Chapter 1
Physics
1.1
1.1.1
Force
Introduction
Force can be defined as any external push or pull which tends to change the state of
motion or rest of a body. It is a vector quantity as it possess both magnitude and
direction. It’s SI unit is Newtons or N (kg.m.s−2 ). There are various types of forces
such as:
ˆ Gravitational Force
ˆ Nuclear Force
ˆ Magnetic Force
ˆ Electrostatic Force etc.
1.1.2
Geocentric and Heliocentric Model
In the past, before 1542AD, people used to believe that earth was the center of the
universe. This model of the universe is known as geocentric model.
This model was later revised. Nicholas Copernicus put forward the idea of a
theory stating that all the planets revolved around the sun. This model is known as
heliocentric model. Galileo proved the theory by observing the solar system through
a telescope.
The way he proved the theory was through orbits (specifically he observed four
of Jupiter’s moons). Orbits are one of the effect of gravitational force.
1.1.3
Gravitational Force
Gravitational Force is a type of force. It is defined as the force between two objects
caused due to their masses. As it is a force, the unit of gravitational force is Newtons
(N). Gravitational force can also be termed as the force of gravitational attraction.
The effect of this force is more pronounced in fluids than in solids.
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Due to the reason that gravitation’s effect is felt more readily in liquids than in
solids, the tides occur due to the gravitational force exerted by the moon and sun
upon the ocean.
Sir Issac Newton proposed the idea of gravitation in 1687AD. He is the first
person to state a theory of gravitation. The theory states that: ”Every particle
in the universe attracts every other particle with a certain force which is directly
proportional to the product of their masses and inversely proportional to the square
of the distance between their centers.” In other words, it can also be stated that
according to Newton’s law: the gravitational force of attraction between any two
objects is proportional to the product of their masses and inversely proportional to
the square of the distance between their centers.
m1
m2
F
d
fig: Gravitational Attraction
From Newton’s law of gravitation we can end up at these following relations:
F ∝ m1 m2
1
F ∝ 2
d
Combining the above two relations we end up with the following law :
F =G
m1 m2
d2
Where ’G’ is the universal gravitational constant. G is defined as the gravitational
force between any two objects of mass 1kg each separated by a distance of 1m from
their centers.
It is called a universal constant because its value (6.67×10−11 Nm2 kg−2 ) doesn’t
depend the medium the objects are in, the masses of the two objects, nor the distance
between them.
Its value was first calculated through the use of sensitive spring balance by the
scientist Henry Cavendish at 1798AD.
Effects of Gravitational Force
There are many effects in the world which happen due to gravity only. Some of
these are:
1. Existence of orbits of heavenly bodies
2. Formation of stars
2
3. Existence of solar systems
4. Existence of tides
5. Existence of atmosphere
6. For keeping us on the ground
1.1.4
Gravity
Gravity is defined as the force of gravitational attraction acting on an object which
pulls it towards the center of a heavenly body. As it is a force, its a vector quantity
and it’s unit in the SI system is Newton.
Thanks to gravity an object has weight. Weight is defined as the amount of
gravity acting upon a body. In other words, it is the force exerted by an object upon
a heavenly body and vice-versa.
As gravity is a force, we know it produces acceleration. Now, acceleration produced due to the gravity of a heavenly body is known as acceleration due to gravity.
It’s a vector quantity and it’s SI unit is m.s−2 .
To calculate the acceleration due to gravity we can do the following:
m
R
M
fig: Acceleration due to gravity
Let’s consider that an object of mass ’m’ is standing on the surface of a heavenly
body with mass ’M’ and radius ’R’. From Newton’s Law of Gravitation we know
that the gravitational force acting upon the body is given by:
F =G
Mm
R2
We know that the object has weight as its being pulled towards the center by the
heavenly body and that the amount of force it is being pulled on by is equal to the
force of gravitation. Thus we can can also say that:
F = mg
3
Where ’g’ is the acceleration due to gravity. Now, equating these two equations we
get:
G
Mm
= mg
R2
GM
∴g= 2
R
Thus, the gravity acting on a body on the surface of a heavenly body is given by
the above equation. Now, depending on the height or depth of the body the gravity
changes. The new values are given by the following two equations for height and
depth respectively.
GM
(R + h)2
d
gd = g 1 −
R
gh =
Here, h = height of the object from the surface, and d = depth of the surface from
the center.
From the above equations we can see that acceleration due to gravity isn’t dependent on the object’s mass but rather the mass of the heavenly body. Thus we
can state that acceleration due to gravity is same for every object. But wee that
isn’t the case on earth and that is due to the existence of the atmosphere which
provides air resistance (a reaction force).
Thus the feather and coin experiment was done to prove that the acceleration due
to gravity is the same for all object in the absence of any reaction force.
It was first demonstrated by Galileo Galilei who dropped two stones from the
leaning tower of Pisa in 1590AD. Later, Robert Boyle demonstrated the actual
feather and coin experiment shortly after Galileo passed away.
The experiment was further done by Sir Issac Newton who used a glass tube of
1 meter length, vacuum pump, and a coin and feather. Through that he proved the
all objects fell at the same rate.
Another fact obtained from one of the above equation is that the force of gravity
grows lesser the deeper you go into a heavenly body. This is the case as whilst indeed
the force of gravity increases by the square of the radius, the mass of the object gets
reduced by the cube of the radius. Because of that the mass grows smaller much
faster and has greater effect on the gravity. For a better understanding, here is the
derivation of the aforementioned equation.
GM
R2
G × 43 × π × R3 × ρ
=
R2
4 GρπR
=
3 1
4
∴ g = GρπR
3
g=
4
Here ρ is the symbol representing density. Suppose that you go to a certain depth,
say d. Then the above equation will change in the following way:
4
gd = Gρπ(R − d)
3
Now, divide g by gd :
4
GρπR
g
= 4 3
gd
Gρπ(R − d)
3
g
R
=
gd
R−d
gd
R−d
=
g
R
d
R
−
gd = g
R R
d
gd = g 1 −
R
It is clear from the above equation, the acceleration due to gravity decreases when
once goes deeper.
