28/FEBRUARY/2022 TO 05/MARCH/2022
REVISION
CHAPTER: 7 STATES OF MATTER
Whatever is present around us is known as matter. The table, chair, blackboard, chalk, duster, bags, air, water etc. can be called as matter.
• In other words we can see and feel matter by our senses.
• Matter is anything which occupies space, has weight and can be perceived by our senses.
A school bag containing books is a matter.
• Matter is just like a closed sac of grains.
• When it is opened, it gives you wheat grains which are like molecules.
• When we grind it, it gives you small flour particles which are like atoms.
States of Matter
Solid State
• If molecules are present close to each other, then it is solid state.
• Solids have a definite shape.
Liquid State
• If molecules are present away from each other, then it is liquid state.
• Liquids take the shape of the container.
Gaseous State
• If molecules are present very far away from each other, then it is gaseous state.
• Gases do not have any definite shape.
• When some solids are heated, they can change into a liquid or a gas.
• Some gases when cooled, change into liquids and solids.
21/FEBRUARY/2022 TO 26/FEBRUARY/2022
CHAPTER 12 : MEASUREMENT
We all make measurements in our daily life. Whether we are in a factory, shop or at home.
• Measurement is one of the most useful processes in science and in our daily life.
• It is done with the help of some standard value.
Whenever you want to get your dresses stitched, the tailor takes you measurement.
Unit
A unit is defined as a fixed quantity used as a standard of measurement.
Measurement of Length
In our day to day work, we use a scale to measure small lengths, e.g., a line drawn on a notebook.
When you go to the market to buy clothes with your mother, you ask for cloth in metres. The cloth merchant measures it with the help of a metre scale, e.g., 4 m of clothes (m = metres).
• For relatively bigger distances, we use kilometres as the unit.
Example : Distance between Jalandhar and Amritsar is 80 km (km =kilometres)
Measurement of Weight
When you buy fruits and vegetables, the shopkeeper measures the quantity. This is measurement of mass. Most of the things we purchase from market are measured by their quantity.
When a very small quantity of a substance has to be purchased, then we use grams. For example, when we go to buy gold, we ask for gold in grams. He uses a small physical balance to weigh this small piece of gold.
• Relatively larger quantities are measured in kilograms (kg).
Example : Whenever we buy fruits, vegetables, pulses, flour etc., we buy it in kilograms.
Measurement of Time
We all get up in the morning. You get ready and go to school. At what time should you get up? How long do you take to get ready? These questions are related to measurement of time.
The devices used to measure time are watch and clock.
• Smaller unit of time is second, larger is minute and the one still larger is hour
• Day, month and year are also considered as larger units of time.
1 hour = 60 minutes
1 minute = 60 seconds
Temperature is defined as the degree of hotness or coldness of a body.
We use thermometer to measure the temperature.
Our body temperature is measured by doctor or at home with the help of clinical thermometer.
Temperature of boiling water etc. is measured with the help of a laboratory thermometer.
14/FEBRUARY/2022 TO 19/FEBRUARY/2022
Revision
CHAPTER 11: SOUND AND NOISE
Sound is the sensation of hearing. It is produced when something vibrates.
When we speak our tongue vibrates and sound is produced.
We hear different sounds everyday. The chirping of birds, rattling of leaves and thunder are natural sounds. The ringing of door bell, blowing of horns and the sounds produced by machines are all artificial sounds.
Types of Sounds
In our daily lives we come across different types of sounds. Some are soft some are loud; some are pleasant and some are unpleasant. Some sounds are shrill and some are flat.
Sounds produced by living things :
Plants
• Plants produce sound by rattling of their leaves when air blows.
• When twigs, branches and fruits fall down from the leaves.
• When animals and birds make their way through the leaves and branches.
Animals
Animals make variable sounds. Few examples are buzzing of bees; chirping of birds ; hissing of snakes and mooing of cows.
TYPES OF SOUNDS
1. Soft and Loud
2. Pleasant and Unpleasant
3. Shrill and Flat
NOISE
Sound which is loud and unpleasant is called noise. Noise produce strong vibrations which can cause damage to our ear drums. Very loud sounds sometimes cause permanent deafness.
Steps to reduce noise pollution :
Following measures should be taken to reduce noise pollution :
1. We should not play the television, radio or music player at loud volumes.
2. Try to blow horns only when necessary.
3. Loud speakers should be avoided.
4. DJ should be used only for a limited period of time.
07/FEBRUARY/2022 to 12/FEBRUARY/2022
Revision
CHAPTER 10 : SAVE NATURAL RESOURCES
Natural resources are also called earth resources as they are obtained from various components of the earth. These resources are gifts of nature to mankind.
