The
Science Hub
TEACHER’S MANUAL
Class 7
Shalini Samadhiya
MSc MEd
(An imprint of New Saraswati House (India) Pvt. Ltd.)
New Delhi-110002 (INDIA)
R
(An imprint of New Saraswati House (India) Pvt. Ltd.)
First published 2016
ISBN: 978-93-5199-718-4
Preface
The purpose of The Science Hub series (1 to 8) teacher’s resource pack is to empower teachers to
make classroom teaching a holistic experience. It will enable teachers to explain the chapters in the
most effective way, which will not only impart knowledge, but also ignite interest in the minds of
young learners towards the subject. A wide array of resources complement these manuals, which
makes learning an interesting process instead of a routine chore.
Teacher’s Manual
Teacher’s Manual resources have been carefully prepared with an aim to make the process of
teaching and learning interesting and intriguing for the teachers and learners alike. It comprises
detailed lesson plans and answers to the coursebook along with solved worksheets and model test
papers. These have been prepared keeping in mind the explanation of the concepts and the level
appropriateness of the topics. Easily available teaching aids are used to make teaching and learning
an interactive and lucid process.
The lesson plans give a topic-wise explanation of each chapter. Its components are:
• Warm up section guides the teacher to start the topic in an interesting way.
• Specific learning objectives give the list of measurable aims of each chapter, which should be
achieved after teaching the chapter.
• Concept explanation gives a detailed method of explaining the important concepts of the
chapter using various teaching aids.
• Reinforce section allows the teacher to check the progress of the concepts learned by the
students with the help of textual questions and worksheets and allows them to revisit and
revise the concepts, if required.
• Explore section helps the learners to do various activities, often taking them beyond their
classroom learning.
Teacher’s CD
Teacher’s CD comprises animations, activities, flip book, detailed lesson plans and answers to the
coursebook along with solved worksheets and model test papers.
Web Support
The web support consists of worksheets, model test papers, and answers to worksheets and model
test papers. These would help teachers in assessing students on the concepts taught in the class.
Contents
S.No.
Chapters
Pages
1.
Nutrition in Plants
5
2.
Nutrition in Animals
11
3.
Fibre to Fabric
19
4.
Chemicals and Chemical Changes
25
5.
Temperature and Heat
32
6.
Acids, Bases and Salts
38
7.
Climate and Adaptations
44
8.
Soil
51
9.
Respiration
59
10.
Transport of Substances in Animals and Plants
66
11.
Reproduction in Plants
73
• Model Test Paper 1
82
12.
Time and Motion
84
13.
Electric Current and Circuits
90
14.
Wind, Storm and Cyclone
95
15.
Light
102
16.
Water: An Important Resource
108
17.
Forests: Our Lifeline
114
18.
Wastewater Management
120
• Model Test Paper 2
129
Chapter 1
Nutrition in Plants
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• know what is nutrition
• know about different types of nutrition such as autotrophic and heterotrophic nutrition
• know about different types of heterotrophic types of nutrition
• understand about the replenishment of nutrients in the soil
Warm Up
The topic can be started by asking simply about what is nutrition. What do students understand by
the term nutrients? Tell students to read the Warm-up section very carefully and answer it. Explain
to them why adding manure and watering plants are important. Tell students to look around and
observe how different plants get their nutrition.
Concept Explanation
• Autotrophic nutrition: Plants are the only living things that make their own food by the
process of photosynthesis. This types of nutrition found in green plants is termed autotropic
nutrition. Ask students about photosynthesis. Explain its process with the help of Activity 1
given on page 9.
• Heterotrophic nutrition: The plants which derive their nutrition from other plants are
called heterotrophs. Heterotrophic plants are of four types, namely, saprophytic, parasitic,
insectivorous and symbiotic plants.
• Saprophytic plants: Tell students that some plants derive their nutrition from dead and
decayed plants and animals such as Indian pipe. Ask students that have they ever seen white
powdered form on the bread. This is fungus which also shows saprophytic nutrition.
• Parasitic plants: Explain such plants with the help of cuscuta plant. Tell students in this
relationship, one plant is the host while the other is the parasite.
• Insectivorous plants: Insectivorous plants get nutrition by trapping and consuming insects.
Pitcher plant is the best example of this category.
• Symbiotic plants: Tell students that in a symbiotic relationship, both the organisms benefit
from each other lichens are symbiotic plants consisting of algae and fungi.
5
• Replenishment of nutrients in the soil: Tell students that plants get their nutrients from the
soil with the help of roots. So, how do these nutrients get replenished in the soil? Tell them
that using manure and fertilisers maintain the level of nutrients in the soil.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
6
Worksheet 1
1. Identify the mode of nutrition in the given plants.
(a)
_________________________
(b)
_________________________
(c)
_________________________
(d)
_________________________
(e)
_________________________
7
Worksheet 2
1. Define the following.
(a) Saprophytic plants
__________________________________________________________
__________________________________________________________
(b) Symbiosis
__________________________________________________________
__________________________________________________________
(c) Stomata
__________________________________________________________
__________________________________________________________
(d) Heterotrophs
__________________________________________________________
__________________________________________________________
(e) Haustoria
__________________________________________________________
__________________________________________________________
(f) Xylem
__________________________________________________________
__________________________________________________________
8
Answers to Coursebook
A.
B.
C.
1. Phloem-Starch
Xylem- Water
Symbiosis-Lichen
Saprotroph- Coral root
2. (a) Drosera, Bladerwort
(b) Autotrophic, heterotrophic
(c) Green plants, Some bacteria
(d) Cuscuta, Misteloe
3. (a) Chlorophyll
(b) Symbiosis
(c) Xylem
(d) Saprophytes
1. The process in which green plants make their food by using substances such as carbon dioxide,
water and minerals.
6CO2 + 6H2O  C6H12O6 + 6O2
2. Photosynthesis is affected by light intensity, availability of carbon dioxide, water.
3. The mode of nutrition in which two different organisms of different species live together and both
are benefited from each other.
4. If we do not destarch the leaf then the test will not be positive.
5. Its roots are called haustoria which pierce the host’s body to obtain nutrition.
6. Tiny pores (stomata) are generally found on the underneath of leaves.
7. The plants which derive their food from the dead and decaying plants and animals.
8. (a) Autotrophic (auto–self; trophe–nutrition) nutrition is the mode of nutrition in which an
organism uses inorganic substances such as carbon dioxide, water and minerals to make its own
food. The mode of nutrition in which an organism cannot make its own food and depends on
other organisms for food is called heterotrophic (hetero–different; trophe–nutrition) nutrition.
(b) The plants that derive some or most of their nutrients by trapping and consuming insects are
called insectivorous plants. Plants which depend partially or completely on other plants for
their food and shelter are called parasitic plants.
(c) Xylem carries water and nutrients from the roots to the leaves. Pholem carries food prepared
by the leaves to all parts of the plants.
1. Hetrotrophic plants are of the following types.
Saprophytic plants: The plants which derive their food from dead and decaying plants and
animals are called saprophytes (Sapro–rotting; phyton–plant) and their mode of nutrition is called
saprophytic. Examples of such plants are Indian pipe, coral root and some varieties of orchids.
Parasitic plants: Plants which depend partially or completely on other plants for their food and
shelter are called parasitic plants; for example, cuscuta (dodder) and mistletoe.
Insectivorous plants: The plants that derive some or most of their nutrients by trapping and
consuming insects are called insectivorous plants. Some examples of insectivorous plants are the
pitcher plant, Drosera (sundew), bladderwort and the Venus flytrap.
Symbiotic plants: The mode of nutrition in which two different organisms of different species live
together and both are benefited from each other is called symbiotic (sym–together; bios–life). For
example, lichens are symbiotic plants.
2. The leaves of nepenthes (pitcher plant) are modified into a tubular pitcher-like structure. The apex
of the leaf forms a lid over the pitcher, which can be opened or closed. The inner surface of the
pitcher has hair directed downwards. When an insect enters the pitcher, the lid closes and the
9
3.
4.
D.
E.
1.
2.
3.
insect gets trapped inside the pitcher. The insect gets digested by the digestive juices secreted in the
pitcher.
Refer to Figure 1.2 on page 9
The mode of nutrition in which two different organisms of different species live together and
both are benefited from each other is called symbiotic (sym–together; bios–life). For example,
lichens are symbiotic plants. Lichen is an association between green algae (chlorophyll containing
organisms) and fungi. Algae being autotrophic, manufacture their own food and supply food to
the fungi. In turn, fungi, being saprophytic, provide water, minerals and shelter to the algae. This
association allows them to survive in harsh conditions. They are unable to live individually.
Refer to Figure 1.2 on page 9
If we coat a leaf with wax, then exchange of gases and water vapour will not occur and ultimately
the leaf will die.
They have chlorophyll so they make their own food but to get nutrients they eat insects.
Because animals don't have chloroplasts in their cells like plants have.
Answers to Worksheets
Worksheet 1
1. (a) Parasitic
(b) Saprophytic
(c) Symbiotic
(d) Insectivorous
(e) Insectivorous
Worksheet 2
1. (a) The plants which derive their food from dead and decaying plants and animals. For example, Indian
pipe
(b) The relationship in which two different organisms of different species live together and both are
benefited from each other. Example, Lichen
(c) Tiny pores present on the underneath of the leaf which help in gaseous exchange.
(d) Animals and non-green plants that cannot make their food and depend on other organisms for
food.
(e) Roots of Cuscuta plant are called haustoria that pierce the host’s body to obtain nutrition.
(f) Thin tube-like structures that carry water and nutrients from the roots to leaves and all parts of the
plant.
10
Chapter 2
Nutrition in Animals
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• know about nutrition in different types of animals
• know the process of digestion in humans
• know what are the different parts present in the alimentary canal, and what are their functions
• find out the number and nature of different types of teeth in our mouth
• spread awareness about the type of food we eat and how it is useful to us
• know about the digestive system of ruminants.
Warm Up
The topic can be started by giving examples of how on seeing food your mouth waters and further
by asking why do we eat food. What happens when you see or smell pizza, pasta or samosa? What
is saliva made up of? Why our mouth waters on seeing food? Amoeba does not have a mouth, then
how digestion takes place in its body? With the help of the Warm-up section, one can explain how
different animals feed on different types of food items to derive energy for their normal body functioning.
Concept Explanation
• Nutrition: What does the term nutrition mean? Explain how digestion of food takes place in
your body.
• Human teeth: Why are different types of teeth present in your mouth? What is the function
of tongue? What preventive measures should we take to maintain good dental hygiene?
With the help of a model of teeth, their shape and function can be explained. Correct method
of brushing teeth can be demonstrated with the help of a tooth brush.
• Digestion: Why should we be careful about the type of food we eat? Digestion of food
starts from mouth. Oesophagus functions as a connection between mouth and stomach. In
stomach, why HCl is secreted. How is HCl useful to us? Why small intestine does not have
villi? Why is large intestine smaller in length?
Demonstrating Experiment 1 will be helpful for students to understand the importance of
saliva.
11
• Ruminants: Why do cows or buffaloes keep on chewing their food? With the help of the
digestive system chart (of ruminants),this can be explained.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
12
Worksheet 1
1. Label the given diagram.
(a)
(b)
(c)
(d)
(e)
2. Fill in the blanks.
(a) The process of taking food into the body is called __________.
(b) __________ kills bacteria that enters the stomach.
(c) ____________ and ___________ secrete digestive juices.
(d) The shape of the stomach is ___________.
(e) The __________ protects the lining of the stomach.
3. Which part of the digestive canal is involved in the following processes?
(a) Absorption of nutrients from food
_______________
(b) Chewing of food
_______________
(c) Absorption of water
_______________
(d) Formation of faeces
_______________
(e) Killing of bacteria
_______________
13
Worksheet 2
1. Answer the following questions.
(a) What are ruminants?
____________________________________________________________
____________________________________________________________
(b) Why are they called so?
____________________________________________________________
____________________________________________________________
2. Give one word for the following.
(a) The grass is rich in it.
_________
(b) The food in amoeba is digested in it.
_________
(c) The process of utilisation of nutrients by the body cells.
_________
(d) Thick muscular organ which makes the floor of the mouth.
_________
3. Match the following.
14
Column A
Column B
Cud
Large intestine
Villi
Ruminants
Egestion
Saliva
Rectum
Anus
Salivary gland
Small intestine
Answers to Coursebook
A.
1. (a) F
(b) F
(c) F
(d) T
(e) T
2. Stomach—Pancreatic juice
Muscular organ used to taste food—Tongue
Finger-like projections on the lining of the small intestine—Villi
Amoeba—Pseudopodia
Ruminants—Omasum
B.
1. The main steps involved in the process of nutrition are ingestion, digestion, absorption, assimilation
and egestion.
2. We should brush our teeth to remove this plaque otherwise this plaque produces acid which
dissolves the tooth enamel which causes pain, discomfort, and in severe cases, the tooth may have
to be removed.
3. Assimilation: The process by which the absorbed food is used for producing energy required for
growth is called assimilation.
Rumination: A ruminant is a plant-eating animal that brings back swallowed food into the mouth
to chew it again. This process is called rumination.
4. Teeth help us in breaking down the food into smaller pieces.
5. The oesophagus leads into the stomach which has four chambers: rumen, reticulum, omasum and
abomasum.
6. (a) Premolars: These are broad and rectangular teeth which have a humped surface. They help in
grinding food.
Molars: These are large back teeth. These teeth have a flat surface with small ridges. They help
in grinding food.
(b) Ingestion: The act of taking in food is called ingestion.
Egestion: The process by which the undigested food is thrown out of the body is called egestion.
(c) Milk teeth: The temporary set has 20 teeth and these teeth are also called the milk teeth.
Around the age of six, milk teeth start falling out.
Permanent teeth: In the permanent set, there are 32 teeth, 16 in each jaw.
(d) Absorption: The simple substances produced by the process of digestion are passed to the
blood which transports these to different parts of the body. These soluble substances are
absorbed by the cells of the body.
Assimilation: The process by which the absorbed food is used for producing energy required
for growth is called assimilation. This process takes place in the cells of living beings where
simple substances are used to make complex substances.
C.
1. Digestion: In human beings, the process of digestion is carried out inside a long tube which
is coiled in some places. It is called the gut or alimentary canal. The alimentary canal is about
7.5 metre long and stretches from the mouth to the anus. The process of digestion involves many
organs and different steps.
15
Mouth: The digestion of food starts in the mouth. The food is broken down into smaller pieces by
chewing. The tongue mixes the food well with a liquid called saliva which is secreted by the salivary
glands.
Oesophagus: After the food is swallowed, it passes through a tube-like structure that carries the
food from the mouth to the stomach, called oesophagus. The walls of the oesophagus contract and
relax to produce wave-like movements (called peristaltic movements) which help to move the food
down into a large sac-like muscular structure called the stomach.
Stomach: Further digestion of the food takes place in the stomach. The inner wall of the stomach
secretes digestive juices, hydrochloric acid and mucus. The digestive juices help to break down the
proteins into simpler forms.
Small intestine: From the stomach, the semi-digested food which is called chyme passes into the
small intestine. The useful nutrients of the food get absorbed into the blood, which takes these
nutrients to all parts of the body. Liver, gall bladder and pancreas help in the digestion of the food
in the small intestine.
Liver: It secretes bile which helps in the digestion of fats.
Gall bladder: Bile is stored in the gall bladder before being released into the small intestine.
Pancreas: The secretions of pancreas help in the breakdown of carbohydrate into sugars, proteins
into amino acids and fats into fatty acids and glycerol.
Large intestine: In the large intestine, the water is absorbed from the undigested food.
Absorption: The inner wall of the small intestine is covered with millions of finger-like tiny
projections called villi (singular: villus). These villi increase the surface area for absorption. Villi
are richly supplied with blood vessels. The digested food passes through the thin walls of these
vessels and enters the blood stream. The chyme now passes into the large intestine, where water
and minerals are absorbed.
2. Refer the answer of Question C–1
3. Food is taken into the body through the mouth and is chewed with the help of teeth. Teeth help us
in breaking down the food into smaller pieces. In the permanent set, there are 32 teeth, 16 in each
jaw. There are 4 incisors, 2 canines, 4 premolars and 6 molars in each jaw.
Incisors: These are so named because they help to incise (cut) food. They are flat, blade-like front
teeth which are present in both the jaws. These are chisel-shaped and help in biting and cutting
food, and therefore, also known as biting teeth.
Canines: These are present on either side of the incisors. They are sharp, pointed and used for
tearing food, and therefore, also known as tearing teeth.
Premolars: These are broad and rectangular teeth which have a humped surface. They help in
grinding food.
Molars: These are large back teeth. These teeth have a flat surface with small ridges. They help in
grinding food.
16
4. Digestion in ruminents: After chewing the food, the food passes down the oesophagus which is 2
to 3 feet long. The oesophagus leads into the stomach which has four chambers: rumen, reticulum,
omasum and abomasum.
Rumen: The rumen helps in storing large quantities of food which is partially digested here and is
now called the cud. This cud is then brought back to the mouth, re-chewed and re-swallowed. This
process is called cud-chewing. The millions of bacteria and protozoa present in the rumen break
down the carbohydrates (cellulose) found in hay and grass.
Reticulum: This part helps in the movement of swallowed food back into the mouth for further
chewing. The reticulum opens into the omasum.
Omasum: This part absorbs the excess water.
Abomasum: The walls of the abomasum secrete digestive juices.
5.
D.
E.
1.
2.
3.
In ruminants, the digested food is brought back to the mouth, re-chewed and re-swallowed while
this is not found in humans.
Amoeba is a unicellular microorganism found in ponds, pools and ditches. Its body is covered
by a thin membrane. It has a dense nucleus and small vacuoles in its cytoplasm. Amoeba has
an irregular shape which keeps changing slowly. It has finger-like projections called pseudopodia
(pseudo–false; podium–foot). When Amoeba comes in contact with food particles, it stretches out
its pseudopodia and engulfs the tiny particles. The pseudopodia close to form a cavity called food
vacuole. The food vacuole moves in the cytoplasm where digestive juices are added to it and the
digestive enzymes break down the food into simple and soluble substances. These substances are
absorbed into the cytoplasm and utilised for the growth, development and release of energy in the
Amoeba. The undigested food is expelled out through the cell membrane.
Refer to Figure 2.1 on page 22
Refer to Figure 2.3 on page 24 and for functions refer answer of C–1
If sportsperson eat heavy meal before playing a match, then the food will not get digested and can
cause stomach pain.
Our throat is not just a hollow tube where air,food and water go down. There are actually muscles
in your throat that drag the food down to the stomach. Even if you are hanging upside down, the
muscles in your throat and oesophagus will push the food toward the stomach to be digested. Same
thing happens with the digestive juices.
Our body needs energy to do work, so one should not remain hungry for a long time.
17
Answers to Worksheets
Worksheet 1
1. (a) Parasitic
Canine
Premolars
Molars
Wisdom
tooth
2. (a) Ingestion
(d) Rounded
3. (a) Small intestine
(d) Large intestine
Incisors
Canine
Premolars
Molars
Wisdom
tooth
(b) Hydrochloric acid
(c) Liver, Pancreas
(e) Mucosa
(b) Mouth
(c) Large intestine
(e) Stomach
1. (a) A ruminant is a plant-eating animal that brings back swallowed food into the mouth to chew it
again.
(b) These animal bring back the chewed food to the mouth to chew it again, hence, they are called
ruminants.
2. (a) Carbohydrate
(c) Assimilation
(b) Food vacuole
(d) Tongue
3. Cud-Ruminants, Villi-Small intestine, Egestion-Anus, Rectum-Large intestine, Salivary gland-Saliva
18
Chapter 3
Fibre to Fabric
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what animal fibre is
• know the types of wool and wool yielding animals
• how the production of wool is done commercially
• how silk is obtained
Warm Up
To make the class interactive ask the students about which material is their uniform made up of.
Is it a plant product or an animal product? Is it artificial or natural? With the help of the Warm-up
section, the chapter can be started.
Concept Explanation
• Need of clothes: Why do we need clothes? What are these clothes made up of? How do we
obtain natural and synthetic fibres? Animal fibre with wool and silk as an example can be
explained in detail.
• Wool: Name the wool yielding animals and ask how woollen clothes keep us warm and why
are they worn in winters? How is wool extracted from sheep? With the help of Figure 3.9 on
page 35, the production of wool can be explained.
• Silk: What is silk? Name the insect from which it is obtained? What can it be woven into?
With the help of the life cycle of a silkworm (Figure 3.10), the whole process of obtaining silk
from the cocoon can be explained.
• Sericulture: How is silk thread obtained to produce the fabric? It can be explained with the
help of Figure 3.11.
• Health hazards: What are the health hazards of working in the wool industry and during
sericulture? These problems can be explained by giving examples given in chapter.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
19
Worksheet 1
1. Label the diagram shown below to show the steps that are necessary for the process
of weaving of fleece into yarn.
Rearing
(a)
(b)
(d)
(c)
Carding
(e)
Spinning and weaving
(f)
2. State whether the following statements are true or false.
(a) Cotton crop requires cold climate.
(b) Dacron is a man-made fibre.
(c) Nali is a carpet wool.
(d) Anthrax is a well-known sheep.
(e) Bombyx mori is the best known silkworm.
3. Label the given picture.
(a) _______
(d) _______
(b) _______
(c) _______
20
Worksheet 2
1. Give two examples of each of the following.
(a) Wool yielding sheep
_____________
_____________
(b) Stages of life cycle of silkworm
_____________
_____________
(c) Synthetic fibres
_____________
_____________
(d) Natural fibres
_____________
_____________
2. Write the quality of wool given by the following animals.
(a) Patanwadi sheep
(b) Angora goat
(c) Rampur bushair sheep
(d) Alpaca and llama
(e) Yak
(f) Cashmere goat
(g) Marwari sheep
(h) Bakharwal sheep
3. List out the processes involved in sericulture.
______________________________________________________________
______________________________________________________________
______________________________________________________________
21
Answers to Coursebook
A.
B.
C.
22
1. (a) Silk
(b) South America (c) Shearing
(d) Fleece
(e) Coarse wool
2. Wool—Sorter's disease
Merino—Spain
Angora goat—Mohair
Removing of fleece—Shearing
Cashmere goat—Pashmina shawls
1. Being an animal, sheep are prone to several diseases. Anthrax is one of the deadliest diseases which
can be transferred to the human beings through the animal. It is also known as the sorter’s disease.
It is a bacterial disease which is transmitted from an infected sheep to human beings when they
inhale the contaminated air. Nowadays, animals are properly vaccinated, hence, this disease rarely
occurs.
2. Wool fibre is highly porous and traps air in it. The trapped air acts as an insulator and does not
allow the body heat to escape to the surroundings. Thus, woollen clothes keep us warm and are
worn in winters.
3. Refer table given on page 33
4. When a pupa changes into a moth, it bursts the silken cell and leaves an indelible stain on the silk
cocoon. For this reason, silk farmers allow only a small percentage of pupae to develop into the
moths.
5. The rearing of silkworms to obtain silk fibres on a commercial scale is called sericulture.
6. (a) Wool is a dead tissue just like our hair, so shearing (removal of fleece) does not hurt sheep.
(b) To remove dirt, dust and grease from the sheared hair, scouring is necessary.
(c) Because of the crimp, woollen fibres have greater bulk.
7. The removal of fleece from a sheep’s body is called shearing. The filaments are taken out from the
cocoons by a process called reeling.
1. Shearing: The removal of fleece from a sheep’s body is called shearing. The fleece is removed as
one layer using large scissors and electric shaving machines. Sheep are usually sheared once a year,
but sometimes they can be sheared twice a year too. Shearing is done in early summer so that
they do not feel the summer heat. By the time winter arrives, they again grow a thick coat of hair.
After shearing is done, the sheep is dipped in an antiseptic solution to prevent skin infection. Just
as haircut does not hurt us, shearing does not hurt the sheep. Removing the heavy woollen coat
actually helps them as they do not require this in summer.
