Oasis Science and Technology 4

Unit Weather
8.2

Key terms and terminologies

1. Weather: The condition of the atmosphere of a place at a particular time is
called weather.

2. Sunny day: Weather with enough sunlight is called a sunny day.
3. Cloudy day: Weather with lots of clouds in the sky is called a cloudy day.
4. Rainy day: Weather with lots of rainfall is called a rainy day.
5. Windy day: If the wind blows a lot, it is called a windy day.
6. Snowy day: If it snows in winter, it is called a snowy day.
7. Weather forecasting: The process of predicting weather conditions of the

coming days is called weather forecasting.
8. Cloud: A cloud is a group of billions of condensed water droplets in the sky.
9. Nimbus: The cloud which brings rain is called nimbus.
10. Cirrus cloud: A white frozen cloud very high from the earth is called a cirrus

cloud.
11. Cumulus cloud: A white and fluffy cloud is called a cumulus cloud.
12. Cumulonimbus: A cumulus cloud that brings rain is called a cumulonimbus

cloud.
13. Stratus cloud: The thin cloud that covers the sky is called the stratus cloud.

14. Nimbostratus: The stratus cloud that brings rain is called the nimbostratus.

Introduction

How is the weather today? Is it a sunny day or a rainy day? The
condition of the atmosphere of a place at a particular time is called
weather. There are five types of weather. They are sunny days, cloudy
days, rainy days, windy days and snowy days.

Sunny day

A sunny day is hot. There is a lot of sunlight. Weather with enough
sunlight for the day is called a sunny day. We should stay in shade.
We should drink enough water. Wearing light clothes keeps us cool.
People enjoy eating ice cream on sunny days.

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Sunny day people wear light cotton clothes in summer

Resonable facts
Why do people wear light cotton clothes on a sunny day?
People use light cotton clothes on a sunny day because it
keeps them cool.

Cloudy day

The weather with lots of clouds in the
sky is called a cloudy day. It may rain on
a cloudy day. Clouds affect weather.

Rainy day cloudy day

If clouds become heavy, it will rain. people use umberella in rainy days
Weather with lots of rainfall is called a
rainy day. It is difficult to go to school on
a rainy day. We should not play in the
rain. People wear a raincoat or use an
umbrella in the rain.

Resonable facts
Why should we carry an umbrella every day in the
summer season?
We should carry an umbrella every day in the summer
season because there are many rainy days in summer.

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Windy day windy day

If the wind blows a lot, it is called a windy day.
Winds may destroy crops. Storms are very
dangerous.

Fact file
Sandstorms can swallow entire cities.

Snowy day

It snows in winter. A snowy day is very cold. We should wear warm
clothes. We should eat warm food.

snowy day people wear warm clothes during warm food keeps us warm in cold

winter winters

Fact file
The snowiest city on earth is Aomori, Japan.

Activity
Complete the table given below.

Weather Food Clothing
Sunny day
Windy day
Rainy day
Cloudy day
Snowy day

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Factors affecting weather

Weather is a day-to-day condition of a place. It keeps changing in a
very short time. It may be cold now but very hot after an hour. It is
different from place to place as well. It may be sunny at our house but
cloudy in our friend’s house. Weather keeps changing because it is
affected by various factors. The factors affecting weather are wind,
clouds, water vapour, sunlight and seasons.

Change in weather

Winds bring clouds. Clouds block sunlight and bring rain. Water
vapour traps heat. It changes into the cloud. Sunlight creates the
wind. Sunlight also runs a water cycle. These activities keep changing
weather continuously. Weather also depends upon the season. The
summer season has rainy days and sunny days. The winter season
has cold snowy days. The spring is windy.

Weather forecasting

We can observe the clouds, the direction of
the wind and predict weather.

Weather scientists collect information

about wind, water vapour, sunshine and weather forecast
clouds from the weather stations. Satellites

help them collect information about the wind, monsoon etc. They use

this information and predict weather. Weather can be predicted

accurately for many days. The process of predicting weather conditions

in the coming days is called weather forecasting.