Examples : Water, air, minerals, oil, soil and sunlight.
Let us study these resources and find out effective measures to save it.
SOIL
Soil is the uppermost layer of earth’s crust. Soil is formed by the friction and breaking up of rocks.
Strong winds and river water carry and deposit it at different places.
Importance of Soil
Soil is an important natural resource because we grow grains, vegetables and other plants on it. It also provides shelter to a number of insects and animals.
Soil Erosion
The process of carrying away of soil by wind or water is called soil erosion.
Assignment:- Read and understand chapter-10.
03/FEBRUARY/2022
CHAPTER 9 : SEASONS AND ITS IMPACT
Revision
Effects of floods
• Floods damage the crops hence it destroys agriculture.
• Houses get washed away or either get submerged in water.
• Floods take away with them the top fertile layer of the soil and thus lead to soil erosion.
Measures against floods
• We can reduce floods by growing more trees. Trees bind the soil and increase its water retaining capacity.
• Building dams and embankments on the rivers will also help to prevent floods.
• Temporary dams can be constructed to stop or divert the flow of water from residential areas.
• The government and other agencies such as the Red Cross set up relief camps for the displaced people.
DROUGHT
What is a drought?
Drought is when a particular region falls dry for a long period of time.
What causes drought?
Drought conditions are caused when a region receives no rainfall or very less rainfall.
Effects of drought
• Drought results in desert like conditions and reduce water quality and quantity.
• People and livestock start dying because of shortage of food and water.
• Droughts lead to shortage of food and crops get destroyed because of absence of water.
• It leads to mass migration of people as people start moving to other areas in search of food and water.
• Droughts cause dust storms and give rise to soil erosion.
How can droughts be prevented?
1. Drought can be prevented by growing more trees as the roots have the capacity to hold water. Moreover, during transpiration trees gives out water vapours and help in giving moisture to the air to cause rain.
2. We should also develop means to harvest rainwater which can be used in case of droughts and hence we can reduce its harmful impact.
Assignment: Read and understand chapter-9.
01/FEBRUARY/2022
CHAPTER 9 : SEASONS AND ITS IMPACT
Revision
SUN - The Ultimate Source of Energy
1. Warmth : Sun gives warmth and protects the life from intense cold.
2. Light : Sun’s energy gives light and gives an environment to work.
3. Photosynthesis: Sun’s energy is used by plants to make their food by the process known as photosynthesis.
4. Solar cookers : Solar cookers are the devices which use solar energy for heating and cooking of food. The sun’s energy is trapped which heats up the solar cooker and cooks the food.
5. Drying : Sun’s energy is used to dry the clothes, fruits and certain vegetables.
6. Solar cell panel : Solar cells trap the solar energy and convert it into electrical energy. Solar cell panel is used specially in rural areas for street lightning.
Sometimes weather changes results in heavy rains leading to floods and sometimes results in no rains leading to drought. Both of these conditions lead to loss of life and property.
FLOODS
What are floods?
When the water does not seep through the soil and it collects over the land for several days, it is called a flood.
What causes floods?
In the interior areas, floods are caused due to continuous burst of rainfall or a cloud burst which makes the soil incapable of holding anymore water and thus the water enters the cities and submerges it.
1. Warmth : Sun gives warmth and protects the life from intense cold.
2. Light : Sun’s energy gives light and gives an environment to work.
3. Photosynthesis: Sun’s energy is used by plants to make their food by the process known as photosynthesis.
4. Solar cookers : Solar cookers are the devices which use solar energy for heating and cooking of food. The sun’s energy is trapped which heats up the solar cooker and cooks the food.
5. Drying : Sun’s energy is used to dry the clothes, fruits and certain vegetables.
6. Solar cell panel : Solar cells trap the solar energy and convert it into electrical energy. Solar cell panel is used specially in rural areas for street lightning.
Sometimes weather changes results in heavy rains leading to floods and sometimes results in no rains leading to drought. Both of these conditions lead to loss of life and property.
FLOODS
What are floods?
When the water does not seep through the soil and it collects over the land for several days, it is called a flood.
What causes floods?
In the interior areas, floods are caused due to continuous burst of rainfall or a cloud burst which makes the soil incapable of holding anymore water and thus the water enters the cities and submerges it.
Assignment: Read and understand chapter-9.
27/JANUARY/2022
Revision
CHAPTER 9 : SEASONS AND ITS IMPACT
SEASONS
During a particular season, the weather conditions remain same for a long period of time. This period is known as a season. There are five major seasons namely summer, winter, monsoon, spring and autumn.
