Modern Concept Science and Technology 4

Unit 6 CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS

iii) Submerged hydrophytes

Those aquatic plants that are present under the surface of water are called submerged
hydrophytes. Vallisneria, hydrilla, chara are examples of submerged hydrophytes.
Submerged hydrophytes have short and narrow leaves. They do not have stomata on
their leaves. So, they respire through the general body surface. The roots of the
submerged hydrophytes are xed to the soil at the bottom. Their stems are exible
with air spaces.

Vallisneria Hydrilla Chara
Fig. 6.4 Submerged hydrophytes

Characteristics of aquatic plants

i) Most of the aquatic plants are soft and weak.
ii) Aquatic plants have small and poorly developed roots.
iii) Most of the aquatic plants have a hollow, eshy and exible stem.
iv) Leaves and stem of aquatic plants have air- lled cells.
v) Free oating hydrophytes and xed hydrophytes transpire water from their upper

surface. It is because they have stomata on the upper surface of the leaves.
vi) Leaves and stem of the aquatic plants are covered with an oily and waxy substance.
vii) It prevents them form getting wet and decaying.

B. Terrestrial plants

Plants like the mango, banana, rose, pea, Mango Tree Orange Tree
mustard grow on land. They are called
terrestrial plants. Thus, plants that grow Fig. 6.5 Terrestrial
on land are called terrestrial plants. plants
Terrestrial plants are found in a di erent
environment. Some plants are found in Pine Tree Cactus
hot and wet places. Some are found in
cold places, and some in hot and dry
places. Shade loving plants are found in
shady and moist places. The shape, size,
color and structure of plants vary from
plant to plant.

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CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS Unit 6

Di erent types of terrestrial plants

Environmental factors like climate, temperature, soil, rainfall, altitude, etc. di er in
di erent places on the earth. They a ect directly and indirectly on the terrestrial plants.
So, di erent plants are found in di erent parts on the earth’s surface.

a. Plants found in hot and wet environment

Plants like coconut, mango, banyan, saal, sisoo, jamun grow in a hot and wet
environment. Mostly these plants grow in plain areas. They are tall and have many
branches. Some of these plants are evergreen while some shed their leaves in winter.
Some terrestrial plants shed their leaves in winter to protect themselves from the cold.

Mango Tree Banyan Tree Fig. 6.6 Saal Tree Sissoo Tree

i. Plants found in hot and highly wet ii. Plants found in shady and wet
environment environment

Some terrestrial plants like rubber, oil Some plants like orchids, fern, moss,
palms, mangroves, co ee, tea grow in mushroom, liverworts grow in shady and
areas where there is high rainfall. These wet areas. They cannot tolerate direct
plants need a hot and highly wet sunlight.
environment. They are evergreen plants.
They do not shed their leaves in winter.
So, the plants which grow in a hot and
highly wet environment make an
evergreen forest.

Rubber plant Orchid Fern

Oil palms

Mangrove Fig. 6.7 Moss Fig. 6.8 Mushroom

Tea plant

44 Modern Concept Science, Health & Physical Education - 4

Unit 6 CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS

b. Plants found in cold environment

Plants like spruce, r, pine, junipers are found in a cold climate. Leaves of these plants
are reduced to needle shape. Such leaves easily allow the snow to slip through. These
leaves also help to reduce transpiration. Plants found in a cold environment also bear
cones instead of owers.

Pine Spruce Fig. 6.9 Fir Juniper

c. Plants found in hot and dry environment

Plants which grow in a hot and dry environment are called xerophytes. They are also
called desert plants. Cactus, aloe, opuntia are found in a hot and dry environment. They
have a green and eshy stem for photosynthesis. Their stem stores water. Their leaves
are reduced to sharp spines. These spiny leaves keep them safe from herbivores. They
also help to prevent loss of water in transpiration.

Cactus Aloe Opuntia
Fig. 6.10
Types of terrestrial plants

On the basis of the shape, size, structure and growth pattern, the plants are divided into

three types. They are herbs, shrubs and trees.

i) Herbs

Very small and weak plants are called herbs. Maize, potato, grass, lettuce, wheat, paddy,
coriander, millet, brinjal, tulsi, mint, onion, ginger, barley, marigold, dahlia are examples
of herbs. We get most of the food, vegetables, oil and medicines from these plants.

Modern Concept Science, Health & Physical Education - 4 45

CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS Unit 6

Coriander Brinjal Maize Tomato Wheat

Fig. 6.11

Herbs have small and weak roots. They have a weak and eshy stem. Most of their stems
are green in color. These stems involve in photosynthesis. Generally, herbs complete
their life cycle within a season.

ii) Shrubs

The medium-sized bushy plants with woody stems are called shrubs. Rose, lemon, cotton,
china rose, tea, co ee, pomegranate, peach, plum are some examples of shrubs.

Tea Coffee Rose Lemon

Fig. 6.12

Shrubs have strong roots. Their stems are thin but strong and woody. They bear many
small branches and leaves. Some of the shrubs also bear spines in their stem, branches
and leaves. Shrubs can live for a few years.

iii) Trees

Very big plants with a hard and woody trunk are called trees. For example, coconut,
mango, pine, peepal, sal, simal, jamun, jackfruit, guava.

Coconut Mango Tree Pine Saal Tree Peepal
Fig. 6.13

46 Modern Concept Science, Health & Physical Education - 4

Unit 6 CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS

Trees have well developed and strong roots. The roots hold the plants strongly into the
ground. They have a strong and woody stem. The stem of trees bears many branches
and sub-branches. Their stem is covered with a protective outer covering called the bark.
Trees can live for many years.

Rapid fire revision

* Di erent plants live in di erent habitats.
* On the basis of habitat, plants are divided into two major groups. They are aquatic

plants and terrestrial plants.
* Plants that grow only in water are called aquatic plants. For example, hydrilla,

duckweed, vallisneria, water lily, lotus.
* Those aquatic plants that oat freely on water are called free oating hydrophytes.

Water hyacinth, duckweed, pistia.
* Those aquatic plants that have roots xed to the soil at the bottom of the water are

called xed hydrophytes. Lotus, water lily.
* Those aquatic plants that are present under the surface of the water are called

submerged hydrophytes. Valisnaria, hydrilla, chara.
* Most of the aquatic plants are soft and weak. They have small and poorly

developed roots. They have a hollow, eshy and exible stem.
* The plants that grow on land are called terrestrial plants. For example, mango,

banana, rose, pea.
* Plants like coconut, mango, banyan, saal, sisoo, jamun grow in a hot and wet

environment.
* Some terrestrial plants like rubber, oil palm, mangroves, co ee, tea grow in areas

where there is high rainfall.
* Some plants like orchids, fern, moss, mushroom, liverworts grow in shady and wet

areas.
* Plants like spruce, r, pine, junipers are found in a cold climate.
* Plants which grow in a hot and dry environment are called xerophytes. For

example, cactus, aloe, opuntia.
* Very small and weak plants are called herbs. For example, maize, potato, grass, lettuce,

wheat, paddy, coriander, millet, brinjal.
* Medium-sized bushy plants with woody stems are called shrubs. For example, rose,

lemon, cotton, china rose.
* Very big plants with a hard and woody trunk are called trees. For example, coconut,

mango, pine, peepal, sal.

Three steps exercise

Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Xerophytes grow in water. ( )
b) Cactus is an example of hydrophyte. ( )
c) Lotus is an underwater plant. ( )
d) Spines in leaves protect plants from herbivores. ( )
e) Pine is found in cold regions. ( )

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CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS Unit 6

f ) Co ee is an example of herb. ( )
g) Shrubs complete their life cycle in one year. ( )
h) Mushrooms are found in moist and shady places. ( )
2. Fill in the blanks with appropriate words.
a) Plants that oat freely in water are called ………
b) Hydrilla is an example ……… hydrophyte.
c) Small and weak plants are called ………
d) Fern lives in ……… and ……… places.
e) Aquatic plants have leaves covered by ……… substance.
f ) Cactus is an example of ………
g) Green stem of xerophytes help in ……….

