02 / 02 / 2022, 07 / 02 / 2022
Ch.11. Force, Work and Energy
Revision Continued
ENERGY
Energy is the ability to do work. We get energy from food we eat. This energy gets stored in our body and helps us to do work.
Principle of Energy Conservation
Energy can neither be created nor be destroyed but it can be converted from one form to the other.
Main Source of Energy
Sun is the main source of energy on earth. Sun’s energy is taken by green plants to prepare their food. The green plants are eaten by herbivores and energy gets transferred to their body. Herbivores are further eaten by carnivores and the energy is further transferred to carnivores.
DIFFERENT FORMS OF ENERGY
1. Mechanical energy
The energy possessed by a body due to its state of rest or of motion is known as mechanical energy.
Kinetic energy
The energy possessed by a body by virtue of its motion is known as kinetic energy.
Example : The water flowing in a river possess kinetic energy.
Potential energy
The energy possessed by a body by virtue of its state of rest is known as potential energy.
Example : A stone lying at a height possess potential energy.
2. Chemical energy
It is the energy stored in the molecules of some chemicals.
Example: Matchstick, wood and coal.
3. Heat energy
The energy possessed by a body at higher temperature is known as heat energy.
4. Light energy
The energy which helps us to see is known as light energy.
5. Sound energy
The energy which is produced by a vibrating body is known as sound energy.
6. Electrical energy
The energy which is used to run electrical appliances is known as electrical energy.
7. Magnetic energy
The energy possessed by a magnet is known as magnetic energy.
8. Muscular energy
The energy stored in the muscles of our body is called muscular energy.
Renewable and Non-Renewable Sources of Energy
ASSIGNMENT
Answer the following questions:-
Q.1. State the principle of energy conservation.
Q.2. Write the SI unit of :
(a) Work
(b) Force
Q.3. Define mechanical energy.
Q.4. What is potential energy?
19 / 01 / 2022, 24 / 01 / 2022, 31 / 01 / 2022
Ch.11. Force, Work and Energy
Revision
The push or pull on an object is known as force. An engine can make a car move from rest. The force of brakes can slow down or stop a moving car due to friction.
Unit of Force
In the SI system, the unit of force is called Newton (N). The unit is named after a great scientist, Sir Issac Newton.
Force produces motion
How and when do we make use of force?
Therefore, the object always moves in the direction of the applied force (that is, in the direction of pull or push).
EFFECTS OF FORCE
1. Force causes motion in a stationary body.
If a force is applied on a stationary body, it can make the body move. Sometimes, the force is insufficient to make the body move.
2. Force can stop a moving body.
If a force is applied on a moving body, it can stop the movement of the body.
3. Force can produce a change in speed.
A force applied on moving object can increase the speed of object.
A force applied in opposite direction on moving object can decrease the speed of object.
4. Force can change the direction of motion of a body.
5. Force can produce a change in the shape of a body.
The applied force can change the shape of the object.
Forces are mainly of two types:
(i) Contact Forces
(ii) Non-Contact Forces
(i) Contact Forces : The forces which act when two bodies touch each other are known as contact forces. Example : Frictional force.
(ii) Non-Contact Forces : The forces which act when two bodies do not touch each other are known as non-contact forces.
Example : Magnetic force.
Resultant Force
The total force acting on a body is called net force or resultant force.
If the force is acting in one direction, then the resultant force is sum of all the forces.
WORK
Work means to do anything using energy. The amount of work done by a body is directly proportional to the amount of energy possessed by a body.
What is Work?
Work is said to be done when an applied force moves the body through some distance.
Work = Force × Distance
Unit of Work
Work done is measured in Joules (J).
Conditions for Work to be done :
For work to be done, two conditions should be fulfilled.
- A force should be applied on the body.
- The force applied should move the body.
MENTAL, PHYSICAL AND MECHANICAL WORK
When you learn your lesson, mental work is said to be done.
When the work is done with the help of a machine, mechanical work is said to be done.
When you throw a ball upwards, the work is done against the force of gravity. After sometime the ball comes back to the ground. It is said to be in direction of gravity.
ENERGY
ASSIGNMENT
Energy is the ability to do work. We get energy from food we eat. This energy gets stored in our body and helps us to do work.
Principle of Energy Conservation
Energy can neither be created nor be destroyed but it can be converted from one form to the other.
Main Source of Energy
Sun is the main source of energy on earth. Sun’s energy is taken by green plants to prepare their food. The green plants are eaten by herbivores and energy gets transferred to their body. Herbivores are further eaten by carnivores and the energy is further transferred to carnivores.
DIFFERENT FORMS OF ENERGY
1. Mechanical energy
The energy possessed by a body due to its state of rest or of motion is known as mechanical energy.
Kinetic energy
The energy possessed by a body by virtue of its motion is known as kinetic energy.
Example : The water flowing in a river possess kinetic energy.
Potential energy
The energy possessed by a body by virtue of its state of rest is known as potential energy.
Example : A stone lying at a height possess potential energy.
2. Chemical energy
It is the energy stored in the molecules of some chemicals.
Example: Matchstick, wood and coal.
3. Heat energy
The energy possessed by a body at higher temperature is known as heat energy.
4. Light energy
The energy which helps us to see is known as light energy.
5. Sound energy
The energy which is produced by a vibrating body is known as sound energy.
6. Electrical energy
The energy which is used to run electrical appliances is known as electrical energy.
7. Magnetic energy
The energy possessed by a magnet is known as magnetic energy.
8. Muscular energy
The energy stored in the muscles of our body is called muscular energy.
Renewable and Non-Renewable Sources of Energy
Answer the following :-
Q.1. What things can a force do?
Q.2. How to find the work done by the force?
Q.3.What is meant by work done by constant force?
Q.4. What is Energy, and how does it relate to work?
Q.5. What is the unit of measurement for energy?
10 / 01 / 2022, 12 / 01 / 2022 , 17 / 01 / 2022
Ch. 10. LIGHT AND SHADOW
REVISION
Light is a form of energy. Light is needed to see thins around us. We are able to see the beautiful world around us just because of light. Sun is the main or ultimate source of light. The part of the Earth that receives sunlight has day and the part of the Earth that do not get sunlight has night.
Features of light :
1. Light produces sensation of vision.
2. Light travels in straight line.
3. Light can be reflected as well as refracted.
4. Reflected light helps us to see.
5. Light travels at a very-very high speed.
Transparent
The objects which allow light to pass through it are known as transparent objects.
Example : Ordinary glass.
Translucent
The objects which allow partial amount of light to pass through it are known as translucent objects.
Example : Butter paper.
Opaque
The objects which do not allow light to pass through it are known as opaque objects.
Example : Wood, concrete wall.
FORMATION OF SHADOWS
You might have seen the shadow of a tree or shadow of your own on the ground in sunlight. It appears like a dark patch on the ground.
Formation of Shadows
When an opaque object is placed in the path of light. The path of light is obstructed and a dark patch is formed on the ground. This dark patch is called the shadow of the opaque object. Shadow is always formed on the opposite side to that of light.
The dark patch obtained when an object obstructs the path of light is known as shadow.
ECLIPSE
What is an Eclipse?
An eclipse occurs when one object in space blocks an observer from seeing another object in space. Since we are on earth, so we can have two types of obstructions, one in which sun is not visible or eclipsed (Solar eclipse) and the other in which moon is eclipsed not visible (Lunar eclipse).
SOLAR ECLIPSE
We know that moon revolves around the earth. Sometimes during its revolution it comes in between the sun and the earth causing a shadow to fall on certain portions on earth. The sun gets blocked for the observers falling under this shadowed region. The eclipse is not seen from every place on earth but only from these locations. For them it becomes dark even during the day time. This is known as Solar Eclipse.
LUNAR ECLIPSE
Lunar eclipse occurs when the earth comes between the sun and the moon during its revolution. When this happen, the moon does not receive light from the sun and earth’s shadow falls on the moon due to which the moon disappears or appears to be darkened.
ASSIGNMENT
Q.1. Give three features of light.