Summer Season
Summer season is marked by hot weather. The scorching heat of sun makes it impossible to go out. People like to stay indoors. Most of the plants dry during this season; less flowers bloom due to intense heat. During summer, we wear light cotton clothes and drink a lot of water. Children enjoy cold drinks, juices and ice creams. People like to eat juicy fruits like melon, litchi and watermelon. Mango, the king of fruits is found in this season.
Rainy Season
Rainy season follows summer season. This season relieves us from the scorching heat of sun. Most of the plants look green and fresh in this season. The atmosphere looks more clean due to washing of atmospheric dust.
People need an umbrella or a raincoat to protect themselves from rain. Plants grow very fast in this season. In places where it rains a lot, people grow and eat rice because rice crop needs a lot of water. People like to take hot drinks and fried food.
Sometimes, heavy rains cause floods which cause damage to crops, houses and lives of people.
Autumn Season
Autumn season brings a lot of changes in weather. Strong winds and storms blow of dry leaves. The temperature becomes moderate. The dry leaves and dust blows in the form of storms. This season blow off old leaves and make place for new leaves to come.
Winter Season
It is the coldest month when the earth is away from the sun. During this month the earth receives slanting rays of sun due to which the temperature is less. It is the coldest time of year. The days are short and nights are cold. People wear heavy woolen clothes in winters. People drink hot milk, tea or soup to keep their body warm. In hilly areas, people light fire or use room heaters to keep themselves warm. Certain areas experience snow fall in this season.
Spring Season
Spring is marked by nature’s beauty. Flowers bloom on plants. Birds are heard twittering. New leaves are born on plants. Cool and pleasent winds blow. Days and nights are equal. People wear light clothes during spring.
Assignment: Read chapter:9.
25/JANUARY/2022
CHAPTER 9 : SEASONS AND ITS IMPACT
Revision
Axis : Axis of the earth is an imaginary line that runs through the centre of the earth. This axis is slightly tilted.
Poles : The two points where the axis seems to enter are called the poles.
Equator : The imaginary line that divides earth into two equal halves is called equator.
Northern hemisphere : The upper half is known as northern hemisphere.
Southern hemisphere : The lower half is known as southern hemisphere.
Movement of the Earth
Revolution : The earth moves around the sun. This movement of the earth is called revolution.
Rotation : The earth spins on its axis. This movement of the earth is called rotation.
Orbit : The revolution of earth takes place in a fixed path called orbit.
Solar year : Earth takes 365¼ days to complete one revolution. This time period is called a solar year.
Effect of Earth’s movement
Day and night
Rotation of the earth causes day and night. As the earth rotates, one half of it faces the sun. The part that faces the sun has day. The part that faces away from sun has night. It takes 24 hours for the earth to rotate once on its axis.
The earth’s axis is tilted at an angle. During winter season, the axis tilts away from the sun. On the other hand, it leans towards the sun in summer. As the earth revolves around the sun, some portions of the earth receive more heat from the sun. These portions have summer season. The other parts which are away from the sun get less heat. These areas experience winter season.
Earth is a blue planet where life exists. Its favourable conditions support life. It is positioned at right place, thus maintain an appropriate temperature for life to flourish.
Assignment: Read chapter: 9.
20/JANUARY/2022
CHAPTER 12: MEASUREMENT
Assignment:- Complete the following in your Science-OCB.
18/JANUARY/2022
CHAPTER 12: MEASUREMENT
Assignment:- Complete the following in your Science- OCB.
13/JANUARY/2022
CHAPTER 12: MEASUREMENT
Measurement of Weight
When you buy fruits and vegetables, the shopkeeper measures the quantity. This is measurement of mass. Most of the things we purchase from market are measured by their quantity.
When a very small quantity of a substance has to be purchased, then we use grams. For example, when we go to buy gold, we ask for gold in grams. He uses a small physical balance to weigh this small piece of gold.
• Relatively larger quantities are measured in kilograms (kg).
Example : Whenever we buy fruits, vegetables, pulses, flour etc., we buy it in kilograms.
Measurement of Time
We all get up in the morning. You get ready and go to school. At what time should you get up? How long do you take to get ready? These questions are related to measurement of time.
The devices used to measure time are watch and clock.
• Smaller unit of time is second, larger is minute and the one still larger is hour
• Day, month and year are also considered as larger units of time.
1 hour = 60 minutes
1 minute = 60 seconds
Temperature is defined as the degree of hotness or coldness of a body.