3. Match the following: o Pine
a) Hydrophyte o Hydrilla
b) Xerophyte o Fern
c) Herb o Peepal
d) Shrub o Coriander
e) Moist and shady places o Cactus
f ) Cold and dry places o Tea plant
g) Tree

4. Choose the correct alternative.

a) Which is an underwater plant?

i. Duckweed ii. Hydrilla

iii. Lotus iv. Cactus

b) Which is a xed hydrophyte?

i. Vallisneria ii. Chara

iii. Water lily iv. Coriander

c) Which of the following has needle shaped leaves?

i. Lemon ii. Cactus

iii. Orange iv. Saal

d) Coriander is an example of

i. Herb ii. Shrub

iii. Tree iv. Xerophyte

e) Which plant lives for many years?

i. Cauli ower ii. Banyan

iii. Cabbage iv. Mustard

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Unit 6 CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS

f ) Which is a xerophyte?

i. Fir ii. Banyan

iii. Cactus iv. Sal

g) Which plant grows in moist and shady places?

i. Peepal ii. Simal

iii. Sisso iv. Mushroom

Step: 2

5. Di erentiate between:
a) Hydrophytes and xerophytes
b) Duckweed and hydrilla
c) Coconut and pine
d) Cactus and fern
e) Shrub and herb

6. Give reasons:
a) Hyrilla is a hydrophyte.
b) Cactus is an example of xerophyte.
c) Aquatic plants have a waxy layer in their stem and leaves.
d) Grass falls under the division herb.
e) Co ee is an example of a shrub.
f ) A mango plant is a tree.

7. In which environment do we get the following plants.
a) Mango __________________
b) Coconut __________________
c) Pine __________________
d) Cactus __________________
e) Spruce __________________
f ) Opuntia __________________
g) Hydrilla __________________
h) Lotus __________________

8. Name the following plants and classify them as: oating hydrophytes, xed
hydrophytes and submerged hydrophytes.

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CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS Unit 6

Name: Name: Name:
Type: Type: Type:

Name: Name: Name:
Type: Type: Type:

9. Name the given plants and classify them as: herb, shrub and trees.

Name: Name: Name:
Type: Type: Type:

Name: Name: Name:
Type: Type: Type:

50 Modern Concept Science, Health & Physical Education - 4

Unit 6 CHARACTERISTICS OF AQUATIC AND TERRESTRIAL PLANTS

Name: Name: Name:
Type: Type: Type:

Name: Name: Name:
Type: Type: Type:

Step: 3

10. De ne the following terms with three examples each:
a) Hydrophytes
b) Terrestrial plants
c) Xerophytes
d) Floating hydrophytes
e) Fixed hydrophytes
f ) Submerged hydrophytes
g) Herb
h) Shrub
i) Tree
11. Answer the following questions:
a) List three important characteristics of hydrophytes.
b) Write three characteristics of terrestrial plants.
c) Write down three important features of a cactus.
d) Where do tea and co ee like to grow?
e) What type of climate does pine need?
f ) In which environment does coconut grow?
g) Write down two features each of a herb, shrub and tree.
12. Draw a neat diagram of:

a) Lotus b) Cactus c) Mushroom d) Spruce

Modern Concept Science, Health & Physical Education - 4 51

7Unit INTERRELATIONSHIP
BETWEEN LIVING BEINGS
AND ENVIRONMENT

Scientific terms and terminologies of the unit

1. Environment : The surrounding world that influences the life and activities
2. Ecosystem of living beings is called the environment.
3. Ecology
4. Biotic components : The interaction between biotic components and abiotic
5. Abiotic components components in a given area is called the ecosystem.
6. Producers
7. Consumers : The study of the interrelationship between biotic and abiotic
8. Decomposers components of the ecosystem is called ecology.

9. Food chain : The living things of the environment are called biotic
components.

: The non-living things of the environment are called abiotic
components.

: Living beings that prepare their own food are called producers.

: The organisms that depend upon producers for their food are
called consumers.

: The organisms that derive their food from the dead and decayed
parts of plants and animals are called decomposers.

: The process of eating and being eaten is called the food chain.

Introduction

We see di erent kinds of living and non-living things around us. Living things include animals,
plants and micro-organisms. Similarly, non-living things include air, water, soil, rocks, sunlight.
These living and non-living things are interrelated to each other. Living things depend upon
non-living things for their survival. Thus, the surrounding world that in uences the life and
activities of living beings is called the environment. Both living beings and non-living things
are part of an environment. Environment provides all basic requirements for living beings to
live. It provides air, water, food, shelter for living beings.

Fig. 7.1 Various things obtained from plants
52 Modern Concept Science, Health & Physical Education - 4

INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT Unit 7

Activity 1

List the major food that you eat. Also, write from where it comes from.

Ecology

Living things of the environment are called biotic components. It includes animals, plants and
micro-organisms. Similarly, non-living things of the environment are called abiotic components.
It includes air, water, soil, rocks, sunlight. The interaction between biotic components and abiotic
components in a given area is called the ecosystem. The study of the interrelationship between
biotic and abiotic components of the ecosystem is called ecology.

Photosynthesis

Plants are the major living
components of the environment.
Green plants have a green pigment
in their leaves and stem. This green
O2

pigment is called chlorophyll. Green O2 CO2 CO2
plants use sunlight, carbon dioxide
and water from the environment and
produce their own food. The process
of preparing food by green plants
Fig. 7.2 Photosynthesis

using sunlight, water and carbon dioxide is called photosynthesis. After photosynthesis, plants
release oxygen in the environment. Both animals and plants take in oxygen and breathe out
carbon dioxide. This process balances the gases in the atmosphere.

Producers and Consumers

Living beings that prepare their own food are called producers. All green plants are called
producers of the ecosystem.

Fig. 7.3 Examples of producers 53
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Unit 7 INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT

Animals cannot prepare their own food. They consume the food produced by the plants
(producers). Thus, the organisms that depend upon the producers for their food are called
consumers. Herbivores eat plants, carnivores eat herbivores and omnivores eat both animals
and plants.

Herbivores

Carnivores

Fig. 7.4 Examples of consumers

Decomposers

The organisms that derive their food from the dead and decayed
parts of plants and animals are called decomposers. Fungi and
bacteria are the examples of decomposers. Living beings also
release unwanted substances from their body. These unwanted
substances mix with the soil and provide nutrients to the growing
plants. After the death of the organisms decomposers break down Bacteria Mushroom (Fungi)

the complex organic matter into simpler nutrients and release Fig. 7.5 Examples of decomposers
them in the soil.

Activity 2

List the names of producers and consumers present in your kitchen garden.

Food Chain

The process of eating and being eaten is
called the food chain. It is a process of
transferring food energy from one living
organism to other. On grasslands, deer eats Grass (Producer) Deer (Primary consumer)

grass. The deer is eaten by the tiger. After
the death of the tiger, bacteria and fungi
Fig. 7.6 Food chain

break down the dead body into simpler
substances. These simpler substances mix
with the soil. Plants absorb these substances
by their roots along with water. In this way, Fungi (Decomposer)
the food chain continues. Tiger (Secondary consumer)

54 Modern Concept Science, Health & Physical Education - 4

INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT Unit 7

Similarly, there are many food chains in the ponds, forests, grasslands, etc.

Fish
Fig. 7.7 Food chain (in pond ecosystem)

Chara

Turtle

Bacteria

Shelter of animals

Plants not only provide air and food for
animals, they also provide shelter to the
animals. Birds use leaves, twigs and
branches of trees to make their nest.
Forest and grasslands are homes for
many animals. Human beings also use
thatch, bamboo for making shelter.

Fig. 7.8 Shelter of animals

Interrelation between plants and animals

Animals and plants are closely related to each other. They bene t each other. Animals cannot
live without plants. They take nutrients from the plants and return them to the soil after their
death. Plants release oxygen during photosynthesis. All living organisms use oxygen to breathe
and release carbon dioxide in the air. Similarly, living organisms also depend upon each other
for their food and shelter. Disturbance in one of the components disturbs the whole ecosystem.
If all plants on the grasslands were to perish, the deer would die due to lack of food. The tiger
would also die due to the absence of the deer. Similarly, if all deer are removed from the
ecosystem, the tiger cannot eat plants, hence they would die. On the other hand, plants grow
excessively and exhaust all the nutrients from the soil. The above discussion proves that di erent
living and non-living components of the environment are interrelated.

Activity 3

Find various types of food chain in your garden or surrounding area and make a sketch to
show them.

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Unit 7 INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT

Rapid fire revision

* The surrounding world that in uences the life and activities of living beings is called
the environment. Both living beings and non-living things are part of the environment.

* The interaction between biotic components and abiotic components in a given area is
called the ecosystem.

* The study of the interrelationship between biotic and abiotic components of the
ecosystem is called ecology.

* The process of preparing food by green plants using sunlight, water and carbon dioxide
is called photosynthesis. Green plants carry out photosynthesis.

* Living beings that prepare their own food are called producers. All green plants are called
producers.

* Organisms that depend upon the producers for their food are called consumers. All
animals are examples of consumers.

* The organisms that derive their food from the dead and decayed parts of plants and
animals are called decomposers. Fungi and bacteria are examples of decomposers.

* The process of eating and being eaten is called the food chain. It is a process of
transferring food energy form one living organism to another.