1.1.5
Gravitational Field
The region of a space where the gravitational influence of a body is felt is known as
the body’s gravitational field. Its unit is Nkg−1 . There exists neutral points in an
object’s gravitational field. These points are where the gravitational field intensity
measures zero. These points are where artificial satellites are launched.
The equations which describe field intensity is the same as the ones which describe the acceleration due to gravity. As in,
GM
I= 2
R
1.1.6
Feather and Coin Experiment
5
fig: Feather and Coin Experiment
Materials Required
A feather, a coin, long glass tube (approx. 1m length), and vacuum pump.
Theory
The acceleration produced in a freely falling object due to gravity is called acceleration due to gravity. It depends upon the mass and radius of the heavenly body. Its
value changes from place-to-place.
Procedure
A feather and coin were dropped in the glass tube kept vertically simultaneously.
The air was then taken out from the tube by using vacuum pump after leaving
feather and coin in it. The tube was then inverted quickly as soon as possible
Observation
The coin feel faster than the feather in the presence of air. The coin and the feather
reached tot he bottom of the tube simultaneously when dropped in the absence of air.
Conclusion
From the above experiment, it can be concluded that acceleration due to gravity is
same for al objects i.e., acceleration due to gravity is independent upon the mass of
an object.
Precaution
1. A long glass tube should be taken
2. The glass tube should me made air free (vacuum) to get the correct result
1.1.7
Mass and Weight
Mass it the amount of matter contained within a body. It is a scalar unit and its
unit in SI system is kilogram. It is measured using physical or beam balance. It
is also a constant quantity, i.e., a one kilogram object will always be one kilogram
unless actual mass is removed from it.
Weight, on the other hand, is the amount of gravity acting on a body. It is also
the amount of force exerted by a body upon a heavenly body. As it is a force its unit
is Newton and it is a vector quantity. It is not constant as the weight of an object
changes from place to place, unlike mass. It is measured using spring balance.
The factors affecting mass are:
1. The size of atoms or molecules of body
2. The number of atoms or molecules of the body
The factors affecting weight are:
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1. The mass of the body
2. The value of acceleration due to gravity acting on the body i.e., the gravity
acting upon the body
1.1.8
Free Fall and Weightlessness
Free Fall is defined as the state of freely falling towards a heavenly body with no
reaction force acting. An object experiences weightlessness in free fall.
Weightlessness is the state of having no weight. It is experienced when:
1. The object is at free fall
2. The object is at space
3. The object is at the center of a heavenly body
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1.2
1.2.1
Pressure
Introduction
Pressure is defined as the force acting upon a surface normally per square unit area.
Force acting upon a surface normally is also known as thrust. It is a scalar quantity.
It is given by the equation:
F
P =
A
Where P is the pressure, F is the force, and A is the area.
Liquid pressure is the thrust exerted by a liquid per unit area. It is given by the
equation:
P = hdg
Where h is the height of the liquid, d is the density, and g is the acceleration due
to gravity acting on the liquid.
Like liquid, air also exerts pressure. The thrust exerted by the atmosphere per
unit area is known as atmospheric pressure. Atmosphere pressure is used for: filling
ink in a fountain pen, injecting medicine in a patient, for pumping air, etc.
1.2.2
Pascal’s Law
The French scientist Blaise Pascal propounded Pascal’s Law. He was born in 1623AD
and was a famous physicist, mathematician, and philosopher.
Pascal’s Law states that: ”The pressure exerted on a liquid enclosed within a
vessel is transmitted equally on all directions throughout the vessel.” In other words,
the theory states that a liquid enclosed in a vessel transmits pressure equally in all
direction normally when pressure is applied at a point on the container. This law is
based upon the following two properties of liquid:
1. Liquids can not be compressed
2. Liquids exerts pressure equally in all direction
Pascal’s Law can be verified through the following experiment:
8
fig: Verification of Pascal’s Law
Materials Required
A spherical vessel fitted with four pistons, water
Theory
Pascal’s Law states that a liquid kept in a closed container transmits pressure equally
in all direction normally when pressure is applied at a point on the container. The
law is based upon the fact that liquids can’t be compressed and that liquids exert
pressure equally in all direction
Procedure
A spherical vessel fitted with four piston was taken. The vessel was filled completely
with water through the upper hole of the piston. The valve of the piston was kept
to enclose liquid in the container.
Observation
When one of the piston, say A, was pressed inward direction the remaining piston
(B, C, and D) moved in the outward direction equally.
Result
The pressure applied at a point on a closed container transmits (distributes) equally
Conclusion
Liquid kept in a closed container transmits pressure in all direction equally and
normally when pressure is applied at a point on the container.
Precautions
1. The area of cross-section of each valve should be same
2. The piston must be friction-less
3. The vessel should be completely filled with water
1.2.3
Application of Pascal’s Law
Various devices like hydraulic press, hydraulic brake, hydraulic lift, etc are based
upon Pascal’s Law.