Scouring: The sheared hair is thoroughly washed in soap and water in tanks to remove dirt, dust
and grease. This process of removing dirt, dust and grease from the sheared hair is called scouring.
It can be done manually or by machines. The scoured hair is then dried.
Sorting or grading: The hair of different textures are sorted out on the basis of length, colour,
feature and the ease with which it can by dyed. The small fluffy hair, called burr, are picked out and
sent for reprocessing.
Carding: The process in which the selected curly wool fibres are straightened by passing them
through rollers is called carding.
Dyeing: The woollen fibres of white or light colours can be dyed in different colours of choice.
Drying: Containers of wool are put through rollers to squeeze out as much water as possible. Then
the wool is weighed and packed into bales. The bales are transported to the mills where they are
processed further.
Spinning and weaving: Two to four strands of wool are spun together to form thick threads called
yarn. The yarn can be rolled into balls of wool. The long fibres are either knitted or woven into
sweaters and other woollen clothes.
2. Refer to Figure 3.10 on page 37
Ova: It is the first stage of a silkworm’s life cycle. The female silk moth lays numerous (about 300 to
400) eggs during the summer season.
Larva: The eggs hatch within 3 to 5 days and caterpillars or silkworms emerge. For the next 40 to
45 days, the larvae eat and grow. They molt, or shed skin, to accommodate their growing size.
Pupa: The caterpillar stops feeding and is ready to pupate. The second moulting occurs inside the
cocoon, when the larva turns into a brown coloured pupa. It takes about 2-3 weeks for the pupa to
finally change into an adult moth.
Cocoon: The salivary glands of silkworms start secreting a sticky fluid called fibroin (a protein)
which hardens on exposure to air and forms silk thread. The caterpillar spins a protective structure
of these filaments (made up of fibroin) around its body through a figure-of-eight movements of the
head, called cocoon. The silkworm takes 3-7 days to prepare the cocoon.
Imago: The adult stage completes the life cycle of Bombyxmori. It is the reproductive stage where
adults mate and females lay eggs.
3. Cashmere goat: This goat lives in Jammu and Kashmir. This rare fibre is combed once a year from
the belly of the goat which can be woven into fine and high quality shawls, known as Pashmina
shawls.
Angora goat and Angora rabbit: The Angora goat belongs to the Angora region (Ankara) in
Turkey. The fibre obtained from the Angora goat is called mohair and the fibre obtained from the
Angora rabbit is called Angora wool. Wool obtained from these animals is warm, durable and light
weight. Mohair is very similar to wool in chemical composition but has a much smoother surface.
Alpaca and llama: These belong to the camel family. These animals are found in South America.
The fibre derived from an alpaca and a llama is soft, fine, shiny and light in weight.
Yak: This animal is found in Tibet and Ladakh. Hair of the yak is used to make coarse and warm
woollen fabrics.
Bactrian camel: The Bactrian camel is found in China and Mongolia. Its soft and fine undercoat is
a source of fibre to make wool. It gives the best quality camel wool.
4. The rearing of silkworms to obtain silk fibres on a commercial scale is called sericulture. Production
of silk from silk moth involves the following steps. The healthiest silk moths are chosen for laying
eggs. Their eggs are placed in open wooden or cardboard containers. After the eggs hatch, the
caterpillars are fed on mulberry leaves for about 30 days. During this time, twigs or racks are placed
on the trays where the silkworms spin the cocoons. If the silkworm is allowed to mature and break
through the cocoon, the silk would be rendered useless for commercial purposes. Therefore, the
cocoon, along with the insect is plunged into boiling water which kills the insect and dissolves the
glue which holds the cocoon together.
23
5.
D.
E.
1.
2.
3.
4.
Boiling: The pupae inside the cocoons are killed by putting them in boiling water. This also loosens
the filaments.
Reeling: The filaments are taken out from the cocoons by a process called reeling or filature.
Filaments from several cocoons are twisted together to make a strong thread, which is wound on
a reel.
Dyeing and weaving: Silk fabric can be dyed before or after weaving. Silk fibres are then dyed and
woven.
Scabies: Due to dipping hands in boiling water to boil the cocoons and check if the threads have
loosened or not, blisters and wounds are caused on the skin of the workers. This leads to scabies or
other such diseases.
Respiratory disease: Asthma, bronchitis and other breathing problems are caused when the
workers inhale vapours that are released due to the boiling of cocoons or due to the release of
diesel fumes from machines.
Loss of hearing: Due to the noise made by spinning and winding machines and looms, workers
suffer from hearing disorders.
Backache and other problems: The workers have to stand continuously for 12-16 hours in a day
to separate cocoons and reel the silk threads which leads to backaches and spinal cord problems.
Refer to Figure 3.10 on page 37
To get silk, silkworms are killed, therefore, animal rights activist oppose the commercial process of
obtaining silk.
Because in this process no harmful chemical is released.
Wool traps air the most. The trapped air acts as an insulator and does not allow the body heat to
escape to the surroundings. Thus, woollen clothes keep us warm.
Silk and wool are both animal fibres and therefore give out a smell like that of burning hair. While
cotton is a plant fibre which does not give the same smell on burning.
Answers to Worksheets
Worksheet 1
1. (a) Breeding
(b) Shearing
(c) Scouring
(d) Sorting
(e) Dyeing
(f) Drying
2. (a) F
(b) T
(c) T
(d) F
(e) T
3. (a) Egg
(b) Larva
(c) Pupa
(d) Adult
Worksheet 2
1. (a) Lohi, Nali
(b) Larva, Pupa
(c) Nylon, Rayon
(d) Cotton, Wool
2. (a) For hosiery
(b) Woollens
(c) Brown fleece
(d) Soft and fine
(e) Coarse wool
(f) High quality shawls
(g) Coarse wool
(h) Woollen shawl
3. Boiling, reeling, dyeing and weaving are the main steps involved in sericulture.
24
Chapter 4
Chemicals and Chemical Changes
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• know what are chemical substances
• understand what are atoms and molecules
• differentiate between elements, compounds and mixtures
• know what are chemical symbols
• understand what is atomicity
• know what is valency
• differentiate between physical and chemical change
Warm Up
Make the class interactive by asking the students to show their tiffin boxes and water bottles. Ask
them to name the material used to make the tiffin box and the water bottle. Now, take a paper and
tear it. Tell students that tearing of paper is a physical change as no new substance is formed. Make
your class more interactive by explaining the Warm-up section.
Concept Explanation
• Chemical substances: Explain to students that all substance are made up of very small
particles called atoms and molecules. Tell them that atoms are the smallest particles of a
substance they may or may not exist independently. Also explain to them that two or more
atoms combine to form a molecule.
• Element: Explain that an element is a pure substance which is composed of only one kind of
atom or molecule.
• Compound: Explain that compounds are made up of two or more elements.
• Mixture: It is formed when two or more substances are simply mixed together. There is no
chemical change seen in them.
• Chemical formula: With the help of the table given on page 46, chemical formulas can be
explained. Examples 1, 2 and 3 will help the students to understand the concept clearly.
• Chemical equation: Explain to students what a chemical reaction is and how it is written.
25
• Chemical changes and physical changes: These can be explained with the help of examples
and experiments and very easily demonstrated in the class. With the help of Activity 1,
differentiation between physical and chemical changes can be discussed in the class.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
26
Worksheet 1
1. Which process is shown in the given picture? What type of change is it?
________________________________________________________________
________________________________________________________________
2. Write the chemical formula for each of the following.
(a)
Methane
__________________
(b) Carbon dioxide
__________________
(c)
__________________
Carbon disulphide
(d) Magnesium oxide
__________________
(e)
__________________
Calcium carbonate
3. Melting of wax is a change wherein a solid changes to a liquid. Give one or more
example of such a change which you observe in your surroundings.
________________________________________________________________
________________________________________________________________
________________________________________________________________
27
Worksheet 2
1. Match the following.
Column A
Column B
Iron oxide
Sugar candy (mishri)
Souring of milk
Turns lime water milky
Deposition of zinc on iron
Rust
CO2
Chemical change
Large crystals
Galvanisation
2. Fill in the blanks.
(a) A physical change is generally a ______________change.
(b) As grinding of wheat grain changes its size, hence it is a ____________ change.
(c) Iron equipment kept in the garden gets ______________ . It is a _____________
change because a new ______________ is formed.
(d) Making salt solution is a ______________ change.
3. Write chemical equations using the substances given in the box.
Iron nail, magnesium ribbon, oxygen, copper sulphate,
magnesium oxide, iron sulphate, copper.
________________________________________________________________
________________________________________________________________
________________________________________________________________
28
Answers to Coursebook
A.
B.
1. (a) T
(b) F
(c) F
(d) T
(e) F
2. Melting of ice—Physical change
Rusting of iron—Chemical change
Reactant—Chemical substance which participates in a reaction
Air—Mixture
Water—Compound
1. (a) Atoms are the smallest particles of a substance. Atoms may or may not exist independently.
(b) The number of atoms present in a molecule of an element is called its atomicity.
(c) The combining capacity of the atom of an element is called its valency.
(d) It is the process in which a layer of zinc is deposited on the iron objects.
(e) The method used for obtaining a substance in pure and solid crystals from its impure compound
is called crystallisation.
2. (a) Physical change: The change in which no new substance is formed is called a physical change.
A change in the physical properties of a substance such as shape, size, colour and state of the
matter is a physical change. Examples of physical changes are melting of ice, boiling of water,
freezing of water, condensation, crystallisation and heating of metals till they become red hot,
etc.
Chemical change: A chemical change occurs when two or more substances undergo a chemical
reaction and are converted into one or more new substances with different sets of properties.
For example, formation of rust on iron objects which are kept in the open for a long time,
digestion of food.
(b) Element: An element is a pure substance which is composed of only one kind of atom or
molecule. For example, gold, iron and aluminium.
Compound: A compound is a substance which is made of two or more elements which are
combined chemically in a fixed proportion.
(c) Atom: Atoms are the smallest particles of a substance. Atoms may or may not exist
independently.
Molecule: When two or more atoms join together, a molecule is formed. A molecule can exist
independently.
(d) Compound: A compound is a substance which is made of two or more elements which are
combined chemically in a fixed proportion.
Mixture: A mixture is formed when two or more substances are simply mixed together, but
they are not chemically combined.
3. Rusting occurs in the presence of oxygen and water. Rusting can be prevented by adopting any of
these methods.
Galvanisation: It is the process in which a layer of zinc is deposited on the iron objects. The water
pipes used in our houses are made of galvanised iron.
Alloy formation: Stainless steel is an alloy of other metals and iron. Stainless steel is resistant to
rusting.
Painting: By painting the surface of an iron object, we can protect it from rusting.
Oiling: Oiling iron objects protects their surfaces from coming in contact with moisture and air
and prevents rusting.
29
C.
4. It is very inconvenient to refer to the elements and their compounds using their full names. To
make it easy, scientists have given them a symbol or an abbreviation.
5. (a) Mg + O2  MgO
(b) MgO + H2O  Mg(OH)2
(c) CuSO4 + Fe  FeSO4 + Cu
1. The process of rusting can be represented as:
Iron + Oxygen + Water  Iron oxide
Fe + O2 + H2O  Fe2O2 (rust)
2. (a) CH3COOH + NaHCO2  CO2 + H2O + CH2COONa
(b) Ca(OH)2 + CO2  CaCO3 + H2O
(c) Fe + CuSO4  FeSO4 + Cu
3. (a) 2Na + 2H2O  2NaOH + H2
(b) 2Na + Cl2  2Nacl
(c) Na2O + H2O  2NaOH
(d) CH4 + 2O2  CO2 + 2H2O
4. Refer to Experiment 3 on page 53
5. Follow the steps given below to write the chemical formula of a compound.
• Write the symbols of the elements present in the compound.
• Write the valencies of the constituent elements below them.
• Cross over or swap the valencies of these elements and write them with the elements as subscripts.
• If the valency can be simplified then divide both the valencies with the smallest valency of the
element. If the valency of any element is 1, then it cannot be simplified further. Then, write the
formula of the compound.
Example: Formula of potassium oxide
Example 1: Formula of potassium oxide
Example 2: Formula of aluminium oxide
Step 1
Symbol K
O
Step 1
Symbol Al
O
Step 2
Valency 1
2
Step 2
Valency 3
2
Step 3
Swap 2
1
Step 3
Swap 2
3
Step 4
Divide 2
1
Step 4
Divide 2
3
Formula Al2O3
Formula K2O
Example 3: Formula of carbon disulphide
Step 1
Symbol C
S
Step 2
Valency 4
2
Step 3
Swap 2
4
Step 4
Divide 1
2
Formula CS2
30
D.
E.
1.
2.
3.
1.
Rusting
Chemical change
Fe + O2 + H2O  Fe2O3 (rust)
In coastal areas, humidity in air is more and salt is also present in the water vapour which increases
the rusting of iron objects. Therefore, people living there need to make extra efforts to protect iron
objects.
2. Perfume got vaporised.
3. The iron present in apple gets oxidised in the presence of oxygen in air and therefore, the sliced
apple had turned brown.
4. Common salt is NaCl which is made up of two elements such as Na and Cl while salt solution is a
mixture because it is made up of two compounds such as NaCl and water.
Answers to Worksheets
Worksheet 1
1. Rusting or iron, chemical change
2. (a) CH4
(d) MgO
(b) CO2
(c) CS2
(e) CaCO3
3. Burning of crackers is a change where chemical energy changes to heat and light energy.
Worksheet 2
1. Iron oxide-Rust, Souring of milk-Chemical change, Deposition of zinc on iron- Galvanisation, CO2Turns lime water milky, Large crystals- Sugar candy (mishri)
2. (a) Reversible
(b) Physical
(c) Rusted, chemical, substance
(d) Reversible/physical
3. 2Mg + O2  2MgO
Fe + CuSO4  Cu + FeSO4
31
Chapter 5
Temperature and Heat
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• list different separation methods.
• explain different separation methods like handpicking, threshing, winnowing, sieving,
sedimentation and decantation, filtration, evaporation and condensation.
• understand the importance of separation of substances.
• understand the principle behind the separation methods.
• acquire skills to perform experiments using suitable techniques in the lab.
• identify the components in a mixture and separate them using suitable methods.
• identify the solute and the solvent in a given solution.
Warm Up
To make the class interactive, carry a hot cup of water and ice. Let students touch them one by one.
Then ask what they felt after touching? Now, discuss temperature and correlate it with weather
conditions. Then show them thermometer and ask its importance. With the help of the Warm-up
section, tell students about the concept of hot and cold objects.
Concept Explanation
• Temperature: Explain to the students about temperature. How is it measured? Tell them about
different types of thermometer such as mercury thermometer and alcohol thermometer.
• Heat: Explain to students how heat is transferred from one object to another due to difference
in their temperatures.
• Conduction: Explain to students that conduction is just like passing of a book from one
child to another. This can very well be explained by Experiment 2. Conduction can also be
explained with the help of Experiment 3. Also explain how different solids conduct heat at
different rates.
• Convection: This concept can be explained very well citing the example of convection current
in coastal areas and some other applications given in book.
• Radiation: Explain to students that when you stand under the sun or near a fire, you feel
warmth, this is due to radiation. It is a mode of transfer of heat without any medium.
32
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
33
Worksheet 1
1. Name the different processes taking place and also define them.
(c) ____________
(a) _ _ _ _
_______
_
(b) ____________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
2. Fill in the blanks.
(a) _____________ is a device used to measure heat. Mode of heat transfer in which
energy can travel in vacuum is called _____________.
(b) Air expands on _____________.
(c) On cooling, the temperature of an object _____________.
(d) The heat flow always from _____________ object to _____________.
(e) _____________ metal is used in the bulb of thermometer.
(d) We should use _____________ or _____________ utensils for cooking food.
34
Worksheet 2
1. Wax coated on an iron rod melts as we heat the iron rod. Give reason. Also name
the process of heat transfer.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
2. A beggar wrapped himself with newspapers on a cold winter night. This helped
him to keep himself warm because
(a) newspaper is a conductor of heat.
(b) friction between the layers of newspaper produced heat.
(c) air trapped between the newspaper is a bad conductor of heat.
(d) newspaper is at higher temperature than the surrounding temperature.
3. Label the following diagrams correctly.
4. What is convection?
_________________________________________________________________
35
Answers to Coursebook
A.
B.
C.
36
1. (a) Radiation
(b) Radiation
(c) Mercury
(d) Conductors, insulators
(e) Black
2. Thermos flask—Maintains the temperature hot or cold
Boiling point of water—100°C
Air— Insulator of heat
Sea breeze—From land to sea
Land breeze— From sea to land
Normal body temperature— 37°C
1. (a) This is because light-coloured clothes absorb lesser heat and keep us cool in summer.
(b) Warm air being lighter rises up and leaves the room through ventilators provided near ceilings.
(c) Iron and aluminium are metals and metals are good conductors of heat.
(d) Warm air is lighter and rises up. Therefore, hot air balloon rises up in the air.
2. (a) Convection: Convection is a mode of heat transfer in which the heat energy is transferred
from one part to another by the actual movement of the molecules of the medium.
Radiation: The mode of transmitting heat that requires no medium is known as radiation. It is
transmitted in the form of electromagnetic waves.
(b) Conduction: Conduction is the mode of heat transfer from a region of lower temperature
within a body, or when two bodies are in contact, and it takes place by collisions between
neighbouring atoms and molecules of the body.
Convection: Convection is a mode of heat transfer in which the heat energy is transferred
from one part to another by the actual movement of the molecules of the medium.
(c) Sea breeze: The pressure of air on the land decreases in comparison to the seawater. Thus, air
from the sea blows towards the land and causes sea breeze.
Land breeze: The cold air that is heavier, starts blowing from the land towards the sea, giving
rise to the land breeze.
(d) Clinical thermometer: A medical thermometer used for measuring the human body
temperature.
Laboratory thermometer: The thermometer that is used in laboratory is called the laboratory
thermometer.
(e) Conductors: Materials which allow heat to be conducted through them easily are known as
conductors of heat. For example, metals such as iron, copper, silver and aluminium are good
conductors of heat.
Insulators: Materials which do not allow heat to flow through them are called non-conductors
or insulators of heat. For example, wood, paper, glass, asbestos and bakelite are non-conductors
of heat.
3. Temperature: The degree of hotness or coldness of an object is called its temperature.
Heat: The energy which is transferred from one object to another due to the difference in their
temperatures is called heat.
4. Different ways in which heat flows are conduction, convection and radiation.
5. The kink is made to ensure that the mercury does not contract (flow back into the bulb) before the
thermometer has been read.
1. Refer page 61 of the textbook.
2. In solids, the molecules are very closely packed and they cannot move around freely. They can,
however, move or vibrate about their mean position only. While in gases, the molecules are very
loosely packed and they can move around freely. Therefore, gases expand more.
D.
E.
3. There is vacuum in between the two walls which reduces the loss of heat due to conduction and
convection. The outer surface of the inner wall and the inner surface of the outer wall are silvered
and polished. The silver surface prevents the loss of heat due to radiation. The mouth is narrow and
closed with a plastic cap, which is a bad conductor of heat.
4. Refer Experiment 2 given on page 64.
5. Dark-coloured objects absorb more heat radiation than the light-coloured ones. Therefore, the
surfaces of solar heaters are painted black.
6. Refer Experiment 1 given on page 63.
7. White and light-coloured clothes are comfortable to be worn in summers and dark-coloured
clothes are usually worn in winters. This is because light-coloured clothes absorb lesser heat and
keep us cool in summer. Darkcoloured clothes absorb more heat and keep us warm in winters.
Refer to Figure 5.5 on page 66
1. We cannot use a clinical thermometer to measure the temperature of boiling water because the
range of the clinical thermometer varies only 35°C–42°C and the temperature of boiling water will
rise this limit.
2. Light colours absorb less heat than dark colours, therefore, it is advised to paint the outer walls of
the houses present in hot regions using white or light colours.
3. When the sun's rays hit clouds, they are reflected back into space, never reaching the ground.
Thus, cloudy days are cooler. However, at night clouds act as a "blanket" preventing heat loss from
the earth. As a result, cloudy nights generally are warmer.
4. The milk of Aayushi’s glass will cool faster because the heat of the warm milk will get transferred to
the spoon.
Answers to Worksheets
Worksheet 1
1. (a) Conduction: Transfer of heat by the vibrating molecules.
(b) Radiation: Transfer of heat through no medium.
(c) Convection: Transfer of heat from one part to another by the actual movement of the molecules of
the medium.
2. (a) Thermometer, radiation
(b) Heating
(c) Decreases
(d) Hotter, cooler
(e) Mercury
(f) Iron, aluminium
Worksheet 2
1. The wax melts due to the transfer of heat by the process of conduction.
2. (b) Friction between the layers produce heat
3.
4. It is a mode of heat transfer in which the heat energy is transferred from one part to another by the actual
movement of the molecules of the medium.
37
Chapter 6
Acids, Bases and Salts
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what acids, bases and salts are
• know the type and uses of acids
• know about the different types of bases
• understand what indicators are
• know the difference between naturally occurring and synthetically obtained indicators
• understand the process of neutralisation
• learn about neutralisation in daily life
Warm Up
With the help of the Warm-up section, you can start the topic by asking what is common among all
shown and what are their uses. Tell the students that acids, bases and salts have importance in our
lives.
Concept Explanation
• Acids: Acids like citric acid, tartaric acid are naturally occurring acids. Explain to students
that they are obtained from animals and plants and, hence, are called organic acids. Tell
students that acids obtained from minerals or chemicals are called mineral acids.
• Bases: Substances like baking soda are called bases. Tell students that bases are hydroxides of
metals and are divided into two types, i.e., weak and strong.
• Indicators: Explain to students that acids and bases can be tested by means of indicators
which are natural as well as synthetic in nature.
• Neutralisation: Explain students when acids react with bases, salt and water are obtained.
• Neutralisation in daily lives: When an ant or a bee stings, baking soda is applied on the
affected part to get relief from the swelling and irritation of the bitten area.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
38
Worksheet 1
1. Define the following.
(a) Indicator
______________________________________________________________
______________________________________________________________
(b) Anhydrous salt
______________________________________________________________
______________________________________________________________
(c) Water of crystallisation
______________________________________________________________
______________________________________________________________
(d) Alkali
______________________________________________________________
______________________________________________________________
(e) Organic acids
______________________________________________________________
______________________________________________________________
(f) Neutralisation reaction
______________________________________________________________
______________________________________________________________
(g) Dilute acids
______________________________________________________________
______________________________________________________________
39
Worksheet 2
1. Write the formula of the following.
(a) Nitric acid
__________________
(b) Magnesium hydroxide
__________________
(c) Sodium hydroxide
__________________
(d) Sulphuric acid
__________________
(e) Ammonium hydroxide
__________________
2. Write two example for the following.
(a) Strong acid
__________________
__________________
(b) Weak base
__________________
__________________
(c) Natural indicator
__________________
__________________
(d) Synthetic indicator
__________________
__________________
(e) Strong base
__________________
__________________
3. Mention the weak acid, weak base, strongest acid, strongest base and neutral in the
given picture.
40
Answers to Coursebook
A.
B.
C.
1. (a) blue
(b) yellow
(c) green
(d) Calcium hydroxide
(e) formic
2. (a) Sulphuric acid
(b) Acetic acid
(c) Salt
(d) Green
(e) Carbon dioxide
1. The substances that are sour to taste are called acids while the substances that are bitter to taste are
base.
2. Refer page 77
3. Indicators show a change in colour when they come in contact with an acid or a base. For example,
Phenolphthalein and litmus.
4. The acids which are derived from animal and plant materials are called organic acids. For example,
citric acid, tartaric acid, lactic acid and acetic acid.
5. Acids react with metals to form hydrogen gas, therefore acids are not kept in metal container.
6. Base neutralises the formic acid left behind by the sting and also helps to reduce the pain.
7. The substances that are used to prevent acidity. For example, aluminium hydroxide or magnesium
hydroxide.
