wall and made a hole in his
stomach. He was brought to an American
army doctor William Beaumont. The doctor
saved the patient but he could not close the
wound properly and left it bandaged (Fig.2.8)
Beaumont took it as a great opportunity to see
the inside of stomach through the hole. He Fig.2.8: Alexis St. Martin's
shotgun wound
made some wonderful observations.

Beaumont found that the stomach was churning food. Its wall secreted a
fluid which could digest the food. He also observed that the end of the
stomach opens into the intestine only after the digestion of the food inside
the stomach is completed.

NUTRITION IN ANIMALS 18
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

food. Each villus has a network of thin and DIGESTION

small blood vessels close to its surface. The breakdown of ingested food (in
mouth cavity, stomach and small
The surface of the villi absorbs the
intestine)
digestive food materials. The absorbed
substances are transported via the blood $
vessels to different organs of the body ABSORPTION
where they are used to build complex Digested food is absorbed through
membranes into various organs (in
substances such as the proteins required small intestine; large intestine absorbs
by the body. This is called assimilation. only water)

$
In the cells, glucose breaks down with the
help of oxygen into carbon dioxide and
ASSIMILATION
water, and energy is released. The food
Absorbed food is incorporated into cell
that remains undigested and unabsorbed components
enters into the large intestine.
$
Large Intestine EGESTION for defecation
The large intestine is wider and shorter Undigested food is excreted out.
than small intestine. It is about 1.5 metre (through anus)

in length. Its function is to absorb water

2.3 DIGESTION IN GRASS-EATING
and some salts from the undigested food ANIMALS
material. The remaining waste passes Have you observed cows, buffaloes and
into the rectum and remains there as other grass-eating animals chewing
semi-solid faeces. The faecal matter is continuously even when they are not
removed through the anus from time-to- eating? Actually, they quickly swallow the
time. This is called egestion. grass and store it in a part of the stomach
called rumen (Fig. 2.9). Here the food
Summary of various steps in the
gets partially digested and is called cud.
process of digestion.
INGESTION But later the cud returns to the mouth in
Taking in of food directly or indirectly small lumps and the animal chew it. This
from plants (through mouth) process is called rumination and these

$ animals are called ruminants.

NUTRITION IN ANIMALS 19
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Diarrhoea

Sometime you may have experienced the need to pass watery stool frequently.
This condition is known as diarrhoea. It may be caused by an infection, food
poisoning or indigestion. It is very common in India, particularly among children.
Under severe conditions it can be fatal. This is because of the excessive loss of water
and salts from the body. Diarrhoea should not be neglected. Even before a doctor is
consulted the patient should be given plenty of boiled and cooled water with a pinch of
salt and sugar dissolved in it. This is called Oral Rehydration Solution (ORS).

The grass is rich in cellulose, a type of

Saba wants to know why
these animals cannot chew carbohydrate. Many animals, including
food properly at the time they humans, cannot digest cellulose.
take it in?
Ruminants have a large sac-like
structure called Caecum between the
Yasir wants to know why small intestine and large intestine (Fig.
we cannot digest cellulose
like the cattle do.
2.9). The cellulose of the food is
digested here by the action of certain
bacteria which are not present in
Oesophagus
Small Intestine humans.
Rumen So far you have learnt about
animals which possess the digestive
system. But there are many small
organisms which do not have a mouth
and a digestive system. Then, how do
they acquire and digest food? In the
section below you will learn another
Stomach Large Intestine interesting way of food intake.
2.4 FEEDING AND DI GESTION IN
Caecum
AMOEBA (Unicellular Organism)
Fig.2.9: Digestive system of ruminant Amoeba is a microscopic single-
celled organism found in pond water.

NUTRITION IN ANIMALS 20
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Amoeba has a cell membrane, a rounded, the food particle and engulfs it. The food
dense nucleus and many small bubble- becomes trapped in a food vacuole
like vacuoles (Fig. 2.10) in its cytoplasm. (Fig. 2.10).
Amoeba constantly changes its shape Digestive juices are secreted into
and position. It pushes out one, or more the food vacuole. They act on the food
finger-like projections, called pseudo and break it down into simpler
podia or false foot for movement and substances. Gradually the digested
capture of food. food is absorbed. The absorbed
Amoeba feeds on some substances are used for growth,
microscopic organisms. When it senses maintenance and multiplication. The
food, it pushes out pseudo podia around undigested residue of the food is
expelled outside by the vacuole.
Nucleus
The basic process of digestion of
Pseudopodium
food and release of energy is the same
Food particle
(ingestion) in all animals. In the later chapter you
will learn about the transport of food
absorbed by the intestine to the various
Food vacuole
parts of the body.

Fig.2.10: Amoeba Egested waste

Absorption Fatty acid Oesophagus

Amino acid Food vacuole Pancreas
Amoeba Gall bladder Premolar
Assimilation Glycerol Pseudopodia
Bile Incisor Rumen
Buccal Cavity Ingestion Ruminant
Canine Liver Rumination
Cellulose Milk teeth Salivary glands
Digestion Molar Villi
Egestion Permanent teeth Saliva

NUTRITION IN ANIMALS 21
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

What you have learnt

l Animal nutrition includes nutrients requirement, mode of intake of food and its utilization in the body.
l The human digestive system consists of the alimentary canal and secretary glands. Former
consists of (i) buccal cavity, (ii) oesophagus, (iii) stomach, (iv) small intestine, (v) large intestine
ending in the rectum and (vi) the anus. The main digestive glands which secretes digestive juices
are (i) the salivary gland, (ii) the liver and (iii) pancreas. The stomach wall and the small intestine
also secrete digestive juices.
l The modes of feeding vary in different organisms.
l Nutrition is a complex process involving: (i) ingestion, (ii) digestion, (iii) absorption, (iv) assimilation
and (v) egestion.
l Digestion of carbohydrates, like starch begins in the buccal cavity. The digestion of proteins starts in
the stomach. The bile secreted from the liver, the pancreatic juice from the pancreas and the
digestive juice from the intestinal wall complete the digestion of all components of food in the small
intestine. The digested food is absorbed in the blood vessels from the small intestine.
l The absorbed substances are transported to different parts of the body. Water and some salts are
absorbed from the undigested food in the large intestine.
l The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.
l The grazing animals like cows, buffaloes and deer are known as ruminants. They quickly ingest,
swallow their leafy food and store it in the rumen. Later, the food returns to the mouth and the
animals chew it peacefully.
l Amoeba ingests its food with the help of its false feet or pseudopodia. The food is digested in the
food vacuole.

EXERCISES
1. Fill in the blanks:
(a) The main steps of nutrition in humans are __________, __________,
__________, __________ and __________.
(b) The largest gland in the human body is __________.
(c) The stomach releases hydrochloric acid and __________ juice which act on
food.
(d) The inner wall of the small intestine has many finger-like outgrowths called
__________.
(e) Amoeba digests its food in the __________.
2. Mark "T" if the statement is true and "F" if it is false:
(a) Digestion of starch starts in the stomach. (T/F)
(b) The tongue helps in mixing food with saliva. (T/F)
(c) The gall bladder temporarily stores bile. (T/F)

NUTRITION IN ANIMALS 22
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(d). The ruminants bring back swallowed grass into their mouth and chew it for
sometime. (T/F)
3. Tick mark (ü) the correct answer in each of the following:
(a) Fats are completely digested in the
(i) Stomach (ii) Mouth (iii) Small intestine (iv) Large intestine
(b) Water from the undigested food is absorbed mainly in the
(i) Stomach (ii) Food pipe (iii) Small intestine (iv) Large intestine
(c) The process of taking food into the body is called
(i) Digestion (ii) Absorption (iii) Ingestion (iv) Assimilation
(d) Which of the following is the largest gland in human body
(i) Pancreas (ii) Liver (iii) Salivary gland (iv) Thyroid
(e) Finger like projections called villi are present in
(i) Small intestine (ii) Stomach (iii) Rectum (iv) Large intestine
(f) Which of the following is a ruminant
(i) Amoeba (ii) Man (iii) Cow (iv) Earthworm
4. Match the items of Column I with those of Column II:
Column I Column II
Food Components Product(s) of digestion
Carbohydrates Fatty acids and glycerol
Proteins Sugar
Fats Amino Acids
5. What are villi ? What is their location and function?
6. Where is the bile produced? Which component of the food does it help to digest?
7. Name the type of carbohydrates that can be digested by ruminants but not by
humans. Give the reason also.
8. Why do we get instant energy from glucose?
9. Which part of the digestive canal is involved in:
(i). Absorption of food _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(ii). Chewing of food _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(iii). Killing of bacteria _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(iv). Complete digestion of food _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(v). Formation of faeces _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
10. Write one similarity and one difference between the nutrition in amoeba and human

NUTRITION IN ANIMALS 23
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

beings.
11. Match the items of Column I with suitable items of Column II:
Column I Column II
(a) Salivary gland i. Bile juice secretion
(b) Stomach ii. Storage of undigested food
(c) Liver iii. Saliva secretion
(d) Rectum iv. Acid release
(e) Small intestine v. Digestion is completed
(f) Large intestine vi. Absorption of water

12. Label Fig. 2.11 of the digestive system.

Fig.2.11: A part of human digestive system

13. Can we survive only on raw, leafy vegetables/grass? Discuss?

NUTRITION IN ANIMALS 24
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Extended Learning - Activities and Project

1. Visit a doctor and find out:
i. Under what conditions does a patient need to be on a drip of glucose?
ii. For how long does a patient need to be given glucose?
iii. How does glucose help the patient to recover ?
Write the answers in your notebook.
2. Find out what vitamins are and get the following information.
i. Why are vitamins necessary in our diet?
ii. Which fruit or vegetables should be eaten regularly to get vitamins?
Write a one-page note on the information collected by you.
You may take help of a doctor, a dietician, your teacher or any other person, or from
any other source.

S.No Age at which Age at which No. of teeth No. of teeth

first tooth fell last tooth fell lost replaced
1.
2.
3.
4.
5.

Find out from at least twenty children, the average age at which children lose their milk
teeth. You may take help of your friends.
You can read more on the following website:
www.health,howstuffworks.com/admn-200112.htm

DO YOU KNOW?
Fats in goat's milk are much simpler than those in cow's milk. Therefore, the goat's
milk is much easier to digest than the cow's milk.

NUTRITION IN ANIMALS 25
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

3 FIBRE TO FABRIC

B
esides milk, meat, eggs some Activity 3.1
fibers are also obtained from Feel the hair on your body and arms
animals. Wool is obtained from and those on your head. Do you find any
the fleece (hair) of sheep or yak. Silk difference? Which one seems coarse and
fibres come from cocoons of the silk which one is soft?
moth. Do you know which part of the Like us, the hairy skin of the sheep
sheep's body yields fibres? Are you has two types of fibres that form its fleece:
aware how these fibres are converted (i) the coarse beard hair, and (ii) the fine
into the woollen yarn that we buy from the soft under-hair close to the skin. The fine
market to knit sweaters? Do you have any hair provide the fibres for making wool.
idea how silk fibres are made into silk, Some breeds of sheep possess only fine
which is woven into saris? under - hair. Their parents are specially
In this chapter we shall try to find chosen to give birth to sheep which have
answers to these questions. only soft under-hair. This process of
selecting parents for obtaining special
Animal Fibres - Wool and Silk characters in their offspring, such as soft
under - hair in sheep, is termed 'selective
3.1 WOOL breeding'.
Wool comes from sheep, goat, yak
and some other animals. These wool-
yielding animals bear hair on their body.
Do you know why these animals have a
thick coat of hair? Hair trap a lot of air. Air
is a poor conductor of heat, as you would
learn in Chapter 4. So, hair keeps these
animals warm. Wool is derived from
these hairy fibres.

Fig.3.1: Sheep with thick growth of hair

FIBRE TO FABRIC 26
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Animals that yield wool Wool is also obtained from goat hair
Several breeds of sheep are found (Fig.3.4). The under - hair in Kashmiri goat
in different parts of our country (Table is soft. It is woven into fine shawls called
3.1). However, the fleece of sheep is not Pashmina shawls.
the only source of wool, though wool The fur (hair) on the body of camels
commonly available in the market is is also used as wool (Fig.3.5). Llama and
sheep wool (Fig.3.1). Yak (Fig.3.2) wool Alpaca, found in South America, also yield
is common in Tibet and Ladakh. Angora wool (Fig. 3.6) and (Fig. 3.7).
wool is obtained from Angora goats,
(Fig.3.3) found in hilly regions such as Activity 3.2
Collect pictures of animals whose
Jammu and Kashmir.
hair is used as wool. Stick them in your
Famous Goats of J&K State.
scrap book. If you are unable to get
1. Pashmina Goat - Found in Ladakh
pictures, try and draw them from the ones
2. Swiss-Alpine and Jakhrana Goats -
given in this book. Find out words for
Found in Kashmir
sheep, goat, camel, and yak in your local
3. Bedal Goat - Found in Jammu.
language and also in other languages of

Fig.3.3: Angora goat

Fig.3.4: Goat

Fig .3.2: Yak

Fig.3.7: Alpaca

Fig.3.5: Camel
Fig.3.6: Llama

FIBRE TO FABRIC 27
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

our country. sheep, rearers also feed them on a mixture

of pulses, corn, jowar, oil cakes (material
Activity 3.3 left after taking out oil from seeds) and
Procure outline maps of India and minerals. In winter, sheep are kept indoors
the world. Find out and mark the places and fed on leaves, grain and dry fodder.
on the map where you find animals that
provide wool. Breeds of Sheep found in J&K State?
Use different colours to denote the 1. Gaddi - Found in Kishtwar,
Bhadarwah.
location for different wool yielding 2. Bakarwal - All over State
animals. 3. Poonchi - Found in Poonch , Rajouri
4. Karnah - Found in Karnah ( Tehsil in
From fibres to wool North Kashmir)
For obtaining wool, sheep are 5.Gurez - Found in Gurez area of
Northern Kashmir
reared. Their hair is cut and processed
6.Changthangi - Found in Changthang
into wool. Let us learn about this process. region of Ladakh.

Rearing and Breeding of sheep: If Certain breeds of sheep have thick

you travel to the hills in Jammu & coat of hair on their body which yields good
K a s h m i r, Himachal Pradesh, quality wool in large quantities. As
Uttaranchal, Arunachal Pradesh and mentioned earlier, these sheep are
Sikkim, or the plains of Haryana, Punjab, "selectively bred" with one parent being a
Rajasthan and Gujarat, you can see sheep of good breed.
shepherds taking their herds of sheep for Once the reared sheep have
grazing. Sheep are herbivores and prefer developed a thick growth of hair, hair is
grass and leaves. Apart from grazing shaved off for getting wool.

Table 3.1: Some Indian breeds of sheep

S.No Name of breed Quality of wool State where found
1. Lohi Good quality wool Rajasthan, Punjab
2. Rampur bushair Brown fleece Uttar Pradesh, Himachal Pradesh
3. Nali Carpet Wool Rajasthan, Haryana, Punjab
4. Bakarwal For woollen shawls Jammu and Kashmir
5. Marwari Coarse wool Gujarat
6. Patanwadi For hosiery Gujarat

FIBRE TO FABRIC 28
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

hurt the sheep just as it does not hurt when

Processing fibres into wool you get a hair cut or your father shaves his
The wool which is used for knitting beard. Do you know why? The uppermost
sweaters or for weaving shawls is the layer of the skin is dead. Also, the hair of
finished product of a long process, which sheep grow again just, as your hair does.
involves the following steps: Step II : The sheared skin with hair is
Step I: The fleece of the sheep along with thoroughly washed in tanks to remove
a thin layer of skin is removed from its grease, dust and dirt. This is called
body [Fig.3.8(a)]. This process is called scouring. Nowadays scouring is done by
shearing. Machines similar to those machines [Fig 3.8 (b) and (c)]
used by barbers are used to shave off Step III : After scouring, sorting is done.
hair. Usually, hair are removed during the The hairy skin is sent to a factory where
hot weather. This enables sheep to hair of different textures are separated or
survive without their protective coat of sorted.
hair. The hair provide woollen fibres. Step IV : The small fluffy fibers, called
Woollen fibres are then processed to burrs, are picked out from the hair. These
obtain woollen yarn. Shearing does not are the same burrs which sometimes

Fig.3.8 (a): Shearing

Fig.3.8 (b): Scouring in tanks

FIBRE TO FABRIC 29
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Fig.3.8 (c) : Scouring by machines Fig 3.8 (d): Rolling into yarn

appear on your sweaters. The fibres are Occupational hazard

scoured again and dried. This is the wool Wool industry (Grey Revolution) is
ready to be drawn into fibres. an important means of livelihood for
Step V : The fibres can be dyed in various many people in our country. But
sorter's job is risky as sometimes
colours, as the natural fleece of sheep they get infected by a bacterium,
and goats is black, brown or white. anthrax, which causes a fatal blood
Step VI : The fibres are straightened, disease called sorter's disease. Such
risks faced by workers in any
combed and rolled into yarn [Fig. 3.8 (d)].
industry are called occupational
The longer fibres are made into wool for hazards.
sweaters and the shorter fibres are spun
and woven into woollen cloth.
Yasir is wondering why it
About 40 tonnes of Pashmina are hurts when some one pulls his
derived from around 1.6 lakh Pashmina hair but not when he goes for a
haircut.
goats found in Ladakh region of J&K
State. Pashmina is derived from
Changthangi and Chegi goat breeds
while Changthangi is found in Ladakh Yasir is wondering why a
cotton garment cannot keep us
and Chegu breed is found in Himachal warm in winter as a woollen
Pradesh and Uttarakhand. sweater does.

FIBRE TO FABRIC 30
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 3.4 cocoon. The further development of the

Debate amongst your classmates pupa into moth continues inside the
whether it is fair on the part of humans to cocoon (Fig. 3.9). Silk fibres are used for
rear sheep and then chop off their hair for weaving silk cloth. Can you imagine that
getting wool. the soft silk yarn is as strong as a
comparable thread of steel!
3.2 SILK
Silk fibres are also animal fibres.
Silkworms spin the 'silk fibres'. The
rearing of silkworms for obtaining silk is
called sericulture. Find out from your
(a) Male
mother/aunt/grandmother the kind of silk (b) Female
clothes they have. List the kind of silk.
Before we discuss the process of Adult silk moths
obtaining silk, it is necessary to know the
interesting life history of the silk moth.

Life history of silk moth

(d) Silkworm
The female silk moth lays eggs,
from which hatch larvae which are called (c) Eggs on mulberry leaves

caterpillars or silkworms. They grow in

size and when the caterpillar is ready to
enter the next stage of its life history
called pupa, it first weaves a net to hold
itself. Then it swings its head from side to
(e) Cocoon
side in the form of the figure of eight (8). (f) Cocoon with developing moth
During these movements of the head, the
Fig.3.9 (a to f): Life history of silk moth
caterpillar secretes fibre made of protein
which hardens on exposure to air and
The silk yarn (thread) is obtained
becomes silk fibre. Soon the caterpillar
from the cocoon of the silk moth. There is a
completely covers itself by silk fibres and
variety of silk moths which look very
turns into pupa. This covering is known as
different from one another and the silk yarn

FIBRE TO FABRIC 31
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

In India, women are significantly involved in various kinds of industries related to

silk production. These are rearing of silkworms, reeling of silk from cocoons and
processing of raw silk into fabrics. By their enterprise, they contribute to the
nation's economy. China leads the world in silk production. India also ranks among
the leading silk producing countries.
they yield is different in texture (coarse, these silks with that of the artificial silk
smooth, shiny, etc.). Thus, tassar silk, pieces, which contain synthetic fibres. Try
mooga silk, kosa silk, etc., are obtained and collect pictures of different moths
from cocoons spun by different types of whose caterpillars provide the various
moths. The most common silk moth is the types of silk.
mulberry silk moth. The silk fibre from
the cocoon of this moth is soft, lustrous Activity 3.6
and elastic and can be dyed in beautiful Take an artificial (synthetic) silk

colours. thread and a pure silk thread. Burn these

Sericulture or culture of silkworms is carefully. Did you notice any difference in
a very old occupation in India. India the smell while burning? Now, burn a
produces plenty of silk on a commercial woollen fibre carefully. Did it smell like
scale & is second largest country in world burning of artificial silk or that of pure silk?
in producing Natural silk. At present, India Can you explain why?
produces 16 percent silk of world. To remember when the cocoon

Karnataka is the leading producer of silk stage is reached in the life history of the

followed by West Bengal, Bihar, etc. silk moth, try the following activity.

Activity 3.7
Activity 3.5
Photocopy Fig. 3.9. Cut out pictures
Collect pieces of silk cloth of various
of the stages of the life history of the silk
types and paste them in your scrap book.
moth, and paste them on pieces of
You can find them in a tailor's shop among
cardboard or chart paper. Jumble them.
the heap of waste cut pieces.
Take help of your mother, aunt or Now try and arrange the stages in the

teacher and identify the types of silk such correct sequence in a cyclic form.

as mulberry silk, tassar silk, eri silk, Whosoever does it fastest wins.
You may also describe the life
mooga silk, etc, Compare the texture of
history in your own words. Write it down in

FIBRE TO FABRIC 32
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

your scrap book. paper and sold to silkworm farmers. The

farmers keep eggs under hygienic
From Cocoon to Silk conditions and under suitable conditions
For obtaining silk, silk moths are of temperature and humidity.
reared and their cocoons are collected to The eggs are warmed to a suitable
get silk threads. temperature for the larvae to hatch from
eggs. This is done when Mulberry trees
Rearing Silkworms [Fig. 3.10 (b)] bear a fresh crop of leaves.
A female silk moth lays hundreds of
The larvae, called caterpillars or
eggs at a time [Fig. 3.10 (a)]. The eggs
silkworms, eat day and night and increase
are stored carefully on strips of cloth or
enormously in size [Fig. 3.10 (c)].

Leaf of Mulberry
(a) Female silkworm
moth with eggs

(b) Mulberry tree

(c) Larvae (Caterpillars/

Silkworms feeding on (d) Cocoons
Mulberry leaves
Fig.3.10: Rearing of Silkworm

FIBRE TO FABRIC 33
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

A pile of cocoons is used for

obtaining silk fibres. The cocoons are kept
The annual silk production in J&K is
under the sun or boiled or exposed to
more than 7,000 quintals.
steam. The silk fibres separate out. The
The larvae are kept in clean bamboo trays
process of taking out threads from the
along with freshly chopped mulberry
cocoon for use as silk is called reeling the
leaves. After 25 to 30 days, the
silk. Reeling is done in special machines,
caterpillars stop eating and move to a tiny
which unwind the threads or fibres of silk
chamber of bamboo in the tray to spin
from the cocoon. Silk fibres are then spun
cocoons [Fig. 3.10 (d)]. Small racks of
into silk threads, which are woven into silk
twigs may be provided in the trays to
cloth by weavers.
which cocoons get attached. The
caterpillar or silkworm spins the cocoon
inside which develops the silk moth.

Saba wants to know if the

Processing Silk cotton thread and silk thread
are spun and woven in the
same manner

A Flow Chart Depicting Story from Woollen Fleece to Textiles

Woollen Fleece
$
Spinning into Yarn

$ $
Weaving Yarns
$ $
Cloth Formation Dyeing of Yarns
$ $
Dyeing of Cloth Weaving
$ $
Cloth of Choice Woollen Cloth of Choice

FIBRE TO FABRIC 34
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Discovery of Silk
The exact time of discovery of silk is perhaps unknown. According to an old Chinese
legend, the empress Si-lung-Chi was asked by the emperor Huang-ti to find the cause of
the damaged leaves of Mulberry trees growing in their garden. The empress found white
worms eating up Mulberry leaves. She also noticed that they were spinning shiny cocoons
around themselves. Accidentally a cocoon dropped into her cup of tea and a tangle of
delicate threads separated from the cocoon. Silk industry began in China and was kept a
closely guarded secret for hundreds of years. Later on, traders and travellers introduced
silk to other countries. The route they travelled is still called the 'Silk route'.

Cocoon Scouring Silk moth

Fleece Sericulture Silkworm
Reeling Shearing Sorting

What you have learnt

 Silk comes from silkworms and wool is obtained from sheep, goat and yak. Hence silk and wool are
animal fibres.
 The hairs of camel, llama and alpaca are also processed to yield wool.
 In India, mostly sheep are reared for getting wool.
 Sheep hair is sheared off from the body, scoured, sorted, dried, dyed, spun and woven to yield
wool.
 Silkworms are caterpillars of silk moth.
 During their life cycle, the worms spin cocoons of silk fibres.
 Silk fibres are made of protein.
 Silk fibres from cocoons are separated out and reeled into silk threads.
 Weavers weave silk threads into silk cloth.

FIBRE TO FABRIC 35
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
1. You must be familiar with the following nursery rhymes:
(i) "Baa baa black sheep, have you any wool".
(ii) "Mary had a little lamb, whose fleece was white as snow".
Answer the following:
(a) Which parts of the black sheep have wool ?
(b) What is meant by the white fleece of the lamb ?
2. The silkworm is (a) a caterpillar, (b) a larva. Choose the correct option.
(i) a (ii) b (iii) both a and b (iv) neither a nor b
3. Which of the following does not yield wool?
(i) Yak (ii) Camel (iii) Goat (iv) Woolly dog
4. What is meant by following terms?
(i) Rearing (ii) Shearing (iii) Sericulture
5. The science of raising silk worms so as to obtain silk cocoons is called:
(a) Apiculture (b) Horticulture
(c) Sericulture (d) Pisciculture
6. The hair on the skin of sheep, yak, etc, from which wool can be obtained.
(a) Wool (b) Fleece
(c) Silk (d) Yarn
7. The proper sequence of life cycle of a silkworm is:
(a) Egg " Pupa " Caterpillar
(b) Pupa " Egg " Caterpillar
(c) Eggs " Caterpillar " Pupa
(d) Caterpillar " Egg " Pupa
8. Which of the following diseases is caused due to wool industry
(a) Typhoid (b) Cholera
(c) Tetanus (d) Anthrax
9. Given below is a sequence of steps in the processing of wool. Which are the missing
steps? Add them
Shearing, __________, Sorting, __________, __________, __________
10. Make sketches of the two stages in the life history of the silk moth which are directly
related to the production of silk.
11. Out of the following, which are the two terms related to silk production ?
Sericulture, floriculture, moriculture, apiculture and silviculture.
Hints:
(i) Silk production involves cultivation of Mulberry leaves and rearing silkworms.

FIBRE TO FABRIC 36
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(ii) Scientific name of Mulberry is Morus alba.

12. Match the words of Column I with those given in Column II:
Column I Column II
1. Scouring (a) Yields silk fibres
2. Mulberry leaves (b) Wool yielding animal
3. Yak (c) Food of silkworm
4. Cocoon (d) Reeling
(e) Cleaning sheared skin
13. Given below is a cross word puzzle based on this lesson. Use hints to fill in the
blank spaces with letters that complete the words.
Down Across
(D) 1. Thorough washing (A) 1. Keeps warm
2. Animal Fibre 2. Its leaves are eaten by silkworms
3. Long thread like structure 3. Hatches from egg of moth

1D 2D

3D 1A

2A

3A

Extended Learning - Activities and Projects

1.

Saba wants to know the

maximum length of
continuous silk thread that
can be obtained from a cocoon.

Find out for her.

FIBRE TO FABRIC 37
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2.

Yasir wants to know why

caterpillars need to shed their skin
when they grow bigger but we
humans do not.

Do you have any idea?

3.

Yasir wants to know why

caterpillars should not be collected
with bare hands.

4. Saba wanted to buy a silk frock and went to the market with her mother. There they
found that the artificial (synthetic) silk was much cheaper and wanted to know why. Do
you know why? Find out.
5. Someone told Saba that an animal called 'Vicuna' also gives wool. Can you tell her
where this animal is found? Look for this in a dictionary or an encyclopedia.
6. When handloom and textile exhibitions are held, certain stalls display real moths of
various varieties of silk and their life histories. Try and visit these stalls with elders or
teachers and see these moths and stages of their life history.
7. Look for eggs of any moth or butterfly in your garden or park or any other place full of
plants. They look like tiny specks (dots) laid in a cluster on the leaves. Pull out the
leaves containing eggs and place them in a cardboard box. Take some leaves of the
same plant or another plant of the same variety, chop them and put them in the box.
Eggs will hatch into caterpillars, which are busy eating day and night. Add leaves
everyday for them to feed upon. Sometimes you may be able to collect the caterpillars.

FIBRE TO FABRIC 38
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

But be careful, Use a paper napkin or a paper to hold a caterpillar.

Observe everyday. Note the (i) number of days taken for eggs to hatch, (ii) number of
days taken to reach the cocoon stage, and (iii) number of days to complete life cycle.
Record your observations in your notebook.

You can read more on the following website:

www.indiansilk.kar.nic.in

DO YOU KNOW?

In terms of the number of sheep, India ranks third in the world behind China and
Australia. However, the New Zealand sheep are known to yield the best wool.

FIBRE TO FABRIC 39
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

4 HEAT

H
eat: - "Heat is a form of energy Table 4.1: Hot and Cold Objects
which produces in us the Object Cold/Cool Warm/Hot
sensation of warmth". You have Ice cream
learnt that woollen clothes are made from Spoon in a
tea cup
animal fibres. You also know that cotton
Fruit juice
clothes are made from plant fibres. We
Handle of a
wear woollen clothes during winters when frying pan
it is cold outside. Woollen clothes keep us
warm. We prefer to wear light coloured Do not touch object which are too hot.
Be careful while handling a candle
cotton clothes when it is hot. These give
flame or a stove.
us a sensation of coolness. You might
We see that some objects are cold
have wondered why particular types of
while some objects are hotter than others
clothes are suitable for a particular
while some are colder than others. How
season.
do we decide which object is hotter than
In winter you feel cold inside the
the other? We often do it by touching the
house. If you come out in the sun, you feel
objects. But is our sense of touch
warm. In summer, you feel hot even
reliable? Let us find out.
whether an object is hot or cold? How do
Activity 4.1
we find out how hot or cold an object is? In
Take three large mugs. Label them
this chapter we shall try to seek answer to
as A, B and C. Put cold water in mug A and
some of these questions.
hot in mug B. Mix some cold and hot water
4.1 HOT AND COLD
in mug C. Now dip your left hand in mug A
In our day-to-day life, we come
and the right hand in mug B. After keeping
across a number of objects. Some of
the hands in the two mugs for 2-3
them are hot and some of them are cold.
minutes, put both the hands
Tea is hot and ice is cold. List some
simultaneously in mug C (Fig.4.1).
objects you use commonly in Table 4.1.
Make sure that water is not so hot that
Mark these objects as hot or cold.
you burn hand

HEAT 40
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Do both the hands get the same feeling ? thermometer. Hold the thermometer in
your hand and examine it carefully. If you
(A) (B) (C)
do not have a thermometer, request a
friend to share it with you. A clinical
thermometer looks like th e one shown in
Fig. 4.2.

Fig.4.1: Feeling water in three mugs Fig.4.2: A clinical themometer

Yasir says,"My left hand

tells me that the water in mug A clinical thermometer consists of
C is hot and the right hand a long, narrow, uniform glass tube . It has
tells me that the same water
is cold . What should I a bulb at one end. This bulb contains
conclude?"
mercury. Outside the bulb, a small shining
thread of mercury can be seen.
Yasir's confusion shows that we If you do not see the mercury
cannot always rely on our sense of touch thread, rotate the thermometer a bit till
to decide whether an object is hot or cold . you see it. You will also find a scale on the
Sometimes it may deceive us. thermometer. The scale we use is the
Then, how do we find out how hot 0
Celsius scale, indicated by C.
an object really is? A reliable measure of
the hotness of an object is its
Yasir wondered which of the two scale
temperature. Temperature is measured
shown in Fig. 4.2 he should read.
by a device called thermometer.
Saba told him that India has adopted
4.2 MEASURING TEMPERATURE the Celsius scale and we should read that
Have you seen a thermometer? scale. The other scale with the range
0
Recall that when you or someone else in 94-108 degrees is the Fahrenheit scale ( F).
It was in use earlier.
your family had fever, the temperature
was measured by a thermometer. The
thermometer that measures our body A clinical thermometer reads
0 0
temperature is called a clinical temperature from 35 C to 42 C.

HEAT 41
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 4.2 temperature?

Reading a thermometer The normal temperature of
Let us learn how to read a human body is 370C. Note that the
t he rmo met er. Fi r st f ind o ut th e temperature is stated with its unit.
te mperat ure difference indi cated
between the two bigger marks. Also note
down the number of divisions (shown by
smaller marks) between these marks.
Suppose the bigger marks read one
degree and there are five divisions
between them. Then, one small division
can read 1 = 0.20C.
5

How to use
Wash the thermometer, preferably
with an antiseptic solution. Hold it firmly
and give it a few jerks. The jerks will bring Fig.4.3: Correct method of reading a clinical
the level of mercury down. Ensure that it thermometer

falls below 350C.Now place the bulb of the

thermometer under your tongue. After Saba measured her body
one minute, take the thermometer out and temperature. She got worried as
it was not exactly 370C.
note the reading. This is your body
temperature. The temperature should
0
always be stated with its unit C. Let us try to assure Saba that there is
What did you record as your body nothing wrong with her.

Precautions to be observed while reading a clinical thermometer

Thermometer should be washed before and after use, preferably with an antiseptic
solution. Ensure that before use the mercury level is below 35 0 C.
Read the thermometer keeping the level of mercury along the line of sight. (See Fig. 4.3)
Handle the thermometer with care. If it hits against some hard object, it can break.
Don't hold the thermometer by the bulb while reading it

HEAT 42
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 4.3 CAUTION

Measure the body temperature Do not use a clinical thermometer for
measuring the temperature of any
of some of your friends (at least 10) with
object other than the human body.
a clinical thermometer. Record your
Also avoid keeping the thermometer in
observations as in Table 4.2.
the sun or near a flame. It may break.
Table 4.2: Body temperature of
some persons 4.3 LABORATORY THERMOMETER
Name Temperature (0C) How do we measure the
temperature of other objects? For this
purpose, there are other thermometers.
Is the body temperature of every
0 One such thermometer is known as the
person 37 C.
The temperature of every laboratory thermometer. The teacher
0 will show you this thermometer. Look at
person may not be 37 C. It could be
it carefully and note the highest and the
slightly higher or slightly lower. Actually,
what we call normal temperature is the
Different types of thermometers are
average body temperature of a large
used for different purposes. The
number of healthy persons.
The clinical thermometer is maximum and minimum temperatures
designed to measure the temperature of the previous day, reported in
of human body only. The temperature weather reports, are measured by a
of human body normally does not go thermometer called the maximum-
0 0
below 35 C or above 42 C. This is the minimum thermometer.
reason that this thermometer has the
0
range 35 C to 42 C
0 lowest temperature it can measure.
The range of a laboratory
0
thermometer is generally from -10 C to
0
110 C (Fig. 4.4). Also, as you did in the
Yasir got a naughty idea. He case of the clinical thermometer, find
wanted to measure the temperature out how much a small division on this
of hot milk using a clinical
thermometer. Saba stopped him thermometer reads. You would need
from doing so. ths information to read the thermometer
correctly. Let us now learn how this
thermometer is used.
Fig. 4.4 A laboratory thermometer

HEAT 43
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

In addition to the precautions needed while reading a clinical

thermometer, the laboratory thermometer
S should be kept upright not tilted (Fig. 4.5).
S bulb should be surrounded from all sides from the substance of which the temperature
is to be measured. The bulb should not touch the surface of the container.

Activity 4.4 Note the reading. This is the

Take some tap water in a beaker or a temperature of water at this time.
mug. Dip the thermometer in water so that Compare the temperature of water
the bulb is immersed in water but does not recorded by each student in the class. Are
touch the bottom or the sides of the there any variations in the readings?
container. Hold the thermometer vertically Discuss the possible reasons.
(Fig. 4.5). Observe the movement of Let us try to answer this question.
mercury in the thermometer. Wait till the Activity 4.5
mercury thread becomes steady. Take some hot water in a beaker or
a mug. Dip the thermometer in water. Wait
till the mercury thread becomes steady
and note the temperature. Now take out
the thermometer from the water. Observe
carefully what happens now. Do you
notice that as soon as you take
thermometer out of water, the level of
mercury begins to fall. This means that
the temperature must be read while the
thermometer is in water.
You may recall that while taking
your own temperature, you have to take
the thermometer out of your mouth to note
the reading. Can you then use the
laboratory thermometer to measure your
body temperature? Obviously, it is not
Fig.4.5: Measuring temperature of water with a convenient to use the laboratory
laboratory thermometer
thermometer for this purpose.

HEAT 44
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Yasir now understand why Yasir wonders why the level

clinical thermometer cannot be of mercury should change at
used to measure high
temperatures. But still wonders all when the bulb of the
whether a laboratory thermometer thermometer is brought in contact
can be used to measure his body
with another object.
temperature.

Why does the mercury not fall or rise in a flame. It is because the heat passes from
clinical thermometer when taken out of the the flame to the utensil. When the pan is
mouth? removed from the fire, it slowly cools down.
Observe a clinical thermometer again. Do Why does it cool down? The heat is
you see a kink near the bulb (Fig. 4.6). transferred from t he pan to the
What is the use of the kink? It prevents surroundings. So you can understand that
mercury level from falling on its own. in both cases, the heat flows from a hotter
object to a colder object. In fact, in all cases
heat flows from a hotter object to a colder
object.
Fig. 4.6: A clinical thermometer has a kink in it.
How dos heat flow? Let us investigate.

There is a lot of concern over

the use of mercury in Saba asks: "Does it mean
thermometers. Mercury is a that heat will not be
toxic substance and is very transferred if the temperature
difficult to dispose of if a of two objects is the same?"
thermometer breaks. These
days, digital thermometers are
available which do not use
Activity 4.6
Take a rod of flat strip of a metal, say
mercury.
of aluminium or iron. Fix a few small wax
pieces on the rod. These pieces should be
4.4 TRANSFER OF HEAT
at nearly equal distances (Fig. 4.7). Clamp
You might have observed that a
the rod to a stand. If you do not find a stand,
frying pan become hot when kept on a

HEAT 45
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

you can put one end of the rod in between wooden handle. Can you lift a hot pan by
bricks. Now, heat the other end of the rod holding it from the handle without getting
and observe. hurt?
What happens to the wax pieces? Activity 4.7
Do these pieces begin to fall? Which Heat some water in a small pan or
piece falls the first? Do you think that heat a beaker. Collect some articles such as a
is transferred from the end nearest to the steel spoon, plastic scale, pencil and
flame to the other end? divider. Dip one end of each of these
articles in hot water (Fig.4.8).

Fig.4.7: Flow of heat through a metal strip

The process by which heat is

transferred from the hotter end to the
colder end of an object is known as
Fig.4.8: Conduction of heat by different
conduction. In solids, generally, the heat materials
is transferred by the process of
Wait for a few minutes. Touch the other
conduction.
end. Enter your observation in Table 4.3
Do all substances conduct heat
The materials which allow heat
easily? You must have observed that the
to pass through them easily are
metallic pan for cooking has a plastic or
conductors of heat. For example
Table: 4.3
Article Material with which the Does the other end get
article is made of hot (Yes / No)
Steel spoon Metal Yes

HEAT 46
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

aluminium, iron and copper. The materials heat transfer is known as convection.
which do not allow heat to pass through How does the heat travel in air?
them easily are poor conductor of heat In which direction does the smoke go?
such as plastic and wood. Poor conductors
are known as insulators.
The water and air are poor
conductors of heat. Then, how does the
heat transfer take place in these
substances? Let us find out.

Activity 4.8
Take a round bottom flask (if flask
is not available, a beaker can be used). Fill
it two-thirds with water. Place it on a tripod
stand, or make some arrangement to
place the flask in such a way that you can
heat it by placing a candle below it. Wait till
the water in the flask is still. Place a crystal Fig.4.9: Convection of heat in water

of potassium permanganate at the bottom The air near the heat source gets
of the flask gently using a straw. Now, heat hot and rises. The air from the sides comes
the water by placing the candle just below in to take its place. In this way the air gets
the crystal. heated. The following activity confirms this
Write your observation in your idea.
notebook and also draw a picture of what
you observe (Fig. 4.9). Activity 4.9
When water is heated, the water Light a candle. Keep one hand
near the flame gets hot. Hot water rises up. above the flame and one hand on the side
The cold water from the sides moves down of the flame (Fig. 4.10). Do your hands feel
towards the source of heat. This water also equally hot? If not which hand feels hotter?
gets hot and rises and water from the sides and why?
moves down. This process continues till
the whole water gets heated. This mode of

HEAT 47
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Be careful. Keep your hands at a safe sides, however, there is no convection and
distance from the flame so that they do air does not feel as hot as at the top.
not get burnt. The people living in the coastal
ar ea s e x pe ri e nc e a n i n te re s ti n g
phenomenon. During the day, the land
gets heated faster than the water. The air
over the land becomes hotter and rises up.
The cooler air from the sea rushes in
towards the land to take its place. The
warm air from the land moves towards the
sea to complete the cycle. The air from the
Fig.4.10: Transfer of heat by convection in air sea is called the sea breeze. To receive
the cooler sea breeze, the windows of the
Notice that towards the top, the air gets houses in coastal areas are made to face
heated by convection. Therefore, the the sea. At night it is exactly the reverse
hand above the flame feels hot. On the (Fig. 4.11). The water cools down more
Day time Night time

Hot Cool
Hot
Cool

Fig. 4.11

HEAT 48
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

slowly than the land. So, the cool air from 4.5 KINDS OF CLOTHES WE
the land moves towards the sea. This is WEAR IN SUMMER AND WINTER
called the land breeze. Fig. 4.11 shows You know that in summer we

this phenomenon. prefer light coloured clothes and in winter

When we come out in the sun, we usually wear dark coloured clothes.
we feel warm. How does the heat from the Why is it so? Let us find out.
sun reach us? It cannot reach us by
conduction or convection as there is no Activity 4.10
medium such as air in most part of the Take two identical tin cans. Paint

space between the earth and the sun. the outer surface of one black and of the

From the sun the heat comes to us by other white (Fig. 4.12). Pour equal

another process known as radiation. The amounts of water in each and leave them

transfer of heat by radiation does not in the mid-day sun for about an hour.

require any medium. It can take place Measure the temperature of water in both

whether a medium is present or not. the cans. Do you find any difference in the

When we sit in front of a room heater, we temperatures? In which can is the water

get heat by this process. A hot utensil kept warmer? You can feel the difference even

away from the flame cools down as it by touching water in the two cans.

transfer heat to the surroundings by

radiation. Our body too, gives heat to the
surroundings and receives heat from it by
radiation.
All hot bodies radiate heat.
Fig.4.12: Containers with black and white
When this heat falls on some object, a surface
part of it is reflected, a part is absorbed
and a part may be transmitted. The
Activity 4.11
temperature of the object increases due
Fill the two cans used in Activity
to the absorbed part of the heat. Why are
4.10 with the same amount of hot water at
you advised to use an umbrella when you
0
go out in the sun? the same temperature (say, at 60 C).
Leave the cans in a room or in a shade.
Note the temperature of water after 10-15

HEAT 49
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

minutes. Does the temperature of water in Woollen clothes keep us warm in

both the cans fall by the same amount? winter
Do these activities suggest to In the winter, we use woolen
you the reason why it is more comfortable clothes. Wool is a poor conductor of heat.
to wear white or light coloured clothes in Moreover, there is air trapped in between
the summer ? Dark surfaces absorb more the wool fibres. This air prevents the flow
heat and, therefore, we feel comfortable of heat from our body to the cold
with dark coloured clothes in the winter. surroundings. So, we feel warm.
Suppose you are given the
Light coloured clothes reflect most of the
choice in winter of using either one thick
heat that falls on them and, therefore, we
blanket or two thin blankets joined
feel comfortable wearing them in the
together. What would you choose and
summer.
why. Remember that there would be a
layer of air in between the blankets.

Celsius Scale Insulator Sea breeze

Conduction Land breeze Temperature
Conductor Radiation Thermometer
Convection

What you have learnt

v Our sense of touch is not always a reliable guide to the degree of hotness of an object.
v Temperature is a measure of the degree of hotness of an object.
v Thermometer is a device used for measuring temperatures.
v Clinical thermometer is used to measure our body temperature. The range of this thermometer is
0 0
from 35 C to 42 C. For other purpose, we use the laboratory thermometers. The range of these
0 0
thermometers is usually from -10 C to 110 C.
v
0
The normal temperature of the human body is 37 C.
v The heat flows from a body at a higher temperature to a body at a lower temperature. There are
three ways in which heat can flow from one object to another. These are conduction, convection
and radiation.

HEAT 50
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

v In solids, generally, the heat is transferred by conduction. No medium is required for transfer of
heat by radiation.
v The materials which allow heat to pass through them easily are called insulators.
v Dark-coloured objects absorb radiation better than the light-coloured objects. That is the reason
we feel more comfortable in light-coloured clothes in the summer.
v Woollen clothes keep us warm during winter. It is so because wool is a poor conductor of heat
and it has air trapped in between the fibres.