Hydraulic Press
9
fig: Hydraulic Press
Hydraulic press is a device which is constructed on the basis of Pascal’s Law. It is
used for
1. Pressing cotton
2. Pressing Paper etc.
A hydraulic press consists of two cylinders connected with a pipe. Both of the
cylinders are fitted with pistons. One of the cylinder is smaller whilst the other
one is larger. Due to Pascal’s law, this work as a force multiplier. We can see it
mathematically by doing the following:
Let the smaller cylinder be A and the larger cylinder be B then we have:
(Cross-sectional Area of A) AA < AB (Cross-sectional Area of B)
Suppose that the smaller piston is pressed with a certain force hence exerting certain
pressure. We know from Pascal’s Law that the pressure exerted on the smaller piston
is also felt by the larger piston, thus
PA = PB =⇒
FB
FA
=
AA
AB
Where FA is the force applied on the smaller piston and FB is the force felt by the
larger one. Rearranging the above equation we get:
FB =
AB
FA
AA
As AB > AA , FA is being multiplied by a coefficient > 1, thus the force felt on the
larger piston is greater than the force being felt on the smaller piston. Thus, we can
say that the force is being multiplied. Hence it (hydraulic press) is a force multiplier.
Hydraulic Lift
10
fig: Hydraulic Lift
Hydraulic lift is a device based upon Pascal’s Law. It is used to raise heavy vehicles
such as car, buses, trucks, etc. It works similarly to a hydraulic press.
In a hydraulic lift there are three cylinders. If we count the reservoir cylinder as
cylinder A, then cylinder B is the small cylinder fitted with a piston, and cylinder C
is the large cylinder fitted with a larger piston. There are two pipes used to connect
cylinder A and B and B and C respectively with a third pipe connecting cylinder C
and A. There are valves in all those pipes. The use of the valves and the reservoir
cylinder is to make it so that the piston is pressed permanently.
It works like this: when the small piston is pressed the water (liquid) is pressed
through the valve connecting cylinder B and C. More water is then funneled from
the reservoir into cylinder B through the valve in the pipe connecting A and B.
Due to the valve the water can’t go back so it is stuck there and thus cylinder C is
constantly pressured by the water within its cylinder. Then when the job is done,
the valve connecting cylinder C and A is opened and the water rushes right back
into the reservoir.
Hydraulic Brakes
Hydraulic brakes are devices based upon Pascal’s law. They are used to control the
speed of vehicles.
1.2.4
Density of Liquid and Upthrust
Density is the amount of matter contained with an object per unit volume. It is
given by the formula:
Density =
m
mass
=⇒ d =
volume
v
SI unit of density is kg.m3 . Another way to measure density is through the use of
relative density or specific gravity. It is defined as the ratio of the density of an
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object with the density of water at 4◦ C. Mathematically:
Relative Density =
Density of Object
Density of water at 4◦ C
Upthrust is defined as the upward force experienced by a body when partially
or wholly submerged in liquid. It is an upward force, thus its unit is Newtons.
There are three factors on which upthrust depends
1. Density of the liquid in which the object is being submerged in
2. Volume of the object immersed or submerged
3. Acceleration due to gravity
The equation to find out the upthrust is therefore:
U = vdg
Where v = the volume of the immersed part of the object, d = density of the liquid,
and g = acceleration due to gravity.
1.2.5
Archimedes’ Principle
Archimedes’ was born in 287BC in Sicily, he was a mathematician, physicist etc. He
propounded Archimedes’ principle.
The principle states that: ”When a body is partially or wholly immersed in a
fluid, it experiences an upthrust (an apparent loss in weight) which is equal to the
weight of the liquid (fluid) displaced by it.”
A body immersed or submerged in liquid experiences two forces: 1) the force of
gravity, and 2) the upthrust generated by the liquid.
We can verify Archimedes’ Principle by the following experiment:
fig: Verification of Archimedes’ Principle
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Materials Required
Eureka can, water, a stone, thread, spring balance, beaker, iron stand, top pan balance.
Theory
When an object is immersed in a liquid partially or completely the upthrust exerted
by the liquid is equal to the weight of the liquid displaced by the object. This is
called Archimedes’ Principle.
Procedure A stone was tied with thread and its weight was measured in air and
water separately. An eureka can was completely filled with water. The stone hanging with the spring balance was clamped in an iron stand then gently introduced in
the eureka can to collect the displaced water in an empty beaker placed near the can.
Observation
The weight of displaced water was collected in the beaker and the following calculation was done:
Weight of stone in air (W1 ) = 70gm
Weight of stone in water (W2 ) = 50gm
Upthrust (U ) = W1 − W2
= 70 − 50 = 20gm
Weight of Empty Beaker (W3 ) = 120gm
Weight of beaker with displaced water (W4 ) = 140gm
Weight of displaced liquid (Wl ) = W4 − W3
= 140 − 120
= 20gm
Result: U = Wl
Conclusion
The upthrust exerted by liquid is equal to the weight of liquid displace by the object
when it is immersed in a liquid
Precaution
1. Proper size of stone should be taken for the experiment
2. Sensitive measuring should be taken
3. Reading should be noted very carefully
Application of Archimedes’ Principle
1. Archimedes’ principal is application to construct sub-marines, hydrometer,
etc.
2. The principle is application is fly hot air balloons, to float ships in sea, etc.
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1.2.6
Law of Flotation
The law of flotation isn’t a complete principle as it is a case of Archimedes’ Principle. The law states that: ”When a body floats in a liquid, the weight of the floating
body is equal to the weight of the liquid displaced by it.”
Conditions of flotation
1. The weight of the liquid displaced by the portion of the body below the liquid
surface must be exactly equal to the weight of the floating body
2. The center of gravity of the body and center of buoyancy of the displaced
liquid must lie in the same vertical line
We can verify the law of flotation by doing the following experiment:
Materials Required
Eureka can, water, a floating object, a thread, spring balance, beaker, iron stand,
top pan balance
Theory
Law of flotation states that object floats in a liquid if it displaces liquid equally to
its own weight.
Weight of Object = Weight of displaced liquid
Where,
Weight of Displaced Liquid = Weight of beaker with displaced water - Weight of empty beaker
Observation
The reading was taken carefully and calculation similar to what we did in the previous experiment was done.
Conclusion
The upthrust experienced and the weight of the object is equal.