The importance of weather forecasting is noted below
i. We will know about daily weather. We can plan our daily

activities.
ii. It tells about future storms and heavy rainfall. We can be prepared

to be safe from them.

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iii. It gives information about temperature and rain. Farmers can
plan their work.
Activity
Listen to the news and learn about tomorrow’s weather.

Resonable facts

Why is weather forecasting important for farmers?

Weather forecasting is important for farmers because
they can plan for irrigation, ploughing, sowing and
harvesting crops.

Clouds and weather

Cloud is a part of the water cycle. Its main work is to bring rain. It
affects weather. If clouds block the sky, it is a cloudy day. If clouds
bring rain, it is a rainy day. If the cloud is white and does not block
the sun, it's a sunny day. If it snows, it is a snowy day.

Sunlight heats up the surface water. It will change into a vapour.
Vapour is warm. It rises up in the sky. When it gets cold, it will change
into tiny water droplets. These water droplets will come closer and
change into the cloud. A cloud is a group of billions of condensed
water droplets in the sky.

Fact file
The highest cloud on earth is 60,000 metres above the
earth’s surface.

Types of the cloud

There are three basic types of clouds. These are stratus, cumulus and
cirrus. There are other different types of clouds as well. The cloud
which brings rain is called nimbus. The nimbus cloud is dark and
heavy. Any cloud can grow heavier and change into a nimbus cloud.

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Activity
Make a model of different types of clouds.

Cirrus cloud

A white frozen cloud very high from

the earth is called a cirrus cloud. It is

formed when water vapour freezes into

ice. It does not bring rain. It is usually

seen when the weather is fine. cirrus cloud

Resonable facts

Why are some clouds white?

Some clouds are white because they reflect most of the

light.

Cumulus cloud

When hot water vapour rises up and cools down, a cumulus cloud is

formed. It is fluffy like cotton. A white

and fluffy cloud is called a cumulus

cloud. When cumulus clouds combine,

they form heavy dark clouds. They

bring heavy rainfall and thunderstorm.

This kind of cumulus cloud is called cumulus cloud
cumulonimbus.

Stratus cloud

When a moist wind flies over a cold stratus cloud
land, it will change into a stratus cloud.
It has many layers. It covers the entire
sky. The thin cloud that covers the sky
is called the stratus cloud. It is grey. It
does not bring rain. If it grows thicker,

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it may bring light rain. This kind of stratus cloud is called the
nimbostratus.

Fact file
The fog is a type of stratus cloud that comes very close
to the ground.

Summary

1. The condition of the atmosphere of a place at a particular time is
called weather.

2. Weather with enough sunlight is called a sunny day.
3. Weather with lots of clouds in the sky is called a cloudy day.
4. The weather when it rains a lot is called a rainy day.
5. If the wind blows a lot, it is called a windy day.
6. The factors affecting weather are wind, clouds, water vapour,

sunlight and season.
7. The process of predicting weather conditions in the coming days

is called weather forecasting.
8. A cloud is a group of billions of condensed water droplets in the

sky.
9. The thin cloud that covers the sky is called the stratus cloud.
10. A white and fluffy cloud is called a cumulus cloud.
11. A white frozen cloud very high from the earth is called a cirrus

cloud.
12. Any cloud can grow heavier and change into a nimbus.
13. Nimbus is a rain-bearing cloud.

Model Questions with Their Answer

1. What is weather?

The condition of the atmosphere of a place at a particular time is
called weather.

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2. What is a nimbus cloud?
The rain-bearing cloud is called a nimbus.

3. Why is weather forecasting important?

Weather forecasting is important because it helps us to plan our
daily activities.