EXERCISES
1. State similarities and differences between the laboratory thermometer and the
clinical thermometer.
2. Give two examples each of conductors and insulators of heat.
3. Fill in the blanks:
(a) The hotness of object is determined by its __________.
(b) Temperature of boiling water cannot be measured by a __________
thermometer.
(c) Temperature is measured in degree __________.
(d) No medium is required for transfer of heat by the process of __________.
(e) A cold steel is dipped in a cup of hot milk. It transfers heat to its other end by the
process of __________.
(f) Clothes of __________ colours absorb heat better than clothes of light
colours.
4. Match the following
(i) Land breeze blows during (a) Summer
(ii) Sea breeze blows during (b) Winter
(iii) Dark coloured clothes are preferred during (c) Day
(iv) Light coloured clothes are preferred during (d) Night
5. Discuss why wearing more layers of clothing during
winter keeps us warmer than wearing just one thick
piece of clothing.

6. Look at Fig. 4.13. Mark where the heat is being

transferred by conduction, by convection and by
radiation.

Fig.4.13

HEAT 51
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

7. In places of hot climate it is advised that the outer walls of houses be painted white.
Explain.
0 0
8. One litre of water at 30 C is mixed with one litre of water at 50 C. The temperature of
mixture will be
0 0 0
(a) 80 C (b) more than 50 C but less than 80 C
0 0 0
(c) 20 C (d) between 30 C and 50 C
0 0
9. An iron ball at 40 C is dropped in a mug containing water at 40 C. The heat will
(a) flow from iron ball to water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.
10. A wooden spoon is dipped in a cup of ice cream. Its other end
(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection.
(c ) becomes cold by the process of radiation.
(d) does not become cold.
11. Stainless steel pans are usually provided with copper bottoms. The reason for this
could be that
(a) copper bottom makes the pan more durable.
(b) such pans appear colourful.
(c) copper is a better conductor of heat than the stainless steel.
(d) copper is easier to clean than the stainless steel.

Extending Learning -Activities and Projects

1. Go to a doctor or your nearest health centre. Observe the doctor taking temperature
of patients, Enquire:
(a) Why she dips the thermometer in a liquid before use.
(b) Why the thermometer is kept under the tongue.
(c) Whether the body temperature can be measured by keeping the thermometer
at some place other than the mouth.
(d) Whether the temperature of different parts of the body is the same or different.
2. Go to a veterinary doctor (a doctor who treats animals). Discuss and find out the
normal temperature of domestic animals and birds.
3. Wrap a thin strip tightly around an iron rod. Try to burn the paper with candle while

HEAT 52
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

rotating the iron rod continuously. Does it burn? Explain your observation.
4. Take a sheet of paper. Draw a spiral on it as shown in the Fig. 4.14. Cut out the
paper along the line . Suspend the paper as shown in Fig. 4.14 above a lighted

Fig.4.14

candle . Observe what happens. Think of an explanation.

5. Take two similar transparent glass bottles having wide mouths. Put a few crystals
of potassium permanganate or pour a few drops of ink in one bottle. Fill this bottle
with hot water. Fill the other bottle with cold water. Cover the cold water bottle with
a thick piece of paper such as a postcard. Press the postcard firmly with one hand
and hold the bottle with the other hand. Invert the bottle and place it on the top of
the hot water bottle. Hold both the bottles firmly. Ask some other person to pull the
postcard. Observe what happens. Explain.

You can read more on the following website:

www.bbc.uk/schools/gcsebitesize/physics/energy/
energytransverse6.html

HEAT 53
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW ?
The Celsius scale was devised by a Swedish Astronomer, Anders Celsius in
1742. Strangely, he fixed temperature of the boiling water as 00C and of freezing
water as 1000C . However, this order was reversed very soon.

HEAT 54
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

5 ACIDS, BASES AND SALTS

T
here are a large number of edible rinsed with water.
substances which we use in our 2. Do not taste all substances above.
daily life. Let us try to find the Some of them can be poisonous.

taste of few substances given in Always ask your elders, teachers,

Table 5.1. before you taste an unknown

Table 5.1 substance.
Substance Taste (sour/bitter/ 5.2 ACIDS AND BASES
salty/sweet, etc.) The substances such as curd,
Curd Sour grapes, lemon juice, orange juice,
Grapes Sour and sweet tamarind, etc., have sour taste.
Lemon juice Sour The sour substances found in
Orange juice Sour and sweet nature or prepared artificially are called
Sugar solution Sweet acids. The chemical nature of acids is
Common salt - Salty called acidic nature.
solution The term acid has been derived
Amla Bitter from the Latin word acidus, which means
Unripe mangoes Bitter sour. A large number of fruits and some
Baking Soda - Bitter vegetables have sour taste and hence are
solution acidic substances.
Soap solution Bitter The sour taste of lemon is due to

Tamarind (imli) Sour citric acid, the sour taste of grapes and

Vinegar Sour tamarind is due to tartaric acid and that of

Plain Soda Water Sour vinegar is due to acetic acid.

The acids which are found in

Caution plants and animals are commonly called

1. The taste of edible substance natural acids or organic acids. The
should be found by touching a drop table given below gives the names of
of it to the tip of the tongue. naturally occurring acids and their source.
Afterwards, the mouth should be

ACIDS, BASES AND SALTS 55

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Table 5.2: Natural or organic acids.

DO YOU KNOW ?

Natural Source Acid 1. The fats or oils which we consume

1. Oranges & lemons CitricAcid contain complex compounds called

2. Grapes, tamarind, Tartaric acid fattyacids.
goose berries 2. All kinds of proteins (animal or plant)
3. Tomatoes Oxalic acid are made by amino acids. It is the
4. Sour milk Lactic acid amino acid which helps in growth,
5. Vinegar Acetic acid development, and repair of our body
6. Apples Malic acid cells.
7. Proteins Amino acids 3. The nucleus of any living cell
contains deoxyribonucleic acid or
In addition to natural or organic DNA. The DNA has specific genetic
acids, there are acids, which can be information a n d c o n t ro l s e v e ry
prepared from non-living things, by feature of the living body, such as
chemical means. Such acids are called look, colour of eyes, etc.
mineral acids.
Coming back to taste of
Definition of mineral acid substances, the substances like baking
An acid which is prepared from the soda solution, soap solution, etc., have a
minerals of the earth is called minerals bitter taste. As these substances do not
acid. have sour taste, therefore, they are not
Examples of Mineral Acids acids.
Name of Acid Formula If you rub soap solution or baking
soda solution between your fingers. You
— Sulphuric acid H2 SO4
will feel 'slippery'.
— Nitric acid HNO3 The substances which have a
— Hydrochloric acid HCI
bitter taste and feel slippery (soapy touch)
— Phosphoric acid H3 PO4
are known as bases. The nature of such
substances is said to be basic.
Note : Mineral acids are highly corrosive in
nature. They can cause severe burns on
Table 5.3 gives the list of common
the skin. They should never be handled bases and the substance in which they
with bare hand or tasted. are found in small amounts.

ACIDS, BASES AND SALTS 56

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Table 5.3: Common bases

Name of base Chemical Formula Found in

Sodium hydroxide NaOH Soap
Potassium hydroxide KOH Liquid soap
Calcium hydroxide Ca (OH) 2 Limewater
Magnesium hydroxide Mg (OH) 2 Milk of magnesia
Ammonium hydroxide NH4OH Window cleaner solution

We cannot taste all substances to brownish red stain, it again changes to

find whether they are acidic or basic in yellow colour. The lemon contains

nature. It is because some substances another substance called citric acid,

may be corrosive to skin or poisonous. which neutralizes the effect of sodium

Now the question arises, if we hydroxide. Thus, the turmeric stain
cannot taste every substance, how do we regains its original colour.
find its nature. Special type of From this discussion, we can say

substances are used to find whether a that there are certain substances which

given substance is acidic or basic in change their colour on coming in contact

nature. Let us perform the following with other substances. Such substances

activity : are called indicators.

ACTIVITY 5.1
5.3 INDICATORS
Turmeric (haldi) is commonly used
The complex, naturally occurring
as spice in kitchen. It is yellow in colour
substances, which change their colour on
and stains a white cloth yellow. If the
coming in contact with acidic or basic
yellow stain is rubbed with soap solution,
substances are called indicators.
the colour of the stain changes to In the above discussion, turmeric is an
brownish red. Why does this happen? indicator. Other common indicators are
The soap solution always contains a litmus solution, phenolphthalein solution
small amount of a chemical called sodium and china rose petals (Gudhal).
hydroxide. It is the sodium hydroxide Sometimes we soak thin
which changes the colour of turmeric rectangular strips of filter paper in the
stain from yellow to brownish red. Now, if solution of above mentioned substances
we rub a freshly cut lemon on the and then dry them. These dried strips are

ACIDS, BASES AND SALTS 57

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

called litmus paper, methyl orange paper, commonly called red litmus paper
phenolphthalein paper, China rose paper, [Fig.5.1(b)] or blue Litmus Paper
etc. [Fig.5.1(c)]. These strips are bound in
On the basis of effect on indicators, the form of a tiny booklets and supplied to
we can classify substances as acidic, chemical laboratories.
basic or neutral substances.
By neutral substances we mean
such substances which are neither acid,
nor basic and do not effect indicators. For
example, distilled water, alcohol,
common salt solutions are neutral
substances.

5.4 NATURAL IN DIC ATORS

Fig.5.1 (a) : Lichen plant
AROUND US
(a) Litmus: A Natural Dye
Litmus in the form of solution or in
the form of dried paper strips is the most
commonly used indicator.
The dye (litmus) is extracted from
Fig.5.1 (b) :
lichen plants found in Tundra region Red litmus paper

[Fig.5.1(a)].The solution of litmus in

distilled water is mauve (purple) in colour.
This solution is called neutral litmus
solution. Fig.5.1(c):
Blue litmus paper
The neutral litmus solution turns
red when added to some acidic solution.
(B) Turmeric
Conversely, the neutral litmus solution
Turmeric is another natural
turns blue, when added to some basic
indicator.
solution.
If thin strips of paper are soaked in red (C) China Rose
litmus solution or blue litmus solution and China rose is a flower which has
then dried, and then these strips are pink petals. The coloured solution

ACIDS, BASES AND SALTS 58

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 5.2

To find the effect on (a) red litmus paper (b) blue litmus paper of different solutions.
Mix a few drops of vinegar in a cup half filled with distilled water. Take a dropper

and fill it with solution of vinegar. Pour a drop of this solution on (i) blue litmus paper (ii) red

litmus paper.
You will observe that blue litmus paper turns red, but there is no effect on red

litmus paper. Thus, vinegar solution is acidic in nature.

Repeat the above procedure with the following:

(I) Soap solution (ii) Aerated water (soda water)

(Iii) Common salt solution (iv) Shampoo solution
(V) Baking soda solution (vi) Lemon juice solution
(Vii) Hydrochloric acid solution (viii) Nitric acid solution
(ix) Washing soda solution (x) Lime Water

Table 5.4: Shows the expected results.

S. Test solution Effect on red Effect on blue Inference
no litmus paper litmus paper
1. Soap solution Changes to blue colour No Change Solution is basic
2. Aerated water No Change Change to red Solution is acidic
colour
3. Common salt No Change No Change Solution is neutral
solution
4. Shampoo solution Changes to blue colour No Change Solution is basic

5. Baking soda Changes to blue colour No Change Solution is basic

solution
6. Lemon juice No Change Change to red Solution is acidic
solution colour
7. Hydrochloric acid No Change Change to red Solution is acidic
solution colour
8. Nitric acid solution No Change Change to red Solution is acidic
Colour
9. Washing soda Changes to blue colour No Change Solution is basic
solution
10. Limewater Changes to blue colour Change

ACIDS, BASES AND SALTS 59

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

extracted from it is light pink colour. dark pink colour (magenta) in acidic
When used as an indicator, its colour solutions. In neutral solution, its colour
changes to green in basic solution and does not change.

ACTIVITY 5.3
To find the effect of acidic /basic solutions on turmeric as an indicator.
· Add a spoonful of turmeric powder in a cup containing warm water. Stir the contents
well and allow it to stand so that undissolved turmeric settles down.
· Pour the clear solution over a blotting paper or a filter paper. Allow the paper to dry and
cut strips 5cm long and 1cm wide.
· Dip a strip each in the solutions of substances mentioned in Activity 5.2.
· You will notice the yellow colour of the strip changes to brown or reddish brown in the
solutions of soap, shampoo, baking soda, washing soda and limewater. These
solutions are basic in nature.
· The yellow colour of the strip will not change in case of aerated water, common salt
solution, lemon juice, hydrochloric acid and nitric acid. These solutions may be neutral
or acidic.
Note: Turmeric as an indicator identifies basic solutions only. Its colour does not
change in acidic or neutral solutions.

(D) Phenolphthalein solution, shampoo solution, washing

Phenolphthalein is an organic dye soda solution, etc., it changes to deep
prepared by dissolving it in alcohol. Its pink colour.
solution is colourless. However, it remains colourless, in
When a few drops of phenolphthalein acidic or neutral solutions.
are added to basic solution, such as soap

ACTIVITY 5.4
To find the effect of acidic /basic solutions on the china rose solution as an indicator.
l Take a fistful of china rose petals in a bowl. Soak the petals in the boiling water for
half an hour. On cooling, crush the petals with hand and then filter the mixture. You
will get pink coloured clear solution, which can be used as an indicator.
l Take 1cc of china rose solution in a test tube and to it add few drops of soap
solution. Shake the contents. You will notice that colour of the solution changes to

ACIDS, BASES AND SALTS 60

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

green.
· Similarly, repeat the activity with solutions
mentioned in Activity 5.2.
· You will notice that pink colour of china rose
solution changes to green colour in case of
solutions of soap, shampoo, baking soda,
Colour changes to
washing soda and limewater. These solutions Colour changes
light green in basic
to deep pink in
acids
are basic in nature. China Rose

· You will notice that pink colour of china rosé Changes of

Natural China
Rose Colour
solution changes to deep pink colour in case of
Fig. 5.2 : China rose as an indicator
aerated water, lemon juice, hydrochloric acid and nitric acid. These solutions are
acidic in character.
· You will notice that pink colour of china rose solution does not change in case of
common salt solution. This solution is neutral in nature.

5.5 GENERAL PHYSICAL conductors of electricity.

PROPERTIES OF ACIDS
1. They have a sour taste. DO YOU KNOW?
2. They turn blue litmus solution red, 1. Yo u m u s t h a v e s e e n p e o p l e
but do not affect red litmus solution. g etting t heir copp er or bras s
3. They do not affect turmeric solution. cooking vessels coated with tin metal
4. They do not affect phenolphthalein
(kalai). Why do they do so?
solution. When we cook food in these
5. They turn China rose solution to
vessels without the coating of kalai,
deep pink colour.
the organic acids present in the food
6. Mineral acids, such as sulphuric
materials react with copper and
acid, hydrochloric acid and nitric acid
corrode it. Further-more, the copper
are highly corrosive. They cause
salts formed by the acids are
painful blisters on the skin.
poisonous in nature.
7. Most of the acids are soluble in
The kalai protects the vessel from the
water
action of acids for a while, and hence,
8. All acid solutions in water are good

ACIDS, BASES AND SALTS 61

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

prevents food poisoning. pink.

However, these days, quite a number 5. They turn china rose solution green.
of people use stainless steel cooking 6. Base like sodium hydroxide,
vessels, because they are not affected potassium hydroxide and calcium
by the acids present in food materials. hydroxide cause painful blisters on
2. Acid Rain : Rain containing traces of skin and are highly corrosive in
mineral acid, such as hydrochloric nature.
acid, nitric acid is called acid rain. 7. Most of the bases are insoluble in
These acids are formed when the air is water.
highly polluted with gases like sulphur 8. All bases have slippery touch like

dioxide and nitrogen dioxide, due to that of soap.

excessive burning of coal and 5.7 NEUTRALISATION

We have learnt that bases turn
petroleum products. The above
phenolphthalein solution pink. The pink
mentioned gases dissolve in rain
colour changes to colourless, if an acid is
droplets and cause acid rain.
The acid rain can cause extensive added to it. Let us perform the following

damage to the forests and crops as activity :

5.8 NEUTRALISATION IN EVERY
they die. Furthermore, the acids in acid
DAY LIFE
rain react chemically with the
(a) Indigestion
building materials of houses and
Our stomach walls produce
historical monuments. Thus, the
gastric juice which contains hydrochloric
buildings gradually decay.
acid. The gastric juice helps in the
digestion of food. However, when we eat
5.6 GENERAL PHYSICAL very spicy foods or have worries or
PROPERTIES OF BASES tension, the stomach wall produces a
1. They have a bitter taste. large amount of hydrochloric acid which
2. They turn red litmus solution blue, leads to the acidity of stomach. One has
but do not affect blue litmus a burning feeling in the stomach and sour
solution. taste in the mouth. This condition is
3. They turn yellow turmeric solution
commonly called “acidity of stomach or
reddish brown.
indigestion”. If not controlled, it can
4. They turn phenolphthalein solution

ACIDS, BASES AND SALTS 62

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 5.5
To show that acids react with alkalis and a neutralization reaction takes place.
Materials required:
In sodium hydroxide
Ÿ dilute sodium hydroxide solution sol. phenalphthalein
solution turns pink Dropper
Ÿ dilute hydrochloric acid or lemon juice Containing
hydrochloride acid
Ÿ phenolphthalein solution
Solution
Ÿ beaker becomes
colourless
Ÿ a dropper.
Fig. 5.3 (a) Fig. 5.3 (b)

Method : Pour about 20cc of sodium hydroxide solution in the beaker. To this
solution, add phenolphthalein solution. You will notice that the solution turns deep pink.
Fill the dropper with dilute hydrochloric acid. Allow the acid to fall in the beaker drop
by drop. Go on stirring the beaker.
You will notice that at some stage, by the addition of one drop of acid the solution
suddenly become colourlees.
It is because at this stage the sodium hydroxide solution has completely reacted
with hydrochloric acid to form salt and water. Thus, the last drop of hydrochloric acid
makes the acid in excess, and hence, the colour of phenolphthalein changes from pink to
colourless.
Touch the beaker immediately after the solution become colourless. You will notice
that beaker is warm. Thus, we can say heat is evolved when an acid reacts with base.

Acid + Base " Salt + Water + Heat

HCI + NaOH " NaCI + H2O + Heat

Hydrochloric Sodium Sodium Water
acid hydroxide chloride

The process due to which an acid completely reacts with a base with the evolution
of heat to form salt and water as the only products is called neutralization.

ACIDS, BASES AND SALTS 63

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

damage the walls of the stomach and can contain acids. If these wastes are directly
cause stomach ulcers. discharged in a river or a lake, they kill the
To relieve indigestion, doctor's prescribe fish and other living organisms. Thus to
antacid tablets or syrup. It contains milk of prevent such a situation, the wastes are
magnesia (magnesium hydroxide) and treated with lime which neutralises acids.
aluminium hydroxide. These hydroxides
neutralise excess hydrochloric acid, and (d) Stings of Ants and Bees
hence, help in controlling acidity of The stings of ants and bees
stomach. contain formic acid when these insects
sting, they inject formic acid in our body
(b) Soil Treatment which causes a painful irritation and
Plants grow well only in the neutral swelling. To reduce the effect of formic
soil. However, sometimes a neutral soil acid, the area around the sting is rubbed
gets acidic due to the excessive use of with soap or baking soda solution or
artificial fertilizers. The soil also gets calamine, which contains zinc carbonate.
acidic, if the roots of harvested crop are These substances neutralise the effect of
allowed to decay in it. This in turn reduces formic acid to some extent and hence
the fertility of the soil. In order to convert help in relieving pain.
acidic soils into neutral soils farmers
spray it with calcium oxide (quick lime) or (e) Preserving Milk for a Short
calcium hydroxide (slaked lime). These Period
chemicals neutralize soil acids and hence Milk is brought to the cities from the

soil becomes neutral. villages by the milk vendors. In hot climate

Some soils are naturally basic in the natural bacteria present in the milk
nature. In order to make these soils produces a large amount of lactic acid,
neutral, a large amount of organic manure which curdles the milk, thereby causing a
is added. The acids present in the organic loss to milk vendors. To prevent the ill
manure neutralize the basic chemicals in effect of lactic acid the milk vendor adds a
the soil and make it neutral. small amount of baking soda to the milk.
This in turn neutralizes lactic acid and the
( C) Factory Wastes milk does not curdle.
The wastes of many factories

ACIDS, BASES AND SALTS 64

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Acid Acidic Base

Basic Indicator Neutral
Neutralization Salt

What you have learnt

S Acids are sour in taste. They turn blue litmus red, china rose solution deep pink, but do
not affect turmeric solution and phenolphthalein solution.
S Bases are bitter in taste and have a soapy touch. They turn red litmus blue, china rose
solution green, turmeric solution reddish brown and phenolphthalein solution pink.
S The substances which change their colour on coming in contact with acid or base are
called indicators.
S When an acid neutralizes a base, the products of reaction are salt and water. It always
proceeds with the evolution of heat.
S A neutral solution is neither acidic nor basic and the indicators do not show any change
in colour in it.

EXERCISES
(I). Fill in the blank spaces by choosing correct words from the list given below:
List: bitter, ants, corrosive, citric, soapy, slaked lime.
1. The acid found in lemons is ____________acid.
2. The bases have a ______________taste and __________touch.
3. The sting of the _______________contains formic acid.
4. Sulphuric acid is highly ___________acid.
5. Acidic soils are neutralized with _____________.
(II) Statements given below are incorrect. Write the correct statements.
1. Sulphuric acid is an example of an organic acid.
2. Blue litmus paper turns red in a basic solution.
3. China rose solution turns green in citric acid solution.
4. Formic acid is found in the sting of a grasshopper.
5. During neutralization, an acid reacts with a salt to from water and a base, as

ACIDS, BASES AND SALTS 65

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

products.
(III) Write true or false in front of the following statements:
Statement True \False
1. Tooth decay is caused by the presence of basic substance in mouth. _______
2. The substance which shows different colours in acids and bases are called
indicators. _______
3. Milk of magnesia and slaked lime are the examples of neutral substances.
_______
4. Acid rain is caused by the excess of carbon dioxide in air. _______
5. Potassium hydroxide turns blue litmus red. _______
6. Most of the fruits contain organic acids. _______

Answer the following questions :

1. Name three organic and three inorganic acids.
2. What are indicators ? Name any three indicators and state the colour change
which takes place in (i) acids (ii) bases.
3. What are neutral substances ? Give examples of two neutral substances.
4. You are given three unlabelled bottles A , B and C, containing colourless
solutions, such that one of them is acid, the other being basic and neutral.
How will you distinguish between them by using china rose as an indicator.
5. What do you understand by the term neutralisation ? Describe an activity in
which neutralisation of hydrochloric acid takes place with sodium hydroxide,
using phenolphthalein as an indicator.
6. Explain Why :
(a) Farmers add slaked lime to acidic soils.
(b) Soap solution or baking soda paste is applied on the part of body stung by
a bee.
(c) Factory wastes and city sewerage is neutralised before discharging in
rivers.
(d)Antacids are used for relieving stomach activity.
7. Give four differences between the acids and the alkalis.
8. Write an equation when hydrochloric acid neutralises sodium hydroxide.

ACIDS, BASES AND SALTS 66

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

MCQS : Choose the correct answer.

1. Name the acid which is present in the sting of ants
(a) Acetic acid (b) Formic acid (c) Oxalic acid (d) Tartaric acid

2. Blue litmus turns red in which solution:

(a) Acidic solution (b) Basic solution (c) Both acidic and basic solutions
(d) Neutral solution
3. Which of the following is not a mineral acid ?
(a) Hydrochloric acid (b) Sulphuric acid (c) Citric acid (d) Nitric acid

4. When few drops of china rose solution is added to shampoo taken in test tube the colour of
the solution becomes:
(a) Blue (b) Red (c) Green (d) Deep Pink

Extended Learning - Activities and Projects

1. Make a concentrated solution of baking soda in about 10 ml of water. With the help of a
cotton bud write a message on a white sheet of paper using baking soda solution as an ink.
Allow the paper to dry in the sun.
Cut a piece of fresh beet root and rub it over the invisible message written on the white
paper. Using your knowledge of acids/bases/indicators, explain your observations.
2. Collect a sample of soil from your garden and make its suspension in water. Filter the
suspension and obtain the clear filtrate. Test the filtrate with litmus solution and find out
whether the filtrate and hence the garden soil is acidic / basic / neutral.
3. Take a white paper and soak it in the turmeric solution. Take out the paper and dry it in the
sun. Take some soap solution in a small bowl. With the help of cotton bud make any
drawing of your choice on the dried turmeric paper, using soap solution as ink. Record your
observations and discuss them with your friends.

ACIDS, BASES AND SALTS 67

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

6 PHYSICAL AND CHEMICAL CHANGES

E very day you come across many 6.1 PHYSICAL CHANGES

changes in your surroundings. Activity 6.1
Cut a piece of paper in four square
These changes may involve one
pieces. Cut each square piece further into
or more substances. For example, your
four square pieces. Lay these pieces on
mother may ask you to dissolve sugar in
the floor or a table so that the pieces
water to make a cold drink. Making a sugar
acquire the shape of the original piece of
solution is a change. Similarly, setting curd
paper (Fig.6.1).
from milk is a change. Sometimes milk
Obviously, you cannot join the
becomes sour. Souring of milk is a
pieces back to make the original piece, but
change. Stretched rubber band also
is there a change in the property of the
represents a change. Make a list of ten
paper?
changes you have noticed around you.
In this chapter we shall perform some
Activity 6.2
activities and study the nature of these
Collect the chalk dust lying on the floor
changes. These changes are of two kinds,
near the blackboard in your classroom. Or,
physical and chemical.
crush a small piece of chalk into dust. Add
a little water to the dust to make a paste.
Roll it into the shape of a piece of chalk.
Let it dry.
Did you recover chalk from the
dust?

Activity 6.3
Take some ice in a glass or plastic tumbler.
Melt a some portion of ice by placing the
tumbler in the sun. You have now a
mixture of ice and water. Now place the

Fig.6.1 Paper pieces tumbler in a freezing mixture (ice plus

PHYSICAL AND CHEMICAL CHANGES 68

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

common salt).
Does the water become solid ice Remove the blade from the flame.
once again? Observe the tip once again after some time.

Activity 6.4
Does it get back its original colour?
Boil some water in a container. Do you see
In Activities 6.1 and 6.2 above, you
the steam rising from the surface of
saw that paper and a piece of chalk
water? Hold an inverted pan by its handle
underwent changes in size. In Activities 6.3
over the steam at some distance from the
and 6.4, water changes its state (from solid
boiling water. Observe the inner surface of
to liquid or from gas to liquid). In Activity
the pan.
6.5, the hack-saw blade changed colour on
Do you see any droplet of water there?
heating.
Activity 6.5 Properties such as shape, size,
colour and state of a substance are called its
CAUTION
physical properties. A change in which a
Be careful while handling a flame.
substance undergoes a change in its
Hold a used hack-saw blade with a physical properties is called a physical
pair of tongs. Keep the tip of the free end change. A physical change is generally
on the flame of a gas stove. Wait for a few reversible. In such a change no new
minutes. substance is formed.
Does the colour of the tip of the Let us consider the other kind of
blade change? change.

Fig.6.2: Rusting of iron

PHYSICAL AND CHEMICAL CHANGES 69

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(Fig. 6.3). When it is completely burnt it

6.2 CHEMICAL CHANGE leaves behind a powdery ash.
A change with which you are quiet Does the ash look like the
familiar is the rusting of iron. If you keep a magnesium ribbon?
piece of iron in the open for some time; it
acquires a film of brownish substance.
This substance is called rust and the
process is called rusting (Fig. 6.2). Iron
gates of parks or farmlands, iron benches
kept in lawns and gardens, and almost
every article of iron, kept in the open gets
rusted. At home you must have seen
shovels and spades getting rusted when
exposed to the atmosphere for some
time. In the kitchen, a wet iron pan (tawa)
often gets rusted if left in that state for
sometime. Rust is not iron. It is different
from iron on which it gets deposited.
Let us consider a few more
changes where new substances are Fig.6.3: Magnesium ribbon burning
formed.
The change can be represented by
Activity 6.6 the following equation:
( To be demonstrated by the teacher)
Magnesium (Mg) + Oxygen (O2)
CAUTION Magnesium oxide (MgO)
It is dangerous to look for long at the
The equations here are different from
burning magnesium ribbon. The
teachers should advise children not to those in mathematics. In equations of
stare at the burning ribbon. this kind, the arrow implies 'becomes'.
No attempt should be made to balance
Get a small piece of thin strip or chemical equations at this stage.
ribbon of magnesium. Clean its tip with
sandpaper. Bring the tip near a candle Collect the ash and mix it with a
flame. It burns with a brilliant white light small amount of water. Stir the mixture

PHYSICAL AND CHEMICAL CHANGES 70

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(aqueous solution) well. Test the mixture Activity 6.7

with blue and red litmus papers. (To be demonstrated by the teacher)
Does the mixture turn red litmus Dissolve about a teaspoonful of
blue? copper sulphate (blue vitriol or neela
Does the mixture turn blue litmus red? thotha) in about half a cup of water in a
On the basis of this test, how do glass tumbler or a beaker. Add a few drops
you classify the aqueous solution - acidic of dilute sulphuric acid to the solution. The
or basic? solution becomes blue in colour. Save a
On dissolving the ash in water it
small sample of the solution in a test tube
forms a new substance. This change can
or a small glass bottle. Drop a nail or a
be written in the from of the following
used shaving blade into the remaining
equation:
solution. Wait for half an hour or so.
Magnesium oxide (MgO) + water
Observe the colour of the solution.
(H2O) Magnesium hydroxide [Mg(OH)2].
Compare it with the colour of the sample
As you have already learnt in
solution saved separately (Fig. 6.4).
Chapter 5, magnesium hydroxide is a Do you see any change in the
base. So, magnesium oxide is a new colour of the solution?
substance formed on burning of Take out the nail or the blade.
magnesium. Magnesium hydroxide is The changes that you notice are due to a
another new substance formed by mixing reaction between copper sulphate and
magnesium oxide with water. iron. The change of colour of the solution

Fig.6.4: Change in colour of the copper sulphate

solution due to reaction with iron

PHYSICAL AND CHEMICAL CHANGES 71

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

from blue to green is due to the formation The reaction between carbon
of iron sulphate, a new substance. The dioxide and lime water is as follows:
brown deposit on the iron nail is copper, Carbon dioxide (CO2) + Lime water
another new substance. We can write the [Ca(OH)2] Calcium carbonate (CaCO3)
reaction as: + water (H2O)
Copper sulphate solution (blue) + Iron When carbon dioxide is passed
Iron sulphate solution (green) + copper through lime water, Calcium carbonate is
(brown deposit) formed, which makes lime water milky.
Activity 6.8 The turning of lime water into milky
Take about a teaspoonful of vinegar in a
appearance is a standard test of carbon
test tube. Add a pinch of baking soda to it.
dioxide. You will use it in Chapter 10 to
You would hear a hissing sound and see
show that the air we breathe out is rich in
bubbles of a gas coming out. Pass this
carbon dioxide.
gas through freshly prepared lime water In Activities 6.6 - 6.8, you saw that
as shown in Fig. 6.5. in each change, one or more new
substances were formed. In Activity 6.6,
the ash was the new substance formed
when magnesium was burnt. In Activity
Carbon
dioxide 6.7, the reaction of copper sulphate with
iron produced iron sulphate and copper.
Vinegar +
Baking soda Both of these are new substances.
Copper was deposited on the shaving
Lime blade of iron. In Activity 6.8, vinegar and
Water
baking soda together produced carbon
Fig.6.5: Set up to pass gas through lime water dioxide, which turned lime water milky.
Can you name the new substance formed
What happens to the lime water?
in this reaction?
The change in the test tube is as
A change in which one or more
follows:
new substances are formed is called a
Vinegar (Acetic acid)+Baking soda
chemical change. A chemical change is
(Sodium hydrogen carbonate) Carbon
also called a chemical reaction.
dioxide + other substances
Chemical changes are very

PHYSICAL AND CHEMICAL CHANGES 72

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

important in our lives. All new substances change. You know that such an explosion
are formed as a result of chemical produces heat, light, sound and
changes. For example, if a metal is to be unpleasant gases that pollute the
extracted from an ore, such as iron from atmosphere. That is way you are advised
iron ore, we need to carry out a series of not to play with fireworks.
chemical changes. A medicine is the end When food gets spoiled, it
product of a chain of chemical reactions. produces a foul smell. Shall we call this
Useful new materials, such as plastics and change a chemical change?
detergents, are produced by the chemical You must have noticed that a slice

reactions. Indeed, every new material is of an apple acquires a brown colour if it is

discovered by studying chemical not consumed immediately. If you have

changes. not seen this change in colour, cut a fresh

We have seen that one or more slice of apple and keep it away for some
new substances are produced in chemical time. Repeat the same activity with a slice
changes. In addition to new products, the of potato and brinjal. The change of colour
following may accompany a chemical in these cases is due to the formation of
change: new substances. Are not these changes
Heat, light or any other radiation (ultra- chemical changes?
violet, for example) may be given off or In Chapter 5, you neutralized an
absorbed. acid with a base. Is neutralization a
Sound may be produced. chemical change?
A change in smell may take place or a
You must have heard of the ozone layer
new smell may be given off.
in our atmosphere. It protects us from the
A colour change may take place. harmful ultraviolet radiations which come
A gas may be formed. from the sun. Ozone absorbs this radiation
Let us look at some examples. and breaks down to oxygen. Oxygen is
You saw that burning of magnesium different from ozone. Can we call the
ribbon is a chemical change. Burning of breakdown of ozone a chemical change?
If ultraviolet radiation were not absorbed
coal, wood or leaves is also a chemical
by ozone, it would reach the earth's
change. In fact, burning of any substance surface and causes harm to us and other
is a chemical change. Burning is always life forms. Ozone acts as a natural shield
against this radiation.
accompanied by production of heat.
Explosion of fire-work is a chemical

PHYSICAL AND CHEMICAL CHANGES 73

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

6.3 RUSTING OF IRON This process of depositing a layer

Let us get back to rusting. This is one of zinc on iron is called galvanization.
change that affects iron articles and slowly The iron pipes we use in our homes to
destroys them. Since iron is used in carry water are galvanized to prevent
making bridges, ships, cars, truck bodies rusting.
and many other articles, the monetary You know that ships are made of
loss due to rusting is huge. iron and a part of them remains under
The process of rusting can be water. On the part above water also ,water
represented by the following equation: drops keep clinging to the ship's outer
Iron (Fe) + Oxygen (O2, from the air) + surface. Moreover, the water of the sea
water (H2O) rust (Iron oxide Fe2O3) contains many salts. The salt water
For rusting, the presence of both makes the process of rust formation
oxygen and water (or water vapour) is faster.
essential. Therefore, ships suffer a lot of damage
In fact, if the content of moisture in from rusting in spite of being painted. So
air is high, which means if it is more humid, much so, that a fraction of ship's iron has
rusting becomes faster. to be replaced every year. Can you
So, how do we prevent rusting? imagine the monetary loss to the world?
Prevent iron articles from coming in
Stainless steel is made by mixing iron
contact with oxygen, or water, or both. with carbon and metal like chromium,
One simple way is to apply a coat of paint nickel, and manganese. It does not
rust.
or grease. In fact, these coats should be
applied regularly to prevent rusting.
Another way is to deposit a layer of a
6.4 CRYSTALLISATION
metal like chromium or zinc on iron. You know that salt can be obtained by the
evaporation of sea water. The salt
obtained in this manner is not pure and its
Oh, that is why my friend crystals are small. The shape of the
Sarish is always complaining
crystals cannot be seen clearly. However,
about iron articles rusting so
fast. She lives near the coast. large crystals of pure substances can be
formed from their solutions. The process
is called crystallization. It is an example

PHYSICAL AND CHEMICAL CHANGES 74

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

of a physical change. for some more time. You have learnt

Activity 6.9 about physical and chemical changes. Try
(To be performed in the presence of the to identify changes that you observe
teacher) around you as physical or chemical
changes.
CAUTION
Use only dilute sulphuric acid. Be careful
while boiling water. Copper sulphate

Take a cupful of water in a beaker

and add a few drops of dilute sulphuric
acid. Heat the water. When it starts boiling
add copper sulphate powder till no more
powder can be dissolved. Filter the
solution. Allow it to cool. Do not disturb the
solution when it is cooling. Look at the Crystals
Fig.6.6: Crystals of copper sulphate
solution after some time. Can you see the
crystals of copper sulphate? If not, wait

Chemical change Crystallization Physical change

Chemical reaction Galvanization Rusting

What you have learnt

Changes can be of two types, physical and chemical.
Physical changes are changes in the physical properties of substances.
No new substances are formed in these changes. These changes may be
reversible.
In chemical changes new substances are produced.
Some substances can be obtained in pure state from their solutions by
crystallization.

PHYSICAL AND CHEMICAL CHANGES 75

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
1. Classify the changes involved in the following processes as physical or
chemical changes
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminum to make aluminum foil
(f) Digestion of food
2. State whether the following statements are true or false. In case a
statement is false, write the corrected statement in your notebook.
(a) Cutting a log of wood into pieces is a chemical change. (True /False)
(b) Formation of manure from leaves is a physical change. (True/False)
(c) Iron pipes coated with zinc do not get rusted easily. (True/False)
(d) Iron and rust are the same substances. (True/False)
(e) Condensation of steam is not a chemical change. (True/False)
3. Fill in the blanks in the following statements:
(a) When carbon dioxide is passed through lime water, it turns milky due to the
formation of _______________ .
(b) The chemical name of baking soda is _____________.
(c) Two methods by which rusting of iron can be prevented are
__________and_____________.
(d) Changes in which only _________properties of a substance change are
called physical changes.
4. When baking soda is mixed with lemon juice, bubbles are formed with evolution
of a gas. What type of change is it? Explain.
5. When a candle burns, both physical and chemical changes take place. Identify
these changes. Give another example of a familiar process in which both the
chemical and the physical changes take place.
6. How would you show that setting of curd is a chemical change?
7. Explain why burning of wood and cutting it into small pieces are considered as

PHYSICAL AND CHEMICAL CHANGES 76

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

two different types of changes.

8. Describe how crystals of copper sulphate are prepared ?
9. Explain how painting of an iron gate prevents it form rusting ?
10. Explain why rusting of iron objects is faster in coastal areas than in deserts ?
11. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the
cylinder it exists as a liquid .When it comes out from the cylinder it becomes a
gas (change-A) then it burns (change-B) .The following statements pertain to
these changes. Choose the correct one.
(i) Process - A is a chemical change.
(ii) Process - B is a chemical change.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.
12. Anaerobic bacteria digest animal waste and produce bio gas (change-A).The
bio gas is then burnt as fuel (change B). The following statements pertain to
these changes.
Choose the correct one.
(i) Process - Ais a chemical change.
(ii) Process - B is a chemical change.
(iii) Both processes A and B are chemical changes.
Choose the correct one
13. Rust is
(a) Carbon dioxide (b) Iron
(c) Oxygen (d) Iron oxide.
14. Which of the following is not a physical change?
(a) Rusting of iron (b) Melting of ice
(c) Freezing of water (d) Dissolving sugar in water.

Extended Learning - Activities and Projects

1. Describe two changes that are harmful. Explain why you consider them
harmful. How can you prevent them?
2. Take three glass bottles with wide mouths. Label them A, B and C. Fill about

PHYSICAL AND CHEMICAL CHANGES 77

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

half of bottle A with ordinary tap water. Fill bottle B with water which has been
boiled for several minutes, to the same level as in A. In bottle C, take the same
boiled water and of the same amount as in other bottles. In each bottle put a few
similar iron nails so that they are completely under water. Add a teaspoon ful of
cooking oil to the water in bottle C so that it forms a film on its surface. Put the
bottles away for a few days. Take out nails from each bottle and observe them.
Explain.
3. Prepare crystals of alum.
4. Collect information about the types of fuels used for cooking in your area.
Discuss with your teachers / parents / others which fuels are less polluting and
why?

DO YOU KNOW?

Near the Qutub Minar in Delhi stands an

iron pillar (Fig. 6.7) which is more than 7 metres
high. It weighs more than 6000kg. It was built
more than 1600 years ago. After such a long
period it has not rusted. For its quality of rust
resistance it has been examined by scientists
from all parts of the world. It tells something
about the advances India had made in metal
technology as back as 1600 years ago.
Fig.6.7 Iron pillar

PHYSICAL AND CHEMICAL CHANGES 78

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE

D
o you remember the things that We find the daily weather report
you were asked to pack when carries information about the
you were heading for a hill temperature, humidity and rainfall during
station? When the sky is cloudy, your the past 24 hours. It also predicts the
parents insist that you carry an umbrella. weather for the day. Humidity, as you
Have you heard elders in your family might know, is a measure of the moisture
discuss the weather before planning a in air.
family function? You must have also
WEATHER
heard the experts discussing the weather
0 0
before the start of a game. Max 16.1 C /Min 2.6 C
Have you ever wondered why? Sunset: Tuesday - 5.41 pm
Sunrise: Wednesday -7.15 am
The weather may have a profound effect Moonset: Wednesday - 11.13 am
Moonrise: Tuesday - 11.05 pm
on the game. It has a profound effect on
Mist/Fog in the morning. Partly cloudy sky. Min
0
our lives. Many of our daily activities are temp will be around 4 C. Max humidity on
Monday 83% and Min 37%
planned based on the weather predicted
Fig.7.1: A sample of a weather report
for that day. There are daily reports of the from a newspaper
weather on the television and radio and in
the newspapers. But do you know what
this weather really is? I wonder who prepares
In this chapter, we will study about these reports!

the weather and climate. We will also see

how different forms of life are adapted to
the climate of their habitat. The weather reports are prepared by
the Meteorological Department of the
Government. This department
7.1 WEATHER collects data on temperature, wind,
In Fig. 7.1, a sample of weather etc., and makes the weather
report from a newspaper is given. prediction.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
79
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 7.1 Do all the seven days have the

Cut out the weather reports of the same maximum and minimum

last week from any newspaper. If you do temperatures, humidity and rainfall? The

not get a newspaper at home, borrow maximum and minimum temperatures

from your neighbours or friends and copy recorded may be the same for some of the

these reports in your notebook. You can days. However, all the parameters are not

also collect weather reports from a library. the same on any two days. Over a week

Paste all the cut-outs on a white sheet or there may be considerable variation. The

on a chart paper. day-to-day condition of the

Now record the information from atmosphere at a place with respect to
the weather reports collected by you in the temperature, humidity, rainfall,
Table 7.1. The first row is just a sample. wind speed, etc., is called the weather
Fill all the columns according to the data at that place. The temperature, humidity,
in the chart that you have prepared. and other factors are called the elements
of the weather. The weather of a place
Rainfall is measured by an
changes day after day and week after
instrument called the rain gauge. It is
week. That is why we often say. “today's
basically a measuring cylinder with a
weather is too humid", or “the weather
funnel on top to collect rainwater.
was warm last week”.
Table 7.1
Weather data of a week
Date Max. Min. Min. Max. Rainfall*
temp.(0C) temp.(0C) humidity (%) humidity(%) (mm)
23-08-06 36.2 27.8 54 82

*(Rainfall may not be recorded for all the days since it may not rain every day. Leave the space for
rainfall blank if the data is not available.)