Precaution
1. A floating body must be taken
2. Sensitive measuring should be taken
3. Reading should be noted very carefully
There are various devices based on the law of flotation. Some of them are: hydrometer, lactometer, etc. Hydrometer is used to measure different densities of different
liquid. Lactometer (also known as a purity checker) is used to check the purity of
milk.
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1.2.7
Atmospheric Pressure
The thrust exerted by the atmosphere per unit area is known as atmospheric pressure. It varies depending on location, climate, and temperature. At sea level at 0◦ ,
atmospheric measures 760mmHg or about 101,300 Pascal. This value is also known
as the standard atmospheric pressure (the pressure exerted by the atmosphere at
sea level at 0◦ C).
Atmospheric pressure reduces with altitude. Thus the atmospheric pressure at
sea level is greater than the atmospheric pressure on Mt. Everest.
The device used to measure atmospheric pressure is known as barometer.
Importance of Atmospheric Pressure
1. Atmospheric Pressure helps to fill ink in fountain pen
2. It balances our body’s pressure
3. It helps to lift water using water pump etc.
The barometer by which we measure atmospheric pressure was first invented by
Evangelist Torricelli in 1643AD. There are different kind of barometers such as
mercury barometer, aneroid barometer etc.
1.2.8
Device Based Upon Atmospheric Pressure
Mercury Barometer
fig: Mercury Barometer
Mercury Barometer was first invented by Evangelist Torricelli in 1643AD.
The construction of the barometer is simple. A tube measuring 1m is taken and
is hence filled completely with mercury. The tube is kept inverted upon a trough
filled with mercury with the tube being supported by a stand.
Due to the atmospheric pressure pushing the mercury in the trough the mercury
level in the tube varies. The vacuum created at the tip of the tube is known as
Torricellian Vacuum. Mercury is used here for the following reasons:
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1. It is silvery white in color thus is easy to read
2. It doesn’t stick to the walls of the container
3. It has very high density and weight
Syringe
fig: Syringe
Syringe is a device based upon atmospheric pressure. It is used in medicine to inject
patient with medicine or to take blood out of patients.
Syringe’s construction is made up of three parts. A cylinder, a piston, and a
needle.
When the syringe’s piston is pulled upwards a vacuum is created in the cylinder (also known as storage cylinder) this vacuum causes the atmospheric pressure
to push substances into it (such as medicine or blood). Now, pushing the piston
downwards releases the substances contained within it from the needle.
Air Pump
fig: Hand Pump
16
Air pump is a device based upon atmospheric pressure. It is used to pump air into
the bladder of football, bicycle tyres, etc.
A standard air pump is made up of a cylinder, a nozzle, a handle, and a piston
valve.
When the piston is moved upward (also known as upstroke) by pulling the
handle, vacuum is created below the piston valve. The atmospheric pressure then
pushes air inside the vacuum through the piston valve.
When the handle is pressed downwards (also known as downstroke), the piston
valve pushes the air into the tube through the nozzle connected to it.
Water Pump
fig: Water Pump
A water pump is a device used to draw underground liquid. It is a device based
upon atmospheric pressure. It has two valves fitted in the cylindrical container with
outlet and handle.
A water consists of a main cylinder which acts as its body. There is a handle
attached on the cylinder’s top which is connected to the pump rod (piston). There
is a valve on the foot and on the piston. The water is collected from the foot valve
and is sent out through the outlet on top.
During upstroke the piston (pump rod) is moved upward by pushing the handle downwards. This creates a vacuum between the two valves. The atmospheric
pressure then causes the liquid to be pushed upward through the foot valve, forcing
it open. The liquid is then collected between the two valves.
During downstroke the handle is moved upwards and the piston downwards.
The piston valve is opened and the foot valve closes because of the weight of the
liquid. The liquid moves upwards and gets collected above the piston valve.
As the process of upstroke and downstroke continues, the water (liquid) can be
collected through the outlet.
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1.3
Energy
1.3.1
Introduction
Energy is the ability to do work. It is a scalar unit and its SI unit is Joules.
1.3.2
Sources of Energy
The objects or source from which we can get energy are known as sources of energy.
There are two types:
1. Renewable sources of energy
2. Non-Renewable sources of energy
Renewable sources of energy are the sources of energy which can’t get exhausted and
can be used over and over again. They are: solar energy, biomass energy, wind
energy, tidal energy, hydropower, etc.
Non-renewable sources of energy are the sources of energy which can get exhausted and can’t be used over and over again. They are: nuclear energy, coal,
petrol, kerosene etc.
1.3.3
Sun as the ultimate source of energy
Sun is considered to be the ultimate source of energy as it is responsible for almost
all sources of energy we currently use.
First example is obviously solar energy. But the others are wind, hydro, and
even most non-renewable sources.
Due to the heat of the sun the air heats up, this changes pressure, and causes
winds to form. Through these winds we derive wind energy.
Sun heating up the planet also is responsible for water cycle and the fact that
water even exists in liquid state. Without water cycle or water being frozen, hydroelectricity couldn’t be produced.
Sun is responsible for biomass energy as it is the main food source of green plants
which lay at the bottom of the food chain. Without autotrophs producing food, no
biological life could happen so therefore no biomass energy could be derived.
The sun is also responsible for coal and other fossil fuels as they are the product
of millions of years chemical and physical change upon biomass.
1.3.4
Basic Statistic of the Sun
Mass = 2 × 1030 kg
Diameter = 1.4 × 106 km
Temperature of inner core = 1.5 × 107◦ C
Mean distance between the sun and the earth: 1.5 × 108 km
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Surface Temperature: 5700◦ C
Energy Radiation: About 4 × 1026 Watt
Energy received by the earth: 1.4kW per square meter
1.3.5
Fossil Fuel Energy
The energy obtained from the fossils that remain buried under the earth crust is
called fossil fuel energy. Fossils are the remains or impressions of (ancient and dead)
plants and animals buried under the crust. Coal, mineral oil, and natural gas are
formed from fossils of plants and animals in nature thus they’re termed as fossil fuels.