Q.2. How does presence of sun makes life possible on Earth?
Q.3. What is reflection?
Q.4. Why solar eclipse should not be seen with naked eyes?
22 / 12 / 2021
Ch.12. Simple Machines
Continuation.....
INCLINED PLANE
An inclined plane is a simple sloping surface which is used to push up objects instead of lifting them up. The ramp outside our houses is a perfect example of an inclined plane. Imagine how your father would have managed to bring the car inside your home if that ramp was not there. Would it be possible?
Hospitals are provided with a ramp to easily carry the wheelchairs up or down which is impossible via stairs.
from the truck.
Wedge
Wedge is a simple machine which works on the principle of an inclined plane. It has 2 inclined surfaces put together to have a sharp cutting edge.
For example: Knife, a needle, an axe which we see around us in our daily life are all wedges. The sharp ‘V’ formed due to joining of two inclined planes is used
to force things apart.
Screw
Screw has been derived from an inclined plane. It is like a nail with grooves cut in it. The grooves provided on the screw hold things tightly together which is why a screw is always better than the nail.
PULLEY
A pulley is a simple machine which is used to lift heavy loads very easily. It changes the direction of force and hence makes it easy to lift heavy loads. It is difficult to lift because it is against the force of gravity. It is easy to drop because it works in the direction of force of gravity.
Diagrammatic Representation of a Pulley :
A simple fixed pulley consists of a wheel with a groove and having a rope wound around it.
In the figure B, load is to
.
+ lifted in upward direction and effort i.e., rope is pulled in the downward direction. Therefore, by changing the direction of force it becomes easier to lift a bucket of water.
Pulleys are also used in cranes to lift loads.
Pulleys are also used in cranes to lift loads.
The Wheel and Axle
Can you imagine a car without wheels or your bicycle without wheels?
The wheel and axle is a simple machine in which a wheel is attached to a cylindrical rod called axle or the wheel rolls upon the axle.
MAINTENANCE AND CARE OF MACHINES
To make these machines work for a longer time we should keep in mind the following points:
1. Since most of the parts are made of iron, therefore, they must be painted against rusting.
2. Machines should be lubricated because there takes place a lot of wear and tear due to frictional forces.
3. Machines should be kept covered when not in use.
ASSIGNMENT
Answer the following questions:
1. How does a pulley ease our work?
2. Why do machines require proper care and maintenance?
3. What is a lever and define 3rd class of lever?
06 / 12 / 2021, 08 / 12 / 2021
Ch.08 Molecules and their Arrangement
REVISION
In our daily life, we come across a wide variety of things. All these things are materials. Some of these things are living and some are non-living. Living things include plants and animals, whereas non-living things include table, chair, pencil, pen etc.
ATOMS AND MOLECULES
Matter is made of tiny particles called atoms. Some atoms are very stable. They are not reactive, hence they stay alone. Example gold, platinum and carbon. But there are certain atoms that are very active and do not stay alone. Such atoms combine with other atoms of the same or different kinds to form a molecule.
Atom: The smallest particle of matter is known as atom.
Example: Gold, silver.
Molecule: Atoms of the same or different kind join together to form molecules.
Example: Oxygen, water.
Now watch this introduction video...
MOLECULES AND THEIR ARRANGEMENT
There are three states of matter namely solid, liquid and gas. Let us study about the molecules and their arrangement.
Solids
Properties of Solid:
- Molecules are closely packed in solids.
- Solids have high density.
- They have definite volume.
Examples:
Liquids
Properties of Liquid:- Molecules are loosely packed in liquids.
- Liquids have medium density
- Liquids also have definite volume.
Examples:
Gas
Properties of Gas:- Molecules are very loosely packed.
- Gases do not have fixed shape. They also take the shape of container.
- Gases do not have a definite volume.
- Gases have low density.
Examples:
There are three states of matter. Few substances like water can exist in more than one state. These states are brought about by application of heat.
Water exists in liquid state in ponds, wells, seas and ocean. When we heat water, it starts boiling and changes into gaseous state known as water vapours.
When we cool water it changes to solid state known as ice.
Freezing: The process in which liquid changes to solid on cooling is known as freezing
Example: Water to ice.
Example: Ice to water.
Evaporation: The process in which substance changes to vapours at normal temperature is known as evaporation.
Example: Water to water vapours.
• Boiling: The process in which substance is heated to a very high temperature so that it changes into vapours is known as boiling.
Example : Water to water vapours.
Note: The boiling point of water is 100°C.
• Condensation: The process in which liquid droplets are formed from vapours is known as condensation.
Example: Water vapours to water droplets.
Assignment
Complete the given Worksheet.
24 / 11 / 2021, 29 / 11 / 2021, 01 / 12 / 2021
CH.12. SIMPLE MACHINES
Machines Everywhere!
Do you know machines are used by us in almost every activity we perform? We use a machine to cut fruits, we use a machine to draw water from well, we use a machine to open a cold drink bottle. Even the pen which we use for writing is a machine.
Now, since you know them, let us know what machines are and why do we call them machines?
A machine is a device that makes our work faster and easier. We either change the force applied or the direction of applied force.
Example : A pair of scissors.
Imagine cutting a plastic sheet with your hands. Is it possible? While cutting the same sheet with scissors is easier and quicker.
TYPES OF MACHINES
Simple Machines : The equipments that are designed in such a way that makes our work easy are known as simple machines. A knife is so designed that its one side is made very sharp so that it can cut easily.
Example; knife, scissors, hand pump, pulley.
Complex Machines : It is a combination of two or more simple machines and has a number of parts.
There are 3 types of simple machines:
A lever is a rigid rod which is free to move about a fixed point.
The fixed point is called Fulcrurum. The force which is applied is Effort and the object to be lifted is Load.
In this class, the fulcrum (F) lies in between the load (L) and the effort (E).
In this class, Load (L) lies in between Fulcrum (F) and Effort (E).
In this type, Effort (E) lies in between the Fulcrum (F) and the Load (L).
An inclined plane is a simple sloping surface which is used to push up objects instead of lifting them up. The ramp outside our houses is a perfect example of an inclined plane. Imagine how your father would have managed to bring the car inside your home if that ramp was not there. Would it be possible?
Hospitals are provided with a ramp to easily carry the wheelchairs up or down which is impossible via stairs.
Wedge is a simple machine which works on the principle of an inclined plane. It has 2 inclined surfaces put together to have a sharp cutting edge.
For example: Knife, a needle, an axe which we see around us in our daily life are all wedges. The sharp ‘V’ formed due to joining of two inclined planes is used
to force things apart.
Screw
Screw has been derived from an inclined plane. It is like a nail with grooves cut in it. The grooves provided on the screw hold things tightly together which is why a screw is always better than the nail.
Screw has been derived from an inclined plane. It is like a nail with grooves cut in it. The grooves provided on the screw hold things tightly together which is why a screw is always better than the nail.
A pulley is a simple machine which is used to lift heavy loads very easily. It changes the direction of force and hence makes it easy to lift heavy loads. It is difficult to lift because it is against the force of gravity. It is easy to drop because it works in the direction of force of gravity.
A simple fixed pulley consists of a wheel with a groove and having a rope wound around it.
In the figure B, load is to lifted in upward direction and effort i.e., rope is pulled in the downward direction. Therefore, by changing the direction of force it becomes easier to lift a bucket of water.
Pulleys are also used in cranes to lift loads.
Can you imagine a car without wheels or your bicycle without wheels?
The wheel and axle is a simple machine in which a wheel is attached to a cylindrical rod called axle or the wheel rolls upon the axle.
To make these machines work for a longer time we should keep in mind the following points:
1. Since most of the parts are made of iron, therefore, they must be painted against rusting.
2. Machines should be lubricated because there takes place a lot of wear and tear due to frictional forces.
3. Machines should be kept covered when not in use.
ASSIGNMENT
Complete it
Q.1. Why do machines require proper care and maintenance?
Q.2. What is lever and define 3rd class of lever?