* Animals and plants are closely related to each other. They bene t to each other.

Three steps exercise
Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Living and non-living components make the environment. ( )
b) Plants and animals are interrelated with to each other. ( )
c) Fungi are examples of producers. ( )
d) Plants with chlorophyll can produce their own food. ( )
e) After photosynthesis, plants release carbon dioxide. ( )
f ) The process of eating and being eaten is called the food chain.( )
g) Herbivores are called esh eating animals.( )
h) Air and water are non-living components of the ecosystem. ( )
2. Fill in the blanks with appropriate words.
a) The surrounding of living beings is called …………
b) …………and ………… components make the environment.
c) Organisms that prepare their own food are called …………
d) Water is an example of …………component of the ecosystem.
e) Plants release …………gas during photosynthesis.
f ) Decomposers include…………and …………
g) In the food chain, carnivores eat…………

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INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT Unit 7

3. Match the following: o Green plants
a) Water o Biotic component
b) Animals o Bacteria
c) Chlorophyll o Abiotic component
d) Producers o Transfer of food energy
e) Animals and plants o Cannot prepare their food
f ) Decomposer o Green pigment
g) Food chain

4. Choose the best alternative.

a) Which of the following can prepare their own food?

i. Fungi ii. Mushroom

iii. Fern iv. Bacteria

b) Which of the following can break down the dead body of animals and plants?

i. Plants ii. Consumers

iii. Decomposers iv. Animals

c) Which is the living component of the ecosystem?

i. Air ii. Water

iii. Soil iv. Animals

d) Which is the non-living component of the ecosystem?

i. Plants ii. Water

iii. Bacteria iv. Animals

e) ……. eat both plants and animals.

i. Herbivores ii. Carnivores

iii. Omnivores iv. Producers

f ) Which of the following indirectly depend upon plants for their food?

i. Tiger ii. Deer

iii. Cow iv. Grasshopper

Step: 2

5. Di erentiate between:
a) Abiotic and biotic components
b) Producers and consumers
c) Producers and Decomposers
d) Herbivores and carnivores

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Unit 7 INTERRELATIONSHIP BETWEEN LIVING BEINGS AND ENVIRONMENT

6. Give reasons.
a) Water is an example of the abiotic component of the environment.
b) Plants are the biotic components of the environment.
c) Plants are called producers.
d) Animals are also called consumers.
7. Name the producer, herbivore and carnivore in the given food chain.

8. Give two examples of each:
a) Abiotic components
b) Biotic components
c) Producers
d) Herbivores
e) Carnivores
f ) Omnivores

Step: 3

9. Answer the following questions.
a) De ne environment and write down its components.
b) What is photosynthesis? What are necessary for photosynthesis?
c) De ne producers with two examples.
d) What are consumers? Give three examples.
e) De ne food chain. Give an example of grassland food chain.
f ) Explain the interrelationship between animals and plants.
g) How are producers, consumers and decomposers interrelated?
h) What happens in the ecosystem when all deer are killed?

10. Explain a grassland food chain with a labeled diagram.

58 Modern Concept Science, Health & Physical Education - 4

8Unit NATURAL DISASTERS

Scientific terms and terminologies of the unit

1. Disasters : Those events that occur suddenly and cause loss of lives and
2. Man-made disasters property are called disasters.

3. Natural disasters : The disasters which are caused by the activities of human beings
4. Flood like wars, aircraft accidents, bus accidents are called man-made
5. Landslide disasters.
6. Fire
: The disasters that are caused by an imbalance in nature are
called natural disasters.

: The overflow of water in the channel of rivers and streams
during the rainy season is called flood.

: A natural disaster in which a landmass falls from a higher
altitude to a lower altitude is called a landslide.

: An incident in which flammable objects burn causing loss of
lives and property is called a fire.

Introduction

Do you listen to the news regularly?
Sometimes, the news is about the destruction
caused by war, landslide, ood, re, aircraft
accident, earthquake, storm, etc. These events
kill people and destroy property.

Those events that occur suddenly and cause Flood Landslide

loss of lives and properties are called disasters.

Some disasters are caused by the activities of

human beings. Wars, aircraft accidents, bus

accidents are some man-made disasters. Volcano
Similarly, the disasters that are caused by an
Earthquake

imbalance in nature are called natural

disasters. An earthquake, volcano, ood, Fig. 8.1 Natural
Disasters
landslide, etc. are some examples of natural
disasters. We can prevent man-made disasters,

but we cannot prevent natural disasters. Fire

Modern Concept Science, Health & Physical Education - 4 59

NATURAL DISASTERS Unit 8

Activity 1

Name the disasters that occur in your surroundings. Have you felt any natural
disaster? Also, write when and where you felt that natural disaster.

Floods Fig. 8.2 Flood

Water ows in the channel of rivers and streams.
Sometime there is over ow of water in these
rivers and streams. It is called a ood. Thus, the
over ow of water in the channel of rivers and
streams during the rainy season is called a ood.
A ood is a natural disaster. It occurs mostly in
the plain areas. The terai region of our country
su ers from oods during the rainy season.
Flood damage life and property every year.

Causes of oods

i) Heavy rainfall for a long time
ii) Rapid melting of snow and ice in the mountains
iii) Bursting of dams in rivers and lakes
iv) Bursting of glacial lakes in the mountainous regions
v) Destruction of forest

E ects of oods

i) A ood drowns people and takes their lives.
ii) It sweeps away houses, roads, bridges.
iii) It kills animals.
iv) It destroys agricultural crops.
v) It causes water pollution.
vi) There are outbreaks of di erent types of diseases.

Prevention and control measures of oods

i) A ood can be controlled by planting trees on barren areas and on both
sides of a river.

ii) It can be controlled by building ponds and large tanks to collect rainwater.
iii) It can be controlled by building embankments on the banks of a river.
iv) It can be controlled by managing the draining of glacial lakes.

Activity 2

Visit your locality and make a list of the controlling measures that people use to
control oods.

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Unit 8 NATURAL DISASTERS

Landslides

Nepal is a country of hills and mountains. During the Fig. 8.3 Landslide
rainy season, many landslides occur in di erent parts
of Nepal every year. They destroy lives and property.
Di erent factors like heavy rainfall, earthquakes,
deforestation, explosion of bombs weaken the land.
The weak landmass moves from a higher altitude to a
lower altitude and is called a landslide. Thus, a natural
disaster in which a landmass falls from a higher altitude
to the a lower altitude is called a landslide.

Causes of landslides

i) A landslide is caused by heavy and continuous rainfall.
ii) It may be caused due to vibration during an earthquake.
iii) It may be caused by the movement of large and heavy vehicles.
iv) It may be caused by deforestation on sloping areas.
v) It may be caused by bomb blast.
vi) It may be caused by outburst of dams.

E ects of landslides

i) A landslide destroys lives and properties.
ii) It damages houses, roads, buildings, bridges,

communication towers, etc.
iii) It damages agricultural land and crops.
iv) It causes water pollution.
v) It causes ood in rivers and streams.

Prevention and control measures of landslides

i) Landslides can be controlled by planting trees on open and hilly areas.
ii) It can be controlled by constructing landslide controlling structures like

dams, gabion walls, etc.
iii) It can be controlled by reducing deforestation and overgrazing in the hilly

areas.
iv) It can be controlled by scienti c farming or terrace farming in the hilly area.

Activity 3

Have you seen any landslide controlling structures? Name them and paste their
photos on your project work copy.

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NATURAL DISASTERS Unit 8

Fire Fig. 8.4 Fire

A re is both a natural and man-made hazard.
A natural forest re is common in the mountain
forests of Nepal. A forest re can occurr due to
human activities like throwing a cigarette butt
and sometimes it might happen due to friction
between the trees in a forest. Forest res burn
vegetation, wild animals. Similarly, a re in a
house burns people and their property as well
as domestic animals. A re in one place can
spread far away, destroying lifes and property.

Causes of re

i) Lightning is the major cause of natural forest res.
ii) Throwing a burning cigarette butt or a matchstick may cause a forest re.

Aircraft accidents also cause a forest res.
iii) Leaving a burning re after a camp re, picnic also causes res.
iv) In the hot and dry season, friction between plants may cause a forest re.
v) Careless handling of petroleum products like petrol, diesel, kerosene, LP gas

may cause a forest re.

E ects of re

i) Forest re destroys plants and wildlife.
ii) It burns people, their homes and property.
iii) It pollutes our environment by releasing smoke and dust.

Prevention and control measures of re

i) We should not throw a burning cigarette butt in the forest.
ii) We should not allow children to carry matchsticks, kerosene, petrol.
iii) We should handle petroleum products carefully.
iv) The electric circuit, plugs, transmission lines should be checked from time to

time.
v) We should put out a re completely using water after a camp re and picnic.
vi) Burning rewood should be put out completely.
vii) A small range of re in a forest should be put out with the help of green

plants or mud.