4. Differentiate between stratus cloud and cumulus cloud.
The differences between stratus cloud and cumulus cloud are:

SN Stratus cloud SN Cumulus cloud
1 Stratus cloud is thin.
1 Cumulus cloud is thick.
2 It covers the entire sky.
2 It does not cover the entire
3 It is grey. sky.

3 It is white.

5. How does the cloud affect weather?

The cloud affects weather. If clouds block the sky, it is a cloudy
day. If clouds bring rain, it is a rainy day. If the cloud is white and
does not block the sun, it's a sunny day. If it snows it is a snowy
day.

Exercise

1. Fill in the blanks with an appropriate word.
rain umbrella weather cloudy atmosphere

a. The condition of ………. of a place at a particular time is
called weather.

b. There are lots of clouds in the sky in a ……… day.
c. People wear a raincoat or use …….. in the rain.
d. The factors affecting ……… are wind, clouds, water vapour,

sunlight and season.
e. Clouds block sunlight and bring……….

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2. Write true for the correct and false for the incorrect statement.

a. The winter season has warm days.
b. Weather scientists collect information about wind, water

vapour, sunshine and clouds from the weather station.
c. A cloud is a group of billions of condensed water droplets in

the sky.
d. A cloud formed when water vapour freezes into ice is called

a cirrus cloud.
e. Cirrus brings heavy rainfall and thunderstorm.

3. Choose the best answer from the given alternatives.
a. What factors do not affect weather?

Wind Cloud Sunlight Rocks

b. What days are common in summer?

Sunny day Snowy day Windy day Cloudy day

c. What days are common in winter?

Snowy day Sunny day Cloudy day Rainy day

d. Which cloud is made of ice?

Cirrus Cumulus Stratus Nimbus

e. Which cloud looks like cotton?

Nimbus Cumulus Stratus Cirrus

4. Match the following.

Day-to-day condition of a place collects information on weather

Cumulus heavy rainfall

Cirrus weather

Nimbus frozen cloud

Weather station fluffy cloud

5. Answer the following questions in a word each.

a. What is the weather like if cumulus clouds are in the sky?

b. What is the weather like if the wind blows fast?

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c. What is the rain-bearing cumulus cloud called?
d. Which cloud cannot bring rain?
e. What is the rain-bearing stratus cloud called?

6. Write any two differences between:
a. Rainy day and windy day
b. Cirrus and stratus
c. Nimbus cloud and cumulus cloud

7. Give reason.
a. Weather forecasting is important.
b. We should be careful on a stormy day.
c. We should carry an umbrella in the rainy season.

8. Study the given diagram and answer the following questions.

i. Write the name of the cloud.

ii. Does it rain?
iii. Which cloud is formed when this cloud

gets thicker and darker? Will it rain then?
9. Answer the following questions.

a. What is weather?
b. What factors affect weather?
c. How do clouds affect weather?
d. What is a cloud?
e. Write a short note on cirrus cloud.
f. What is cumulus cloud?

g. Describe stratus cloud.

10. Project work.
Observe the weather condition of first day of every month for a

year and note it.
Baisakh 1 :
Jestha 1 :

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Unit Natural Disaster
8.3

Key terms and terminologies

1. Natural disasters: The natural activities that harm us are called natural
disasters.

2. Wind: The air in motion is called wind.
3. Storm: A very strong wind is called a storm.
4. Flood: The overflow of water in the river is called a flood.
5. Landslide: The falling of the landmass from the hills is called a landslide.
6. Earthquake: The shaking of the land is called an earthquake.
7. Emergency survival kit: An emergency survival kit is a box that contains

life-saving materials.

Introduction

We live in the environment. Different phenomena are happening in
the environment. Sunshine, rainfall, water cycle, wind, storm,
lightning, clouds, volcano, earthquake, soil erosion, forest fire etc. are
natural activities. Some of them are useful for us and some are harmful.

sunshine rainfall wind
fig: Natural activities

lightning volcano earthquake
fig: Natural disaster

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The natural activities that harm us are called natural disasters. Rainfall
is a natural activity. It is good for plants. It brings us water. However,
if it rains continuously for many days, it causes floods and landslides.
Therefore, heavy rainfall is a natural disaster.