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
80
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

The weather is such a complex Look at the graph below which

phenomenon that it can vary over very shows the maximum temperature
short periods of time. It can happen recorded during 03 August 2006 to 09
sometimes that it is sunny in the morning, August, 2006 at Shillong, Meghalaya
but suddenly clouds appear from (Fig.7.2).
nowhere and it starts raining heavily. Or, a As it is clear from any weather
heavy rain may vanish in a matter of report, the maximum and minimum
minutes and give way to bright sunshine. temperatures are recorded everyday. Do
You must have had several such you know how these temperatures are
experiences. Try to recall any such recorded. In chapter 4 you have learnt
experience and share it with your friends. that there are special thermometers for
Since weather is such a complex this purpose, called maximum and
phenomenon, it is not easy to predict. minimum thermometers. Can you

Date Maximum
temperature
0
03.08.06 26.0 C
0
04.08.06 23.5 C
0
05.08.06 25.0 C
0
06.08.06 22.0 C
0
07.08.06 25.5 C
0
08.08.06 23.3 C
0
09.08.06 24.4 C

Fig.7.2: Graph showing the variation of maximum temperature during 03 to 09 August, 2006

All changes in the weather are caused by the sun. The sun is a huge sphere of
hot gases at a very high temperature. The distance of the sun from us is very large. Even
then the energy sent out by the sun is so huge that it is the source of all heat and light on
the earth. So, the sun is the primary source of energy that causes changes in the weather.
Energy absorbed and reflected by the earth's surface, oceans and the atmosphere play
important roles in determining the weather at any place. If you live near the sea, you would
have realized that the weather at your place is different from that of a place in a desert, or
near a mountain

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
81
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

guess when during the day we have the over a long time, say 25 years, is called
maximum temperature and when the the climate of the place. If we find that
minimum? the temperature at a place is high most of
the time, then we say that the climate of
I wonder why weather that place is hot. If there is also heavy
changes so frequently! rainfall on most of the days in the same
place, then we can say that the climate of
What is the source of weather
that place is hot and wet.
in the place?
In Table 7.2 and 7.3 we have
given the climate condition at two places
The maximum temperature of in India. The mean temperature for a
the day occurs generally in the afternoon given month is found in two steps. First we
while the minimum temperature occurs find the average of the temperatures
generally in the early morning. Can you recorded during the month. Second, we
now understand why in summers we feel calculate the average of such average
so miserable in the afternoon and temperatures over many years. That
comfortable early in the morning? gives the mean temperature. The two
What about the times of sunrise places are: Srinagar in Jammu and
and sunset? You know that in winters it Kashmir, and Thiruvananthapuram in
becomes dark early and you do not get Kerala.
much time to play. Are the days shorter in By looking at Tables 7.2 and 7.3
winter than summer? Try to find it out we can easily see the difference in the
yourself by completing the project given climate of Jammu and Kashmir and
at the end of the chapter. Kerala. We can see that Kerala is very hot
and wet in comparison to Jammu and
7.2 CLIMATE
Kashmir, which has a moderately hot and
Met eorologists record t he wet climate for a part of the year.
weather everyday. The records of the Similar data for the western
weather have been preserved for the past region of India, for example Rajasthan,
several decades. These help us to will show the temperature is high during
determine the weather pattern at a place. most part of the year. But during winter,
The average weather pattern taken which lasts only for a few months, the

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
82
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Table 7.2: Srinagar (Jammu & Kashmir) Table 7.3: Thiruvananthapuram (Kerala)
Information about climate Information about Climate
Month Mean Temperature Mean Month Mean Temperature Mean
0 0
C total C total
Daily Daily rainfall Daily Daily rainfall
minimum maximum (mm) minimum maximum (mm)
Jan -2.3 4.7 57 Jan 22.2 31.5 23
Feb -0.6 7.8 65 Feb 22.8 31.9 24
Mar 3.8 13.6 99 Mar 24.1 32.6 40
Apr 7.7 19.4 88 Apr 24.9 32.6 117
May 10.7 23.8 72 May 24.7 31.6 230
Jun 14.7 29.2 37 Jun 23.5 29.7 321
July 8.2 30.0 49 July 23.1 29.2 227
Aug 17.5 29.7 70 Aug 23.2 29.4 138
Sep 12.9 27.8 33 Sep 23.3 30.0 175
Oct 6.1 21.9 36 Oct 23.3 29.9 282
Nov 0.9 14.7 27 Nov 23.1 30.3 185
Dec -1.6 8.2 43 Dec 22.6 31.0 66
(Note: The numbers for the mean total rainfall have been rounded off)
temperature is quite low. This region the conditions in which they live. Animals
receives very little rainfall. This is the living in very cold and hot climate must
typical desert climate. It is hot and dry. possess special features to protect
The northeastern India receives rain for a themselves against the extreme cold or
major part of the year. Therefore, we can heat. Recall from your class VI science
say that the climate of the north-east is book the definition of adaptation.
wet. In our state climatic conditions are Features and habits that help animals to
different at different places. In Jammu adapt to their surroundings are a result of
region temperature at times shoot upto 46 the process of evolution.
o
C.On the contrary in Ladakh temperature In chapter 9 you will learn about the
o
falls as low as -23 C. effect of weather and climate on soil. Here
we will study the effect of climate on
7.3 CLIMATE AND ADAPTATION animals only. In class VI, you have read
Climate has a profound effect on about adaptations of animals to certain
living organisms. habitats. As examples of adaptation of
Animals are adapted to survive in animals to climatic conditions, we discuss

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
83
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

only animals living in Polar Regions and extreme climate. These regions are
tropical rainforests. covered with snow and it is very cold for
most part of the year. For six months the
Some animals that have adapted sun does not set at the poles while for the
to the Himalayan climate include the other six months the sun does not rise. In
mountain goat, which has a thick wat for winters, the temperatures can be as low
warmth and strong hooves for running up O
as-37 C. Animals living there have
the rocky slopes.
adapted to these severe conditions. Let
The wild Yak is a bulky species
us see how they are adapted by
with high capacity and a thick coat which
considering the examples of polar bears
are adaptations to the high altitude
and penguins.
environment of Tibet.
Polar bears have white fur so that
they are not easily visible in the snowy
As the name suggests, the Polar
white background. It protects them from
Regions are situated near the poles, i.e.,
their predators. It also helps them in
north pole and south pole.
catching their prey. To protect them from
Some well-known countries that
extreme cold, they have two thick layers
belong to the polar regions are Canada,
of fur. They also have a layer of fat under
Greenland, Iceland, Norway, Sweden, their skin. In fact, they are so well-
Finland, and Alaska in U.S.A. and insulated that they have to move slowly
Siberian region of Russia. and rest often to avoid getting
Examples of some countries overheated.
where the tropical rainforests are found Physical activities on warm days
are India, Malaysia, Indonesia, Brazil, necessitate cooling. So, the polar bear
Republic of Congo, Kenya, Uganda, and goes for swimming. It is a good swimmer.
Nigeria. Its paws are wide and large, which help it
not only to swim well but also walk with
Activity 7.2 ease in the snow. While swimming under
Take an outline map of the world. Mark the water, it can close its nostrils and can
polar regions in blue. Similarly, mark the remain under water for long durations. It
tropical regions in red. has a strong sense of smell so that it can
(i) The Polar Regions catch its prey for food. We can understand
The polar regions present an the adaptations of polar bears with the

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
84
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

The white fur is not

Its predator and prey are It has a very strong
easily visible in the snowy
unable to see it sense of smell
white background

It has two thick layers It helps the bear to locate

of fur and catch its prey

These keep it warm in It has long curved

cold weather and sharp claws

The fat insulates its body from It has a layer of fat These help it to walk
cold and keeps it warm under its skin on ice

Fig. 7.3: Adaptations of polar bear

Fig. 7.5: Feet of Penguin

Fig. 7.4: Penguins huddled together
help of the flow chart shown in Fig 7.3. You may have seen pictures of penguins
Another well-known animal living huddled together. This they do to keep
in the polar regions is the penguin (Fig. warm. Recall how warm you feel when
7.4). It is also white and merges well with you are in a hall full of people.
the white background. It also has a thick Like polar bears, penguins are also
skin and a lot of fat to protect it from cold. good swimmer. Their bodies are

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
85
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

streamlined and their feet have webs,

making them good swimmers (Fig. 7.5).
Other animals living in the polar
regions are many types of fishes, musk
oxen, reindeers, foxes, seals, whales,
and birds. It is to be noted that while fish
can remain under cold water for long,
birds must remain warm to survive. They
migrate to warmer regions when winter Fig.7.6: Migratory birds in their habitat/
sets in. They come back after the winter is Migratory birds in flight.

over. You know probably that India is one The ladakh region is home to
of the destinations of many of these birds. many rare Himalayan birds including
You must have seen or heard about the Tibetan Snowcocks, griffon vultures
Siberian crane that comes from Siberia to and bearded vultures which have a 3 m
places like Bharatpur in Rajasthan and long wingspan. Many migratory birds
are seen in Ladakh including the
Sultanpur in Haryana, Gharana netland in
graceful Black-necked crane, which
Jammu and some wetlands of north east
can be seen flying in distinctive V-
and some other parts of India (Fig.7.6).
shaped formation across the clear
Himalayan sky.
There is an estimated 1.3 million
Do fishes and butterflies migratory birds in various wetlands of
also migrate like birds? the valley this year. The birds migrate
from Central Asia and China, Siberia
and Eastern Europe.
Avian visitors migrate to three
famous wetlands in valley viz; Haygam,
Hokersar and Shalibag. The other
prominent destination for the migratory
birds in the valley is at Mirgund.
Kashmir's Largest Wetland
Reserve is Shallabagh Wetland
Reserve.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
86
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

In the 29 wetlands surveyed in J&K, 106 temperature is generally higher than

0
species of birds were observed, of which about 15 C. During hot summers, the
0
25 species were land birds, temperatures may cross 40 C. Days and
occassionally visiting the wetlands, nights are almost equal in length
especially the drier parts. The highest throughout the year. These regions get
number of species (43) was in Tokhar plenty of rainfall. An important feature of
Tso in Ladakh region. Two threatened this region is the tropical rainforest.
species, namely the Blacknecked Crane Tropical rainforests are found in Western
(at 3 sites in Ladakh) and Sarus Crane Ghats and Assam in India. Southeast
(at Gharana, R.S. Pura) and nearly two Asia, Central America and Central Africa.
threatened species, viz. white-eyed Because of continuous warmth and rain,
Pochard (at 7 wetlands in state) and this region supports wide variety of plants
White ibis (at 2 wetlands in Jammu) were and animals. The major types of animals
observed. living in the rainforests are monkeys,
There is a blanket ban on bird apes, gorillas, lions, tigers, elephants,
shooting in the state. Most of the bird leopards, lizards, snakes, birds and
poaching reports during the winter came insects.
from north Kashmir, Baramulla district Let us read about the adaptations
where poachers reportedly shot many of these animals to a hot, humid climate.
birds in the Wullar Lake under the cover The clima tic conditions in

of darkness using guns loaded on their rainforests are highly suitable for

boats. supporting an enormous number and

Infact the migratory birds could be variety of animals. Since the numbers are
purchased at many places in North large, there is intense competition for food
Kashmir confirming (Poal Specific) that and shelter. Many animals are adapted to
poaching had not completely stopped. living on the trees. Red- eyed frog (Fig.
7.7) has developed sticky pads on its feet
to help it climb trees on which it lives. To
(ii) The Tropical Rainforests:
help them live on the trees, monkeys (Fig.
The tropical region has generally a hot
7.8) have long tails for grasping branches.
climate because of its location around the
Their hands and feet are such that they
equator. Even in the coldest month the
can easily hold on to the branches.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
87
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Toucan to reach the fruits on branches

which are otherwise too weak to support
its weight.

Fig.7.7: Red-eyed frog

Fig.7.9: Toucan

Many tropical animals have

sensitive hearing, sharp eyesight, thick
skin and a skin colour which helps them to
camouflage by blending with the
surrounding. This is to protect them from
predators. For example, big cats (lions
and tigers) have thick skins and sensitive
hearing.
The lion- tailed macaque (also
called Beard ape) lives in the rainforest of
Fig.7.8: A new world monkey
Western Ghats (Fig.7.10). Its most
outstanding feature is the silver- white
As there is competition for food, some
mane, which surrounds the head from the
animals are adapted to get food not easily
cheeks down to its chin. It is a good
reachable.A striking example is that of the
climber and spends a major part of its life
bird Toucan (Fig. 7.9), which possesses
on the tree. It feeds mainly on fruits. It also
a long, large beak. This helps a
eats seeds, young leaves, stems, flowers

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
88
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

and buds. This bearded ape also its tusks are modified teeth. These can
searches for insects under the bark of the tear the bark of trees that elephant loves
trees. Since it is able to get sufficient food to eat. So, the elephant is able to handle
on the trees, it rarely comes down on the the competition for food rather well. Large
ground. ears of the elephant help it to hear even
very soft sounds.

Fig.7.10: Lion-tailed macaque

Another well- known animal of

Indian tropical rainforest is the elephant
(Fig.7.11) . It has adapted to the
conditions of rainforests in many Fig.7.11: An Indian elephant
remarkable ways. Look at its trunk. It uses
it as a nose because of which it has a
They also help the elephant to
strong sense of smell. The trunk is also
keep cool in the hot and humid climate of
used by it for picking up food. Moreover,
the rainforest.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
89
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Adaptation Maximum Temperature Tropical rainforest

Climate Migration Tropical region

Elements of weather Minimum temperature Weather

Humidity Polar region

What you have learnt

§ The day- to- day condition of the atmosphere at a place with respect to the
temperature, humidity, rainfall, wind- speed, etc., is called the weather at that place.
§ The weather is generally not the same on any two days and week after week.
§ The maximum temperature of the day occurs generally in the afternoon while the
minimum temperature occurs in the early morning.
§ The times of sunrise and sunset also change during the year.
§ All the changes in the weather are driven by the sun.
§ The average weather pattern taken over a long time, say 25 years is called the
climate of the place.
§ The tropical and the polar regions are the two regions of the earth, which have
severe climatic conditions.
§ Animals are adapted to the conditions in which they live.
§ The polar regions are very cold throughout the year. The sun does not set for six
months in a year and in the other six months it does not rise.
§ Animals in the polar region are adapted to the extremely cold climate by having
some special characteristics such as white fur, strong sense of smell, a layer of fat
under the skin, wide and large paws for swimming and walking, etc.
§ Migration is another means to escape the harsh, cold conditions.
§ Because of the hospitable climatic conditions, huge populations of plants and
animals are found in the tropical rainforests.
§ Animals in the tropical rainforests are adapted such that they eat different kind of
food to overcome the competitions for food and shelter.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
90
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

§ Some adaptations of animals living in the tropical rainforests include living on the
trees, development of strong tails, long and large beaks, bright colours, sharp
patterns, loud voice, diet of fruits, sensitive hearing, sharp eyesight, thick skin,
ability to camouflage in order to protect themselves from predators, etc.

EXERCISES
1. Name the elements that determine the weather of a place.
2. When are the maximum and minimum temperatures likely to occur during the day?
3. Fill in the blanks:
(i) The average weather taken over a long time is called ______________
(ii) A place receives very little rainfall and the temperature is high throughout the
year, the climate of that place will be___________and ______________
(iii) The two regions of the earth with extreme climatic conditions are __________
and _____________
4. Indicate the type of climate of the following areas:
(a) Jammu and Kashmir: __________________
(b) Kerala: ___________________
(c) Rajasthan: ___________________
(d) North-east India: ___________________
5. Which of the two changes frequently, weather or climate?
6. Following are some of the characteristics of animals:
(i) Diets heavy on fruits (ii) White fur
(iii) Need to migrate (iv) Loud voice
(v) Sticky pads on feet (vi) Layer of fat under skin
(vii) Wide and large paws (viii) Bright colours
(ix) Strong tails (x) Long and large beak
For each characteristic, indicate whether it is adaptation for tropical rainforests or
polar regions. Do you think that some of these characteristics can be adapted for
both regions?
7. The tropical rainforest has a large population of animals. Explain why it is so?
8. Explain, With examples, why we find animals of certain kind living in particular
climatic conditions?
9. How do elephant living in the tropical rainforest adapt itself.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
91
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Choose the correct option which answers the following questions:

10. A carnivore with stripes on its body moves very fast while catching its prey. It is likely
to be found in
(i) polar regions (ii) deserts
(iii) oceans (iv)tropical rainforests
11. Which features adapted polar bears to live in extremely cold climate?
(i) A white fur, fat below skin, keen sense of smell.
(ii) Thin skin, large eyes, a white fur.
(iii) A long tail, strong claws, white large paws.
(iv) White body, paws for swimming, gills for respiration.
12. Which option best describes a tropical region?
(i) Hot and humid
(ii) Moderate temperature, heavy rainfall
(iii) Cold and humid
(iv) Hot and dry

Extending Learning - Activities and Projects

1. Collect weather reports of seven successive days in the winter months (preferably
December). Collect similar reports for the summer months (preferably June). Now
prepare a table for sunrise and sunset times as shown:
Table
June December
Date Sunrise Sunset Date Sunrise Sunset

Try to answer the following questions:

(i) Is there any difference in the time of sunrise during summer and winter?
(ii) When do you find that the sun rises earlier?
(iii) Do you also find any difference in the time of sunset during the month of June
and December?
(iv) When are the days longer?
(v) When are the nights longer?
(vi) Why are the days sometimes longer and sometimes shorter?
(vii) Plot the length of the day against the days chosen in June and December.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
92
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2. Collect information about the Indian Meteorological Department. If possible visit its
website: http// www.imd.gov.in.
Write a brief report about the things this department does.

DO YOU KNOW?

Rainforests cover about 6% of the earth's surface, but they have

more than half of the animal life and about two thirds of the
flowering plants of the planet. However, much of this life is still
unknown to us.

WEATHER, CLIMATE AND ADAPTATIONS

OF ANIMALS TO CLIMATE
93
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

8 WINDS, STORMS AND CYCLONES

O
But what are cyclones? How are
rrisa was hit by a cyclone with
they formed? Why are they so
wind Speed of 200 km/hr on 18
destructive? In this chapter we shall seek
October, 1999. The cyclone
answers to some of these questions.
smashed 45,000 houses making
We begin with some activities
7,00,000 people homeless. On 29
involving air. These activities will clarify
October the same year, a second cyclone
some basic features concerning a
with a speed of 260 km/hr hits Orrisa
cyclone. Before we begin, remember that
again. It was accompanied by water
the moving air is called the wind.
waves about 9m high. Thousands of
people lost their lives. Property worth
8.1 AIR EXERTS PRESSURE
crores of rupees was destroyed. The
Activity 8.1
cyclone affected agriculture, transport,
communication, and electricity supply. Whenever an activity involves
heating, be careful. It is advised that
such activities are performed in the
presence of an elderly person from
your family. Or, carry out these
activities in the presence of your
teacher.

You need to boil water in the

following activity.
Take a tin can with a lid. Fill it
approximately half with water. Heat the
can on a candle flame till the water boils.
Fig. 8.1: Image taken by a satellite of a cyclone
approaching the coast of Orissa
Let the water boil for a few minutes. Blow
out the candle. Immediately put the lid
Courtesy : India Meteorological Department,
New Delhi tightly on the can. Put the can carefully in

WINDS, STORMS AND CYCLONES 94

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

a shallow metallic vessel or a washbasin. the air exerts pressure. It is due to this
Pour fresh water over the can. What pressure that the leaves of trees,
happens to the shape of the can? banners, or flags flutter when the wind is
blowing. You can list some more
experiences which shows that the air has
pressure.
Let us now try to explain why the
can (or the bottle) gets distorted. As water
is poured over the can, some steam in the
can condenses into water, reducing the
amount of the air inside. The pressure of
air inside the can decreases the pressure
Fig. 8.2 : Can with hot water being cooled exerted by the air from outside the can. As
a result the can gets compressed.
Can you guess why the shape of
This activity again confirms that air
the can got distorted?
exerts pressure.
If you cannot get a tin can, take a
soft plastic bottle. Fill it with hot water.
8.2 HIGH SPEED WINDS ARE
Empty the bottle and immediately cap it
ACCOMPANIED BY REDUCED
tightly. Place the bottle under running
AIR PRESSURE
water.
ACTIVITY 8.2
Recall some of your experiences.
Crumble a small piece of the paper
When you fly a kite, does the wind blow
into a ball of size smaller than the mouth
from behind you?
of an empty bottle. Hold the empty bottle
Do you find it difficult to ride a
on its side and place the paper ball just
bicycle against the direction of the wind.
inside its mouth. Now try to blow on the
You know that we have to fill air into
ball to force it into the bottle. Try the
the bicycle, tube overfilled with air must
activity with bottle of different size.
burst. What is the air doing inside the
Challenge your friends if they can force
tube?
Discuss with your friends how the the paper ball in by blowing into the bottle.
Saba and Yasir are thinking about
air in the bicycle tube keeps it in shape.
All these experiences show that the following question:

WINDS, STORMS AND CYCLONES 95

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Why is it difficult to force the paper ball into Try different ways of blowing on
the bottle? the balloons to see what happens.

ACTIVITY 8.4
Can you blow and lift ?
Hold a strip of paper, 20cm long
and 3cm wide, between your thumb and
forefinger as shown in Fig.8.5. Now blow
over the paper.
Fig. 8.3 : Blowing into the bottle
Saba thinks that strip will be lifted
up. Yasir thinks that the strip will bend
ACTIVITY 8.3 down.
Blow the balloons
Take two balloons of approximately
equal size. Put a little water into the
balloons.

Fig. 8.4 : Blowing between the balloons

Blow up the balloons and tie each one to a

Fig. 8.5 : Blowing over a strip of paper
string. Hang the balloons 8-10 cm apart
on a cycle spoke or a stick. Blow in the
space between the balloons.
What did you expect? What What do you think will happen to
happens? the paper?

WINDS, STORMS AND CYCLONES 96

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

roofs of buildings? If the roofs were weak,

Let us try to understand the they could be lifted and blown away. If you
observations in Activity 8.2, 8.3 and 8.4. have any such experience, share it with
Were the observations along the your friends.
lines you thought? Do you get the feeling Let us try to understand how winds
that the increased wind speed is are produced, how they bring rain and
accompanied by a reduced air pressure? how they can be destructive sometimes.
When we blow into the mouth of You already know that when air
the bottle, the air near the mouth has moves, it is called wind. Air moves from
higher speed. This decreases the the region where the air pressure is
pressure there. The air pressure inside high to the region where the pressure
the bottle is higher than near the mouth. is low. The greater the difference in
The air inside the bottle pushes the ball pressure, the faster the air moves. But
out. how are the pressure differences created
In Activity 8.3 you saw that when in nature? Is the difference in temperature
you blew between the balloons, they involved? The following activities will help
moved towards each other. How could you to understand this.
this happen? This could happen if the
pressure of air between the balloons were
somehow reduced. The pressure outside
the balloons would then push them
towards each other.
In Activity 8.4 you saw that when Balloon tied over
the neck of the
boiling tube Balloon tube Balloon tube
you blew over the paper strip, it went immersed in immersed in
hot water ice-cold water
upwards. Again, this could happen if
blowing over the paper reduced the air
Fig. 8.6 : The shape of the balloon depicting
pressure above the strip. hot and cold water
We see that the increased wind
speed is, indeed, accompanied by a 8.3 AIR EXPANDS ON HEATING

reduced air pressure. Activity 8.5

Can you imagine what would Take a boiling tube. Stretch a
happen if high-speed winds blew over the balloon tightly over the neck of the tube.
You can use a tape to make it tight. Pour

WINDS, STORMS AND CYCLONES 97

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

some hot water in a beaker. Insert the candle below one of the bags as shown in
boiling tube with the balloon in the hot the figure. Observe what happens. Why is
water. Observe for 2-3 minutes for any the balance of the bags disturbed?
change in the shape of the balloon. Take
the tube out, let it cool down to the room
temperature. Take some ice cold water in
another beaker and place tube with the
balloon in cold water for 2-3 minutes.
Observe the change in the shape of the
balloon.
Think and try to answer :
What makes the balloon deflated when
the boiling tube is placed in hot water?
Can we infer from the first
observation that air expands on heating?
Can you now state what happens to the
Fig. 8.7 : Hot air rising up
air in the boiling tube when it cools down?
The next activity is very Does this activity indicate that
interesting. This will make you warm air rises up? As the warm air rises
understand more about hot air. up, it pushes the bag above the candle.
Does the disturbance of the balance
ACTIVITY 8.6
suggest that the warm air is lighter than
CAUTION the cold air?
Handle the burning candle carefully. Can you now explain why smoke
always rises up?
Take two paper bags or empty
Also, it is important that on heating
paper cups of the same size. Hang the
the air expands and occupies more
two bags in the inverted position on the
space. When the same thing occupies
two ends of a metal or wooden stick.
more space, it becomes lighter. The
Tie a piece of thread in the middle
warm air is, therefore, lighter than the
of the stick. Hold the stick by the thread
cold air. That is the reason why smoke
(Fig. 8.7) as in a balance. Put a burning
goes up.

WINDS, STORMS AND CYCLONES 98

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

8.4 WIND CURRENTS ARE

GENERATED DUE TO UNEVEN
I wonder why the winds shown
HEATING ON THE EARTH
in the figure are not in the exact
These situations are:
north-south direction.
(A) Uneven heating between
the equator and the poles
Yo u m i g h t h a v e l e a r n t i n
The winds would have flown in the
Geography that region close to the
north-south direction from north to south,
equator get maximum heat from the sun.
or from south to north. A change in
The air in these regions gets warm. The
directions is however, caused by the
warm air rises up, and the cooler air from
rotation of the earth.
the regions in the 0-30 degrees latitude
belt on either side of the equator moves
(B) Uneven heating of land
in. These winds blow from the north and
and water
the south towards the equator. At the
You have read about the sea breeze in
poles, the air is colder than that at
Chapter 4.
latitudes about 60 degrees. The warm air In summer, near the equator the
at these latitudes rises up and the cold land warms up faster and most of the time
wind from the polar regions rushes in, to the temperature of the land is higher than
take its place. In this way, wind circulation that of the water in oceans. The air over
is set up from the poles to the warmer the land gets heated and rises. This
latitudes, as shown in Fig. 8.8. causes the winds to flow from oceans
towards the land. These are monsoon
winds (Fig. 8.9).

The word monsoon is derived

from the Arabic word 'mausam'
which means 'season'.

In winter, the direction of the wind

Fig. 8.8 : The wind flow pattern because of flow gets reversed; it flows from the land
uneven heating on the earth.
to ocean (Fig. 8.10).

WINDS, STORMS AND CYCLONES 99

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

with clouds and rain. Sing and enjoy with

your friends, if you know such a song.
I want to know what these Here is one for you.
winds do for us. However, it is not always a happy
ending. Rains often create problems.
Can you list some of the
problems?
The winds from the ocean carry You can discuss the causes and
water and bring rain. It is a part of the solution of the problem with your teacher
water cycle. and parents.
The monsoon winds carry water In nature itself there are certain
and it rains. situations that can sometimes create
Clouds bring rain and give disaster and pose threat to humans,
happiness. Farmers in our country animals and plant life.
depend mainly on rains for their harvests. Let's study two such situations -
There are many folk songs associated thunderstorm and cyclones.

Roaring clouds across the sky

Tell us that monsoon's here
Dark and floating clouds then pour
Raindrops every where.
Clouds make lightning flash

overhead.
And irrigate fields with rain.
Clouds make earth, its fragrance

spreads
When wet with drops of rain,
Rising from the ocean vast
Clouds fill up with rain. Fig. 8.9 : Uneven heating of land especially the
Rajasthan desert generates monsoon winds from
Rain to ocean, back at last Southwest direction in summer. These winds
carry lots of water from the Indian Ocean.
To mingle with ocean again!

WINDS, STORMS AND CYCLONES 100

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

8.5 THUNDERSTORMS AND

CYCLONES
Thunderstorms develop in hot,
humid tropical areas like India very
frequently. The rising temperatures
produce strong upward rising winds.
These winds carry water droplets
upwards, where they freeze, and fall
down again. The swift movement of the
falling water droplets along with the rising

Fig. 8.10 : Uneven heating of land and water in

air creates lightning and sound. It is this
winter generates winds from the northwest event that we call a thunderstorm. You
colder land. These colder winds carry little
water, hence small amount of rain in winter. will read about lightning in higher classes
If a storm is accompanied by lightning,
we must take the following
DO YOU KNOW?
precautions:
The energy possessed by Wind is
called 'Wind Energy'. Denmark is
? Do not take shelter under an
called the country of 'Winds'. More
isolated tree. If you are in a forest
than 25% of their electricity needs are
take shelter under a small tree. Do
g e n e ra t e d t h r ou g h w i n d m i ll s .
not lie on the ground.
Germany ranks first whereas India ? Do not take shelter under an
ranks fifth in harnessing wind energy. umbrella with a Metallic end.
About 45,000 MW power can be ? Do not sit near a window. Open
generated if India's wind potential is garages, storage sheds, metal
fully exploited. sheds are not safe places to take
Largest Wind energy farm in shelter.
India is near Kanyakumari in Tamil ? A car or a bus is a safe place to take
Nadu and it generates 380 MW of shelter.
electricity. ? If you are in water, get out and go

. inside a building.

WINDS, STORMS AND CYCLONES 101

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

this heat is released in the atmosphere.

How a thunderstorm becomes a The heat released in the atmosphere

cyclone warms the air around. This air tends to

You know that water requires heat rise and causes a drop in pressure. More
when it changes from liquid to vapour air rushes to the centre of the storm. This
state. Does the water give back heat cycle is repeated. The chain of events
when vapour condenses into liquid? Can ends with the formation of a very low-
you recall any experience to support this? pressure system with very high-speed
winds revolving around it. It is this
Structure of a Cyclone weather condition that we call a cyclone.
Factors like wind speed, wind direction,
The centre of a cyclone is calm
temperature and humidity contribute to
area. It is called the eye of the storm. A
the development of cyclones.
large cyclone is a violently rotating
mass of air in the atmosphere, 10 to 15
km high. The diameter of the eye varies
from 10 to 30 km (Fig. 8.11). It is a
region free of clouds and has light
winds. Around this calm and clear eye
(Fig. 8.12), there is a cloud region of
about 150 km in size. In this region
there are high-speed winds (150-250
km/h) and thick clouds with heavy rain.
Away from this region the wind
gradually decreases. The formation of
Fig. 8.11 : Formation of a cyclone
a cyclone is a very complex process. A
8.6 DESTRUCTION CAUSED BY
model is shown in Fig. 8.11.
CYCLONES
Cyclone can be very destructive.
Before cloud formation, water
Strong winds push water towards the
takes up heat from the atmosphere to
shore even if the storm is hundreds of
change into vapour. When water vapour
kilometers away. These are the first
changes back to liquid form as raindrops,
indications of an approaching cyclone.

WINDS, STORMS AND CYCLONES 102

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

areas, causing severe loss of life and

property. It also reduces the fertility of the
soil.
Continuous heavy rainfall may
further worsen the flood situation.
High-speed winds accompanying
a cyclone can damag e h ouses,
telephones and other communication
systems, trees, etc., causing tremendous
Fig. 8.12 : The image of the loss of life and property.
‘eye’ of a cyclone

A cyclone is known by different

names in different parts of the world.
It is called a 'hurricane' in the
American continent. In Philippines
and Japan it is called a 'typhoon'
(Fig. 8.14).

Fig. 8.13 : Rising water caused by

a cyclone. The diameter of a tornado can be as
Courtesy : India Meteorological Department, small as a metre and as large as a km,
New Delhi
or even wider. The funnel of a tornado
The water produced by the wind
sucks dust, debris and everything near
are so powerful that a person cannot
overcome them. it at the base (due to low pressure) and
The low pressure in the eye lifts throws them out near the top. Here are
water surface in the centre. The rising a few accounts of the survivors of
water may be high as 3-12 meters tornados - (from Discovery Channel's
(Fig. 8.13). It appears like a water-wall "Young Discovery Series") .
moving towards the shore. As a result, the "I saw the cloud coming and
seawater enters the low-laying coastal tried to take shelter inside. But as soon

WINDS, STORMS AND CYCLONES 103

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Fig. 8.14 :Regions near the equator where cyclones exist.

as I reached for the doorknob, the situated deep inside or underground

house took off into the sky. I was not having no windows. Or otherwise it is
hurt at all." better to shut windows and take shelter
under a table, workbench, where
debris cannot reach. One has to bow
down on knees protecting head and
neck using arms (Fig. 8.15).

Tornadoes: In our country they are not

Fig. 8.15 : Protecting
from a tornado very frequent. A tornado is a dark funnel
shaped cloud that reaches from the sky to
"After the storm we had to the ground (Fig. 8.16). Most of the

clean the debris from the wheat fields. tornadoes are weak. A violent tornado
can travel at speeds of about 300 km/h.
We picked up splintered boards and
Tornadoes may form within cyclones.
tree branches as well as dead The whole coastline of India is
chickens with their feathers blown off vulnerable to cyclones, particularly the
and rabbits looked like they had been east. The west coast of India is less
skinned.” vulnerable to cyclonic storms both in
A tornado shelter is a room terms of intensity and frequency of the
cyclones.

WINDS, STORMS AND CYCLONES 104

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

8.7 EFFECTIVE SAFETY

MEASURES
? A cyclone forecast and warming
service.
? Rapid communication of warning
to the Government agencies, the
ports, fishermen, ships and to
general public.
? Construction of cyclone shelters
Fig. 8.16 : Image of a tornado in the cyclone prone areas, and
[National Server Storm Laboratory (NSSL)]
Courtesy : India Meteorological Department, Administrative arrangements for
New Delhi moving people fast to safer

We have learnt that all storms are low- places.

pressure systems. Wind speed plays

Action on the part of the people
an important role in the formation of
? We should not ignore the warnings
storms. It is, therefore, important to
issued by the meteorological
measure the wind speed. The
department through T.V, radio, or
instrument that measures the wind
newspaper.
speed is called an anemometer.
? We should make necessary
arrangements to shift the essential
household goods, domestic
animals and vehicles, etc, to safer
places; avoid driving on road; and
keep ready the phone number of
all emergency services like police,
fire brigade, and medical centres.
Some other precautions, if you are
staying in a cyclone hit area -
Fig. 8.17 : An anemometer for measuring the
speed of wind
? Do not drink water that could be
Courtesy : India Meteorological Department, contaminated. Always store drinking
New Delhi
water for emergencies.

WINDS, STORMS AND CYCLONES 105

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

? Do not touch wet switches and fallen less than a day to prepare or evacuate
power lines. their homes from an oncoming cyclone.
? Do not go out just for the sake of fun. The world today is very different. Thanks
? Do not pressurize the rescue force by to satellites and radars, a Cyclone alert
making undue demands. or Cyclone watch is issued 48 hours in
? Cooperate and help your neighbors
advanced of any expected storm and a
and friends.
cyclone warning is issued 24 hrs in
advance. The message is broadcast
8.8 ADVANCED TECHNOLOGY
every hour when a cyclone is nearer the
HAS HELPED
The se d ays we are b et ter coast. Several national and international

protected. In the early part of the last organizations cooperate to monitor the

century, coastal residence may have had cyclone -related disasters.

Anemometer Low pressure Tornado

Cyclone Monsoon winds Typhoon

Hurricane Pressure Wind flow pattern

Lightning Thunderstorms

What you have learnt

? Air around us exerts pressure.
? Air expands on heating and contracts on cooling.
? Warm air rises up, whereas comparatively cooler air tends to sink towards the
earth's surface.
? As warm air rises, air pressure at that place is reduced and the cooler air moves to
that place.
? The moving air is called wind.
? Uneven heating on the earth is the main cause of wind movements.

WINDS, STORMS AND CYCLONES 106

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

? Winds carrying water vapours bring rain.

? High-speed winds and air pressure difference can cause cyclones.
? It has become easier to monitor cyclones with the help of advance technology like
satellites and radars.
? Self-help is the best help. Therefore it is better to plan in advance and be ready with
defence against any approaching cyclone.
? The following flow chart will help you to understand the phenomena that leads to the
formation of clouds and falling of rain and creation of storms and cyclones:

Difference of temperature between two regions

Sets convection in air

Warm air rises, creating a low-pressure area

Cool air converges to the low pressure area

Warm air rises, cools and the water vapour

condense to form clouds

The bigger water drops in the cloud fall to the

ground as rain, hail and snow

Falling water droplets and rising air move

vigorously to produce thunderstorm

Under certain weather condition storms may

develop into cyclones.

WINDS, STORMS AND CYCLONES 107

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
1. Fill the missing words in the blank spaces in the following statements:
(a) Wind is __________air.
(b) Winds are generated due to _____________heating on the earth.
(c) Near the earth's surface ____________ air rises up whereas
_________air comes down.
(d) Air moves from a region of ____________ pressure to a region of
__________pressure.
2. Suggest two methods to find out wind direction at a given place.
3. State two experiences that made you think that air exerts pressure (other than
those given in the text).
4. You want to buy a house. Would you like to buy a house having windows but no
ventilators? Explain your answer.
5. Explain why holes are made in hanging banners and hoarding ?
6. How will you help your neighbors in case a cyclone approaches your village/town?
7. What planning is required in advance to deal with the situation created by a
cyclone?
8. Which one of the following place is unlikely to be affected by a cyclone.
(i) Chennai (ii) Mangaluru (Mangalore)
(iii) Amritsar (iv) Puri
9. Which of the statements given below is correct?
(i) In winter the winds flow from the land to the ocean.
(ii) In summer the winds flow from the land towards the ocean.
(iii) A cyclone is formed by a very high-pressure system with very high speed
winds revolving around it.
(iv) The coastline of India is not vulnerable to cyclones.

Extended Learning - Activities and Projects

1. You can perform the Activity 8.5 given in the chapter slight differently at home. Use
two plastic bottles of the same size. Stretch one balloon on the neck of each bottle.
Keep one bottle in the sun and the other in the shade. Record your observations.
Compare these observations and the result with those of Activity 8.5.
2. You can make your own anemometer.
Collect the following items:

WINDS, STORMS AND CYCLONES 108

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

4 small paper cups (used ice cream cups), 2 strips of cardboard (20cm long and
2cm wide), gum, stapler, a sketch pen and a sharpened pencil with eraser at one
end.
Take a scale; draw crosses on the cardboard strips as shown in the Fig. 8.18. This
will give the centre of the strips.

Fig. 8.18 : Finding centre of the strips

Fig. 8.19 : A model of an anemometer

Fix the strips at the centre, putting one over other so that they make a plus (+) sign.
Now fix the cups at the end of the strips. Colour the outer surface of one cup with a
marker or a sketch pen. All the 4 cups should face same direction.

Push a pin through the centre of the strips and attach the strips and the cups to the
eraser of the pencil. Check that the strips rotate freely when you blow on the cups.
Your anemometer is ready. Counting the number of the rotation per minute will give
you an estimate of the speed, use it at different places and different times of the day.

If you do not have a pencil with attached eraser you can use the tip of the ball pen.

WINDS, STORMS AND CYCLONES 109

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

The only condition is that the strips should rotate freely.

Remember that this anemometer will indicate only speed changes. It will not give
you the actual wind speed.
3. Collect articles and photographs from newspapers and magazines about
storms and cyclones. Make a story on the basis of what you have learnt in this
chapter and the matter collected by you.
4. Suppose you are a member of a committee, which is responsible for creating
development plan of a coastal state. Prepare a short speech indicating the
measures to be taken to reduce the suffering of the people caused by cyclones.
5. Interview eyewitnesses to collect the actual experience of people affected by a
cyclone.
6. Take an aluminum tube about 1 to 1.5cm in
diameter. Cut slice of a medium sized potato about
2cm thick. Insert the tube into the slice, press it, and
rotate it 2-3 time. Remove the tube. You will find a
piece of potato fixed in the tube like a piston head.
Repeat the same process with the other end of the
tube. Now you have the tube with both ends closed
with potato pieces with an air column in between.
Take a pencil with one end unsharpened. Place
this end at one of the pieces of potato. Press it
suddenly to push the potato piece in the tube. Observe what happens. The activity
shows rather dramatically how increased air pressure can push things.
CAUTION: When you perform this activity no body should be
standing in front of the tube .

You can read more on the related topics on the following websites:
http: // www. imd. gov. in/
http: // library. thinkquest. org / 10136 /
www. bom. gov.au / students_ teachers / shtml
www. chunder. com / ski/ lightanim. html

WINDS, STORMS AND CYCLONES 110

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW ?

A bolt of lightning travels at a speed of more than 400,000 km/hr. It can heat the air
around it to a temperature which is more than 4 times the temperature of the
surface of the sun. That is what makes lightning so dangerous.

WINDS, STORMS AND CYCLONES 111

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

9 SOIL

A
ll living organisms depend The earthy fragrance of soil after the first
directly or indirectly on soil. rain is always refreshing.
Plants prepare food for whole The scientific study of the
characteristics, development and
biots but the plants derive all vital
distribution of soils is called pedology
nutrients from soil to grow and thrive. and the process of soil formation is
Soil is one of the most important known as pedogenesis.
natural resources. It supports the growth
9.1 SOIL TEEMING WITH LIFE
of plants by holding the roots firmly and
One day during the rainy season
supplying water and nutrients. It is the
Saba and Yasir observed an earthworm
home for many organisms. Soil is
coming out of the soil. Saba wondered
essential for agriculture. Agriculture
whether there were other organisms also
provides food, clothing and shelter for all.
in the soil. Let us find out.
Soil is thus an inseparable part of our life.
Activity 9.1
Collect some soil sample and observe
them carefully. You can use a hand lens.
Examine each sample carefully and fill in
Table 9.1.
? Discuss your observations with
your friends.
Fig.9.1 : Children playing with soil ? Are the soil samples collected by
Table 9.1
S.No Soil Source Plants Animals Any other observation
1. Garden soil Grass,… Ant,…….
2. Soil from the roadside …… …….
3. Soil from the area where
construction is going on ……. ……...
4. ..........
5. ..........

SOIL 112
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

your friends similar to the ones Activity 9.2

collected by you? Take a little soil. Break the clumps with
Yasir and Saba have used soil in your hand to powder it. Now take a glass
many ways. They enjoy playing with it. It is tumbler, three quarters be filled with
a great fun indeed. water, and then add a handful of soil to it.
Make a list of the uses of soil. Stir it well with a stick to dissolve the soil.
Now let it stand undisturbed for some time
(Fig.9.2). Afterwards, observe it and
I wonder why I found some
pieces of plastic articles and answer the following questions:
polythene bags in the soil sample ? Do you see layers of particles of
collected from the roadside and
the garden. different sizes in the glass tumbler?
? Draw a diagram showing these
layers.
Polythene bags and plastics pollute the ? Are there some dead rotting leaves or
soil. They also kill the organisms living in
the soil. That is way there is a demand to animal remain floating on water?
ban the polythene bags and plastics. The rotting dead matter in the soil is called
Other substances which pollute the soil humus. You probably know that the soil is
are a number of waste products,
formed by the breaking down of rocks by
chemicals and pesticides. Waste
products and chemicals should be the action of wind, water and climate. This
treated before they are released into the process is called weathering. The nature
soil. The use of pesticides should be
minimized. of any soil depends upon the rocks from
which it has been formed and the type of
vegetation that grows in it.

I want to know whether the

soil from a field can be used humus
to make toys.
water

clay
9.2 SOIL PROFILE
Soil is composed of distinct layers. sand

Perform the following activity to find out

gravel
how these layers are arranged.
Fig.9.2 : Layers of soil

SOIL 113
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

A vertical section through different see the inner layers of the soil, too. Such a
layers of the soil is called the soil profile. view enables us to observe the soil profile
Each layer differs in feel (texture), color, at that place. Soil profile can also be seen
depth and chemical composition. These while digging a well or laying the
layers are referred to as horizons foundation of a building. It can also be
(Fig.9.3). seen at the sides of a road on a hill or at a
The soil profile revels the surface steep river bank.
and the sub-surface qualities of the soil The uppermost horizon is generally
which directly affect plant growth. dark in color as it is rich in humus and
minerals. The humus makes the soil
We usually see the top surface of
fertile and provides nutrients to growing
the soil, not the layers below it. If we look
plants. This layer is generally soft, porous
at the sides of a recently dug ditch, we can
and can retain more water. It is called the

A-horizon

B-horizon

C-horizon

Bedrock

Fig.9.3 : Soil profile

SOIL 114
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

topsoil or the A-horizon. proportion of fine particles is relatively

This provides shelter for many living higher, then it is called clayey soil. If the
organisms such as worms, rodents, amount of large and fine particles is about
moles and beetles. The roots of small the same, then the soil is called loamy.
plants are embedded entirely in the Thus, the soil can be classified as sandy,
topsoil. clayey and loamy.
The next layer has a lesser amount of
Soil types in Jammu and Kashmir:
humus but more of minerals. This layer is 1. Gurti or Clay Soil
generally harder and more compact and 2. Sekil or Sandy Soil
is called the B-horizon or the middle 3. Bahil or Loam Soil
layer. 4. Nambal or Peats Soil
The third layer is the C-horizon, which 5. Surzamin
6. Karewa
is made up of small lumps of rocks with
cracks and crevices. Below this layer is The size of the particles in a soil have
the bedrock, which is hard and difficult to a very important influence on its
dig with a spade. properties. Sand particles are quite large.
They cannot fit closely together, so there
9.3 SOIL TYPES are large spaces between them.
As you know, weathering of rocks
produces small particles of various About 35% of the volume of a typical
materials. These include sand and clay. soil consists of air filled pores.
The relative amount of sand and clay
depends upon the rock from which the These spaces are filled with air. We
particles were formed, that is the parent say that the sand is well aerated. Water
rock. The mixture of rock particles and can drain quickly through the spaces
humus is called the soil. Living between the sand particles. So, sandy
organisms, such as bacteria, plant roots soils tend to be light, well aerated and
and earthworm are also important parts of rather dry. Clay particles, being much
any soil. smaller, pack tightly together, leaving little
The soil is classified on the basis of space for air. Unlike sandy soil, water can
proportion of particles of various sizes. If be held in the tiny gaps between the
soil contains greater proportion of big particles of clay. So clay soils have little
particles, it is called sandy soil. If the air. But they are heavy as they hold more

SOIL 115
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

water than the sandy soils. cylinder (Fig.9.4 (d)). Try to make a ring
from this cylinder (Fig.9.4(e)). Repeat this
The air trapped in the pores present in
activity with other samples also. Does the
the soil has been found to contain
extent to which a soil can be shaped
excess of carbon dioxide, but a
indicate its type?
deficiency of oxygen and nitrogen.
Can you suggest which type of soil

The best topsoil for growing plants is would be the best for making pots, toys

loam. Loamy soil is a mixture of sand, and statues?

clay and another type of soil particle

known as silt. Silt occurs as a deposit in
river beds. The size of the silt particles is
between those of sand and clay. The
(a) (b)
loamy soil also has humus in it. It has the
right water holding capacity for the growth
(d)
of plants.