Activity 4

Have you heard of a forest re in and around your community? If yes, write when
and where it was. Also, ask your elders how it was controlled?

62 Modern Concept Science, Health & Physical Education - 4

Unit 8 NATURAL DISASTERS

Rapid fire revision

* Those events that occur suddenly and cause loss of lives and property are
called disasters.

* Disasters which are caused by the activities of human beings are called man-made
disasters. For example, wars, aircraft accidents, bus accidents.

* Disasters that are caused by an imbalance in nature are called natural disasters.
For example, an earthquake, volcano, ood, landslide, etc.

* The over ow of water in the channel of rivers and streams during the rainy season
is called a ood. It is a natural disaster.

* A natural disaster in which a landmass falls from a higher altitude to a lower
altitude is called a landslide. Di erent factors like heavy rainfall, earthquakes,
deforestation, explosion of bombs cause landslides.

* Fire is both a natural and man-made hazard. It occurs due to human activities
like throwing the butt of a cigarette and sometimes it might happen due to
friction between trees in a forest.

Three steps exercise

Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Flood occurs in hilly areas. ( )
b) Deforestation can also cause landslides and oods.( )
c) A re can spread over a larger area. ( )
d) Disasters occur after informing us. ( )
e) Natural disasters cannot be prevented. ( )
f ) We should throw burning buds of cigarette butts in the forest. ( )
g) Lightning can cause a forest re. ( )

2. Fill in the blanks with appropriate words.
a) An aircraft accident is a ………. disaster.
b) ………. disaster is caused by nature.
c) Sliding of landmass from a higher to a lower slope is called ……….
d) A ood mainly occurs in ……….area.
e) ……….is the major cause of a natural forest re.
f ) ……….should be constructed on the river banks.

Modern Concept Science, Health & Physical Education - 4 63

NATURAL DISASTERS Unit 8

3. Match the following with their counterpart.
a) Example of natural disaster o Plain areas
b) Example of man-made disaster o Hilly areas
c) Flood occurs in o Wars
d) Landslide occurs in o Lighting
e) Forest re occurs due to o Earthquake

4. Select the correct alternative.

a) Which is a man-made disaster?

i. Aircraft accident ii. Earthquake

iii. Flood iv. Volcano

b) Which disaster always occurs in the hilly region of Nepal?

i. Fire ii. Earthquake

iii. Flood iv. Landslide

c) Embankment mainly prevents

i. Accident ii. Fire

iii. Flood iv. Landslide

d) Landslide in Nepal mainly occurs in

i. Rainy season ii. Summer season

iii. Winter season iv. Autumn season

e) Which disaster mainly occurs mainly in the rainy season?

i. Volcano ii. Flood

iii. Forest re iv. War

Step: 2

5. Write two di erences between the following:
a) Landslide and earthquake
b) Flood and landslide
c) Forest re and domestic re

6. Give reasons.
a) War is a man-made disaster.
b) Landslide is called a natural disaster.
c) We should not throw cigarette butts in a forest.

64 Modern Concept Science, Health & Physical Education - 4

Unit 8 NATURAL DISASTERS

7. Name the disasters shown in the gure below:

8. Which disaster needs the following control measures?
a) Embankments on the banks of streams and rivers.
b) Avoiding deforestation on sloping lands and hilly areas.
c) Putting out a re after cooking food during a picnic and camp re.

Step: 3

9. Answer the following questions.
a) What are natural disasters? Name any four.
b) De ne ood. What are the major causes of a ood? Write any two.
c) How can we control oods? Write any two measures.
d) What is a landslide? What are its major causes?
e) Write any three causes of landslides.
f ) Mention three preventive measures of a landslide.
g) What are the causes of a natural forest re? List any three.
h) How can we prevent a forest re? List any two ways.

10. Draw a gure of a ooded area.

Modern Concept Science, Health & Physical Education - 4 65

9Unit MATTER

Scientific terms and terminologies of the unit

1. Matter : Anything that has weight and occupies space is called matter.
2. Mass
3. Molecules : The amount of matter contained in a body is called mass.

4. Volume : Each and every matter is made up of small tiny particles called
5. Solids molecules.
6. Liquids
: The total space occupied by a substance is called volume.
7. Gas : Substances which have definite shape, size and volume are called solids.
: Substances which do not have definite shape and size but have definite

volume are called liquids.
: A substance which does not have definite shape, size and volume is

called gas.

Introduction

We see di erent things around us. They may be useful or useless to us. They have di erent
shapes, sizes and color. For example, a book, pen, pencil, chair, box, lamp, shoes, bags, clothes,
air, water, water vapor. These things have weight and occupy space. Anything that has weight
and occupies space is called matter. For example, a brick, rock, table, chair, bag, television. Air
is also matter because it has weight and occupies space.

Things like light, sound, etc. do not have mass and also do not occupy space. So they are not
called matter.

Chair Table Car Computer Stone
Fig. 9.1 Examples of matter

66 Modern Concept Science, Health & Physical Education - 4

MATTER Unit 9

Almost all matter di ers from one another in its shape, size, color, odor, weight, volume. For
example, a chair di ers from a table, a television set di ers from a radio and water di ers from
ice. All matter is made up of tiny particles called molecules. We cannot see molecules with
our naked eyes. To be matter, the substance must have two common properties. They are:
i. The substance must have weight. ii. The substance must occupy space.

i. The substance must have weight

The amount of matter contained in a body is called mass. Each and every matter is made up
of small particles called molecules. Matters have mass due to these molecules. A matter which
has more number of molecules has more weight. Similarly, a matter which has less number of
molecules has less weight. Molecules of di erent matter di er from each other. For example,
the molecules of a brick di er from the molecules of a stone. Similarly, the molecules of plastic
di er from the molecules of water.

ii. The substance must occupy space

The total space occupied by a substance is called volume. All matters have their own volume.
Some matters occupy more space and have more volume. Similarly, matters which occupy less
space have less volume. For example, a table occupies more space than a brick. In the same
way, a brick occupies more space than a pen.

Activity 1 Fig. 9.2
To show matter has weight

* Take a pan balance and two balloons of equal size.
* Fill a balloon with air and tighten its mouth.
* Keep one balloon in one pan and another in another

pan. What do you observe?
You see that the pan with the air- lled balloon remains
downward. Similarly, the pan with the unblown balloon remains
upward. It mean the air- lled balloon is heavier than the empty
balloon. This shows that air is matter, which has weight.

Activity 2
To show matter occupies space

* Take a glass and keep it on a plate.
* Fill the glass completely with water.
* Take a small piece of stone.
* Insert the stone into the glass.

Fig. 9.3

When you dip the stone, water over ows from the glass and gets collected on the plate. It
shows that, a piece of stone occupies space as it has volume.

Modern Concept Science, Health & Physical Education - 4 67

Unit 9 MATTER

Again ll the glass jar with water and dip a bigger piece of stone in it. It covers more space. So,
it displaces more water from the glass. In this way, we can show that matter occupies space.

States of matter
Generally, matter exists in three di erent forms. These three di erent forms are called
the states of matter. They are:
a) Solid, b) Liquid and c) Gas.

a) Solids

Substances which have de nite shape, size Stone Brick Table
and volume are called solids. Solids are hard
because their molecules are closely packed.
A stone, brick, paper, wood, glass, pen, pencil
are some examples of solids.

Bag Pencil

Fig. 9.4 Examples of solids

Properties of solids

i) Solids have de nite shape and size.
ii) They have a xed volume.
iii) They cannot be compressed further.
iv) They have a strong force of attraction between their molecules.

b) Liquids

Substances which do not have de nite Milk Water Honey
shape and size but have de nite volume are Beer Petrol
called liquids. They ow from a higher level Petrol Fig. 9.5 Examples
to a lower level. Liquids ow because the of luquids
molecules of liquids are far apart from each
other with less force of attraction. For
example, milk, water, honey, petrol, diesel,
kerosene, melted ghee, alcohol.

Properties of liquids

i) Liquids do not have de nite shape and size. Their shape and size depend
upon the vessel in which they are kept.

ii) Liquids have xed volume.
iii) Liquids cannot be compressed.
iv) Liquids have a weak force of attraction between their molecules. So, they

ow from a higher level to a lower level.

68 Modern Concept Science, Health & Physical Education - 4

MATTER Unit 9

Activity 3 Water in glass
To show liquids do not have xed shape but
have xed volume Water in plate Water in measuring
Fig. 9.6 cylinder
* Take a glass of water.
* Observe the shape of water in the glass.
* Obviously, water takes the shape of the glass.
* Pour water on a at plate. Now, water takes the

shape of the plate.
* Again, put the water in a measuring cylinder. The

water takes the shape of the measuring cylinder.