Q.3. Draw the diagrammatic representation of second class of lever, giving three examples each along with it.
17 / 11 / 2021, 22 / 11 / 2021
Ch.11 Force, Work and Energy
CONTINUED
Resultant Force
The total force acting on a body is called net force or resultant force.
If the force is acting in one direction, then the resultant force is sum of all the forces.
Moves the body through some distance.
Work = Force × Distance
Unit of Work
Work done is measured in Joules (J).
WORK
Work means to do anything using energy. The amount of work done by a body is directly proportional to the amount of energy possessed by a body.
Work is said to be done when an applied force m
Conditions for Work to be done :
For work to be done, two conditions should be fulfilled.- A force should be applied on the body.
- The force applied should move the body.
MENTAL, PHYSICAL AND MECHANICAL WORK
When you learn your lesson, mental work is said to be done.
When you learn your lesson, mental work is said to be done.
WORK DONE AGAINST AND IN THE DIRECTION OF GRAVITY
ENERGY
Energy is the ability to do work. We get energy from food we eat. This energy gets stored in our body and helps us to do work.
Energy is the ability to do work. We get energy from food we eat. This energy gets stored in our body and helps us to do work.
Principle of Energy Conservation
Energy can neither be created nor be destroyed but it can be converted from one form to the other.
Energy can neither be created nor be destroyed but it can be converted from one form to the other.
Main Source of Energy
Sun is the main source of energy on earth. Sun’s energy is taken by green plants to prepare their food. The green plants are eaten by herbivores and energy gets transferred to their body. Herbivores are further eaten by carnivores and the energy is further transferred to carnivores.
Sun is the main source of energy on earth. Sun’s energy is taken by green plants to prepare their food. The green plants are eaten by herbivores and energy gets transferred to their body. Herbivores are further eaten by carnivores and the energy is further transferred to carnivores.
DIFFERENT FORMS OF ENERGY
The energy possessed by a body due to its state of rest or of motion is known as mechanical energy.
The energy possessed by a body by virtue of its motion is known as kinetic energy.
Example : The water flowing in a river possess kinetic energy.
The energy possessed by a body by virtue of its state of rest is known as potential energy.
Example : A stone lying at a height possess potential energy.
It is the energy stored in the molecules of some chemicals.
Example: Matchstick, wood and coal.
The energy possessed by a body at higher temperature is known as heat energy.
The energy which helps us to see is known as light energy.
The energy which is produced by a vibrating body is known as sound energy.
The energy which is used to run electrical appliances is known as electrical energy.
The energy possessed by a magnet is known as magnetic energy.
The energy stored in the muscles of our body is called muscular energy.
Renewable and Non-Renewable Sources of Energy
ASSIGNMENT
Complete it
Q.1. Calculate the work done when force of 80 N moves the object by 16 metres.
Q.2. Explain ''Sun is ultimate source of all energy".
27 / 10 / 2021, 01 / 11 / 2021, 03 / 11 / 2021
CH.11. FORCE
The push or pull on an object is known as force. An engine can make a car move from rest. The force of brakes can slow down or stop a moving car due to friction.
Unit of Force
In the SI system, the unit of force is called Newton (N). The unit is named after a great scientist, Sir Issac Newton.
Force produces motion
How and when do we make use of force?
Therefore, the object always moves in the direction of the applied force (that is, in the direction of pull or push).
EFFECTS OF FORCE
1. Force causes motion in a stationary body.
If a force is applied on a stationary body, it can make the body move. Sometimes, the force is insufficient to make the body move.
2. Force can stop a moving body.
If a force is applied on a moving body, it can stop the movement of the body.
3. Force can produce a change in speed.
A force applied on moving object can increase the speed of object.
A force applied in opposite direction on moving object can decrease the speed of object.
4. Force can change the direction of motion of a body.
5. Force can produce a change in the shape of a body.
The applied force can change the shape of the object.
TYPES OF FORCE
Forces are mainly of two types:(i) Contact Forces
(ii) Non-Contact Forces
(i) Contact Forces : The forces which act when two bodies touch each other are known as contact forces.
Example : Frictional force.
Example : Magnetic force.
Resultant Force
The total force acting on a body is called net force or resultant force.
If the force is acting in one direction, then the resultant force is sum of all the forces.
The total force acting on a body is called net force or resultant force.
If the force is acting in one direction, then the resultant force is sum of all the forces.
WORK
Work means to do anything using energy. The amount of work done by a body is directly proportional to the amount of energy possessed by a body.
What is Work?
Work is said to be done when an applied force moves the body through some distance.
Work = Force × Distance
Work is said to be done when an applied force moves the body through some distance.
Work = Force × Distance
Unit of Work
Work done is measured in Joules (J).
Conditions for Work to be done :
For work to be done, two conditions should be fulfilled.- A force should be applied on the body.
- The force applied should move the body.
MENTAL, PHYSICAL AND MECHANICAL WORK
When you learn your lesson, mental work is said to be done.
When you push an object and the object moves, physical work is said to be done.
When the work is done with the help of a machine, mechanical work is said to be done.
WORK DONE AGAINST AND IN THE DIRECTION OF GRAVITY
ENERGY
Energy is the ability to do work. We get energy from food we eat. This energy gets stored in our body and helps us to do work.
Principle of Energy Conservation
Energy can neither be created nor be destroyed but it can be converted from one form to the other.
Main Source of Energy
Sun is the main source of energy on earth. Sun’s energy is taken by green plants to prepare their food. The green plants are eaten by herbivores and energy gets transferred to their body. Herbivores are further eaten by carnivores and the energy is further transferred to carnivores.
DIFFERENT FORMS OF ENERGY
The energy possessed by a body due to its state of rest or of motion is known as mechanical energy.
The energy possessed by a body by virtue of its motion is known as kinetic energy.
Example : The water flowing in a river possess kinetic energy.
The energy possessed by a body by virtue of its state of rest is known as potential energy.
Example : A stone lying at a height possess potential energy.
It is the energy stored in the molecules of some chemicals.
Example: Matchstick, wood and coal.
The energy possessed by a body at higher temperature is known as heat energy.
The energy which helps us to see is known as light energy.
The energy which is produced by a vibrating body is known as sound energy.
The energy which is used to run electrical appliances is known as electrical energy.
7. Magnetic energy
The energy possessed by a magnet is known as magnetic energy.
The energy possessed by a magnet is known as magnetic energy.
The energy stored in the muscles of our body is called muscular energy.
Renewable and Non-Renewable Sources of Energy
ASSIGNMENT
Complete it
1. A person pushing the wall does not work. Why?
2. A thunderstorm sometimes results in cracking of window panes. Why?
18 / 10 / 2021, 20 / 10 / 2021, 25 / 10 / 2021
Ch. 10. LIGHT
Light is a form of energy. Light is needed to see things around us. We are able to see the beautiful world around us just because of light. Sun is the main or ultimate source of light. The part of the Earth that receives sunlight has day and the part of the Earth that do not get sunlight has night.
Features of light:
1. Light produces sensation of vision.
2. Light travels in straight line.
3. Light can be reflected as well as refracted.
4. Reflected light helps us to see.
5. Light travels at a very-very high speed.
We can see a plant during day time because it reflects sunlight, which then enters our eyes and helps us to see.
The objects which allow light to pass through it are known as transparent objects.
Example : Ordinary glass.
Translucent
The objects which allow partial amount of light to pass through it are known as translucent objects.
Example : Butter paper.
Opaque
The objects which do not allow light to pass through it are known as opaque objects.
Example : Wood, concrete wall.
FORMATION OF SHADOWS
You might have seen the shadow of a tree or shadow of your own on the ground in sunlight. It appears like a dark patch on the ground.
Formation of Shadows
When an opaque object is placed in the path of light. The path of light is obstructed and a dark patch is formed on the ground. This dark patch is called the shadow of the opaque object. Shadow is always formed on the opposite side to that of light.
The dark patch obtained when an object obstructs the path of light is known as shadow.
ECLIPSE
What is an Eclipse?