Storm

The air in motion is called wind. The storm breaks the trees
wind is useful. If the wind is very
strong, it is called storm and it can
cause loss of lives and properties. It
destroys buildings. It can destroy crops.
Therefore, the storm is a natural disaster.

Resonable facts
Why should we stay inside our houses during the storm?
We should stay inside our houses during the storm
because a storm can kill people.

Flood

Water flows in the river. It is good for flood can cause loss of lives and
us. We get drinking water. Animals properties
live in it. However, the overflow of
water in the river is dangerous. The
overflow of water in the river is called
a flood. It is a disaster.

Fact file
Terai region of Nepal suffers a lot from floods.

Activity
Learn about flood cases in Nepal in the last 20 years
from the internet.

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Some harmful effects of the flood are listed below:
i. Human settlements are flooded.
ii. It destroys crops and kills domestic animals.
iii. People drown and die.
iv. Mud and sewage mix in drinking water.

Some of the causes of flood are given below:
i. When people cut trees, land becomes barren and cannot store

water. So all of water goes in the river.
ii. Heavy rainfall in the monsoon season.
iii. Meting of ice from mountains due to very hot weather.
iv. Bursting of lakes and dams.

deforestation concrete city bursting dam
fig: causes of flood

Some ways to prevent the flood are listed below
i. Reduce air pollution. Keep earth cool.
ii. Do not cut down trees. Plant trees in barren lands.
iii. Protect water resources.
iv. Make embankments on the riverside.
v. Build spurs in the river to decrease the speed of flood.
vi. Make canals and dams.
vii. Repair old dams.
viii. Plant trees on riverbank and hills.

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Some tips to be safe from the flood are:
i. Do not make huts on river banks.
ii. Make strong buildings.
iii. Use flood detection system.
iv. Government should inform people

about possible flood sthrough media.

flood detection system

Resonable facts
Why should we grow plants on the river banks?
We should grow plants on river banks because it
helps to control floods. It protects the soil.

Landslide

Nepal has lots of hills. Hills have weak soil. During the monsoon
season, masses of land fall down the hill. The falling of a landmass off
a hill is called a landslide. Landslide is a natural disaster. It is caused
by human activities as well.

landslide destroys lives and properties landslide can block roads

Some of the causes of landslides are listed below:
i. Weak hills
ii. Heavy rainfall

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iii. Earthquake

iv. Deforestation

v. Farming on sloped hills

vi. Mining

Resonable facts
Why are there frequent landslides in the hilly region of
Nepal during the monsoon?
There are frequent landslides in the hilly regions of Nepal
during the monsoon because of heavy rainfall on weak
hills for many days.
Effects of landslide:
i. Landslide destroys the forest.
ii. It destroys historical, cultural and religious places.
iii. It destroys villages and cities.
iv. It destroys roads, poles and hydroelectricity dams.
v. It kills people and livestock.
Some good tips to prevent landslides:
i. Plant trees on hills.
ii. Practise terrace farming on hills.
iii. Grow grasses along the edges of agriculture fields.
iv. Avoid overgrazing.
v. Do not make many houses on hills.
vi. Make proper gullies to drain the excess rainwater.

afforestation terrace farming on hills retaining walls
fig: preventive measures of landslide

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Activity
Make two models of hills: one with sloped land and
another with terrace. Pour down water from the top.
Which one will lose more soil? Observe.

Fact file
The hilly region of Nepal suffers a lot from landslides.

Some measures to be safe from the landslide are:
i. Make houses in safe places.
ii. If there are weak hills near our house, we should make retaining

walls.
iii. Be alert during heavy rainfall.
iv. Store emergency survival kit in our room.
v. Rescue buried people.