We use thermometer to measure the temperature.
Our body temperature is measured by doctor or at home with the help of clinical thermometer.
Temperature of boiling water etc. is measured with the help of a laboratory thermometer.
Assignment:- Read and understand chapter-12.
11/JANUARY/2022
CHAPTER 12: MEASUREMENT
Now watch this video for your better understanding:-
We all make measurements in our daily life. Whether we are in a factory, shop or at home.
• Measurement is one of the most useful processes in science and in our daily life.
• It is done with the help of some standard value.
Whenever you want to get your dresses stitched, the tailor takes you measurement.
Unit
A unit is defined as a fixed quantity used as a standard of measurement.
Measurement of Length
In our day to day work, we use a scale to measure small lengths, e.g., a line drawn on a notebook.
When you go to the market to buy clothes with your mother, you ask for cloth in metres. The cloth merchant measures it with the help of a metre scale, e.g., 4 m of clothes (m = metres).
• For relatively bigger distances, we use kilometres as the unit.
Example : Distance between Jalandhar and Amritsar is 80 km (km =kilometres)
Assignment:- Read and understand chapter-12.
09/DECEMBER/2021
REVISION
CHAPTER: 8 WATER
A. Tick the correct option:-
1. Which of the following is a pure form of water?
a) surface water b) rainwater
2. Which gas is used to disinfectant water?
a) chlorine b) bromine
3. Water which forms lather with soap easily is known as:
a) soft water b) rainwater
B. Fill in the blanks:-
1. ________ impurities are very finely mixed in water.
2. Lighter substances __________ in water.
3. _________ gas helps in the respiration.
C. Give one word for the following:-
1.Water which collects over the hard rock below the earth is called _________.
2. A cloth used for the process of filtration is _________.
D. True or false:-
1. Sugar dissolves completely in water.
2. The solid substance that dissolve is known as solute.
E. Answer the following questions:-
1. Differentiate between surface and underground water.
2. What is water cycle?
07/DECEMBER/2021
REVISION
CHAPTER 8 WATER
SOLUBILITY AND SOLUTION
Common Terms used in the formation of a Solution
IMPURITIES AND ITS REMOVAL
There are two types of impurities soluble and insoluble.
2. Sedimentation and Decantation
Removal of soluble impurities
Water is known as universal solvent because it can dissolve all kinds of solids, liquids or gases to little or more extent. According to the solubility, the substances may be classified as soluble or insoluble substances.
• The substances which dissolve rapidly in water are called soluble substances.
Examples : Common salt and sugar.
• The substances which dissolve very little or do not seem to dissolve are known as insoluble substances.
Examples : Mud and sand.
SOLUTION
The mixture formed by dissolving a soluble substance in water is known as solution.
Common Terms used in the formation of a Solution
1. Solvent : A liquid which dissolves other substances in it is called solvent. For example, common salt dissolves in water
and hence water is a solvent.
2. Solute : A substance which dissolves in a liquid is called solute. Example : In the above example common salt is the
solute.
3. Unsaturated Solution : A solution which has less amount of solute is known as unsaturated solution.
4. Saturated Solution : A solution which has large amount of solute is known as saturated solution.
Conditions which enhance the formation of a solution :
1. Solute and solvent must be capable of mixing.
2. High temperature enhances the formation of a solution.
3. Stirring helps in quick formation of the solution.
4. Solute should be in the form of a fine powder, as it helps in the formation of solution quickly.
IMPURITIES AND ITS REMOVAL
There are two types of impurities soluble and insoluble.
Both these impurities are present in water. Thus the removal of these impurities become important.
Some methods of removing insoluble impurities
1. Filtration The separation of insoluble impurities with the help of filter paper or muslin cloth is known as filtration.
Filtrate : The clear liquid which passes through the filter paper is known as filtrate.
Residue : The solid impurity left on the filter paper is known as residue.
2. Sedimentation and Decantation
The process of settling down of heavy impurities is known as sedimentation and then removing the clear liquid from the top is known as decantation.
Step I: The impure water is allowed to stand for sometime.
Step II: The impurities settle down at the bottom of the container as sediments.
Step III: The clean water poured out into a separate container is known as decantation.
Removal of soluble impurities
Soluble impurities are very finely mixed in water. Hence, their removal becomes bit difficult. These impurities can be removed by evaporation or by distillation.
Assignment:- Read and understand chapter-8.
02/DECEMBER/2021
REVISION
CHAPTER 8 WATER
Now watch these videos for your better understanding:-
Now watch these videos for your better understanding:-
POTABLE WATER
Need for Potable Water
PURIFICATION OF WATER
Water Purification at Small level
Chlorine Tablets
Hard and Soft Water
Water which is clean and pure and fit for human consumption is known as potable water.