I want to know:
what kind of soil should be
used for making matkas and
surahis. (c) (e)
Fig.9.4 : Working with the soil
Activity 9.3
9.4 PROPERTIES OF SOIL
Collect samples of clayey, loamy and
You have listed some uses of soil. Let
sandy soils. Take a fistful of soil from one
us perform some activities to find the
of the samples. Remove any pebbles,
characteristics of the soil.
rocks or grass blades from it. Now add
Percolation rate of water in soil
water drop by drop and knead the soil (Fig
Yasir and Saba marked two different
9.4(a)). Add just enough water so that a
squares of 50 cm x 50 cm each, one on
ball (Fig 9.4 (b)) can be made from it, but
the floor of their house and the other on
at the same time it should not be sticky.
the Kutcha (unpaved) road. They filled
Try to make a ball (Fig.9.4 (c)) from the
two bottles, of the same size with water.
soil. On a flat surface, roll this ball into the
They emptied the water from the bottles,

SOIL 116
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

one each, at the same time in the two

squares. They observed that the water
on the floor flowed down and was not
absorbed. On the Kutcha road, on the
other hand, the water was absorbed.

Yasir wondered why there

was a difference
. in the Fig.9.5 : Measuring rate of percolation
absorption of water in the
two squares. the pipe empty, note the time again.
Be careful not to let the water spill over or

Now let us perform an activity to run down on the outside of the pipe while

understand this. pouring. Calculate the rate of percolation

Activity 9.4 by using the following formula:

amount of water (mL.)
percolation rate (mL./min) =
For this activity divide yourself into percolation time (min)

three teams A, B and C. You will be finding For example, suppose that for a
out how fast the water passes down the certain sample, it took 20 minutes for 200
soil. You will need a hollow cylinder or a mL to percolate. So,
200 mL
rate of percolation = = 10mL/min
pipe. Ensure that each team uses pipes of 20min

the same diameter. Some suggestions for Calculate the rate of percolation in
obtaining such a pipe are given below: your soil sample. Compare your findings
1. If possible, get a small tin can and cut with other and arrange the soil samples in
off its bottom. the increasing order of the rate of
2. If PVC pipe (approx. diameter 5 cm) is percolation.
available, cut it into 20 cm long pieces 9.5 MOISTURE IN SOIL
and use them. Have you ever passed through a
At the place where you collect the soil, farmland during a hot summer day?
place the pipe about 2 cm deep in the Perhaps you noticed that the air above
ground. Pour 200 mL water in the pipe the land is shimmering. Why is it so? Try
slowly. For measuring 200 mL water you out this activity and find the answer.
can use any empty 200 mL bottle. Note Activity 9.5
the time when you start pouring water. Take a boiling tube. Put two spoonful
When all the water has percolated leaving of a soil sample in it. Heat it on a flame

SOIL 117
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(Fig.9.6) and observe it. Let us find out Activity 9.6

what happens upon heating. Take a plastic funnel. Take a filter
Do you see water drops any where? If paper (or a piece of newspaper sheet),
yes, where did you find them? fold and place it as shown in the figure.
On heating, water in the soil Weigh 50 gm of dry, powdered soil and
evaporates, moves up and condenses on pour it into the funnel. Measure a certain
the cooler inner walls of the upper part of amount of water in a measuring cylinder
the boiling tube. and pour it drop by drop on the soil. You
On a hot summer day, the vapour
can use a dropper for this purpose. Do not
coming out of the soil reflects the sunlight
let all the water fall at one spot.
and the air above the soil seems to
shimmer.
Dropper
Filter paper
Drops

Funnel

Boiling tube

Stand Soil sample

Beaker

Burner

Fig.9.7 : Absorption of water in the soil

Fig.9.6 : Removing moisture from the soil
Pour water all over the soil. Keep pouring
After heating the soil, take it out of the water till it starts dripping. Subtract the
tube. Compare it with the soil which has amount of water left in the measuring
not been heated. Note the difference cylinder from the amount you started with.
between the two. This is the amount of water retained by
9.6 ABSORPTION OF WATER the soil. Record your results in your
BY SOIL notebook in the following manner:
Do all the soils absorb water to the Weight of soil = 50 g
same extent? Let us find out. Initial volume of water in the

SOIL 118
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

measuring cylinder = U mL different parts of India. In some parts

Final volume of water in the there is clayey soil, in some parts there is
measuring cylinder = V mL loamy soil while in some other parts there
Volume of water absorbed by the soil is sandy soil.
= (U-V) mL In the regions of J&K, the soils
Weight of water absorbed by the soil =
are loamy and there is little clay content
(U-V) g
in them, poor in lime and phosphorus
(1 mL of water has weight equal to 1g)
content but with a high content of
Percentage of water absorbed
= (U-V) x 100 magnesia.
50 Soil is affected by wind, rainfall,
Repeat this activity with different soil temperature, light and humidity. These
samples. Would you get same results for are some climatic factors which affect the
all the samples? Discuss the results with soil profile and bring changes in the soil
your friends and answer the following structure. The climatic factors, as well as
questions: the components of soil, determine the
? Which soil would have the highest various types of vegetation and crops that
percolation rate? might grow in any region.
? Which soil would have the lowest
percolation rate? A typical productive soil consists of
? Yasir heard from his neighbourer that approximately 5% organic matter and
95% inorganic matter.
8-10 days after the rain, the level of
water in a pond or well rises. Which Clayey and loamy soils are both suitable
type of soil will allow water to reach a for growing cereals like wheat and gram.
well faster and in greater amount? Such soils are good at retaining water. For
? Which type of soil retains the highest paddy, soils rich in clay, organic matter
amount of water and which retains the and having a good capacity to retain
least? water are ideal. For lentils (masoor) and
? Can you suggest any method to let other pulses, loamy soils, which drain
more rain water percolate and reach water easily, are required. For cotton,
the water underground? sandy-loam or loam, which drain water
9.7 SOIL AND CROPS easily and can hold plenty of air, are more
Different types of soils are found in suitable.

SOIL 119
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

A CASE STUDY

John, Rashida and Radha went to Leeladhar Dada and Santosh Malviya of Sohagpur
in Madhya Pradesh. Leeladhar Dada was preparing the soil to make items like Surahi,
Matki, Kalla (earthen frying pan) etc. The following is the conversation they all had with
Leeladhar Dada :

- Where was the soil obtained from ?

Dada: We brought the black soil from a piece of barren land.
- How is the soil prepared ?
Dada: Dry soil will be placed in a large tank and would be cleared of pebbles etc. After
removing these things the soil will be soaked for around 8 hours. This soil would
be kneaded after mixing horse dung. The kneaded soil would be placed on the
wheel and given appropriate shape. The final shape is given with hands. The
items are coloured after three days of drying. All the items are baked at high
temperature after drying in the air.
- Why is the horse dung mixed on soil ?
Dada: Burnt horse dung helps open up the pores in the soil. So that water could
percolate out of the Matkas and Surahis which evaporates and cools the water
inside. You know Sohagpuri surahis and matkas are famous in far off places like
Jabalpur, Nagpur, Allahabad etc.

Fig.9.8 : Making pots

Major Crops grown in J&K State

S.No Area Crops grown
1. Jammu and Kathua districts Rice, Wheat, Sugarcane
2. Kandi belt (Jammu, Kathua, Maize, Wheat, Jawar and Bajra
Udhampur and Rajouri districts)
3. Kashmir Rice, Wheat, Maize, Pulses, Oilseeds
4. Ladakh Wheat Barley

SOIL 120
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Crops such as wheat are grown in the fine

clayey soils, because they are rich in
humus and are very fertile. Find from your
teachers, parents and farmers the type of What is the difference
between rate of percolation and
soil and crops grown in your area. Enter
the amount of water retained?
the data in the following Table 9.2. Yasir, You seem to have
Which kind of soil would be most forgotten what you read
earlier. Go and reread the
suitable for planting rice? Soil with a
lesson again and you will find
higher or lower rate of percolation? the answer.

Table 9.2
S.No. Type of soil Crop grown Soil Erosion in J&K
1. Clayey Wheat….... Erosion results from energy transmitted
2.
from rainfall and wind. In Jammu and
3.
Kashmir, the soils of Kandi belt have

severely suffered from erosion. About 26

Soil Erosion
percent of the total area which is under
The removal of land surface by water,
village forests is now quite eroded.
wind or ice is known as erosion. Plant
roots firmly bind the soil. In the absence Other affected areas in J&K due to
of plants, soil becomes loose. So it can erosion are Kaleeth and Chauki Chora
be moved by wind and flowing water. of Akhnoor tehsil, Dansal, Jhajjar Kotli,
Erosion of soil is more severe in areas of
Ramnagar, Mansar, Surinsar, Jandial
little or no surface vegetation, such as
and Amb series of Bhalwal block of
desert or barren lands. So, cutting of
trees and deforestation should be Jammu, areas between Balaul and
prevented and effort should be made to Basantar.
increase the green areas.

SOIL 121
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Clayey Moisture Humus

Sandy Loamy Water retention
Percolation

What you have Learnt

? Soil is important for life on earth
? Soil profile is a section through different layers of the soil, various layers are called
horizons.
? Soil is of different types: Clayey, loamy and sandy.
? Percolation rate of water is different in different types of soil. It is highest in the sandy soil and
least in the clayey soil.
? Different types of soils are used to cultivate different types of crops. Clay and loam are suitable
for growing wheat, gram and paddy. Cotton is grown in sandy loam soil.
? Soil holds water in it, which is called soil moisture. The capacity of a soil to hold water is
important for various crops.
? Clayey soil is used to make pots, toys and statues.

EXERCISES
Tick the most suitable answer in questions 1 and 2.
1. In addition to the rocks particles, the soil contains
(i) Air and water
(ii) Water and plants
(iii) Minerals, organic matter, air and water
(iv) Water, air and plants
2. The water holding capacity is highest in
(i) Sandy soil (ii) Clayey soil
(iii) Loamy soil (iv) Mixture of sand and loam
3. The process of soil formation is called
(i) Conservation (ii) Weathering
(iii) Erosion (iv) Pedogenesis
4. Soil profile consist of
(i) Two layers (ii) Three layers
(iii) Four layers (iv) Five layers

SOIL 122
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

5. Humus is present in
(i) A-Horizon (ii) B-horizon
(iii) C-Horizon (iv) Bed rock

6. Match the items in Column I with those in Column II:

Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight
(v) Clayey soil (e) Lesser amount of humus

7. Explain how soil is formed.

8. How is clayey soil useful for crops?
9. List the differences between clayey soil and sandy soil.
10. Sketch the cross section of soil and label the various layers.
11. Razia conducted an experiment in the field related to the rate of percolation.
She observed that it took 40 min for 200 mL of water to percolate through the soil
sample. Calculate the rate of percolation.
12. Explain how soil pollution and soil erosion could be prevented.
13. Solve the following crossword puzzle with the clues given:
1

4 5

SOIL 123
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organisms in the soil.
Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.

Extended Learning - Activities and Projects

1. Yasir would like to know the difference between raw and baked soil? Investigate
how the soil from which matkas are made is different from the soil used to make
statues.
2. Saba is worried. She could see a brick kiln from her house. Bricks were being made
there. There was so much smoke coming out of the kiln. She was told that the best
quality of clay is required for making pottery, statues and bricks. She has seen
truck loads of bricks being taken away for construction of buildings. At this rate, she
fears, no soil will be left. Are her fears justified? Discuss this problem with your
parents, teachers and other experts of your area and prepare a report.
3 Try to find out the moisture content of a soil sample. One method is given here.
Activity: Take 100 g soil. (Take help from any shopkeeper to weigh the soil.) Place
it on a newspaper in the sun and allow it to dry for two hours. This activity is best
done in the afternoon. Take care that the soil does not spill outside the newspaper.
After drying it, weigh the soil again. The difference in the weight of the soil before
and after drying gives you the amount of moisture contained in 100g of soil. This is
called the percentage moisture content.
Suppose your sample of soil loses 10 g on drying. Then
wt. of moisture (g) x 100
Percent of moisture in soil =
Original wt. of soil sample (g)
In this example
10 x 100
Percent of moisture in soil = = 10%
100

SOIL 124
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW?

Rivers of North India, which flow from Himalayas, bring a variety of materials
including silt, clay, sand and gravel. They deposit their materials called alluvial
soil, in the planes of north India. This soil is very fertile and supports nearby half
the population of India.

SOIL 125
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

10 RESPIRATION IN ORGANISMS

O
ne day Yasir was eagerly from? Can you say why your parents
waiting to meet his insist that you should eat regularly? The
grandparents who were food has stored energy, which is released
coming to the town after a year. He was in during respiration. Therefore all living
a real hurry as he wanted to receive them organisms respire to get energy from
at the bus stop. He ran fast and reached food. During breathing, we breathe in air.
the bus stop in a few minutes. He was You know that air contains oxygen. We
breathing rapidly. His grandmother asked breathe out air which is rich in carbon
him why he was breathing so fast. Yasir dioxide. The air we breathe in is
told her that he came running all the way. transported to all part of the body and
But the question got struck in his mind. He ultimately to each cell. Inhaled oxygen
wondered why running makes a person from the air helps in the breakdown of
breathe faster. The answer to Yasir food. The process of breakdown of food in
question lies in understanding why do we the cell with the release of energy is called
breathe. Breathing is a part of respiration. cellular respiration. Cellular respiration
Let us learn about respiration. takes place in the cells of all organisms.
In the cell, the food (glucose) is broken
10.1 WHY DO WE RESPIRE? down into carbon dioxide and water using
You know that all organisms are oxygen. When breakdown of glucose
made of small microscopic units called occurs with the use of oxygen it is called
cells. A cell is the smallest structural and aerobic respiration. Food can also be
functional unit of an organism. Each cell broken down, without using oxygen. This
of an organism performs certain function is called anaerobic respiration.
such as nutrition, transport, excretion and Breakdown of food releases energy.
reproduction. To perform these functions, C6H12O6 + 6O2 " 6CO2 + 6H2O +
the cell needs energy. Even when we are
Energy
eating, sleeping or reading we require Glucose with use of oxygen release
energy. But, where does this energy come carbon dioxide, water and energy.

RESPIRATION IN ORGANISMS 126

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Glucose with the use of oxygen breakdown of glucose produces lactic

carbon dioxide + water + energy acid which causes muscle cramps. We
You should know that there are get relief from cramps after a hot water
some organisms such as yeast that can bath or a massage. Can you guess why it
survive in the absence of air. They are is so? Hot water bath or massage
called anaerobes. They get energy improves circulation of blood. As a result,
through anaerobic respiration. In the the supply of oxygen to the muscle cells
absence of oxygen, glucose breaks down increases. The increase in the supply of
into alcohol and carbon dioxide, as given oxygen re sults in the comp lete
below: breakdown of lactic acid into carbon
Glucose without the use of oxygen
dioxide and water.
alcohol + carbondioxide + energy

Yeasts are single- celled organisms.

They respire anaerobically and during
this process yield alcohol. They are,
therefore, used to make wine and beer.

Our muscle cells can also respire

anaerobically, but only for a short time,
when there is a temporary deficiency of
oxygen. During heavy exercise, fast
running (Fig.10.1), cycling, walking for
many hours or heavy weight lifting, the
demand for energy is high, but the supply
Fig.10.1 : During exercise, some muscles may
of oxygen is very less in the muscle cells respire anaerobically
to fulfill the demand of energy:
In the absence of oxygen
Glucose
(In Muscle) 10.2 BREATHING
Lactic acid + Energy
Activity 10.1
Have you ever wondered why you
CAUTION
get muscle cramps after heavy exercise?
Do this activity under the supervision
The cramps occur when muscle cells
of your teacher .
respire anaerobically. The partial
Close your nostrils and mouth

RESPIRATION IN ORGANISMS 127

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

tightly and look at a watch. What did you according to the requirement of oxygen
feel after some time? How long were you by the body? Let us find out by doing the
able to keep both of them closed? Note following activity.
down the time period for which you could
hold your breath (Fig. 10.2).
So, now you know that you cannot
survive for long without breathing.
Breathing means taking in air rich
in oxygen and giving out air rich in carbon
dioxide with the help of respiratory
organs. The talking in of air rich in oxygen
into the body is called inhalation and
giving out of air rich in carbon dioxide is Fig.10.2 : Holding breath
known as exhalation. It is a continuous
process which goes on all the time and Yasir noticed that when he
throughout the life of an organism. released his breath after holding
The number of times a person it for some time, he had to
breathe heavily. Can you tell
breathes in a minute is termed as the him why it was so?
breathing rate. During breathing
inhalation and exhalation takes place
alternately. A breath means one inhalation Activity 10.2
plus one exhalation. Would you like to find Generally we are not aware that we

out your breathing rate? Do you want to are breathing. However, if you try you can

know whether it is constant or it changes count your rate of breathing. Breathe in

Table 10.1: Changes in breathing rate under different conditions
Name of the classmate Breathing rate
Normal After a brisk walk After running At rest
for 10 minutes fast for 100 m

Self

RESPIRATION IN ORGANISMS 128

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

and out normally. Find out how many Activity 10.3

times you breathe in and breathe out in a Figure 10.3 shows the various
minute? Did you inhale the same number activities carried out by a person during a
of times as you exhale? Now count your normal day. Can you say in which activity,
breathing rate (number of breaths/ the rate of breathing will be the slowest
minute) after brisk walk and after running. and in which it will be the faster? Assign
Record your breathing rate as soon as number to the picture in the order of
you finish and also after complete rest. increasing rate of breathing according to
Tabulate your findings and compare your your experience.
breathing rates under different conditions
with those of your classmates.
.
From the above activity, you must
have realized that whenever a person
needs extra energy, he/ she breathes
faster. As a result more oxygen is supplied
to our cells. It speeds up the breakdown of
food and more energy is released. Does
this explain why we feel hungry after a
physical activity?
When you feel drowsy, does your
breathing rate slow down? Does your
Fig.10.3 : Variation in the breathing during
body receive sufficient oxygen? different activities

On an average, an adult human being Saba wants to know why

at rest breathes in and out 15 -18 times we yawn when we are

sleepy or drowsy.
in a minute. During heavy exercise, the
breathing rate can increase upto 25
times per minute. While we exercise, 10.3 HOW DO WE BREATHE?
not only do we breathe fast, we also Let us now learn about the
take deep breaths and thus inhale more mechanism of breathing. Normally we
oxygen . take in air through our nostrils. When we

RESPIRATION IN ORGANISMS 129

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

inhale air, it passes through our nostrils During inhalation, ribs move up
into the nasal cavity. From the nasal and outwards and diaphragm moves
cavity, the air reaches our lungs through down. This movement increases space in
the windpipe. Lungs are present in the our chest cavity and air rushes into the
chest cavity (Fig. 10. 4). This cavity is lungs. The lungs get filled with air. During
surrounded by ribs on the sides. A large exhalation, ribs move down and inwards,
muscular sheet called diaphragm forms while diaphragm moves up to its former
the floor of the chest cavity (Fig. 10. 4). position. This reduces the size of the
Breathing involves the movement of the chest cavity and air is pushed out of the
diaphragm and the rib cage. lungs (Fig. 10.5). These movement in our

Nasal passage
Pharynx

Oral cavity

Trachea

Lungs

Diaphragm
Ribs

Fig 10.4 : Human respiratory system

The air around us has various types of unwanted particles, such as smoke, dust, pollen,
etc. When we inhale, the particles get trapped in the hair present in our nasal cavity.
However, sometimes these particles may bypass the hair in the nasal cavity. Then they
irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these
foreign particles from the inhaled air and a dust- free, clean air enters our body.
TAKE CARE: When you sneeze, you should cover your nose so that the foreign particles
you expel are not inhaled by other persons.

RESPIRATION IN ORGANISMS 130

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

body can be felt easily. Take a deep Activity 10.4

breath. Keep your palm on the abdomen. Take a deep breath. Measure the
What do you find? size of the chest with a measuring tape
After having learnt that during (Fig. 10.6) and record your observations
breathing there are changes in the size of in Table 10.2. Measure the size of the
chest cavity, children got involved in the chest when expanded and indicate which
chest expansion competition. Everyone classmate shows the maximum
was boasting that she/ he could expand it expansion of the chest.
the maximum. How about doing this We can understand the
activity in the class with your classmate? mechanism of breathing by a simple
model.
Smoking damages our lungs. Smoking
Activity 10.5
is also linked to cancer. It must be
Take a wide plastic bottle. Remove
avoided.
the bottom of the bottle. Get a Y- shaped

Diaphragm Diaphragm
moves down moves back
(b) Exhalation
(a) Inhalation
Fig.10.5 : Mechanism of breathing in human beings
Table 10.2 Effect of breathing on the chest size of some classmates
Name of the Size of the chest
Classmates During inhalation During exhalation Difference in size

RESPIRATION IN ORGANISMS 131

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

glass or plastic tube. Make a hole in the lid 10.4 WHAT DO WE BREATHE OUT?
so that the tube may pass through it. To Activity 10.6
the forked end of the tube fix two deflated Take a slender, clean test tube or a
balloons. Introduce the tube into the bottle glass/ plastic bottle. Make a hole in its lid
as shown in Fig. 10.7. Now cap the bottle. and fix it on the bottle. Pour some freshly
Seal it to make airtight. To the open base prepared lime water in the test- tube.
of the bottle tie a thin rubber or plastic Insert a plastic straw through the hole in
sheet using a large rubber band. the lid in such a way that it dips in lime
water. Now blow gently through the straw
a few times (Fig. 10.8). Is there a change
in the appearance of lime water? Can you
explain this change on the basis of what
you have learnt earlier ?
You are aware that the air we
inhale or exhale is a mixture of gases.
What do we exhale? Do we exhale only
carbon dioxide or a mixture of gases
along with it? You must have also
observed that if you exhale on a mirror, a
film of moisture appears on its surface.
Fig.10.6 : Measuring chest size From where do these droplets come?

To understand the expansion of

the lungs, pull the rubber sheet from the
base downwards and watch the balloons. Plastic
Next, push the rubber/ plastic sheet up bottle

and observe the balloons. Did you see

Balloons
any changes in the balloons?
What do the balloons in this model
Rubber
represent? What does the rubber sheet sheet
represent?
Now you should be able to explain
Fig 10.7 : Model to show the mechanism of
the mechanism of breathing. breathing

RESPIRATION IN ORGANISMS 132

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

How do other organisms breathe?

Do they also have lungs like those of
human beings? Let us find out.

Yasir wants to know if

Straw cockroaches, snails, fish,
earthworms, ants and mosquitoes
also have lungs.

Lime water
Fig 10.8 : Effect of exhaled air on lime water Cockroach: A cockroach has small
openings on the sides of its body. Other
Yasir wants to know how insects also have similar openings. These
much air a person can hold in openings are called spiracles (Fig. 10.9).
the lungs.
Insects have a network of air tubes called
tracheae for gas exchange. Oxygen rich
The percentage of oxygen and carbon air rushes through spiracles into the
dioxide in inhaled and exhaled air. tracheal tubes, diffuses into the body
Inhaled air Exhaled air
tissue and reaches every cell of the body.
21% oxygen 16.4% oxygen
Similarly, carbon dioxide from the cells
goes into the tracheal tubes and moves
Lungs out through spiracles. These air tubes or
tracheae are found only in insects and not
0.04% Carbon 4.4% Carbon in any other group of animals.
dioxide dioxide
Tracheae
10.5 BREATHING IN OTHER
ANIMALS
Animals such as elephants, lions,
cows, goats, frogs, lizards, snakes and
birds have lungs in their chest cavities like
Fig.10.9 : Tracheal system
the human beings.

RESPIRATION IN ORGANISMS 133

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Earthworm: You have already learnt that You have studied in previous class
earthworms breathe through their skin. that gills in fish help them to use oxygen
The skin of an earthworm feels moist and dissolved in water. Gills are projections of
slimy on touching. Gases can easily pass the skin. You may wonder how gills help in
through them. Though frogs have a pair of breathing. Gills are well supplied with
lungs like human beings, they can also blood vessels (Fig.10.10) for exchange of
breathe through their skin, which is moist gases.
and slippery.
10.7 DO PLANTS ALSO RESPIRE?
Like other organisms, plants also
Yasir has seen in television
programmes that whales and respire for their survival as you have
dolphins often come up to the already learnt. They also take in oxygen
water surface. They even release from the air and give out carbon dioxide.
a fountain of water sometimes
In the cells oxygen is used to breakdown
while moving upwards. Why do
they do so? glucose into carbon dioxide and water as
in other organisms. In plants each part
can independently take in oxygen from
10.6 BREATHING UNDER WATER the air and give out carbon dioxide. You
Can we breathe and survive in have already learnt in chapter 1 that the
water? There are many organisms which leaves of the plants have tiny pores called
live in water. How do they breathe under stomata for exchange of oxygen and
water? carbon dioxide.

Gills
Saba wants to know whether
roots, which are underground
also, take in oxygen. If so, how?

Like all other living cells of the

plants, the root cells also need oxygen to
Fig.10.10 : Breathing organs in fish generate energy. Roots take up air from
the air spaces present between the soils

RESPIRATION IN ORGANISMS 134

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

particles (Fig. 10. 11). Can you guess what would

happen if a potted plant is over watered?
In this chapter you learnt
Soil particles that respiration is a vital biological
process. All living organisms need to
respire to get the energy needed for the
survival.
Root hair

Air space

Fig.10.11 : Roots absorb air from the soil

Aerobic respiration Diaphragm Inhalation

Anaerobic respiration Exhalation Spiracles
Breathing rate Gills Tracheae
Cellular respiration Lungs Ribs

What you have learnt

? Respiration is essential for survival of living organisms. It releases energy from the
food.
? The oxygen we inhale is used to breakdown glucose into carbon dioxide and water.
Energy is released in the process.
? The breakdown of glucose occurs in the cells of an organism (cellular respiration).
? If the food is broken down with the use of oxygen, it is called aerobic respiration. If
the breakdown occurs without the use of oxygen, the respiration is called
anaerobic respiration.
? During the heavy exercise when the supply of oxygen to our muscle cells is
insufficient, food breakdown is by anaerobic respiration.
? Breathing is a part of the process of respiration during which an organisms takes in

RESPIRATION IN ORGANISMS 135

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the oxygen rich air and gives out air rich in carbon dioxide. The respiratory organs
for the exchange of gases vary in different organisms.
? During inhalation, our lungs expand and then come back to the original state as the
air moves out during exhalation.
? Increased physical activity enhances the rate of breathing.
? In animals like cow, buffalo, dog and cat the respiratory organs and the process of
breathing are similar to those in humans.
? In earthworms, the exchange of gases occurs through the moist skin. In fishes it
takes place through gills and in insects through the tracheae.
? In a plant the roots take in air present in the soil. Leaves have tiny pores called
stomata through which they exchange gases. The breakdown of glucose in the
plant cells is similar to that in other living beings.

EXERCISES
1. Define cellular respiration.
2. Why does an athlete breathe faster and deeper than usual after finishing the race?
3. List the similarities and differences between aerobic and anaerobic respiration.
4. Why do we often sneeze when we inhale a lot of dust-laden air?
5. Take three test tubes. Fill ¾th of each with water. Label them A, B and C. Keep a
snail in test-tube A, a water plant in test- tube B and in C, keep snail and plant both.
Which test-tube would have the highest concentration of CO2?

6. Tick mark ( ) the correct answer:

(a) In cockroaches, air enters the body through
(i) lungs (ii) gills
(iii) spiracles (iv) skin
(b) During heavy exercise, we get cramps in the legs due to the accumulation of
(i) carbon dioxide (ii) lactic acid
(iii) Alcohol (iv) water
(c) Normal range of breathing rate per minute in an average adult person at rest is

RESPIRATION IN ORGANISMS 136

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(i) 9-12 (ii) 15-18

(iii) 21-24 (iv) 30-33

(d) During exhalation, the ribs

(i) move outwards (ii) move downwards
(iii) move upwards (iv) do not move at all

7. Match the items in column I with those in column II:

Column I Column II
(a) Yeast (i) Earthworm
(b) Diaphragm (ii) Gills
(c) Skin (iii) Alcohol
(d) Leaves (iv) Chest Cavity
(e) Fish (v) Stomata
(f) Frog (vi) Lungs and skin
(g) Cockroach (vii) Tracheae

8. Mark 'T' if the statement is true and 'F' if it is false:

(i) During heavy exercise the breathing rate of a person slows down. (T/F)
(ii) Plants carry out photosynthesis only during the day and respiration only at
night. (T/F)
(iii) Frogs breathe through their skin as well as their lungs. (T/F)
(iv) The fishes have lungs for respiration. (T/F)
(v) The size of the chest cavity increases during inhalation. (T/F)

9. Given below is a square of letters in which are hidden different words related to
respiration in organisms. These words may be present in any direction upwards,
downwards, or along the diagonals. Find the words for your respiratory system.
Clues about those words are given below the square.

RESPIRATION IN ORGANISMS 137

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

S V M P L U N G S

C Z G Q W X N T L

R M A T I D O T C

I Y R X Y M S R A

B R H I A N T A Y

S T P T B Z R C E

M I A M T S I H A

S P I R A C L E S

N E D K J N S A T

(i) The air tubes of insects

(ii) Skeletal structure surrounding chest cavity
(iii) Muscular floor of the chest cavity
(iv) Tiny pores on the surface of the leaf
(v) Small openings on the sides of the body of an insect
(vi) The respiratory organs of human beings
(vii) The openings through which we inhale
(viii) An anaerobic organism
(ix) An organism with tracheal system

10. The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the
ground.
(c) The temperature of air is higher than on the ground.
(d) The pressure of air is higher than that on the ground.

RESPIRATION IN ORGANISMS 138

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11. Give two example of each of the following:

(1) Animals that breathe through gills __________________
(2) Animals that breathe through spiracles __________________
(3) Animals that breathe through skin __________________

Extended Learning- Activities and Projects

1. Observe fish in an aquarium. You will find flap like structures on both sides of
their heads. There are flaps which cover the gills. These flaps open and
close alternately. On the basis of these observations, explain the process of
respiration in the fish.
2. Visit a local doctor. Learn about the harmful effects of smoking. You can
also collect material on this topic from other sources. You can seek help of
your teacher or parents. Find out the percentage of people who smoke. If
you have a smoker in your family, confront him with the material that you
have collected.
3. Visit a doctor. Find out about artificial respirations.Ask the doctor.
(a) When does a person need artificial respiration?
(b) Does the person need to be kept on artificial respiration temporarily or
permanently?
(c) From where can the person get supply of oxygen for artificial
respiration?
4. Measure the breathing rate of the members of your family and some of your
friends. Investigate.
(a) If the breathing rate of children is different from that of adults.
(b) If the breathing rate of males is different from that of females.
If there is a difference in any of those cases, try to find the reason.

You can read more on the following website:

www.health.howstuffworks.com/adam-200142.htm

RESPIRATION IN ORGANISMS 139

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW?

For us oxygen is essential, but for those organisms which do not use it, oxygen is
toxic. In fact, for humans and other organisms it may be dangerous to breathe
pure oxygen for long.
If we inhale CO (carbon monoxide) produced through incomplete combustion of
coal, respiration gets blocked leading to death of an organism.
At high altitude areas, the pressure of air decreases causing problem in
inhalation. Thus, the people living there are adapted by having more no. of RBC as
compared to those living in low altitude areas.

RESPIRATION IN ORGANISMS 140

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11 TRANSPORTATION IN
PLANTS & ANIMALS

L
iving organisms need food, water 11.2 TRANSPORT IN UNICELLULAR
and oxygen for their survival. In AND S IMPLE MULTI CELLULAR
PLANTS
case of green plants, carbon
Diffusion is a major method by
dioxide, water and sunlight are required.
which transport of material occurs in
These substance need to be carried (or
single celled (unicellular) organisms like
transported) to various parts of the body.
Chlamydomonas and simple multicelluar
In addition, waste materials
plants like Spirogyra.
produced within the body also need to be
When food is being cooked in your
removed. Do you know? There is a
kitchen you can smell it in other rooms in
system called transportation system in
the house.
organisms for this purpose. This is because molecules are
In case of plants, there is a system
leaving the food as a gas and moving
of independent channels, while in
around at a high speed, eventually
animals, transportation is brought about
reaching all parts of the house. This is
by the circulatory system.
called diffusion.
11.1 TRANSPORT OF MATERIALS IN Diffusion is the movement of
PLANTS particles from a high concentration to a
Earlier you have studied that : low concentration until they are spread
(i) Water required for food, manufactured out evenly.
by the plants is absorbed from soil,
11.3 TRANSPORT IN HIGHER
through the root system, and
PLANTS (CONDUCTION)
(ii) The food is synthesized in the leaves.
The mechanism of transport in
The water absorbed from the soil
multicellular higher plants is much more
through the root system has to be moved
elaborate. The process of diffusion, which
upwards to other plant parts, and the food
is slow, cannot meet the requirements of
synthesized in the leaves has to be
transport to all parts in a short period of
carried to other plant parts.
time. How does water reach in our homes.
The methods of transport in
We have pipes for the supply of water in
different plants vary.

TRANSPORTATION IN PLANTS AND ANIMALS 141

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

our homes. In plants also, there are Upward movement of water and
special tubes called xylem and phloem, minerals occurs through pipe-like
which comprise the conducting tissues structures or channels, called xylem
or vascular tissues. It is through these elements, present in root, stem and
tubes that the transport of materials takes leaves of plants. Water is thus carried to
place. Xylem and phloem are present in the entire plant.
all part of the plant body. Plants absorb water and minerals
As mentioned above, there are two by the roots. The roots have root hairs.
aspects of transport of substances in These root hair increase the surface area
plants (Fig. 11.1). of the root for absorbing water and
minerals dissolved in water. The root hair
absorbs water present between the soil
particles and from there it reaches the
xylem elements. (Fig.11.2).

Transport of food

Fig 11.1 : Transport system in plants

(I) Movement of water and minerals
takes place from the roots upwards
to other plant parts. This movement
Fig. 11.2 : Root with root hair
takes place through the stem and its
branches. The prepared food material is
carried in a soluble from through another
(ii) Movement of food materials,
channel, constituted by phloem, from the
synthesized in leaves, to other plant
leaves to all other parts of the body.
parts.
How can we show that these two
transport systems occur in plants?
Transport of water and minerals Let us perform Activities 11.1 and

TRANSPORTATION IN PLANTS AND ANIMALS 142

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11.2 to learn about the transport of plants in a vapour form to their

materials in plants. surroundings by the process of

11.4 TRANSPIRATION transpiration.

The plants absorb much more Transpiration is the process of

water through their root system than what loss of water in a vapour form from the

is required for various life activities like leaves in plants.

It occurs through stomata present
growth and photosynthesis. What
in the leaves by the process of diffusion.
happens to the rest of the water?
Water absorbed through the roots
The excess water is lost by the

ACTIVITY 11.1
To show upward movement of water.
Take a cut shoot (a piece of stem with leaves) of balsam plants and dip it
in a red coloured dye (either eosin or safranine) in a flask as shown in Fig. 11.3.
Leave it for some time.
Then, take sections from different parts of stem. Examine the sections
under the low power of a microscope.
What do you find under the microscope?
You will observe red colour in the stem section.
Now, check weather the entire stem tissue is red or only some parts of
section is red.
You will find that only certain parts of the section are red (Fig. 11. 4 A, B).
Which are these parts?
The red coloured area of the stem represents the vascular tissue (xylem)
in the stem.

Fig. : 11.3 Fig. : 11.4

143
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 11.2
To show transport of food material.
This is easily demonstrated by the
experiment commonly known as 'girdling
experiment'. Girdling of stem removes
phloem tissue (Fig. 11.5).
If a stem is girdled, the downward and
upward movement or food material gets
blocked. So the trunk portion shows
swelling in the area due to accumulation of
food material. Fig. 11.5 : Girdling experiment
To perform this activity, select one branch of a potted pant. Gently remove its
soft part in a small area with the help of a razor blade, as shown in Fig.11.5 A.
Leave the branch after girdling for a week. Observe what happen to the
portion of stem above and below the girdled area.
You will find that the part of stem above the girdle is swollen while the lower
part is unchanged.
What does it indicate?
The food prepared by the leaves could not be carried below the girdled part
of the stem. It therefore, collects above the girdle and the stem there becomes
swollen.
is moved upwards within the plant body. A
Importance of Transpiration
part of it used in the process of
photosynthesis, and some of it is also 1. It results in the transport of water and
used to keep the plant erect and stop it minerals from the soil to the leaves. In
from wilting (drooping). the leaves, water forms the raw
The rest is lost as water vapour
material for photosynthesis.
into the atmosphere from the leaves.The
2. It produces a cooling effect which
evaporation of water from leaves
helps in preventing hot sunlight from
produces a suction pull which helps to
damaging delicate cells.
pull the water upwards to great heights.

TRANSPORTATION IN PLANTS AND ANIMALS 144

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 11.3
To demonstrate transpiration.
You can prove that transpiration takes
place by setting up the apparatus shown in
Fig. 11.6.Mark clearly the level of the water in
each flask. Oil has been added on the surface
of water to prevent its evaporation.
Now leave the apparatus for 24 hours. After
24 hours, note the level of water in the two
Fig. 11.6
flasks.
Note down the level of water in flask (a) and (b) .In which flask the level dropped.
Why has it ? Explain your results.

ACTIVITY 11.4
To demonstrate that water is given off during transpiration.
What do you need ?
(a) Small- sized well watered potted plant
(b) transparent polythene bag
(C) thread
How to do the test? (Fig. 11.7)
1. Take a small sized well watered potted
plant.
2. Cover the plant as shown in figure with a
transparent polythene bag. Tie the bag at the
Fig. 11.7
base of the stem.
3. Leave the plant in sunlight for a few hours, and then observe.
What do you observe? Drops of water on the inside of the bag.
(Water vapour transpired by the plant condenses as water droplets.)

TRANSPORTATION IN PLANTS AND ANIMALS 145

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11.5 CIRCULATORY SYSTEM intestine) from where they are

Circulatory system is a transport excreted out of the body.
system moving substances throughout 3. It p r o t ec t s t h e bo d y a g a i n s t
our body with the help of blood (Fig.11.8). infection by destroying germs.
In an adult human body, there are about 4. It helps in blood clotting, thereby

5.5 litres of blood, forming the most preventing excessive blood loss.
5. It regulates body temperature.
amazing transportation system in the
The blood moves in the body in tubes
body. The blood circulates through the
called blood vessels. The blood vessels
body so that it reaches every cell that
are of three types- arteries, veins and
makes up the body.
capillaries.
The circulatory system (Fig. 11.8)
consists of three part- (i) Heart, (ii) Blood
vessels, (iii) Blood.
11.5.1 The Heart
The adult human heart is about the
size of a clenched fist. It is located in the
chest cavity slightly towards the left (Fig
11.8). This amazing organ is built like a
double-storey house. Each part has two
rooms. On the ground floor are the right

Fig. 11.8 : Circulatory System

The circulatory system or the blood

performs the following functions: Fig. 11.9 : Internal Structure of Heart
1. It carries or transports food and
oxygen to each body cell.
2. It carries away waste products to and left 'ventricles' and the first floor has

organs (like kidneys, lungs and the right and left 'auricles or atria'

TRANSPORTATION IN PLANTS AND ANIMALS 146

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(singular atrium) (Fig 11.9) There are network of capillaries forms the
doors called ‘valves 'between the auricle connection between the arteries and the
and ventricle on each side but none in veins. The pumping station is the heart.
between the two rooms on each floor.
There are also exits from the ventricles DO YOU KNOW ?
The human heart weighs about 225 to
into arteries and entrance from veins into
340 grams and pumps about 16,360
the auricles.
Actually, the heart consists of two litres of blood in 24 hours.

pumps, one on each side. The left side

Arteries lie deep in the tissues,
receives the oxygenated blood (blood rich
except at the wrist, at the temple, and
in oxygen) from the lungs and sends it
along the side of the neck. The pulse can
through the body. The right side receives
be felt at any of these places. Veins lie
it back again with less oxygen and more
closer to the surface of skin and can be
carbon dioxide and sends it to the lungs.
seen as greenish blue lines in our hands
11.5.2 The Blood Vessels and legs.
Imagine two systems of pipes, one
BLOOD
large and one small, both meeting at a
Blood is a red-coloured fluid
central pumping station. This will give you
flowing inside blood vessels. It consists of
an idea of the circulatory system
(i) a liquid part called plasma, and (ii) the
(Fig. 11.9). The smaller system of pipes
cells or corpuscles (Fig.11.10).
goes from the heart to the lungs and back.
The blood cells are of three types :
The larger one goes from the heart to (I) Red blood cells ( RBCs),
various other parts of the body. (ii) White blood cells (WBCs)
The pipes represent the blood and
vessels-arteries, veins and capillaries. (iii) Platelets.
Arteries are blood vessels in The RBCs, as the name suggest,
which blood is going away from the heart are red-coloured due to the presence of a
to all parts of body. In veins, the blood is red-coloured pigment called
coming back to the heart. Arteries are haemoglobin. Haemoglobin is a carrier
carrying (oxgen rich) blood, and the veins of oxygen.
are bringing back impure (carbon dioxide
rich) blood loaded with waste products. A

TRANSPORTATION IN PLANTS AND ANIMALS 147

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

It binds with oxygen and transports it to all

parts of body. It would be difficult to
provide oxygen to all body cells without
haemoglobin.
The WBCs plays an important role
in the body as they destroy the germs and
help in fighting infection.
The platelets help in clotting of
blood, whenever there is a blood flow due
to some injury.

DO YOU KNOW?
The blood of insects, like the
Fig. 11.10 : Types of blood cells cockroach, is colourless.
(not drawn to scale)

Table 11.1: Differences between Arteries and Veins

Arteries Veins

1. Carry blood away from the heart. 1. Bring blood into the heart.
2. Carry oxygenated blood (except 2 Carry deoxygenated blood (except
lung artery) which carries carbon lung vein) which carries
dioxide-rich blood to the oxygen-rich blood from the lungs to
lungs. the heart.
3. Usually deep seated. 3. Lie closer to skin surface.

To see movement of blood through capillaries, perform the following Activity 11.5.

ACTIVITY 11.5
To see movement of blood.
Place a living tadpole in a small drop of water on a slide under microscope.
Examine the thin skin of the tail to see movement of blood through capillaries.

TRANSPORTATION IN PLANTS AND ANIMALS 148

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

oxygen takes place in the lungs. The pure

DO YOU KNOW?
The circulation of blood was blood (oxygenated blood) is carried by the
discovered by an English physician, pulmonary vein to the left auricle. From
William Harvey. here, it enters the left ventricle, and is then
carried by an artery called aorta to all
11.5.3 BLOOD CIRCULATION
parts of the body (Fig.11.11 A).
Blood circulates throughout the
body by the pumping action of the heart.
The deoxygenated blood, (rich in carbon
dioxide) is collected from different organs
of the body through two major veins (vena
cava). The two veins empty blood into the
right auricle from here, it enters the right
ventricle and is pumped into the
pulmonary artery. Through this artery,
blood is carried to the lungs. Exchange FIG. 11.11B : Schematic diagram
of blood circulation
of gases between carbon dioxide and

11.6 HEART BEAT AND PULSE

In a child, the heart beats from 90
to 100 times a minute. In an adult, heart
beat varies from 70-72 times per minute.
Heart beat increases when you do some
Fig. 11.11A : Blood circulation around the body.
The blood always flows in the direction shown.

TRANSPORTATION IN PLANTS AND ANIMALS 149

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

You can perform the following Activity 11.6 and 11.7 to feel the heart beat and the pulse
rate.
ACTIVITY 11.6
To feel the heart beat.
Place your palm on the chest of your friend just below the left nipple. What do you
feel?
You feel that heart is beating with a regular rhythm. Now place your ear at the same
place. What do you hear?
A distinct sound is heard. It is known as the heart beat.
beat. In fact, he is noting the pulse, by measured by using an instrument called
feeling the pressure of movement of Stethoscope (Fig 11.13). A stethoscope
blood through the artery at your wrist. is a device that amplifies the sound of a
The heartbeat can also be heart beat and is used to hear the heart

ACTIVITY 11.7
To Count the Pulse.
Place your two fingers on the wrist of
friend in the line of his thumb (Fig 11.12).
Wait for some time and note down what you
feel.
A throbbing is felt under the fingers.
This indicates that some liquid is flowing
underneath your finger with a jerk. In fact, Fig. 11.12 A Fig. 11.12 B
when a physician holds your wrist, he counts the number of jerks he feels in a
minute.