8. In case of acidity, more acid is produced in the stomach which causes irritation. To counter this
irritation, an antacid tablet or liquid is taken which contains aluminium hydroxide or magnesium
hydroxide. They are weakly basic in nature, therefore, neutralising the excess acid present in the
stomach.
9. (a) Acids which are derived from minerals or chemicals are called mineral acids. For example,
H2SO4.
(b) Natural indicators are obtained from brightly coloured plant parts such as petals, roots or
leaves.
(c) Most of the salt crystals contain some molecules of water. This is called water of crystallisation.
(d) The acids which are derived from animal and plant materials are called organic acids.
(e) Bases which are soluble in water are called alkalis.
(f) The hydrated salts that have lost their water of crystallisation are called anhydrous salts.
1. (a) Before discharging the industrial waste into drains or rivers, it must be checked and neutralised
to protect the aquatic animals from the adverse effects. Too much of acidic waste can be treated
with quicklime or slaked lime. Too much of basic waste can be treated with an acid or acidic
waste discharged from some other industry.
(b) Calamine solution contains zinc carbonate which is a weak base and also helps to reduce the
pain.
(c) In case of acidity, more acid is produced in the stomach which causes irritation. To counter
this irritation, an antacid tablet or liquid is taken which contains aluminium hydroxide or
magnesium hydroxide. They are weakly basic in nature, therefore, neutralising the excess acid
present in the stomach.
2. The solution is acidic in nature.
3. The reaction between an acid and a base (or an alkali) to form salt and water is called neutralisation
reaction. Heat is evolved in this process. The salt formed may form acidic, basic or neutral solution
with water.
Acid + Base  Salt + Water + Heat
Example: HCl + NaOH  NaCl (salt) + H2O
41
4. (a) It is used as a cleaning agent. It is used for making fertilisers.
(b) It is used for cleaning sinks and sanitaryware. It is also used for cleaning iron sheets before
galvanisation.
(c) It is also called Milk of Magnesia. It helps to neutralise excess of acidity in the stomach. It is
used as an antacid or a laxative.
5. Acids: H2SO4 (sulphuric acid), HNO3 (nitric acid) and HCl (hydrochloric acid).
Bases: Sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), potassium hydroxide (KOH)
Uses:
Hydrochloric Acid (HCl)
• It is used for cleaning sinks and sanitary ware.
• It is also used for cleaning iron sheets before galvanisation.
Sulphuric Acid (H2SO4)
• It is used in car batteries.
• It is used in the manufacture of paints, drugs, dyes and artificial silk.
Sodium Hydroxide (NaOH)
• It is also called caustic soda.
• It is used in the manufacture of soaps and detergents.
Calcium Hydroxide (Slaked lime) [Ca(OH)2]
• It is used in whitewashing of walls.
• It is used in the manufacture of bleaching powder.
6. Properties of salt are as follows.
•Melting and boiling points: Salts have high melting and boiling points.
•Solubility in water: Salts are usually soluble in water. For example, sodium chloride and
potassium sulphate are soluble in water. Salts such as silver chloride are insoluble in water.
•Conduction of electricity: Distilled water is a bad conductor of electricity. When some salt is
added to it, the solution becomes a good conductor of electricity.
•Water of crystallisation: Most of the salt crystals contain some molecules of water. This is
called water of crystallisation. The salt containing the water of crystallisation is called hydrated
salt. This water of crystallisation gives the crystal its shape, it is lost when the salt is heated.
On heating, the colour and the crystallised structure of the salt can also change. For example,
CuSO4.5H2O (hydrated copper sulphate) salt is blue in colour. When it is heated, it loses the
water of crystallisation and changes into CuSO4 (anhydrous copper sulphate), which is white in
colour. The hydrated salts that have lost their water of crystallisation are called anhydrous salts.
D.
The solution in the first beaker is acidic while in the second beaker is basic.
E.
1. Soaps are basic in nature. When turmeric comes in contact with a base, it give red colour.
2. Too much of acidic waste can be treated with quicklime or slaked lime. Too much of basic waste
can be treated with an acid or acidic waste discharged from some other industry.
3. Soaps are basic in nature while our skin is acidic. Therefore, it is not advised to use soap for face
washing.
4. Toothpastes are basic in nature which neutralise the acids and prevent tooth decay.
5. (a) Neutral
(b) Basic
(c) Acidic
42
Answers to Worksheets
Worksheet 1
1. (a) A substance which shows a change in colour in the presence of acids or bases.
(b) Salt which has lost its water of crystallisation.
(c) The water molecules present in solid crystals of salts.
(d) Highly soluble bases.
(e) Acids which are naturally present in plant and animal materials.
(f) Reaction between acids and bases to form salt and water
(g) Acids which contain more amount of water
Worksheet 2
1. (a) HNO3
(b) Mg(OH)2
(c) NaOH
(d) H2SO4
(e) NH4OH
2. (a) Nitric acid and sulphuric acid
(b) Aluminum hydroxide and Ammonium hydroxide
(c) Turmeric and litmus
(d) Phenolphthalein and methyl orange
(e) Sodium hydroxide and potassium hydroxide
Strongest base
Weak base
Neutral
Weak acid
Strongest acid
3.
43
Chapter 7
Climate and Adaptations
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what weather is
• know how rainfall is measured
• learn about the instrument used to measure humidity
• understand how climate and weather are correlated
• explain how different factors affect the weather and climate of the place
• identify the different climate zones
Warm Up
Explain to students what is weather report with the help of the Warm-up section given in the chapter.
Concept Explanation
• Weather: Explain to students that weather at a given place depends on humidity, rainfall,
snow, temperature and wind. Prediction of weather conditions of a place is called weather
forecasting. Tell students about the satellites which send images and after studying these the
forecast is released. This helps people to plan their activities.
• Climate: Explain to students that climate is a long-term pattern of weather in a particular
area. There are certain geographical factors on which the climate of the earth depends such
as distance from the sun, tilt of the earth on its axis, etc.
Climate of a place also depends on the distance from the equator, height above sea level,
distance from the sea and mountains.
• Effect of human activities on the climate of a place: Explain to students how industrialisation
and deforestation affect the climate of a place.
• Adaptation: Tell students that adaptation helps an animal to survive in its natural environment.
Explain to them about the permanent and temporary adaptations by means of examples.
With the help of some animals like chameleon, elephant, adaptation can be explained.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
44
Worksheet 1
1. What do given devices measure?
(a)
_________________________
(b)
_________________________
(c)
_________________________
2. List the factors that affect the climate of a place.
45
Worksheet 2
1. Write any two adaptations for the following animals.
(a) Elephant
(b) Penguin
(c) Polar bear
(d) Camel
(e) Monkey
(f) Bearded ape
(g) Chameleon
46
Answers to Coursebook
A.
B.
1. (a) F
(b) T
(c) T
(d) F
(f) T
2. Humidity—Hot and wet
Temperature—The study of weather
Meterology—Maximum-minimum thermometer
Rainfall—Rain gauge
Kerala—Hygrometer
1. (a) Their body is streamlined to reduce the drag in water.
(b) They migrate to avoid unfavourable conditions of food availability and temperatures.
(c) Tropical rainforests have the maximum variety of animals and plants as these areas have
favourable temperature and plenty of water.
(d) Camels can live in desert conditions because of their adaptations according to the desert
conditions while human beings find it difficult to adapt to desert life.
2. (a) Weather: The state of the atmospheric conditions such as humidity, rainfall, snow, temperature,
cloud and wind at a given place and time is called the weather of the place at that time.
Climate: Climate is the long-term pattern of weather in a particular area, long enough to yield
meaningful averages.
(b) Temporary adaptations: These are short-term adaptations and are not inherited by other
generation. For example, the colour of the skin gets tanned on exposure to sunlight for a long
time.
Permanent adaptation: It leads to permanent changes in the individual. It is inherited from
one generation to another. For example, camel is well adapted for living in desert areas.
(c) Polar region: It has the coldest climate and the temperatures are always below the freezing
point. The area is usually covered with snow which melts only during summer season which
lasts for a very short time.
Tropical zone: This is the warmest region with average high temperature and receives the
maximum amount of rainfall.
(d) Humidity: The amount of water vapour present in the air determines humidity.
Precipitation: The amount of water vapour that falls as rain.
3. Exploitation of the environment and natural resources by human beings has also resulted in various
climatic changes. Some of its major causes are as follows.
Industrialisation: The Industrial Revolution in the 18th century led to the establishment of new
industries. Industries and transportation of goods consume large amount of fossil fuels. Use of
fossil fuels increases carbon dioxide in the atmosphere which results in acid rains, global warming
and pollution of air, water and soil.
Deforestation: The large-scale cutting of trees is called deforestation. It results in an increase in
the amount of carbon dioxide in the atmosphere. Trees absorb carbon dioxide and produce oxygen
during photosynthesis. Increased levels of carbon dioxide in the absence of trees lead to an increase
in the atmospheric temperature as carbon dioxide absorbs heat, resulting in global warming.
4. The climate of a place depends on many factors such as distance from the equator, height above sea
level, distance from the sea and mountains, and many more.
47
5. (a) The earth is slightly tilted on its axis at an angle of 23.5° as it revolves around the sun in an
elliptical orbit. This is called the angle of inclination.
(b) Adaptations can be defined as the changes in the structure or behaviour of an organism that
allow it to survive in a particular habitat.
C. 1. Polar bears are the largest land carnivores. Their white fur helps them to blend with the snow and
protects them from their predators. It also helps them to catch their prey.
• A polar bear has a layer of fat under its skin called blubber which provides additional insulation
and helps it to stay warm. It also has a thick layer of fur to survive in extreme cold climate.
• The wide and large paws help a polar bear to walk in the snow, swim in water, dig the snow,
hold the prey and defend itself.
• When a polar bear swims underwater, it closes its nostrils so that water cannot get inside.
• The polar bear has a strong sense of smell to locate its enemy and prey.
• During winter, polar bears go for a long winter sleep called hibernation in big dens. During
this time, they do not eat or drink. They remain completely inactive. They survive on the stored
body fat which gets converted into energy so that the basic life processes can continue. The
cubs are born in the den.
2. Factors affecting the climate of a place: The climate of a place depends on many factors such as
distance from the equator, height above sea level, distance from the sea and mountains, and many
more.
Distance from the equator: Distance of a place on the earth from the equator affects its climate.
The Sun’s rays fall directly at equator thus it is hotter. At the North and South poles, the Sun’s rays
fall at an angle; hence, these places are cooler. For example, it is much warmer in India, which is
nearer to the equator than Greenland which is nearer to the North Pole.
Height above sea level: The higher a place is, the cooler it is. That is why people visit hill stations
which have a cooler climate than plains during the summer months.
Distance from the sea and mountains: The sea has a moderating influence on the climate of a
place. The places near the coast are neither too hot nor too cold. The places far away from the
sea have extreme climates with very hot summer and very cold winter. Mountains also affect the
climate of a place by changing the direction of the wind and by influencing the rainfall. You must
be familiar with the fact that the Himalayas affect the climate of North India.
3. Distance of a place on the earth from the equator affects its climate. The sun’s rays fall directly at the equator, thus, it is hotter. At the North and South poles, the sun’s rays fall at an angle; hence,
these places are cooler. For example, it is much warmer in India, which is nearer to the equator than
Greenland which is nearer to the North Pole.
4. The massive size of the elephants protects it from predators. • In elephants, the trunk is an extremely useful organ. It helps them to eat food which is present
at a higher level in trees. It also allows them to get food and water from the ground, which they
otherwise would not be able to access.
• Elephants are mainly poached for their ivory. Their tusks which are the modified teeth, can also
help them to survive through dry spells, as they use them to bore down into the earth and find
water in dry riverbeds. They also use their tusks to extract the softwood of the trees which they
can eat.
48
•
Elephants live in hot conditions and need to cool themselves down. Since they are unable to
sweat, they flap their large ears to blow air which cools the blood in their capillaries which
then distribute the cooled blood in their body thus cooling the body. Asian elephants have
smaller ears than their African counterparts.
5. (a) A camel has long eyelashes to prevent the entry of sand in its eyes. Its thick eyebrows shield the
eyes from the hot sun.
• It has nostrils that can open and close so that sand does not enter its nose.
• Camels can survive for a week without water and for several months without food. They store
fat in their hump which is a source of energy for them when they do not eat or drink. They can
drink up to 46 litres of water at one time.
• A healthy camel’s body temperature changes throughout the day from 34°C to 41.7°C (93°F to
107°F). Thus, the camel does not sweat like other mammals when it feels hot. This allows the
camel to conserve water. A camel also excretes very little amount of water as waste.
• A camel’s feet are wide. Its huge feet help it to walk on sand without sinking into it.
• Camels have thick lips to eat the leaves of prickly desert plants without feeling the pain.
• The colour of their body helps them to blend with the sand.
• A camel’s ears are covered with hair even on the inside. The hair helps to keep out the sand that
might blow into the animal’s ears.
(b) Kangaroo rat does not drink water, it utilises the moisture from the food it eats.
(c) Fennec fox has long ears to keep its body cool.
6. Animals such as kangaroo rats, fennec foxes, and many other reptiles and birds inhabit the desert
areas. Most of these animals are nocturnal, i.e., they come out in night and sleep through the day
to avoid the harsh sunlight. Some of the desert animals survive the hot and dry summer season by
becoming inactive and sleeping under the ground. This is called aestivation. Fennec fox has long
ears to keep its body cool.
D.
Rain gauge is shown in the given picture. Amount of rainfall in an area is measured by using this
instrument.
E.
1. Polar regions: Because of the absence of blubber, human beings are unable to survive in polar
regions.
Deserts: Absence of hump, wide feet, thick lips, covered ears, long eyelashes in human beings,
makes it difficult for human beings to survive in deserts.
Tropical rainforests: Because of the absence of the camouflage property, human beings cannot
survive here.
2. The deforestation will result in the extinction of many animal species.
3. Due to increasing pollution, the ice is melting down gradually. Due to this it is becoming impossible
for polar bears to survive.
4. Yes, the government has taken the right step because this will slow down the process of deforestation
which will ultimately result in the protection of animals.
49
Answers to Worksheets
Worksheet 1
1. (a) Maximum-minimum thermometer
(b) Hygrometer
(c) Rain gauge
2. Distance from equator, height above sea level and distance from the sea and mountains
Worksheet 2
1. (a) The massive size of the elephants protects it from predators. In elephants, the trunk is an extremely
useful organ. It helps them to eat food which is present at a higher level in trees. It also allows them
to get food and water from the ground, which they otherwise would not be able to access.
(b) Penguins have webbed feet for powerful swimming. Their body is streamlined to reduce the drag in
water. Their wings are shaped like flippers which help them to swim underwater. Penguins have to
remain active to keep their body temperature high. They have a layer of fat (blubber) under their
skin to keep them warm in cold weather.
(c) When a polar bear swims underwater, it closes its nostrils so that water cannot get inside. The polar
bear has a strong sense of smell to locate its enemy and prey.
(d) A camel has long eyelashes to prevent the entry of sand in its eyes. Its thick eyebrows shield the eyes
from the hot sun. It has nostrils that can open and close so that sand does not enter its nose.
(e) Monkeys have long and coiled prehensile tail which helps in their movement from one branch of a
tree to another. Monkeys have grasping hands and feet with opposable thumb for a better grip.
(f) It has silver-white mane surrounding the head, cheeks and chin, as in lions. It lives on trees and
rarely comes on ground as it gets most of its food from the trees it lives on.
(g) Chameleons are capable of changing colour. These colour changes help them to camouflage
themselves and protect themselves from predators. A chameleon can extend its tongue about one
and a half times the length of its body. It has the ability to shoot its tongue out to catch the prey and
roll it up back inside its mouth.
50
Chapter 8
Soil
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand how soil is formed
• know how chemical or physical weathering helps in the formation of soil
• know different horizons of soil, different types of soil
• understand the process of soil erosion
• understand how soil pollution is caused due to human interference
Warm Up
Explain to students the role of different animals in maintaining soil fertility. With the help of the
Warm-up section, the role of different animals can be discussed. By showing the soils of different
areas, the topic can be started.
Concept Explanation
• Soil: Explain to students how soil is formed and how weathering helps in the formation of
soil. Lichens are also responsible for the formation of soil. Explain what the components of
soil are and what are the different soil horizon.
Tell them that soil is of different types because of its texture and absorption rate.
With the help of Experiments 1 and 2, absorbing capacity and rate of percolation of soil can
be demonstrated.
• Soil erosion: Explain how washing and blowing away of topmost layer of soil leads to soil
erosion. Explain how deforestation, overgrazing of animals, forest fire, floods lead to soil
erosion. Also tell students the ways to prevent soil erosion such as planting more trees,
preventing overgrazing, terrace farming, etc.
• Soil pollution: Explain to students how human activities lead to soil pollution and what
different measures should be taken to avoid it.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life
skills sections of the chapter. Discuss the terms and their meanings given at the end of the
chapter. Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
51
Worksheet 1
1. Write the difference between physical and chemical weathering.
2. Write the composition of soil.
3. Write the names of layers of the soil.
4. Write the formula to calculate the absorption of water by the soil.
5. Mention any two factors that affect the weathering of soil.
52
Worksheet 2
1. Arrange the steps of weathering of rocks by numbering them in sequence from 1
to 4.
2. What is the difference between sandy soil, clayey soil and loamy soil?
3. List the causes of soil erosion.
53
Answers to Coursebook
A.
B.
54
1. (a) F
(b) F
(c) T
(d) T
(e) F
2. (a) C horizon
(b) Soil
(c) Cotton
(d) Deforestation
(e) Prevention of soil erosion
1. (a) It retains moisture and becomes wet. When it dries up, it becomes hard and forms deep cracks.
Therefore, it is used in pottery.
(b) It is made up of large particles for easy circulation of water. It has large spaces.
(c) Formation of soil is an extremely slow process. It takes 500 years to produce just under an inch
of topsoil, which is the most productive layer of soil, therefore, it is a non-renewable resource.
(d) Plastic and metal do not get decomposed, therefore, these should not be thrown in the soil.
(e) Vegetation binds the particles of soil, therefore, soil not covered by vegetation gets eroded
easily.
2. (a) Some characteristics of soil form the basis for its classification into various types. It also
determines the types of crops that are grown in it. These properties are as follows.
• Absorption of water
• Moisture in the soil
• Percolation rate of water in soil
(b) A horizon: This layer is also called the topsoil. It consists of fine soil particles obtained from
parent material along with the organic matter. This layer supports the growth of plants and
other organisms. It is rich in humus and therefore dark in colour. It is soft, porous and can hold
water.
B horizon: It is also called the subsoil. This layer is rich in minerals that move down with water.
It contains compactly packed fine particles of soil. Farmers often mix horizon A and horizon B
when ploughing their fields.
(c) Soil erosion: The washing or blowing away of the top layer of the soil by running water or wind
is called soil erosion.
Soil conservation: The practice of preventing the soil from getting eroded.
3. 1st stage: The parent rocks expand in the presence of the sun.
2nd stage: In the cold and rain, expanded rocks shrink and get broken down into smaller pieces.
The smaller pieces of rocks are further broken down into even smaller pieces.
3rd stage: This forms a layer of soil which allows the growth of tiny microorganisms. These
microorganisms change the organic material composition and also add humus to it which makes
the soil fertile and rich in organic materials and minerals.
4th stage: As the soil particles become smaller in size, they are able to absorb water which can also
dissolve salts and other minerals. This allows the growth of plants in the soil.
4. Soil helps in the growth of plants.
• Soil maintains the balance in atmosphere by emitting and absorbing gases and dust.
• Soil provides habitat for animals such as mice and organisms such as bacteria and fungi.
• Soil absorbs, holds, releases, alters and purifies water in terrestrial ecosystems.
• Soil absorbs recycled nutrients, including carbon, so that living things can use them again.
• Soil is also used for making houses, buildings and bricks. They were also used to make ancient
artefacts.
• Soil acts as a natural filter to clean water before it moves into an aquifer.
5. The main components of soil are air, water, sand, clay, silt, pebbles and humus. The difference in the
proportion of these constituents leads to the formation of different kinds of soil.
Particle
Diametre (mm)
Clay
Less than 0.002
Silt
0.002 - 0.05
Sand
0.05 - 2.00
Five pebbles
2.00 - 5.00
Medium pebbles
5.00 - 20.00
Coarse
20.00 - 80.00
C. 1. Prevention of Soil Erosion
Soil erosion can be prevented by the following ways.
Planting wind breaks: A wind break is a line of plants that are planted to stop or slow down the
speed of wind. A thick row of bushes planted next to a field of plants can stop the wind from
blowing the soil away. This method also helps to prevent erosion due to water as the soil gets caught
up against the roots of the bushes, rather than being washed away.
Terrace farming: People cut large steps along the side of the hills to make fields to grow crops. These steps
or terraces slow down the speed of flowing water and thus reduce soil erosion.
By preventing overgrazing: Overgrazing by animals remove the green cover of the land which
binds the soil and prevents erosion. Therefore, animals should not be allowed to graze in one area
for a long time.
By construction of embankments: Dams and embankments on river banks prevent the running water
from washing away the soil. They also prevent flooding of the areas near rivers.
2. Each layer of a soil profile is referred to as a soil horizon. These horizons are identified by letters
(O, A, B, C and R). All the horizons together form a soil profile.
O horizon: The O horizon is thin in some soils, thick in others and not present at all in some other
soils. It consists of organic matter such as decomposing leaves and animal parts.
A horizon: This layer is also called the topsoil. It consists of fine soil particles obtained from
parent material along with the organic matter. This layer supports the growth of plants and other
organisms. It is rich in humus and therefore dark in colour. It is soft, porous and can hold water.
B horizon: It is also called the subsoil. This layer is rich in minerals that move down with water. It
contains compactly packed fine particles of soil. Farmers often mix horizon A and horizon B when
ploughing their fields.
C horizon: This layer contains the parent material. Here, we can find partly weathered rocks from
which the soil is developed. It is usually identified by cracks and crevices. It is very difficult to dig
beyond this layer.
R horizon: It is also called bedrock. It is the lowermost level and contains the parent rock. A mass
of rock such as granite, basalt, quartzite, limestone or sandstone forms the parent material for
some soils. The properties of these rocks greatly determine the composition of the soil.
3. Prevention of Soil Erosion: Soil erosion can be prevented by the following ways.
Planting wind breaks: A wind break is a line of plants that are planted to stop or slow down the
speed of wind. A thick row of bushes planted next to a field of plants can stop the wind from
blowing the soil away. This method also helps to prevent erosion due to water as the soil gets caught
up against the roots of the bushes, rather than being washed away.
55
Terrace farming: People cut large steps along the side of the hills to make fields to grow crops. These steps
or terraces slow down the speed of flowing water and thus reduce soil erosion.
By preventing overgrazing: Overgrazing by animals remove the green cover of the land which
binds the soil and prevents erosion. Therefore, animals should not be allowed to graze in one area
for a long time.
By construction of embankments: Dams and embankments on river banks prevent the running water
from washing away the soil. They also prevent flooding of the areas near rivers.
4. Soil is formed by the process of weathering of rocks. Weathering is the mechanical or chemical
process by which rocks on the earth’s surface are broken down into smaller pieces due to natural
forces such as wind, water, frost and roots of plants.
Weathering is of two types.
Physical or mechanical weathering: It involves the breakdown of rocks due to atmospheric
conditions such as heat, water, ice, pressure exerted by animals and movement of plant roots. The
chemical constituents of the soil do not change in this process.
Chemical weathering: It involves the breaking down of minerals to form new chemicals. Chemical
weathering is caused mainly by water. The rate of chemical weathering increases by 2-3 times when
the temperature increases by 10°C.
5. Some characteristics of soil form the basis for its classification into various types. It also determines
the types of crops that are grown in it. These properties are as follows.
• Absorption of water
• Moisture in the soil
• Percolation rate of water in soil
Absorption of water: The capacity of the soil to hold water before it starts dripping is called its
water absorption capacity. The percentage of water absorbed is calculated by using the following
formula.