An eclipse occurs when one object in space blocks an observer from seeing another object in space. Since we are on earth, so we can have two types of obstructions, one in which sun is not visible or eclipsed (Solar eclipse) and the other in which moon is eclipsed not visible (Lunar eclipse).
We know that moon revolves around the earth. Sometimes during its revolution it comes in between the sun and the earth causing a shadow to fall on certain portions on earth. The sun gets blocked for the observers falling under this shadowed region. The eclipse is not seen from every place on earth but only from these locations. For them it becomes dark even during the day time. This is known as Solar Eclipse.
LUNAR ECLIPSE
Lunar eclipse occurs when the earth comes between the sun and the moon during its revolution. When this happen, the moon does not receive light from the sun and earth’s shadow falls on the moon due to which the moon disappears or appears to be darkened.
04 / 10 / 2021, 06 / 10 / 2021
The topmost layer of Earth’s crust is soil. Soil is very important for life on Earth. Soil holds the plants firmly and helps in their growth. Plants in turn produce food and maintain oxygen cycle in nature.
FORMATION OF SOIL
Soil is formed by weathering of rocks. The mechanical agents like heat, water, wind etc., break rocks into smaller and smaller pieces. The fine powder obtained by breaking of rocks is known as soil. The soil so obtained is not so fertile and does not support plant growth. The soil has to be enriched with :
(i) Organic matter which includes :
(a) dead plants and animals.
(b) waste of living plants and animals.
(ii) Minerals.
Thus, we can say, “A complex mixture of fine powder obtained by weathering of rocks, organic matter and minerals is known as soil.”
Layers of Soil
There are three main layers of soil:
(i) Topsoil : The top layer of soil is rich in organic matter, dark in colour and suitable for growth of plants.
(ii) Subsoil: The layer below the top layer is light in colour and full of broken rock pieces. This is known as sub soil.
(iii) Bed rock: The bottom layer is made-up of solid rock called bed rock.
Functions of Soil Soil are needed:
(ii) for construction of buildings.
(iii) for making toys, pots and decorative articles.
Introduction to soil formation
Soil is home for many animals
Many microscopic organisms like bacteria live in the soil. Insects like ants, grasshoppers, centipedes, millipedes, scorpions, earthworm etc. are also found in the soil. Bigger animals like rats, moles and rabbits also make their homes in the soil. They dig burrows or holes in the soil to live in. They break up the hard parts of the soil and help in making soil soft for easy growth of plants.
TYPES OF SOIL
Broadly classifying soil is of four types. Different places have different kinds of soil.
SOIL EROSION
The process of removal of fertile topsoil by the action of wind and water is called soil erosion.
Due to the action of external forces like wind, water etc., the topsoil being soft and light is removed. This creates an imbalance in nature and both plant as well as animal life is disturbed.
Factors affecting soil erosion :
1. Heavy rains and floods cause soil to flow along with water.
2. Strong winds and cyclones cause top soil to blow away.
3. Cutting of trees cause soil to loosen and carries the soil along.
SOIL CONSERVATION
Topsoil contains most minerals, hence it is best suitable for the growth of plants. Measures have to be taken to prevent soil from erosion otherwise the fertile top soil will be lost. “The protection of the soil form erosion by adopting suitable measures is known as soil conservation.”
Methods to Conserve Soil
1. By growing grass and trees : The roots of grass and trees bind the soil firmly. As a result, it cannot be blown off easily by eroding agents like water, wind etc.
2. By constructing dams and embankments : Embankments are walls of rocks and stones on the bank of river. Dams and embankments help in controlling floods and hence are useful in checking soil erosion.
3. By terrace farming : When water comes down from a hilly area, it exerts great force on the soil. If the flow of water is made slower, the damage can be reduced. Thus, slopes are cut into terraces and farming on these terraces prevents soil erosion.
4. By practising crop rotation : If same type of crop is grown it will deplete same type of nutrients. The soil will not be able to recover the mineral loss and hence will lead to soil erosion. Thus, different crops should be grown on fields every time so that soil has time to recover the minerals that the previous crop has used. This is called crop rotation.
ASSIGNMENT
Q.1. Write five methods of soil conservation.
Q.1. Write five methods of soil conservation.
15 / 09 / 2021
Continuation of chapter -08 Molecules and their Arrangements
CHANGE IN STATE OF MATTER
There are three states of matter. Few substances like water can exist in more than one state. These states are brought about by application of heat.
Water exists in liquid state in ponds, wells, seas and ocean. When we heat water, it starts boiling and changes into gaseous state known as water vapours.
When we cool water it changes to solid state known as ice.
Some other terms related to change in state.
Freezing: The process in which liquid changes to solid on cooling is known as freezing
Example: Water to ice.
Melting: The process in which solid changes to liquid on heating is known as melting.
Example: Ice to water.
Evaporation:
The process in which substance changes to vapours at normal temperature is known as evaporation.
Example: Water to water vapours.
• Boiling: The process in which substance is heated to a very high temperature so that it changes into vapours is known as boiling.
Example : Water to water vapours.
Note: The boiling point of water is 100°C.
• Condensation: The process in which liquid droplets are formed from vapours is known as condensation.
Example: Water vapours to water droplets.
ASSIGNMENT
Q. 1. Make a table chart of symbol of elements atomic no. 1 to 20.
06/09/2021, 08/09/2021, 13/09/2021
Ch.08 Molecules and their Arrangements
In our daily life, we come across a wide variety of things. All these things are materials. Some of these things are living and some are non-living. Living things include plants and animals, whereas non-living things include table, chair, pencil, pen etc.
ATOMS AND MOLECULES
Matter is made of tiny particles called atoms. Some atoms are very stable. They are not reactive, hence they stay alone. Example gold, platinum and carbon. But there are certain atoms that are very active and do not stay alone. Such atoms combine with other atoms of the same or different kinds to form a molecule.
Atom: The smallest particle of matter is known as atom.
Example: Gold, silver.
Molecule: Atoms of the same or different kind join together to form molecules.
Example: Oxygen, water.Now watch this introduction video...
MOLECULES AND THEIR ARRANGEMENT
There are three states of matter namely solid, liquid and gas. Let us study about the molecules and their arrangement.
Solids
Properties of Solid:
- Molecules are closely packed in solids.
- Solids have high density.
- They have definite volume.
Examples:
Liquids
Properties of Liquid:- Molecules are loosely packed in liquids.
- Liquids do not have fixed shape. They take the shape of container.
- Liquids have medium density- Liquids also have definite volume.
Examples:
Properties of Gas:
- Molecules are very loosely packed.
- Gases do not have fixed shape. They also take the shape of container.
- Gases do not have a definite volume.- Gases have low density.
Examples:
There are three states of matter. Few substances like water can exist in more than one state. These states are brought about by application of heat.
Water exists in liquid state in ponds, wells, seas and ocean. When we heat water, it starts boiling and changes into gaseous state known as water vapours.
When we cool water it changes to solid state known as ice.
Some other terms related to change in state.
Freezing: The process in which liquid changes to solid on cooling is known as freezing
Example: Water to ice.
Freezing: The process in which liquid changes to solid on cooling is known as freezing
Example: Water to ice.
Example: Ice to water.
Evaporation:
The process in which substance changes to vapours at normal temperature is known as evaporation.
Example: Water to water vapours.
• Boiling: The process in which substance is heated to a very high temperature so that it changes into vapours is known as boiling.
Example : Water to water vapours.Note: The boiling point of water is 100°C.
• Condensation: The process in which liquid droplets are formed from vapours is known as condensation.
Example: Water vapours to water droplets.Assignment
Q.1. Write five point differences between solids, liquids and gases.
23/08/2021, 25/08/2021, 01/09/2021
CH. 07 STATES OF MATTER
CONTINUATION
What is matter?
Anything that occupies space and has mass is called matter. Matter can range from something as small as a needle to something as big as an aeroplane. So everything we see is called matter. Infact we can’t see air but since air has mass and occupies space, it is also called matter.