A stethoscope consists of three parts:-

(i) a chest piece, which is sensitive to
heart beats,
(ii) two earpieces, and
(iv)a tube joining the chest piece and
the ear pieces.
Chest Piece You can make a stethoscope of your
own. How? This is shown in Activity
Fig. 11.13 : Stethoscope 11.8.

TRANSPORTATION IN PLANTS AND ANIMALS 150

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 11.8
Go to your family doctor and request him to show you the stethoscope, the

instrument which he often places on your chest. What does the doctor do with this

instrument?
Now prepare a stethoscope of your
own. You require a glass funnel, a 50cm
long rubber tube and a piece of paper. Fix
these items as shown in the Fig. 11.14. Fig. 11.14
The stethoscope is ready for use. Put the open end of the rubber tubing in one

of your ears. Place the funnel on your chest near the heart. Listen carefully the

thumping sound. The thumping sound is the heart beat. Count the heart beats per

minute. Now run for a short while and again count your heart beats. Do you find any

difference between the two counts? Note down and explain your results.

beats in the chest, by placing the chest 11.7 EXCRETION

piece of the stethoscope at the Living organisms perform a
appropriate place. number of activities. During these
activities, a variety of waste products are

BLOOD PRESSURE
The pumping heart produces a high
pressure in our arteries. We call this the
blood pressure. It rises if we do anything to
make our heart-beat faster, or if the arteries
become narrower.
Constant high blood pressure is
harmful. It puts a strain on the heart and
makes it work harder. It can also cause an
Fig. 11.15 : Measuring Blood Pressure
artery to burst open. If this happens in the brain it can cause a stroke. A stroke can leave
someone partly paralysed and unable to speak. Even worse, it can kill them.

TRANSPORTATION IN PLANTS AND ANIMALS 151

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

produced. For example, some of the food by the simple process of diffusion.
we eat is not used by our bodies. The Specialized organs of excretion are
undigested food is a waste product. lacking (Fig 11.16), which shows outward
During respiration, water, carbon dioxide diffusion of dissolved carbon dioxide and
and heat are produced as wastes. Urea is waste nitrogen compounds all over the
another waste. It comes from used up large surface.
protein. 2. In large animals, diffusion alone is
Some of the waste products like not sufficient. They have developed
urea are very harmful and toxic. These specialized organs for excretion. For
must not be accumulated within the body. example, nephridia are present in
Otherwise, accumulation of waste earthworm and leeches, malpighian
produces health problem. Fortunately, tubules in insects and kidneys in
each organism has a mechanism of its vertebrate animals.
own to remove the waste products.
11.8 EXCRETION IN HUMANS
The process of removal of the
Excretory substances in humans
waste products is called excretion.
are urea, sweat and undigested food.
EXCRETION IN ANIMALS Human body has various organs to get rid
1. In small aquatic organisms like of wastes.
amoeba, paramecium, hydra, etc., most 1. Lungs - for excretion of carbon
of the metabolic wastes are removed dioxide and water vapour produced
through the general surface of the body during respiration.
2. Skin - for excretion of urea, salt and
excess water by means of sweat
glands present in the skin.
High 3. Large Intestine - for excretion of
Concentration of Waste
some wastes along with faeces
through anus.
(Owing to Production 4. Kidneys - for excretion of products
of waste by living like urea and nitrogen in urine.
Protoplasm)
5. Liver - for removal of excess sugar by
converting it into glycogen for future
Fig. 11.16 : Excretion in Amoeba use.

TRANSPORTATION IN PLANTS AND ANIMALS 152

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11.9 EXCRETORY SYSTEM IN HUMANS person may be suffering from diabetes.

Excretory system consists of the A narrow tube called the ureter
following organs (Fig. 11.17): runs from the inner side of each kidney.
1 A pair of kidneys 2 Ureters The ureters, in turn, are connected
3 Urinary bladder 4 Urethra. to the large sac called urinary bladder.
Urine passes from the kidney through two
ureters into the urinary bladder. Urine is
collected and stored here.
Leading from the bladder is
another tube called the urethra. Urethra
works as the outlet passage for urine.

DO YOU KNOW?
About 1.00-1.8 litres of urine is
passed out by an adult human being
in 24 hours.
Fig. 11.17 : Excretory system in humans. 11.9.1 SWEATING
We all sweat on a hot summer day.
Kidneys are bean-shaped Sweating is the production of a watery
structures about 10 centimeters long. fluid from sweat glands in the skin. The
They are located just above the waist on watery fluid contains dissolved salts. In
either side of the backbone. Each kidney summer, you may have seen white
consists of a large number of coiled tube patches on your clothes. These patches
called nephrons. Nephrons act as filters. are produced by the salt present in the
They filter waste products from the blood. sweat. Sweating produces a cooling
The waste materials collected in the effect.
kidneys form the liquid urine. Urine The rate of sweating depends
contains 95 per cent water, 2.5 per cent of upon two things - humidity (the amount of
urea and 2.5 per cent waste products. water vapour in the air), and air
Glucose generally is not present in urine. movements. It is more in hot conditions.
Its presence in urine indicates that the

TRANSPORTATION IN PLANTS AND ANIMALS 153

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Sweating is much more rapid But how to separate a mixture of

when one exercises in hot climates. glucose and starch? For this, the
Heavy loss of water causes the blood to technique of dialysis is used (Fig. 11.19).
become thick, so that it no longer Dialysis is a process or technique
circulates properly. Loss of dissolved
of separating small molecules from larger
salts, due to sweating causes muscular
ones using a semi-permeable membrane
pains (cramps). In hot climates, you are,
therefore, advised two things- (i) to drink (a membrane which allows only small

lot of fluids, and (ii) to increase the intake sized molecules to pass through it).
of the salt in diet. An egg membrane or cellophane
Animals of dog family have sweat tubing can be used as a semi-permeable
glands only in the pads on their claws. membrane.
Sweating, therefore, is very limited. Through the membrane, glucose
These animals lose heat by panting will come out while starch will be retained

rapidly with the tongue hanging out. inside, if kept in a beaker of water.
Similarly, you can separate a mixture of
11.9.2 DIALYSIS starch and common salt.
What will you do if you want to
Application of Dialysis
separate a mixture of sand and water. You
The principle of dialysis is used in
will use the simple technique of filtration
an artificial key machine (also called
(Fig .11.18).
dialysis machine).

Fig. 11.18 : Filtration Fig. 11.19 : Dialysis

TRANSPORTATION IN PLANTS AND ANIMALS 154

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY 11.9
To separate a mixture of sugar and starch of water using dialysis.
Take a cellophane tubing or an egg membrane and place the given mixture in
the tubing or the membrane. Tie the loose ends. Suspend this tubing in a beaker
containing water .
Wait for half an hour.
Then, test water in the beaker for starch and sugar. First, test for starch using
iodine solution.
What do you find?
No blue black colour, showing that starch has not come out of the semi-
permeable membrane in the beaker.
Now test for the presence of glucose in the beaker, using Benedict's test.
Benedict's test
Take the water from the beaker in a test tube and add Benedict's solution to it.
Heat the mixture to boiling, then cool it. A brick red precipitate will indicate the
presence of glucose.
What do you observe?
A brick red precipitate, indicating the presence of glucose in beaker water.

This machine is used in case of connected to vein in the same arm.

individuals whose kidneys are not able to The dialysis tubing is bathed in a
perform the excretory function. As a liquid similar to blood plasma (dialysis
result, wastes accumulate in the body, solution), except that it lacks the plasma
which may even lead to death. waste substances. Consequently, wastes
A kidney machine (Fig 11.20) but not useful substances diffuse out of
receives blood through a tube connected the blood and are carried away by the
to an artery in the arm. Inside the machine.
machine, blood flows through a Kidney machines allow patients
cellulosic dialysis tubing which allows with kidney failure to remain healthy,
small molecules including urea, to pass provided dialysis is carried out after every
through its walls. The 'cleaned' blood is few days.
returned to the patient through a tube

TRANSPORTATION IN PLANTS AND ANIMALS 155

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Fig. 11.20 : A kidney machine at work. A thin semi-permeable membrane separates

the patient's blood from the dialysis solution. Wastes from the blood diffuse
into the dialysis solution.

Artery Heart Capillaries

Heartbeat Circulation Phloem
Dialysis Transpiration Diffusion
Vein Excretion Xylem
Haemoglobin

TRANSPORTATION IN PLANTS AND ANIMALS 156

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

What you have learnt

Ÿ (a) In living organisms, food, gases and waste products have to be transported
from one part of the body to another.
(b) In unicellular organisms, transport occurs by diffusion.
(c) In higher multicellular organisms, transport occurs, through blood.
(d) In higher plants, transport occurs through xylem and phloem. Movement of
water and minerals occurs through xylem, while that of food materials through
phloem.
(e) A lot of water is lost by plants in vapour form through stomata during
transpiration.
(f) Transpiration produces a suction force which pulls water from the soil to
above ground parts.
Ÿ (a) In humans, the circulatory system consists of heart, blood vessels
(arteries, veins and capillaries) and blood. Arteries carry oxygenated
blood while veins, deoxygenated blood.
(b) Blood consists of liquid plasma and cells (RBCs, WBCs and platelets).
Ÿ The red colour of blood is due to pigment haemoglobin, present inside RBCs.
Ÿ The process of removal of waste products produced in the body is known as
excretion.
Ÿ In unicellular organisms, excretion takes place through the general body surface
by the process of diffusion.
Ÿ Excretion in humans occurs from lungs (carbon dioxide and water vapour), skin
(sweat), Kidneys (urine), and liver (wastes from blood). Major excretory organ,
however, is the kidney.
Ÿ Excretory system in humans consists of a pair of kidneys, ureters, urinary bladder
and urethra. Anumber of filtering tubes called nephrons are present in each kidney.

TRANSPORTATION IN PLANTS AND ANIMALS 157

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
(I) Multiple Choice Questions - Tick mark (ü ) the correct choice.
(1) In plants ,materials are transported through
(a) xylem (b) xylem and phloem
(c) phloem (d) root hair
(2) Food is transported in the plants through
(a) xylem (b) root hair
(c) phloem (d) diffusion
(3) Water absorption is more because
(a) of xylem (b) of more transpiration
(c) of phloem (d) more water is required by the plant body
(4) Water absorption through roots can be increased by keeping the plant
(a) in bright light (b) in dim light
(c) in the shade (d) covered with a polythene bag
(5) The colour of blood is red due the presence of
(a) chlorophyll (b) anthocyanin
(c) haemoglobin (d) red blood cells
(6) In an adult normal rate of heartbeat is
(a) 72 times per minute (b) 92 times per minute
(c) 82 times per minute (d) 62 times per minute
(7) Blood cells which protect the body from infection are
(a) RBCs (b) Platelets
(c) WBCs (d) Haemoglobin

(II) Fill in the blanks:

1. In most animals, circulation is brought about by a liquid called _________.

2. Blood moves through tubes called ___________.

3. Two useful things that are circulated in all animals are________and

__________.
4. The liquid part of blood is called ___________.

TRANSPORTATION IN PLANTS AND ANIMALS 158

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

5. The substance in red blood cells that links up with oxygen is called __________.

6. The red colour of the blood is due to the presence of __________.

7. Excretion of wastes in unicellular organisms takes place by ___________.

8. Getting rid of waste materials in living beings is called____________.

9. Most liquid wastes are excreted through the ____________.

10. Skin helps in the excretion of water and ____________.

11. In man, carbon dioxide is excreted through ___________.

12. Kidneys are made up of a number of filters called ___________.

13. Kidneys are connected to the urinary bladder by long tubes called __________.

14. Artificial kidney machines work on the principle of __________.

(III) Match the Column A with those in Column B.

Column A Column B

1. Heart (a) A living pump

2. Food and oxygen (b) Can poison an organism

3. Waste products (c) Movement of materials

4. Carrier of oxygen (d) Materials needed by every living thing.

5. Circulation (e) Pipes for transport in man

6. Arteries and Veins (f) Red blood cells

(IV) Write true or false in front of the statements given below:

Statements (True /False)

1. In spirogyra, transport of materials takes place through osmosis.

_________

2. Xylem and phloem are vascular tissues. _________

3. 'Girdling experiment demonstrates food synthesis in plants.

_________

TRANSPORTATION IN PLANTS AND ANIMALS 159

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

4. Platelets help in clotting of blood. _________

5. In Hydra, excretion takes place through diffusion._________

(V) Answer the following questions:

1. How does transport of materials take place in unicellular plants?

2. Define diffusion.

3. What are two aspects of transport in higher plants?

4. Mention the functions of (a) Xylem and (b) Phloem.

5. Name a process by which water loss takes place in plants.

6. Define the following:

(i) Circulatory system (ii) Arteries (iii) Veins

7. Name the main parts of the circulatory system.

8. Mention the functions of blood.

9. Describe the functions of the following:

(i) Heart (ii) Blood vessels

(iii) Red blood cells (iv) White blood cells

(v) Platelets

10. Describe, in brief, the circulatory system in human beings.

11. Name the organ from which oxygenated blood goes into the heart.

12. Define excretion.

13. How does excretion occur in lower animals?

14. Why is the process of excretion important for living beings?

15. Name the various organs of excretion in humans.

TRANSPORTATION IN PLANTS AND ANIMALS 160

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

16. What waste products are removed by the following parts?

(a) Skin (b) Kidneys

(c) Lungs (d) Large intestine

17. Name the organs of excretion in earthworms, insects and vertebrates.

18. Define sweating.

19. What is the importance of sweating?

For more information, read on the following websites :

www.health.howstuffworks.com/adam-200142.html

http://www.funsci.com/fun3_en/blood/blood.html

TRANSPORTATION IN PLANTS AND ANIMALS 161

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

12 REPRODUCTION IN PLANTS

O
rganisms which are born, show including reproduction. In an annual
growth, reach adulthood and plant, for example, the life span is about
live for some more time till after one year, and in a perennial plant, it goes
death attaining their maximum life span. up to many years. Then the organisms
How then a particular type of organism die, leaving behind individuals of their
continue to exist? This is possible only own kind. Thi s they ensure by
through one of the most important life reproducing during their life span. If they
processes called multiplication or would not reproduce, then after their
reproduction. All living organisms death, there would be no organism left.
reproduce. What it means in simple terms The species would thus perish.
is that living organisms produce young Reproduction is thus, the means of
ones of their own kind. For examples, a perpetuation of species.
cat produces kittens which grow into adult DO YOU KNOW ?
cats. In plants too, seeds grow into young Do you know, at one time people
seedlings. The seedlings in due course of thought that living things could
time develop into mature plants, as in a come from dead (once alive) or
mango tree. non- living (never alive) matter.

Reproduction is one of the most This was however, disproved

important property of living subsequently.
organisms. It means creating new
12.2 MODES OF REPRODUCTION
life, producing young ones of their
own kind. How do you grow new plants?
You have studied about the
12.1. WHY LIVING ORGANISMS structure of a flower. You also have
NEED TO REPRODUCE? studied that flowers produce seeds.
All living organisms have a fixed Seeds are formed by the fusion of a male
life span. During their life span, the gamete with a female gamete. We sow
organisms perform various life functions these seeds and grow more plants of the

REPRODUCTION IN PLANTS 162

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

same type. This is the most common 5. Regeneration

method of growing new plants. This type 6. Vegetative propagation
of reproduction is called sexual
12.3 ASEXUAL REPRODUCTION IN
reproduction.
Can we grow new plants without PLANTS
A. Binary fission
seeds?
It is a most common method of
Yes, there are some plants which
asexual reproduction in which an
do grow without seeds. These plants give
organism divides into two. It is common
rise to new plants from a part of stem; root
among plants in unicellular organisms like
or leaf. These parts of the plants are
bacteria (Fig. 12.1) and some algae and
called vegetative parts.
For example, a new plant of rose is fungi. In this method, the organisms

produced by growing a cutting from one of divide itself into almost two equal halves.

its branches. This type of reproduction, Nucleus also divides into two parts. Each

which takes place without seeds, is called of the two parts then grows into full size.

asexual reproduction.
Sexual reproduction is
characterized by the fusion of two cells
(gametes) usually coming from two
parents. New plants are produced from
seeds.
Asexual reproduction, on the
other hand, is any type of reproduction
that does not involve the union of
.
gametes. New individual is produced
from a single parent.
Fig. 12.1 : Binary Fission in Bacteria
Methods of Asexual Reproduction B. Budding
1. Fission-binary and multiple Budding is commonly observed in
2. Budding
yeast. A bulb-like projection, called the
3. Fragmentation
bud, is formed on the body. The nucleus
4. Spore formation

REPRODUCTION IN PLANTS 163

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

of the body divides into two. Then, one of

the two nuclei passes into the bud. The
bud detaches itself from the parent body.
It grows to full size and becomes a new
individual (Fig. 12.2).

Fig. 12.3 : Fig. 12.4 :

Fragmentation Spore formation in
in Spirogyra Mucor (a fungus)

Fig. 12.2 : Budding in yeast E. Regeneration

In your garden, you mow the

C. Fragmentation grass, and again next week, it needs

In some filamentous organism mowing.
such as Spirogyra (an alga), the filaments Each organism can repair itself in

break up into two or more fragments (Fig. some or the other way. New cells grow to

12.3). Each fragment or piece grows into replace damaged or lost cells.
The ability of living things to repair
a new individual.
them-selves or grow lost parts is called
D. Spore formation
regeneration. Plants generally have
In non-flowering plants (the plants
greater powers of regeneration than
which do not produce seeds), like fungi
animals do.
(Mucor), bacteria, ferns or mosses,
formation of spores is a common method DO YOU KNOW ?
Every time you wash your hands, you
of reproduction (Fig. 12.4).
wash off hundreds of skin cells. New
Spores are very small, covered by very
skin cells are always being
thick walls which help them to survive
regenerated.
adverse conditions in the environment,
like high temperature, scarcity of water F. Vegetative Reproduction This is an
and lack of food. The spores give rise to asexual method of reproduction in plants
new organisms under favourable where vegetative parts, namely, the root,
conditions. stem or leaf, give rise to new plants. No
reproductive organs take part in this
method of reproduction and therefore, no

REPRODUCTION IN PLANTS 164

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

seeds are produced.

Vegetative Propagation by
Roots- In sweet potato, dahlia or
asparagus, the swollen roots are present.
New plants arise from these swollen roots
buried in the soil (Fig. 12.5).

Fig. 12.5 : Roots of Dahlia

Activity 12.1
Take about 10 gram of yeast powder and put it in a glass beaker containing warm
water in which a spoonful of sugar has been dissolved. Keep the beaker in a warm place (at
about 350 to 400C). After an hour, take a drop of solution from the beaker on a glass slide,
and observe the slide under the microscope. Make a sketch of what you observe. You will
observe budding in yeast. Yeast powder can be obtained from a bakery or a chemist shop.

Activity 12.2
To grow your own fungi like bread mould take a small piece of bread, a paper napkin,
a small jar or bottle with cap and water.
Now perform the activity as follows:
a) Cut a piece of napkin to fit in the bottom of the jar.
b) Pour a small amount of water into the jar-just enough to wet the paper
napkin completely.
c) Place a piece of bread on the moist paper napkin.
d) Cap the jar loosely. This is very important.
e) Place the jar in a dark place where it is not cold.
f) Look at it everyday for a week and draw pictures showing how the mould
looked during its growth stages.

REPRODUCTION IN PLANTS 165

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 12.3
Take swollen roots of sweet potato or asparagus. Place some of these roots in a
flower pot containing moist soil. Observe after a few days.
What do you observe ?
New plants will grow from the roots buried in the soil.

Vegetative Propagation by Stems- A are called 'eyes'. The 'eyes' on the potato
number of plants like potato, ginger, tuber sprout (germinate) and give rise to
sugarcane and gladiolus multiply by new plants (Fig.12.6).
stems.
Potato plants produce flowers,
fruits and seeds. Yet, they never grow into
plants.
The potato which you eat is in fact
an underground swollen stem (tuber)
which contains stored food material. If
you observe a potato with a magnifying Fig. 12.6 : A sprouted potato tuber
glass, you will find 'scars'. These scars showing the development of many
plants.

Activity 12.4
Take a potato tuber and observe it with a hand lens. You will be able to see 'eyes' on it. Now,
cut a piece of it and plant the cut piece in a pot containing soil. Observe the new plant
(roots, stem and levels) developing from the cut potato piece.

Likewise, ginger is a modified present on the stem grow into new plants.
swollen underground stem (rhizome)
Parent Plant
with stored food. Under favorable Runner
New Plant
conditions, the buds on the stem give rise
to new plants.
In strawberry, long stems grow
over the soil surface and are called
runners (Fig. 12.7). Buds which are Fig. 12.7 : Runner in strawberry

REPRODUCTION IN PLANTS 166

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Vegetative Propagation by Leaves Advantages of Vegetative Reproduction

Some plants like Bryophyllum 1. It is an easier, rapid and less
(sprout leaf plant), Begonia can be expensive method of propagation.
propagated by leaves. In Bryophyllum, Plants can be grown in much less
plantlets develop from the margins of time.
intact leaves. These plantlets, on being 2. Seedless plants can be raised.
3. Plants produced by this method are
detached, develop into independent
identical copies of the parent plants
plants (Fig. 12.8).
and show no variations.
4. Plants like banana, sugarcane, sweet
potato, rose and jasmine do not
produce viable seeds. Such plants
can be easily grown by this method.
Fig. 12.8 : Buds present in individual notches
along the margin of a Bryophyllum leaf are
capable of forming new plants.

Activity 12.5
Take a Bryophyllum leaf and place it on the moist soil in a dish or a flower pot. Take care

that margins of the leaf remain in touch with the moist soil.
Observe after 2-3 days.
Some small plants with fine roots and shoots will come out from the notches of the leaf.
Now, separate a small plant from the leaf notch and plant it in soil in another pot.

Observe what happens.

In a few days, you will find that a mature plant develops.

Artificial methods of Vegetative methods are called artificial methods of

Propagation
vegetative propagation. Some of these
Because of the advantages
methods are as follows:
offered by vegetative propagation,
1. Cutting, as in rose and sugarcane.
humans have used this method for 2. Layering, as in jasmine (Chameli)
artificial multiplication of useful plants. plant.
For this reason, such multiplication 3. Grafting, as in case of mango.

REPRODUCTION IN PLANTS 167

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

4. Tissue culture
new plant can be
1. Cutting: (a) Stem Cuttings: Cuttings
cut from the
are short lengths of the plant which, when
parent plant and
removed and placed in soil, with suitable
planted as a new
conditions develop roots and leaves and
independent
grow into independent plants. (Fig 12.9) Fig. 12.10 : Layering in
plant. This Jasmine
method is used in plants l i k e
jasmine, strawberry and bougainvillea.

3. Grafting (Fig. 12.11): In grafting,

the desired plant is
derived from two
different individuals.
The root portion
Fig. 12.9 :Cutting in rose
taken from one plant
Sometimes the stem cutting has to be is called the stock
dipped into a rooting hormone to while the stem
Fig. 12.11 :Grafting
stimulate rooting. Rose, coleus, portion from the other is called the
bougainvillea, sugarcane and cactus are scion. Scion is the plant which one
easily propagated by cuttings. wants to propagate and so it is grafted
(b) Root cuttings: In certain plants like on to the stock. The grafting ends of the
lemon, tamarind, etc., root cuttings when stock and scion are obliquely cut and
put in the damp soil give rise to roots and placed face to face. Then the two ends
shoots and form new plants. are tied tightly.
2. Layering (Fig. 12.10): The lower 4. Tissue culture: In this method, a
branch of the stem is bent so that a part of tissue is taken from the tip of a plant as it
the stem is buried under the soil. The is composed of undifferentiated and
growing tip remains above the soil immature rapidly dividing cells. The
surface. After sometime, roots grow from tissue is grown in a suitable medium
the stem part buried in the soil. Now this containing necessary nutrients and

REPRODUCTION IN PLANTS 168

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

hormones. The tissue grows into an

unorganized mass called callus. Small
.
parts of this callus are put in another
medium which induces the formation of
p lan t let s. T he p la nt le ts can be
transplanted in the soil or in pots. This
t ec h n i qu e i s a l so c al l e d m icro
propagation (Fig 12.12).

Since in a very short time, unlimited

number of plants can be produced, this
technique is being used for the Fig. 12.12 :Tissue Culture
propagation of disease-free orchids,
carnation, gladiolus, chrysanthemum,
potato, sugarcane and other plants.

Activity 12 .6
Visit a nearby nursery and note down the names of ten plants growing there. With the
help of a gardener (mali), find out the method of multiplication followed in the case of
these plants.

male gamete and the female parent

12.4 SEXUAL REPRODUCTION produces the female gamete.
In nature, sexual reproduction A male gamete is usually small
occurs in plants as well as animals. It is with a nucleus and little cytoplasm. T h e
t he mo st co mm on m et ho d of female gamete is larger, with a nucleus
reproduction. and more cytoplasm than the male.
As stated earlier, two parents, one The fusion of the two gametes is
male, and the other female, are required called fertilization. The product of fusion
for sexual reproduction. Two types of of the two gametes is called the zygote.
reproductive cells, called gametes are The male gamete in a flowering

produced from the reproductive organs of plant is a nucleus in the pollen grain; in

two parents. Male parent produces the most animals, it is the sperm. The female

REPRODUCTION IN PLANTS 169

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

gamete in plants is a large egg cell in the sepals, petals, stamens and pistil (Fig.
ovule; while in animals, it is the ovum. 12.13). Of these four parts, stamens and
After fertilization, the zygote undergoes carpels are the important parts, as these
cell division and growth. Ultimately, forms take part in sexual reproduction. The
the new individual. stamens are the male reproduction part,
Thought for you : Imagine, there was while the pistil (or carpel) is the female
no sexual reproduction in man, and part.
man could reproduce asexually. What
would be the consequences of such a
reproductive process in man, and
other organisms ?

Why do we need sexual

reproduction?
Sexual reproduction brings about
Fig. 12.13 : Parts of a flower
a fusion of gametes from both the
A stamen consists of an anther
parents. The zygote so formed thus
and a filament (Fig. 12.14). An anther is
possesses characters of both parents.
a swollen structure present on the tip of
This also helps to bring variations among
the filament. The anther produces a
new individuals. You can now understand
powdery substance called the pollen
why children of the same parents show
grains.
variations. Do you find such variations in
organisms reproducing asexually?
12.5 SEXUAL REPRODUCTION
IN PLANTS
In the last class, you have learnt
about the structure of a flower. To recall,
a flower has commonly four parts. These
parts, in order from the outside are Fig. 12.14: A stamen Fig. 12.15: A pistil

REPRODUCTION IN PLANTS 170

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Pollen grains contain the male sex mulberry, corn and cucumber.
cell or male gamete. Pollen grains are Pollination
light and can be carried by wind, water or Pollination is the transfer of pollen
insects. grains from the ripe anther to the stigma.
A pistil consists of a basal swollen The transfer of pollen grains to the stigma
portion called the ovary. The ovary can take place in two ways:
continues into a long style and ends in a 1. Within the same flower or between
knob-like part, the stigma (Fig 12.15). flowers of the same plant called Self
The ovary contains many ovules. The Pollination.
female sex cell or gamete (egg) is 2. Between flowers from different plants
present inside the ovule (Fig. 12.16). of the same species called Cross
Pollination (Fig 12.17).

Fig. 12.17 : Self and Cross

Pollination

Cross pollination often involves

Fig. 12.16: Female gamete inside the ovule various external agencies to carry pollen
grains from one flower to another one.
In many plants, the male and
These agencies may be air, water, insects
female parts are present in the same
or animals. Most flowers are pollinated by
flower. Such flowers are called
bisexual. Examples pea, rose, insects.
When you visit a garden during
mustard, sunflower and china-rose.
flowering season, you observe many
In some, the male and the female parts
butterflies, bees and moths. What are the
are borne in different flowers. Such
flowe rs are ca lled u n i s e x u a l . insects doing? Though these insects visit
the flower for nectar or honey, at the same
E x a m pl e s - d a t e p a l m , p a p a y a ,
time, they help in pollination (Fig 12.18).

REPRODUCTION IN PLANTS 171

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Perform the Activity 12.7 to see what the

insects do when they visit a flower.
When an insect visits a flower, the
pollen grains get deposited on the body of
the insects. When this insect visits
another flower, the deposited pollen
grains now get dusted on the stigma of the
second flower, thus bringing about the
transfer of pollen grains from the anther to
Fig. 12.18 : Insect and wind-pollination
the stigma (pollination).

Activity 12.7
Catch an insect immediately after it has visited a flower. Dust its body on a white paper
with a fine brush. With the help of a hand lens, observe the paper.
Do you find something on the paper?
Yes, you find that there are small rounded structures. These are the pollen grains,
which were deposited on the insect's body when it visited the flower to collect nectar or
honey.

Activity 12.8
Observe the flowers and the method of pollination in sunflower, china-rose, salvia
and maize. Make these observations in nature. Note down in your notebook what
you observe. Use a hand lens while observing the pollen grains.
You will make the following observations:
(1) The flowers in case of sunflowers, china-rose and salvia are large, coloured and
showy. But in case of maize, flowers are small and not coloured.
(2) Flowers in case of sunflower, china-rose and salvia have either scent or nectar. But
in case of maize, flowers have no scent or nectar.
(3) Pollen grains in the first three flowers are sticky and bigger in size, so that these can
stick on the insect's body. In case of maize, pollen grains are very small in
size and dry. Such pollen grains can be easily carried by wind.
The wind-blown pollen grains are caught by stigmas which hang out.
What do you conclude from your observations?

REPRODUCTION IN PLANTS 172

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(1) Flowers in case of sunflower, china-rose and salvia (Fig. 12.18) are
insect- pollinated.
(2) Flowers in case of maize are wind-pollinated.

Fertilization
Fertilization is a step between
pollination and seed formation.
The fusion of the male gamete with
the female gamete is called fertilization.
During fertilization, the following events
take place:
(1) The pollen grains germinate on the
stigma, and pollen tubes develop.
Fig. 12.20 : Process of fertilization
The pollen tubes move downwards
into the style (Fig. 12.20) . the female gamete. This
The pollen tubes are carriers of completes the process of
male gametes (Fig. 12.19.). fertilization. The fusion product or
the cell formed as a result of fusion
of the two gametes is called
Zygote. The zygote soon develops
into an embryo (body plant).

Formation of Fruit and Seed

Fig. 12.19 : Pollen grain develops into
a tube carrying male gametes.
What happens to the flower after
fertilization? If you observe carefully, you
(2) One pollen tube finally enters the may see following changes in a flower:
ovule, where female gamete is (1) The flower loses its bright colour.
located (Fig.12.20). (2) The sepals, petals, and stamens
Female gamete or egg cell is fall off.
present inside the ovule. (3) The ovary increases in size and
(3) Finally the male gamete fuses with becomes the fruit. The fruit thus is

REPRODUCTION IN PLANTS 173

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the ripened ovary. The Fruit : Let us perform the following

(4) The ovary wall becomes the fruit Activity 12.11.
wall. Fruits of the type of pea are called
(5) Inside the ovary, the ovules dry fruits. The fruit wall in such a fruit is
develop to form the seeds. thin and dry.

Activity 12.9
Take a cavity slide (a cavity slide is a microscopic slide with a small cavity in it). Put a
few drops of 3% sugar solution in the cavity. With the help of a fine brush, collect some
pollen grains from a mature anther and dust these on the sugar solution. Place a cover slip
on the cavity of the slide.
Leave the slide undisturbed for some time and then observe under the microscope.
What do you observe?
You will find small tubes coming out from the pollen grains (Fig. 12.19).

Activity 12.10
Examine the stigmas of a number of flowers found in your garden, under the low power
of a microscope. Pollen grains may be seen adhering to them. Now place a drop of water
and crush the stigmas between two slides. You may see pollen tubes.

Activity 12.11
Examine a pea fruit and a mango fruit. Remove the outer covering in both these
fruits. What do you observe?
In case of pea fruit, once the outer green
covering is removed, the rounded seeds
become visible (Fig. 12.21). The fruit wall in pea
is thin and dry.
In a mango fruit, after the removal of the
outer covering, you find the freshly portion which
you eat. Inside the freshly portion, a stony part of
the fruit wall is present. Seed is present inside
Fig. 12.21 : Fruit of pea Fig. 12.22 : Fruit of mango

REPRODUCTION IN PLANTS 174

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the stony wall (Fig. 12. 22). The fruit wall in mango has, therefore three layers:-
(i) Outer skin (epicarp).
(ii) Middle fleshy portion (mesocarp), and
(iii) Inner stony wall (endocarp).

Activity 12.12
Collect the fruits of bean, lady finger, sun flower, maize, tomato, brinjal, orange,
coconut and plum. Study these fruits and classify them as dry and fleshy fruits giving
reasons.

Examples of dry fruit : Cotton,

lady finger, maize, sunflower, bean.
On the other hand, mango fruit is a
fleshy fruit, as the fruit wall is thick and
fleshy.
Examples of fleshy fruit :
Fig. 12.23 : Structure of gram seed
Tomato, brinjal, orange, coconut, plum.
new plant. The cotyledons often contain
Functions of fruits
reserve food material for the developing
(I) The fruit wall gives protection to
plant.
the seeds and therefore, to the
embryo.
12.6 DISPERSAL OF SEEDS
(Ii) The fruit is a store house of food
material. AND FRUITS
(Iii) The fruit helps in the dispersal of For a seed to give rise to a new

seeds. plant, certain favourable conditions are

Seed necessary. A seed must fall on a suitable

A seed contains an embryo, one place where favourable conditions are
or two cotyledons and a protective seed present. How are seeds carried or
coat (Fig 12.23). The embryo, after dispersed to such a place?
germination of the seed, develops into a Can you imagine what would happen if
the seeds were to germinate near the
plant itself and not get dispersed to distant

REPRODUCTION IN PLANTS 175

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

places?
Let us study the following seeds or
fruits to know about the mechanism of
dispersal.
Collect seeds/ fruits of drumstick, maple,
calotropis (madar), gokhru (tribulus), okra Fig. 12.24 : Seed of madar Fig. 12.25 : Fruit of maple

(xanthium) and coconut, with the help of

your class teacher.
Examine these seeds or fruits.
What do you find?
You will find different situations:-
(I) In some cases like madar ( Fig 12.
24), the seeds are small and dry. A (A) (B)
Fig. 12.26 :A. Fruit of gokhru B. Fruit of Xanthium
fine tuft of fine hair is present on the
tip of each seed. These seeds are
carried to far- off places by wind.
(ii) In maple, the fruit has flat, wing-
like light structure (Fig 12.25). Like
madar, these fruits are dispersed
by wind. Fig. 12.27 : Fibrous fruit of coconut dispersed by water

(iii) In gokhru and xanthium, the fruits the parent plant by water currents.
are thorny (Fig 12.26) and stick to Thus, seeds and fruits may be

our clothes as we pass by them. dispersed to places away from the parent

These fruits also stick to bodies of plant by various means like wind,

passing animals. The animals as animals, or water.

well human beings help in

Seed dispersal helps the plants to
dispersal.
(i) prevent overcrowding, (ii) avoid
(iv) In case of coconut which is grown
competition for water, mineral and
on the sea shore, the fruit is large
sunlight, and (iii) spread to new habitats.
and fibrous (Fig 12.27). It falls in
water, and being fibrous it floats in
water, it is thus carried away from

REPRODUCTION IN PLANTS 176

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Asexual reproduction Binary fission Bisexual

Budding Cutting Embryo
Fertilization Gametes Grafting
Layering Pollination Regeneration
Tissue culture Unisexual Vegetative propagation

What you have learnt

? Reproduction is the process in which living organisms produce new
individuals of their own kind. It is the means of perpetuation of species.
? Broadly, there are two modes of reproduction - Asexual and sexual.
? Asexual reproduction involves only one parent. Sex organ or gametes are not
involved.
? Different types of asexual reproduction are fission, budding, fragmentation,
spore formation, regeneration and vegetative reproduction.
? Sexual reproduction involves two parents. Two types of gamete are formed.
The male parent produces the male gamete (sperm) and the female parent
produces the female gamete (ovum).
? In higher plants, flowers are the reproductive organs. Stamens are the male
reproductive organs producing male gamete, while pistil is the female
reproductive part producing the female gamete or egg inside the ovule.
? Pollination (transfer of pollen grains from the anthers to the stigma) and
fertilization (fusion of male gamete with the female gamete) results in fruit and
seed.
? Fertilized egg is called zygote.
? Sexual reproduction brings about variations among new individuals. No
variation is caused by asexual reproduction.
? Seed dispersal takes place by wind, water and animals.

REPRODUCTION IN PLANTS 177

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
(I) Multiple choice questions - Tick mark (ü) the correct choice.

1. The common method of reproduction in bacteria is

(a) budding (b) fragmentation

(c) binary fission (d) all the above

2. Budding is commonly seen in

(a) Yeast (b) Grasses

(c) Amoeba (d) Bryophyllum

3. Reproduction or propagation by stem is common in

(a) Rose (b) Potato

(c) Sweet potato (d) Bryophyllum

4. Unisexual flowers are found in

(a) Mulberry (b) Mustard

(c) Pea (d) Sunflower

5. A seed consists of

(a) Embryo (b) Seed coat and cotyledons

(c) Embryo and seed coat (d) Seed coat and endosperm

6. An embryo of a seed consists of

(a) Plumule (b) Radicle, plumule and cotyledons

(c) Plumule and radicle (d) Radicle and cotyledons

(II) Fill in the blanks:

(a) Budding is a kind of _____________ reproduction.

(b) The amount of cytoplasm in the parent cell is ______________ than

the amount in the bud.

(c) Yeast cells reproduce by _____________.

REPRODUCTION IN PLANTS 178

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(d) Binary fission produces cells of ______________ size.

(e) Budding produces cells of ___________size.

(f) Fungi, ferns and mosses reproduce by_____________.

(g) Male sex cells in plants are called __________.

(h) The two kinds of pollination are ________________ and

___________.

(III) State whether the statement given below are true or false:-

Statements False/True

(a) Asexual reproduction is more common than the sexual reproduction.

(b) Producing life is called respiration.

(c) Bacteria and yeast reproduce by asexual reproduction.

(d) Reproduction by spores is a method of asexual reproduction.

(e) A potato tuber is really an underground stem.

(f) A whole new plant can grow from the eye of a tuber.

(g) Cutting and grafting are natural means of reproduction.

(h) Most organisms have the capacity of regeneration in some or the

other ways.

(i) Stamens make eggs cells.

(j) A fertilized egg becomes a seed.

(k) Flowers which possess stamens and pistils are called unisexual.

(l) Insect pollinated flowers are brightly coloured.

(IV) Differentiate between the following:

1. Asexual reproduction and sexual reproduction.

2. Binary fission and budding.

3. Self pollination and cross pollination

REPRODUCTION IN PLANTS 179

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

4. Insect pollination flowers and wind pollination flowers

5. Zygote and embryo

(V). Find the odd one out, giving reasons:

1. Gamete, budding, fragmentation, regeneration.

2. Cutting, grafting, layering, binary fission.

3. Ovary, stigma, style, pollen grain.

(VI) Name the following:

1. Part of the flower where ovule is found.

2. Three agents of pollination.

3. The place where fertilization occurs in the flowering plant.

(VII) Mention the functions of the following:

1. Flower 2. Anther

3. Ovary 4. Stigma

5. Seed dispersal

(VIII) Answer the following Questions:

1. Why is reproduction necessary for living organisms?

2. How much of the parent's nuclear material does each daughter cell get

during reproduction by binary fission?

3. What kind of reproduction is binary fission?

4. How many parents take part in binary fission?

5. Describe the various methods of asexual reproduction?

6. Describe the various methods of vegetative reproduction?

7. Mention two characteristic features of wind Pollinated flowers.

8. Mention two features of insect-pollinated flowers.

9. Describe the various steps leading to the formation of seeds in plants.

REPRODUCTION IN PLANTS 180

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

10. Describe the various ways by which seeds are dispersed.

(IX) Spell the missing word

Fill in the missing letters to spell the terms that fit the definition

1. ___ t ___ g ___ a (a) Top part of pistil

2. ___g ____ (b) Female gamete

3. ___ m ___ r ___ o (c) Baby plant

4. ___u ___d ___ n ___ (d) Method of asexual reproduction

(X) Spot the odd term

In each of the following set one terms does not belong to the set. Circle

that term.

1. Sexual reproduction asexual reproduction one parent

2. Sexual reproduction asexual reproduction two parents

3. Binary fission bacteria yeast

4. Binary fission budding yeast

5. Stamen anther style

For more information, read on the following websites:

www.edumedia-science. com/a437_P2-blog-call.html

http:///koning.ecsu.ctstate4.edu/plants_Human/flowerstructure.html.

REPRODUCTION IN PLANTS 181

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

13 MOTION AND TIME

I
n class VI, you learnt about different It is common experience that the
types of motions. You learnt that a motion of some objects is slow while that
motion could be along a straight line, of some other is fast.
it could be circular or periodic. Can you
recall these three types of motions? 13.1 SLOW OR FAST
Table 13.1 gives some common We know that some vehicles move
examples of motion. Identify the type of faster than others. Even the same
motion in each case. vehicles may move faster or slower at
Table 13.1: Some examples of different times. Make a list of ten objects
different types of motion moving along a straight path. Group the
Example of Type of motion motion of these objects as slow and fast.
Motion Along a straight How did you decide which object is
line/circular/ moving slowly and which one is moving
periodic fast?
Soldiers in a If vehicles are moving on a road in
march past the same direction, we can easily tell
Bullock cart which one of them is moving faster than
moving on a
the other.
straight road
Hand of an
ACTIVITY 13.1
athlete in a race
Look at Fig. 13.1. It shows the
Pedal of a bicycle
position of some vehicles moving on a
in motion
road in the same direction at some instant
Motion of the earth
around the sun of time. Now look at Fig. 13.2. It shows the

Motion of a swing position of the same vehicles after some

Motion of a time. From your observation of the two
Pendulum figures, answer the following question:
Which vehicles is moving faster of

MOTION AND TIME 182

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

all? Which one of them is moving the that covered by bus. Would you say that
slowest of all ? the bus is moving faster than the bicycle?
We often say that the faster vehicle
has a higher speed. In a 100- metre race it
is easy to decide whose speed is the
highest. One who takes shortest time to
cover the distance of 100 metres has the
highest speed.