Percentage of water absorbed = (U – V × 100)/U
Here,
U = Initial amount of water
V = Final amount of water
Moisture in the soil: The water content present in the soil is used by plants. Moisture content of the
soil mainly depends on the type of soil.
Percolation rate of water in soil: The phenomenon of absorption of water by soil is termed as
percolation. The rate of absorption is different for different types of soils. The rate of absorption of
a soil depends on its composition.
Percolation rate = Amount of water percolated (mL)/Percolation time (min)
6. There are a number of factors which affect soil formation. These factors are as follows.
Parent rock: As we know that soil particles are formed due to the breaking down of the parent
rock. If the parent rock is composed of salts and soft minerals, then the soil formed will be made up
of fine granules and composed of the same type of salt.
Climate of the area: The formation of soil is closely related to the climate of an area. If the
temperature of an area is very low, then the water particles present in the crevices of rocks will be
frozen. This will increase the pressure on the rocks and force them to crack. Colder regions have a
slower rate of soil formation. Humid and warm areas have a higher rate of soil formation.
Slope of the land: The landform of an area is also an important factor for the process of soil
formation. If the land of any area has a sloping surface then it will cause the removal of the top layer
56
7.
D.
E.
1.
2.
3.
4.
5.
of the soil due to flowing water or wind. These fine particles of soil get deposited in the plains.
Given, U (Initial amount of water) = 1 L = 1000 mL
V (Final amount of water) = 650 mL
Percentage of water absorbed = (U-V×100)/U
= (1000–650×100)/1000
= 35000/1000
= 35 %
Refer to Figure 8.3 on page 107.
Each layer of a soil profile is referred to as a soil horizon. These horizons are identified by letters
(O, A, B, C and R). All the horizons together form a soil profile.
O horizon: The O horizon is thin in some soils, thick in others and not present at all in some other
soils. It consists of organic matter such as decomposing leaves and animal parts.
A horizon: This layer is also called the topsoil. It consists of fine soil particles obtained from
parent material along with the organic matter. This layer supports the growth of plants and other
organisms. It is rich in humus and therefore dark in colour. It is soft, porous and can hold water.
B horizon: It is also called the subsoil. This layer is rich in minerals that move down with water. It
contains compactly packed fine particles of soil. Farmers often mix horizon A and horizon B when
ploughing their fields.
C horizon: This layer contains the parent material. Here, we can find partly weathered rocks from
which the soil is developed. It is usually identified by cracks and crevices. It is very difficult to dig
beyond this layer.
R horizon: It is also called bedrock. It is the lowermost level and contains the parent rock. A mass
of rock such as granite, basalt, quartzite, limestone or sandstone forms the parent material for
some soils. The properties of these rocks greatly determine the composition of the soil.
Formation of soil is a very slow process. It takes 500 years to produce just under an inch of topsoil,
which is the most productive layer of soil. Therefore, we should be worried about soil erosion.
He will use clayey soil for making pots because it retains moisture and becomes wet. When it dries
up, it becomes hard.
Clayey soil retains water and remains wet. And cactus plant is a desert plant which needs no water
to grow. Therefore, Rohan’s cactus plant died.
Fertile areas are used for growing crops while barren land should be used for industries and
residential buildings because industrial waste will pollute the soil that will reduce the fertility of the
soil.
Organic farming method is more beneficial than using chemical fertilisers because chemicals
pollute the soil on getting accumulated.
Answers to Worksheets
Worksheet 1
1. Physical or mechanical weathering: It involves the breakdown of rocks due to atmospheric conditions
such as heat, water, ice, pressure exerted by animals and movement of plant roots. The chemical
constituents of the soil do not change in this process.
Chemical weathering: It involves the breaking down of minerals to form new chemicals. Chemical
weathering is caused mainly by water. The rate of chemical weathering increases by 2-3 times when the
temperature increases by 10°C.
57
2.
Particle
Diametre (mm)
Clay
Less than 0.002
Silt
0.002 - 0.05
Sand
0.05 - 2.00
Five pebbles
2.00 - 5.00
Medium pebbles
5.00 - 20.00
Coarse
20.00 - 80.00
3. O horizon, A horizon , B horizon, C horizon, R horizon
4. Percentage of water absorbed = U – V × 100
U
Here,
U = Initial amount of water
V = Final amount of water
5. Parent rock, Climate of the area, Slope of the land
Worksheet 2
1.
1
4
3
2
2. Sandy soil: It is made up of large particles for easy circulation of water. It has large spaces.
Clayey soil: It is made up of small particles for air and water to circulate.
Loamy soil: It is a combination of sandy and clayey soil.
3. Deforestation, Overgrazing, Forests fires, Wrong agricultural practices, Floods
58
Chapter 9
Respiration
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what is respiration
• differentiate between internal and external respiration
• explain how oxygen is the major factor for respiration
• understand what is breathing, and how breathing rate differs
• know the how human respiratory system works
• explain the process of respiration in different other animals
Warm Up
To make the class interesting, start with the Warm-up section. Ask students to take a rough page.
Now ask them to blow it by means of air from their mouth. Ask them which organ is involved in this
process. Now give students balloons and ask them to inflate them in one minute. Ask them again
that which organ is involved and on which part of their body they have put stress.
Concept Explanation
• Respiration: Explain to students that respiration is the most important process in our body
as it produces energy. Tell students how respiration and breathing are the two different
processes. Now tell them that respiration is of two types. One in which oxygen is required,
called aerobic respiration. And the other in which no oxygen is required, called anaerobic
respiration.
Also perform Experiment 1 to show aerobic respiration.
• Breathing: Explain that breathing consists of two steps, namely, inhalation and exhalation.
This can be demonstrated by inhalation and exhalation exercise. Activity 1 can be of great
help to understand that breathing rate is very much dependent on time and the work one is
doing.
• Human respiratory system: With the help of a model, explain the process of respiration.
This will help students to understand different organs involved in respiration.
• Respiration in other animals: With the help of diagrams, explain respiration in plants. This
can be explained by showing stomata, lenticels in plants.
59
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
60
Worksheet 1
1. Label the given picture.
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
___________
2. What are the breathing organs in the given animals?
(a) Amoeba
(b) Cockroach
(c) Fish
(d) Human being
3. Write the functions of alveoli in human beings.
4. What is breathing rate?
61
Worksheet 2
1. What is the difference between inhalation and exhalation?
2. How do plants respire?
3. Define the following.
(a) Stomata
(b) Lenticels
(c) Epiblema
(d) Trachea
(e) Inhalation
62
Answers to Coursebook
A.
1. Cockroach—Spiracles
Plants—Stomata
Salamander—Moist skin
Fish—Gills
Human beings—Lungs
2. (a) F
B.
(b) T
(c) F
(d) F
1. (a) In woody plants, the stems have openings called lenticels for gaseous exchange.
(b) During respiration, we breathe in oxygen and give out carbon dioxide. Therefore, percentage of
carbon dioxide is more in the exhaled air.
(c) Hair and the moist layer inside our nose trap dust and germs and prevent them from entering
the body, thus cleaning the inhaled air.
2. (a) Refer table given on page 122.
(b) Respiration: Respiration is the process of releasing energy from the breakdown of food.
Breathing: Breathing involves intake of air rich in oxygen (inhalation or breathing in) and
giving out air rich in carbon dioxide (exhalation or breathing out.)
(c) Refer table given on page 128.
3. Breathing rate is the number of times a person breathes in one minute. When our body works
hard, it requires more energy. To get more energy, more amount of food needs to be broken down.
Therefore, more amount of oxygen is required which increases the breathing rate.
4. While running, the muscle cells do not get a regular supply of oxygen at a particular time, thus
forced to respire anaerobically. The glucose stored in the muscle cells gets converted into lactic acid
and energy is released. The lactic acid accumulates in muscles and causes muscle cramps. Massage
gives relief from cramps as it improves blood circulation. This supplies oxygen to the muscle cells
which breaks down lactic acid into carbon dioxide and water.
5. Breathing is the process of the intake of air rich in oxygen (inhalation or breathing in) and giving
out air rich in carbon dioxide (exhalation or breathing out). So no chemical change takes place.
Therefore, breathing is a physical process.
C.
1. Refer text given on page 127.
2. The oxygen is transported to the blood vessels of alveoli. In the blood, the oxygen combines with
haemoglobin and forms a compound called oxyhaemoglobin which is carried by the blood to all
cells of the body. In the cells, oxyhaemoglobin releases oxygen which helps to break down food
and generate energy. Along with energy, carbon dioxide, water and heat are also generated. Air
rich in carbon dioxide from the body enters the alveoli. The carbon dioxide and water vapour are
absorbed by the blood vessels of the alveoli and expelled out of the body.
The chemical reaction involved in the breakdown of sugar is as follows.
Sugar + Oxygen
Energy + Carbon dioxide + Water
63
The passage of air in this process can be summed up as follows.
Nostrils
Nasal cavity
Alveoli
Pharynx
bronchioles Larynx
Lung
Trachea
Bronchi
3. Roots: Roots absorb water along with dissolved oxygen and nutrients from the soil. The outer
surface of the roots has a thin layer of cells called epiblema. The air trapped between the soil
particles diffuses in the roots through these cells. Oxygen is taken in by the cells and carbon dioxide
is given out which diffuses into the soil. For proper root respiration, farmers plough or till the soil
so that tiny air spaces are created around the soil particles.
Stems: The stems of the woody plants have openings called lenticels for gaseous exchange.
Leaves: Leaves have minute openings called stomata. In the daytime, the leaves perform
photosynthesis by taking in carbon dioxide and giving out oxygen. At night, when photosynthesis
stops, leaves only respire. Thus, during the daytime, both photosynthesis and respiration occur in
plants, but at night, only respiration takes place.
4. Refer Experiment 1 given on page 121
5. Refer Experiment 2 given on page 126
6. Alveoli are richly supplied by blood vessels. These are the sites of gaseous exchange. Air rich in
oxygen enters the alveoli. The oxygen is transported to the blood vessels of alveoli. In the blood,
the oxygen combines with haemoglobin and forms a compound called oxyhaemoglobin which is
carried by the blood to all cells of the body. In the cells, oxyhaemoglobin releases oxygen which
helps to break down food and generate energy. Along with energy, carbon dioxide, water and heat
are also generated. Air rich in carbon dioxide from the body enters the alveoli. The carbon dioxide
and water vapour are absorbed by the blood vessels of the alveoli and expelled out of the body.
D.
E.
Refer to Figure 9.3 on page 125.
1. Nose has hair and a moist layer which prevent the entering of dust and germs in the body while if
we breathe through mouth then dust and germs enter in our body. Therefore, we should breathe
through nose.
2. Yes, both aerobic respiration and anaerobic respiration take place in the human body. In humans,
normally aerobic respiration takes place, but anaerobic respiration also occurs in the muscles.
3. When our body works hard, it requires more energy. To get more energy, more amount of food
needs to be broken down. Therefore, more amount of oxygen is required which increases the
breathing rate.
4. We should not sleep under a tree at night because at night no photosynthesis takes place, only
respiration takes place. Therefore, the amount of carbon dioxide given out by the tree becomes
more which is harmful for us.
64
Answers to Worksheets
Worksheet 1
1.
Nasal cavity
Nostril
Oral cavity
Larynx
Right main
bronchus
Right lung
Pharynx
Trachea
Left main
Bronchus
Left lung
Diaphragm
2. (a) Plasma membrane
(b) Spiracles
(c) Gills
(d) Lungs
3. These are the site of gaseous exchange.
4. Breathing rate is the number of times a person breathes in one minute.
Worksheet 2
1. Inspiration or inhalation: It means to take in air which is rich in oxygen. In this process, the ribs in the
chest cavity of human beings move upwards and outwards, while the diaphragm moves downwards. The
chest cavity increases in size. The lungs expand and the air from the surroundings gets sucked into the
lungs which fills the lungs with air.
Expiration or exhalation: It means to give out air which is rich in carbon dioxide. The ribs move
downwards and inwards while the diaphragm moves upwards. This reduces the chest cavity and air is
forced out of the lungs. As the lungs reduce in size, air is expelled.
2. Roots: Roots absorb water along with dissolved oxygen and nutrients from the soil. The outer surface
of the roots has a thin layer of cells called epiblema. The air trapped between the soil particles diffuses
in the roots through these cells. Oxygen is taken in by the cells and carbon dioxide is given out which
diffuses into the soil.
Stems: The stems of the woody plants have openings called lenticels for gaseous exchange.
Leaves: Leaves have minute openings called stomata. In the daytime, the leaves perform photosynthesis
by taking in carbon dioxide and giving out oxygen. At night, when photosynthesis stops, leaves only
respire.
3. (a) Tiny openings present at the underside of the leaf which helps in gaseous exchange.
(b) Small openings in the bark of woody stems of plants which help in gaseous exchange
(c) The outer surface of the roots has a thin layer of cells called epiblema.
(d) A thin tube through which air enters into the lungs from nose
(e) It means to take in air which is rich in oxygen.
65
Chapter 10
Transport of Substances in Animals and Plants
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand the transportation of substances in animals
• know how transportation takes place in humans
• explain what blood contains
• know what are different types of blood vessels
• understand what is heartbeat and what is pulse rate
• explain how transportation takes place in plants
• understand transportation in plants
• know about excretory system in animals
• understand how excretion occurs in humans.
Warm Up
Ask students to complete the Warm-up section given in the chapter. What actually is the function of
the heart? How blood pressure is measured? If possible carry a sphygmomanometer (blood pressure
measuring instrument) and discuss its functions and utility in the class.
Concept Explanation
• Transport of substances: Explain to students how substances are transported by the process
of diffusion and osmosis in plants and animals. In humans, how blood is the main source of
transportation of substances. Tell them that blood contains blood plasma and blood cells.
Also explain to them the functions of the sub parts of blood cells.
• Blood vessels: How different types of blood vessels carry blood in and out of the heart.
• Heart: Explain to students that the heart is a pumping organ. Increase and decrease in the
heart beat is linked to the brain.
• Pulse: With the help of Activity 1, tell students how to measure pulse rate. Then with Activity
2, tell students to count pulse by means of stethoscope.
• Transportation in plants: Explain to students that xylem and phloem are meant for
transportation of substances in plants.
• Excretory system: With the help of Figure 10.4, explain the human excretory system and the
functions of nephrons.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
66
Worksheet 1
1. Define the following.
(a) Thrombocytes
(b) Leucocytes
(c) Veins
(d) Heart beat
(e) Pulse
(f) Vascular system
(g) Excretion
67
Worksheet 2
1. Label the given picture.
____________
____________
____________
____________
____________
____________
____________
____________
____________
____________
2. What is dialysis?
3. What are the waste materials excreted by the plants?
4. Define plasma.
68
Answers to Coursebook
A.
B.
1. (a) Veins
(b) Transpiration (c) Phloem
(d) Transpiration (e) Haemoglobin
2. WBC—Protects the body from infection
Blood platelets—Blood clotting
Nephron—Filtration of blood
Osmosis—Semi-permeable membrane
Heart—Pumping organ
1. Red blood cells are responsible for the transport of oxygen.
2. Nephrons
3. The heat rate increases because your heart needs to supply more oxygen to your muscles.
4. Due to transpiration, plants remove excess amount of water in the form of water vapour which
helps in transporting minerals through the plant.
5. Pulse: The heart beat is represented in our body in the form of the pulse rate. Each time, the heart
pumps the blood out, it rushes through the arteries and produces a twitching movement called
pulse.
Pulse rate: The number of pulse beats per minute is called the pulse rate.
6. If a person’s kidneys get damaged, doctors remove the body waste by means of a medical procedure
called dialysis or kidney transplantation. The dialysis machine is also called an artificial kidney.
In this process, blood from the artery of an arm is allowed to pass through the dialysis machine
through tubes. It is then filtered to remove excess of salts and urea. The filtered blood is then
transferred back to the body through a vein.
7. A kidney consists of millions of microscopic structures called nephrons. Each nephron consists of
glomerulus (tuft of capillaries) present inside the cup-shaped structure called Bowman’s capsule.
The capillaries filter the blood which passes through their walls.
8. Water evaporates from the leaves by the process of transpiration and generates a low pressure and
a pulling force that causes water to move up. In this way, water and minerals are transported from
the roots to different parts of the plant.
9. (a) Arteries: These are thick-walled vessels, which carry blood from the heart to different parts of
the body. They carry oxygenated blood which moves under high pressure. Arteries are placed
deep inside the skin and lack valves.
Veins: Veins are thin-walled vessels which carry blood from different body parts to the heart.
They carry deoxygenated blood and are located superficially below the skin. The blood does
not move under high pressure. Veins have valves to prevent the backflow of blood.
(b) Xylem vessels transport water and dissolved minerals from the roots to the stem and the leaves.
Phloem tubes carry the food prepared by the leaves to the other parts of the plant.
(c) Diffusion: It is the movement of gases, liquids or solid molecules from a region of their higher
concentration to a region of their lower concentration. For example, if perfume is sprayed in
one corner of the room, its smell reaches to other end of the room. This is diffusion.
Osmosis: It is the movement of solvent (water) particles from the region of its higher
concentration to the region of its lower concentration through a semi-permeable membrane.
For example, raisins soaked in water swell up due to the movement of water from outside the
raisins into them.
69
(d) Auricles refer to the upper chambers of the heart that receives the impure blood from the veins
to send it to the ventricles. On the other hand, ventricles are small cavities or chambers that are
present within an organ.
C. 1. The human body excretes wastes in the following ways.
Through sweat: Our body gets rid of urea, salts and water through sweat which is secreted by the
sweat glands present under the skin. Sweating helps in regulating the body temperature. It helps to
keep the body cool by helping body lose heat as sweat evaporates off the skin.
Through exhaled air: Carbon dioxide, formed after respiration, is sent out of the body with exhaled
air.
Through the kidney: The excretory system of human beings consists of the following organs.
A pair of kidneys A pair of ureters
Urinary bladder
Urethra
It is also called the urinary system. The excretory system of our body helps it to get rid of nitrogenous
wastes. Kidneys are the most important part of this system. A kidney consists of millions of
microscopic structures called nephrons. Each nephron consists of glomerulus (tuft of capillaries)
present inside the cup-shaped structure called Bowman’s capsule. The capillaries filter the blood
which passes through their walls. The useful substances such as glucose and some salts are absorbed
back while the nitrogenous waste is passed through it. The filtrate thus obtained is called urine.
It is mixed with water and is yellowish in colour. It contains salt, urea, and other waste materials.
The urine thus formed, passes through the ureters and gets collected in the urinary bladder. It is
discharged out of the body with the help of urethra. The concentration of various constituents in
the urine depends on the functioning of various organs or organ systems in the body. If the listed
substances are found in urine then it suggests a disease or improper functioning of the body.
Sugar – Diabetes
Blood – Disease or injury
Protein – Disease or injury
Bile – Jaundice
Excess urea or uric acid – Malfunctioning of kidneys
A healthy human being passes out about 1.5 to 2.5 litres of urine every day.
2. Refer to Figure 10.3 on page 136.
3. Xylem vessels transport water and dissolved minerals from the roots to the stem and the leaves.
Water evaporates from the leaves by the process of transpiration and generates a low pressure and a
pulling force that causes water to move up. This is similar to what happens when we drink juice or
water through a straw. In this way, water and minerals are transported from the roots to different
parts of the plant.
4. Blood is composed of three types of blood cells, namely, red blood cells, white blood cells and
platelets.
Red blood cells: Red blood cells or RBCs are also known as erythrocytes. Red blood cells have
a disc-shaped structure and they are red in colour due to the presence of haemoglobin protein.
Haemoglobin combines with oxygen and forms oxyhaemoglobin which carries oxygen to all parts
of the body. The life span of RBC is 120 days.
70
White blood cells: White blood cells or WBCs are also called leucocytes. These are colourless,
Amoeba-like large cells. They produce antibodies to fight against infection. They are less in number
than RBCs. They destroy disease-causing harmful bacteria and foreign materials.
Blood platelets: They are also called thrombocytes. These are smaller than RBCs. They are colourless
and irregular in shape. They help in the clotting of blood at the site of injury, thus blocking the fl ow
of blood and preventing blood loss.
5. The heart is a hollow, muscular, cone-shaped organ. It is a pumping organ which pumps blood
throughout the life of an individual without stopping. The heart is able to do so by the rhythmic
contractions and relaxations of its muscles. The heart is made up of cardiac muscles. It beats 60 to
80 times a minute throughout the life of an individual. The heart has four chambers—two auricles
and two ventricles. Auricles are chambers on the upper side and ventricles are chambers on the
lower side. The right auricle opens into the right ventricle and the left auricle opens into the left
ventricle.
D.
Refer to Figure 10.3 on page 136.
E.
1. Xylem and phloem are important because they transport substances to plants. Xylem transports
water and nutrients from the roots to all the parts and phloem transports food from the leaves to all
parts of the plant. Xylem and phloem are similar because they both transport substances in plants.
2. Vegetable tend to dry by losing water. When water is sprayed, the water enters vegetables due to
osmosis and keeps them fresh.
3. RBCs are red in colour due to the presence of haemoglobin protein in it and the number of RBC is
more than WBC. So in spite of having different constituents of different colours, blood appears red
in colour.
4. It is important to check blood group so that the blood of donor matches that of recipient. Mismatch
of bloods can lead to complications.
71
Answers to Worksheets
Worksheet 1
1. (a) Blood platelets are called thrombocytes.
(b) White blood cells are called leucocytes.
(c) Veins are thin-walled vessels which carry blood from different body parts to the heart.
(d) The rhythmic contraction and relaxation of the heart muscles constitute a heart beat.
(e) Each time, the heart pumps the blood out, it rushes through the arteries and produces a twitching
movement called pulse
(f) Plants have a well-developed transport system called the vascular system
(g) The process of the removal of wastes from the body is called excretion.
Worksheet 2
1.
Inferior vena cava
Aorta
Adrenal gland
Right kidney
Left Kidney
Renal vein
Renal artery
Ureter
Urinary bladder
Urethra
2. If a person’s kidneys get damaged, doctors remove the body waste by means of a medical procedure
called dialysis or kidney transplantation.
3. Oxygen, Carbon dioxide, Excess water, Excess salt, Gums, resins and latex.
4. The colourless fluid component of the blood.
72
Chapter 11
Reproduction in Plants
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand importance of reproduction in life
• know the difference between asexual and sexual reproduction
• explain different types of asexual reproduction
• explain what is vegetative propagation, its natural methods and artificial methods with
respect to root stem and leaves
• explain sexual reproduction in plants
Warm Up
To make the class interactive, ask students before hand to germinate gram seeds at home. Ask them
to bring the germinated seeds in the class. Now tell students to complete the exercise given in the
Warm-up section. Tell them how important is the process of reproduction for the life to go on this
earth.
Concept Explanation
• Reproduction: Explain how important this process is. Let them differentiate between
asexual and sexual reproduction. Tell them how fission differs from budding, sporulation
and fragmentation?
• Vegetative propagation: Explain to students how they can grow potato, coriander, rose at
home in a kitchen garden or pots. Tell them not only roots but stem, leaves and seeds all are
important for the growth of plants. Vegetative propagation can be done both by natural as
well as artificial means.
• Sexual reproduction: Tell students about the different parts of a flower. Bring a hibiscus
flower in class and dissect it in front of students. Then explain each and every part. Tell them
what are unisexual and bisexual flowers.
• Pollination: Explain to them how pollination occurs in plants and what are the different
agents of pollination. Also mention the role of bees they usually see sitting on the flowers.
• Dispersal of seeds: Tell students how seed is formed in plants. Also explain the germination
and dispersal of seeds.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life
skills sections of the chapter. Discuss the terms and their meanings given at the end of the
chapter. Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
73
Worksheet 1
1. What is fertilisation? Where does fertilisation take place in plants?
2. Unjumble the words.
(a) YAVRO
(b) AMGETE
(c) LILPONTION
(d) DBNDUIG
3. Label the given picture.
74
Worksheet 2
1. The mode of vegetative reproduction in which scion and stock are tied is called
(a) Layering
(b) Cutting
(c) Grafting
(d) Tissue culture
2. Fill in the blanks.
(a) _________develops into a new plant.