Properties of matter
- It occupies space.
- It has mass.
- It can be perceived by the senses. (either seen or felt)
STATES OF MATTER
Matter exists in three different states
The best example to understand the states of matter is by taking water. Take a glass of water. It is in liquid state. When we put water in an ice tray and keep it in a freezer for some time, it becomes ice i.e., solid. If we put the same glass of water in a pan and heat it, it becomes gas (steam).
Let us study about the important properties of solids, liquids and gases.
Solids
- In solids the molecules are closely packed and there are no intermolecular spaces between them.
- Solids have fixed shape and don’t flow.
- Solids occupy a definite volume and cannot be compressed.
- In solids the molecules are strongly attracted towards each other and hence they are dense.
Examples
Liquid
- In liquids the molecules are loosely packed and there are few intermolecular spaces between them.
- Liquids do not have a fixed shape and take the shape of any container. Also, liquids can flow easily.
- Liquids have an indefinite shape but definite volume and can be compressed slightly.
- In liquids molecules are not attracted towards each other with so strong forces as in solids. Hence, they are less dense.
Examples
Gases
- In gases the molecules are very loosely packed and there are huge intermolecular spaces between them.
- Gases do not have any shape of their own and take the shape of the container they are put in. Also, gases can flow easily.
- Gases don’t have a definite volume and can be compressed easily.
- In gases, molecules are very weakly attracted towards each other. Hence, they are very less dense.
Examples
CLASSIFICATION OF MATTER
On the basis of nature of atoms present in it. These are of three types.
Interconversion of States of Matter
Matter can be converted from one state to another by simple processes like freezing, boiling, melting etc.
For example, water can be converted to gaseous form by boiling and ice can be converted to water by melting.
Change of State
When matter is converted from one state to the other it is called change of state. Let us understand the various processes that take place during change of state.
Sublimation
The process in which a solid gets converted to gaseous form is called Sublimation.
e.g., Camphor, naphthalene.
Assignment
Q.1. Collect different kinds of matter from your surroundings and make a chart after classifying into solids,liquids and gases.
11/08/2021
CH. 07 STATES OF MATTER
What is matter?
Anything that occupies space and has mass is called matter. Matter can range from something as small as a needle to something as big as an aeroplane. So everything we see is called matter. Infact we can’t see air but since air has mass and occupies space, it is also called matter.
Properties of matter
- It occupies space.
- It has mass.
- It can be perceived by the senses. (either seen or felt)
STATES OF MATTER
Matter exists in three different states
The best example to understand the states of matter is by taking water. Take a glass of water. It is in liquid state. When we put water in an ice tray and keep it in a freezer for some time, it becomes ice i.e., solid. If we put the same glass of water in a pan and heat it, it becomes gas (steam).
Let us study about the important properties of solids, liquids and gases.
Solids
- In solids the molecules are closely packed and there are no intermolecular spaces between them.
- Solids have fixed shape and don’t flow.
- Solids occupy a definite volume and cannot be compressed.
- In solids the molecules are strongly attracted towards each other and hence they are dense.
Examples
Liquid
- In liquids the molecules are loosely packed and there are few intermolecular spaces between them.
- Liquids do not have a fixed shape and take the shape of any container. Also, liquids can flow easily.
- Liquids have an indefinite shape but definite volume and can be compressed slightly.
- In liquids molecules are not attracted towards each other with so strong forces as in solids. Hence, they are less dense.
Examples
Gases
- In gases the molecules are very loosely packed and there are huge intermolecular spaces between them.
- Gases do not have any shape of their own and take the shape of the container they are put in. Also, gases can flow easily.
- Gases don’t have a definite volume and can be compressed easily.
- In gases, molecules are very weakly attracted towards each other. Hence, they are very less dense.
Examples
CLASSIFICATION OF MATTER
On the basis of nature of atoms present in it. These are of three types.
Interconversion of States of Matter
Matter can be converted from one state to another by simple processes like freezing, boiling, melting etc.
For example, water can be converted to gaseous form by boiling and ice can be converted to water by melting.
Change of State
When matter is converted from one state to the other it is called change of state. Let us understand the various processes that take place during change of state.
Sublimation
The process in which a solid gets converted to gaseous form is called Sublimation.
e.g., Camphor, naphthalene.
Assignment
Q.1. Collect different kinds of matter from your surroundings and make a chart after classifying into solids,liquids and gases.
02/08/2021, 04/08/2021, 09/08/2021
Ch. 06 Vegetative Propagation
There are many plants which neither bear flower nor fruit. Some plants reproduce through other parts. Thus, new plants can grow not only from seeds or spores but also grow from other parts such as stems, leaves and roots. This phenomenon is known as vegetative propagation.
VEGETATIVE PROPAGATION
Vegetative propagation is the process in which new plants grow from stem, leaves and roots instead of seeds.
Stem
Two common underground stems, potato and onion reproduce vegetatively.
Potato, an underground stem has buds called eyes which give rise to new plants.
Onion, an underground stem has leaves which if planted can grow into a new plant.
The stem of a sugarcane has root-like structures which can also grow into a new plant.
Leaves
Some leaves like bryophyllum have bud-like structures. These grow into a new plant when they get favourable conditions.
Roots
Carrot and sweet potato can grow into new plants from their roots.
Carrot and sweet potato can grow into new plants from their roots.
Spores
Some plants like fern and fungi do not bear flowers. They produce their spores, each of which grows into a new plant.
Some plants like fern and fungi do not bear flowers. They produce their spores, each of which grows into a new plant.
THE FLOWER
Flowers are the most attractive and colourful part of the plant. The main parts of a flower are :
1. Pedicel : The flower is borne on a stalk called pedicel.
2. Sepals : The outermost whorl of a flower consists of leaf like structures called sepals. These are generally green in colour. It protects the inner floral whorls during the bud formation and also takes part in photosynthesis.
3. Petals : Petals are brightly coloured with sweet smell that attract the insects.
4. Stamen : It is the male part of a flower. It consists of a thin stalk called filament and a bilobed structure called anther. Each anther contains pollen grains.
5. Carpel : It is the female part of the flower. It is divided into three parts stigma, style and ovary.
A flower in which all the four whorls i.e., sepal, petal, stamen and carpel are present is known as a complete flower.
Example : China rose and mustard. Incomplete Flower
A flower in which one or more whorls is missing is called an incomplete flower.
Example : Date palm and mulberry tree.
Functions of Flowers:
1. Many flowers produce sweet, sticky substance called nectar.
2. Many flowers like rose and jasmine produce perfume.
3. Spices are the dried flower buds.
4. Flowers help in the process of reproduction. Pollination
The process of transfer of pollen grains from anther to stigma is called pollination.
After the pollination, fertilization takes place leading to the formation of fruit and seeds.
(i) Ovary develops to form the fruit.
(ii) Ovules present in the ovary form the seeds.
(i) Ovary develops to form the fruit.
(ii) Ovules present in the ovary form the seeds.
Now watch this video...
Assignment
Draw the typical structure of a flower and write the name of their parts.
19/07/2021, 26/07/2021, 28/07/2021
CH. 05 GROWTH AND REPRODUCTIONS IN PLANTS
Watch this introduction video.....
Plants are important for every living creature. They are the God’s greatest blessing to us. Plants give us food. Fibres, rubber, gum, tea, cereals, fruits, vegetables and spices are also provided by plants. Oxygen which is needed by all organisms is also given out by plants.
Growing plants from seeds
When you eat papaya or a watermelon, you will find seeds inside. New plants can be grown from these seeds as these seeds contain a growing embryo.
Types of Seed
Germination of Seeds
During the early stages of germination, the seedling gets food for its growth from the seed leaves. After the seed leaves are used up, the baby plant obtains its nourishment from the nutrients present in the soil.
Stages of germination: The entire span from the seed to a plant is referred as stages of germination.