13.2 SPEED
You are probably familiar with the
Fig. 13.1 : Vehicles moving in the same
direction on a road word speed. In the example given above,
a higher speed seems to indicate that a
The distance moved by objects in
given distance has been covered in a
a given interval of time can help us to
shorter time, or a large distance covered
decide which one is faster or shower. For
in a given time.
example, imagine that you have gone to The most convenient way to find
see off your friend at the bus stand. out which of the two or more objects are
Suppose you start pedalling your bicycle moving faster is to compare the distances
at the same time as the bus begins to moved by them in a unit time. Thus, if we
move. know the distance covered by two buses
in one hour, we can tell which one is
slower. We call the distance covered by
an object in a unit time as the speed of the
object.
When we say that a car is moving
with a speed of 50 kilometers per hour, it
implies that it will cover a distance of 50

Fig. 13.2 : Position of vehicles shown in

kilometers in one hour. However, a car
Fig. 13.1 after some time seldom moves with a constant speed for
one hour. Infact, it starts moving slowly
The distance covered by you after
and then picks up speed. So, when we
5 minutes would be much smaller than

MOTION AND TIME 183

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

say that the car has a speed of 50 13.3 MEASUREMENT OF TIME

kilometers per hour, we usually consider If you did not have a clock, how
only the total distance covered by it in one would you decide what time of the day it
hour. We do not bother whether the car is? Have you ever wondered how our
has been moving with a constant speed or elders could tell the approximate time of
not during that hour. The speed calculated the day by just looking at shadows?
here is actually the average speed of the How do we measure time interval
car. In this book we shall use the term of a month? A year?
speed for average speed. So, for us the Our ancestors noticed that many

speed is the total distance covered events in nature repeat themselves after

divided by the total time taken. Thus, definite intervals of time. For example,
they found that the sun rises everyday in
Total distance covered
Speed = the morning. The time between one
Total time taken
sunrise and the next was called a day.
In everyday life we seldom find objects
Similarly, a month was measured from
moving with a constant speed over
one new moon to the next. A year was
long distance or for long durations of
fixed as the time taken by the earth to
time. If the speed of an object moving
complete one revolution of the sun.
along straight line keeps changing, its Often we need to measure
motion is said to be non-uniform. On intervals of time which are much shorter
the other hand, an object moving along than a day. Clocks or watches are
a straight line with a constant speed is perhaps the most common tim e
said to be in uniform motion. In this measuring devices. Have you ever
case, the average speed is the same wondered how clocks and watches
as the actual speed. measure time?
The working of clocks is rather
We can determine the speed of a
complex. But all of them make use of
given object once we can measure the
some periodic motion. One of the most
time taken by it to cover a certain
well- known periodic motions is that of a
distance. In class VI you learnt how to
simple pendulum.
measure distance. But, how do we A simple pendulum consists of a
measure time? Let us find out. small metallic ball or a piece of stone

MOTION AND TIME 184

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

suspended from a rigid stand by a thread of the pendulum is released after taking it
{Fig13.4 (a)}. The metallic ball is called slightly to one side, it brings to move to
the bob of the pendulum. and fro [Fig.13.4(b)]. The to and fro
Fig13.4 (a) shows the pendulum motion of a simple pendulum is an
at rest in its mean position. When the bob example of a periodic or an oscillatory
motion.
The pendulum is said to have
completed one oscillation when its bob,
started from its mean position O, moves
to A, to B and back to O. The pendulum
also completes one oscillation when its

(a) Wall clock (b) Table clock bob moves from one extreme position A to
the other extreme position B and comes
back to A. The time taken by pendulum to
complete one oscillation is called its time
period.
ACTIVITY 13.2
Set up a simple pendulum as shown
(c) Digital clock Fig 13.4 (a) with a thread or string of
Fig. 13.3: Some common clocks
length nearly one metre. Switch off
fans nearby. Let the bob of the
pendulum come to rest at its mean
position. Mark the mean position of the
bob on the floor below it or on the wall
behind it.
To measure the time period of
the pendulum we will need a
stopwatch. However, if a stopwatch is
not available, a table clock or a
? A ? B wristwatch can be used.
O
To set the pendulum in motion,
Fig. 13.4(b): Different positions of the bob of
an oscillating simple pendulum gently hold the bob and move it slightly

MOTION AND TIME 185

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

called quartz clocks. The time

to one side. Make sure that the string
measured by quartz clocks is much
attached to the bob is taut while you
more accurate than that by the clocks
displace it.
available earlier.
Now release the bob from its
displaced position. Remember that the Table 13.2
bob is not to be pushed when it is
Time period of a simple pendulum
released. Note the time on the clock
Length of the string = 100 cm
when the bob is at it mean position.
S.No. Time taken for 20 Time period
Instead of the mean position you may
oscillations
note the time when the bob is at one of
1. 42 s 2.1 s
its extreme positions. Measure the time
2.
the pendulum takes to complete 20
3.
oscillations. Record your observations
in Table 13.2. The first observation
shown is just a sample. Your
observation could be different from this. UNITS OF TIME AND SPEED
The basic unit of time is a second.
Repeat this activity a few times and
Its symbol is s. Larger units of time are
record your observations. By dividing
minutes (min) and hours (h). You already
the time taken for 20 oscillations by 20,
know how these units are related to one
get the time taken for one oscillation, or
another.
the time period of the pendulum.
What would be the basic unit of
Is the time period of your speed?
pendulum nearly the same in all cases? Since the speed is distance/ time,
the basic unit of speed is m/s. Of course, it
Note that a slight change in the
could also be expressed in other units
initial displacement does not affect the
such as m/min or km/h.
time period of your pendulum.
You must remember that the
Nowadays most clocks or symbols of all units are written in
watches have an electric circuit with singular. For example, we write 50 km
one or more cells. These clocks are and not 50 kms or 8 cm and not 8cms.

MOTION AND TIME 186

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

There is an interesting story about the discovery that the time period of a given
pendulum is constant. You might have heard the name of famous scientist Galileo Galilie
(A.D.1564-1642). It is said that once Galileo was sitting in a church. He noticed that a
lamp suspended from the ceiling with a chain was moving slowly from one side to the
other. He was surprised to find that his pulse beat the same number of times during the
interval in which the lamp completed one oscillation. Galileo experimented with various
pendulums to verify his observation. He found that a pendulum of a given length takes
always the same time to complete one oscillation. This observation led to the
development of pendulum clocks. Winding clocks and wristwatches were refinements of
the pendulum clocks.

Yasir is wondered how many counting aloud from “two thousand and
seconds there are in a day and how many one” to "two thousand and ten”. The
hours in a year. Can you help him? pulse of a normal healthy adult at rest
Different units of time are used beats about 72 times in a minutes that is
depending on the need. For example, it is about 12 times in 10 seconds. This rate
convenient to express your age in years may be slightly higher for children.
rather than in days or hours. Similarly, it
will not be wise to express in years the
time taken by you to cover the distance
between your home and your school. Saba wondered how time was
measured when pendulum
How small or large is a time
clocks were not available .
interval of one school? The time taken in
saying aloud “two thousand and one” is
nearly by one second. Verify it by
The smallest time interval that can be measured with commonly available clocks and
watches is one second. However, now special clocks are available that can measure
time intervals smaller than a second. Some of these clocks can measure time intervals
as small as one millionth or even one billionth of a second. You might have heard the
terms like microsecond and nanosecond. One microsecond is one millionth of a
second. A nanosecond is one billionth of a second. Clocks that measure such small time

MOTION AND TIME 187

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

intervals are used for scientific research. The time measuring devices used in sports can
measure time intervals that are one tenth or one hundredth of a second. On the other
hand, times of historical events are stated in terms of centuries or millenniums. The ages
of stars and planet are often expressed in billions of years. Can you imagine the range of
time intervals that we have to deal with?

Many time measuring devices

were used in different parts of world
before the pendulum clocks became
popular. Sundials, water clocks and sand
clocks are some examples of such
devices. Different designs of these
devices were developed in different parts
of the world (Fig 13.5).

(b) Sand clock

(c) Water clock

(a) Sundial at Jantar Mantar, Delhi

Fig. 13.5 : Some ancient time-measuring devices

MOTION AND TIME 188

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

13.4 MEASURING SPEED rest?

Having learnt how to measure time Measure the distance between
and distance, you can calculate the speed the point at which the ball crosses the
of an object. Let us find the speed of a ball line and the point where it comes to rest.
moving along the ground. You can use a scale or measuring tape.
Let different groups repeat the activity.
Record the measurements in Table 13.3.
ACTIVITY 13.3 In each case calculate the speed of the
Draw a straight line on the
ball.
ground with chalk powder or lime and You may now like to compare your
ask one of your friends to stand 1 to speed of walking or cycling with that of
2m away from it. Let your friend gently your friends. You need to know the
roll a ball along the ground in a distance of the school from your home or
direction perpendicular to the line. from some other point. Each one of you
Note the time at the moment the ball can then measure the time taken to
crosses the line and also when it cover that distance and calculate your
comes to rest (Fig. 13.6). How much speed. It may be interesting to know who
time does the ball take to come to amongst you is the fastest. Speeds of
some living organisms are given in Table
13.4. in km/h. You can calculate the
speeds in m/s yourself.
Rockets, launching satellites into
earth's orbit, often attain speeds up to
8km/s. On the other hand, a tortoise can
move only with a speed of about 8cm/s.
Can you calculate how fast is the rocket
compared with tortoise?
Once you know the speed of an
object, you can find the distance moved
by it in a given time. All you have to do is
to multiply the speed by time. Thus,
Fig. 13.6 : Measuring the speed of a ball Distance covered = Speed x Time.

MOTION AND TIME 189

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Table 13.3: Distance moved and time taken by a moving ball

Name of the group Distance moved by Time taken (s) Speed = Distance/
the ball (m) Time taken (m/s)

You might have seen a meter

fitted on top of a scooter or a
motorcycle. Similarly, meters can be
Yasir wants to know whether
there is any device seen on the dashboards of cars, buses
that measures the speed. and other vehicles. Fig 13.7 shows the
dashboard of a car. Note that one of the
meters has km/h written at one corner.
You can also find the time an object
This is called a speedometer. It
would take to cover distance while
records the speed directly in km/h.
moving with a given speed.
There is also another meter that
Time taken = Distance / Speed

Table 13.4 : Fastest speed that some animals can attain

S.No. Name of the object Speed in km/h Speed in m/s

1. Falcon 320 320 x 1000

60 x 60
2. Cheetah 112
3. Blue fish 40 - 46
4. Rabbit 56
5. Squirrel 19
6. Domestic mouse 11
7. Human 40
8. Giant tortoise 0.27
9. Snail 0.05

MOTION AND TIME 190

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

measures the distance moved by the

vehicle. This meter is known as an
odometer.

While going for a school picnic, Saba

decided to note the reading on the
odometer of the bus after every 30
minutes till the end of the journey. Later on
she recorded her readings in Table 13.5.

Can you tell how far the picnic spot

from the school was? Can you calculate
the speed of the bus? Looking at the
table, Yasir teased Saba wheather she
can tell how far they would have traveled
Fig. 13.7 : The dashboard of a car
till 9:45 AM. Saba had no answer to this
question. They went to their teacher. She 3.5 DISTANCE-TIME GRAPH
told them that one way to solve this You might have seen that
problem is to plot a distance-time graph. newspapers, magazines, etc., present
Let us find out how such a graph is information in various forms of graphs to
plotted. make it interesting. The type of graph
shown in Fig 13.8 is known as a bar
Table 13.5: Odometer reading at
different times of the journey graph. Another type of graphical
representation is a pie chart
Time Odometer Distance from
(AM) reading the starting
( F i g . 1 3 . 9 ) . Th e g rap h sho wn in
point Fig 13.10 is an example of the line graph.
8:00AM 36540 km 0 km The distance time graph is a line graph.
8:30AM 36560 km 20 km Lets us learn to make such a graph.
9:00AM 36580 km 40 km Take a sheet of graph paper. Draw
9:30AM 36600 km 60 km two lines perpendicular to each other on

10:00 AM 36620 km 80 km it, as shown in Fig. 13.11. Make the

horizontal line as XOX'. It is known as the
x-axis. Similarly mark the vertical line

MOTION AND TIME 191

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

oxygen other gases

YOY'. It is called y- axis. The point of
intersection of XOX' and YOY' is known
as origin O. The two quantities between
which the graph is drawn are shown
along these two axes. We show the nitrogen
positive values on the X-axis along OX. Fig. 13.9 : A pie chart showing
composition of air
Similarly, positive values on the y-axis
are shown along OY. In this chapter we
shall consider only the positive values of
quantities. Therefore, we shall use only
the shaded part of the graph shown in
Fig. 13.11.
Fig. 13.8: A bar graph showing runs scored by
a team in each over

Fig. 13.10 : A line graph showing change in

weight of a man with age

Yasir and Saba found out the distance

traveled by a car and the time taken by it
to cover that distance. Their data is
shown in Table 13.6.
Table 13.6 The motion of a car
S.No. Time Distance Fig. 13.11 : x-axis and y-axis on a
paper
1. 0 0
2. 1 min 1 km You can make the graph by following
3. 2 min 2 km the steps given below:
4. 3 min 3 km t Draw two perpendicular lines to
5. 4 min 4 km represent the two axes and mark
6. 5 min 5 km

MOTION AND TIME 192

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

them as OX and OY as shown in values for distance and time. Observation

Fig. 13.11. recorded as S.No. 1 in Table 13.6. Shows
t Decide the quantity to be shown along that at time 0 min the distance moved is
the x-axis and that to be shown along also Zero. The point corresponding to this
the y-axis. In this case we show the set of values on the graph will therefore be
time along the x-axis and the distance origin itself. After 1 minute, the car has
along the y-axis. moved a distance of 1 km. To mar k t his
t Choose a scale to represent the set of values look for the point that
distance and another to represent the represents 1 minute on the x-axis. Draw a
time on the graph. For the motion of line parallel to the y-axis at this point.
the car scales could be Then draw a line parallel to the x-axis
Time : 1min = 1cm
from the point corresponding to distance
Distance 1km = 1cm
1km on the y-axis. The point where these
t Mark values for the time and the
two lines intersect represents this set of
distance on the respective axes
values on the graph (Fig 13.12). Similarly,
according to the scale you have
mark on the graph paper the points
chosen. For the motion of the car
corresponding to different sets of values.
mark the time 1min, 2min,… on the x-
w Fig. 13.13 shows the set of points on
axis from the origin O. Similarly, mark
the graph corresponding to positions
the distance 1km, 2km... on the y-axis
of the car at various times.
(Fig13.12).

Fig. 13.12 : Making a graph Fig. 13.13 : Making a graph

t Now you have to mark the points on

w Join all the point on the graph as
the graph paper to represent each set of
shown in Fig. 13.13. It is a straight

MOTION AND TIME 193

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

line. This is the distance-time highest and the lowest value of each
graph for the motion of the car. quantity.
l If the distance-time graph is a l the intermediate values of each
straight line, it indicates that the quantity, so that with the scale
object is moving with a constant chosen it is convenient to mark the
speed. However, if the sped of the value on the graph ,and
object keeps changing, the graph l to utilize the maximum part of the
can be of any shape. paper on which the graph is to be
Generally, the choice of scale is drawn.
not as simple as in the example given Suppose that we have a graph
above. We may have to choose two paper of size 25 cm x 25 cm. One
different scales to represent the desired of the scales which meets the
quantities on the x-axis and the y-axis. Let a bo v e c o nd i t i o ns an d ca n
us try to understand this process with an accommodate the data of Table
example. 13.5 could be
l Let us again consider the motion of Distance: 5 km = 1cm, and
the bus that took Saba and her friends to Time: 6 min = 1cm
Can you now draw the distance-
the picnic. The distance covered and time
time graph for the motion of the bus? Is
taken by the bus are shown in Table
the graph drawn by you similar to that
Fig.13.5. The total distance covered by
shown in Fig. 13.13 ?
the bus is 80 km.If we decide to choose a
Distance-time graph provide a
scale 1km =1 cm, we shall have to draw
variety of information about the motion
an axis of length 80 cm. This is not
when compared to the data presented by
possible on a sheet of paper. On the other
the table. For example, Table 13.5 gives
hand a scale 10 km = 1 cm would require
information about the distance moved by
an axis of length only 8 cm. This scale is
the bus only at some definite time
quiet convenient. However, the graph
intervals. On the other hand, from the
may cover only a a small part of the graph
distance-time graph we can find the
paper. Some of the points to be kept in
distance moved by the bus at any instant
mind while choosing the most suitable
of time. Suppose we want know how
scale for drawing a graph are:
much distance the bus has traveled at
l the difference between the
8:15 AM. We mark the point

MOTION AND TIME 194

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

corresponding to the time (8:15 AM) on distance corresponding to the point B on

the x-axis. Suppose this point is A. Next the y-axis, OB, gives us distance in km
we draw a line perpendicular to the x-axis covered by the bus at 8:15 AM. How much
(or parallel to the y-axis) at point A. We is this distance in km? Can you now help
then mark the point, T, on the graph at Saba to find the distance moved by the
which this perpendicular line intersects it bus at 9:45 AM? Can you also find the
(Fig. 13.14). Next, we draw a line through speed of the bus from its distance-time
the point T parallel to the x-axis. This graph ?
intersects the y-axis at the point B. The

Fig. 13.14 : Distance-time graph of the bus

Bar graph Oscillation Time period

Graphs Simple pendulum Uniform motion
Non-uniform motion Speed Unit of time

What you have Learnt

? The distance moved by an object in a unit time is called its speed. Speed of
objects help us to decide which one is moving faster than the other.
? The speed of an object is the distance traveled divided by the time taken to cover
that distance. Its basic unit is metre per second (m/s).
? Periodic events are used for the measurement of time. Periodic motion of a
pendulum has been used to make clocks and watches.

MOTION AND TIME 195

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

? Motion of object can be presented in pictorial from by their distance-time graphs.

? The distance-time graph for the motion of an object moving with a constant speed
is a straight line.

EXERCISES
1. Classify the following as motion along a straight line, circular or
oscillatory motion:
(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge.
2. Which of the following are not correct ?
(i) The basic unit of time is second.
(ii) Every object moves with a constant speed.
(iii) Distance between two cities are measured in kilometers.
(iv) The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/h.
3. A simple pendulum takes 32 s to complete 20 oscillations. What is the time
period of the pendulum?
4. The distance between two stations is 240 km. A train takes 4 hours to cover
this distance. Calculate the speed of the train.
5. The odometer of a car reads 57321.0 km when the clock shows the time
08:30AM. What is the distance moved by the car. If at 08:50 AM, the
odometer reading has changed to 57336.0 km?
Calculate the speed of the car in km/min during this time. Express the speed in
km/h also.
6. Geeta takes 15 minutes from her house to reach her school on a bicycle. If the
bicycle has a speed of 2 m/s, calculate the distance between her house and

MOTION AND TIME 196

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the school.
7. Show the shape of the distance-time graph for the motion in the following
cases :
(i) A car moving with a constant speed.
(ii) A car parked on a road side.
8. Which of the following relations is correct?
Distance
(i) Speed = Distance x Time (ii) Speed =
Time
Time 1
(iii) Speed = (iv) Speed =
Distance Distance x Time

9. The basic unit of speed is:

(i) km / min (ii) m / min
(iii) km /h (iv) m/s
10. A car moves with a speed of 40 km/ h for 15 minutes and then with a speed of 60
km/ h for the next 15 minutes. The total distance covered by the car is:
(i) 100 km (ii) 25 km
(iii) 15 km (iii) 10 km
11. Suppose the two photographs, shown in Fig.13.1 and Fig.13.2, had been taken
at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in
these photographs, calculate the speed of the blue car.
12. Fig. 13.15 shows the distance-time graph for the motion of two vehicles A and B.

Fig. 13.15 : Distance -time graph for the motion of two cars

MOTION AND TIME 197

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Which one of them is moving faster?

13. Which of the following distance time graph shows a truck moving with speed
which is not constant?

(i) (ii)

(iii) (iv)

MOTION AND TIME 198

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Extend Learning - Activities and Projects

1. You can make your own sundial and use it to mark the time of the day at your
place. First of all find the latitude of your city with the help of an atlas. Cut out
a triangular piece of a cardboard such that its one angle is equal to the
latitude of your place and the angle opposite to it is a right angle. Fix this
piece, called gnomon, vertically along a diameter of a circular board as
shown in Fig. 13.16. One way to fix the gnomon could be to make a
groove along a diameter on the circular board.

Next, select an open space, which receives sunlight for most of the day.
Mark a line on the ground along the North-South direction. Place the sundial
in the sun as shown in Fig. 13.16. Mark the position of the tip of the shadow
of the gnomon on the circular board as early in the day as possible, say 8:00
AM. Mark the position of the tip of the shadow every hour throughout the
day. Draw lines to connect each point marked by you with the centre of the
base of the gnomon as shown in Fig.13.16. Extend the lines on the circular
board up to its periphery. You can use this sundial to read the time of the day
at your place. Remember that the gnomon should always be placed in the
North-South direction as shown in Fig.13.16.

Fig. 13.16

2. Collect information about time-measuring devices that were used in the

ancient times in different parts of the world. Prepare a brief write up on each

MOTION AND TIME 199

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

one of them. The write up may include the name of the device, the place of its
origin, the period when it was used, the unit in which the time was measured
by it and a drawing or a photograph of the device, if possible.

3. Make a model of a sand clock which can measure a time interval of 2

minutes (Fig.13.17) .

Fig.13.17

4. You can perform an interesting activity when you visit a park to ride a swing.
You will require a watch. Make the swing oscillate without anyone sitting on
it. Find its time period in the same way as you did for the pendulum. Make
sure that there are no jerks in the motion of the swing. Ask one of your friends
to sit on the swing. Push it once and let it swing naturally. Again measure its
time period. Repeat the activity with different persons sitting on the swing.
Compare the time period of the swing measured in different cases. What
conclusions do you draw from this activity?

MOTION AND TIME 200

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW ?

The time keeping services in India are provided by the National Physical
Laboratory, New Delhi. The clock they use can measure time intervals with an
accuracy of one millionth of a second. The most accurate clock in the world has
been developed by the National Institute of Standards and Technology in the
U.S.A. This clock will lose or gain one second after running for 20 million year.

MOTION AND TIME 201

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

14 ELECTRIC CURRENT AND CIRCUITS

Y
ou might have learnt about
electric current and circuits. Do
you remember the conditions
that are required to make an electric
current flow in a circuit?
Look at the following pictures.

(b)

(a)
What do you see in these figures? (c)
Does the bulb glow in any of the figure
shown? Can you say why? There are three conditions that need to be
fulfilled for electric current to flow: a
In (a), the source that produces source, an unbroken path, and a metal
electric current is missing. In (b), there is wire. Why do you need a metal wire?
no wire for electric current to flow through. What will happen if we introduce a rubber
In (c), the path is broken or incomplete. band in the path as shown in Fig 14.1. Will
Thus, the bulb does not glow in any of the the bulb glow? No! Can you say why? The
figures shown above. bulb does not glow as the rubber band is

ELECTRIC CURRENTS AND CIRCUITS 202

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

insulator. It does not allow electric current

to flow through it.

If we replace the rubber band with metal

key (Fig. 14.2), will the bulb glow? Yes!
the metal key, being a conductor, will let
the electric current to flow through it, thus
fulfilling all the conditions required to
make the bulb glow.

Fig.14.2: The bulb glows if a

conductor is introduced in the
path of the current

In this chapter, we will learn a little more

about electric circuits, how to represent
them conveniently, and the effects
produced by electric currents.

14.1 ELECTRIC CIRCUIT DIAGRAMS

You know what an electric circuit is. Look
at the electric circuit in Fig. 14.3. It
Fig.14.1: The bulb does not
glow if an insulator is consists of a cell, a small torch bulb, and a
introduced in the path of the
current switch. Can we represent the circuit in
some other way? Let us find out.

The unbroken path through which

electric current can flow is called an
electric circuit. Figure14.2 shows an
electric circuit consisting of a cell, a bulb,
wires, and a conductor.

Fig.14.3: An electric circuit

ELECTRIC CURRENTS AND CIRCUITS 203

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

For the sake of simplicity, Using these symbols, we can draw

scientists have developed a standard the circuit diagram for the circuit given in
method of drawing an electrical circuit. Figure14.3 as shown in Figure 14.4. This
This is known as circuit diagram. In a is when the switch is ON. Can you draw a
circuit diagram, the various components circuit diagram for a circuit given in Figure
of the circuit are represented by standard 14.3, but with switch OFF?
symbols. Table 14.1 gives the standard You can practice drawing circuit
symbols used for some common diagrams with a various elements in it.
electrical components. These are also The important points to remember are:
called elements of an electrical circuit. 1. There should be a source, that is, one
or more electric cells.
Table 14.1: Standard symbols used for some basic components of electric circuits
Component Symbol
+ -
Cell The shorter line denotes the
negative terminal and the longer
line denotes the positive terminal

+ -
Battery Two or more cells joined
together form a battery.

Switch
(also called Open Closed
key)
Open Closed

Bulb

'Off' 'On'
'Off' 'On'

Wire

ELECTRIC CURRENTS AND CIRCUITS 204

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2. The wires should not have any like a bulb when electric current passes
discontinuity (gaps). through them? Electric toasters, electric
3. The only component that can have irons, hot plates, electric hairdryers,
discontinuity is the switch. When it is electric ovens are some appliances that
open', there is a discontinuity and get hot when electric current passes
current does not flow in the circuit. through them. See Figure 14.5.

This kind of heating is called Ohmic

heating or Joule heating.

Fig.14.4: Circuit diagram

14.2 HEATING EFFECT OF CURRENT

Try touching two torch bulbs, one
which is lighted and other that is not. Be
careful when you touch the lighted bulb.
Do you feel that lighted bulb is hot to
touch? Can you say why?

This is because when an electric current

passes through a wire, the wire gets
heated up. You will come across many
appliances at your home in which electric Fig.14.5: Appliances that
work on the heating effect
current causes heating. Can you think of current

some of appliances that get heated up just

ELECTRIC CURRENTS AND CIRCUITS 205

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY

Aim: To show the heating effect of current (adult supervision required)

Material required: 1.5 V cell, two pieces of wire, a small torch bulb, insulation
tape/adhesive tape.
Procedure:
1. Strip the insulation at both ends of the wire so that 1cm of metal portion is exposed.
2. Connect the negative end of the cell to the threaded portion of the bulb with one of the
wires. Secure both ends with insulation /adhesive tape.
3. Connect the positive end of the cell to the bottom portion of the bulb with second piece
of wire. Secure both ends with insulation /adhesive tape.
4. You will find that the bulb glows. If it does not, check to see if the connections are tight
or need to be tightened. Adjust the connections till the bulb glows.
5. Touch the bulb to see how hot it is just when the connections are complete.
6. Leave this arrangement (with the bulb glowing) for some time and then touch the
bulb. You will find that the bulb is little warmer now than at the beginning. This is
because the passage of electric current has heated it up.
NOTE: Follow the precautions given below while doing this activity.
v Touch only the insulated part of the wire connected to the terminals of the cell.
v Do not perform activity near inflammable materials such as kerosene, petrol, or the
gas cylinder.
v Do not use a cell of higher voltage than specified (1.5 V).
v Do not use the plug points of your house/school.

appliance, it causes the wires to get

14.3 ELECTRIC FUSE overheated, and the appliance gets
You know that electric appliances damaged. This situation arises as a result
work when an electric current passes of some fault in the circuit and can be
through them. But have you ever extremely dangerous as it can lead to a
wondered what will happen if a large fire.
amount of electric current passes through To prevent electric appliances from
an appliance such as an electric iron, getting damaged as a result of excessive
refrigerator, television, or a hairdryer? If a passage of current through them, we use
large amount of current is drawn inside an a safety device called a fuse.

ELECTRIC CURRENTS AND CIRCUITS 206

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

A fuse is a safety device used in an An electric fuse prevents a large

electric circuit. amount of current from flowing into any
See Figure 14.6. It shows some appliance or device in your house as it
electric fuses. cuts off the supply of electric current, thus
preventing further damage.

Principle of an Electric Fuse

As you know, a wire gets heated up
Ceramic fuse
Cartridge fuses if an electric current passes through it.
Fig.14.6: Electric fuses
The amount of heating up caused
Fact File depends on the amount of current flowing
If you look carefully at a cartridge fuse, through the wire. The greater the current
you will find a number stamped on it. Can the more is the heating caused. The
you say what this number signifies? electric fuse works on the principle of
The number stamped on a fuse signifies
heating effect of current.
the amount of current (measured in An electric fuse consists of a thin
amperes, A) that can flow through the wire usually placed inside a glass or
fuse before it melts. ceramic cartridge. The wire is made of a
material that melts easily when heated. It
Where would you commonly find an
is designed such that only a certain
electric fuse?
Fuses are commonly found inside electric maximum amount of current can flow

plugs. through it. If the current exceeds this

maximum amount, the heating in the wire
causes it to melt. We say that the fuse
blows. This breaks the circuit and stops
the flow of current in the circuit. Simple,
isn't it?
The common symbol used for an
electric fuse is

Can you think of any other place where

electric fuses are likely to be found?

ELECTRIC CURRENTS AND CIRCUITS 207

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Miniature circuit breaker

A miniature circuit breaker is an automatically operated electric switch that protects an
electric circuit during an overload or short circuit. Circuit breakers are available in
different sizes, and can protect small household appliances to high voltage circuits. The
advantage circuit breakers have over fuses is that they can be reset (manually or
automatically) to restore normal operation, whereas fuses need to be replaced after single
operation.

ACTIVITY
Aim: To make an electric fuse (adult supervision
required).
Materials required: a pencil cell, about 6-8 inches length
of wire with single stand, a short piece of wire with multiple
strands, a pair of scissors, insulation/adhesive tape, a
blade, two pieces of paper folded up many times (to hold
the cell if it gets very hot), and two small pieces of pencil
eraser (you can take one and cut it into two pieces).
Procedure:
1. Cut the single strand wire into two pieces and strip the
insulation from all four ends.
2. Take the wire with multiple strands and strip the
insulation (about 2 inches) from one end. Cut the
strands from the wire and pick out just one strand. We
will use this strand as the fuse wire.
3. Take one single strand wire. Twist the tip of the wire
with one tip of the fuse wire.Take the other single
strand wire and do the same with the other tip of the
fuse wire.
4. Fix the two single strand wires on the two pieces of
erasers with the insulation tape. Make sure the fuse
wire is held taut between the two wires.
5. Connect the loose end of one of the single strand wires to the negative terminal of the
pencil cell. Secure the connection with an insulation tape.
6. Now touch the loose end of the other single strand wire to the positive terminal of the
pencil cell.
7. What do you see? You will see that the fuse wire becomes red hot and then breaks.
An electric fuse works on very similar lines.

ELECTRIC CURRENTS AND CIRCUITS 208

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

LET'S ANSWER
(I) Match the following
Column A Column B
1. Circuit diagram (a) Heating of a conductor due to an electric current
2. Joule heating (b) Fuse
3. Safety device (c) Fuse wire
4. Melts easily (d) A drawing of an electrical circuit with standard symbols
(II) Draw the standard symbol used to represent each of the following
components in a circuit diagram
1. Electric cell
2. An open switch
3. A closed switch
4. A bulb
5. A wire

Hans Christian Oersted

1777-1851

During a classroom demonstration of an 1. A magnet has two poles, namely the

experiment to his students, Oersted noticed ______ pole and the ______ pole.
that a compass needle was deflected when 2. Like poles of a magnet _______ each
an electric current was switched on nearby. other and unlike poles _______ each
He went on to study this effect further and other.
discovered the connection between 3. A magnet when suspended freely aligns
electricity and magnetism. itself in the _______ direction.

So far, you have studied about

14.4 MAGNETIC EFFECT OF
electricity and magnetism separately. But
ELECTRIC CURRENT
did you know that electricity and
Do you remember what you studied
magnetism are closely related? Perform
about magnets in Class 6? Look at the
following pictures and fill in the blanks.
the following experiment to understand
this.

ELECTRIC CURRENTS AND CIRCUITS 209

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY
Aim: To see the magnetic effect of current passing through a wire (adult
supervision required).
Materials required: 1.5 V cell, two pieces of insulated wire, a small
magnetic compass, and insulation /adhesive tape.
Procedure:
1. Strip the insulation from the two ends of both the wires.
2. Connect one end of one of the wires to the negative terminal of
the cell. Secure the connection with the insulation/adhesive
tape.
3. Connect one end of the other wire to the positive terminal of the
cell. Secure the connection with the insulation tape.
4. Place the magnetic compass near the wire.
5. Keep an eye on the needle of the magnetic compass and touch
the free ends of the wires connected to the positive and
negative terminals of the cell.
What do you see? You will see that when you touch the wire to the
positive terminal of the cell, the needle of the magnetic compass gets deflected (moves). This is because
when a current passes through the wire, it behaves like a magnet and therefore deflects the magnetic
needle of the compass.
Note: Follow the precautions given below while doing this activity.
Ÿ Touch only the insulated parts of the wire connected to the terminal of the cell.
Ÿ Do not perform the activity near inflammable materials such as kerosene, petrol or the gas
cylinder.
Ÿ Do not use a cell of a higher voltage than specified (1.5V).
Ÿ Do not use the plug points of your house/school.

piece behaves like a magnet. A magnet

ELECTROMAGNET made by using such an arrangement is
We have seen in the previous called an electromagnet. See Figure 14.7
activity that a current-carrying wire behaves Can an electromagnet attract iron pieces?
like a magnet, that is, it can deflect a
compass needle. Do you think it can also
attract iron pieces like a magnet does? Let
us find out.
Wrap a wire around a soft iron piece
(known as the core). When an electric
current is passed through the wire, the iron Fig.14.7: An
electromagnet

ELECTRIC CURRENTS AND CIRCUITS 210

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW WHAT A SOLENOID IS?

It is a device made of a long wire that has been wound many times into a tightly packed coil; it has
the shape of a long cylinder. Solenoids are used in doorbells; door locks, telephones,
loudspeakers, etc.

ACTIVITY
Aim: To make an electromagnet (adult supervision required).
Materials required: 1.5 V cell, iron nail, a safety pin, and a piece of wire.
(There are two types of wires commonly available. In one type, if you strip
the insulation you will see many thin metal strands, and in another type
there is only one thick wire. Get the one with a single thick wire).
Procedure:
1. Take a piece of wire and strip the insulation from the two ends.
2. Wind the wire around the iron nail.
3. Connect the two ends of the wire to two terminals of an electric cell
4. You have now made an electromagnet.
5. Bring this close to a safety pin.
What do you see? The safety pin gets attracted to the iron nail.
attract the safety pin? No, the iron piece
What do you observe in the above will lose its magnetic effect, i.e., it will stop
activity? We see that by passing electric behaving like a magnet and, thus, will not
current through the coil, we can produce a attract the safety pin.
magnetic effect in the nail which enables it
to attract the safety pin. [A coil is a piece of
wire twisted (or wrapped around) to from a
circle.A coil can have one or many turns.]
The strength of an electromagnet
depends on the number of turns of the
wire around the core and the amount of
current passing through it. More the
number of turns more will be the magnetic
effect. See Figure 14.8. But can you say
what will happen if the current passing Fig.14.8: An Iron nail attracts
more safety pins when wrapped
through the coil is switched off? Will it still with a coil with more number of turns

ELECTRIC CURRENTS AND CIRCUITS 211

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY
Aim: To study the behavior of an electromagnet when the current is
switched off (adult supervision required).
Materials required: An electromagnet, iron filings, wires, cardboard,
and a pencil cell.
Procedure:
1. Take an electromagnet. Connect the free ends of the wire to the
terminals of a pencil cell.
2. Take a cardboard and sprinkle some iron filings on it.
3. Now bring the electromagnet near to the iron filings. Do the filings get
attracted to the electromagnet?
4. Now remove the pencil cell from the circuit. Do the filings still get
attracted to the electromagnet? No, because the electromagnet loses
its magnetic effect when the source of electric current is removed.

USES OF ELECTROMAGNETS electric fans, washing machines,

Electromagnets have a wide range refrigerators, etc.
of uses in all sorts of devices. Can you In relays: A relay is an
electrically operated
think of some devices from everyday life
switch. Some relays use
where we use electromagnets? Have you
electromagnets to
seen cranes that use electromagnets to
control the operation of
pick up cars in scrapyards?
the switch. Some of the
Here are a few examples of
first computers ever built
devices that use magnets and
used relays.
electromagnets.
In telephones: A typical In loudspeakers: An
telephone handset electromagnet is used in
consists of two parts - the a loudspeaker which is
receiver and the used to amplify the
microphone. The receiver signals.
c o n s i s t s o f a n
electromagnet. Electromagnets are also used in electric
In electric motors: Electric bells to pull a strip of iron which makes the
motors use magnets, and
hammer hit the gong to ring the bell. Let
find wide application in
us now see how an electric bell works.

ELECTRIC CURRENTS AND CIRCUITS 212

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

14.5 ELECTRIC BELL

What do you do when you reach
your friend's house to let him/ her know
that you are at the door? Do you ring the
doorbell? Do you know what makes the
bell ring?

Step 2
Step 2

Step 2. The electromagnet attracts the soft

iron strip. The hammer attached to the strip
then hits the gong, causing a ring.
Let us see how an electric bell works:

Step
Step33

Step 1
Fig. 14.9: Working of an Electric Bell
Step 3. When the soft iron strip gets attracted
Step 1. When you push the switch of the bell, to the electromagnet, it no longer touches the
the electric current flows to the screw (interrupter) and hence the circuit is
electromagnet. broken,(much like a switch being turned off).

ELECTRIC CURRENTS AND CIRCUITS 213

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

This turns off the electromagnet and it can no Steps 1 to 3 repeat in quick succession
longer attract the soft iron strip. The soft iron as long as the switch is on.
strip returns to its initial position, touching the This is how we hear a continuous ring of
screw (interrupter). This results in the circuit the bell.
being complete and current flows again.

ELECTRIC BUZZER
Nowadays, we use electric buzzers and music bells, which work on a principle different from that
of the electric bell described here. Buzzers are of different types. Can you think of some places
where you use electric buzzers?

(a) ...................................... (b) ..................................... (c)..................................

LET'S ANSWER
State whether the following statements are true or false.
1. An electromagnet attracts a safety pin even when the current is turned off.
2. The strength of an electromagnet does not depend on the number of turns on the coil wrapped
around it.
3. An electromagnet is used in a loudspeaker to amplify the signals.
4. In an electric bell, the hammer hits the gong when the electromagnet attracts the soft iron strip.
5. When the soft iron strip gets attracted to the electromagnet, it gets detached from the hammer.

Electric circuit Circuit diagram Ohmic or Joule heating

Electric fuse Electromagnet Coil

ELECTRIC CURRENTS AND CIRCUITS 214

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

What you have learnt

® There are basically three conditions required to make electric current flow in a
circuit : a source to provide electric current, an unbroken path for electric
current to flow, and a conducting wire.
Electric circuit diagrams
® For the sake of simplicity, scientists have developed a standard method of
drawing an electrical circuit. This is known as a circuit diagram.
® In a circuit diagram, the various components of the circuits are represented by
standard symbols.
Heating effect of electric current
® When an electric current passes through an electric conductor, the conductor
gets heated up. This is called Ohmic heating or Joule heating.
® Electric irons, room heaters, electric ovens, water heaters, etc. use the heating
effect of current to work.
Electric fuse
® A fuse is a safety device.
® An electric fuse prevents a large amount of current from flowing into any
appliance or device in your house.
® An electric fuse consists of a thin wire made of a material that melts easily
when heated.
® The wire in an electric fuse is designed such that only a certain maximum
amount of current can flow through it. If the current exceeds this maximum
amount, the heating in the wire causes it to melt and break the electrical circuit.
Magnetic effect of electric current
® A current carrying wire can behave like a magnet deflecting the needle of the
compass.
Electromagnet
® An electromagnet consists of a piece of soft iron (called the core), with an
insulated wire wound around it.
® The soft iron piece acts like a magnet when a current passes through the wire.

ELECTRIC CURRENTS AND CIRCUITS 215

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

® A coil is a piece of a wire twisted (or wrapped around) to form a circle.

® Electromagnets are used in cranes, relays, electric motors, telephones,
loudspeakers, electric bells, etc.
Electric bell
® An electric bell consists of a battery, an electric switch, an electromagnet, an
adjusting screw (interrupter), a soft iron strip, a hammer, and a gong.

EXERCISES
A. Fill in the blanks:
1. A drawing of an electrical circuit with standard symbols is called
a/an___________(Circuit diagram/ electric diagram).
2. Hot plates, electric toasters, and electric irons get hot when switched on
because of the ___________effect of current. (Magnetic/heating)
3. A fuse is a ____________device. (Safety/heating).
4. A wire twisted in the from of a circle is called a/an ___ _____
(coil/electromagnet).
5. An ___________consists of a soft iron core with an insulated wire wound
around it. (Electromagnet/electric magnet).

B. Choose the correct answer:

1. A circuit diagram is
(a) a picture of a circuit
(b) a drawing of a circuit with standard pictures for the different electrical
components.
(c) a diagram of an electrical circuit with standard symbols for the different
electrical components.
(d) a difficult representation of an electrical circuit.
2. When an electric current passes through a wire ,the wire gets hot .This is called
(a) Joule heating (b) conduction
(c) electricity (d) thermal heating

ELECTRIC CURRENTS AND CIRCUITS 216

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

3. An electric fuse is
(a) a safety device (b) an appliance
(c) used to produce electric current (d) use to heat a room
4. When we bring a magnetic compass near a current carrying wire,
(a) it deflects the magnetic needle of the compass
(b) it makes the magnetic needle point North
(c) it makes the magnetic needle point South
(d) it has no effect on the magnetic needle
5. A coil refers to
(a) an electrical wire (b) a fuse
(c) a current carrying conductor (d) a wire twisted in the from of a circle
6. An electromagnet acts like a magnet
(a) when a current is passed through the coil
(b) all the time
(c) because it has a magnetic core
(d) only if a current does not pass through the coil.
7. In an electric bell, we have
(a) an electromagnet (b) a hammer
(c) an interrupter (d) all of these
8. In an electric bell, which of these gets attracted to the electromagnet?
(a) the hammer (b) the gong
(c) the soft iron strip (d) the screw
9. Which of these does not use heating effect of current?
(a) electric toaster (b) electric fan
(c) electric Iron (d) room heater
10. An electric fuse wire melts if the amount of current flowing through it.
(a) more than a minimum amount (b) less than a minimum amount
(c) more than a maximum amount (d) less than a maximum amount
C. Answer the following questions
1. What is an electrical circuit?
2. Draw an electrical circuit with an electrical cell, a bulb, and an 'ON' switch.
3. Why does an electric bulb get hot if it is kept 'ON' for a little while?
4. Name three appliances that use the heating effect of electric current.

ELECTRIC CURRENTS AND CIRCUITS 217

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

5. What is an electric fuse?

6. Draw an electric fuse and explain briefly how it works.
7. How can you show that an electric current has a magnetic effect?
8. What is an electromagnet?
9. Name two factors on which the strength of an electromagnet depends.
10. Explain the working of an electric bell using diagrams.

Think and Answer

1. We have seen that the heating effect of electric current has been put to use
in many appliances like toasters, heaters, etc. This kind of heating can also
be a waste in many places. Can you think of one example?
(Hint: Think of appliances, electrical wires, etc. Where there is excessive
heating.)
2. You know that the strength of an electromagnet depends on the amount of
current flowing in the coil. Do you think the magnetic strength will
increase/decrease if the amount of current in the coil is increased?
(Hint: Think what happens if the current is totally switched off. Then think
what will happen if we slowly increase the current.)
3. Do you think all electrical fuses should have the same maximum current?
(Hint: Different appliances require different amount of current.)

Fun Time
Following is a story of a professor and his students. At the end of it, you will have to
solve a puzzle. But before we start with the story, let us introduce you to a device
that is used to measure electric current.
An ammeter is a device used to measure the flow of electric current in a circuit. It is
represented by the Symbol A
You will find this bit of information useful when you solve the puzzle.
Here is the story of the professor and his students.
Once upon a time there lived a brilliant professor called Sheen Proton. He was a
wonderful teacher and also a great inventor. Along came a year when there was a
very famous science fair and the professor and his students toiled day and night to

ELECTRIC CURRENTS AND CIRCUITS 218

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

invent a very powerful device which would surely win them a prize in the fair. On the
night before the big day, Prof. Proton was putting final touches on the device when
he heard some strange sounds at his front door. He knew that his rival, an evil
professor, and his students from a neighboring school were desperate to get his
device. He quickly hid the device and jotted down something on a sheet of paper
and left it on his computer table. He was confident that neither the evil professor nor
his students would be able to decipher it. Then he slowly slipped out of the back
door. The desperate intruders broke open the door and searched the house thread
bare. However, they found nothing unusual but a sheet of paper with some strange
symbols and circles. They could not make head or tail of this and went away
dejected. Here is what Prof. Sheen Proton had written on the sheet of paper. Can
you decode his message and tell where the device was hidden?

Project Ideas
To explore the advantages and disadvantages of the heating effect of electric
current.
Materials required: Two big chart papers, the Internet, encyclopedias, books (on

ELECTRIC CURRENTS AND CIRCUITS 219

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

subject related to the topic mentioned), and bright colourful pictures of appliances
using the heating effect of electric current.
Procedure:
(a) Find out as many appliances and devices as possible, used by us, which
are based on the heating effect of electric current. Get colourful pictures
of them, and stick them on a chart paper. Write a few lines below each
picture explaining what each appliance / device is used for. Title this chart
'Uses of Heating Effect of Electric Current.'
(b) Make a second chart with the title 'Heating Effect of Electric Current-
Disadvantages'. In this chart explain how the heating effect that can be so
useful in many devices can also be a disadvantage in many other places.
Outdoor Activity
Go to an electrical repair shop and ask the technician to show you different type of
fuses. Try to gather some information about these fuses and where they are used.

For more information:

http://www.tpub.com/doeelecscience/electricalscience236.htm.
(accessed 15 Sep. 06)

Teacher's Notes
ü Take simple electrical components like cell, switch, fuse, wire etc. to the class.
Make cards with the symbols for each of these. Ask the students to match the
components with their corresponding symbols.
ü Have a discussion in the class on the advantages and disadvantages of the
heating effect of electric current.
ü Take an electric cell, a piece of wire, and a magnetic compass and show how a
current in the wire can produce a deflection in the compass needle.
ü Show an electric bell of the kind described in this chapter (many school bells are of
this type) and show the students how it works.

ELECTRIC CURRENTS AND CIRCUITS 220

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

15 LIGHT

Y ou might have seen a beam of

sunlight when it enters a room
through a narrow opening or a
hole. You may have also observed beams
of light from the headlamps of scooters,
cars and engines of trains (Fig.15 (a)).

Fig. 15.1 (b): Light House

Fig. 15.1 (a): Rail Engine 15.1 Light Travels Along A

Similarly, a beam of light can be seen from Straight Line
a torch. Some of you may have noticed a Yasir recalls an activity, in which
beam of searchlight from a light house or he looked at a lit candle first through a
from an airport tower (Fig.15.1 (b)). straight pipe and then through a bent pipe
What do these experiences (Fig.15.2). Why was Yasir not able to see
suggest? the candle flame through a bent pipe?