(b) Yeasts reproduce by __________.
(c) Fruit is generally ripened _________.
(d) Fusion of two gametes is called ___________.
3. Match the following.
Column A
Column B
Stems
Maple
Spores
Yeast
Bud
Potato
Wings
Rose
Eyes
Bread mould
4. Which type of stem is found in ginger?
5. Write any two examples of bisexual flowers.
75
Answers to Coursebook
A.
B.
B.
76
1. (a) F
(b) F
(c) F
(d) T
(e) F
2. Rizopus—mould
Hydrilla—water
Corm—gladiolus Layering—grapes
Budding—hydra
1. The transfer of pollen grains from the anther to the stigma is called pollination.
2. A flower in which four whorls, that is, sepals, petals, stamens and pistil are present. Example:
Hibiscus
3. Some algae such as Spirogyra multiply in number by this process. Fragmentation is a process where
a mature organism breaks up into small pieces. Each of these pieces or fragments can lead an
independent life like a new individual.
4. There is no genetic variation, hence the plants are less adaptive to the changing environment.
Neither can the new characters be introduced nor can the undesirable characters be eliminated.
5. When a seed is soaked in water or put in moist soil, it absorbs water and swells up. The enzymes
present inside the seed become active and help in the germination of the seed.
6. (a) Unisexual flowers consist of only one type of reproductive organ, that is, either male gamete or
female gamete. For example, papaya.
Bisexual flowers consist of both male and female reproductive cells called gametes. For example,
china rose, sunflower and rose.
(b) Wind pollination: The transfer of pollen grains takes place by wind. It occurs in those flowers
which are not brightly coloured and do not produce nectar. In the absence of large petal, the
anthers are exposed to the wind. This type of pollination takes place in grasses, corn and wheat.
Water pollination: The flowers of aquatic plants release pollen grains from their anthers in
water. The pollen grains reach the stigma of another flower by means of water currents. This
type of pollination takes place in water lily, Vallisneria and Hydrilla.
(c) The ovary is the swollen portion of the flower which contains the female gametes called ovules.
(d) Fission: It is the process by which a mature cell gives rise to two or more daughter cells. It
takes place during favourable conditions, that is, when there is abundant food supply. During
this process, the nucleus divides first followed by the division of cytoplasm. It takes place in
organisms such as Amoeba and Paramecium.
Budding: In budding, reproduction takes place by the formation of a small bud-like projection
or protuberance from the body. The nucleus of the parent body divides into two and one of the
nuclei moves into the bud. When the bud matures, it detaches from the parent and can exist
independently. For example, Hydra and yeast reproduce by budding.
(e) Self-pollination: When the pollen grains of one flower are transferred to the stigma of the
same flower, it is called self-pollination.
Cross-pollination: When the pollen grains of one flower are transferred to the stigma of
another flower of the same species, it is called cross-pollination.
1. The transfer of pollen grains from the anther to the stigma is called pollination.
2. After pollination, the stigma secretes a sugary, sticky fluid which helps the pollen grains to grow.
The pollen grains produce a thin tube which grows through the style and reaches one of the ovules
present in the ovary. The tube dissolves the wall of the ovule and discharges two male gametes in it.
One of the male gametes fuses with the egg present in the ovule. The process of fusion of male and
female gametes is called fertilisation. It results in the formation of a zygote. After fertilisation, most
parts of the flower wither away and a significant change occurs in the ovary. The ovary enlarges
to form the fruit. A fruit is the seed bearing part or the ripened ovary of the flower. The wall of
the ovary becomes the fruit wall. The ovules become the seeds. A seed is a ripened ovule which
contains the embryo and is covered by a protective coat. Petals, sepals and other parts of the flower
dry up and fall off .
3. Advantages of Vegetative Propagation
• The plants produced by vegetative methods grow or mature quickly than the plants produced
from seeds, as the seeds sometimes may not germinate due to unfavourable conditions. This
process of growing plants is quite economical.
• Seedless fruits are obtained through this process. Such fruits are usually preferred by us as we
can eat them without removing the seeds.
• New plants are identical to the parent plants which contain the desirable characteristics of the
parent plant.
• Desirable qualities of two varieties of plants can be combined through the process of grafting.
• The fruits obtained through these methods are of uniform quality, size and taste.
Disadvantages of Vegetative Propagation
• There is no genetic variation, hence the plants are less adaptive to the changing environment.
• Neither can the new characters be introduced nor the undesirable characters can be eliminated.
4. A seed is a ripened ovule which contains the embryo and is covered by a protective coat. The
dispersal of seeds and fruits takes place by the following ways.
• Dispersal by wind: Seeds which are small, light in weight and have tufts of hair or wings are
carried away to distant places by the wind. Seeds of maple, sunflower, madar, dandelion, cotton
and poppy are dispersed by wind.
• Dispersal by water: Fruits and seeds having special structures such as a spongy outer coat are
dispersed by water. For example, seeds and fruits of water lily, lotus and coconut are dispersed
by water.
• Dispersal by animals: Seeds and fruits which are edible or have hooks, stiff hair, spines, bristles
are dispersed by animals. Such seeds stick to the skin or fur of animals or clothes of human
beings and are carried to distant places. Animals and human beings eat the pulp of the fruit and
throw away the seeds at some distant place. Such seeds germinate and develop into new plants.
• Dispersion by explosion: Fruits like pea, violet, okra and mustard disperse their seeds by the
splitting of fruits. When the fruit ripens, seeds grow in size, thus splitting the fruit into two
halves with a small explosion. It leads to the dispersal of seeds.
5. It is a common method where a small piece of a stem of another plant is cut and is placed on
the stem of another plant which is rooted in soil. The inserted branch is called scion or graft
and the rooted part of the plant on which the cutting is attached is called a stock. The scion
and stock are tied together with a thread so that their cambium get fused into one. The stock
supplies water and minerals to the scion. New cells develop in the joining area and a new
variety of plant develops. This technique is very helpful in developing new varieties of plants
such as rose, mango and cherry.
77
6. Asexual reproduction is of the following types: fission, budding, fragmentation and spore
formation.
Fission: It is the process by which a mature cell gives rise to two or more daughter cells. During
this process, the nucleus divides first followed by the division of cytoplasm. It takes place in
organisms such as Amoeba and Paramecium.
Refer to Figure 11.1 on page 146.
Budding: In budding, reproduction takes place by the formation of a small bud-like projection
or protuberance from the body. The nucleus of the parent body divides into two and one of the
nuclei moves into the bud. When the bud matures, it detaches from the parent and can exist
independently. For example, hydra and yeast reproduce by budding. In case of yeasts, a chain
of buds can be formed, if it is not detached from the parent cell.
Refer to Figure 11.3 on page 147.
Sporulation or spore formation: Sporulation occurs in bacteria, fungi, moss and ferns.
During unfavourable climatic conditions such as scarcity of water and food or heat or dryness,
the plants produce reproductive spores. The spore is a small single-celled reproductive body
which is covered by a thick and hard protective coating. This protective layer helps it to survive
under unfavourable conditions. When the conditions become favourable, the thick coating
breaks open and spores germinate to produce a new plant. Bread mould or Rhizopus reproduces
asexually by growing on the surface of moist stale bread.
Refer to Figure 11.4 on page 147.
Fragmentation: Some algae such as Spirogyra multiply in number by this process.
Fragmentation is a process where a mature organism breaks up into small pieces. Each of these
pieces or fragments can lead an independent life like a new individual.
Refer to Figure 11.5 on page 148.
D.
Stigma
Petal
Petal
Anther
Filament
Style
Ovary
Ovule
E.
78
Carpel
Sepal
1. Zinnia plants do not require heavy irrigation and Rohit did just that by watering them regularly,
that’s why Zinnia plant failed to grow.
2. In order for pollination to occur, male and female cucumber plants are grown close to each
other.
3. Propagation of moderate and difficult-to-root species with rooting hormones may enhance
rooting percentages. Applied hormones also facilitate rooting where environmental conditions
are not ideal.
4. In Tuberose flowers, pollination occurs by insect such as hawkmoth.
Answers to Summative Assessment 1
A.
1. Clinical
2. 240 km
3. Spoon, water
4. It travels an unequal distance in equal intervals of time
5. Pressure
B.
1. Rhizobium
2. Stomach
3. (a) MgO + H2O  Mg(OH)2
(b) HCl + NaOH  NaCl + H2O
4. Magnesium oxide is formed which is of white colour.
5. The inner wall of the small intestine is covered with millions of finger-like projections called villi.
They increase the surface area for absorption.
C.
1. Stainless steel is a good conductor of heat while thermocol cup is not. Therefore, stainless steel
tumbler containing hot tea cannot be held in hand.
2. The air present in the boiling tube expands which results in the inflation of the balloon.
3. More layers of clothes act as insulator which do not let air in. Therefore, we feel warmer in more
layers of clothes.
4. In summer, white patches occur due to the salt present in sweat.
5. During rigorous exercise, anaerobic respiration takes place along with aerobic respiration.
Anaerobic respiration does not need oxygen:
Glucose  lactic acid
The waste product, lactic acid, builds up in the muscles causing pain and tiredness.
D.
1. During the day, the sun shines equally bright on the land and the sea. The land gets heated up
quickly as compared to seawater because land is a better conductor of heat. Air above the land gets
heated up and rises up. As a result, the pressure of air on the land decreases in comparison to the
seawater. Thus, air from the sea blows towards the land and causes sea breeze.
2. The mode of transmitting heat that requires no medium is known as radiation.
Applications of radiation: These are as follows.
• White and light-coloured clothes are comfortable to be worn in summers and dark-coloured
clothes are usually worn in winters. This is because light-coloured clothes absorb lesser heat
and keep us cool in summer. Dark-coloured clothes absorb more heat and keep us warm in
winters.
79
• The bottom of some cooking utensils is painted black whereas the sides are sparkling white.
Black-bottomed utensils absorb more heat and their sides are kept bright so that they do not
radiate or lose heat. Refer Experiment 5 on page 68.
3. Refer Experiment 4 on page 66.
4. Shearing: The removal of fleece from a sheep’s body is called shearing. The fleece is removed as one
layer using large scissors and electric shaving machines. Sheep are usually sheared once a year, but
sometimes they can be sheared twice a year too. Shearing is done in early summer so that they do
not feel the summer heat.
5. The rhythmic contraction and relaxation of the heart muscles constitute a heart beat. The contraction
and expansion of the heart muscles is linked with the circulation of blood; therefore, pumping
of heart can be heard as regular sounds. These are lub-dub sounds. Doctors hear and count the
heart beat of a patient with the help of a stethoscope. The colour of the blood is red because of the
presence of haemoglobin.
E.
Physical change: Characteristics of a physical change are as follows.
• Physical changes are generally reversible.
• Physical changes are temporary in nature.
• No new substances are formed.
• Energy, in the form of heat, light and temperature is neither absorbed nor evolved.
• During a physical change only the physical properties of the substance change.
Chemical change: Characteristics of a chemical change are as follows.
• A chemical change is permanent in nature and is irreversible.
• A new substance is formed which has different properties.
• Heat or light may be emitted or absorbed during a chemical reaction.
• A chemical change occurs only under particular conditions.
F.
1. Cuscuta (dodder) has yellow, thread-like stems which help it to climb over the stems and branches
of other plants. Its roots are called haustoria which pierce the host’s body to obtain nutrition.
2. The leaves of nepenthes (pitcher plant) are modified into a tubular pitcher-like structure. The apex of
the leaf forms a lid over the pitcher, which can be opened or closed. The inner surface of the pitcher
has hair directed downwards. When an insect enters the pitcher, the lid closes and the insect gets
trapped inside the pitcher. The insect gets digested by the digestive juices secreted in the pitcher.
G.
80
Refer to Figure 2.3 on page 24.
Answers to Worksheets
Worksheet 1
1. (a) The process of fusion of male and female gametes is called fertilisation. It occurs in ovary.
2. (a) OVARY
(b) GAMETE
(c) POLLINATION
(d) BUDDING
3.
Stigma
Petal
Petal
Anther
Filament
Style
Ovary
Ovule
Carpel
Sepal
Worksheet 2
1. (c) Grafting
2. (a) Embryo
(b) Budding
(c) Ovary
(d) Fertilisation
3. Stems—Rose
Spores—Bread mould
Bud—Yeast
Wings—Maple
Eyes—Potato
4. Rhizome
5. China rose, sunflower.
81
Model Test Paper 1
100 marks
A. Tick () the correct option.
5×1=5
1. Which of the following plants is reproduced by grafting method?
(a) Jasmine
(b) Rose
(c) Asparagus
(d) Mint
2. Which of the following animals breathe through spiracles?
(a) Fish
(b) Frog
(c) Cockroach
(d) Amoeba
3. Which of the following plants show symbiotic nutrition?
(a) Lichen
(b) Sundew
(c) Cuscuta
(d) Coral root
(c) Fe
(d) Ag
(c) Monkey
(d) Elephant
4. What is the symbol for silver element?
(a) Au
(b) Pb
5. Which of the following animals has blubber?
(a) Camel
(b) Penguin
B. Match the columns.
5×1=5
1. Strong base
(i) Rusting
2. Relative humidity
(ii) Chyme
3. Chemical change
(iii) KOH
4. Small intestine
(iv) Fungi
5. Saprophyte
(v) Hygrometer
C. Give two examples for each of the following.
2 × 5 = 10
1. Parasitic plants
2. Compounds
3. Application of radiation
4. Weak base
5. Plants reproduce by grafting
D. Differentiate between:
1. Wind pollination and water pollination
2. Arteries and veins
3. Horizon A and horizon B
4. Permanent adaptation and temporary adaptation
5. Acid and base
82
2 × 5 = 10
E. Answer the following briefly.
3 × 5 = 15
1. Explain the neutralisation reaction in the soil treatment.
2. Explain the reaction between copper sulphate and iron nail.
3. Explain the digestion process in ruminants.
4. What are the health hazards in sericulture?
5. What are the climate zones on the earth?
F. Answer the following in detail.
5 × 7 = 35
1. What are the adaptive features of chameleon?
2. What is percolation? How is percolation rate of water in soil determined?
3. What is breathing? Explain its steps.
4. What are the types of blood cells? Explain them.
5. Explain the functions of different organs of human respiratory system.
6. Explain the artificial methods of vegetative propagation.
7. Write the properties of salts.
G. Reeta took 1 kg garden soil in a pot and poured 650 mL water in it. The pot had a hole at its
base through which the water seeped out and got collected in another pot. She measured the
amount of collected water and found it to be 500 mL. Find the percentage of water absorbed
by the soil.
5 × 7 = 35
H. Look at the picture carefully and answer the following questions.
15
1. Which method of reproduction is being depicted in the picture?
2. Explain its process.
3. Write one more example of plant in which this method is the mode of reproduction.
83
Chapter 12
Time and Motion
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what time is and how it is measured
• know the different techniques by which ancient people used to measure or calculate time
• exlpain what is motion
• understand difference between slow and fast motion
• know about uniform and non-uniform motion
• know how distance and time can be represented by bar graph, pie graph and line graph
Warm Up
To start the topic, ask the questions given in the Warm-up section. Tell students about the importance
of each and every minute. Tell students about the relevance of time in daily life activities.
Concept Explanation
• Measurement of time: Explain the ways in which time can be measured by means of time
intervals. Also explain the methods that were used by the ancient people to measure time
such as hour glass, sundial, etc.
• Simple pendulum: Explain to the students how a small mass such as a stone or a metallic
bob which is suspended from a fixed point and allowed to swing freely under the influence
of gravity is called a simple pendulum. With the help of a bob and a thread suspended on a
stand, the amplitude of the pendulum can be calculated.
• Motion: Explain to the students when an object changes its position with time it is said to be
in motion.
• Speed: Explain to the students that when a body moves fast or slows down, we refer to it as
speed.
• Uniform and non-uniform motion: This can be explained with the help of distance-time
graph.
• Pie graph: Show them a circular chart divided into different sections and tell them that in
this way pie chart can be made.
84
• Bar graph: Tell students that it is a graph which is plotted on a graph paper. It displays the
data with the help of bars of different heights.
• Line graph: Line graph can be made on the blackboard by plotting the two variables on y and
x axis.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
85
Worksheet 1
1. Draw a distance-time graph for uniform speed.
2. Fill in the blanks.
(a) _____________ is an instrument used to measure time.
(b) The instrument used to measure the speed of a vehicle is _____________.
(c) A _____________ is a graphical display of data using bars of different heights.
(d) Speed of an object is defined as the _____________ travelled by it in unit time.
(e) _____________ is useful for displaying data or information that changes
continuously over time.
86
Worksheet 2
1. What is meant by uniform motion? A car travels a distance of 480 km in 6 h. Find
its speed in m/s.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
2. Match the following.
Column A
Column B
Speed
One oscillation
Km/h
Measure speed travelled
Odometer
SI unit
Time period
Distance-time graph
Speedometer
Measure distance travelled
3. How can one reduce the time period of a pendulum?
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
4. Define periodic motion.
_________________________________________________________________
5. What is the use of an odometer?
_________________________________________________________________
87
Answers to Coursebook
A.
B.
C.
88
1. (a) F
(b) T
(c) F
(d) T
(e) T
2. Speedometer—Speed of vehicle
Line graph—x and y axes
Simple pendulum—Time period
365 ¼ days—One year
Mean position—Rest position
1. All our activities are based on time. You go to school at a fixed time. You sleep at a fixed time. You
take meals at a fixed time. We cannot do without time.
2. If the body changes its position with time, it is said to be in motion.
3. 1 minute = 60 seconds
1 Hour = 60 minutes
1 Day = 24 hours
1 Year = 365 ¼ days
1 Decade = 10 years
1 Century = 10 decades (100 years)
1 Millennium = 10 centuries (1000 years)
One day is the time taken by the earth to complete one rotation on its axis. One year is the time
taken by the earth to complete one revolution around the sun.
4. (a) Uniform motion: When an object covers equal distances in equal intervals of time, the object
is said to move in uniform motion.
Non-uniform motion: A body is said to be in non-uniform motion when it travels an unequal
distance in equal intervals of time or vice versa.
(b) Speed: The distance travelled by an object in unit time.
Average speed: The rate of change in distance with respect to time.
1. Time period : The time taken by the bob to complete one oscillation is called its time period.
Amplitude: Amplitude is the maximum displacement of the bob from its mean position.
Oscillation: A repeating fluctuation in a physical object or quantity.
Refer to Figure 12.4 on page 165.
2. When an object covers equal distances in equal intervals of time, the
object is said to move in uniform motion.
• The motion of a body moving with a constant speed is called
uniform motion.
• The distance covered by a body is directly proportional to the time
taken.
• The distance-time graph shows a straight line.
For example, a car is moving at a uniform speed. The table below
shows the distance covered by the car with respect to time.
Distance (in metres)
0
5
10
15
20
25
Time (in seconds)
0
2
4
6
8
10
The table shows that the distance covered by the car in every 2 seconds is 5 metres. So this is a
uniform motion.
D.
E.
3. Distance = 320 km
Time = 6 h
Speed = Distance / Time = 320 / 6 = 53.33 km/h
Speed in m/s = 320 × 1000/ 6 × 3600 = 14.81 m/s
4. Speed = 140 km/h
Distance = 560 km
Time taken = Speed/Distance = 140/560 = 0.25 h = 900 s
The more the length of the string, the more time it will take to complete one oscillation. So, (i) will
move faster because speed is directly proportional to the time.
1. She can reduce the time period by shortening the length of the string.
2. Ravi says right because, bus is in motion not Ravi.
3. The coarseness of the sand, the bulb size and the neck width can change the time measured by
Priya.
Answers to Worksheets
Worksheet 1
1.
2. (a) Clock
(b) Speedometer
(c) Bar graph
(d) Distance
(e) A line graph
Worksheet 2
1. (c) Grafting
1. When an object covers equal distances in equal intervals of time, the object is said to move in uniform
motion.
Given, distance = 480 km = 480000 m
Time = 6 h = 21600 s
Speed = Distance/Time = 480000/21600 = 22.22 m/s
2. Speed— Distance-time graph
Km/h— SI unit
Odometer—Measure distance travelled
Time period—One oscillation
Speedometer— Measure speed travelled
3. By reducing the length of the wire.
4. The motion that repeats itself in equal intervals.
5. An odometer is used to measure the distance travelled by a vehicle.
89
Chapter 13
Electric Current and Circuits
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand what electric current is
• know the symbol of electric components
• understand the heating effect of current and its applications
• explain the magnetic effect of current and its applications.
Warm Up
To make the class interactive, ask students the different electric components and the symbols used.
Ask students how current can be produced by using a pencil cell, wire and a small bulb (can be
demonstrated).
Concept Explanation
• Magnets: Magnetic and non-magnetic materials and types of magnets should be discussed
with the students. Students should be asked to complete Activity 1 and discuss the activity in
the class.
• Electric current: Explain to students how electricity is generated in powerhouses, and tell
them how electric current flows by means of wires and reaches our homes.
• Heating effect of current: If one wants to hold a glowing bulb, he or she requires cloth as the
bulb gets heated up. Experiment 1 will help students to understand it further.
• Magnetic effect of current: With the help of Experiment 2, students can be explained how
deflection of compass needle occurs when current flows in a circuit.
• Solenoid: Tell students that it is an electromagnet which generates a controlled magnetic
field.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
90
Worksheet 1
1. Write the names of the electric components these symbols represent.
Electric component
Symbol
(a) _________________________
(b) (i) ________ (ii) ________
(i)
(ii)
(c) _________________________
(d) _________________________
(e) _________________________
(f) _________________________
91
Worksheet 2
1. Write the components of an electric bell.
________________________________________________________________
________________________________________________________________
________________________________________________________________
2. Define the following.
(a) Electric circuit
____________________________________________________________
____________________________________________________________
(b) Filament
____________________________________________________________
____________________________________________________________
(c) Electric fuse
____________________________________________________________
____________________________________________________________
(d) Electromagnet
____________________________________________________________
____________________________________________________________
(e) Solenoid
____________________________________________________________
____________________________________________________________
92
Answers to Coursebook
A.
B.
C.
1. (a) increasing
(b) battery
(c) iron
(d) circuit
(e) hammer
2. Cell—Source of electric current.
MCB—Heating effect of current
Fuse—Breaks when excess current flows
Electromagnet—Electric bell
Open circuit—NO current flows
1. (a) When the circuit is not complete, electric current will not flow.
(b) Electric bulb is hot to touch due to the heating effect of electric current.
(c) Fuse is a safety device that prevents the overheating of electric circuit and prevents fires, so it is
a necessary evil.
(d) This wire is made of material that melts quickly and thus breaks the circuit. When a large
amount of current passes through the circuit, this wire gets heated up and melts away.
2. (a) Open circuit: In this circuit, the electric current will not flow.
Closed circuit: In this circuit, the electric current will flow.
(b) MCB: It is an automatically operated electric switch which turns off the supply of current by
switching itself off.
Fuse: It is a safety device which breaks if more than required amount of electric current passes
through the circuit.
3. When an electric current flows through metal wires, usually the wires get heated up. You must have
observed that if someone wants to hold the glowing electric bulb, he/she holds it with a piece of
cloth as the bulb gets heated up because electric current flows through it continuously.
1. Electric fuse is a safety device which prevents the overheating of the electrical circuit and prevents
fires. In our home also we have an electrical fuse which breaks if more than the required amount
of electric current passes through the circuit. It cuts off the supply of the electric current, thus
preventing further damage.
Principal of an electric fuse: Electric fuse is a wire usually placed inside a glass or a ceramic
cartridge. This wire is made of material that melts quickly and thus breaks the circuit. When a large
amount of current passes through the circuit, this wire gets heated up and melts away. Thus, the
circuit is broken and further damage to the electrical appliances is prevented. We say that the fuse
‘blows’. Nowadays, we use miniature circuit breaker (MCB) which is an automatically operated
electric switch which turns off the supply of current by switching itself off. The supply can be
restored by simply switching it on.
Key Electric lamp
2.