1. Seeds absorb water from the soil.
2. Seed gets air and light, seed coat breaks and the seedling comes out.
3. The seedling develops root (or radicle) which grows downwards and shoot (or plumule) which grows upwards.
4. Cotyledons shrink and disappear. The seedling develops into a young plant.
5. Young plant takes time and grows to maximum.
Conditions required for Germination
Conditions for germination include air, water and warmth. Thus, in order to understand the conditions of germination, let us carry out the following activity:
Watch this video now....
Dispersal of Seeds
The process by which seeds are scattered away from the parent plant is called “Dispersal of seeds''.
Agents of dispersal
Dispersal of seeds is carried out by wind, water, explosion or even by animals. These are known as agents of dispersal. Now, let us study how the different agents cause dispersal.
(a) Dispersal by wind
Plants which have light weight seeds or have hairy or winged seeds are dispersed by wind. e.g., Dandelion, Maple, Sycamore.
(b) Dispersal by water
Seeds of plants growing in and around water bodies are dispersed by water. They have a fibrous or spongy structure which helps water to transport these seeds from one place to another. e.g., coconut, lotus.
(c) Dispersal by animals
Some seeds are eaten and thrown away by animals. These seeds grow into new plants. Some seeds pass out along with undigested waste. In some cases, seeds have hooks, stiff hair or spines which cling to animal bodies. When animals move the seeds are also carried away.
(d) Dispersal by explosion
In some plants, the seeds open and burst on drying. They scatter in all directions. This is known as explosion, e.g., pea, poppy, beans.
Different plant parts used for reproduction are tabulated below :
Watch this video now...
Agriculture and crops
Agriculture is the practice of growing crops on a large scale.
The plants grown on a large scale for food or other purposes are known as crops.
Steps involved in agriculture
Agriculture is a stepwise process.
The different stages in agriculture are given below :
1. Ploughing : The field is ploughed. Ploughing is the practice of loosening the soil using a plough before seeds are sown. It helps to increase air circulation in the soil.
2. Adding fertilizers : Manure and fertilizers are added to the soil. These are essential for the growth of the plant.
3. Sowing : Good quality seeds are sown with sufficient space in between them to prevent overcrowding of plants.
4. Irrigation : The seeds are watered. Proper amount of water should be provided.
5. Protection of crops : Crops are sprayed with pesticides, insecticides, weedicides to protect them.
6. Harvesting : Crops are cut and gathered once they are ripe. This is known as harvesting.
Watch this video now...
Types of Crops
Depending on the season in which crops are grown, they are of two types :
The table below gives the differences between Kharif and Rabi crops :
Watch this video now....
Increasing yield of crops
The yield of crops can be increased in the following ways :
- Using good quality seeds for sowing.
- Irrigating the soil properly.
- Keeping the soil well-aereated.
- Protecting the crops against grazing animals, pests, diseases.
Assignment
Q. Collect different kinds of seeds and make a seed chart by classifying them into rabi and kharif crops.
07/07/2021, 12/07/2021, 14/07/2021
CH.04 SAFETY AND FIRST AID
Imagine a person driving a scooter at very high speed and talking on mobile phone while he drives. He suddenly hits into a pedestrian as he crosses the road. The pedestrian gets serious injuries while the person driving the scooter breaks his leg. Suppose you are an eye witness to this accident. What will you do to provide the first help to both of them? Whose mistake or negligence was it? What precautions should have been followed that would have saved this accident?
Before we learn to answer the above question, let us find out what is an accident?
Can accidents be prevented?
Yes, accidents can be prevented by being careful and cautious and following the safety rules at various places. Children should always follow what their parents and teachers ask them to do to avoid accidents.
Let us now learn about some safety rules to be followed at different places to avoid accidents.
ROAD SAFETY
Road accidents are caused due to rash driving. People drive at high speeds and don’t follow the traffic rules.
Let’s read what traffic rules should be followed on road.
Rules that should be followed while driving
- Follow traffic rules everywhere.
- Have knowledge about the sign boards used on roads and follow them.
- Never exceed the speed limit while driving.
- Always fasten the seat belt while driving.
- Always use an indicator to change the lane.
- On a two wheeler both the riders should wear a helmet.
- Always use an indicator to change the lane.
- On a two wheeler both the riders should wear a helmet.
- Overtaking should always be done from the right.
- Always look into a rear view mirror before overtaking.- Never drive after drinking.
- Children should not be given scooter or cars for driving before the age of 18.
- Always be careful while crossing an unmanned railway crossing.
- Children should not be given scooter or cars for driving before the age of 18.
- Always be careful while crossing an unmanned railway crossing.
Rules to be followed by pedestrians.
• Always use a footpath to walk on the road.
• Always cross the road from the pedestrian or zebra crossing.
• Look carefully, first towards your right and then left before crossing the road.
• Always make small children walk towards your left while walking on the road.
• Do not let children run or play on the road.
• Try not to use the mobile phone even while walking.
FIRE SAFETY
Safety in case of fire is very essential because a single spark may lead to a big and harmful fire accident. Fire accidents are generally caused by electric sparks, smoking, leakage of cooking gas or petrol, fire crackers etc. Rules that should be followed for fire safety.
Safety in case of fire is very essential because a single spark may lead to a big and harmful fire accident. Fire accidents are generally caused by electric sparks, smoking, leakage of cooking gas or petrol, fire crackers etc. Rules that should be followed for fire safety.
- Never touch an electric switch with wet hands.
- Always wear rubber slippers while dealing with electrical appliances or wires. This is because rubber is a bad conductor of electricity.
- In case of fire caused by electricity never throw water over it because water is a good conductor of electricity and may conduct the electricity to your body andyou may get shock.
- Electric fire should be put off with the help of sand. For big fires, fire extinguisher can be used.
- Cooking gas supply should be closed at night after use. In case of leakage of cooking gas, all doors and windows should be opened to let the gas escape. Never light a candle or switch on or off any electrical appliance as any spark generated may ignite a fire and lead to bigger fire.
- If possible cooking gas cylinders should be kept in the open and the supply pipe should be changed regularly.- Always wear cotton clothes while cooking. Never wear nylon clothes because they catch fire easily.
- Fire caused due to petrol should always be put out by throwing sand or fire extinguisher.
This is because petrol is lighter than water and hence floats on water and continues to get air supply. The fire doesn’t get extinguished.
- Fire crackers should be burnt by maintaining proper distance and being very careful.
In case somebody’s clothes catches fire, cover him with a blanket or make him roll on the ground. This will cut the air supply and put off fire.
More is the contact with air, more the fire will spread.
- Inflammable items should be kept out of the reach of small children.
- In case of huge fire accidents, fire extinguishing team or fire brigade should be called immediately.
FIRST AID
What do you do when a friend of yours falls and gets injured? Do you directly rush him to the doctor or first give some help on your own? This immediate help given to a wounded person before the doctor arrives is called First Aid. It relieves the injured person from some pain and prevents the injury from getting worse.
Injury
- The victim should not be surrounded by too many people and should be given mental calm.
- Next step is to give immediate medical help.
- The type of help to be given depends on the type of injury.
Cuts and wounds expose the internal tissues to the air that contains germs and dust. This may cause infection if proper care is not taken.
- Always clean the wound with an antiseptic solution like dettol that kills germs and then apply some antiseptic cream.
- Don’t let flies sit on the wound.
• In case of bleeding:
- Use an ice pack (crushed ice in a thick towel) to stop bleeding.
- Tie a tight band above the wound for stopping the
blood flow.
Nose Bleeding
- Make the person sit down and squeeze the nostrils with thumb and index finger. Breath through mouth.
Burns
When the skin gets exposed to high temperature, the outer layer of the skin gets removed and exposes the inner sensitive layers to germs and dust.
- In case of a burn, immediately wash the burnt part with cold water.
- Apply an antiseptic like burnol to the wound.
- If antiseptic is not available use a mixture of baking soda and water to the burnt area.
- Never prick the blisters that arise after burns as it exposes the inner sensitive tissues to germs.
When the skin gets exposed to high temperature, the outer layer of the skin gets removed and exposes the inner sensitive layers to germs and dust.