Fire

Fire is very useful for us. It is
used for cooking. It keeps us
warm in winter. If the fire is
mishandled it may cause a fire

disaster. house on fire
Causes of fire

i. Playing with matchstick and petroleum.

ii. Short circuit.

iii. Storm and lightning can cause a forest fire.

iv. Leakage of gas.

v. The explosion of bombs.

vi. Volcano.

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Effects of fire
i. Fire in the forest destroys plants.
ii. Wild animals will die.
iii. Fire in a house will kill people.
iv. Property will be destroyed.

Fact file
Flood and wildfire are natural disasters that occur mostly
on the earth.

Measures to prevent fire
i. Divide forest into many areas.
ii. Do not play with petroleum.
iii. Use electrical devices properly.

Resonable facts
Why should we keep flammable substances far away
from children’s reach?
We should keep flammable substances far away from
children’s reach because they may accidentally cause a
fire.

Things we should do during a fire are listed below
i. Call for help. Dial 101 to inform the fire brigade.
ii. Try to come outside the house.
iii. Do not touch things with bare hands. Use tools instead.
iv. If our clothes are burning we should cover ourself with a blanket

or use water. It will put out the fire.
v. Use water, mud or sand to put out the fire.
vi. Use first aid.

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Earthquake

We live on land. It does not move. Sometimes, however, it shakes.
The shaking of the land is called an earthquake. It is a natural disaster.
The earthquake is measured by seismograph.

Causes of earthquake
i. Volcanic eruption.

ii. Massive landslide.

iii. Movement of tectonic plates.

Effects of earthquake faulting causes earthquake
i. Earthquakes may cause cracks on

the ground.
ii. It may cause landslides and volcanoes.
iii. It may destroy buildings and roads.
iv. It may kill people.

earthquake destroys cities and villages

Fact file
Earthquakes usually occur on the edges of tectonic plates.

Resonable facts
Why should we not stay inside the house after a big
earthquake?
We should not stay inside our house after a big
earthquake because another earthquake may hit again
while the land is adjusting itself.

Safety measures from earthquake

Earthquakes cannot be prevented by human beings.

Some safety measures to save lives and property from an earthquake
are listed below:

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Before the earthquake
i. Make earthquake-proof buildings.
ii. Make strong roads and dams.
iii. Make houses in safe places.
iv. There should be open ground near every village.
v. Repair old and weak buildings.
vi. Do not keep heavy things in high places in the room.
viii. Store emergency survival kit in the room.

During the earthquake
i. Do not panic.We should be very careful while running outside

because we might fall, falling walls can hit us etc.
ii. If we are on the ground, we should sit down or lie on the ground.
iii. If we are inside a house, we should run toward an open space.
iv. If we are on top floors, we should go to the roof.
v. If we are driving, we must stop vehicles at a safe place.
vi. Hide under the table or wear a helmet to protect the head.

hiding under table during earthquake take shelter in open ground during the
earthquake

After the earthquake:
i. Call for help.
ii. Use first aid.
iii. Collect emergency survival kit.
iv. If we are not injured, we should help others.

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v. We should be very careful because aftershocks will occur
frequently after the main earthquake.

Resonable facts
Why should we not put heavy things at a height?
We should not keep heavy things at a height because
they can fall and hit us during the earthquake.

Emergency survival kit

An emergency survival kit is a box that an emergency survival kit
contains life-saving materials. It usually
contains food and water for a few days.
We can keep a first aid box in it. Torchlight,
whistle and power bank are also stored
in it. It is very important to save lives
during a natural disaster.

Activity
Make an emergency survival kit.

Summary

1. The natural activities that harm us are called natural disasters.
2. The overflow of water in the river is called a flood.
3. The government should alert people about possible flooding.
4. The falling of a landmass from a hill is called a landslide.
5. If a fire is mishandled it may cause a fire disaster.
6. If our clothes are burning we should cover ourself with a blanket

or use water. It will put out the fire.
7. The shaking of the land is called an earthquake.
8. Do not keep heavy things in high places in the room.