Has the volume of water changed? You can see that the volume of water remains the same
in all cases, but the shape of water is di erent in di erent containers.

c) Gas Smoke from vehicle
Smoke from chimney
A substance which does not have de nite shape,
size and volume is called gas. Gas spreads here and Fig. 9.7 Examples of gas
there because the molecules of gas are very far from
each other. Oxygen, carbon dioxide, bad smell, Air-filled
smoke, air are examples of gases. We cannot see gas balloon
with our naked eyes but we can feel their e ects.

Properties of gases

i) Gases do not have de nite shape, size and volume.
ii) They are highly compressible. They can be compressed into a very small

container.
iii) They have a very weak force of attraction between their molecules. Therefore,

they spread far away from each other.

Activity 4 Fig. 9.8
To show that gas does not have de nite shape and
volume

Take a bottle of perfume or body spray. Where do you think
the gas is? The gas is inside the bottle of the perfume. Go to a
corner of the room and ask your friends to stand in another
corner. The gas spreads out in the room. Do your friends smell
it? Yes, they smell the perfume. It means that the gas in a small
bottle spreads all over the room. This shows that the gas does
not have a xed shape and a xed volume.

Modern Concept Science, Health & Physical Education - 4 69

Unit 9 MATTER

Rapid fire revision

* Anything that has weight and occupies space is called matter. For example, a
brick, rocks, table, chair, bag, television.

* The amount of matter contained in a body is called mass.
* Each and every matter is made up of small particles called molecules. Matters

have mass due to these molecules.
* The total space occupied by a substance is called volume.
* Substances which have de nite shape, size and volume are called solids. For

example, a stone, brick, paper, wood, glass.
* Substances which do not have de nite shape and size but have de nite volume

are called liquids. For example, milk, water, honey, petrol, diesel, kerosene, melted
ghee, alcohol.
* A substance which does not have de nite shape, size and volume is called gas.
For example, oxygen, carbon dioxide, bad smell, smoke, air.

Three steps exercise

Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Air does not have weight. So, it is not considered as matter. ( )
b) Matters have weight and cover some space.
c) Oil does not have a xed volume. ( )
d) Gas molecules have very strong intermolecular force of attraction. ( )
e) Solids and liquids are generally non-compressible. ( )
f ) All substances are made up of tiny particles called molecules. ( )

2. Fill in the blanks with appropriate words:
a) There are………states of matter.
b) Matter has ……… and occupies ……….
c) Matter is made up of tiny particles called ………
d) ………molecules have least intermolecular force of attraction.
e) Smoke is an example of ………
f ) Liquids have a xed ……….but no xed……….
g) Oxygen, nitrogen, carbondioxide are some examples of ……….

3. Match the following words with their pairs:
a) Liquids o The total matter contained in a body
b) Gases o The total space occupied by a substance
c) Solids o Has weight and occupy space
d) Matter o No de nite shape, size and volume
e) Volume o De nite shape, size and volume
f ) Mass o De nite volume but no de nite shape and size

70 Modern Concept Science, Health & Physical Education - 4

MATTER Unit 9

4. Select the correct alternatives.

a) Matters have

i. Only volume ii. Only weight

iii. Both volume and weight iv. None

b) Which is an example of solid?

i. Petrol ii. Diesel

iii. Kerosene iv. Cotton

c) Which is an example of liquid?

i. Desk ii. Chair

iii. Kerosene iv. Clothes

d) Which is an example of gas?

i. Kerosene ii. Milk

iii. Perfume iv. Honey

e) Which has the largest distance in their molecules?

i. Solid ii. Liquid

iii. Gas iv. Plastic

f ) Which has the least distance in their molecules?

i. Solid ii. Liquid

iii. Gas iv. All

g) Whose molecules are highly compressible?

i. Solid ii. Liquid

iii. Gas iv. All

Step: 2

5. Di erentiate between:
a) Solid and liquids
b) Liquids and gases
c) Brick and alcohol
d) Smoke and stone

Modern Concept Science, Health & Physical Education - 4 71

Unit 9 MATTER

6. Give reasons:
a) Wood is a solid matter.
b) Liquids ow from a higher level to a lower level.
c) Gases spread everywhere.
d) Water is a liquid.

7. Identify the following gures and classify into solid, liquid and gas.

Step: 3

9. Answer the following questions.
a) De ne matter with any ve examples.
b) What are the three di erent states of matter?
c) What are solids? Write down any three characteristics and four examples.
d) De ne liquids with three characteristics and four examples.
e) What are gases? Write down any three characteristics and four examples.
f ) What are molecules?
g) De ne volume.

10. Explain an activity to show that air has weight.

11. Explain an activity to show that gas does not have a xed volume.

72 Modern Concept Science, Health & Physical Education - 4

10Unit ENERGY

Scientific terms and terminologies of the unit

1. Energy : The capacity of doing work is called energy.

2. Sources of energy : Things or places from where we get energy are called sources

of energy.

3. Heat : Heat is a form of energy, which gives the sensation of warmth.

4. Conservation of energy : Using energy and sources of energy wisely and economically

is called conservation of energy.

Introduction

The capacity of doing work is called energy. All living organisms need energy to live. We get
energy from food. The di erent fossil fuels like coal, petrol, diesel give energy to run vehicles
and industries. Cooking gas, kerosene, rewood give energy to cook food. Running water
gives energy to run water mills and to produce electricity. Solar energy and wind energy also
produce electricity. Electricity is used in various activities like cooking food, lighting, warming
rooms, running industries, running vehicles, etc. Human beings need di erent types of energy
to live.

Sun Fire LPG Magnet Battery Wind mill

Fig. 10.1 Sources of energy

Di erent forms of energy

There are di erent forms of energy. They are heat energy, light energy, sound energy,
magnetic energy, chemical energy, solar energy, mechanical energy, magnetic energy,
nuclear energy.

Solar panel Magnet Light bulb
Fig. 10.2
Ringing bell

Modern Concept Science, Health & Physical Education - 4 73

ENERGY Unit 10

Sources of energy

Things or places from which we get energy are called sources of energy. Sun, rewood, fossil
fuels, magnet, musical instruments, battery, friction, nucleus of atoms are sources of energy.
Among them, the sun is the ultimate source of energy on earth because all the other sources
of energy are derived from the sun. It is a direct source of heat and light energy.

Memory Plus

The materials which are used to produce energy are called fuels.

Heat energy

Heat is a form of energy which gives the sensation Sun LPG Burning fire
of warmth. The sun is a major source of heat energy Fig. 10.3 Some of the sources of heat energy
on earth. Firewood, heater, coal, LP gas, diesel, petrol,
etc. are other sources of heat energy. Heat energy is
used for cooking food, running vehicles, operating
engines in the factories, drying clothes, drying food
grains. Human body also needs heat energy. Food
provides heat energy to our body and makes us
warm.

E ects of heat on matter

Heat shows di erent e ects on matter. Some of the e ects of heat are listed below.
i) Heat increases the length of an object.
ii) Heat increases the volume of an object.
iii) Heat changes the shape of the body.
iv) Heat changes the state of a matter.
v) Heat increases the temperature of a body.

Change in state of matter Fig. 10.4 Change in the state of matter

Heat energy can change the state of matter. Ice
is a solid. When we heat ice, it changes into water.
Water is a liquid. When we again heat water, it
changes into water vapour. Water vapor is a gas.
Similarly, when we cool water vapor, it changes
into water droplets. When water is further cooled,
it freezes into ice. In this way, heat changes the
state of the matter.
We usually see that wet clothes get dry due to
solar heat. The solar heat changes water into
water vapor and makes the clothes dry. Similarly,
food grains also get dried due to sunlight.

74 Modern Concept Science, Health & Physical Education - 4

Unit 10 ENERGY

Activity 1 Copper wire

To show that heat increases the length of an object Fig. 10.5
* Take a thin copper wire and tie a piece of stone

with it.
* Tie the wire on a horizontal rod and hang as shown

in the given gure.
* The stone should be very near to the ground, but

it should not touch the ground.
* Heat the copper wire at any point for some time

and observe what happens.

Observation

After some time, the stone touches the ground.

Conclusion

When we heat the copper wire, it expands and the length increases. As a result, the stone
touches the ground.

Activity 2

To show that heat increases the volume of a body
* Take a glass bottle and keep some water in it.
* Add some drops of red ink in it. Now, it is red
colored. Rise in
water level

* Mark the water level in the glass bottle. Hot water
* Cover the mouth of the glass bottle with a tight
cork.
* Keep the glass bottle in a hot water trough.
Fig. 10.6
Observation
The water in the glass bottle becomes hot, and the level of water increases above the marked
level.