- In case of a burn, immediately wash the burnt part with cold water.
- Apply an antiseptic like burnol to the wound.
- If antiseptic is not available use a mixture of baking soda and water to the burnt area.
Sprains and Fractures
Animal Bite
Animal bite is very dangerous as the bites of various insects and animals is poisonous and can even cause death if they enter the body.
Dog Bite
- Wash the wound with water and antiseptic as the saliva of dogs contain harmful germs, which can cause rabies.
- Apply an antiseptic.
- Immediately visit the doctor.
Insect Bite
- In case of a honeybee or wasp bite, remove the sting using a tweezer. This removes the sting and prevents it from spreading.
- Wash the bitten area with soap. Soap neutralises the sting or the chemical released by the insect bite.
Snake Bite
- First step should be to stop the poison from spreading to the entire body as snake poison directly affects the nervous system and leads to death.
- For this a tight bandage (tourniquet) is tied a little above the bitten area to stop the blood from circulating in that area and spread of poison can be prevented.
- Do not let the victim sleep.
- Take the victim to the doctor immediately.
First Aid for Poisoning
- Poisoning can be caused by taking in certain substances that are very harmful and dangerous like phenyl, naphthalene balls, nail polish etc.
- In case someone has swallowed a poison, we should try to induce vomiting by making the victim drink lot of lukewarm, salty water. This way the poisonous substance swallowed can be thrown out of the body. The victim should then be rushed to the doctor immediately.
Assignment
Q. Prepare a first aid box at home and write their five applications in your OCBs.
05/07/2021
CH.03 NERVOUS SYSTEM AND SENSE ORGANS
CONTINUED
REFLEX ACTIONS
On touching a hot object, you pull back your hand immediately. The secretion of saliva in your mouth on seeing a pizza for dinner, the blinking of eyelids when you see a ball coming towards you are some of the examples of reflex actions.
Now let us define a reflex action.
“A reflex action is a rapid and automatic response generated by our body to a sudden change in the surrounding.”
Reflex actions are controlled by the spinal cord.
SENSE ORGANS
The organs that help us to feel, smell, see, hear, taste and remain aware to the surrounding are known as sense organs. We have five sense organs. These are:
1. Eyes — sight
2. Ears — hearing
3. Nose — smell
4. Tongue — taste
5. Skin — touch
1. Eyes
Eyes help us to see the world around us. They are present below the forehead in the eye-sockets of the skull. They are covered by eyelids which protect them. Along with the eyelids, the eyelashes and the eyebrows also protect the eyes.
2. Ears
Ears help us to hear. Each ear has an ear canal. This receives sound which is then converted into nerve signal and sent to the brain. The brain helps to identify the sound.
3. Nose
The nose helps us to smell. It has tiny hair inside the two nostrils. Mucus present in the nostril clings the foreign particles and stop the entry of germs and dust into our body.
4. Tongue
The tongue helps us to taste. It helps to sense a variety of tastes which include sweet, sour, salty and bitter. It also helps us to speak and swallow. The surface of the tongue has a large number of taste buds which contain tiny hair. These help to recognise different tastes.
5. Skin
The skin is the largest sense organ in our body. It gives us the sensation of touch. It covers our entire body. The skin has nerve endings which help to detect heat, cold, pain and touch.
Assignment
Q. Draw the structure of all sense organs and write their functions in OCBs.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
14/06/2021, 16/06/2021
CH.03 NERVOUS SYSTEM AND SENSE ORGANS
Do you remember the way to your friend’s house? Why do your eyes blink? Where do dreams come from? How do you come to know when somebody touches you?
It’s the brain which helps us to think, reason and analyse things.
“The system that controls all other systems of our body is known as Nervous System”. It consists of nerves and fibres which send and receive messages from different body parts.
PARTS OF THE NERVOUS SYSTEM
The nervous system includes the following parts:
- Brain
- Spinal Cord
- Nerves (along with the five sense organs) Posture of human body showing the parts of nervous system.
BRAIN
The brain is the most important organ of the nervous system. It controls everything we do.
Location: It is present inside the skull. Function: It receives information from the nerves, processes it and send signals so that actions can be taken.
Parts of brain the human brain have three parts:
1. Cerebrum
2. Cerebellum
3. Brain stem
The largest and outermost part of the brain is the cerebrum. It is dome shaped and comprises 85% of the brain’s weight.
Functions:
- It controls the working of sense organs of our body.
- It is responsible for thinking, logic, memory, learning and intelligence.
2. Cerebellum
The cerebellum is also called “the little brain”. It is present towards the back of the head, behind the cerebrum. It is smaller than the cerebrum.
Functions:
- It maintains the balance and posture of our body.
- It regulates and co-ordinates the movement of muscles.
3. Brain Stem
Brain stem is located just below the cerebellum. It is the lowermost part of the brain.
It is interesting to know that it is the simplest part of human brain.
Functions:
- It is responsible for basic vital life functions such as breathing, digestion, controlling blood pressure and heartbeat.
- It also controls involuntary muscle movements.
SPINAL CORD
The nerves enclosed in vertebral column forms the spinal cord. It has the same composition as that of brain. The nerves are protected by the backbone. It extends from the lower part of the brain down through the spine.
Functions:
- It helps in the transfer of information and nerve signals between the brain and rest of the body.
- It also controls the reflex actions.
Example: Removing of hand on touching the hot object.
Nerves
Nerves carry information from parts of body to brain and then back to body. Sometimes in case of reflex actions this function is performed by spinal cord instead of brain. Nerves are of three types:
Sensory nerves: They carry messages from various parts of the body to brain or spinal cord.
Motor nerves: These nerves carry messages away from the brain or spinal cord to the muscles where the action has to be taken. Mixed nerves: These nerves carry out both the functions; they carry messages from the brain and bring them back to the brain.
REFLEX ACTIONS
On touching a hot object, you pull back your hand immediately. The secretion of saliva in your mouth on seeing a pizza for dinner, the blinking of eyelids when you see a ball coming towards you are some of the examples of reflex actions.
Now let us define a reflex action.
“A reflex action is a rapid and automatic response generated by our body to a sudden change in the surrounding.”
Reflex actions are controlled by the spinal cord.
SENSE ORGANS
The organs that help us to feel, smell, see, hear, taste and remain aware to the surrounding are known as sense organs. We have five sense organs. These are:
1. Eyes — sight
2. Ears — hearing
3. Nose — smell
4. Tongue — taste
5. Skin — touch
1. Eyes
Eyes help us to see the world around us. They are present below the forehead in the eye-sockets of the skull. They are covered by eyelids which protect them. Along with the eyelids, the eyelashes and the eyebrows also protect the eyes.
2. Ears
Ears help us to hear. Each ear has an ear canal. This receives sound which is then converted into nerve signal and sent to the brain. The brain helps to identify the sound.
3. Nose
The nose helps us to smell. It has tiny hair inside the two nostrils. Mucus present in the nostril clings the foreign particles and stop the entry of germs and dust into our body.
4. Tongue
The tongue helps us to taste. It helps to sense a variety of tastes which include sweet, sour, salty and bitter. It also helps us to speak and swallow. The surface of the tongue has a large number of taste buds which contain tiny hair. These help to recognise different tastes.
5. Skin
The skin is the largest sense organ in our body. It gives us the sensation of touch. It covers our entire body. The skin has nerve endings which help to detect heat, cold, pain and touch.
Assignment
Q.1. Draw the structure and label the human brain in your OCBs.
31/05/2021, 02/06/2021, 07/06/2021, 09/06/2021
Ch:- 02.
CIRCULATORY SYSTEM
In which of the above two cases, you will be able to fill the petrol in your car?
Obviously in Case II because here we have pipeline to transport petrol from tank to the engine.
Similarly, nutrition and digestion processes are of no value unless and until the digested food or nutrients are transported from the alimentary canal to all body cells, where these are actually needed and utilized. Hence, all higher organisms need such a pipeline system to transport nutrients which is known as circulatory system.