Fig.15.2: Looking at a candle through a straight and bent pipe

LIGHT 221
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

changes the direction of light that falls on

This activity showed that light it. This change of direction of light by a
travels along a straight line. How can we mirror is called reflection of light. Can
change the path of light? Do you know, you recall the activity in which you got the
what happens when light falls on a light of a torch reflected from a mirror? Let
polished or a shiny surface? us perform a similar activity.

Saba remembers the story of the lion

15.2 REFLECTION OF LIGHT
and the rabbit from the Panchtantra,
One way to change the direction of
in which the rabbit befooled the lion
light is to let it fall on a shiny surface. For
by showing him his reflection in
example, a shining stainless steel plate or
water (Fig.15.4).
a shining steel spoon can change the
direction of light. The surface of water can
also act like a mirror and change the path
of light. Have you ever seen the reflection
of trees or buildings in water (Fig.15.3)?

Fig.15.4: Reflection of lion in water

Activity 15.1
Take a torch. Cover its glass with a
chart paper which has three slits as
Fig.5.3: Reflection of objects in water shown in Fig.15.5.
Any polished or a shiny surface Spread a sheet of chart paper on a

can act as a mirror. What happens when smooth wooden board. Fix a plane mirror

light falls on a mirror? strip vertically on the chart paper

You might have learnt that a mirror (Fig.15.5). Now direct the beam of light on

LIGHT 222
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the mirror from the torch with slits. Place the slits.
the torch in such a way that its light is seen This activity shows how light gets
along the chart paper on the board. Now reflected from a plane mirror.
adjust its position so that the light from the Let us play around with the images

torch strikes the plane mirror at an angle formed in mirrors and know a little more

(Fig.15.5). about them.

Activity 15.2
CAUTION
Handle the lighted candle with care. It is
better if this activity is performed in the
presence of a teacher or an elder
person.

Place a lighted candle in front of a

plane mirror. Try to see the flame of the
candle in the mirror. It appears as if similar
Fig.15.5: Reflection of light from a mirror candle is placed behind the mirror. The
candle, which appears behind the mirror,
Does the mirror change the is the image of the candle formed by the
direction of light that falls on it? Now move mirror (Fig.15.6). The candle itself is the
the torch slightly to either side. Do you find object.
any change in the direction of reflected
light?
Saba wants to know, what makes
things visible to us? Yasir thinks
that objects are visible only when
light reflected from them reaches
our eyes. Do you agree
with him?

Fig.15.6: Image of a candle in a plane mirror

Look into the mirror along the

Now move the candle to different
direction of the reflected light. Do you see
positions in front of the mirror. Observe
the slits in the mirror? This is the image of

LIGHT 223
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

the image in each case. paper. Fix a plane mirror vertically on this
line. Place any small object, such as a
pencil sharpener, at the boundary of the
Yasir noted in his note book: Is it
not surprising that my image is of the third square counting from the mirror
same size as me, whether the (Fig.15.7). Note the position of the image.
mirror is small or large? Now shift the object at the boundary of the
fourth square. Again note the position of
the image. Did you find any relation
between the distance of the image from
Was the image upright in each
the mirror and that of the object in front of
case? Did the flame appear on top of the
it?
candle as in the object? Such an image is
called erect.
An image formed by a plane mirror is erect
and of the same size as the object.
Now place a vertical screen behind
the mirror. Try to obtain the image of the
candle on this screen. Can you get the Fig.15.7: Locating image in a plane mirror

candle on this screen? Now place the

screen in front of the mirror. Can you get Saba made a note in her notebook:
In a plane mirror the image is formed
the image on the screen now? You will
behind the mirror. It is erect, of the
find that the image of the candle cannot same size and is at the same
distance from the mirror as the
be obtained on the screen in either case. object is in front of it.
What about the distance of the
image from mirror? Let us perform
another activity. You will find that the image is at the same
distance behind the mirror as the object is
Activity 15.3
in front of it. Now verify this by placing the
Take a chart paper, if a chess
object anywhere on the chart paper.
board is not available. Draw on a chart
paper 64 (8x8) squares of equal size. 15.3 RIGHT OR LEFT
Draw a thick line in the middle of the When you see your image in a

LIGHT 224
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

plane mirror, is it exactly like you? Have

you ever noticed that there is one Now write down your name on a
interesting difference between you and piece of paper and hold it, in front of a
your image in a mirror? Let us find out. plane mirror. How does it appear in the
mirror?

Activity 15.4
Stand in front of a plane mirror and Yasir saw an ambulance on
the road. He was surprised to
look at your image. Raise your left hand. see that the word 'Ambulance 'in front
Which hand does your image raise (Fig. was written in a strange manner

15.8)? Now touch your right ear. Which

ear does your hand touch in your image?
Observe carefully. You will find that in the Can you now understand why the
mirror the 'right' appears ' left' and the 'left' word 'AMBULANCE' is written as in
appears 'right'. Note that only sides are Fig. 15.9? When the driver of a vehicle
interchanged; the image does not appear ahead of an ambulance looks in her/his
upside down. rear view mirror, she/he can read
'AMBULANCE 'written on it and give way
to it. It is the duty of every one of us to
allow an ambulance to pass without
blocking its way.

Fig.15.8: Left hand appears on the Fig.15.9: An ambulance

right side in the image

LIGHT 225
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

You might have observed that in the side find your image is erect and larger in size.
mirror of a scooter or a car, the images of If you increase the distance of the spoon
all the objects appear smaller than the from your face. You may see your image
objects themselves. Have you ever inverted (Fig.15.11). You can also
wondered why it is so? compare the image of your pen or pencil
instead of your face.
15.4 PLAYING WITH SPHERICAL
MIRRORS
Saba and Yasir were waiting for
their dinner. Yasir lifted steel plate and
saw his image in it. Oh! This plate acts as
a plane mirror. My image is erect and is of
the same size. Saba saw her image using
back side of a steel spoon. “Yasir look
here! you can also see my erect image
though it is smaller in size. This spoon Fig.15.10: Images from
the outer side of a spoon
also acts as a mirror of some kind”, said
Fig.15.11: Images from the
Saba. inner side of a spoon
You can also use a spoon or any
curved shining surface to see your image.
The curved shinning surface of a
spoon acts as mirror. The most common
Activity 15.5 example of a curved mirror is a spherical
Take a stainless steel spoon. Bring mirror.
the outer side of the spoon near your face If the reflecting surface of a
and look into it. Do you see your image in spherical mirror is concave, it is called a
it (Fig.15.10)? Is this image different from concave mirror. If the reflecting surface is
what you seen in a plane mirror? Is this convex, then it is called a convex mirror
image erect? Is the size of the image the (Fig.15.12).
same, smaller or larger? The inner surface of a spoon acts
Now look at your image using the like a concave mirror. While its outer
inner side of the spoon. This time you may surface acts like a convex mirror.
We know that the image of an

LIGHT 226
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

object formed by a plane mirror cannot be Activity 15.6

obtained on a screen. Let us investigate if CAUTION
it is also true for the image formed by a You will conduct Activity 15.6 in the
concave mirror. sunlight. Be careful; never look directly
towards the sun or its image as it may
damage your eyes. You may look at the
image of the sun when it is drawn on a
screen or a wall.
(a) Take a concave mirror. Hold it
(b)
facing the sun. Try to get the light
reflected by the mirror on a sheet of
paper. Adjust the distance of the paper
until you get a sharp bright spot on it
(Fig.15.14). Hold the mirror and the
Fig.15.12: A concave and a convex mirror
sheet of paper steady for a few minutes.
Why are concave and convex mirrors Does the paper start burning?
called spherical mirrors? This bright spot is in fact the
Take a rubber ball and cut a portion image of the sun. Notice that this image
of it with a knife or a hacksaw blade is formed on a screen. An image formed
(Fig.15.13 (a)) (Be careful. Ask an elder on a screen is called a real image.
person to help you in cutting the ball). Recollect that in Activity 15.2 the image
The inner surface of the cut ball is called formed by a plane mirror could not be
concave and the outer surface is called obtained on a screen. Such an image is
convex (Fig.15.13 (b)). called a virtual image.
Now let us try to obtain on the
screen the image of a candle flame
Convex surface formed by a concave mirror.

Concave surface
(a) (b)
Fig.15.14: A concave
Fig.15.13: A spherical mirror is a part of a sphere mirror forms a real
image of the sun

LIGHT 227
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 15.7 Now move the candle towards the mirror

Fix a concave mirror on a stand and place it at different distances from it.
(any arrangement to keep the mirror In each case try to obtain the image on the
steady would do) and place it on a table screen. Record your observation in Table
(Fig.15.15). Paste a piece of white paper 15.1. Is it possible to obtain the image on
on a cardboard sheet (say about 15 cm x the screen when the candle is too close to
10 cm). This will act as a screen. Keep a the mirror (Fig.15.16)?
lighted candle on the table at a distance of
about 50 cm from the mirror. Try to obtain
the image of the flame on the screen. For
this, move the screen till a sharp image of
the flame is obtained. Make sure that, the
screen does not obstruct the light from the
candle falling on the mirror. Is this image
real or virtual? Is it of the same size as the
flame?

Fig.15.16: Virtual image formed by a

concave mirror

We see that the image formed by a

concave mirror can be smaller or larger in
size than the object. The image may also
be real or virtual.
Concave mirrors are used for
many purposes. You might have seen
doctors using concave mirrors for
examining eyes, ears, nose and throat.
Concave mirrors are also used by
Fig.15.15: Real dentists to see an enlarged image of the
images formed
by a concave mirror teeth (Fig.15.17).

LIGHT 228
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Activity 15.8
Repeat Activity 15.7 now with a
convex mirror in place of a concave mirror
(Fig. 15.19).

Fig.15.17: A dentist examining a patient

The reflectors of torches,
headlights of cars and scooters are
concave in shape (Fig.15.18).
Yasir observed his image in the Fig.15.19: Images formed by a
convex mirror
shiny surface of the bell on his new
Record your observations in a
bicycle.
table similar to Table 15.1.
Could you get a real image at any
distance of the object from the convex
mirror? Did you get an image larger in size
than the object?
Can you now recognize the mirrors
used as side mirrors in scooters? These
are convex mirrors. Convex mirrors can
form images of objects spread over a
large area. So, these help the drivers to
see the traffic behind them (Fig. 15.20).

Fig. 15.18: Reflector of a torch

He found that his image was erect

and smaller in size. He wondered if the
bell is also a kind of spherical mirror. Can
you recognize the type of the mirror?
Note that the reflecting surface of
the bell is convex.
Fig.15.20: Convex mirror as
side view mirror

LIGHT 229
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Table 15.1: Image formed by a concave mirror for object

placed at different distance from it

Distance of the Smaller/larger Character of the image

object from the than the object
mirror Inverted/ Erect Real/Virtual
50 cm .... ....
40 cm .... ....
30 cm
20 cm
10 cm ....
5 cm
spectacles, telescopes and microscopes.
15.5 IMAGES FORMED BY LENSES Try to add a few more uses of lenses to
You might have seen a magnifying this list.
glass. It is used to read very small print Get some lenses. Touch and feel
(Fig. 15.21). You might have also used it them. Can you find some difference just
to observe the body parts of a cockroach by touching? Those lenses which feel
or an earthworm. The magnifying glass is thicker in the middle than at the edges are
actually a type of lens. convex lenses (Fig.15.22(a)).Those
which feel thinner in the middle than at the
edges are concave lenses (Fig.15.22(b)).
Notice that the lenses are transparent and
light can pass through them.
Let us play with lenses.

(a) (b)

Fig.15.21: A magnifying glass

Lenses are widely used in Fig.15.22: (a) A convex lens

and (b) A concave lens

LIGHT 230
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

CAUTION A convex lens converges (bends

It is dangerous to look through a lens at inward) the light generally falling on it
sun or a bright light. You should also be (Fig.15.24 (a)). Therefore, it is called a
careful not to focus sunlight with a converging lens. On the other hand, a
convex lens on any part of your body. concave lens diverges (bends outward)
the light and is called a diverging lens
Activity 15.9
(Fig. 15.24 (b)).
Take a convex lens or a
magnifying glass. Put it in the path of
(a)
sunrays. Place a sheet of paper as
shown in (Fig.15.23) . Adjust the
distance between the lens and the
paper till you get a bright spot on the
paper. Hold the lens and the paper in
(b)
this position for a few minutes. Does the
paper begin to burn?

Fig.15.24

Activity 15.10
Take a convex lens and fix it on a
stand as you did with the concave mirror.
Place it on a table. Place a lighted candle
Fig.15.23: Real image of the sun by a at a distance of about 50cm from the lens
convex lens
(Fig. 15.25 (a) ). Try to obtain the image of
Now replace the convex lens with the candle on a paper screen placed on
a concave lens. Do you see a bright spot the other side of the lens.
on the paper this time, too? Why are you You may have to move the screen
not getting a bright spot this time? towards or away from the lens to get a
We have seen in the case of sharp image of the flame. What kind of
mirrors that for different positions of the image did you get? Is it real or virtual?
object the nature and size of the image Now vary the distance of the
change. Is it true for lenses also? candle from the lens (Fig.15.25 (b)). Try to
Let us find out.

LIGHT 231
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(a) (b)
Fig.15.25: Image by a convex lens for object placed at different distances from it.

Fig.15.26: A virtual image formed by

Fig.15.27: Image formed by a concave lens
the convex lens

obtain the image of the candle flame Did you get in any position which was
every time on the paper screen by erect and magnified (Fig.15.26). Could
moving it. Record your observations as this image be obtained on a screen? Is
you did in Activity 15.7 for the concave the image real or virtual? This is how a
mirror. convex lens is used as a magnifying
glass.
It means that we can see the image In a similar fashion study the
formed by a lens from the side images formed by a concave lens. You
opposite to that of the object.
will find that image formed by a concave
lens is always virtual, erect and smaller in
size than the object (Fig. 15.27).

LIGHT 232
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

15.6 SUNLIGHT- WHITE OR colourful. Similarly, when light is reflected

COLOURED? from the surface of a compact disk (CD),
Have you ever seen a rainbow in the you see many colours (Fig. 15.29).
sky? You might have noticed that it
appears usually after the rain when the
sun is low in the sky. The rainbow is seen
as a large arc in the sky with many colours
(Fig.15.28).

Fig.15.29: A CD placed in sun

On the basis of these experiences,

could we say that the sunlight is a mixture
of different colours? Let us investigate.

Activity 15.11
Take a glass prism.Allow a narrow
beam of sunlight through a small hole in
Fig.15.28: A rainbow
the window of a dark room to fall on one
How many colours are present in a face of the prism. Let the light coming out
rainbow? When observed carefully, there of the other face of prism fall on a white
are seven colours in a rainbow, though it sheet of paper or on a white wall.
may not be easy to distinguish all of them.
Saba wants to tell you
These are- red, orange, yellow, green
that you can see a rainbow
blue, indigo and violet. [VIBGYOR] only when your back
is towards the sun

Does this mean that the

white light consists
What do you observe? Do you see
of seven colours?
colours similar to those in a rainbow
(Fig.15.30)? This shows that the sunlight
consists of seven colours. The sunlight is
You might have seen that when
said to be white light. This means that
you blow soap bubbles, they appear

LIGHT 233
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

white light consists of seven colours. Try segments. Make a small hole at the
to identify these colours and write their centre of the disc. Fix the disc loosely on
names in your notebook. the tip of a refill of a ball pen. Ensure that
Can we mix these colours to get the disc rotates freely(Fig. 15.31 (a)).
white light? Let us try. Rotate the disc in the daylight. When the
disc is rotated fast, the colours get mixed
together and the disc appears to be
whitish (Fig.15.31 (b)). Such a disc is
popularly known as Newton's disc.

Fig.15.30: A prism splits sunlight

into seven colours

Activity 15.12
Take a circular cardboard disc of
about 10 cm diameter. Divide this disc
into seven segments. Paint the seven
rainbow colours on these segments as
shown in Fig.15.31 (a). You can also
paste- coloured papers on these Fig.15.31: (a) A disc with seven colours
(b) it appears white on rotating

Saba has a brilliant idea! She has

prepared a small top with a small circular
disc with seven rainbow colours painted
on it (Fig.15.32). When the top rotates it
appears nearly white.
Fig.15.32: A top with seven colours

LIGHT 234
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Concave lens Magnified image Rear view mirror

Concave mirror Magnifying glass Side mirror

Convex lens Prism Spherical mirror

Convex mirror Rainbow Virtual image

Erect image Real image

What you have learnt

? Light travels along straight lines.
? Any polished or a shining surface acts as a mirror.
? An image which can be obtained on a screen is called a real image.
? An image which cannot be obtained on a screen is called a virtual image.
? The image formed by a plane mirror is erect. It is virtual and is of the same size as
the object. The image is at the same distance behind the mirror as the object is in
front of it.
? In an image formed by a mirror, the left side of the object is seen on the right side in
the image, and right side of the object appears to be on the left side in the image.
? A concave mirror can form a real and inverted image. When the object is placed
very close to the mirror, the image formed is virtual, erect and magnified.
? Image formed by a convex mirror is erect, virtual and smaller in size than the
object.
? A convex lens can form real and inverted image. When the object is placed very
close to the lens, the image formed is virtual, erect and magnified. When used to
see objects magnified, the convex lens is called a magnifying glass.
? A concave lens always forms erect, virtual and smaller image than the object.
? White light is composed of seven colours.

LIGHT 235
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

EXERCISES
1. Fill in the blanks:
(a) An image that cannot be obtained on a screen is called ____________.
(b) Image formed by a convex ___________is always virtual and smaller in
size.
(c) An image formed by a ____________mirror is always of the same size as
that of the object.
(d) An image which can be obtained on a screen is called a _________ image.
(e) An image formed by a concave __________cannot be obtained on a
screen.
2. Mark 'T' if the statement is true and 'F' if it is false:
(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
(b) A concave lens always form a virtual image. (T/F)
(c) We can obtain a real, enlarged and inverted image by a concave mirror.
(T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always forms a real image. (T/F)
3. Match the items given in Column I with one or more items of Column II
Column I Column II
(a) A plane mirror (i) Used as a magnifying glass.
(b) A convex mirror (ii) Can form image of objects spread over a large
area.
(c) A convex lens (iii) Used by dentists to see enlarged image of teeth.
(d) A concave mirror (iv) The image is always inverted and magnified
(e) A concave lens (v) The image is erect and of the same size as the
object.
(vi) The image is erect and smaller in size than the
object.
4. State the characteristics of the image formed by a plane mirror ?
5. Find out the letters of English alphabet or any other language known to you in
which the image formed in a plane mirror appears exactly like the letter itself.

LIGHT 236
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Discuss your findings ?

6. What is a virtual image? Give one situation where a virtual image is formed?
7. State two differences between a convex and a concave lens?
8. Give one use each of a concave and a convex mirror?
9. Which type of mirror can form a real image?
10. Which type of lens always forms a virtual image?

Choose the correct option in question 11-13

11. A virtual image larger than the object can be produced by a
(i) Concave lens (ii) Concave mirror
(iii) Convex mirror (iv) Plane mirror
12. David is observing his image in a plane mirror. The distance between the mirror
and his image is 4 m. If he moves 1 m towards the mirror, then the distance
between David and his image will be
(i) 3m (ii) 5m
(iii) 6m (iv) 8 m
13. The rear view mirror of a car is a plane mirror. A driver is reversing his car at a
speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked
behind his car. The speed at which the image of the truck appears to approach the
driver will be
(I) 1 m/s (ii) 2 m/s
(iii) 4 m/s (iv) 8 m/s

Extending Learning - Activities and

Projects
1. Play with a mirror
Write your name with a sketch pen on a thin
sheet of paper, polythene or glass. Read your
name on the sheet while standing in front of a Fig.15.33: Candle burning in water

plane mirror. Now look at your image in the mirror.

LIGHT 237
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2. A burning candle in water

Take a shoe box, open on one side. Place a small lighted candle in it. Place a clear
glass sheet (roughly 25 cm x 25 cm) in front of this candle (Fig.15.33). Try to locate
the image of the candle behind the glass sheet. Place a glass of water at its
position. Ask your friends to look at the image of the candle through the sheet of
glass. Ensure that candle is not visible to your friends. Your friends will be
surprised to see the candle burning in water. Try to explain the reason.
3. Make a rainbow
Try to make your own rainbow. You can try this project in the morning or in the
evening. Stand with your back towards the sun. Take a hosepipe or a water pipe
used in the garden. Make a fine spray in front of you. You can see different colours
of rainbow in the spray.
4. Visit a laughing gallery in some centre or a science park or a village mela.
You will find some large mirrors there. You can see your distorted and funny
images in these mirrors. Try to find out the kind of mirrors used there.
5. Visit nearby hospital. You can also visit the clinic of an ENT specialist, or a
dentist. Request the doctor to show you the mirrors used for examining ear, nose,
throat and teeth. Can you recognize the kind of mirror used in these instruments?
6. Role play
Here is a game that a group of children can play. One child will be chosen to act as
object and another will act as the image of the object. The object and the image will
sit opposite to each other. The object will make movements, such as raising a
hand, touching an ear, etc. The image will have to make the correct movement
following the movement of the object. The rest of the group will watch the
movements of the image. If the image fails to make the correct movement, she/he
will be retired. Another child will take her/his place and the game will continue. A
scoring scheme can be introduced. The group that scores the maximum will be
declared the winner.
You can read more on the following websites:
www.glenbrook.k12.il.us/gbssci/ phys/mmedia/optics/ifpm.html
www.glenbrook.k12.il.us/gbssci / phys/class /refln/u1311b.html

LIGHT 238
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW?
The mirrors can be used as weapons. Archimedes, a Greek scientist, is said to have d o n e j u s t
that more than two thousands years ago. When the Romans attacked Syracuse, a coastal city-
state in Greece, Archimedes used mirror arranged as shown in Fig. 15.34. The mirrors could be
moved in any direction. They were positioned in such a way that they reflected the sunlight on the
Roman soldiers. The soldiers were dazzled by the sunlight. They did not know what was
happening. They got confused and ran away. This was an example of triumph of ideas over
military might.

Fig.15.34: Archimedes mirrors

LIGHT 239
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

16 WATER
comes from the rainfall and snow, which
are a part of the water cycle.

I
n previous chapters, we studied that Jammu and Kashmir state is
we (animals too) depend directly or bestowed with rich resources of good
indirectly on plants. Can you guess a quality water, both surface as well as
substance on which all, including plants underground water. Glaciers, snow
beds and snow fed perennial rivers carry
depend? Also, which substance do you
large quantity of good quality water.
use in maximum amount during whole
day? Obviously, water. Water is life. One
Our water requirement depends
cannot live without water. Besides
entirely on nature. Whenever the water
drinking, bathing and washing, water is
cycle in nature is disrupted, the ecological
used for many other purposes. It is used
balance in nature is disturbed.
in the construction of houses. The
Water is often wasted during its
different industries, factories and mills
use. The rivers and the canals near the
cannot run without water. They require
big cities get polluted due to industrial
plenty of water. Growth and development
wastes or sewages which are thrown into
of plants can never be imagined without
them. Indiscriminate felling of plants by
water.
man, to satisfy his greed, has also upset

16.1 W A T E R AS A NATURAL the water cycle in nature. This has

RESOURCE resulted in water shortage. Water is

renewable only if it is protected against
Water is essential for sustenance of
wastage and pollution, and if a thick cover
life. It is an important medium for all the
of forest plants is maintained.
life processes and acts as universal
solvent. It is a prime natural resource. We
16.2 IMPORTANCE OF WATER FOR
have both the surface and ground water. SUSTAINING LIFE
India has rich water bodies consisting of Every plant, animal and human
rivers, lakes, streams and ponds. The being needs water to stay alive. But
surface and ground water available to us human beings depend on water more

WATER 240
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

than just to stay alive. We also need it for solubility. These properties make it useful
our way of life. We need water in our in the process of digestion, blood
homes to brush our teeth, cook food and circulation and excretion, etc. Water also
wash utensils. We need water for helps in regulating our body temperature
irrigation. Let us learn in detail. by the process of sweating.
1. Water in living things: Every 2. Water in the home : In our homes, we
organism consists mostly of water. Your require water for cleaning, cooking,
body is about 65 per cent water. So is that bathing and carrying away wastes.
of a mouse. An elephant and an ear of Each person may use an average
of about 260 liters of water a day in the
corn are about 70 per cent. A potato and
an earthworm are about 80 per cent home.
3. Water for irrigation: Most of the plants
water. A tomato is about 95 per cent water.
that people raise need great quantities of
All living things need a lot of water to
carry out their life processes. Plants, water. People raise most of their crops in

animals and human beings must take in areas that have plenty of rain. But to
produce enough food for their needs,
nutrients (food substances). Watery
solutions help to dissolve these nutrients people must also irrigate dry areas.

and carry them to all parts of an In J&K state, irrigation is done

organism's body. through
Every living thing must keep its (a) Canals
water supply near normal, or it will die. A (b) Wells and Tanks
person can live without food for more than (c) Tube wells
(d) Dhingri wells
two months, but can live without water for
(e) River pools
only about a week. If the body loses more
About 70,9795 acres of land is
than 20 per cent of its normal water irrigated through canals. The region
content, a person will die painfully. Human wise break up is Jammu: 21,9778
beings must take in about 2.4 litres of acres; Kashmir: 486072 acres;
water a day. This intake can be in the form Ladakh: 3945 acres .
of the water we drink, or the water in other
beverages we drink, or the water in the The seeds of many plants are
food we eat. transported by water. When they fall in
Water has properties of fluidity and water, they float and are carried away to

WATER 241
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

far off places. Several varieties of plants example, water cools the steam used in
have spread from one place to another in producing electric power from fuel. It
this manner. cools the hot gases produced in refining
oil and the hot steel made by the steel
mills.
5. Water for power: People use water to
produce electric power to light homes and
to run factories. Electric power stations
burn coal or other fuel to turn water into
steam. The steam supplies the energy to
run machines that will produce electricity.
Fig.16.1: Use of water in irrigation
Hydroelectric power stations use the
energy of falling water from waterfalls and
4. Water for Industry: The largest single
dams to turn the water turbines that drive
use of water is by industry. An industry
a generator to produce electricity.
uses water in many ways. It uses water for
cleaning fruits and vegetables before
canning and freezing them.

Fig.16.4: A hydroelectric power station

Hydroelectic Power Stations in J&K

1. The Sind Valley Hydroelectric Project
2. Mohra Hydroelectric Power Station
3. T h e P a h a l g a m H y d r o e l e c t r i c
Fig.16.2: Water is used in Fig.16.3: Water is used in soft Project
cooling hot steel drinks manufacturing
4. Lower Jhelum Hydel project
5. Salal Hydroelectric Project
It uses water as a raw material in
6. Uri Hydroelectric Dam
soft drinks, canned foods and many other 7. Dul Hasti Hydroelectric Project
products. It uses water to air-condition 8. Chutak Hydroelectric Project
9. Pakal Dul Hydroelectric Project
and clean factories. But most of the water
10. Kiru Hydroelectric Project
used by the industry is for cooling. For

WATER 242
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

6. Water for transport and recreation:

After people learned to build small boats,
they began using rivers and lakes to carry
themselves and their goods. Later, they
built larger boats and sailed across the
ocean in search of new lands and new
trade routes.
Today, people still depend on water
transportation to carry such heavy and Fig.16.6: Recreational uses of water

bulky products as machinery, coal, grain

Worksheet 16.1
and oil. 1. By what percent water is your
body?
2. By what percent water is a potato?
3. How much water do you require
for different activities? Calculate
the quantity of water used for
different activities and put them in
a tabular form.
Activities where Water is used
water is used in terms of litres
Fig.16.5: Water transportation Bathing __________
Drinking __________
Washing clothes __________
Peo ple b uild mos t of th eir
Cleaning utensils __________
recreation areas along lakes, rivers and Cleaning house __________
seas. They enjoy water sports such as 4. List any four uses of water in
swimming, fishing and sailing. Many industries.
people also enjoy the beauty of a quiet 5. What is the use of water in

lake, a thundering waterfall, or a roaring hydroelectric power stations?

surf.
Now, you must have understood the 16.3 SOURCES OF WATER
Water which fulfils all your necessities,
importance of water. Save water, water
where does it come from? Taps, tube
will save you!
wells, water tanks, rivers, lakes, etc., are

WATER 243
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

some sources of water. If you are living in Important canals of J&K.

a city, have you thought from where does 1. Jammu Region :
water come in taps? From where does (i) Ranvir Singh Canal
water come in reservoir in the village or (ii) Partap Canal
city? How do the rivers and lakes get (iii) Kathua Canal
(iv) Tawi Canal
filled? After thinking, you will realize that
(v) Duddar Canal
all these sources get water from rain. Rain
(vi) Pargol Canal
is the main source of water. (vii) Ujh Canal
(viii) Basant pur Canal
Famous Rivers of J&K : Ravi, Ujh, (ix) Raigarh Canal
Chenab, Tawi, Kishenganga, Indus, (x) Ravi Canal.
Jehlum. 2. Kashmir Region :
(i) Martand canal
1. Rivers and Lakes: Most cities that (ii) Zainagir canal
depend on rivers for water are located at (iii) Lalkul (Pohru)
(iv) Dadikul (Liddar)
the river banks. The amount of water in a
(v) Sumbal Khul (Sukhang)
river can vary from time to time. It
(vi) Nandikul (Anantnag)
depends on the amount of rain fall over (vii) Avantipur (Liddar)
the land which drains into the river and the (viii) Zainapora (Vishu)
amount of snow that melts on mountains. (ix) Rishipora Canal.
Snow on high mountains is the source of 3. Ladakh Region:
(i) Chuchot Mayur
big rivers.
(ii) Thikasay Mayur
(iii) Khangral Canal
(iv) Kharbu Thang
(v) Zangla Canal
(vi) Khaksar Canal
(vii) Khurbathang Canal .

During a dry spell, a river`s water level

may fall sharply. Then, a city may not have
enough water. For this reason, many
cities that depend on small rivers store
Fig.16.7: A river

WATER 244
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

water during rainy periods, and they

always have a good supply. Some build a
dam on the river and store water behind it
in a reservoir. Others store water in a
pond or small lake.

Fig.16.9: An ocean

3. Ground water: Many cities are not

near rivers or lakes. They use water that is
stored underground. This water comes
from rain that seeps into the ground. As it
Fig.16.8: A freshwater lake trickles downwards, it fills the space
Lakes of Jammu and Kashmir state: between grains of sand and cracks and
Famous lakes of Jammu region: pores in rocks. In time, the water reaches
(i) Sanasar lake a layer of rocks or other material that is
(ii) Mansar and Saruinsar lake watertight. The water collects above the
Famous lakes of Kashmir region:
watertight layer, and the ground becomes
(i) Dal lake
saturated (soaked). This saturated zone
(ii) Wular lake
(iii) Manasbal lake. is called an aquifier. The upper limit of the
Famous lakes of Ladakh region: zone is called the water table.
(i) Pangong lake
(ii) Tsomoriri lake

2. Sea water: Oceans are the largest

reservoir of natural water because
streams and rivers flow into them. Almost
97 per cent of all water is in the oceans.
But this water is too salty to be used for
drinking, farming and manufacturing. Fig.16.10: Ground water

WATER 245
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Limestone bodies of Reasi limestone Hot water springs are found at Tatapani
and permo- Triassic limestone bodies of near Kalakote, district Rajouri, Tatapani
warevan valley Banihal, Gulabgarh and in Dhamkund Sangaldan area of Gool
Mandi areas are good reservoirs of Valley, district Doda, and Tatowain in Rin
good quality ground water. Sirowal /Trai Nai, east of Jnshan in Marwa valley. The
belt of Jammu region contains water of these springs is Known to cure
groundwater. This water emerges in the skin diseases and therefore of great
from of springs and flowing tube wells as tourist attraction.
seen in Rajpura, Beliain, Jandi,
Banechak area of Hiranagar. This The underground water may rise
ground water is used for irrigating paddy until it finds a way out to the surface to
fields. form a flow of water called a spring. The
spring water is filtered and clean. Spring
Cities obtain underground water
water is usually cold. However, some
by drilling wells that reach below the water
springs are warm or hot.
table and pumping up the water.
WORKSHEET 16.2
1. Name the main source of water.
2. Name the main source of water at
your home.
3. What is the source of underground
water?
4. Why do we not use sea water?
Handpump Well 5. From where does water come in
rivers and streams?
6. Define water table.
7. What is a spring? Is spring water
drinkable?

16.4 DIFFERENT STATES OF WATER

Water exists in three states - solid,
liquid and gaseous. The water in wells,
ponds, rivers, lakes and seas is in the
Fig.16.11: Underground water sources liquid state. At high altitudes on

WATER 246
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

mountains or in very cold regions like the point. The freezing point of water is 00C.
North or South pole, much water freezes When the ice is kept in open, it
to form ice, the solid state. In air, water starts melting and changes into the liquid
exists as vapour, i.e., in the gaseous state, i.e., water.
state. The phenomenon of change of
The molecules that make up water one state of water into another and back
are always moving. The form, water t o t h e o r i g i na l s t a te i s c al l e d
takes, depends on how fast the molecules interchangeability.
move. The molecules in solid water (ice) The overall process can be shown as:

are close together and almost motionless.

The molecules in liquid water are far apart Ice Water Water Vapour
(Solid) (Liquid) (Gas)
and move about freely. The molecules in
water vapour, move about violently and DO YOU KNOW?
bump into one another. Ice acts as a preservative by
inhibiting the destructive action of
INTERCHANGEABILITY OF bacteria, yeast and mould.
DIFFERENT STATES OF WATER
The existence of water in three 16.5 WATER AS A SOLVENT
An important property of water is
physical states is mainly the function of
its ability to dissolve many substances.
t e m p e ra t u r e a n d p r e s s u r e . T h e
When water evaporates to form cloud, it is
interconversion of water is brought about
a pure form of water. But when it falls as
by the change of temperature and
rain water, many gases from air dissolve
pressure.
When water is heated, it changes in it. After falling on the ground, it comes in

into gaseous state. This change takes contact with several minerals and salts

place at a particular temperature, called and dissolves some of them. Hence, it is

boiling point. The boiling point of water is called a universal solvent.

Large water surfaces like rivers,
1000C.
lakes and oceans are in direct contact
When water is kept in the freezer of
with atmospheric air. The gases like
a refrigerator, it solidifies into ice. This
oxygen and carbon dioxide are soluble in
change also takes place at a particular
water. It is only the dissolved oxygen
temperature, which is called freezing
which helps aquatic organisms to survive

WATER 247
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

in water. Fish have special organs called The water droplets adhere to the dust
gills which help them in taking up the particles which are present in the air. The
dissolved oxygen. group of water droplets along with dust
particles forms clouds. The clouds are
moved from one place to another place by
wind. When water droplets in the cloud
come together, they form drops of water.
These drops of water are heavy and they
fall as rain. Thus, the cycle goes on and is
called the water cycle in nature.
Gill

WORKSHEET 16.3
Fig.16.12: The gills of a fish
Aquatic plants use carbon dioxide 1. Name the three states of water.
2. Why do fish in shallow ponds die
dissolved in water for preparation of their
during summer?
food.
3. N a m e t h e f a c t or s t h a t a r e
The solubility of gases in water
de crea ses wi t h th e inc re ase in responsible for the change of state.
4. Define temperature.
temperature. Often during the summer,
5. Draw a diagram to explain the
fish in shallow ponds die. The water in the
interchangeability of water.
ponds becomes hot due to summer heat.
6. Explain water cycle in nature.
As a result, the amount of oxygen
7. Give examples to show that water is
dissolved in water is reduced and fishes
a universal solvent.
die.
8. Name two things which cannot
dissolve in water.
16.6 WATER CYCLE IN NATURE
9. At what temperature does the water
Have you ever seen a river, or a
lake, or a sea. The water from the surface boil ?
10. At what temperature does the water
of these water bodies evaporates
freeze ?
continuously. The water vapour rises up.
The temperature goes down as we go
16.7 WATER POLLUTION
higher and higher. When the air You have learnt that water is
containing water vapour cools at upper important for all living organisms. Do you
altitudes, the water droplets are formed.

WATER 248
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

know what are the different sources of variety of waste materials which are the
water? Three fourth part of the earth is direct result of population explosion and
covered with water. Such a huge quantity large scale industrialization.
of water on earth is in oceans, while the
fresh water, which we use, is in very less CAUSES OF WATER POLLUTION
quantity. If we imagine that the total Various causes of water pollution are:
1. Domestic sewage: Discharge of
quantity of water on earth is bucketful, the
fresh water is only one teaspoonful. sewage water containing human urine
and faeces, animal dung, cloth washing,
etc., into lakes, rivers and other water
bodies is one of the most common
primary sources of water pollution,
especially near big cities. Gutter water
and faulty drainage system may also
pollute water.

Wular lake is a large fresh water lake in

Bandipora district in J&K. It faces
environmental threats including the
Fig.16.13: A sewage polluting water
conversion of large parts of the lake's
Water is regarded as polluted catchment areas into agricultural land,
w h e n i t c h an g e s i t s q u al i t y o r pollution from fertilizers and animals
composition, directly or indirectly as a waste, hunting of water fowl and
result of man`s activities, so that it migratory brids and weed infestation in
becomes less suitable for drinking the lake itself.
purposes, domestic use, agricultural
practice, fisheries or other purposes. All 2. Industrial wastes: The industrial
kinds of water resources, like ponds, wastes play a major role in the pollution of
rivers, lakes and oceans, are polluted by a water. They include toxic substances

DO YOU KNOW?
One fifth of the world`s population, 1.2 billion people, regularly drink polluted
drinking water. One person dies every six seconds from drinking disease-
contaminated water.

WATER 249
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

such as chloride, ammonia, hydrogen sea water. Oil refineries situated near sea
sulphide, different acids and salts of shore also pollute water.
metals like copper, zinc, lead, nickel,
mercury, arsenic, etc. The throwing of PREVENTION OF WATER POLLUTION
1. Septic tank treatment should be used
these wastes into water bodies is also an
for individual houses of communities.
important cause of water pollution.
2. The sewage and factory wastes have

3. Agricultural wastes: Various minerals to be cleaned before they flow into the

and organic wastes are carried to the water reservoirs.

3. Biological treatment for the sewage
lakes, rivers and other water reservoirs
should be carried out.
from agricultural fields where a variety of
4. The use of fertilizers and herbicides
fertilizers, insecticides and herbicides are
should be judicious and minimal.
applied almost throughout the year.
5. The use of synthetic detergents
should be minimized.
4. Oil pollution: Crude oil during
6. Dead bodies of humans and animals
transport in ships is discharged into the

Fig.16.14: Types of pollution

WATER 250
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

should not be thrown into the river. suspended materials. The water
7. The excreta and other garbage should becomes partly clean.
be treated in a biogas plant to get fuel 2. Filtration: In this process, the
as well as manure. partly clear water is filtered through sand
8. The water of rivers, streams, lakes filters. All insoluble impurities are
and ponds should be purified. This is removed here.
done by the government. One such 3. Chlorination: Chlorine or
example is the Ganga Purification bleaching powder is added to filtered
Project. The Government of India has water. Bleaching powder also contains
undertaken the project to prevent the chlorine. Chlorine kills bacteria. Now this
pollution of the Ganga river. Under this water is free from harmful germs. This
project, water treatment plants have water is fit for drinking purposes.
been set up to treat the industrial and 4. Aeration: Aeration improves taste
domestic waste water entering the and odour. In this process, water is
river. usually sprayed through air. The oxygen
9. A large number of trees should be in the air takes away the bad taste and
planted along the river banks. odour.
16.9 COMPOSITION OF WATER
16.8 POTABLE WATER Water is a compound. Its molecular
The water which is used for drinking formula is H2O. This formula tells us that a
purpose is known as potable water. It
WORKSHEET 16.4
should be clean and fresh. It should not 1. What is domestic sewage? What does
contain suspended or soluble impurities it contain?
and harmful germs such as bacteria. 2. Name the metals whose salts are
Water from rivers and lakes contained in industrial wastes.
contains both suspended and soluble 3. How can you say that a given sample of

impurities. Before supply, it is purified for water is polluted?

4. Why is the river water not fit for drinking
drinking purpose. The following steps are
purposes?
taken to purify water from natural 5. What are the properties of potable
resources: water?
1. Sedimentation: Alum is added to the 6. What is the importance of aeration for
water tank. It helps in quick settling of fine purifying water?
7. Why do we add alum to water tanks?

WATER 251
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

molecule of water is composed of two split into its constituent elements, i.e.,
atoms of hydrogen and one atom of hydrogen and oxygen by passing electric
oxygen. current through it. This method of using
Although boiling converts water into electricity to split the molecules is called
steam and on cooling it gives ice, the electrolysis.
chemical composition of water in its three
states, solid (ice), liquid (water) and This activity shows that water is
gaseous (steam), is the same. made up of two volumes of hydrogen and
However, water molecules can be

Fig.16.15: Supply of drinking water to a town

ELECTROLYSIS OF WATER
ACTIVITY
Fill three fourth of a voltameter with water. Add 2-3 drops of sulphuric acid to make it
good conductor of electricity. Set up the apparatus as shown in Fig. 16. 17.
Fill two test tubes with water and invert them over the two electrodes made of steel
or carbon, not allowing any water in the test tube to spill. Connect the electrodes to the
source of electricity (a battery). You will see the bubbles rising to the top of the test tubes
and gases collecting in them over the water.
Are the volumes of gases in both the tubes same? One test tube seems to be
collecting more gas than the other. After one of the test tube is filled about half with gas,
measure the height of the gas column in each test tube. The ratio of the collected gases
seems to be 2:1. When one of the test tubes is filled with gas, remove it slowly and cork it.

WATER 252
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Now test this gas by bringing a burning splinter

near its mouth and open the cork. The gas
burns with a popping sound and water is
formed. This gas is hydrogen.
Similarly, test the gas from the other test tube
when filled with gas by burning a glowing splint.
The splint catches fire and burns brightly. This
property is of oxygen gas.
Fig.16.16: Electrolysis of Water
one molecule of oxygen, i.e., the volume 4. Density: The density of water is 1g/cc
o
ratio of hydrogen and oxygen is 2:1. Thus, at 4 C.
the chemical formula of water is H2O. 5. Heat capacity: Heat capacity is the
16.10 PHYSICAL PROPERTIES OF ability of a substance to absorb heat
WATER without becoming much warmer itself.
1. Nature: Pure water is clear, colourless, This property of water is used to cool
tasteless and odourless liquid. engines and thus, prevents them from
2. Boiling point: Pure water boils at getting hot. This property of water is made
o
100 C. use of in air coolers.
3. Freezing point: Pure water freezes at 6. Conduction: Pure water is a bad
o
0 C. At higher pressure, the freezing point conductor of heat and electricity.
o
of water is slightly less than 0 C. If 7. Solubility: Water can dissolve almost
impurities are present in water, the water any substance.
o
freezes at a temperature less than 0 C.
ACTIVITY
To determine the boiling point of water.

Fill a beaker half with water. As shown in Fig.16.18, use a stand to

fix a thermometer upright in the beaker with the bulb of
thermometer immersed in the water. Heat the beaker. After some
time the water will start boiling. Note the temperature. At this time,
the thermometer shows a temperature of about 1000C. This
temperature is called the boiling point of water.
Fig.16.17: Determining the boiling point of water

WATER 253
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

ACTIVITY
To determine the freezing point of water.
Take some pieces of ice in a beaker. As shown in the figure,
stand a Celsius thermometer amongst them. Measure the
temperature of ice. The ice melts and the thermometer
o
shows a constant temperature of approximately 0 C. The
temperature remains the same till all the ice has melted.
o
You know that this temperature, 0 C is known as the
Fig.16.18: Determining the freezing
freezing point of water. point of water

Look at Fig.16.20. It is a desert cooler. Water is

kept in a tray at the bottom. A pump circulates
this water which drips on the mats kept at
sides, keeping them constantly wet. The fan
takes the warm air in from outside. The air
enters through mats and evaporates the water.
The evaporating water absorbs heat from the
air and cools it. The cool air is then pushed into
Fig.16.19: A desert cooler
the room by the fan.As a result, we get cool air.