Coal
Coal is a hard black mineral found in nature. It is the fossil fuel which is found in
solid state. It is widely used in industries, factories, and trains as the main source
of heat energy.
Depending on how high the percentage of carbon is in goal is divided these types:
1. Anthracite−it is about 90% carbon
2. Bituminous
3. Lignite
4. Peat
Anthracite is the highest quality of coal whilst peat is the lowest quality of coal.
In the context of Nepal, coal is found in Dang. Also, every type of coal except
Anthracite is found in Nepal.
Mineral Oil/Petroleum
Mineral oil includes liquid fossil fuels like petrol, diesel, keresone etc. Mineral oil
is used to run automobiles like car, truck bus, motorcycle, tractor, aeroplane, helicopter, etc.
The mineral oil just dug up from the crust is known as crude oil. It is purified
by fractional distillation to get natural gas, petrol, diesel, kerosene, mobil, paraffin,
etc. The residue left is called coal tar (asphalt) and it is used for pitching roads.
Similarly, raw materials to make plastics are also obtained from the leftover after
purifying mineral oil.
Natural Gas
It is is another form of fossil fuel. It is gaseous is nature. It is found above mineral
oil as it is produced in the same environment as mineral oil.
Advantages of Fossil Fuel
1. It is a cheap fuel
19
2. It is easy to store and transport
3. It can generate electricity
4. It is used to generate high heat
Disadvantages of Fossil Fuel
1. It is a non-renewable source of energy
2. It releases green house gases and causes air pollution
1.3.6
Hydropower
Hydropoer is the form of energy produced by rotating turbines through the use of
the kinetic energy of flowing water. Our country is the second richest in hydropower
potential. According to research, the country has the maximum generation capacity
of 83,000MW.
Advantages of Hydropower
1. Hydropower can generate electricity
2. It is cheaper in the long run
3. It does not create pollution
4. It can be easily be transported by using cable
5. It is renewable source of fuel
Disadvantages of Hydropower
1. It requires specific geography
2. It has a large upfront cost
3. Its construction requires a large area and has noticeable impact on the surrounding ecology
1.3.7
Alternative Sources of Energy
The energy sources which are used in the place of conventional sources of energy
are called alternative sources of energy. Biofuel, tidal energy, wind energy, solar
energy, etc. are the examples of alternative sources of energy. It is very important
to develop these sources of energy as they help to solve the climate crisis.
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1.3.8
Biomass Energy
Biomass can be defined as animal or plant product. The energy derived from biomass
is thus called biomass energy.
Biogas, another source of energy, is obtained by fermenting biomass with bacteria.
Our country’s government has provided subsidies to farmer to produce more biogas to reduce the use of non-renewable source of energy.
Advantages of Bio Fuel
1. Animal dung is used to produce biogas which is used for cooking food etc.
2. The residue produced while preparing biogas can be uased as organic fertilizer
3. It produces less smoke while burning thus doesn’t effect our health
4. It is cheap and can be produced easily
5. It can be used to run engines
1.3.9
Nuclear Energy
The energy obtained from nuclear reaction is known as nuclear energy. There are
two types of nuclear reactions:
1. Nuclear Fission: The reaction in which one heavier nucleus is split into two or
more smaller nuclei
2. Nuclear Fusion: The reaction in which two or more smaller nuclei fuse together
to form a relatively larger nucleus
Nuclear fission requires radioactive materials such as uranium, thorium, plutonium,
etc. Nuclear fusion, on the other hand, requires smaller elements but also needs
truly immense heat, pressure, and energy to make the reaction happen.
Nuclear fission is the only type of reaction being used for power generation.
”The change in mass between reactant and product is converted into energy,” is
the principle of formation of nuclear energy. The mass reduction or difference is
known as mass defect is denoted by ∆m.
The formula to calculate how much energy is produced by a given nuclear reaction
is known as the mass-energy-equivalence equation. It is also known as Einstein’s
mass-energy-equivalence equation. It is:
E = mc2
Where, E = the energy generated, m = mass difference or lost during the reaction,
and lastly c = the speed of light in vacuum.
In a nuclear power plant, the energy generated by the fuel is used to vaporize
water thus converting it into steam. The steam thus formed is used to spin turbines
21
which generates electricity.
Advantages of Nuclear Energy
1. The fuel is extremely dense so little fuel can generate a lot of energy
2. It doesn’t need much refueling
3. It requires less area for high energy production
Disadvantages of Nuclear Energy
1. It requires a large upfront cost
2. It produces nuclear wastes as byproduct which is extremely dangerous
1.3.10
Wind Energy
The energy obtained from the kinetic energy of blowing wind is known as wind
energy. It is a renewable source of energy best fit for countries where wind blows
for a long time.
As our country is a mountainous country and wind blows continuously for in
some parts. Thus we can build wind mills in those locations to generate electricity.
1.3.11
Tidal Energy
The energy derived from tides of seas or oceans is known as tidal energy.
The is energy generated by making seawater rotate turbines. It is done so with
the help tides.
Dams are made such that during high tide water gets collected on the other side
and then send through a tunnel where a turbine is spun by the current of water. The
current is formed with the difference of height of water caused due to the difference
of water level (tides).
Tidal energy is physically unavailable to landlocked country.
1.3.12
Solar Energy
Solar energy is considered to be among the best if not the best alternative source
of energy. It works by converting the solar radiation from the sun into electricity
through the use of photo cells.
Solar energy can be used to do various tasks such as heating water or generating
electricity. They’re especially useful in remote areas where there might not be proper
electrical infrastructure.