Need for Potable Water
The water which is present in lakes, rivers and as underground water; can only be used for human consumption. Thus, there exist an intense need for potable water.
Characteristics of Drinking Water :
It should be :
(i) Colourless
(ii) Odourless
(iii) Free from suspended impurities
(iv) Free from bacteria and germs
(v) Free from harmful compounds
PURIFICATION OF WATER
The impure water has to undergo series of steps for the process of purification.
Step I : Pumping
Water from rivers, lakes is fed into pumping station where it is pumped into big reservoirs.
Step II : Sedimentation
Water is collected in reservoirs. Heavy particles settle down in this tank. Chemicals like alum are added to speed the process of sedimentation.
Step III : Filtration
After sedimentation, the water is filtered through a clean sandbed to remove the finer suspended particles.
Step IV : Chlorination
Water is then disinfected with a very small quantity of chlorine gas to kill bacteria.
Water Purification at Small level
The water brought to the houses may sometimes carry germs in the way. These germs may be removed by:
Boiling and Straining : Water may be boiled and then filtered with the help of a clean cloth.
Storage : The purified water should be stored in clean containers with a lid.
Chlorine Tablets
Chlorine tablets are used to kill the germs at the small level. It is simply added to drinking water, then kept for sometimes before consuming.
Hard and Soft Water
Soft Water : Water which forms lather with soap easily is known as soft water.
Example : Rainwater and distilled water.
Hard Water : Water which does not form lather with soap is known as hard water.
Example : Well water and spring water.
Water Contain Dissolved Gases
• Dissolved gases in water provide taste to the water.
• Oxygen dissolved in water helps in the respiration and survival of aquatic life.
• Carbon dioxide dissolved in water helps in photosynthesis of aquatic plants.
Assignment:- Read and understand chapter-8.
30/NOVEMBER/2021
REVISION
CHAPTER 8 WATER
Now watch this video for your better understanding:-
Water plays a key role in carrying out important activities like drinking, cooking, bathing, irrigation etc. Hence, life is possible on the earth due to the presence of water. Nearly three-fourth of the earth’s surface is covered with water. It is present in all living things.
OCCURRENCE OF WATER
Water is present almost in all natural things like plants, animals, rocks and air. In the solid state, it exists as snow in snow covered mountains. It is present in rocks and minerals as water of crystallisation and as water vapours in air.
Surface and underground water
Surface water : Water which is present on the surface of the earth is called surface water.
Example : Rainwater, sea water.
Underground water : The water which collects over the hard rock below the earth is called underground water.
Example : Well water, spring water.
WATER CYCLE
Circulation of water from the earth’s surface to the atmosphere and back to the earth is called the water cycle.
Assignment:- Read and understand chapter-8.
25/NOVEMBER/2021
REVISION
CHAPTER : 7 STATES OF MATTER
23/NOVEMBER/2021
REVISION
CHAPTER : 7 STATES OF MATTER
Now watch this video for your better understanding:-
Whatever is present around us is known as matter. The table, chair, blackboard, chalk, duster, bags, air, water etc. can be called as matter.
• In other words we can see and feel matter by our senses.
• Matter is anything which occupies space, has weight and can be perceived by our senses.
A school bag containing books is a matter.
Composition of Matter
• Matter is just like a closed sac of grains.
• When it is opened, it gives you wheat grains which are like molecules.
• When we grind it, it gives you small flour particles which are like atoms.
States of Matter
Solid State
• If molecules are present close to each other, then it is solid state.
• Solids have a definite shape.
Liquid State
• If molecules are present away from each other, then it is liquid state.
• Liquids take the shape of the container.
Gaseous State
• If molecules are present very far away from each other, then it is gaseous state.
• Gases do not have any definite shape.
Can states of matter be changed?
• When some solids are heated, they can change into a liquid or a gas.
• Some gases when cooled, change into liquids and solids.
Assignment:- Read and understand chapter-7.
18/NOVEMBER/2021
CHAPTER 11 : SOUND AND NOISE
Assignment:- Complete the following in your Science-OCB.
16/NOVEMBER/2021
CHAPTER 11: SOUND AND NOISE
Now watch this video for your better understanding:-
Sounds produced by living things:
Plants
• Plants produce sound by rattling of their leaves when air blows.
• When twigs, branches and fruits fall down from the leaves.
• When animals and birds make their way through the leaves and branches.