Conclusion

When matter gets heated, its molecules move farther away from each other. This increases
the volume of the matter.

Activity 3

To show that heat changes the shape of the object
* Take a bottle which has a narrow mouth.
* Cover the mouth of the bottle using a big balloon.
* Take a trough with boiled water in it.
* Keep the bottle in the hot water trough for some time.
* What do you observe?
Fig. 10.7

Modern Concept Science, Health & Physical Education - 4 75

ENERGY Unit 10

Observation

You can observe the balloon in ates a little when kept in a trough with hot water.

Conclusion

Hot water gives heat to the air inside the bottle. Hot air rises up and lls into the balloon. Then,
the balloon in ates. This activity shows that heat changes the shape of an object.

Activity 4

To show that heat changes the state of matter
* Take some ice cubes from the fridge.
* Put them in a beaker.
* Heat the beaker in the burner for a minute.
* Observe what happens to the ice cubes.

Observation Fig. 10.8

When we heat the beaker, the ice cubes get heated. After heating, the molecules of ice move
away from each other. This changes ice into water. When we heat water further, it changes
into water vapor and rises up in the sky.

Conclusion

This activity shows that heat changes the state of matter.

Activity 5 Fig. 10.9

To show that heat increases the temperature of
matter
* Take normal water in a beaker.
* Measure its temperature and record it in

your exercise book.
* Heat the beaker using a Bunsen burner for

about two minutes.
* Now, measure the temperature of the water.
* What di erence do you observe?

Observation

The temperature of the cold water is less. The
temperature of the warm water is more.

Conclusion

This activity shows that heat increases the
temperature of matter.

76 Modern Concept Science, Health & Physical Education - 4

Unit 10 ENERGY

Applications of heat in our daily life

i) Heat keeps our body warm. A healthy human body has a constant temperature of
about 98.6o Fahrenheit.

ii) We need heat for cooking food. Di erent sources of heat like rewood, solar energy,
electricity, kerosene, LP gas, natural gas are used for cooking purposes.

iii) We need heat to dry food grains, wet utensils, washed clothes and rewood. Solar
energy is mainly used for drying purpose.

iv) Heat is used for running automobiles. Petrol, diesel, LP gas are used to run vehicles.
v) Heat is required in industries for their operation. In industries, heat is obtained from

various sources like petrol, diesel, kerosene and coal.

Conservation of energy

Conservation means saving for the future. So, using energy and sources of energy wisely and
economically is called conservation of energy.
Energy can be conserved by the following ways.

i) We should turn o electrical appliances when they are not in use.
ii) We should use highly e cient electrical devices as far as possible. For example, use of
iii) CFL in place of normal bulbs, use of LED monitor in place of CRT monitors, use of

pressure cooker in place of normal utensils.
iv) Non-renewable sources of energy like petrol, LPG, diesel, coal, kerosene should

be used wisely.
v) We should walk or take a cycle for a short distance and use vehicles for only long

distances.
vi) We should encourage gadgets that run on solar energy. For example, solar light, solar

cooker, solar water heater.
vii) We should use biogas as an alternative source of energy for cooking and lighting in

place of rewood or electricity.
viii) We can use wind energy for lifting water.
ix) We should use public transportation in place of private vehicles.

Rapid fire revision

* The capacity of doing work is called energy. All living organisms need energy to live. We
get energy from food.

* There are di erent forms of energy like heat energy, light energy, sound energy, magnetic
energy, chemical energy, solar energy.

* Things or places from which we get energy are called sources of energy. For example,
the sun, rewood, fossil fuels, nucleus of atoms.

* Heat is a form of energy which gives the sensation of warmth. The sun is a major source
of heat energy on earth.

Modern Concept Science, Health & Physical Education - 4 77

ENERGY Unit 10

* Heat increases the length, volume, shape, temperature and state of matter.
* Using energy and sources of energy wisely and economically is called conservation

of energy.

Three steps exercise

Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Energy is the capacity of doing work. ( )
b) All living things get energy from food. ( )
c) Heat cannot change the volume of an object. ( )
d) The sun is the major source of energy on earth. ( )
e) A simple bulb should be used in place of a CFL one. ( )
f ) CRT monitor is better than LED monitor. ( )

2. Fill in the blanks with appropriate words:
a) The capacity of doing work is called …………
b) Living things get energy from…………
c) Heat is a form of energy which gives the sensation of ………
d) The full form of LP gas is………
e) Heat energy can change the state of………
f ) The major source of heat energy on earth is………
g) Water changes into ………on heating and changes into……… on cooling.
h) .………increases the temperature of a body.

3. Match the following: o Conservation of energy
a) Energy o Major source of heat
b) Heat increases o Capacity of doing work
c) States of matter o Solid, liquid and gas
d) The sun o Temperature
e) Wise use of energy

`4. Select the best alternatives.

a) The capacity of doing work is called

i. Energy ii. Pressure

iii. Power iv. Force

78 Modern Concept Science, Health & Physical Education - 4

ENERGY Unit 10

b) Water freezes to ice when Rise in
water level
i. Heating ii. Cooling Hot water

iii. Compressing iv. Expanding

c) Which of the following does not need solar energy?

i. Solar cooker ii. Pressure cooker

iii. Solar panel iv. Solar cell

d) When we heat matter, its temperature

i. Decreases ii. Remains constant

iii. Increases iv. Depends upon condition

e) Which is the main source of energy on earth?

i. Wind energy ii. Solar energy

iii. Petrol iv. Hydropower

Step: 2

5. Write down one di erence between:
a) Heat and energy
b) Solar energy and petrol

6. Give reasons.
a) The sun is the ultimate source of energy.
b) We need energy.
c) CFL is better than a normal bulb.
d) We should use public vehicles in place of private ones.

7. Which e ect of heat do the gures show?

Copper wire

a) b)

Modern Concept Science, Health & Physical Education - 4 79

Unit 10 ENERGY

c) d)

e) f )
8. Answer the following in one word.
a) What is the capacity of doing work called?
b) Things or places from which we get energy are called
c) The form of energy which gives the sensation of warmth is called
d) Using energy wisely and economically is called

Step: 3

9. Answer the following questions.
a) De ne energy.
b) What is heat? Write down any three e ects of heat.
c) What are the sources of energy? Name any three.
d) Namethree di erent forms of energy.
e) Write any four applications of heat energy in our daily life.
f ) Write any four ways of saving energy.

10. Describe an activity to show that heat increases the length of a body.

11. How can you show that heat increases the volume of a body? Explain with a gure.

80 Modern Concept Science, Health & Physical Education - 4

11Unit WEATHER AND
SEASONS

Scientific terms and terminologies of the unit

1. Weather : The atmospheric condition of a place at a given time is called
2. Meteorology weather.
3. Meteorologist
4. Elements of weather : The branch of science in which we study about the weather
5. Humidity is called meteorology.
6. Evaporation
7. Condensation : The scientists who study about the weather are called
8. Water cycle meteorologists.
9. Season
10. Equator : The components that cause change in the weather are called
11. Hemispheres elements of weather.

12. Axis : Humidity means the amount of water vapor present in the air.
: The process of converting water into water vapor by heating

is called evaporation.

: The process of cooling down of water vapour into water
droplets is called condensation.

: The cyclic process in which water moves on, in and above
the earth, is called the water cycle.

: A season is a division of the year, which is characterized by
the change in weather, ecology and hours of daylight.

: The earth is divided into two equal halves by an imaginary
line passing through east to west and is called the equator.

: The equatorial line divides the earth into two halves, which
are called hemispheres. The half towards the north is called
the northern hemisphere and the half towards the south is
called the southern hemisphere.

: The imaginary line that joins the north and south poles of
the earth is called the axis.

Introduction

The atmospheric condition of a place at a given time is called weather. Weather keeps
on changing. So, all days do not have exactly the same weather. Some days are sunny,
some are rainy and sometimes it may be windy. Sometimes we feel very cold and
sometimes very hot. Sometimes it may be hot in the day but it may rain in the evening.

Modern Concept Science, Health & Physical Education - 4 81

WEATHER ANS SEASONS Unit 11

The branch of science in which we study about the weather is called meteorology.
Meteorologists study the weather.

Rainy day Snowfall Hot day
Fig. 11.1

Activity 1

Listen to the radio or watch television and record the minimum and maximum tem-
peratures for a week.

Day Minimum Temp. Maximum Temp.
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday

Causes of change in weather

Solar heat is the major cause of change in the weather. The sunlight, humidity, rainfall,
wind play their role in weather change. These components also depend upon the heat
of the sun. Thus, the components that cause change in the weather are called
elements of weather.