22
1.3.13
Geothermal Energy
Geothermal energy is the energy derived from the heat under the earth. It works
by sending down pipes deep underground filled with water to convert to that into
steam. The steam is then extracted by another set of pipe which is then used to
run steam engine to turn generators to generate electricity.
The temperature of the earth increases by 20◦ and 80◦ per km in volcanic passive
and active region respectively as we go underground.
1.3.14
Energy Crisis
The shortage or scarcity of available forms of energy is called energy crisis. The
main causes of the crisis are:
1. Rapid Population Growth or Overpopulation
2. Industrialization
3. Urbanization
Methods to combat the energy crisis:
1. The existing sources of energy should be used wisely and economically
2. Alternative sources of energh such as solar energy, wind energy, biomass energy, etc. should be developed and used
3. Population growth should be controlled
4. Awareness should be generated for wise and economic use of existing sources
of energy
Methods for conserving energy at home:
1. Food should be cooked in pressure cookers to save energy
2. Computer, television, bulbs, etc. should be switch off if their operation is not
necessary
3. LED bulbs should be used instead of filament bulb to save electricity
At the present the world’s energy needs are met mostly by non-renewable sources of
energy. Coal fulfills 27% of energy demand and mineral oil fulfills 35% of the energy
demand. Lastly, the demand of energy is increasing at the rate of 2.3% per year
due to various factors including population growth. This rate of increase may cause
energy crisis in the near feature.
23
Mineral Oil
35%
Coal
27%
3%
5%
17%
13%
Nuclear Energy
Hydroelectricity
Biomass
Natural Gas
24
1.4
1.4.1
Heat
Introduction
Heat is the form of energy which gives us the sensation of hotness or coldness. It is
a scalar quantity and its SI unit is Joules. Temperature is the degree of hotness or
coldness of a body. It is a scalar quantity and its SI unit is Kelvin or Celsius.
According to kinetic molecular theory, heat is defined as the total sum of kinetic
energy present in the molecules of matter whilst temperature is the average kinetic
energy of the molecules of the matter.
Heat is measured by device called caloriemeter whilst temperature is measured
through thermometers.
In CGS system, the unit of heat is calorie. 1 calorie = 4.2 joules.
Factors affecting the heat energy present in the body
1. The number of molecules present in the body or mass of the body
2. Average kinetic energy of the molecules present in the body
From above it is easy to say that the heat present within a body is proportional to
the mass of the body and average kinetic energy of the molecules of that body.
Different substances react to heat energy differently. This is due to the molecules
of matter having different properties. This fact makes some substances have higher
hotter temperature than others even if they were given equal heat energy and had
same mass.
1.4.2
Thermometer
Thermometer is the device used to measure the temperature of a body. When a body
is heated it expands and contracts when it is cooled. This is the principle behind the
thermometer which is known as Thermal Expansion.
There are various types of thermometer such as laboratory thermometer, clinical
thermometer, and maximum-minimum thermometer.
25
Clinical Thermometer
fig: Clinical Thermometer
The thermometer used to measure the temperature of the human body is known as
called a clinical thermometer.
The thermometer consists of the body (a prismatic glass tube), a thin capillary
which houses the thermometric liquid (mercury) where there is a constriction near
the tip (close to the bulb) which functions to not let the mercury flow fall back
immediately when removed from the body, and lastly there is a bulb which is used
as a medium to transfer heat to the mercury.
In a clinical thermometer, the temperature ranges from 35◦ to 42◦ as the average
body temperature of a human is 37◦ C.
Laboratory Thermometer
fig: Laboratory Thermometer
The thermometer which is used to measure the temperature of various objects in
the laboratory is called laboratory thermometer.
26
Its construction is similar to that of a clinical thermometer i.e., there is a glass
tube which houses the capillary which further houses the thermometric liquid (mercury or dyed alcohol). But unlike clinical thermometer it doesn’t have kink and
it’s longer than clinical thermometer. The biggest difference is in the size of the
bulb which helps laboratory thermometer make quicker reading due to greater heat
transfer.
This thermometer is graduated between -10◦ C and 110◦ C
Maximum-minimum thermometer
fig: Maximum-minimum Thermometer
It is the thermometer is used to check the maximum and minimum thermometer of
a place over a period of time (a day).
In this thermometer both alcohol and mercury is used. There are two bulbs in
the thermometer Both of these are connected by a tube which is in a sharp U shape.
On one side of the tube there’s alcohol whilst on the other there’s mercury. The
mercury tube shows the maximum thermometer whilst the alcohol tube shows the
minimum thermometer.
The temperature is seen through the index. The index keeps moving due to
the expansion and contraction of the liquid within the tub. For the maximum
temperature the alcohol expands which exerts pressure on the mercury causing to
rise thus pumping the index higher. For minimum temperature the alcohol contracts
and is thus pushed by the mercury which also moves the index. The indexes can be
rest using magnets.
The scale on the minimum side is in ascending order ranging from -25 to 40◦ C
whilst the scale on the maximum is in descending order going from 40 to -25◦ C.
1.4.3
Thermometric Liquid
The two most popular thermometric liquids are alcohol and mercury. They each
have their own merits and demerits
Advantages of mercury
27
1. Mercury can be seen clearly in the capillary due to its silvery white color
2. It is a good conductor of heat
3. It can measure temperature ranging from -39◦ C to 357◦ C
4. It doesn’t stick to the inner wall of the capillary
Disadvantages of mercury
1. It can’t measure very low temperature as -39◦ C is its freezing point
2. It is a toxic metal
3. It is an expensive metal
Advantages of Alcohol
1. Alcohol is suitable to measure very low temperature as it can measure temperature ranging from -115◦ C to 78◦ C
2. It gives a much more accurate measure as its rate of expansion is six times
greater than mercury
3. It is not an expensive liquid
Disadvantages of Alchol
1. It is a colorless liquid thus it requires coloring
2. It can’t measure high temperature as it’s boiling point is 78◦ C
3. It sticks to the walls of the tube
1.4.4
Specific Heat Capacity
The total amount of heat required to raise the temperature of 1kg mass by 1K or
1◦ C is called the specific heat capacity of the body. Its SI unit is Jkg−1 K or Jkg−1◦ C.