Animals
Animals make variable sounds. Few examples are buzzing of bees; chirping of birds ; hissing of snakes and mooing of cows.
TYPES OF SOUNDS
1. Soft and Loud
2. Pleasant and Unpleasant
3. Shrill and Flat
NOISE
Sound which is loud and unpleasant is called noise. Noise produce strong vibrations which can cause damage to our ear drums. Very loud sounds sometimes cause permanent deafness.
Steps to reduce noise pollution :
Following measures should be taken to reduce noise pollution :
1. We should not play the television, radio or music player at loud volumes.
2. Try to blow horns only when necessary.
3. Loud speakers should be avoided.
4. DJ should be used only for a limited period of time.
Assignment:- Read and understand Chapter-11.
02/NOVEMBER/2021
CHAPTER 11 : SOUND AND NOISE
Now watch this video for your better understanding:-
Sound is the sensation of hearing. It is produced when something vibrates.
When we speak our tongue vibrates and sound is produced.
We hear different sounds everyday. The chirping of birds, rattling of leaves and thunder are natural sounds. The ringing of door bell, blowing of horns and the sounds produced by machines are all artificial sounds.
Types of Sounds
In our daily lives we come across different types of sounds. Some are soft some are loud; some are pleasant and some are unpleasant. Some sounds are shrill and some are flat.
Assignment:- Read and understand chapter- 11.
Holiday Homework:- Learn notes of chapter- 7, 8 and 9.
28/OCTOBER/2021
CHAPTER 10 : SAVE NATURAL RESOURCES
Assignment:- Complete the following in your Science-OCB.
26/OCTOBER/2021
CHAPTER 10 : SAVE NATURAL RESOURCES
Now watch this video for your better understanding:-
Natural resources are also called earth resources as they are obtained from various components of the earth. These resources are gifts of nature to mankind.
Examples : Water, air, minerals, oil, soil and sunlight.
Let us study these resources and find out effective measures to save it.
SOIL
Soil is the uppermost layer of earth’s crust. Soil is formed by the friction and breaking up of rocks.
Strong winds and river water carry and deposit it at different places.
Importance of Soil
Soil is an important natural resource because we grow grains, vegetables and other plants on it. It also provides shelter to a number of insects and animals.
Soil Erosion
The process of carrying away of soil by wind or water is called soil erosion.
How to save soil?
Roots of the trees fix the soil particles to ground and hence check erosion. Therefore, more and more trees should be planted to check soil erosion.
WATER
Nearly 75% of the land is covered with water which is present on the earth in the form of various bodies like ponds, lakes, rivers, seas and oceans. It is also present as underground water.
Importance of water
• We need water to drink, bathe, wash,cook and clean.
• We also need water to irrigate our crops.
Water Pollution
The process by which water gets contaminated with solid waste, debris, and other harmful substances is called water pollution.
How to save water?
Basic saving of water starts at home.
• Close tap when not in use.
• Do not leave the tap open while brushing.
• Do not throw any kind of waste into stagnant water.
• Rainwater can be collected in containers and used.
AIR
Air is a mixture of gases. It is present in the lower layer of atmosphere. Moving air is called wind and it possesses a lot of energy.
Importance of Air
• All living things breathe in air for their survival.
• Green plants take in carbon dioxide present in the air to prepare their food.
• Animals take in oxygen for respiration.
• Wind is used to run mills for generating energy.
Air Pollution
The process by which the clean air gets contaminated with other gases, dust and chemicals is called air pollution.
How to Save Air from Being Polluted?
• Unnecessary burning should be decreased.
• Tall chimneys should be present on factories.
• More and more trees should be planted.
• Using pollution free vehicles.
FOSSIL FUELS
The remains of plants and animals which were buried deep under the earth got converted into fossil fuels. These fuels contain a lot of energy. Some of the fossil fuels are coal, charcoal, petrol, diesel etc.
Importance of Fossil Fuels
We use fossil fuels mainly to generate energy. This energy can be used for doing any sort of work. Different fuels are used for different purposes.
1. Coal : To run the steam engine.
2. Petrol : To run various vehicles.
3. Kerosene : To fill in lamps and stoves.
4. LPG : Used for cooking.
How To Save Fuel?
• Cooking on a slow flame saves fuel
• Vehicles should be kept in proper conditions as old and damaged vehicles consume more fuel.
• Food cooked in covered vessel employs less fuel.
• Avoid heating the food again and again.
Assignment:- Read chapter- 10.