On a sunny day, it is warmer because the sun rays heat the land and air. In the morning
and evening, the weather is generally colder than the day. This is because in the morn-
ing and evening, sunlight is slanted, but during the day, it is straight. In the evening, as
the sun sets, land and water also radiate heat into space. The di erence in the heat
between the land and water causes the wind to blow and clouds to form.

Humidity means the amount of water in air. Some- Fig. 11.2 Cloud in the sky
times, the air is more humid because it contains
more water. Humid air causes formation of more
clouds. When there is more cloud in the sky, it
blocks sunlight and makes the day cloudy. Cloudy
days are dark but relatively warmer. It is because
clouds block escaping of heat from the earth.

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Unit 11 WEATHER ANS SEASONS

Sometimes, we may get rain in the cloudy days. Mountainous regions have snowfall
in spite of rainfall. So, the weather of a place changes from day to day and even hour
to hour. Sometimes, we can observe that weather changes many times a day.

Types of weather

Weather changes when the elements of weather change. On the basis of change in
the elements, there may be di erent types of weather. It may be sunny, cloudy, rainy,
windy, foggy.

Sunlight is the major source of heat
on earth. We feel hot on a sunny
day. A hot sunny weather may bring
wind. Sometimes, the speed of the
wind is too much. It causes storms
and makes the day windy.

Sunny day Fig. 11.3 Windy weather

When clouds cover the sky, it is called cloudy weather. A cloudy weather can bring
rain. Rain makes the environment wet and humid. In the mountain areas, rainfall
occurs as snow. It makes the weather very cold.

Cloud in the sky Rainy day Snowfall
Fig. 11.4
Clouds formation and rainfall

The heat of the sun heats the air, water
and land. As a result, water evaporates
from water bodies like ponds, lakes,
oceans. The process of converting water
into water vapor by heating is called
evaporation. The water vapor and air get
heated and become lighter. The mixture
of water vapor and air rises up in the sky.
In the sky, water vapor cools down and
converts into water droplets. This process
is called condensation. Thus, the process
of cooling down of water vapor into water
droplets is called condensation. Fig. 11.5 Water cycle

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WEATHER ANS SEASONS Unit 11

Large numbers of water droplets cling together and Hailstones
form clouds. Wind moves clouds form one place to
another place in the sky. While moving, many small Snowfall
clouds join together to form larger clouds. In the Fig. 11.6
large clouds, the water droplets become bigger and
heavier. In this condition, clouds cannot hold the
water. In this way, water falls down and is called
rainfall. In the hilly regions, the clouds collide with the
hills and cause heavy rainfall. Sometimes, in the
clouds the water droplets cool rapidly and form ice
crystals called hailstones.
In the mountain regions, the atmospheric tempera-
ture is very low. It is below freezing point. When rainfall
occurs in such places, water droplets rapidly convert
into snow. So we get snowfall in the mountains.

Most of the rainwater travels into water bodies like streams, rivers, ponds and lakes.
Whereas some rain water in ltrates in the land and forms groundwater. We get ground
water from a well or by boring. Snow on the mountains also melt and join the rivers.
Finally, many rivers nd their way to the seas and oceans.

In nature, water moves from the seas and oceans to lands and from the land to the seas
and oceans. It is called a water cycle. Thus, the cyclic process in which water moves on,
in and above the earth, is called the water cycle. Water cycle is very important in nature
because it carries water soluble nutrients from one place to another.
Memory Plus
A water cycle includes evaporation, condensation and rainfall.

Seasons

The weather of a place changes throughout the year. The days are shorter and colder
in the winter season. Similarly, the days are longer and hotter in the summer season.
Season means occurrence of the same type of weather for some months. Thus, a
season is a division of the year, which is characterized by the change in weather, ecol-
ogy and hours of daylight.
Di erent plants and animals prefer di erent seasons for a particular activity. Most of
the birds prefer a hot season. So, they show seasonal migration from one place to
another. Paddy is sown in the hot and wet season and harvested in a moderate season.
Human beings wear warm and woolen clothes during the cold season and light cotton
clothes in the hot season. Season in uences the life of plants and animals in various
ways.

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Unit 11 WEATHER ANS SEASONS

Memory Plus
Most of the birds prefer hot to moderate wet season so, they show seasonal migration
from one place to another to escape cold seasons.

People on rainy day People in winter clothes
Sowing paddy in rainy season
Fig. 11.7 Northern Hemisphere

Causes of change in seasons Rotation axis Southern Hemisphere

The earth revolves around the sun in its xed Fig. 11.8
orbit. One complete revolution takes about
365.25 days. The earth has oval shape. It is
divided into two halves by an east-west imagi-
nary line called the equator. The half towards the
north is called the northern hemisphere and the
half towards the south is called the southern
hemisphere. Another imaginary line that joins
the north and south poles of the earth is called
the axis. The axis of the earth is not perpendicular
but tilts towards the east by 23.5o.

The earth is continuously moving around the sun in its elliptical path. The tilt causes
some parts of the earth to receive straight sunlight and other parts slanted sunlight.

Straight sunlight has more energy and is
hotter than slanted sunlight. Due to this
reason, the hemisphere of the earth
which receives straight sunlight for most Autumn in N hemisphere Winter in N hemisphere
Spring in S hemisphere Summer in S hemisphere

of the time have summer season. At the
same time, the opposite hemisphere has
winter season. At the equator, the
sunlight always falls straight. So, equato- Winter in S hemisphere Spring in N hemisphere
Summer in N hemisphere Autumn in S hemisphere

rial regions are hotter and wetter for Fig. 11.9
most of the times in the year. Autumn and spring season occur in between the
summer and winter seasons in the hemispheres of the earth. So, when it is summer in
the northern hemisphere, it is winter in the southern hemisphere. The change in the
distance between the sun and the earth is not the reason of change in seasons. The
tilted axis of the earth and the revolution of the earth around the sun are the major
causes of di erent seasons.

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WEATHER ANS SEASONS Unit 11

Types of seasons

On the basis of the position of the earth in its orbit around the sun, the di erent parts
of the earth get sunlight for di erent periods. According to the periods of sunlight,
there are four di erent types of seasons. These four seasons have an average duration
of about 3 months. They are the summer season, autumn season, winter season and
spring season.

a) Summer season

Nepal lies in the northern hemisphere. In the northern hemisphere, the summer
season occurs from about mid-May (Jestha) to mid of august (Shrawan). During the
summer season, the most parts of the northern hemisphere receive straight sunlight.
So, during this season, the days are hot and long, and nights are short. June 21
(Ashar7) has the longest day and shortest night on earth.

Heavy rainfall occurs in the summer season. So, most of
the plants and animals are active during this season.
Many crops are cultivated during summer. Animals and
plants also reproduce during the summer season. As the
summer days are hot, people prefer fan, coolers, AC or to
go swimming. Similarly, they like to eat ice-cream, cold
drinks. People wear light and thin cotton clothes during
the summer season. Fig. 11.10 Summer season

b) Autumn season

In Nepal, the autumn season occurs from mid-August
(Bhadra) to mid-November (Kartik). During autumn, both
hemispheres of the earth receive equal amounts of
sunlight. So the duration of the days and nights are equal
during the autumn season. September 23 (Ashwin7) has
equal duration of day and night.

During the start of the autumn season, the weather is
neither hot nor cold. But at the end of autumn, both
Fig. 11.11 Autumn season
the days and nights start to get colder. Most of the crops are harvested during this
season. Deciduous plants shed their leaves to prepare themselves for the cold winter.
Many animals prepare for their hibernation. The activities of living organisms gradu-
ally start to decrease.

c) Winter season

In Nepal, the winter season occurs from the mid of November (Mangsir) to about the
mid of February (Magh). During winter, the northern hemisphere receives slanted
sunlight. The days become shorter and nights longer. December 22 (Poush 7) has the
shortest day and longest night.

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Unit 11 WEATHER ANS SEASONS

The weather is cold during the winter season. The higher Fig. 11.12 Winter season
mountains and polar regions of the earth get snowfall
during winter. Nepal receives little rainfall during this
season. Most of the animals are also inactive. Cold
blooded animals are not seen in the winter season
because they go for winter sleep. Plants also show limited
growth and reproduction in winter. People prefer bask-
ing in the sun, warming by a re, heater. People also like
to take hot drinks, co ee, tea, soup, hot food. They wear
warm and thick woolen clothes to keep their body warm.

d) Spring season

Spring comes after the winter season. This season in Nepal is from about the mid of
February (Falgun) to about the mid of May (Baisakh). Days and nights are almost equal
the in the spring season because both the hemispheres receive equal duration of
sunlight. At the end of the spring season, the days gradually become hotter. March 21
(Chaitra 8) has equal day and night .