16.11 RELATIVE VOLUME AND decreases. Water behaves differently. It

DENSITY OF WATER AND ICE contracts or takes up less volume, when
The density of a substance is the heated from 0oC to 4oC, and its density
amount of mass it contains for each unit of o
increases. Above 4 C, water expands
its volume. The density of a substance is when heated, and its density decreases.
calculated by dividing its mass by its Most substances contract when
volume, i.e., they freeze. In such substances, the
Mass
Density = density of the solid is higher than the
Volume
Most substances expand in volume density of the liquid. Again, water is an
when they are heated. Therefore, when exception. It expands when it freezes; its
substances are heated, their density density decreases. Ice floats on water

WATER 254
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

because lower density substances float in ACTIVITY

liquids of higher density. The lower Take two pods of seedlings of the same
density of ice helps in letting fish survive. plant. Water them everyday, one with
plain (tap) water and the other with saline
16.12 SALINITY OF SEA WATER water.
As sea water is salty, it cannot be used for What do you observe?
drinking. Rain water falling on earth flows The seedling which was watered with
in the form of rivulets, streams and rivers saline water did not grow properly. This
into the sea. As it flows over the land, activity shows that saline water is not
many salts in the soil dissolve in it and are suitable for agriculture.
carried into the sea. Materials released by
volcanoes and under sea springs also
add salts to the sea. Rivers also bring
fresh water to the sea, which lowers the
salinity of sea water near river mouth. Fig.16.20: Saline water is not suitable for Plants

Many plants also cannot tolerate

ACTIVITY saline water. Saline water cannot be
Take some wax in a metal bowl. Heat it used in industries either. Use of saline
slowly till it melts. Add a piece of solid water spoils the machinery gradually and
wax in molten wax. You will notice that puts it out of use.
the solid wax sinks to the bottom. This Saline water may cause metals to
shows that the solid wax is heavier than corrode.
the liquid wax. Use of saline water in heaters and
Now, put a piece of ice in a container boilers causes deposits of salts on
filled with water. The ice floats on water. heating elements and soon renders them
We can say that ice is lighter than water useless.
or ice has less density than water. The presence of dissolved salts
and gases impart a characteristic taste to
Drinking salty water makes a drinking water.
person vomit. If it is necessary to 16.13 DESALINATION OF SEA WATER
evacuate a person`s stomach, doctors The process of removing dissolved
prescribe salty water. salts from saline water is called
desalination.

WATER 255
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

membrane.
DO YOU KNOW?
3. High pressure is applied from an
Our body needs iodine. Lack of iodine
external source on saline water.
causes goitre. The drinking water
4. The pressure retains salts and allows
available in the vicinity of sea contains
only water to pass through semi-
adequate quantity of iodine. Iodine is not
permeable membrane.
found in water in high mountainous
5. Pure water collected in the tank is
regions. Hence, goitre is prevalent
used to meet the domestic need, in
among people living at high altitudes
industries and irrigation projects.
away from the sea due to lack of iodine in
their bodies. WORKSHEET 16.5
1. Which property of water makes the
Desalination of sea water is done as ice float on its surface?
follows: 2. What is the formula of density?
1. Sea water is collected in a huge tank. 3. Why is the sea water salty?
2. The tank is connected with another 4. How can sea water be used for

tank through a semi - permeable irrigation?

5. Name the element which is found in
sea water but not in water at high
mountains.

What you have learnt

? Water is essential for all living beings.
? The ocean is the major sources of water. Other sources are rivers, lakes, ponds, streams,
springs, wells and rains.
? Water from any natural surrounding is seldom safe to drink.
? People in cities get water from taps.
? Water cycle in nature is continuous.
? Water exists in three states solid, liquid and gaseous.
? The water which is used for drinking purpose is called potable water.
? Pure water is colourless, odourless, tasteless and transparent liquid.
? Ice which is a solid form of water is lighter than water.

WATER 256
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

? The lower density of ice helps in letting fish survive.

? The heat capacity of water is high and its conductivity is poor.
? Hydrogen and oxygen combines in the ratio of 2 : 1 by volume to form water.
? Water dissolves many substances.
? Oxygen dissolved in water is utilised by aquatic organisms during respiration.
? Water gets easily polluted.
? Water pollution is harmful for living organisms.
? Water pollution is caused by industries and by improper health practices.
? Water pollution can be controlled.
? Dissolved salts in water cause salinity.
? Sea water is highly saline. Each litre of this contains about 35 grams of dissolved salts.
? High salinity of water is harmful for agriculture, to animals and for human use.
? Presence of certain salts make water hard.

EXERCISES
I. Answer the following questions in one word or a figure:
1. What is the apparatus used for the electrolysis of water called?
2. What is the volume ratio for hydrogen to oxygen in water?
3. At what temperature does water change into steam?
4. At what temperature does water change into ice?
5. At what temperature is the density of water maximum?
6. What is the composition of water?
7. Which is lighter: water or ice?
8. Name the largest source of water on earth.
9. Name a liquid which is heavier than water.
10. Name a chemical which is used to kill germs in water.
II) Fill in the blanks.
1. Water helps in the__________ of seeds and fruits.
2. About 97% of water is in the __________.
3. The property of ____________makes water useful in the process of
digestion.
4. The human body has about 70% of water by ____________.
5. Seed cannot___________ without water.
6. Removing dissolved salts from saline water is called________.
7. The process of using electricity to split water molecule is called
_________.
8. The __________ of liquid water is 1 g/cc.

WATER 257
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

9. The density of water is maximum at ________.

10. The freezing point of water is_________.
III) Write 'True' or 'False' against each of the following statements:
1. Ice has lower density than water._______________
2. Rain water is the purest form of natural water._______________
3. The solubility of gases in water increases with the increase in temperature.
_______________
4. During the summer, the amount of oxygen dissolved in water is increased and
fish die. _______________
5. Pure water tastes sweet. _________________
6. The use of fertilizers pollutes water _________________
7. The ratio of oxygen to hydrogen in water is 2:1. _________________
8. The states of water are interchangeable. _________________
IV. Answer the following questions:
1. State any three physical properties of water.
2. How will you determine the freezing point of water?
3. How will you determine the boiling point of water?
4. Briefly describe the water cycle in nature.
5. Mention five uses of water.
6. How is water polluted?
7. How can pollution of water be prevented?
8. What is electrolysis? Describe in brief the electrolysis of water.
9. Mention the names of some industries which pollute water.
10. Give the names of some metals whose compounds are toxic.
11. Why is saline water not suitable for drinking?
12. What is potable water? Give its characteristics.
13. Name the elements that water is composed of.
14. Name two physical changes that take place in the water cycle.
15. How will you determine that a given sample of water is pure or polluted?
16. What is salinity? Describe the process of desalination.
V. Choose the correct answer:
1. At which temperature is the density of water maximum?
0 0 0 0
(a) 0 C (b) 4 C (c) -4 C (d) 100 C
2. What is the volume ratio of oxygen to hydrogen in water?
(a) 1:2 (b) 1:3 (c) 2:1 (d) 3:1
3. Which one of the following liquids has the greatest heat capacity?
(a) Water (b) Glycerine (c) Kerosene (d) Oil
4. Which one of the following metals is not affected by water?
(a) Sodium (b) Potassium (c) Calcium (d) Boron

WATER 258
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW ?
? There is an area in the Caribbean Sea known as the Bermuda
Triangle. Many ships and planes have mysteriously
disappeared here. Is there some supernatural force at work
here, spiriting people away to another planet or pulling them
to their death in the sea below? Although many
disappearances are reported to have happened in calm
weather, investigations show that an area is given to sudden
storms. Hurricanes often begin here and it is not surprising
that many planes and ships have been lost.

? The Ancient Greeks write of an idyllic island called

Atlantis which disappeared into the sea. Why did it
disappear? According to the story, the sea god was so
angry at how greedy and dishonest the people had
become, he shook the island for a day and a night
before the sea swamped it forever. Many people have
wondered whether Atlantis really existed and historians
think that the legend is based on the island of Thera,
known as Santorini. In 1450 B.C., a huge volcanic
explosion shook the island. Most of th island disappeared beneath the sea and tidal wave
flooded the island round about. Probably destroying the Minoan Civilization of the nearby
island, Crete.

? Although the oceans are so important, we are

polluting them in many different ways. Millions of
tons of oil flow into oceans every year. Some of
this comes form oil tankers which are involved in
accidents. Sometimes, ships illegally wash
their empty tanks in the sea. In 1989, fifty million
litters of oil spilled in to the oceans. Much of this came
from a tanker called the Exxon Valdez' which was involved in an accident when oil was spilled off
the Alaskan coast. Millions of marine creatures died as a result. During the Gulf War in February
1991, Iraq set fire to more than 550 oil wells. This was an act of environmental

WATER 259
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

vandalism which future generation will have to pay for by way of polluted oceans.
Cities like Mumbai and Rio de Janeiro, which lie along the coast, often dump waste directly
into the sea. Many countries do not bother to treat or clean their sewage in any way but
allow it to flow untreated into the oceans.

? The saltiest seas are in the Middle East

where hot sun evaporates the water and
makes it saltier and saltier. The red sea is
so salty you cannot sink into it, the salt
keeps you floating.

? In July 1978, Walter Poenisch swam from Cuba, an island in the Caribbean Sea to Florida
in the U.S. The waters are so dangerous that he swam inside a shark cage and took just
over 34 hours to complete the 207 km journey.

WATER 260
 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

17 FORESTS: OUR LIFELINE

T
he word forest is derived from a Prof. Ahmad realized that the children
latin word foris which means “out had not visited a forest. The children also
of door". One evening Yasir wanted to know more about the forest, so
entered the park with an elderly person. they decided to visit it with Prof.Ahmad.
He introduced him to his friends. Prof.
Ahmad was a scientist working in the 17.1 Visit to a Forest
university. The children started playing One Sunday morning, the children
while Prof. Ahmad sat on the bench in packed a few things like a knife, a hand
the corner. He was tired as he had lens, a stick, a notebook and walked
participated in the golden jubilee together through a forest trail near a
celebrations of the town. After a while, the village. On their way, they met Ayman, a
children also came and sat around him. young boy of their age group, of a nearby
They wanted to know about the village, who was taking a cattle for
celebrations. Prof. Ahmad told them that grazing along with his aunt. He was very
after the cultural programme, the senior agile, running here and there to keep the
people discussed the town's herd together. When he saw the childern,
unemployment problem. A plan was Ayman also started walking along with
proposed to put up a factory by clearing them while his aunt went on a different
an area of the forest just outside the town. path. As soon as they entered the forest,
This would give the increasing population Ayman raised his hand and signalled
of the town a chance to get jobs. The them to keep quiet because noise could
children were very surprised when Prof. disturb the animals living in the forest .
Ahmad told them that many people had Ayman then took them to a place
objected to this idea. at a height to show them the broad view of
“This is because the forests serve the forest. Children were surprised
as green lungs and water purifying because they could not see any land
systems in nature”. Prof. Ahmad (Fig.17.1). The different treetops had
explained. The children were confused. formed green cover over the land.

FORESTS: OUR LIFELINE 261

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

However, the cover was not uniformly branches of the trees. Ayman told them to
green. The environment was peaceful relax since it was a normal phenomenon
and a cool breeze was blowing. This here. Because of the children's presence,
made the children quite fresh and happy. some monkeys had climbed higher up on
the trees where they disturbed the birds.
Animals often give this type of warning
call to alert other animals. Ayman also told
them that many other animals like boars,
bisons, jackals, porcupines and
elephants live in the deeper areas of the
forest (Fig .17.2). Prof. Ahmad cautioned
children that they should not go deep into
Fig.17.1 : A view of a forest the forest.

While coming down, they got Yasir and Saba remembered that
excited on hearing a sudden sound of they have studied about forest as an
birds and some noise from the top example of a habitat (Fig. 17.3). They

Fig.17.2 : Some forest animals

FORESTS: OUR LIFELINE 262

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

could see now how the forest provides a The land where the childern were
home for many animals and plants. walking was uneven and covered with
many trees. Ayman helped them to
identify sal, teak, semal, sheesham,
neem, palash, fig, khair, amla, bamboo,
kachnar (Fig 17.4). Prof. Ahmad pointed
out that there are several other trees,
shrubs, herbs and grasses in the forest .
The trees were also covered with different
types of creepers and climbers. The sun
was barely visible through the leaves of
the trees, making it quite dark inside the
forest.
Activity17.1
Observe the various things in your home
Fig.17.3 : Forest as habitat
and make a list of those which are made

Neem

Sheesham

Semal
Bamboo Fig17.4 : Some forest plants

FORESTS: OUR LIFELINE 263

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

from material which may have been

obtained from the forest.
The area under forest cover is 21% Honey

of the to tal a rea of I ndian

subcontinent. According to an
estimate, total area under forests in
Sealing wax Wooden
J&K is 20,230 sq. km i.e., 19.95% of statue
state area.

You might have many wooden

items on your list like plywood, fuel wood,
boxes, paper, matchsticks, and furniture.
Gum Catechu
Do you know that gum, oils, spices,
fodder for animals and medicinal plants Fig.17.5 : Forest products
are also some of the products which we Prof. Ahamd asked childern to look up
get from the forest (Fig.17.5). and observe how the branches of the tall
Saba wondered who would have trees look like a roof over the plants in the
planted these trees. Prof. Ahmed replied forest. He told them that this is called a
that in nature trees produce enough canopy (Fig.17.7).
seeds and the forest floor provides Activity17.2
favourable conditions for them to Visit a forest or a park in your
germinate and develop into seedlings and neighbourhood. Observe the trees and try
saplings. Some grow up into trees. He to identify them. You can take the help
added that branchy part of a tree above from some elder person or consult books
the stem is known as the crown of the on trees. List the characteristics of the
tree (Fig 17.6). trees that you observe, such as the

Fig.17.6 : Some crown shapes

FORESTS: OUR LIFELINE 264

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

height, shape of leaves, crown, flowers,

The forest of J&K grows numerous
and fruits. Also draw the crowns of some kinds of plants & trees. Some of them
trees. are : Pine, Deoder, Poplar, Fir, Chinar.
Prof. Ahmad pointed out that trees These provide excellent shelter to
had crowns of different types and sizes. various animal species such as Musk
These had created different horizontal Deer, Nilgai, Snow Leopards, etc.

layers in the forest. These are known as

understoreys (Fig.17.7). Gaint and tall A few children were busy watching
trees constituted the top layer followed by beautiful butterflies fluttering here and
shrubs and tall grasses, and herbs form there on the flowers of shrubs and herbs.
the lowest layer. They had a close look at the bushes.
“Would we see similar trees in While doing that their hair and clothes
every forest ?” asked Yasir. Prof. Ahmad had seeds and shrubs clinging to them.
said,"No, due to different climatic They came across numerous
conditions there are variations in the insects, spiders, squirrels, ants and
types of trees and other plants. The types various other small animals on the bark of
of animals also differ from forest to forest". the trees, plants leaves and on decaying
leaves of the forest floor (Fig.17.8).They
started making sketches of these

Canopy

Understorey

Fig.17.7 : Canopy and under storeys in a forest

FORESTS: OUR LIFELINE 265

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

creatures. The forest floor seemed dark like this. What difference will it make if we
coloured and was covered with a layer of cut some trees for a factory?”
dead and decaying leaves, fruits, seeds, Prof. Ahmed said, “You have read
twigs and small herbs. The decaying about autotrophs, heterotrophs and
matter was moist and warm. saprotrophs. You have learnt how green
plants produce food. All animals, whether
herbivorous or carnivores, depend
ultimately on plants for food. Organisms
which feed on plants often get eaten by
other organisms, and so on. For example,
grass is eaten by insects, which in turn, is
taken by the frog. The frog is consumed
by snakes. This is said to form a food
chain:
Fig.17.8 : Forest floor
Grass " insects" frogs " snakes " eagle.
Many food chains can be found in the
Children picked up various seeds
forest. All food chains are linked. If any
and leaves for their collection. Walking
one food chain is disturbed, it affects other
over the dead leafy layer on the forest
food chains. Every part of the forest is
floor was like walking over a spongy
inter-dependant on the other parts. If we
carpet!
Is the decaying matter always remove one component, say trees, all

warm? Prof. Ahmad suggested that the other components would be affected.”
Prof. Ahmad asked children to pick
children could perform an activity to get
up leaves from the forest floor and
an answer for this question.
observe them under a hand lens. They
Activity17.3
found tiny mushrooms over the decaying
Dig a small pit. Put vegetable waste and
leaves. They also saw an army of tiny
leaves in it. Cover it with soil. Add some
insects, millipedes, ants and beetles on
water. After three days, remove the upper
them. They were wondering how these
layer of the soil. Does the pit feel warm
organisms live there. Prof Ahmad
inside?
explained that apart from these animals
Saba asked. “ There are so many
which are easily seen, there are several
trees here. Also, there are many forests

FORESTS: OUR LIFELINE 266

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Oxygen
Carbon dioxide

Photosynthesis

Soil
Nutrients Decomposers Water

Fig.17.9 : Interrelationship of plant, soil and decomposers in a forest

organisms and micro- organisms that live some dead leaves and discovered under
in the soil. Saba wondered what them a layer of humus on forest floor. The
mushroom and other micro-organisms presence of humus ensures that the
eat. Prof. Ahmad replied that they feed nutrients of the dead plant and animals
upon the dead plants and animal tissues are released into the soil. From soil these
and convert them into a dark coloured nutrients are again absorbed by the roots
substance called humus. of the living plants. “What happens if an
You have learnt about humus in animal dies in the forest?" Sheila asked.
chapter 9. In which layer of the soil would Ayman replied that the dead animals
you find humus? What is its importance to become food for vultures, crows, jackals
the soil? and insects. In this way, the nutrients are
The micro- organisms which cycled. So, nothing goes waste in a forest
convert the dead plants and animals into (Fig. 17.9).
humus are known as decomposers. Saba reminded Prof. Ahmad that
These micro-organism play an important he had explained why forests are called
role in the forest. Soon, Saba removed

FORESTS: OUR LIFELINE 267

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

green lungs. Prof Ahmad explained that depend mostly on the forests. The forest
plants release oxygen through the provides them with food, shelter, water
process of photosynthesis. The plants and medicines. They have traditional
help to provide oxygen for animal knowledge about many medicinal plants
respiration. They also maintain the in the forest.
balance of oxygen and carbon dioxide in While Yasir was drinking water
the atmosphere (Fig 17.10). That is why from a small stream, he saw some deer
forests are called lungs. crossing the stream (Fig. 17.11). They
disappeared into the bushes. The dense
Saba reminded her bushes and the tall grasses provide
friends that they have animals with the food and shelter. They
studied photosynthesis in
also protect them from carnivores that live
Chapter 1.
in the forest.

O2

Plants Animals

CO2
Fig.17.10 : Balance of oxygen and carbon
dioxide

The children saw clouds forming in

the sky. Yasir recalled what he had learnt
about the water cycle in class VI. Trees
take in water from their roots and release
water vapour into the air through
Fig.17.11: Deer in a forest
evaporation.
If there were fewer trees, how will
the water cycle be affected?
Saba remembered that she
Ayman told them that the forest is
saw a Pipal sapling on the
not just home to plants and animals. Many sidewall in her school. Can you
people also live in the forest. Some of help her to understand how this
them may belong to different tribes. would have happened?

Ayman explained that these people

FORESTS: OUR LIFELINE 268

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Ayman then started looking closely at the After listening to this, Yasir noted in his
forest floor. Soon he called and showed notebook, “ By harbouring greater variety
the children droppings of some animals, of plants, the forest provides greater
and explained the difference between opportunities for food and habitat for the
various types of droppings. Prof. Ahmad herbivores. Larger number of herbivores
informed them that the forest officers means increased availability of food for a
could recognise the presence of some variety of carnivores. The wide variety of
animals in the forest by their dropping and animals help the forest to regenerate and
footprints. grow. Decomposers help in maintaining
Yasir called every one and showed them a the supply of nutrients to the growing
large, decaying heap of animal dropping. plants in the forest. Therefore, the forest is
Several beetles and grubs were feeding a ' dynamic living entity'- full of life and
on the heap and a bunch of seedlings vitality.”
which were sprouting. "These seedlings It was about afternoon and the
are of the herbs and shrubs. The animals children wanted to go back. Ayman
also disperse the seeds of certain plants suggested another route for going back .
and help the forest to grow and While they were going back, it started
regenerate. The decaying animal dung raining. However, surprisingly, they saw
also provides nutrients to the seedlings to that the raindrops were not hitting the
grow,” said Prof. Ahmad. forest floor directly . The uppermost layer
of the forest canopy intercepted the flow
of raindrops, and most of the water was
coming down through the branches and
the stems of the trees. From the leaves it
was dripping slowly over branches of the
shrubs and herbs (Fig.17.13). They found
that the ground was still dry. After about
half an hour, the rain stopped. They
noticed that the layer of dead leaves over
the forest floor appeared wet now. But
water did not stagnate in the forest.
Fig.17.12 : A sapling on a wall

FORESTS: OUR LIFELINE 269

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Rain
Transpiration and evaporation

The closed canopy and

many layers of vegetation
slow down the speed of
raindrops

Covered ground with

decaying material acts
Root system like a sponge

The root system helps

water to seep down in
the ground
Water table

Fig.17.13 : Rainwater drips from the trees and seeps into the ground

Yasir thought that if it had rained so year. Forests not only help in controlling
heavily in his town, it would have flooded floods but also help to maintain the flow of
the drains and roads.
water in the streams so that we get a
What would happen if it rains
heavily in your town? steady supply of water. On the other
Prof. Ahmad told them that the hand, if trees are not present, rain hits the
forest also acts as a natural absorber of ground directly and may flood the area
rainwater and allows it to seep. It helps to around it. Heavy rain may also damage
maintain the water table throughout the the soil. Roots of trees normally bind the

FORESTS: OUR LIFELINE 270

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

soil together, but in their absence the soil village is not regenerating and is on the

is washed away or eroded. verge of disappearing due to overgrazing

The children spent an hour at
of animals and indiscriminate felling of
Ayman's village on their way back. The
trees. Prof. Ahmad said that if we did
weather of the village was quite pleasant.
things wisely we could preserve forest
Villagers told them that due to the
and environment as well as have
surrounding forest, they receive good
development.
rainfall. The air also remained cool. Noise Children prepared a few pictures

pollution, too is less because the forest to show the consequences of such an

absorbs the noise of the nearby highway. event.

The children learnt about the At the end of the visit, Prof. Ahmad

history of the village. It surprised them asked children to sum up the importance

that the villages and the agricultural fields of forests. The children wrote: forests

of that area were created after clearing provide us oxygen. They protect the soil

the forest about sixty years ago. Ayman's and provide habitat to a large number of

grandfather told them that when he was animals. Forests help in bringing good

young, the village was not as large as it rainfall in the neighbouring areas. They

was now. It was also surrounded by are a source of medicinal plants, timber

forests. Construction of roads, building, and many other useful products. We must

industrial development and increasing preserve our forests.

demand of wood created pressure on the

forest and it started vanishing. He was not What would happen if forests
disappear ?
happy that the forest adjoining their

FORESTS: OUR LIFELINE 271

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

2 1. If forests disappear, the amount of

carbon dioxide in air will increase,
resulting in the increase of earth's
temperature.
2. In the absence of trees and plants, the
animals will not get food and shelter.
3. In the absence of trees, the soil will not
hold water, which will cause floods.
4. Deforestation will endanger our life and
environment. Think, what we can do to
preserve our forests.

3 4

FORESTS: OUR LIFELINE 272

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Canopy Deforestation Seed dispersal

Crown Humus Soil erosion

Decomposers Regeneration Understorey

What you have learnt

— We get various products from the forests surrounding us.
— Forest is a system comprising of various plants, animals and micro-organisms.
— In a forest, tree form the upper most layer, followed by shrubs. The herbs form
the lowest layer of the vegetation.
— Different layers of the vegetation provide food and shelter for animals, birds
and insects.
— The various components of the forest are interdependent on one another.
— The forest keeps growing and changing, and can regenerate.
— In the forest, there is an interaction between soil, water, air and living organisms.
— Forests protect the soil from erosion.
— Soil helps the soil to grow and regenerate.
— Forests are the life line for the forest-dwelling communities.
— Forests influence climate, water cycle and air quality.

EXERCISES
1. Explain how animals dwelling in the forest help it grow and regenerate.
2. Explain how forests prevent floods.
3. What are the decomposers? Name any two of them. What do they do in the
forest?
4. Explain the role of forest in maintaining the balance between oxygen and
carbon dioxide in the atmosphere.
5. Explain why there is no waste in a forest ?
6. List five products we get from forests ?

FORESTS: OUR LIFELINE 273

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

7. Fill in the blanks:

(a) The insects, butterflies, honeybees and birds help flowering plants
in_______________.
(b) A forest is a purifier of ___________ and __________.
(c) Herbs form the___________ layer in the forest.
(d) The decaying leaves and animal droppings in a forest enrich
the__________.
8. Why should we worry about the conditions and issues related to forests
far from us?
9. Explain why there is a need for variety of animals and plants in a forest.
10. In Fig 17.15, the artist has forgotten to put the labels and directions on the
arrows. Mark the directions on the arrows and label the diagram using
the following labels:
clouds, rain, atmosphere, carbon dioxide, oxygen, plants, animals, soil,
roots, water table.

Carbon dioxide

Oxygen

Fig. 17.15

FORESTS: OUR LIFELINE 274

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

11. Which of the following is not a forest product?

(i) Gum
(ii) Plywood
(iii) Sealing wax
(iv) Kerosene
12.Which of the following statements is not correct?
(i) Forests protect the soil from erosion.
(ii) Plants and animals in a forest are not dependent on one another.
(iii) Forests influence the climate and water cycle.
(iv) Soil helps forests to grow and re generate.
13. Micro-organism act upon the dead plants to produce?
(i) Sand (ii) Mushrooms (iii) Humus (iv) Wood
14. Tick mark ( ü) the correct choice
(1) Micro-organism which converts dead plants, animals into humus are
known as:-
(a) Decomposers (b) Omnivores
(c) Herbivores (d) Carnivores
(2) Which of the following is not a forest product?
(a) Plywood (b) Gum
(c) Teak (d) Gasoline
(3) Deforestation results in
(a) Increase in rainfall
(b) Global warming
(c) Increase in water level
(D) Conservation of soil
(4) A food chain includes :
(a) Producers and herbivores
(b) Producers and carnivores
(c) Producers and decomposers
(d) Producers, herbivores and carnivores

FORESTS: OUR LIFELINE 275

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Extended Learning - Activities and Projects

1. The department of environment is to decide whether some portion of a forest in
your area could be cleared for a housing complex. Write a letter to the
department explaining your point of view as a concerned citizen.
2. Visit a forest. Here is a list of points that would make your visit more fruitful.
(a) Make sure that you have permission to go in to the forest.
(b) Make sure that you can find your way around. Get a map and go
along with some one who is familiar with the area.
(c) Keep a record of things you see and do. Observations
make the visit interesting. Sketches and photographs are useful.
(d) You may record the bird calls.
(e) Collect different kinds of seeds or hard fruits like nuts.
(f) Try to recognize various types of trees, shrubs, herbs etc. Make a list of
plants from different places in the forest and of different layers. You
may not be able to name all the plants, but it is worth recording and seeing
where they grow. Make a record of approximate height of plants, crown
shape, bark texture, leaf size, and flower colour.
(g) Learn to recognise the animal's droppings.
(h) Interview the forest official and the people of surrounding villages and
other visitors.

You must never collect birds eggs, and their nest should never be
disturbed.
You can read more on the following website:
www.wild-india.com

FORESTS: OUR LIFELINE 276

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW?

In India the area under forest cover is about 21% of the total
area. It had steadily been falling since independence. But people now
seem to have realized the importance of the forest cover. Reports
suggest that the area under forest cover has slightly increased in
recent years.

FORESTS: OUR LIFELINE 277

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

18 WASTEWATER STORY

E xistence of life can not be

imagined without water. But
what we are doing with it. All of
us use water in our homes and make it
Clean water
put to use
dirty.
Dirty!Are you surprised?
Rich in lather, mixed with oil, black
Drinking
brown water that goes down the drains
from sinks, showers, toilets, laundries is
This accounts for a
dirty. It is called wastewater. Basically
l ar g e n u m b e r o f
used water is wastewater. This used
water-related
water should not be wasted. We must
diseases and even
clean it up by removing pollutants. Have WATER FOR LIFE
deaths. Women and 2005-2015
you ever thought where the wastewater
girls walk for several
goes and what happens to it?
kilometers to collect clean water, as you
18.1 WATER OUR LIFELINE have read earlier. Is it not a serious matter
Clean water is a basic need of for human dignity?
human beings. Let us make a mind-map You have already studied about
of the many uses of clean water. the increasing scarcity of fresh-water due
to population growth, population,
Activity 18.1 industrial development, mismanagement
(We have given one example of the use of and other factors. Realizing the urgency
clean water. You can add many more.) of the situation on the World Water Day,
Clean water that is fit for use is on 22 March 2005, the General Assembly
unfortunately not available to all. It has of the United Nations proclaimed the
been reported that more than one billion period 2005-2015 as the International
of our fellow human beings have no Decade for action on “ Water for life”. All
access to safe drinking water.

WASTEWATER STORY 278

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

efforts made during this decade aim to Locate an open drain near your
reduce by half the number of people who home, school or on the roadside and
do not have access to safe drinking water. inspect water flowing through it.
Cleaning of water is a process of Record colour, odour and any
removing pollutants before it enters a other observation. Discuss with your
water body or is reused. This process of friends and your teacher and fill up the
wastewater treatment is commonly following Table 18.1.
known as “Sewage Treatment". It takes We know that sewage is a complex
place in several stages mixture containing suspended solids,
organic and inorganic impurities,
18.2 WHAT IS SEWAGE? nutrients, saprophytic and disease
Sewage is wastewater released by causing bacteria and other microbes.
homes, industries, hospitals, offices and Organic impurities - Human faeces,
other uses. It also includes rainwater that animal waste,
has run down the street during a storm or oil, urea (urine),
heavy rain. The water that washes off pesticides,
herbicides, fruit
roads and rooftops carries harmful
and vegetable
substances with it. Sewage is a liquid
waste, etc.
waste. Most of it is water, which has Inorganic impurities - Nitrates,
dissolved and suspended impurities. Phosphates,
These impurities are called metals.
contaminants. Nutrients - Phosphorous
and Nitrogen.
Bacteria - Such as which
Activity 18.2
cause cholera

Table 18.1: Contaminant survey

S.No. Type of sewage Point of origin Substances which Any other
contaminate remark
1 Sullage water Kitchen
2 Foul waste Toilets
3 Trade waste Industrial
and commercial
organizations

WASTEWATER STORY 279

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

and typhoid. living organisms are found in and

Other microbes - Such as which around it.
cause dysentery. In case you do not have a sewerage
system in your locality, find out how
sewage is being disposed off.
18.3 Water Freshens Up - An
Eventful Journey
In a home or a public building 18.4 TREATMENT OF
generally one set of pipe brings clean
POLLUTED WATER
water and another set of pipes takes away
Perform the following activity. It will
wastewater. Imagine that if we could see
help you understand the processes that
through the ground. We would see a
take place at the wastewater treatment
network of big and small pipes, called
plant.
sewers, forming the sewerage. It is like a
transport system that carries sewage
from the point of being produced to the Activity 18.4
point of disposal, i.e. treatment plant. Divide the class into groups to perform the
Manholes are located at every
activity. Record observation at each
50m to 60m in the sewage, at the junction
stage:
of two or more sewers and at points where
ê Fill a large glass jar ¾ full of
there is a change in direction.
water. Add some dirty organic
matter such as grass pieces or
Activity 18.3
orange peels, a small amount of
Study the sewage route in your
detergent, and a few drops of an
home/school/building. Do the following:
ink or any color.
? Make a line diagram of the
ê Cap the jar, shake it well and let the
sewage route.
mixture stand in the sun for two
? Walk down the street or survey days.
the campus to find the number of
ê After two days, shake the mixture
manholes.
and pour a small sample into the
? Follow an open drain and find out test tube. Label this test tube
where it ends and which

WASTEWATER STORY 280

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

“Before treatment; Sample 1”. ê Pour a sample of the filtered water

How does it smell? into a third test tube labelled
ê Use an aerator from an aquarium to “Filtered; Sample 3”.
bubble air through the sample in the ê Pour another sample of the filtered
glass jar. Allow several hours for water into a fourth test tube. Add a
aeration; leave the aerator attached small piece of a chlorine tablet. Mix
overnight. If you do not have an well until the water is clear. Label the
aerator, use a mechanical stirrer or a test tube “Chlorinated; Sample 4”.
mixer. You may have to stir it several ê Observe carefully the samples in all
times. the test tubes. Do not taste! Just
ê The next day when aeration is smell them!
complete, pour another sample
into a second test tube. Label it as
“After aeration; Sample 2”
ê Fold a piece of filter paper to from
a cone. Wet the paper with tap
water and then insert the cone in a
funnel. Mount the funnel on a
support.
ê Place layers of sand, fine gravel and
finally medium gravel in the funnel
(Fig.18.2). (An actual filtration plant
does not use filter paper, but the Fig.18.2 : Filtration process

sand filter is several metres deep).

Now answer the following questions:
ê Pour the remaining aerated liquid (a) What changes did you observe in the
through the filter into the beakers. appearance of the liquid after
Do not allow the liquid to spill over aeration?
the filter. If the filtered liquid is not (b) Did aeration change the odour?
clear, filter it a few times till you get (c) What was removed by the sand filter?
clear water. (d) Did chlorine remove the color?
(e) Did chlorine have an odour?

WASTEWATER STORY 281

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

(f) Was it worse than that of the

wastewater?

18. 5 WASTEWATER TREATMENT

PLANT (WWTP)
Treatment of wastewater involves
physical, chemical and biological
processes, which remove physical,
Fig.18.4 Grit and sand removal tank
chemical and biological matter that
3. The water is then allowed to settle in
contaminates the wastewater.
1. Wastewater is passed through bar a large tank which is sloped towards

screens. Large objects like rags, the middle. Solids like faeces settle at

sticks, cans, plastic packets, napkins the bottom and are removed with a

are removed (Fig. 18.3) scraper. This is the sludge. A

skimmer removes the floatable solids
like oil and grease. Water so cleared
is called clarified water (Fig. 18.5).

Fig.18.5 : Water clarifier

The sludge is transferred to a separate
Fig.18.3 : Bar screen
tank where it is decomposed by the
2. Water then goes to a grit and sand
anaerobic bacteria. The biogas
removal tank. The speed of the
produced in the process can be used
incoming wastewater is decreased to
as fuel or can be used to produce
allow sand, grit and pebbles to settle
electricity.
down (Fig 18.4).

WASTEWATER STORY 282

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Shrinking Dal lake The present water. The water is removed by sand
condition of the world famous Dal lake drying beds or machines. Dried sludge is
is a matter of great concern as the lake is used as manure, returning organic matter
shrinking at a very fast rate. Amongst and nutrients to the soil.
the problems responsible for The treated water has a very low level
deterioration of Dal lake, the prominent of organic material and suspended
are heavy sanitation, urbanization, over matter. It is discharged into a sea, a river
exploitation, over grazing, weed or into the ground. Nature cleans it up
growth, loss of biodiversity etc. The further. Sometimes it may be necessary
status report of J&K LAWDA (Lakes to disinfect water with chemicals like
& Waterways Development Authority) chlorine and ozone before releasing it into
reports an annual silt deposition of the distribution system.
40,000 cubic meters. Become an active citizen
Waste generation is a natural part
4. Air is pumped into the clarified water to of human activity. But we can limit the type
help aerobic bacteria to grow. Bacteria of waste and quantity of waste produced.
consume human waste, food waste, Often we have been repelled by offensive
soaps and other unwanted matter still smell. The sight of open drains is
remaining in clarified water (FIg. 18.6) disgusting. The situation worsens in the
rai ny seaso n when drai ns start
overflowing. We have to wade through the
mud pools on the roads. Most unhygienic
and unsanitary conditions prevail during
this time. Flies, mosquitoes and other
i n s e cts breed in it.

Fig.18.6 : Aerator

After several hours, the suspended The water in a river is cleaned

naturally by processes that are
microbes settle at the bottom of the tank similar to those adopted in a
as activated sludge. The water is then wastewater treatment plant.

removed from the top.

The activated sludge is about 97%

WASTEWATER STORY 283

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

DO YOU KNOW? (iii) L a r g e scale illegal

It has been suggested that we should encroachment
plant eucalyptus trees all along sewage (iv) 80% of the lake was seen under
ponds. These trees absorb all surplus the thick blanket of weed.
wastewater rapidly and release pure
Tawi river is a major left bank
water vapour into the atmosphere.
tributary of river chenab flowing through

You can be an enlightened citizen the city of Jammu. Waste water from 12
nallahs as well as other waste of
and approach the municipality or the
Jammu city are discharged into it
gram panchayat. Insist that the open
without any treatment .
drains be covered. If the sewage of any
particular house makes the Jhelum River Conservation Plan

neighbourhood dirty, you should request (JRCP) for Jammu and Kashmir State is

them to be more considerate about formulated under the National River

others' health. Conservation Plan (NRCP) of the

Ministry of Environment (MOE), Govt. of
India (GOI). The four towns, namely
Anantnag, Srinagar, Sopore and
Don't add to the load of Baramulla in Jammu and Kashmir State
WWTP. Saba wonders how! have been identified as contributing
pollution to river Jhelum and are
therefore covered under Jhelum River
Mansabal lake is located in the Jhelum
Conservation Plan.
valley and is encircled by three villages
viz., Jarokbal, Kondabal and Ganderbal
18.6 BETTER HOUSE KEEPING
and is stated to be the deepest lake in the PRACTICES
Kashmir valley. World Wide Fund for
One of the ways to minimize or
Nature (WWF) conducted an extensive
eliminate waste and pollutants at their
survey of the lake in 1997 and gave
source is to see what you are releasing
following reasons for its deterioration.
down the drain.
(i) The flow of sewage
P Cooking oil and fats should not be
(ii) Siltation
thrown down the drain. They can

WASTEWATER STORY 284

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

harden and block the pipes. In an These wastes choke the drains.
open drain the fats clog the soil They do not allow free flow of oxygen.
pores reducing its effectiveness in This hampers the degradation process.
filtering water. Throw oil and fats in
the dustbin. 18.7 SANITATION AND DISEASE
P Chemicals like paints, solvents, Poor sanitation and contaminated
insecticides, motor oil, medicines drinking water is the cause of a large
may kill microbes that help purify number of diseases.
water. So do not throw them down Let us look at our own country. A
the drain. vast number of our people are still without

P Used tea leaves, solid food sewerage facilities. Where do they relieve

remains, soft toys, cotton, sanitary themselves?

A very large fraction of our people
towels, etc. should also be thrown in
defecate in the open, on dry riverbeds, on
the dustbin (Fig. 18.7).
railway tracks, near fields and many a
times directly in water. Untreated human
excreta are a health hazard. It may cause
water pollution and soil pollution. Both the
surface water and groundwater get
polluted. Groundwater is a source of
water for wells, tube wells, springs and
many rivers. Thus, it becomes the most
common route for water borne diseases.
They include cholera, typhoid, polio,
meningitis, hepatitis and dysentery.

18.8 ALTERNATIVE ARRANGEMENT

FOR SEWAGE DISPOSAL
To improve sanitation, low cost
onsite sewage disposal systems are
being encouraged. Examples are septic

Fig.18.7 : Do not throw everything in the sink tanks, chemical toilets, composting pits.

WASTEWATER STORY 285

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Septic tanks are suitable for places where It must be disposed off properly otherwise
there is no sewerage system, for epidemics could break out.
hospitals, isolated buildings or a cluster of The government has laid down
4 to 5 houses. certain standards of sanitation but,
unfortunately, they are not strictly
enforced.
However, all of us can contribute in
maintaining sanitation at public places.
Yasir wants to know how
We should not scatter litter anywhere. If
sewage is disposed of in an
aeroplane. there is no dustbin in sight, we should
carry the litter home and throw it in the
dustbin.
Some organization offer hygienic on-
site human waste disposal technology. Conclusion
These toilets do not require scavenging. We all have a role to play in

Excreta from the toilet seats flow through keeping our environment clean and

covered drains into a biogas plant. The h ea l t h y. Yo u m u s t r e a l i z e y o u r

biogas produced is used as a source of responsibility in maintaining the water

energy. sources in a healthy state. Adopting good

sanitation practices should be our way of
18.9 SANITATION AT PUBLIC PLACES life. As an agent of change your individual
In our country fairs are organized initiative will make a great difference.
periodically. A large number of people Influence others with your energy, ideas
participate in them. In the same way and optimism. A lot can be done if people
railway stations, bus depots, airports, work together. There is great power in
hospitals are very busy places. collective action.
Thousands of people visit them daily.
Large amount of waste is generated here.

WASTEWATER STORY 286

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Aeration Contaminant Sewerage

Aerobic bacteria Sanitation Sludge
Anaerobic bacteria Sewage Wastewater
Biogas Sewer

What you have learnt

o Used water is wastewater, Wastewater could be rescued.
o Wastewater is generated in homes, industries, agricultural fields and in other human activities.
This is called sewage.
o Sewage is a liquid waste which causes water and soil pollution
o Wastewater is treated in a sewage treatment plant.
o Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.
o Where underground sewerage systems and refuse disposal systems are not available, the
low cost on-site sanitation system can be adopted.
o By-products of wastewater treatment are sludge and biogas.
o Open drain system is a breeding place for flies, mosquitoes and organisms which cause
diseases.
o We should not defecate in the open. It is possible to have safe disposal of excreta by low cost
methods.

EXERCISES
1. Fill in the blanks:
(a) Cleaning of water is a process of removing ___________ .
(b) Wastewater released by houses is called ___________ .
(c) Dried ___________ is used as manure.
(d) Drains get blocked by ___________ and ___________ .
2. Water is sewage? Explain why it is harmful to discharge untreated sewage into rivers or
seas.
3. Why should oils and fats not be released in the drains? Explain.
4. Describe the steps involved in getting clarified water from waste water.
5. What is sludge? Explain how it is treated.
6. Untreated human excreta is a health hazard. Explain.
7. Name two chemicals used to disinfect water.

WASTEWATER STORY 287

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

8. Explain the function of bar screens in a wastewater treatment plant.

9. Explain the relationship between sanitation and disease.
10. Outline your role as an active citizen in relation to sanitation.

11. Here is a crossword puzzle: Good Luck!

Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from the human body.
Down
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water.

WASTEWATER STORY 288

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

12. Study the following statements about ozone.

(a) It is essential for breathing of living organisms.
(b) It is used to disinfect water.
( c) It absorbs ultraviolet rays.
(d) Its proportion in air is about 3%.
Which of these statements are correct?
(i) (a), (b) and (c)
(ii) (b) and (c)
(iii) (a) and (d)
(iv) All four
13. Tick mark (ü) the correct answers.
1. The disease caused by polluted water
(a) Jaundice (b) Dysentery
(c) Cholera (d) All of these
2. Malaria can be triggered by
(a) Open drains (b) Closed drains
(c) Taps (d) Pipe lines
3. Waste that can be broken down by bacteria
(a) Biological (b) Biochemical
(c) Biodegradable (d) Chemical
4. Stage of wastewater treatment for removing large particles
(a) Disinfection (b) Secondary
(c) Primary (d) Chlorination

Extending Learning - Activities and Projects

1. Construct a crossword puzzle of your own using the keywords.
2. Then and now: Talk to your grandparents and other elderly people in the
neighbourhood. Find out the sewage disposal systems available to them. You can also
write letters to people living in far off places to get more information. Prepare a brief
report on the information you collect.
3. Visit a sewage treatment plant.
It could be as exciting and enriching as a visit to a zoo, a museum, or a park. To guide
your observation here are a few suggestions.
Record in your notepad.
Place ____________ Date ____________ Time ____________

WASTEWATER STORY 289

 JAMMU AND KASHMIR STATE BOARD OF SCHOOL EDUCATION

Name of the official at the plant ____________ Guide/Teacher ____________

(a) The location of the sewage plant.
(b) Treatment capacity.
(c) The purpose of screening as the initial process.
(d) How is air bubbled through the aeration tank?
(e) How safe is the water at the end of the treatment? How is it tested?
(f) Where is the water discharged after treatment?
(g) What happens to the plant during heavy rains?
(h) Is biogas consumed within the plant or sold to other consumers?
(i) What happens to the treated sludge?
(j) Is there any special effort to protect nearby houses from the plant?
(k) Other observations.
For more information, consult:
Millennium Development Goals:
http” // www.un.org/millenniumgoals/
“water for life” International Decade for Action:
http”// www.un.org/waterforlifedecade/:
World Water Day Themes and Importance.
http// www.worldwaterday.org/
Through the ages Development of Sanitation:
http” // www.cep.unep.org/pubs/techreports/tr43en/Household%
20Systems. htm.

“By providing clean water and sanitation to the poorest people on the
planet, we can reduce poverty and suffering and ensure education for all
children”. -UNICEF

An early engineering feat: Indus valley civilization

One of the ancient civilizations, Harappa and Mohenjodaro had perhaps the
world's first urban sanitation system. Within the city individual houses, or
groups of houses, obtained water from wells. There was a separate room for
bathing, and wastewater was directed to the covered drains which lined the
major streets. The oldest toilet made of bricks is about 4500 years old.

WASTEWATER STORY 290