21/OCTOBER/2021
CHAPTER 9 : SEASONS AND ITS IMPACT
07/OCTOBER/2021
CHAPTER 9 : SEASONS AND ITS IMPACT
Now watch these videos for your better understanding:-
SUN - The Ultimate Source of Energy
1. Warmth : Sun gives warmth and protects the life from intense cold.
2. Light : Sun’s energy gives light and gives an environment to work.
3. Photosynthesis: Sun’s energy is used by plants to make their food by the process known as photosynthesis.
4. Solar cookers : Solar cookers are the devices which use solar energy for heating and cooking of food. The sun’s energy is trapped which heats up the solar cooker and cooks the food.
5. Drying : Sun’s energy is used to dry the clothes, fruits and certain vegetables.
6. Solar cell panel : Solar cells trap the solar energy and convert it into electrical energy. Solar cell panel is used specially in rural areas for street lightning.
Sometimes weather changes results in heavy rains leading to floods and sometimes results in no rains leading to drought. Both of these conditions lead to loss of life and property.
FLOODS
What are floods?
When the water does not seep through the soil and it collects over the land for several days, it is called a flood.
What causes floods?
In the interior areas, floods are caused due to continuous burst of rainfall or a cloud burst which makes the soil incapable of holding anymore water and thus the water enters the cities and submerges it.
Effects of floods
• Floods damage the crops hence it destroys agriculture.
• Houses get washed away or either get submerged in water.
• Floods take away with them the top fertile layer of the soil and thus lead to soil erosion.
Measures against floods
• We can reduce floods by growing more trees. Trees bind the soil and increase its water retaining capacity.
• Building dams and embankments on the rivers will also help to prevent floods.
• Temporary dams can be constructed to stop or divert the flow of water from residential areas.
• The government and other agencies such as the Red Cross set up relief camps for the displaced people.
DROUGHT
What is a drought?
Drought is when a particular region falls dry for a long period of time.
What causes drought?
Drought conditions are caused when a region receives no rainfall or very less rainfall.
Effects of drought
• Drought results in desert like conditions and reduce water quality and quantity.
• People and livestock start dying because of shortage of food and water.
• Droughts lead to shortage of food and crops get destroyed because of absence of water.
• It leads to mass migration of people as people start moving to other areas in search of food and water.
• Droughts cause dust storms and give rise to soil erosion.
How can droughts be prevented?
1. Drought can be prevented by growing more trees as the roots have the capacity to hold water. Moreover, during transpiration trees gives out water vapours and help in giving moisture to the air to cause rain.
2. We should also develop means to harvest rainwater which can be used in case of droughts and hence we can reduce its harmful impact.
Assignment:- Read chapter-9 carefully.
05/OCTOBER/2021
CHAPTER 9 : SEASONS AND ITS IMPACT
Now watch this video for your better understanding:-
THE EARTH
Earth is a blue planet where life exists. Its favourable conditions support life. It is positioned at right place, thus maintain an appropriate temperature for life to flourish.
Axis : Axis of the earth is an imaginary line that runs through the centre of the earth. This axis is slightly tilted.
Poles : The two points where the axis seems to enter are called the poles.
Equator : The imaginary line that divides earth into two equal halves is called equator.
Northern hemisphere : The upper half is known as northern hemisphere.
Southern hemisphere : The lower half is known as southern hemisphere.
Movement of the Earth
Revolution : The earth moves around the sun. This movement of the earth is called revolution.
Rotation : The earth spins on its axis. This movement of the earth is called rotation.
Orbit : The revolution of earth takes place in a fixed path called orbit.
Solar year : Earth takes 365¼ days to complete one revolution. This time period is called a solar year.
Effect of Earth’s movement
Day and night
Rotation of the earth causes day and night. As the earth rotates, one half of it faces the sun. The part that faces the sun has day. The part that faces away from sun has night. It takes 24 hours for the earth to rotate once on its axis.
The earth’s axis is tilted at an angle. During winter season, the axis tilts away from the sun. On the other hand, it leans towards the sun in summer. As the earth revolves around the sun, some portions of the earth receive more heat from the sun. These portions have summer season. The other parts which are away from the sun get less heat. These areas experience winter season.
SEASONS
During a particular season, the weather conditions remain same for a long period of time. This period is known as a season. There are five major seasons namely summer, winter, monsoon, spring and autumn.
Summer Season
Summer season is marked by hot weather. The scorching heat of sun makes it impossible to go out. People like to stay indoors. Most of the plants dry during this season; less flowers bloom due to intense heat. During summer, we wear light cotton clothes and drink a lot of water. Children enjoy cold drinks, juices and ice creams. People like to eat juicy fruits like melon, litchi and watermelon. Mango, the king of fruits is found in this season.