Normal activities of living beings start in spring Fig. 11.13 Spring season
season. This is the season when new leaves and
buds grow and the owers bloom. Animals prepare
themselves for reproduction. It is green and colorful
everywhere in nature. So, it is also known as the
queen of the seasons.

Activity 2

With the help of your family members and your own experience, list the names of the
di erent types of crops that are cultivated in the di erent seasons.

Activity 3

Collect some pictures or photos of the seasons you like most and paste or draw them
in your project work book.

Rapid fire revision

* The atmospheric condition of a place at a given time is called weather. Weather
keeps on changing.

* The branch of science in which we study about the weather is called meteorology.
Meteorologists are scientists who study the weather.

* Solar heat is the major cause of change in the weather. After sunlight, humidity,
rainfall, wind, etc. play their role in weather change.

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WEATHER ANS SEASONS Unit 11

* The components that cause change in the weather are called elements of weather.
* Humidity means the amount of water in the air. Sometimes, the air is more humid

because it contains more water.
* Weather changes when the elements of weather change.
* On the basis of the change in the elements, there are di erent types of weather-

sunny, cloudy, rainy, windy, foggy.
* The process of converting water into water vapor by heating is called evaporation.
* In the sky, water vapor cools down and converts into water droplets. This process

is called condensation.
* The cyclic process in which water moves on, in and above the earth, is called the

water cycle.
* A season is a division of the year, which is characterized by the change in weather,

ecology and hours of daylight.
* The tilted axis of the earth and the revolution of the earth around the sun are

the major causes of di erent seasons.
* There are four di erent seasons in a year. They are the summer season, autumn

season, winter season and spring season.
* In northern hemisphere, summer season occurs from about the mid-May (Jestha) to

the mid-August (Shrawan).
* Autumn occurs in Nepal from mid-August (Bhadra) to mid-November (Kartik).
* Winter season occurs in Nepal from mid-November (Mangsir) to about mid-

February (Magh).
* Spring season occurs in Nepal from about the mid of February (Falgun) to the mid

of May (Baisakh).
* June 21 has the longest day and shortest night on the earth.
* September 23 has equal duration of day and night.
* December 22 has the shortest day and longest night.
* March 21 has equal day and night.

Three steps exercise

Step: 1

1. Tick (√) the correct statement and cross (x) the false one.
a) Weather is always constant. ( )
b) Sunny days are hotter. ( )
c) The process of cooling of water vapor into water droplets is called
d) evaporation. ( )
e) There are 6 major seasons in Nepal. ( )
f ) December 22 has the shortest day and longest night. ( )

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Unit 11 WEATHER ANS SEASONS

f ) Many animals go for winter sleep in the winter season. ( )
g) Autumn season is also called the season of owers. ( )

2. Fill in the blanks with appropriate words.
a) …………are scientists who study weather.
b) The fast moving air is called …………
c) …………days are dark, but they are warm.
d) …………is the long-term weather condition of a place.
e) …………is the shortest day and longest night in the northern hemisphere.
f ) The revolution of the earth is the major cause of change in …………

3. Match the following: o December 22
a) Elements of weather o About 365.25 days
b) Equator o June 21
c) Axis o Joins east and west
d) Longest day o Joins north and south
e) Longest night o Sunlight, humidity, rainfall
f ) Revolution of earth

4. Select the appropriate answer from the given alternatives.

a) Which is not considered as an element of the weather?

i. Sunlight ii. Rainfall

iii. Humidity iv. Revolution of the moon

b) It is dark but warm in…….. weather.

i. Cloudy ii. Sunny

iii. Windy iv. Stormy

c) The process of changing water into water vapor is called

i. Condensation ii. Evaporation

iii. Freezing iv. Precipitation

d) Day and night are more or less equal on

i. September 22 ii. September 23

iii. September 21 iv. September 24

e) …….. is the major cause of change in seasons.

i. Revolution of the earth ii. Distance between the earth and sun

iii. Tilted earth’s axis iv. Distance between the earth and moon

f ) Which season is also called the queen of seasons?

i. Winter ii. Autumn

iii. Spring iv. Summer

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WEATHER ANS SEASONS Unit 11

Step: 2

5. Di erentiate between:
a) Weather and season
b) Sunny day and cloudy day
c) Evaporation and condensation
d) Summer and winter season
e) Autumn and spring season
6. Give reasons:
a) Why is it hot in summer and cold in winter?
b) Why do some plants shed their leaves during the autumn season?
c) The spring season is also called the queen of seasons, why?

7. Write down both English and Nepali dates for the followings.
a) Days and nights are equal
b) Longest day
c) Longest night

8. Give one word answer to the following.
a) The imaginary line that joins east to west of the earth.
b) The imaginary line that joins the north and south poles of the earth.
c) The angle by which the axis of the earth is tilted from the normal.
d) The queen of seasons.
e) Season in which most of the living organisms are active.

Step: 3

9. Answer the following questions.
a) What is weather?
b) What are elements of weather?
c) What are the major causes of change in the weather?
d) Write down the names of di erent types of weather.
e) De ne sunny weather.
f ) What does cloudy weather mean?
g) How is cloud formed? Explain.
h) Explain water cycle with a labeled diagram.
i) Write down the major characteristics of the seasons.

10. Look at the gure and identify the types of season.

a) b) c)
90 Modern Concept Science, Health & Physical Education - 4

12Unit EARTH

Scientific terms and terminologies of the unit

1. Hydrosphere : The water portion of the earth surface is called the hydrosphere.
2. Lithosphere
: The solid portion of the earth’s surface made up of rocks and soil is
3. Atmosphere called the lithosphere.

: The mixture of different gases which is present around the earth’s
surface is called the atmosphere.

Introduction

The earth is the only planet where living beings are Fig. 12.1
present. It revolves round the sun in its elliptical orbit. It Fig. 12.2 Earth
takes 365 days and 6 hours to complete one revolution
around the sun. The earth also rotates on its own axis. It
completes one rotation in 24 hours. The rotation causes
days and nights on the earth. Similarly, revolution of the
earth causes seasonal change. The shape of the earth is
like an orange with east-west bulging. So, its east- west
diameter is 12,756 km and north-south diameter is
12,714 km.
The earth is the only living planet in the solar system. Its
estimated age is 4.5 billion years. The earth has a favorable
environment for living organisms. It has oxygen for breathing,
water for drinking, and land and ocean to live and grow. The
earth has an average temperature of 15oC. More than two-
thirds of the earth surface is covered with water and the
remaining one-third is land. Due to the large water bodies like
the ocean, the earth looks blue from space. So, it is also called a
blue planet.

Composition of the earth

Broadly, the earth is composed of land, water and air. These broad components of the
earth are called the hydrosphere, lithosphere and atmosphere.

1. Hydrosphere

The water portion on the earth’s surface is called the hydrosphere. All the water bodies
like springs, streams, rivers, ponds, lakes, seas and oceans constitute the hydrosphere.

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EARTH Unit 12

Oceans form the largest mass of water. They are very deep. The average depth of an
ocean is about 4 kilometers. Water bodies like streams, rivers, ponds, lakes, seas,
oceans are called sources of surface water. The water which is present inside the
earth’s surface is called underground water. It can be obtained through a spring, well,
tube well, boring, etc. In the Himalayan region, most of the water is found in the form
of snow. The surface water changes into water vapour due to the solar heat. Thus,
surface water, underground water, snow, water vapour, etc. are called sources of water.

Ocean River Lake

Fig. 12.3 Hydrosphere

Water is an important substance on the earth. All living beings need water to live. Both
sea and ocean water and fresh water are habitats for animals and plants. Large
amounts of water are present in the bodies of all living beings. Water transfers nutri-
ents from one place to another in the form of a water cycle.

2. Lithosphere Plain Plateau

The solid portion of the earth’s surface made Island Mountain
up of rocks and soil is called the lithosphere.
The lithosphere covers about one-third of Valley
the total surface of the earth. It is not uniform Fig. 12.4 Lithosphere
and smooth throughout. It varies in its struc-
ture. Mountains, hills, deserts, plains, islands,
peninsulas, plateaus are the di erent land-
forms of the lithosphere. Mount Everest is
the highest landform in the lithosphere. It is
8,848 m high from the sea level. Large
distinct land masses of the earth are called
continents.

Minerals and nutrients required for living
beings are present in the lithosphere. These
minerals get cycled continuously to support
plants and animals. The water cycle trans-
ports minerals from land to the water bodies.
The lithosphere is home to many animals
and plants.

92 Modern Concept Science, Health & Physical Education - 4