Resistor
Cell
3. Working of an electric bell
Step 1: When you push the switch of the bell, an electric current flows to the electromagnet.
Step 2: The electromagnet attracts the soft iron strip. The hammer attached to the strip then hits the
gong, making it ring.
93
4.
5.
D.
E.
6.
1.
2.
Step 3: As the soft iron strip gets attached to the electromagnet, it does not touch the screw, and
hence, the circuit is broken. This turns off the electromagnet and it can no longer attract the soft
iron strip. The soft iron strip returns to its initial position and touches the screw. This results in the
circuit being completed and current starts flowing again.
When steps 1 to 3 are repeated in quick succession, we hear the continuous ring of the bell.
When an electric current is passed through a coil of insulated wire wrapped around a piece of iron,
the iron exhibits the properties of a magnet. The magnet made using such an arrangement is called
an electromagnet.
Uses of Electromagnets:
Electromagnets are used on cranes, in scrap yards and in the steel industry for lifting heavy loads.
They are also used to separate magnetic substances from non-magnetic ones and in scrap yards.
They are used in telephones, speakers, audio, video tape recorders and electric bells.
A solenoid is a coil wound into a tightly packed helix. A solenoid is a type of electromagnet whose
purpose is to generate a controlled magnetic field. When current is passed through such a coil, it
acts like a bar magnet. A solenoid acts like a strong magnet in the following cases.
Wire is wound over an iron core.
The number of turns of wire per unit length of the solenoid is increased.
Strong current is passed through its coil
The circuit is not complete or the bulb is damaged.
Refer to Figure 13.3 on page 182
No, we cannot use copper wire because its melting point is very low as compared to the tungsten.
When the current will flow, it will melt.
(a) Wire A will be the best for the fuse that will allow more current to pass through.
(b) Wire B will be the best when the current is less.
Answers to Worksheets
Worksheet 1
1. (a) Electric cell
(b) (i) Off electric bulb (ii) On electric bulb
(c) Switch in OFF position
(d) Switch in ON position
(e) Battery
(f) Wire
Worksheet 2
1. Electromagnet, Strip spring, Armature, Contact screw, Hammer, Gong, Switch, Battery
2. (a) A closed path through which electric current flows when the switch is in a closed position.
(b) A lose spiral of a very thin wire of high melting alloy or metal.
(c) A safety device which prevents damage to the electrical appliance.
(d) A coil of insulated current-carrying wire wound around a soft iron core.
(e) A solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.
94
Chapter 14
Wind, Storm and Cyclone
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• know the characteristics of air
• understand what are storms and thunderstorms
• understand the characteristics of wind
• know cyclones and tornadoes
• know the safety measures during storms.
Warm Up
Ask students to complete the exercise given in the Warm-up section. Ask students whether they
have experienced any kind of storm or thunder.
Concept Explanation
• Wind: Ask students what is wind. How can they differentiate between air and wind? Tell them
that the movement of air is called wind which is caused due to the difference in temperatures
between the different regions of the earth.
• Air: Ask students to recapitulate the concepts studied in previous classes. Ask them about
the properties of air. Tell students why a chapatti inflates when it is heated. With the help of
Experiments 1 and 2, properties of air can be explained.
• Characteristics of wind: Tell students that direction and speed are the two main characteristics
of wind. The direction of wind is measured with the help of a wind vane while speed can be
measured with the help of a cup anemometer.
• Storms: Tell students the difference between the wind and storm. Storm is the atmospheric
disturbance accompanied by strong winds.
• Thunderstorm: Tell students that thunderstorm is caused due to moisture, rising warm air
and sea breeze. Ask students about sea breeze. Also mention the precautions that one should
take during a thunderstorm.
• Cyclone: Cyclones are huge and powerful storms which generally develop over waterbodies.
Tell students about the formation of cyclones and the destruction caused by them.
• Tornadoes: Tell students that the storms formed on land are called tornadoes. Also mention
the safety measures that one should take during tornadoes.
95
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
96
Worksheet 1
1. Define the following.
(a) Storm
____________________________________________________________
____________________________________________________________
(b) Thunder
____________________________________________________________
____________________________________________________________
(c) Hurricanes
____________________________________________________________
____________________________________________________________
(d) Water spouts
____________________________________________________________
____________________________________________________________
(e) Cyclone
____________________________________________________________
____________________________________________________________
(f) Anemometer
____________________________________________________________
____________________________________________________________
(g) Wind vane
____________________________________________________________
____________________________________________________________
97
Worksheet 2
1. What are the characteristics of air?
______________________________________________________________
______________________________________________________________
______________________________________________________________
2. Write an experiment that shows air expands on heating.
______________________________________________________________
______________________________________________________________
______________________________________________________________
3. What precautions need to be taken care during a thunderstorm?
______________________________________________________________
______________________________________________________________
______________________________________________________________
4. What is the difference between a tropical cyclone and an extra tropical cyclone?
______________________________________________________________
______________________________________________________________
______________________________________________________________
5. Write the safety measures to be adopted during storms.
______________________________________________________________
______________________________________________________________
______________________________________________________________
98
Answers to Coursebook
A.
B.
C.
1. (a) Typhoon
(b) Cyclone
(c) Tropical storm
(d) Extra tropical cyclone
(e) Eye
2. Direction of wind—Wind vane
Anemometer—Speed of wind
Warm air—Lighter
Cold air—Heavier
Cyclone in mind-latitudes—Extratropical cyclones
1. (a) Thunderstorm: The movement of falling water along with the rising warm air produces heavy
rain, lightning, and strong wind. It is called a thunderstorm.
Cyclone: It is a small low-pressure system with very high speed winds revolving around it.
(b) Storm: Storms are severe atmosphere disturbances accompanied by strong winds blowing at a
very high speed.
Wind: Movement of air (usually in a horizontal direction) is called wind. Wind is caused due
to the difference in temperatures between the different regions on the earth.
(c) Tornadoes: Storms formed suddenly on land are called tornadoes. This type of storm has the
highest wind speed on the earth, about 500 km/h.
Hurricanes: In North America, severe atmosphere disturbances accompanied by strong winds
blowing at a very high speed are called hurricanes.
2. If the wind speed of the storm is between 63 km/h–87 km/h, then it is called a tropical storm.
3. The pressure exerted by air at any point on the earth is called atmospheric pressure.
4. Wind is caused due to the difference in temperatures between the different regions on the earth.
5. (a) The rain-bearing winds are called monsoon wind.
(b) Storms are severe atmosphere disturbances accompanied by strong winds blowing at a very
high speed.
(c) In North America, severe atmosphere disturbances accompanied by strong winds blowing at a
very high speed are called hurricanes.
1. • A cyclone is a small low-pressure system with very high speed winds revolving around it.
• When the rays of the sun fall on the surface of the sea, the air over the sea and ocean gets heated
and the water evaporates. The warm air containing water vapour rises upwards and forms a low
pressure region. As the warm air rises, it gets cooler. As a result, the water vapour condenses
to form raindrops. During condensation, heat is released and the air around it gets warm.
This warm air rises upwards, creating a low pressure region. Cooler air rushes to fill the space
created by the rising warm air. This cycle of events continues till a very low pressure system
is formed with very high speed winds revolving around it leading to storms. This is called a
cyclone. If the wind speed of the storm is between 63 km/h–87 km/h, then it is called a tropical
storm. A cyclone has a wind speed of more than 120 km/h.
• The centre of the storm or cyclone is a calm, cloudless area which is called the ‘eye’ of the storm.
Its diameter may vary from 10 km to 30 km. There is no rain and the wind is fairly light.
• At the periphery of the cyclone, strong winds of about 150-250 km/h blow along with heavy
rains and thick clouds form around the eye of the cyclone.
• Wind speed, wind direction, temperature and humidity are all factors that contribute to the
development of cyclones.
2. No, we would not prefer to go for such house because ventilators are the important part of a house
as the air gets circulated in the house through these.
99
3. Precautions to be observed during a thunderstorm
• Do not take shelter under an isolated tree. If you are in forest, take shelter under a small tree.
Do not lie down.
• Do not take shelter under an umbrella with a metallic handle.
• If you are in a swimming pool, come out and go inside the building, that is, keep away from
waterbodies.
• Do not take shelter under a metal shed.
• Do not sit near an open window.
• Do not touch or operate any electrical appliance or telephone.
• Switch off the TV.
4. • When a cyclone hits an area, it causes widespread destruction of property and life. Some of its
effects are listed on the next page.
• The low pressure area in the eye of the cyclone lifts water up to a height of 12 m. It appears as
a wall of water. This wall of water enters low-lying coastal areas, resulting in severe loss of life
and property.
• It leads to soil erosion, i.e., the top fertile layer of the soil is swept away with water currents.
• High-speed wind damages buildings, disrupts telephone and electricity supply and uproots
trees.
• Cyclones push water, thereby producing water waves, causing floods. These water waves are
very powerful.
Safety measures to survive during these storms are as follows.
• Cyclone shelters must be constructed in cyclone-prone areas. Proper arrangements should be
made for quick evacuation of people.
• Remove any loose roofing items, dead trees and branches which can cause accidents during a
cyclone storm.
• Listen to TV and radio weather bulletins regularly.
• Keep phone numbers of hospitals, government agencies such as fire brigades and police, and
friends and relatives handy.
• Keep dry food items, safe drinking water, torches and emergency first aid medicines with you.
5. Refer Experiment 1 on page 188.
D.
1. Tornado
2. It will damage buildings, disrupt telephone and electricity supply and also will uproot trees.
E.
1. Cyclones are primarily formed over waterbodies. They weaken over the land as they are cut-off
from their primary energy source, the waterbody.
2. The earth rotates on its axis from west to east. This rotation causes both the wind and ocean
currents to move from east to west. But if the earth were to rotate from east to west, then the wind
circulation pattern will be reversed.
3. After prediction, cyclones and tornadoes cause a lot of harm to lives because of the lack of
preparedness for proper evacuation and lack of proper arrangements.
4. The boat will go in the direction in which the wind blows. So, the boat will not move in the direction
opposite to the wind.
100
Answers to Worksheets
Worksheet 1
1. (a) Storms are severe atmosphere disturbances accompanied by strong winds blowing at a very high
speed.
(b) Loud sound is called thunder.
(c) Tropical cyclones originating in the Gulf of Mexico, the Caribbean Sea and Western Pacific Ocean
are known as hurricanes.
(d) Tornadoes formed over the sea are known as water spouts.
(e) Cyclones are huge and very powerful storms. They generally develop over waterbodies such as
oceans and seas located in warm areas.
(f) An instrument used to measure wind speed
(g) An instrument used to find wind direction.
Worksheet 2
1. Air has pressure.
Air expands on heating.
Air moves from a region of high pressure to a region of low pressure.
2. Materials required: A balloon, a glass bottle, trough, hot water and cold water
Procedure: • Take a balloon and place it on the mouth of the bottle.
• Keep this bottle in a trough containing hot water.
• After some time, the balloon gets bigger in size, that is, it gets inflated.
• Now, replace the hot water with cold water.
Observation: When the bottle is kept in a trough of hot water, the balloon expands. When the bottle along
with the balloon is kept in cold water, the balloon wrinkles. This shows that air expands on
heating and contracts on cooling.
3. • Do not take shelter under an isolated tree. If you are in forest, take shelter under a small tree. Do not
lie down.
• Do not take shelter under an umbrella with a metallic handle.
• If you are in a swimming pool, get out and go inside the building, that is, keep away from waterbodies.
• Do not take shelter under a metal shed.
• Do not sit near an open window.
• Do not touch or operate any electrical appliance or telephone.
• Switch off the TV.
4. Cyclones that originate and travel in the tropics are called tropical cyclones. Cyclones that originate and
travel in mid-latitudes are called extra tropical cyclones.
4. • Keep dry food items, safe drinking water, torches and emergency first aid medicines with you.
• Do not venture into the sea once a warning has been issued. Stay indoors as much as possible.
• As soon as the warning is broadcast, secure your home or move to safer places.
• Do not drive on roads which are under water. The floods might have damaged the road.
• Listen to TV and radio weather bulletins regularly.
101
Chapter 15
Light
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• understand the reflection of light
• know what mirrors are
• learn the formation of images
• understand about the lenses and prism
• understand the concept of rainbow
Warm Up
Ask students to do the activity given in Warm-up section and tell them to write their observations.
The topic can be started by putting off all the lights and closing the windows of the classroom. Now,
teacher will light a torch and ask students what do they observe.
Concept Explanation
• Light: Tell students that light travels in a straight line. This property can be explained with the
help of Experiment 1. Also ask students how are they able to see things. What is the concept
behind this? Tell them that we are able to see things due to reflection.
• Mirror: Tell students that mirrors are highly polished reflecting surface. Ask students what
do they observe when they see themselves in the mirror. Tell students about the types of
mirrors. Tell students about the types of images formed by the plane mirror.
• Spherical mirror: Tell students that these are the spherical mirrors. These are of two types,
namely, concave mirror and convex mirror. Also mention the properties of images formed by
both of these mirrors. Also explain the daily life uses of these mirrors.
• Lens: Explain this topic by giving the example of a hand lens. Tell students that lenses are
of two types, namely, convex lens and concave lens. Also mention the properties of images
formed by these two lenses.
• Prism: Explain the concept of prism with the help of a rainbow. These both depend on the
concept of dispersion of light.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
102
Worksheet 1
1. Differentiate between:
(a) Plane mirror and curved mirror
______________________________________________________________
______________________________________________________________
(b) Real image and virtual image
______________________________________________________________
______________________________________________________________
(c) Concave mirror and convex mirror
______________________________________________________________
______________________________________________________________
2. Draw the image formed when
(a) The object is far from the concave lens
(b) The object is far from the convex lens
3. What do you mean by lateral inversion?
_________________________________________________________________
103
Worksheet 2
1. Which type of reflection is shown by each of the given pictures?
(a)
(b)
Rough
surface
Smooth
surface
_______________________
_______________________
2. Write some uses of the following.
(a) Concave mirror
_____________________________________________________________
(b) Plane mirror
_____________________________________________________________
(c) Convex mirror
_____________________________________________________________
3. Write the position of the image formed by a convex lens when the object is
104
(a) Between the lens and the focus
____________________
(b) At 2F
____________________
(c) At infinity
____________________
(d) At F
____________________
Answers to Coursebook
A.
B.
C.
1. (a) T
(b) F
(c) F
(d) F
(e) T
2. Lateral inversion—Plane mirror
Concave lens—Diverging lens
Plane mirror—Used in periscope
Dispersion of white light—VIBGYOR
Car headlight—Concave mirror
1. (a) Old people suffer from long-sightedness, therefore, they use convex lens.
(b) Concave mirrors are used by dentists because at a short range (object distances less than the
focal length) they produce magnified, upright images. It is useful to have a magnified image of
a tooth when you're looking for or repairing cavities, cracks, or other abnormalities.
(c) We cannot see a light source through a bent tube because light travels in a straight line.
2. (a) Concave mirror: A mirror in which the hollow inner surface functions as a reflecting surface
is called a concave mirror.
Convex mirror: A mirror in which the outer bulging surface functions as a reflecting surface
is called a convex mirror.
(b) Real image: If the rays of light emitted from an object actually meet at one point after reflection,
a real image is formed. A real image is always inverted, may be of the same size as the object or
bigger or smaller than the object. It can be obtained on a screen.
Virtual image: If the rays of light do not actually meet at a point after reflection but appear to
meet at a point behind the screen, a virtual image is formed. A virtual image is always erect,
and may be of the same size, or bigger or smaller than the object. It cannot be captured on a
screen.
(c) Concave lens: It is thin at the middle and gradually becomes thicker at the edges. When a
parallel beam of light passes through a concave lens, it spreads or diverges.
Convex lens: This lens is thick in the middle and becomes thinner towards the edges. For
example, magnifying lenses. When a parallel beam of light passes through a convex lens it
bends and narrows down at a point on the principle axis.
(d) Reflection: The bouncing of light rays by a surface is called reflection of light.
Refraction: Refraction is the bending of a wave when it enters a medium where its speed is
different.
3. We should use a plane mirror to get a clear image.
4. Concave lens always produces a diminished image.
5. The image will be formed beyond 2F and it will be inverted, magnified and real.
1. When the object is placed very near a mirror, then the image formed is virtual and cannot be
obtained on a screen. It is erect, bigger than the object and formed behind the mirror.
Refer to Figure 15.8 on page 205.
2. Light: Light is a form of energy which enables us to see objects around us.
Reflection: The bouncing of light rays by a surface is called reflection of light.
Image: An impression of an object formed when a ray of light falls on a mirror and gets reflected,
is called an image.
105
3.
4.
5.
D.
E.
1.
2.
A smooth surface reflects light uniformly in one direction. This is called regular reflection. An
irregular or a rough surface reflects light in different directions. This is called irregular or diffused
reflection.
Left-Right Inversion of the image: As the name suggests, images are laterally inverted, that is,
the right part of an object appears as the left in the image and vice versa. For example, the word
AMBULANCE is painted left-right inverted on the ambulance, so that when the driver of a vehicle
in front looks into his rear-view mirror, he can read the word AMBULANCE quickly and give way
to it.
Uses of a concave mirror
1. A concave mirror is used by the dentists to observe the teeth carefully.
2. It is used while shaving to see an enlarged and erect image of the face.
3. It is used in the solar cooker and as radiation collectors in solar heating devices.
Uses of a convex mirror
1. As a reflector in street lights
2. As a rear view or side view mirror in vehicles
3. Vigilance mirrors in big shops to look out for shoplifters.
If the light rays emerging from the other face of the prism are made to fall on a white sheet of paper
or a white wall, we can observe different components of white light in the form of different colours
separately. Thus, the colours are said to have dispersed after passing through the prism.
In the first case, convex mirror is used and the image will be erect, virtual and smaller.
In the second case, convex mirror is used and the image will be virtual, erect and very small in size.
To get the proper estimation of the distance it is written in the mirror. Convex mirror is used in
vehicles.
The image will be same because the image will not depend on the size of mirror.
Answers to Worksheets
Worksheet 1
1. (a) Plane mirror: This type of mirror has a highly polished flat surface to reflect light rays. A steel plate,
a shiny surface or still water can also act like a plane mirror.
Curved mirror: This type of mirror has a curved reflecting surface. These type of mirrors are also
called spherical mirrors or parabolic mirrors. Concave and convex mirrors are examples of curved
mirror.
(b) Real image: If the rays of light emitted from an object actually meet at one point after reflection, a
real image is formed. A real image is always inverted, may be of the same size as the object or bigger
or smaller than the object. It can be obtained on a screen.
Virtual image: If the rays of light do not actually meet at a point after reflection but appear to meet at
a point behind the screen, a virtual image is formed. A virtual image is always erect, and may be of
the same size, or bigger or smaller than the object. It cannot be captured on a screen.
(c) Concave mirror: A mirror in which the hollow inner surface functions as a reflecting surface is
called a concave mirror.
106
Convex mirror: A mirror in which the outer bulging surface functions as a reflecting surface is called
a convex mirror.
2. (a)
Rays
coming
from a far
off object,
(say the
sun)
Image
F
2F
(b)
Rays coming from
a far off object
F
Image
3. The phenomenon in which the right part of an object appears as the left in the image and vice versa.
Worksheet 2
1. (a) Diffused reflection
(b) Regular reflection
2. (a) • It is used in the headlights of the car.
• It is used in search lights and torchlights.
(b) • It is used as a looking glass.
• It is used in periscopes.
(c) • As a reflector in street lights.
• As a rear view or side view mirror in vehicles.
3. (a) On the same side of the lens as the object
(b) At 2F
(c) At infinity
(d) At F
107
Chapter 16
Water: An Important Resource
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• know about the sources of water
• understand the forms of water
• explain the uses of water
• know what is the natural distribution of water
• know the factors that are responsible for the scarcity of water
• learn how to conserve water
Warm Up
Ask students what percentage of earth is made of water. Tell them to complete the exercise given
in the Warm-up section. Now based on this, ask students about the percentage of groundwater,
freshwater.
Concept Explanation
• Water: Tell students about the composition of water molecule. Also mention the availability
of water on the earth. Tell students about the forms of water such as ice, water and steam by
giving daily life examples.
• Water cycle: Ask students if they know what water cycle is. Explain the different steps of
water cycle with the help of Figure 16.2. Also mention the uses of water such as domestic
uses, agricultural uses and industrial uses.
• Sources of water: Explain to students about the different sources of water. Tell them that rain
is the major source of water. Also explain about the surface water. Now ask students about the
availability of water in India with the help of Figure 16.5.
• Dam: Ask students if have they ever seen the Bhakra dam? If they have then ask about the
uses of dams. Why dams are built? Tell students about the main dams of India.
• Conservation of Water: Tell students that if we do not use water judiciously then water will
be depleted. This scarcity of water can be seen in desert regions. Ask students to mention the
steps to conserve water.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
108
Worksheet 1
1. What is being depicted in the given picture?
______________________________________________________________
2. What are the different forms of water?
______________________________________________________________
______________________________________________________________
3. Write the names of any five dams of India.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
4. Write any two factors that are responsible for the depletion of water.
______________________________________________________________
______________________________________________________________
109
Worksheet 2
1. What is being depicted in the given picture?
______________________________________________________________
2. Write the sources of water.
______________________________________________________________
______________________________________________________________
3. Draw an outline diagram of a rainwater harvesting system.
110
Answers to Coursebook
A.
1. (a) T
(b) F
(c) F
2. Sewage—Pollution of water sources
Condensation—Cooling of cloud to form rain
(d) T
(e) F
Freshwater—Aquifer
Drought—Leads to scarcity of water
Evaporation—Water vapour
B.
1. Rain, rivers, lakes, seas, oceans are the major sources of water.
2. Drinking and agriculture are the two major uses of pure water.
3. Dams are used to retain water and also to produce electricity.
4. Few days forecast charts can help us to check floods.
5. (a) Rainwater is the biggest source of water, so we need to conserve rain water.
(b) All living things need water for their survival. So, shortage of water could ultimately be
responsible for the death of all life forms on the earth.
6. (a) A layer of rock in which groundwater collects.
(b) The upper level of the groundwater is called water table.
(c) The water flowing or collected on the earth’s surface is called surface water.
(d) The water stored under the ground where the soil is completely filled or saturated with water.
7. Precipitation: It is any product of the condensation of atmospheric water vapour that falls on the
earth. The main forms of precipitation include drizzle, rain, sleet, snow and hail.
Condensation: Condensation is the change of water from its gaseous form (water vapour) into
liquid water. Water vapour condenses to form cloud droplets.
C.
1. It is important to realise that groundwater is not a resource that could be utilised indiscriminately
simply because it is available in abundant quantities. Problems and issues such as waterlogging,
salinity, agricultural toxins, and industrial effluents, all need to be properly managed so that we can
use our water resources for a long time. During the last decade, there has been a rising awareness
among the common people for the need to conserve groundwater. Water usage has to be integrated
effectively with steps for water regeneration which are as follows.
Recycling of water: Rainwater can be collected and used for cleaning purpose.
Fixing leaks and dripping taps: A dripping tap can result in the loss of up to 72 litres of water
every day.
Improvised methods for irrigation: In a technique called drip irrigation, watering of plants is
done drop-by-drop. This saves a lot of water.
Rainwater harvesting: In this method, special structures are designed to store rainwater and use
it for irrigation. In the southern states of India, tanks, artificial ponds, and reservoirs have been
constructed as a part of the water harvesting system.
2. It is defined as a situation when the amount of water present in an area is insufficient to meet the
needs of people living in the area. Being a renewable resource, we pay very little attention towards
the judicious use of water. As a result, with time, a water deficit develops in the area. The factors
responsible for the depletion of water are as follows.
111
• Increasing pollution: As a result of increasing population, more and more houses, shops, roads,
offices, etc., are using water to fulfil their needs. This, in turn, increases the usage of water and
more amount of wastewater is being produced. Moreover, urbanisation leads to the usage of
concrete and cement which prevents the surface water to seep into the ground.