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9. An emergency survival kit is a box that contains lifesaving
materials.

10. Protect the head during earthquake. Hide under the table.

Model Questions with Their Answer

1. Write a cause of the flood.
Heavy rainfall is one of the main causes of floods.

2. Which device measures the earthquake?
A seismograph measures the earthquake.

3. What are the activities that help to reduce the chances of a
flood?

Some ways to reduce the chances of a flood are listed below:

i. Do not cut trees. Plant trees on barren lands.

ii. Build embankments on the riverside.

iii. Repair old dams.

iv. Plant trees on riverbanks and hills.

4. What should we do if our clothes catch fire?
We should do the following things if our clothes catch fire:

i. Throw the clothes away if possible.

ii. Put water if available.

iii. Cover with a thick cloth or blanket in case water is not

available.

iv. Use mud or sand to put out the fire.
5. What must be done during the earthquake?
We must do the following things during the earthquake:

i. Do not panic.

ii. If we are on the ground, we should sit on the ground or lie

down.

iii. If we are inside a house, we should run out to an open space.

iv. If we are driving, we must stop our vehicle at a safe place.

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Exercise

1. Fill in the blanks with an appropriate word.

storm seismograph natural emergency flood
disaster survival kit

a. The natural activities that harm us are called ………

b. A very strong wind is called ………

c. The overflow of water in the river is called ………..

d. Earthquake is measured by …………

e. Life-saving materials are present in …………

2. Write true for the correct and false for the incorrect statement.
a. Mud and sewage will mix in drinking water during the flood.
b. We have heavy rainfall in the monsoon season.
c. The falling of a landmass from a hill is called a storm.
d. The earthquake will crack the land.
e. The earthquake can be prevented by human beings.

3. Choose the best answer from the given alternatives.
a. What is the cause of the flood?

Heavy rainfall Tectonic plates Petroleum Weak hills
b. What is the cause of the landslide?

Petroleum Tectonic plates Heavy rainfall Short circuit

c. What is the cause of the fire?

Tectonic Heavy rainfall Petroleum Short circuit
plates

d. What measures the earthquake?

Seismograph Stethoscope Sphygmomanometer Barometer

e. What contains life-saving materials in it?

Emergency survival kit Lunch box Black box School bag

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4. Match the following. food and water for few days
Strong wind earthquake
Overflowing river flood
Shaking of land storm
Falling of land from hills landslide
Emergency survival kit

5. Answer the following questions in a word each.
a. Which disaster usually occurs in the hills during heavy
rainfall?
b. Which disaster usually occurs in Terai during heavy rainfall?
c. What device measures the magnitude of the earthquake?
d. What is the contact number of the fire brigade in Nepal?
e. What is stored in the room so that we can survive for a few
days during the disaster?

6. Write any two differences between:
a. Flood and landslide

7. Give reason.
a. We should plant trees on barren hills and riverbanks.
b. We should not make many houses on hills.
c. There are many landslides in the rainy season.
d. We should make earthquake-proof buildings.

8. Study the given diagram and answer the following questions.
i. Which natural disaster is shown?

ii. What are the possible causes of this
disaster?

iii. How can we prevent this disaster?

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9. Answer the following questions.
a. What is a natural disaster? Give two examples.
b. What are the causes of floods in the Terai region of Nepal?
c. What can be done to prevent floods in Terai?
d. What are the effects of flood?
e. What are the causes of landslides in the hills of Nepal?
f. What are the effects of landslides on people?
g. What should the government do to reduce the damage from
landslides?
h. What is an earthquake? Write any two of its causes.
i. How should people prepare for the earthquake?
j. What would you do if an earthquake hit you when you were
in the class?
k. What might be the possible causes of fire disaster? If our
home is on fire what should we probably do to be safe?

10. Project work.

What should you do to minimise the loss of life and property
after an earthquake?

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