Here is a table having a list of specific heat capacity of various materials:
28
S.N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Specific Heat Capacity (in Jkg−1◦ C)
234
140
460
400
447
900
130
360
4200
2100
2400
800
2000
1670
2200
670
Substances
Silver
Mercury
Iron
Copper
Steel
Aluminum
Lead
Brass
Water
Ice
Alcohol
Sand
Vegetable Oil/Cooking Oil
Petrol
Kerosene
Glass
Water is a very common substance with a very high specific heat capacity. It is for
that reason it is used as coolant due to its high heat capacity of 4200Jkg−1◦ C it
takes 4200J to raise the temperature of 1kg water by 1◦ C.
1.4.5
Heat Equation
Conservation of energy states that energy can neither be created nor destroyed but
can be changed from one form to another. Also similarly, heat energy also flows from
hot body to cold bodies. Thus, from there we’ve: the amount of heat lost and the
amount of heat gained by two objects of different temperature is same. This principle
is applicable provided that no heat is lost to the surrounding. This principle is called
the principle of calorimetry. Thus based upon this principle we can derive a physical
equation which tells us the amount of heat lost or gained by a substance, provided
that no heat is lost to the surrounding.
This equation is known as the heat equation:
Q = msdt
We can derive it by the following:
We know that the amount of heat gained is proportional to different in temperature and the difference in temperature is inversely proportional to the mass of the
body. Mathematically:
Q ∝ dt
dt ∝ m−1
29
(1)
(2)
Where Q = heat energy gained/lost, dt = difference in temperature, and m = the
mass of the body. Combining (1) and (2) we get:
Q ∝ mdt
∴ Q = msdt
Where s is a constant known as the specific heat capacity of the body
30
1.5
1.5.1
Light
Introduction
Light is the type of energy which gives us the sensation of vision. It is produced
from hot object.
1.5.2
Lens
A piece of transparent matter (e.g: glass or plastic) having refracting surfaces is
called lens. They form image through the refraction of light rays. They’re used in
various optical instruments such as cameras, microscopes, telescopes, etc.
A lens consists of two refracting surfaces, of which one may be spherical or plane.
There are two types of lenses:
1. Convex Lens
2. Concave Lens
A convex lens is the lens which is thick in the middle and thin at the edges. A
convex lens converges parallel rays of light at a point after refraction thus it is called
a converging lens. On the basis of the shape there are three types of convex lens:
1. Biconvex lens (they’re also simply called convex lens)
2. Planoconvex lens
3. Concavoconvex Lens
A concave lens is the lens which is thin the middle and thin and thick at the edges.
A concave bends parallel rays thus it is also called diverging lens. Based on shape,
there are three types of concave lens:
1. Biconcave lens (like with convex, they’re simply called concave lens)
2. Planoconcave lens
3. Convexoconcave lens
1.5.3
Terminology Related to Lens
1. Optical Center: It is the geometrical center of the lens. It is denoted by O. A
ray of light passing through the optical center doesn’t deviate.
2. Center of curvature: It is the center of the sphere from which the lens has
been cut. It is denoted by C or 2F. A lens has two centers of curvature.
3. Focal Length: Focal length of a lens is the distance between the optical center
and the principal focus of the lens. It is denoted by f.
31
4. Principal Focus: The point on the principal axis where the rays of light parallel to principal axis pass through after refraction or appear to diverge after
refraction is called principal focus. It is denoted by F.
5. Radius of Curvature: Radius of curvature is the radius of the sphere which
the lens is cut. It is denoted by R. It is the distance between optical center
and the center of curvature. Radius of curvature is equal to the twice of the
focal length. It is also denoted as 2F.
6. Principal Axis: The straight line passing through optical center and center of
curvature is called principal axis. It can also be defined as the straight line
passing through two centers of curvature of the lens.
1.5.4
Refraction of Light through lens
2F
F
O
F
2F
For a convex lens, a parallel ray gets converged towards the focus. Whist the ray
going through optical center doesn’t deviate. On the other hand when the ray
comes through the focus it gets refracted in such a way that it becomes parallel to
the principal axis after the refraction.
2F
F
O
F
2F
In concave lens, the parallel rays seems to get refracted in such a way that the ray
seems to get diverged from the focus and the line passing through the optical center
without any deviation.
1.5.5
Image Formed by a Convex Lens
At infinity
When an object is at infinity from a convex lens the image is formed at focus. The
image is:
32
1. Real
2. Inverted
3. Highly Diminished
2F
F
O
F
2F
Beyond the center of curvature or 2F
When the object is beyond the center of curvature the image is formed between F
and C (2F) on the other side of the lens. The image is:
1. real
2. inverted
3. diminished
A
2F
F
O
F
B′2F
B
A′
At the center of curvature or 2F
When an object is placed at the center of curvature (C) or 2F of a convex lens,
image is formed at C or 2F on the other side of the lens. The image is:
1. real
2. inverted
3. same size
33
A
2F
B
F
O
F
B′
2F
A′
Between 2F and F
When an object is placed between F and 2F of a convex lens, the image is formed
beyond 2F on the other side of the lens. The image is:
1. real
2. inverted
3. enlarged
A
2F
F
O
B′
F
2F
B
A′
At F (principal focus)
When an object is at principal focus, the image is formed at infinity on the other
side of the lens. Thus, the image is:
1. real
2. inverted
3. highly enlarged
A
2F
F
B
O
F
2F
34
Between principal focus and optical center
When an object is placed between principal focus (F) and optical center (O), the
image is formed beyond the object on the same side of the lens. The image is:
1. virtual
2. erect
3. enlarged
A′
A
2F
B′
1.5.6
F
O
F
2F
B
Image Formed by a Concave Lens
Object between infinity and optical center
When an object is placed anywhere between infinity and optical center, the image
is formed between principal focus and optical center. The image is:
1. virtual
2. erect
3. diminished
35
A
2F
F
A′
F
O
2F
B′
B
Object placed at infinity
When an object lies at infinity from a concave lens, the image is formed on the same
side of the object. The image is:
1. virtual
2. erect
3. highly diminished
2F
1.5.7
F
F
O
2F
Power of lens
The reciprocal of the focal length (in meters) of a lens is called the power of the
lens. It can also be defined as the ability of a lens to converge or diverge the rays of
light falling on it.