Rainy Season
Rainy season follows summer season. This season relieves us from the scorching heat of sun. Most of the plants look green and fresh in this season. The atmosphere looks more clean due to washing of atmospheric dust.
People need an umbrella or a raincoat to protect themselves from rain. Plants grow very fast in this season. In places where it rains a lot, people grow and eat rice because rice crop needs a lot of water. People like to take hot drinks and fried food.
Sometimes, heavy rains cause floods which cause damage to crops, houses and lives of people.
Autumn Season
Autumn season brings a lot of changes in weather. Strong winds and storms blow of dry leaves. The temperature becomes moderate. The dry leaves and dust blows in the form of storms. This season blow off old leaves and make place for new leaves to come.
Winter Season
It is the coldest month when the earth is away from the sun. During this month the earth receives slanting rays of sun due to which the temperature is less. It is the coldest time of year. The days are short and nights are cold. People wear heavy woolen clothes in winters. People drink hot milk, tea or soup to keep their body warm. In hilly areas, people light fire or use room heaters to keep themselves warm. Certain areas experience snow fall in this season.
Spring Season
Spring is marked by nature’s beauty. Flowers bloom on plants. Birds are heard twittering. New leaves are born on plants. Cool and pleasent winds blow. Days and nights are equal. People wear light clothes during spring.
Earth is a blue planet where life exists. Its favourable conditions support life. It is positioned at right place, thus maintain an appropriate temperature for life to flourish.
Axis : Axis of the earth is an imaginary line that runs through the centre of the earth. This axis is slightly tilted.
Poles : The two points where the axis seems to enter are called the poles.
Equator : The imaginary line that divides earth into two equal halves is called equator.
Northern hemisphere : The upper half is known as northern hemisphere.
Southern hemisphere : The lower half is known as southern hemisphere.
Movement of the Earth
Revolution : The earth moves around the sun. This movement of the earth is called revolution.
Rotation : The earth spins on its axis. This movement of the earth is called rotation.
Orbit : The revolution of earth takes place in a fixed path called orbit.
Solar year : Earth takes 365¼ days to complete one revolution. This time period is called a solar year.
Effect of Earth’s movement
Day and night
Rotation of the earth causes day and night. As the earth rotates, one half of it faces the sun. The part that faces the sun has day. The part that faces away from sun has night. It takes 24 hours for the earth to rotate once on its axis.
The earth’s axis is tilted at an angle. During winter season, the axis tilts away from the sun. On the other hand, it leans towards the sun in summer. As the earth revolves around the sun, some portions of the earth receive more heat from the sun. These portions have summer season. The other parts which are away from the sun get less heat. These areas experience winter season.
SEASONS
During a particular season, the weather conditions remain same for a long period of time. This period is known as a season. There are five major seasons namely summer, winter, monsoon, spring and autumn.
Summer Season
Summer season is marked by hot weather. The scorching heat of sun makes it impossible to go out. People like to stay indoors. Most of the plants dry during this season; less flowers bloom due to intense heat. During summer, we wear light cotton clothes and drink a lot of water. Children enjoy cold drinks, juices and ice creams. People like to eat juicy fruits like melon, litchi and watermelon. Mango, the king of fruits is found in this season.
Rainy Season
Rainy season follows summer season. This season relieves us from the scorching heat of sun. Most of the plants look green and fresh in this season. The atmosphere looks more clean due to washing of atmospheric dust.
People need an umbrella or a raincoat to protect themselves from rain. Plants grow very fast in this season. In places where it rains a lot, people grow and eat rice because rice crop needs a lot of water. People like to take hot drinks and fried food.
Sometimes, heavy rains cause floods which cause damage to crops, houses and lives of people.
Autumn Season
Autumn season brings a lot of changes in weather. Strong winds and storms blow of dry leaves. The temperature becomes moderate. The dry leaves and dust blows in the form of storms. This season blow off old leaves and make place for new leaves to come.
Winter Season
It is the coldest month when the earth is away from the sun. During this month the earth receives slanting rays of sun due to which the temperature is less. It is the coldest time of year. The days are short and nights are cold. People wear heavy woolen clothes in winters. People drink hot milk, tea or soup to keep their body warm. In hilly areas, people light fire or use room heaters to keep themselves warm. Certain areas experience snow fall in this season.
Spring Season
Spring is marked by nature’s beauty. Flowers bloom on plants. Birds are heard twittering. New leaves are born on plants. Cool and pleasent winds blow. Days and nights are equal. People wear light clothes during spring.
Assignment:- Read chapter -9.
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