• Increasing industries: Most of the stages of manufacturing processes in industries require
water. As the number of industries increases, the water required by them also increases which
contributes to the depletion of the water table.
• Deforestation: Trees have the ability to hold water. Due to deforestation, the number of plants
decreases. Hence, the water keeps flowing towards the sea, and the groundwater is not recharged.
• Agricultural activities: India is an agricultural country and agriculture is impossible without
water. Water for agriculture is mainly obtained from groundwater, rainwater, rivers and canals.
As the rainfall pattern is erratic in many places, agriculture cannot entirely depend on the
availability of rainwater. Also, canal water is available in a few places only. Therefore, groundwater
is the main source of water for agricultural activities and this causes further depletion of the
water table.
• Pollution of freshwater resources: It is caused when wastewater from industries and sewage
from households are allowed to enter the rivers and other water sources without treatment. The
runoff water from agricultural areas is polluted with pesticides and other chemicals. Due to this,
with time, many waterbodies are becoming unfit for use.
• Uncontrolled extraction of groundwater: Easy availability of borewell technology has led to
the uncontrolled extraction of groundwater. Due to this, the water table in many places is falling
sharply and leading to groundwater crisis in many places.
• No effective means of water conservation: Very little has been done to conserve freshwater
sources.
3. A dam is a barrier or an artificial wall built over a river. A reservoir is made behind the dam
which is used for the storage of water which can be evenly distributed among locations. Dams
generally serve the primary purpose of retaining water. Dams also help to generate electricity. The
Brahmaputra, Ganges and Indus basins contribute about 80 per cent of electricity generation.
4. Water is used for domestic, industrial and agricultural purposes. India has a typical monsoon
climate. In most parts of India, rainfall occurs under the influence of the southwest monsoon,
between June and September. However, in the southern coastal areas, near the East Coast (Tamil
Nadu and adjoining areas), much of the rainfall occurs under the influence of the northeast
monsoon, during the months of October and November. The average annual rainfall is estimated
at 1170 mm over the country which varies significantly from place to place.
• In Rajasthan, the average annual rainfall is lower than 150 mm/year.
• In the areas extending from Central Maharashtra to Tamil Nadu, parts of Andhra Pradesh and
Karnataka, the average annual rainfall is generally lower than 500 mm/year.
• More than 10,000 mm of rainfall occurs on the Khasi hills in the North East part of the country
during a period of four months.
• In the states of Assam, Meghalaya, Arunachal Pradesh and parts of sub-Himalayan West Bengal,
the average annual rainfall is about 2500 mm.
• Except in the north western part of India, the inter-annual variability of rainfall is relatively low.
In general, the northern half of the country sees greater extremes in rainfall.
112
D.
E.
The Himalayan rivers, namely, Ganges, Brahmaputra and Indus are formed by the melting of
snow and glaciers as well as rainfall. Therefore, these rivers have a continuous flow throughout the
year. These rivers account for a major proportion of India’s water resources. Water in these rivers
is strongly influenced by the monsoons. As these regions receive very heavy rainfall during the
monsoon period, the rivers swell up and cause frequent floods. At the same time, during summer,
the water levels drop to significantly low levels. To regulate the water flow in these rivers and
distribute water more evenly throughout the year, a large number of dams are built on a number of
rivers.
Mountain regions of northern areas of our country do not allow adequate seepage of water.
Therefore, most of the groundwater is mostly collected in low-lying areas, such as valleys. The
peninsular areas of our country also do not allow proper absorption of water and do not have large
continuous aquifers. Coastal plains are a rich source of groundwater but they can be contaminated
by salt water inflow caused by overpumping of groundwater.
5 Rainwater harvesting: In this method, special structures are designed to store rainwater and use
it for irrigation. In the southern states of India, tanks, artificial ponds, and reservoirs have been
constructed as a part of the water harvesting system.
Due to scarcity of water, it is not available everywhere especially in deserted conditions. So, people
go to far places and bring water in pots. By rainwater harvesting and by making water reservoirs
this condition can be improved.
1. Water obtained from rain is not good for consumption as such. Also, in Mawsynram, good
rainwater harvesting system is not present, So, Mawsynram gets maximum rainfall but still it faces
water shortage
2. The lowering of the level of water table is the prime reason behind this.
Answers to Worksheets
Worksheet 1
1. Water cycle
2. Solid (ice), Liquid (water), Gas (steam).
3. • Nagarjuna Sagar Dam on the Krishna River
• Bhakra Dam on the Sutlej River
• Hirakud Dam on the Mahanadi River
4. Increasing pollution and deforestation.
Worksheet 2
1. Purification of water
2. Rain, rivers, lakes, seas and oceans.
3.
• Rihand Dam on the Rihand River
• Srisailam Dam on the Krishna River
Rainwater
Downpipe
Rainwater storage tank
(above/below ground)
Filter system
Outlet
Pump
113
Chapter 17
Forests: Our Lifeline
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• learn what are forests
• know about the different layers of forests
• understand the benefits of forests
• know what are the consequences of destruction of forests
• learn about interdependence of plants and animals in forests
• understand the different steps to conserve forests
Warm Up
Ask students what is being depicted in the picture given in Warm-up section. Ask students about
soil erosion and what is responsible for soil erosion? Ask students about the correlation between
global warming and extinction of animals.
Concept Explanation
• Forest: Tell students that about one-third of the earth surface is covered with forests. Explain
how forest helps in maintaining the balance in nature.
• Layers of forest: Tell students that a forest consists of 4 layers: emergent layer, canopy layer,
understory layer and forest layer. Also mention the characteristics of each layer. Also mention
the benefits of forests. Tell students that one should not cut trees.
• Interdependence of plants and animals: Explain to students about the biotic community.
Ask students what would happen if any species becomes extinct? Tell them about the food
chain. Also mention food web which is the interconnection of many food chains. Also tell
students that disturbance in one food chain will affect the other one also.
• Conservation of forests: Ask students to plant more and more trees. Also mention the steps
which one can take to conserve forests such as afforestation, prevention of overgrazing,
protection of forest fires, planned cultivation and prevention of illegal logging.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
114
Worksheet 1
1. Write the different layers of forest in the given picture.
(a)
_____________
(b)
_____________
(c)
_____________
(d)
_____________
2. Write any five benefits of forests.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
3. What are the consequences of deforestation?
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
115
Worksheet 2
1. What is being depicted in the given picture?
______________________________________________________________
2. What is Chipko movement?
______________________________________________________________
______________________________________________________________
______________________________________________________________
3. Write any five methods to conserve forests.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
116
Answers to Coursebook
A.
1. (a) T
(b) F
2. Afforestation—Planting trees
Roots—Prevent soil erosion
Food web—Group of food chain
(c) F
(d) T
(e) F
Vanmahotsav—Planting new seedling on a particular day
Pine—Oil
B.
1. Forests give out the oxygen we need to survive and absorb the carbon dioxide we exhale. Thus, they
are the main source of oxygen. Since forests help to maintain the balance of gases in the atmosphere,
they are also known as the lungs of the earth.
2. Deforestation has many ill-effects on the environment. These are as follows.
• Loss of forest products which are provided by plants and animals living in the forests.
• Loss of different species of animals and plants. Food chains are disturbed due to lack of plants.
Many wonderful species of plants and animals have been lost and many others are endangered.
It is estimated that about 50 to 100 species of animals are being lost each day as a result of the
destruction of their habitats, which is a huge tragedy.
• Deforestation results in barren soil which is easily eroded by wind and water. Soil (and the
nutrients in them) is exposed to the sun’s heat due to which the moisture is lost. It gradually
becomes unfit for the growth of plants.
• The levels of carbon dioxide increases in the atmosphere which leads to global warming due
to the absence of trees for absorbing this gas. When forests are destroyed, the atmosphere,
waterbodies and water table are all affected. Trees absorb and retain water in their roots.
3. They prevent soil erosion and maintain the fertility of the soil. The dry leaves, flowers and fruits get
converted into humus, thus enriching the soil. Tree roots hold the soil during heavy rains, especially
in low-lying areas such as river plains. They help the ground absorb more water, reducing soil
loss and property damage by slowing down the flow. They help to replenish groundwater through
seepage of rainwater.
4. Trees absorb water from the ground through their roots, and then release some of it as water vapour.
In this way, they manage to keep the surrounding air cool. By raising the water vapour content of
the atmosphere, trees are responsible for bringing in rains.
5. This layer is dark, damp and full of dead leaves, twigs and dead remains of animals.
• It usually lacks freshly growing vegetation and receives very little fresh air and rainfall.
• The forest floor is dark as the canopy layer of the forest stops the sunlight from entering this
layer of the forest. Only 2 per cent of sunlight actually reaches the floor.
• Animals found in this layer include jaguars in South America; gorillas and leopards in Africa;
and tapirs, tigers and elephants in Asia.
6. Food chain is the sequence of which organism is eaten by another organism. A food chain is a
simple representation of energy flow in nature. For example,
Grass
Grasshopper
Frog
Snake
Eagle
7. Human beings also depend on plants for oxygen, food, fibres like cotton, jute, hemp, medicines,
wood, timber, rubber and gum.
8. Same as answer B-7
9. (a) Emergent layer
(b) Deforestation
(c) Forest floor
(d) Canopy layer
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C.
1. Interdependence means the way in which plants and animals depend on each other in order to live,
grow and reproduce. Various organisms are interconnected and together form a biotic community
or biota. For example, bees are dependent on flowers (plants) to get nectar and flowers in turn get
pollinated by bees. So, bees and flowers are interdependent on each other. Living organisms are
classified on the basis of their nutritional habits into producers, consumers and decomposers. These
organisms occupy different levels in the food chain. Forests help in energy transfer and maintenance
of food chains. The bacteria and fungi decompose dead remains into simpler compounds and thus
enrich the soil with nutrients.
2. Soil conservation is important because soil is necessary for trees to grow. And trees are important for
the wildlife to survive. Therefore, soil conservation, forest conservation and wildlife conservation
are related to each other.
3. Forests are of great importance as a source of timber and other products. The constant need of
farmland, grazing area and fuelwood has caused destruction through centuries. So we need to
conserve this valuable resource. One of the ways to replenish the forest cover is by afforestation.
• Afforestation: Afforestation is the planting of trees in barren land to increase the area under
forests. Afforestation influences the climate of a particular area and shows positive effect on
the environment. Afforestation helps in restoring balance in the environment. The government
insists that everybody should plant trees in their lifetime. It has to take necessary actions for
converting wastelands into forests.
• Preventing overgrazing: Overgrazing by animals should be controlled. Animals should not be
allowed to graze in one area for a very long time.
• Ensuring protection from forest fires: Forests should be protected from fires which cause
large-scale destruction.
• Practising planned cultivation: Cutting and uprooting of trees should be made a punishable
offence. Vanmahotasav festival should be observed every year by planting seedlings in large
numbers.
• Preventing illegal logging: If felling of trees is essential, new trees should be planted and taken
care of in a planned way. While constructing dams and roads, all ecological factors should be
taken into consideration.
4. The basic structure of a typical forest has four major layers. They are as follows.
Emergent Layer
• This layer receives most of the sunlight because it is the topmost layer of the forest. Only the
tallest trees in the forest can reach up to this level.
• It is also known as the overstory layer.
• Animals found in this layer include birds, butterflies, small monkeys, bats and bugs.
Canopy Layer
• This is the thickest layer and serves as a roof of the forest. The thick foliage of this layer stops the
rain drops.
• The plants that grow in the canopy layer whose roots do not reach the ground are called air
plants.
• Animals found in this layer include birds, monkeys, frogs, sloths, lizards, snakes and many other insects.
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5.
D.
E.
1.
2.
3.
4.
Understory layer
• This layer has many vines and dense vegetation. This layer does not receive much sunlight as it
is blocked by the canopy layer.
• Animals found in this layer include birds, butterflies, frogs and snakes.
Forest Floor
• This layer is dark, damp and full of dead leaves, twigs and dead remains of animals.
• It usually lacks freshly growing vegetation and receives very little fresh air and rainfall.
• The forest floor is dark as the canopy layer of the forest stops the sunlight from entering this
layer of the forest. Only 2 per cent of sunlight actually reaches the floor.
• Animals found in this layer include jaguars in South America; gorillas and leopards in Africa;
and tapirs, tigers and elephants in Asia.
Forests give out the oxygen we need to survive and absorb the carbon dioxide we exhale. Thus, they
are the main source of oxygen. Since forests help to maintain the balance of gases in the atmosphere,
they are also known as the lungs of the earth.
The picture represents the balance between plants and animals. If any component is removed, then
the balance will get disturbed and it becomes impossible for everyone to survive.
Forests are the important resource. Anything that we get from forests is of use. There is nothing
which we can say that is the waste product of the forest.
The dry leaves, flowers and fruits get converted into humus, which increases the fertility of the soil.
If the wind blows in a treeless area, it will result in soil erosion.
There is a balance between the different components of the nature. If any component is lost
completely, it will affect the nature which will ultimately result in forest depletion.
Answers to Worksheets
Worksheet 1
1. (a) Emergent layer
(b) Canopy layer
(c) Understory layer (d) Forest floor
2. • Forests give us oxygen.
• Forests are home to many animals.
• They check global warming.
• They regulate climate and help in rainfall.
• They control and prevent erosion and floods.
3. • Loss of forest products which are provided by plants and animals living in the forests.
• When plants are lost, the atmosphere and waterbodies begin to dry out. Less water runs through the
rivers and smaller lakes, and streams also dry up.
• Deforestation causes severe flooding, soil erosion and landslide affecting our daily lives.
Worksheet 2
1. Deforestation.
2. The Chipko movement is a non-violent movement started by Indian villagers in the 1970s and 1980s,
to protest against the destruction of trees and forests. The movement started in the Chamoli district in
1973 and spread throughout India. Chipko activists would protest against the cutting down of trees by
hugging them and preventing the workers from doing their job.
3. • Afforestation
• Preventing overgrazing
• Ensuring protection from forest fires
• Practising planned cultivation
• Preventing illegal logging
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Chapter 18
Wastewater Management
Specific Learning Objectives
After the completion of the chapter, students will be able to:
• learn about wastewater and its sources
• understand what is domestic wastewater and sewage
• know about the wastewater treatment
• know what can be done to treat sludge
• explain the steps to reduce sewage production
• understand about sanitation in public places
Warm Up
Ask students what is being depicted in the given pictures in Warm-up section. Ask students what
will happen to the fish in picture 2? Explain them the consequences of pollution in water.
Concept Explanation
• Wastewater: Ask students what happens to the water after washing clothes? Is it still clean?
Tell students that water gets polluted by detergents, dirt and many other waste products.
Also mention the main sources of wastewater. Tell students that not only industries but also
domestic uses of water also makes the water dirty.
• The sewer system: Ask students where does the waste water go after getting discharged from
houses. Tell students that the wastewater goes to the sewers.
• Wastewater treatment plant: Tell students about the process by which wastewater can be
treated. Mention the steps needed to follow for primary, secondary and tertiary treatment of
wastewater.
• Treatment of sludge: Sludge is semi-solid slurry produced during wastewater treatment
processes. Also explain how to control sewage generation.
• Sewage disposal: Tell students about the methods used for sewage disposal. Also explain
about the vermicomposting toilets, septic tanks and biogas plant. Tell students what will
happen if the sewage is not disposed of properly.
Reinforce
• Help students develop values/skills (research and thinking) given in the Values and Life skills
sections of the chapter. Discuss the terms and their meanings given at the end of the chapter.
Discuss the answers in the class and explain them.
Explore
• Ask the students to complete the questions and the project given at the end of the chapter.
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Worksheet 1
1. Write any six sources of wastewater.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
2. What is being depicted in the given picture?
Primary treatment
Secondary treatment
Tertiary treatment
Sewage
Treated water
Mechanical process
Biological process
Chemical process
______________________________________________________________
3. List the steps of secondary treatment of wastewater.
______________________________________________________________
______________________________________________________________
______________________________________________________________
4. Define lagoons.
______________________________________________________________
______________________________________________________________
______________________________________________________________
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Worksheet 2
1. Write a few lines on the given picture.
______________________________________________________________
______________________________________________________________
2. What will happen if sewage is not managed properly?
______________________________________________________________
______________________________________________________________
______________________________________________________________
3. Write a short note on vermicomposting toilets.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
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Answers to Coursebook
A.
B.
C.
1. (a) T
(b) F
(c) F
(d) T
(e) T
2. Sludge—Settles down in the tank
Tertiary treatment—Disinfection of organic waste
Scum—Floats on the top
Microorganisms—Digestion of organic waste
Manhole—Sewer system
1. The dirty water is called wastewater. It contains urine, faeces, detergents and dirt released after
bathing, washing clothes and utensils.
2. It is produced from hospitals, factories, hotels, offices, shops and some other places.
3.
Primary sewage treatment
Secondary sewage treatment
It is a physical method of treatment.
It is a biological method of treatment.
It involves removal of large particles
and floating materials such as leaves, papers,
rags, solids such as sand, grit and oily
substances.
It involves the removal of fine suspended and
dissolved organic matter.
It makes the use of sedimentation
and filtration processes.
It makes the use of aerobic or anaerobic
biological units.
It is relatively simple and less time
consuming process.
It is relatively complex and takes a long time
for completion.
4. Improper sanitation leads to various diseases such as diarrhoea, dysentery and malaria. As per the
UNICEF reports, in India about 1000 children under the age of 5 die every day due to diarrhoea.
5. A few measures that can be adopted to control the generation of sewage are given below.
• Never pour household products such as cleaners, medicine, automobile oil and paint down the
drain. These contain harmful chemicals that may be difficult to remove. So, wastewater from
household activities should be properly disposed of.
• Fix leakages in sewer pipes. These leaks can contaminate drinking water and seep into the water
table. If this water gets stagnated, it can cause the breeding of disease-causing insects such as
flies, cockroaches and mosquitoes.
6. It is another method of disposal of waste which is used in rural areas. The organic waste including
human and animal excreta and vegetable waste is collected in a main tank called the digestor. The
microorganisms inside the tank break down the waste into methane gas. This methane gas is a
high quality fuel which can be used for cooking and the completely digested waste can be used as
a fertiliser.
7. It may cause diarrhoea, jaundice, typhoid and cholera.
1. Refer to Figure 18.1 on page 240
2. The sanitary sewer (also called a sewer system) is an underground carriage system which is
specifically designed for transporting sewage from our houses and commercial buildings through
a network of pipes for its treatment or disposal. The drainage pipes carry wastewater from our
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homes or industries. These drains are further connected to bigger pipes which carry waste from
each building to larger, underground main pipelines. These pipelines transport the sewage to
sewage treatment facilities. The sewage carrying pipes are usually made of precast concrete and
have a slight slope for water to flow quickly. Big holes with cover, called manholes, connect the
main pipelines to the surface. The manholes provide access to maintenance workers to the sewer
pipes for their inspection and maintenance in case of a blockage. The manholes also help sewer
gases to escape.
3. The primary treatment of wastewater involves the following steps.
• Screening: Screening removes large suspended particles, such as pieces of stones, metal cans
or plastic bags that could plug lines or block the inlet pipes. For this, the wastewater is passed
through vertical bars to trap and remove such objects.
• Grit chamber: The speed of the flowing wastewater is slowed down by passing it through the
grit chamber to allow the grit and sand particles to separate. The sand and grit particles, being
heavy, settle down at the bottom. The wastewater is allowed to flow for further treatment.
• Sedimentation tank, settling tank or clarifier: The wastewater is then allowed to flow into huge
settling tanks. Here, floating solid particles, such as feaces are allowed to settle at the bottom of
the tank. This waste is called sludge. Waste such as oils and detergents float to the top and are
skimmed off. This waste is called scum. The water that is released from the sedimentation tank
is called clarified water.
4. A septic tank is an efficient, low-cost and underground system to manage the household wastewater.
These are generally used in rural areas where houses are located at a distance from each other.
In semiurban areas, septic tanks are called on-site disposal system. The household wastewater is
allowed to pass into the underground septic tank. The solid waste settles down and the liquid and
the lighter waste floats on it. The microorganisms present naturally in the wastewater digest the
solid waste. The clarified liquid then flows from the tank to the outlet pipe where it gradually seeps
into the soil around it.
5. Secondary treatment of wastewater typically utilises a biological treatment process. In this process,
microorganisms convert the sludge that contains organic matter. This process is called digestion
which produces biogas. This biogas can be used as a source of fuel. Secondary treatment of
wastewater can be done by three ways.
• Activated sludge: It is the most common method which uses microorganisms in the treatment
process to break down organic material using aeration and agitation. The solid waste is then
allowed to settle. Bacteria-containing ‘activated sludge’ is continuously circulated back to the
aeration basin to increase the rate of organic decomposition.
• Trickling filters: These are the beds of coarse media, often containing stones or plastics and
are 3-10 feet deep. The wastewater is sprayed into the air (aeration), and then allowed to trickle
through the media. Microorganisms growing on the media break down the organic material
present in the wastewater. Trickling filters drain at the bottom from where the wastewater is
collected and then sent for sedimentation.
• Lagoons: It is a slow, cheap, and relatively inefficient method, but it can be used for various
types of wastewater. This process relies on the interaction of sunlight, algae, microorganisms
and oxygen with the wastewater and breaking down of organic waste present in it.
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D.
E.
6. Sewage contains harmful components, such as human and animal waste, suspended particles and
harmful chemicals. If these are thrown directly into the waterbody, then they will pollute the water
and make it unfit for human consumption. If this water mixes with drinking water supply then it
may lead to an epidemic of water-borne diseases such as diarrhoea, jaundice, typhoid and cholera.
Many of our major rivers such as the Ganga and Yamuna have become polluted to such an extent
that they are also called open sewers. In villages, people often wash their clothes, utensils, and
animals in ponds and lakes which makes these sources polluted. It is important to note that if the
sewage is treated properly, then we can protect our water sources from getting polluted and can
also generate fuels.
Refer to Figure 18.2 on page 241.
1. Yes, she does the right thing because drinking water without purify it makes us fall ill. So, drinking
bottled mineral water is a right choice when you are away from home.
2. Spitting and throwing waste in public areas leads to many diseases. So, it is a right step to impose a
penalty for people who do so.
3. The oil will make a layers over the water and due to this oxygen will not be available for the
microorganisms who decompose it. This will result in wastewater which ultimately result in many
diseases.
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Answers to Summative Assessment 2
A.
B.
C.
1.
4.
1.
4.
1.
prism
2. sludge, scum
3. concave
convex
5. clayey
6. real
(a)
2. (c)
3. (b)
(a)
5. (b)
6. (b)
Newton’s Disc: Through experiments with glass prisms, Newton discovered that white light consists
of seven colours. A Newton’s disc can be created by painting a disc with the seven different colours
violet, indigo, blue, green, yellow, orange and red. When the disc is rotated at a speed, it appears
white in colour. This explains that white light consists of seven colours.
2. A Danish scientist Hans Christian Oersted in 1819 discovered that when an electric current is
passed through any conductor, a magnetic field is created around it.
3. (a)
(b) No graph can be plotted.
4. Electric fuse is a safety device which prevents the overheating of the electrical circuit and prevents
fires. In our home also we have an electrical fuse which breaks if more than the required amount
of electric current passes through the circuit. It cuts off the supply of the electric current, thus
preventing further damage.
Principal of an electric fuse: Electric fuse is a wire usually placed inside a glass or a ceramic
cartridge. This wire is made of material that melts quickly and thus breaks the circuit. When a large
amount of current passes through the circuit, this wire gets heated up and melts away. Thus, the
circuit is broken and further damage to the electrical appliances is prevented.
5. Sludge: floating solid particles, such as feaces are allowed to settle at the bottom of the tank. This
waste is called sludge.
Activated sludge: Sludge particles produced by the growth of microorganisms in aerated tanks to
treat wastewater
6. In coastal areas, the humidity is more as compared to deserts which will increase the rusting of iron
objects.
7. Real image: If the rays of light emitted from an object actually meet at one point after reflection, a
real image is formed. A real image is always inverted, may be of the same size as the object or bigger
or smaller than the object. It can be obtained on a screen.