Similarly, nutrition and digestion processes are of no value unless and until the digested food or nutrients are transported from the alimentary canal to all body cells, where these are actually needed and utilized. Hence, all higher organisms need such a pipeline system to transport nutrients which is known as circulatory system.
Now watch this video to help you understand the chapter better.
Thus, “the system which helps in transporting nutrients and other substances from one part of the body to the other part of the body is known as circulatory system”.
In animals, it consists mainly of three parts.(i) Blood
(ii) Heart
(iii) Blood vessels (arteries, veins and capillaries)
BLOOD
The red coloured liquid which transports nutrients and other substances to all parts of the body is known as blood.
WORKING
- Lungs enrich the blood with oxygen. This oxygenated blood is poured into left auricle.
- From left auricle, the blood is pumped into left ventricle.
- From left ventricle it is pumped to all parts of body.
- The impure blood is collected and poured into right auricle.
- Right auricles pump it into right ventricle.
- Right ventricle pumps it to lungs for oxygenation. This entire circle repeats itself.
Blood contains cells known as red blood cells or erythrocytes.
Now watch this video to help you understand the chapter better.
BLOOD VESSELS
Blood flows in tubes which are known as blood vessels. Blood vessels can further be classified as arteries, veins or capillaries.
1. The arteries : These blood vessels originate from heart and distribute pure blood to all parts of the body.
2. The veins : These blood vessels collect impure blood from all parts of the body and pour it into heart.
3. The capillaries : These blood vessels are very thin and are present at the junction of an artery and a vein.
Functions of Blood
1. Blood helps in transporting digested food from the alimentary canal to all parts of the body.
2. It helps in transportation of oxygen for respiration.
3. It takes carbon dioxide formed during respiration to lungs for exhalation.
4. It helps in transportation of hormones.
5. It transports heat and hence maintain constant temperature of the body.
6. It maintains water level in the body.
7. It helps in the removal of waste material from the body.
3. It takes carbon dioxide formed during respiration to lungs for exhalation.
4. It helps in transportation of hormones.
5. It transports heat and hence maintain constant temperature of the body.
6. It maintains water level in the body.
7. It helps in the removal of waste material from the body.
Differences between Artery and Vein
Artery
- Arteries are deep seated.
- Arteries pump blood from heart to various parts of the body.
- Arteries have thick walls.
- Arteries mostly carry oxygenated blood.
Vein
- Veins are superficial.
- Veins collect blood from various parts of the body and take it to heart.
- Veins have thin walls.
- Veins mostly carry deoxygenated blood.
THE HEART
The heart of man is reddish brown in colour. It is the main pumping organ of the body. It pumps and collects blood to and from various body parts. It is of the size of a human closed fist.
Location
It is located between the two lungs well protected by lungs. The broad portion of heart is upwards and apex points downward.
It is located between the two lungs well protected by lungs. The broad portion of heart is upwards and apex points downward.
The heart of human has four chambers, two auricles and two ventricles. These are labelled as right auricle left auricle, right ventricle and left ventricle.
Now watch this video to help you understand the chapter better.
- Lungs enrich the blood with oxygen. This oxygenated blood is poured into left auricle.
- From left auricle, the blood is pumped into left ventricle.
- From left ventricle it is pumped to all parts of body.
- The impure blood is collected and poured into right auricle.
- Right auricles pump it into right ventricle.
- Right ventricle pumps it to lungs for oxygenation. This entire circle repeats itself.
Double circulation : The blood has to pass twice through the heart so as to circulate once through the body. This circulation is known as double circulation.
Assignment
Q.1. Draw the structure and label the human heart in your OCBs.
03 / 05 / 2021
Ch-1 The Skeletal System
Page - 6 to 7
The human body is the most complex of all organisms present on this earth. A human body is made-up of nearly 206 bones.The skeletal system is a system which supports the framework of bones in our body and gives it a particular and definite shape.
The human skeleton consists of the skull, the backbone, the ribcage and two pairs of limbs.
Skull : Acts like a helmet and protects the brain.
Forelimbs : Help us to lift various objects.
Ribcage : Protects delicate organs like heart and lungs.
Lower Limbs : Along with muscles they help in movement.
The framework of bones present in our body is known as skeleton.
Bone
Bones are made-up of minerals which include calcium and phosphorus. These make the bones strong.
Types of Bones
Bones may be short, long, flat or irregular.
Skull
The skull protects the brain. It is a hollow round structure present in the head.
Functions :
1 The skull covers and protects the brain.
2 It gives shape to the face.
3 It supports the teeth present in upper and lower jaw.
NOTE : All the bones that form the skull are fixed and immovable, except for the lower jaw.
Backbone
The bone present on the extreme back of our body is known as backbone. It is also known as the vertebral column or spine. The skull is attached to the backbone.
Vertebral Column — Long bony structure made-up of 33 bones.
Vertebra : The small bones that form the vertebral column are called vertebrae.
Function : The backbone encloses and protects the delicate spinal cord.
Ribcage
The bony cage present in the chest region is called the ribcage. It is made-up of 12 pairs of thin curved bones called ribs.
Sternum : The long flat bone present in the centre of chest is called sternum.
Backbone : The bone present at the back supporting the ribs is known as backbone. Now watch this video to help you understand the chapter better.Assignment : -1.) Draw "The Skeletal System" given on page no. - 6 in your OCBs.
The human body is the most complex of all organisms present on this earth. A human body is made-up of nearly 206 bones.
The skeletal system is a system which supports the framework of bones in our body and gives it a particular and definite shape.
The human skeleton consists of the skull, the backbone, the ribcage and two pairs of limbs.
Skull : Acts like a helmet and protects the brain.
Forelimbs : Help us to lift various objects.
Ribcage : Protects delicate organs like heart and lungs.
Lower Limbs : Along with muscles they help in movement.
The framework of bones present in our body is known as skeleton.
Bone
Bones are made-up of minerals which include calcium and phosphorus. These make the bones strong.
Types of Bones
Bones may be short, long, flat or irregular.
The human skeleton consists of the skull, the backbone, the ribcage and two pairs of limbs.
Forelimbs : Help us to lift various objects.
Ribcage : Protects delicate organs like heart and lungs.
Lower Limbs : Along with muscles they help in movement.
The framework of bones present in our body is known as skeleton.
Bone
Bones are made-up of minerals which include calcium and phosphorus. These make the bones strong.
Types of Bones
Bones may be short, long, flat or irregular.
Skull
The skull protects the brain. It is a hollow round structure present in the head.
Functions :
1 The skull covers and protects the brain.
2 It gives shape to the face.
3 It supports the teeth present in upper and lower jaw.
NOTE : All the bones that form the skull are fixed and immovable, except for the lower jaw.
Backbone
The bone present on the extreme back of our body is known as backbone. It is also known as the vertebral column or spine. The skull is attached to the backbone.
Vertebral Column — Long bony structure made-up of 33 bones.
Vertebra : The small bones that form the vertebral column are called vertebrae.
Function : The backbone encloses and protects the delicate spinal cord.
Ribcage
The bony cage present in the chest region is called the ribcage. It is made-up of 12 pairs of thin curved bones called ribs.
Sternum : The long flat bone present in the centre of chest is called sternum.
Backbone : The bone present at the back supporting the ribs is known as backbone.
The skull protects the brain. It is a hollow round structure present in the head.
1 The skull covers and protects the brain.
2 It gives shape to the face.
3 It supports the teeth present in upper and lower jaw.
Backbone
The bone present on the extreme back of our body is known as backbone. It is also known as the vertebral column or spine. The skull is attached to the backbone.
Vertebra : The small bones that form the vertebral column are called vertebrae.
Function : The backbone encloses and protects the delicate spinal cord.
Ribcage
The bony cage present in the chest region is called the ribcage. It is made-up of 12 pairs of thin curved bones called ribs.
Backbone : The bone present at the back supporting the ribs is known as backbone.
Now watch this video to help you understand the chapter better.
Assignment : -
1.) Draw "The Skeletal System" given on page no. - 6 in your OCBs.
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