Virtual image: If the rays of light do not actually meet at a point after reflection but appear to meet
at a point behind the screen, a virtual image is formed. A virtual image is always erect, and may be
of the same size, or bigger or smaller than the object. It cannot be captured on a screen.
126
D.
E.
8. Ram runs a distance = 120 km
Speed = 4.5 km/h
Shyam runs a distance = 1.6 km
Time taken = 15 m = ¼ h
So, Shyam’s speed = 1.6 × 4 = 6.4 km/h
As we can see that the speed of Shyam is more than Ram, So Shyam runs faster.
1. Number of oscillations = 20
Time taken = 40 s
Time period = Time taken/Number of oscillations = 40/20 = 2 s
2. • The levels of carbon dioxide increases in the atmosphere which leads to global warming due to the
absence of trees for absorbing this gas. When forests are destroyed, the atmosphere, waterbodies
and water table are all affected. Trees absorb and retain water in their roots.
• A large part of the water that circulates in the ecosystem of rainforests remains inside the plants.
Some of this moisture is transpired into the atmosphere. When plants are lost, the atmosphere
and waterbodies begin to dry out. Less water runs through the rivers and smaller lakes, and
streams also dry up.
• Deforestation causes severe flooding, soil erosion and landslide affecting our daily lives.
3. Galvanisation: It is the process in which a layer of zinc is deposited on the iron objects. The water
pipes used in our houses are made of galvanised iron.
4. • A concave mirror is used by the dentist to observe the teeth carefully.
• It is used while shaving to see an enlarged and erect image of the face.
• It is used in the solar cooker and as radiation collectors in solar heating devices.
5. • Increasing pollution
• Increasing industries
• Deforestation
• Agricultural activities
• Pollution of freshwater resources
• Uncontrolled extraction of groundwater
• No effective means of water conservation
6. • Do not take shelter under an isolated tree. If you are in forest, take shelter under a small tree. Do
not lie down.
• Do not take shelter under an umbrella with a metallic handle.
• If you are in a swimming pool, get out and go inside the building, that is, keep away from
waterbodies.
• Do not take shelter under a metal shed.
• Do not sit near an open window.
• Do not touch or operate any electrical appliance or telephone.
• Switch off the TV.
1. Refer to Figure 8.3 on page 107.
2. Refer to Figure 13.3 on page 182.
3. Refer to Figure 11.17 on page 152.
4. Refer to Figure 9.2 on page 124.
127
Answers to Worksheets
Worksheet 1
1. • Domestic
• Construction of building
• Agriculture
• Mining
• Industries
• Hospitals
2. Wastewater treatment plant
3. • Activated sludge
• Trickling filters
• Lagoons
4. This process relies on the interaction of sunlight, algae, microorganisms and oxygen with the wastewater
and breaking down of organic waste present in it.
Worksheet 2
1. Septic tank
2. Sewage contains harmful components, such as human and animal waste, suspended particles and
harmful chemicals. If these are thrown directly into the waterbody, then they will pollute the water and
make it unfit for human consumption. If this water mixes with drinking water supply then it may lead to
an epidemic of water-borne diseases such as diarrhoea, jaundice, typhoid and cholera.
3. A vermicomposting toilet has been field tested for 8 years in India and was found to be a novel, low
water-use toilet for safe processing of human excreta without odour. It is started off by putting 5 kg of
vermicastings in the pit. It is based on the innovative design in which earthworms are used to convert
human excreta into compost. It is a safe and hygienic way of processing human waste.
128
Model Test Paper 2
100 marks
A. Fill in the balnks.
5×1=5
1. The water that is released from the sedimentation tanks is called ____________.
2. ____________ is the interconnection of many food chains.
3. A mirror in which the outer bulging surface functions as a reflecting surface is called a
____________.
4. The Earth is surrounded by an envelope of air called ____________.
5. ____________ of an object is the distance travelled by it in unit time.
B. Match the columns.
5×1=5
1 decade
Anemometer
Electric bulb
Source of water
Speed of wind
10 years
Periscope
Tungsten
Rain
Plane mirror
C. Define the following terms.
2 × 5 = 10
1. Groundwater
2. Biota
3. Manholes
4. Pie chart
5. Effect of current
D. Differentiate between.
3 × 5 = 15
1. Storms and hurricanes
2. Plane mirror and curved mirror
3. Deforestation and reforestation
4. Canopy layer and understory layer
5. Bar graph and line graph
E. Answer the following briefly.
3 × 5 = 15
1. What is sundial?
2. Write any one application of magnetic effect of current.
3. Explain the effect of atmospheric pressure on weather.
129
4. How rainbow is formed?
5. Write agricultural uses of water.
F. Answer the following in detail.
5 × 6 = 30
1. List any five benefits of forests.
2. Explain secondary treatment of wastewater.
3. Explain the components of an electric bell.
4. What is kite experiment? Explain it.
5. List the causes of spectrum.
6. Explain the different methods used to measure time in ancient times.
G. Draw the images formed when:
2 × 5 = 10
1. Object is placed very near to a concave mirror
2. Object is placed near to the convex lens
H. Look at the pictures carefully and answer the following questions.
1. What is being depicted by the given graph?
2. What will be the speed in m/s when 4 km distance is travelled in 4 minutes?
130
2 × 5 = 10
Answers to Model Test Paper 1
A. 1. (b)
B.
2. (c)
Column A
Strong base
Relative humidity
Chemical change
Small intestine
Saprophyte
3. (a)
4. (d)
5. (b)
Column B
KOH
Hygrometer
Rusting
Chyme
Fungi
C. 1. Cuscuta, Mistletoe
2. Alum, Baking soda
3. Thermos flask, Solar panels
4. Copper hydroxide, Aluminium hydroxide
5. Mango, Cherry
D. 1. Wind: The transfer of pollen grains takes place by wind. It occurs in those flowers which are not brightly
coloured and do not produce nectar. In the absence of large petal, the anthers are exposed to the wind.
This type of pollination takes place in grasses, corn and wheat.
Water: The flowers of aquatic plants release pollen grains from their anthers in water. The pollen grains
reach the stigma of another flower by means of water currents. This type of pollination takes place in
water lily Vallisneria and Hydrilla.
2. Arteries: These are thick-walled vessels, which carry blood from the heart to different parts of the body.
They carry oxygenated blood which moves under high pressure. Arteries are placed deep inside the skin
and lack valves.
Veins: Veins are thin-walled vessels which carry blood from different body parts to the heart. They
carry deoxygenated blood and are located superficially below the skin. The blood does not move under
high pressure. Veins have valves to prevent the backflow of blood.
3. A horizon: This layer is also called the topsoil. It consists of fine soil particles obtained from
parent material along with the organic matter. This layer supports the growth of plants and other
organisms. It is rich in humus and therefore dark in colour. It is soft, porous and can hold water.
B horizon: It is also called the subsoil. This layer is rich in minerals that move down with water. It
contains compactly packed fine particles of soil. Farmers often mix horizon A and horizon B when
ploughing their fields.
4. Permanent adaptation leads to permanent changes in the individual. It is inherited from one generation
to another. For example, camel is well adapted for living in desert areas.
Temporary adaptations are short-term adaptations and are not inherited by other generation. For
example, the colour of the skin gets tanned on exposure to sunlight for a long time.
5. Acid: The substances which are sour to taste. For example, citric acid
Base: The substances which are bitter to taste. For example, sodium hydroxide
E. 1. In soil treatment: Plants do not grow properly if the soil is too acidic or basic. Excessive use of nitrogen
fertiliser makes the soil acidic. Such soils can be neutralisd by using quicklime (CaO) or slaked lime
131
[Ca(OH2)]. Quicklime and slaked lime are basic, therefore, they neutralise the acid in the soil. If the soil
is basic, then organic matter is added to it. Organic matter produces acid and neutralises the effect of
excess base in the soil.
2. Copper sulphate (CuSO4) solution is blue in colour. Put an iron nail in the copper sulphate solution and
wait for half an hour. The solution turns light green and the iron nail acquires a brown coloured deposit
on it. This is due to the deposition of copper on the iron nail. The reaction can be represented as:
Copper sulphate
+
Iron
Iron sulphate + Copper
(Blue)
(Green)
(Brown deposit)
3. After chewing the food, the food passes down the oesophagus which is 2 to 3 feet long. The oesophagus
leads into the stomach which has four chambers: rumen, reticulum, omasum and abomasum.
Rumen: The rumen helps in storing large quantities of food which is partially digested here and is now
called the cud. This cud is then brought back to the mouth, re-chewed and re-swallowed. This process
is called cud-chewing. The millions of bacteria and protozoa present in the rumen break down the
carbohydrates (cellulose) found in hay and grass.
Reticulum: This part helps in the movement of swallowed food back into the mouth for further chewing.
The reticulum open into the omasum.
Omasum: This part absorbs the excess water.
Abomasum: The walls of the abomasum secrete digestive juices.
4. Scabies: Due to dipping hands in boiling water to boil the cocoons and check if the threads have
loosened or not, blisters and wounds are caused on the skin of the workers. This leads to scabies or
other such diseases.
Respiratory disease: Asthma, bronchitis and other breathing problems are caused when the workers
inhale vapours that are released due to the boiling of cocoons or diesel fumes from machines.
Loss of hearing ability: Due to the noise made by spinning and winding machines and looms, workers
suffer from hearing disorders.
Backache and other problems: The workers have to stand continuously for 12-16 hours in a day to
separate cocoons and reel the silk threads which leads to backaches and spinal cord problems.
5. Climate zones are the divisions of the Earth’s areas into general climate zones, according to their
average temperatures and rainfall. The three major climate zones on the Earth are the polar, temperate
and tropical zones. Temperatures in these three climate zones are determined mainly by the location or
latitude of the zone.
Polar region: It has the coldest climate and the temperatures are always below freezing point. The area
is usually covered with snow which melts only during summer season which lasts for a very short time.
Temperate region: This region contains most of the Earth’s landmasses. This region has moderate
temperature and receives rainfall round the year.
Tropical zone: This is the warmest region with average high temperature and receives the maximum
amount of rainfall.
F. 1. Chameleons are relatively small, carnivorous reptiles that are found in trees, where they hunt for various
insects. Chameleons are capable of changing colour. These colour changes help them to camouflage
themselves and protect themselves from predators. A chameleon can extend its tongue about one and
a half times the length of its body. It has the ability to shoot its tongue out to catch the prey and roll it
up back inside its mouth. A chameleon has large and independent eyes that move in all directions. Its
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vision is binocular, that is, each eye can also focus independently and the lizard is capable of viewing
two images separately. A chameleon uses its long prehensile tails to grip the branches. It uses its tail as
a fifth foot for anchoring so that it does not fall while moving through the trees. This reptile curls it tail
up when it is not being used to grip a branch. A chameleon’s feet are equally well designed to hold and
grip the branches.
2. The phenomenon of absorption of water by soil is termed as percolation.
Amount of water percolated (mL)
Percolation rate = Percolation time (min)
3. Breathing is a process in which exchange of gases takes place between living organisms and their
surroundings. It involves the following steps.
Inspiration or inhalation: It means to take in air which is rich in oxygen. In this process, the ribs in
the chest cavity of human beings move upwards and outwards, while the diaphragm moves downwards.
The chest cavity increases in size. The lungs expand and the air from the surroundings gets sucked into
the lungs which fills the lungs with air.
Expiration or exhalation: It means to give out air which is rich in carbon dioxide. The ribs move
downwards and inwards while the diaphragm moves upwards. This reduces the chest cavity and air is
forced out of the lungs. As the lungs reduce in size, air is expelled.
4. Blood is composed of three types of blood cells, namely, red blood cells, white blood cells and platelets.
Red blood cells: Red blood cells or RBCs are also known as erythrocytes. Red blood cells have a discshaped structure and they are red in colour due to the presence of haemoglobin protein. Haemoglobin
combines with oxygen and forms oxyhaemoglobin which carries oxygen to all parts of the body. The life
span of RBC is 120 days.
White blood cells: White blood cells or WBCs are also called leucocytes. These are colourless, Amoebalike large cells. They produce antibodies to fight against infection. They are less in number than RBCs.
They destroy disease-causing harmful bacteria and foreign materials.
Blood platelets: They are also called thrombocytes. These are smaller than RBCs. They are colourless
and irregular in shape. They help in the clotting of blood at the site of injury, thus blocking the flow of
blood and preventing blood loss.
5. The organs of human respiratory system and their functions are given below.
Nasal cavity: The nose has two openings called nostrils for the entry of the air inside the body. Hair
and the moist layer inside our nose trap dust and germs and prevent them from entering the body, thus
cleaning the inhaled air.
Pharynx: The warm and moist air reaches the funnel-shaped structure called pharynx. This is a
common passage for food and air.
Trachea: It is small tube-like structure. It is also called windpipe. The air which we breathe in passes
through it to reach the lungs.
Bronchi: The trachea gets divided into two tubes called bronchi. Each bronchi enters into the lungs and
carries air from the windpipe to the lungs.
Lungs: Each bronchus opens into lungs. Lungs are dark, spongy, bag-like conical-shaped organs. Inside
each lung, bronchus divides and redivides into thin tubes, which end into air sacs called alveoli.
Alveoli: These are also called air sacs. Alveoli are richly supplied by blood vessels. These are the site of
gaseous exchange.
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6. Plants can be reproduced vegetatively by artificial means. These methods include grafting, cutting,
layering and tissue culture.
Grafting: It is a common method where a small piece of a stem of another plant is cut and is placed
on the stem of another plant which is rooted in soil. The inserted branch is called scion or graft and
the rooted part of the plant on which the cutting is attached is called a stock. The scion and stock are
tied together with a thread so that their cambium get fused into one. This technique is very helpful in
developing new varieties of plants such as rose, mango and cherry.
Cutting: In this method, a piece of stem is cut from the main plant and is placed in moist soil. After
some time, it grows into a plant. For example, sugar cane, rose, Bougainvillea, Hibiscus and cactus are
grown by this method.
Layering: In this method, a young branch of the plant is bent towards the ground and covered by moist
soil. After some time, roots grow from the part of the stem which is buried below the soil. The parent
branch is cut off and the new young plant grows further. Gardeners use this method to grow new plants
of jasmine, Bougainvillea and grapes.
Tissue Culture: In this method of growing plants, a few cells from the mother plant are grown to
make tissues in a nutritive medium. The tissue is then transferred into another medium which give rise
to small plantlets. These plantlets are then transferred to the moist soil for further growth. Orchids,
Chrysanthemum and Asparagus are grown by such methods.
7. Melting and boiling points: Salts have high melting and boiling points.
Solubility in water: Salts are usually soluble in water. For example, sodium chloride and potassium
sulphate are soluble in water. Salts such as silver chloride are insoluble in water.
Conduction of electricity: Distilled water is a bad conductor of electricity. When some salt is added to
it, the solution becomes a good conductor of electricity.
Water of crystallisation: Most of the salt crystals contain some molecules of water. This is called water
of crystallisation. The salt containing the water of crystallisation is called hydrated salt. This water of
crystallisation gives the crystal its shape, it is lost when the salt is heated. On heating, the colour and the
crystallised structure of the salt can also change. For example, CuSO 4.5H2O (hydrated copper sulphate)
salt is blue in colour. When it is heated, it loses the water of crystallisation and changes into CuSO4
(anhydrous copper sulphate), which is white in colour. The hydrated salts that have lost their water of
crystallisation are called anhydrous salts.
G. Given, Initial amount of water (U) = 650 mL
Final amount of water (V) = 500 mL
Percentage of water absorbed = (U – V × 100)/U
= (650 – 500 × 100)/650 = 23.07 %
H. 1. Sporulation
2. Sporulation occurs in bacteria, fungi, moss and ferns. During unfavourable climatic conditions such
as scarcity of water, food, heat or dryness, the plants produce reproductive spores. The spore is a small
single-celled reproductive body which is covered by a thick and hard protective coating. This protective
layer helps it to survive under unfavourable conditions. When the conditions become favourable, the
thick coating breaks open and spores germinate to produce a new plant.
3. Other examples which reproduce by sporulation are bread mould and Rhizopus.
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Answers to Model Test Paper 2
A.1. Clarified water
2. Food web
3. Convex mirror
4. Atmosphere
5. Speed
B.
Column A
1 decade
Electric bulb
Speed of wind
Periscope
Rain
Column B
10 years
Tungsten
Anemometer
Plane mirror
Source of water
C. 1. Groundwater is the water stored under the ground where the soil is completely filled or saturated with
water.
2. Various organisms are interconnected and together form a biotic community or biota.
3. quickly. Big holes with cover, called manholes, connect the main pipelines to the surface.
4. A pie chart is a circular chart divided into sectors. Each sector shows the relative size of each value.
5. The process of conversion of electrical energy into another form of energy is called the effect of current.
D. 1. Storms: These are severe atmosphere disturbances accompanied by strong winds blowing at a very high
speed.
Hurricanes: Storms are called hurricanes in North America and the Caribbean.
2. Plane mirror: This type of mirror has a highly polished flat surface to reflect light rays. A steel plate, a
shiny surface or still water can also act like a plane mirror.
Curved mirror: This type of mirror has a curved reflecting surface. These type of mirrors are also called
spherical mirrors or parabolic mirrors. Concave and convex mirrors are examples of curved mirror.
3. Cutting of trees on a large scale is called deforestation.
Planting of trees is called reforestation.
4. Canopy Layer: This is the thickest layer and serves as a roof of the forest. The thick foliage of this layer
stops the rain drops.
Understory layer: This layer has many vines and dense vegetation. This layer does not receive much
sunlight as it is blocked by the canopy layer.
5. Bar graph: A bar graph (also called a bar chart) is a graphical display of data using bars of different
heights.
Line Graph: A line graph is useful for displaying data or information that changes continuously over time.
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E. 1. Sundial: A sundial is a device that tells the time of the day by observing the apparent position of the
sun in the sky. In common designs, such as the horizontal sundial, the sun casts a shadow of a gnomon
on a surface marked with lines, indicating the hours of the day. As the sun appears to move across the
sky, the edge of the shadow aligns with different hour-lines and gives us the of time. This instrument
cannot work at night.
2. The most common application of this property of electricity is to make an electromagnet. When an
electric current is passed through a coil of insulated wire wrapped around a piece of iron, the iron exhibits
the properties of a magnet. The magnet made using such an arrangement is called an electromagnet
3. Movement of air upwards causes cloudy sky whereas downward movement of air causes clear sky. As air
rises and creates an area of low pressure, water vapour in it condenses to form clouds. Thus low pressure
is associated with cloudy skies and wet weather whereas high pressure is associated with clear and sunny
skies.
4. A band of colours in the sky extending from violet to red is called a rainbow. A rainbow is formed by
the refraction and reflection of the sun rays through raindrops. A rainbow is a natural spectrum which
appears in the sky after rain. The sunrays are dispersed by the water droplets present in the atmosphere.
The water droplets act as small prisms which refract and disperse the sunrays falling on them. The
sunrays emerging out of the water droplets are refracted again. A rainbow is always formed in the
direction opposite to the position of the sun. Although sunlight appears white, it is composed of seven
colours. The colours in a rainbow are the constituent colours of sunlight.
5. Irrigation of crops is essential for growing fruits, vegetables and grains to feed the world’s growing
population. Almost 60 per cent people of our country depend on agriculture for their living. Throughout
the world, irrigation is probably the most important use of water. According to estimates, about 70 per
cent of all the world’s freshwater is used for irrigation purposes. This water is obtained from rivers, lakes,
reservoirs and wells.
F. 1. They block wind: Group of trees serve as a windbreak and protect the wind-sensitive crops growing
near the forest. Less wind also makes it easier for bees to pollinate the flowers.
They are a source of food: Trees provide fruits, nuts, seeds, edible mushrooms, berries for human
beings and for other animals such as deer, turkeys, rabbits and fish.
They give us medicines: Neem, eucalyptus and amla plants are used to make many ayurvedic medicines.
Cinchona trees provide quinine, which is used for treating malaria. Many kinds of essential oils are
obtained from grasses such as lemon grass, kewra and khus. Pine, eucalyptus and sandalwood also give
us oil. Forests provide a wealth of natural medicines.
They provide us with materials to make our lives better: We use various forest resources such as timber,
raisin (used to make paint and varnish), gum (used to make paper), cane (used to make furniture) and
latex (used to make rubber).
They help us to relax and relieve stress: Our innate attraction to forests is a part of a phenomenon
known as biophilia which draws human beings to water, forests and other natural scenic areas.
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2. Secondary treatment of wastewater can be done by three ways.
Activated sludge: It is the most common method which uses microorganisms in the treatment process
to break down organic material using aeration and agitation. The solid waste is then allowed to settle.
Bacteria-containing ‘activated sludge’ is continuously circulated back to the aeration basin to increase
the rate of organic decomposition.
Trickling filters: These are the beds of coarse media, often containing stones or plastics and are
3-10 feet deep. The wastewater is sprayed into the air (aeration), and then allowed to trickle through
the media. Microorganisms growing on the media break down the organic material present in the
wastewater. Trickling filters drain at the bottom from where the wastewater is collected and then sent
for sedimentation.
Lagoons: It is a slow, cheap, and relatively inefficient method, but it can be used for various types of
wastewater. This process relies on the interaction of sunlight, algae, microorganisms and oxygen with
the wastewater and breaking down of organic waste present in it.
3. A simple electric bell has the following components.
(a) Electromagnet – It is a ‘U’ shaped soft, iron rod.
(b) Strip spring – A slightly bent metallic strip.
(c) Armature – It is made of soft iron, facing the two poles of the electromagnet.
(d) Contact screw – It is a screw to make or break the contact in the circuit.
(e) Hammer – It is made of steel.
(f) Gong – It is a circular, hollow disc made of brass.
(g) Switch – It is a push button.
(h) Battery – It is the source of electricity in an electric bell.
4. Benjamin Franklin, on June 1752, built a kite with a sharp, pointed wire attached to the kite to attract
the electrical charges (working like a lightning rod). He attached a key at the end of the kite string, near
his holding hand and held the kite with a silk ribbon also tied to the key. A thin metal wire, connected
to the key, was inserted into a Leyden jar (a container for storing electrical charges). The flying kite
was struck by lightning and the sparks (electrical charges/static electricity) flew through the wet kite
and string to the key and inside the Leyden jar. After he noticed that the loose fibres of the string were
bristling outward because the string was charged with static electricity, he intentionally extended his
knuckle to touch the key and he felt an electrical shock. This experiment proves that lightning is an
electric phenomenon.
5. The dispersion of white light occurs because the angle of refraction (angle of bending) of light rays of
different colours is different when they pass through the glass prism.
The red colour deviates the least, so it forms the upper part of the spectrum.
The violet colour deviates the maximum, so violet colour appears at the bottom of the spectrum.
6. Ancient people develop devices like sundial, hour glass and water clock to measure time.
Hour glass: An hour glass (sand timer, sand watch, or sand clock) is a mechanical device which was
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used to measure the passage of time. It comprises two glass bulbs which are connected vertically by a
narrow neck that allows a regulated trickle of sand from the upper bulb to the lower one. Factors which
affect the time interval to be measured are the quantity of sand, its coarseness, the bulb size and the neck
width.
Sundial: A sundial is a device that tells the time of the day by observing the apparent position of the
sun in the sky. In common designs, such as the horizontal sundial, the sun casts a shadow of a gnomon
on a surface marked with lines, indicating the hours of the day. As the sun appears to move across the
sky, the edge of the shadow aligns with different hour-lines and gives us the of time. This instrument
cannot work at night.
Water clock: An instrument called water clock was also used to measure time. It worked on the principle
of regulated flow of water.
G. 1. Refer to Figure 15.8 on page 205.
2. Refer to Figure 15.13 on page 208.
H. 1. Distance-time graph for uniform motion is being depicted by the given graph.
2. Given, distance = 4 km = 4000 m
Time = 4 min = 240 s
Speed = Distance/Time
= 4000/240 = 16.66 m/s
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