The power of a lens having less focal length is more and vice versa. The power
of a convex lens is positive and that of a concave lens is negative.
The power of a lens is calculated by the given formula:
P =
36
1
f
Where, P = power of the lens, and f = focal length of the lens in meters.
In SI system the power of lens is measured in diopter. It id denoted by D. Diopter
(D) is also measured in radian/m.
1.5.8
Magnification
The ratio of the height of the image to the height of the object is called magnification.
It is calculated by the given formula:
m=
I
O
Where, m = magnification, I = height of the image, and O = height of the object.
As magnification is the ratio of two same physical quantities it has no unit.
Magnification can also be defined as the ratio of image distance to the object
distance.
m=
v
u
Where, v = image distance, and u = object distance.
1.5.9
Human Eye
Human eye is a spherical organ located in the orbital cavity in the facial region.
Each eye consists of biconvex lens thus it is called an optical instrument. Humans
use it to see the outside world.
The eye refracts the rays of light and forms a real, inverted, and diminished
image on the retina. The photosensitive cells on the walls of the retina capture that
image and convert it into nerve impulses which is later translated by the brain thus
giving us vision.
1.5.10
Accommodation of the Human Eye
Accommodation of eye can be defined as the ability of an eye to focus the image of
the objects at different distances on the retina by changing its focal length.
Ciliary muscles contract and relax to change the focal length of the eye lens.
It contracts for nearer object (thus decreasing the focal length and increasing its
power) and relaxes for far objects (thus increasing the focal length and decreasing
its power).
The nearest and farthest distance that a normal eye can see clearly without any
difficult is called range of normal eye. The range of normal eye is at a distance of
25cm from the eye to infinity where the former is known as the near point and the
later as the far point.
37
1.5.11
Defect In vision
If a person cannot see nearby or distant objects clearly then that state is known as
the defect of vision. It is caused when the image is not formed on the retina. It is
of two types:
1. Myopia or shortsightedness
2. Hypermetropia or longsightendness
Myopia
A person suffering from myopia cannot see nearby object. It is caused because of:
1. Thickening of eye lens (increases the power of the lens)
2. Elongation of eyeballs
In a myopic eye, the image of the distance object forms in front of retina due to
high converging power of the lens. Here the far point is less than infinity.
It can be cured by using a concave lens of suitable thickness. The lens diverges
the rays coming from distance objects and these rays are converged by the eye lens.
As a result, the image is formed at the retina.
Hypermetropia
In this defect the person cannot see near objects due to the low converging power of
the lens. The near point in such a case is greater than 25cm. The main causes are:
1. Shortening of eyeball
2. Decrease in the thickness of the lens
It is removed by using convex lens of appropriate power. The rays of coming from
nearby objects are converged in such a way that it appears to be nearer and thus
the image is formed at the retina.
1.5.12
Correction of Defects in Vision
Myopia
O
38
Hypermetropia
O
39
1.6
Electricity
Electricity can be defined as the flow of charge. There are two types of electricity
static electricity and current electricity.
There are two types of electric current:
1. AC: AC or alternating current is defined as the electric current which is periodically changing its polarity and magnitude. The rate of change of the
polarity and magnitude of the current is measured in hertz.
2. DC: DC or direct current is defined as the electric current which doesn’t
change its polarity or magnitude.
There are various effects noticed with current electricity. These effects are caused
due to the electric current which are:
1. Heating Effect
2. Lighting Effect
3. Magnetic Effect
4. Chemical Effect
1.6.1
Heating Effect
The phenomena where a conductor is heated by the electric current passing through
it is known as the heating effect of current electricity.
This phenomenon is the main principle behind devices such as heaters, electric
irons, immersion rod, etc. These devices have a heating element which is a piece of
conductor which converts electrical energy into heat energy when a current is passed
through.
For the above mentioned devices, a nichrome coil is used as the heating element.
The reason nichrome is used−which is a an alloy of nickel and chromium in 6:4
ratio−is because it is a material with high resistance. It is shaped like a coil because
it increases resistance.
In summary, the reason why a nichrome coil is used can be enumerated as follows:
1. Nichrome provides high resistance which causes more electrical energy to get
converted into heat energy
2. Nichrome has a high melting point of 1400◦ C which means that even at 900◦ C
which is its working temperature it will not deform
3. Nichrome doesn’t oxidize which is extremely helpful as it works at 900◦ C
4. The reason why nichrome is coiled is because a coil will provide higher resistance when compared to a straight wire
40
1.6.2
Lighting Effect
Lighting effect is defined as the phenomena where a conductor becomes so hot due
to the passing electric current that it becomes a luminous object i.e., it gives off
visible light.
Filament Lamp
It is the electrical device which converts electrical energy into light energy through
the use of a high resistance filament. Here, the said filament is called the lighting
element. Like with heating element, a lighting element is the substance or coil which
converts electrical energy into light energy.
It consists of a glass bulb which is filled with non-reactive or noble gases so that
the filament (which is generally made from tungsten due to it high resistance and
melting point) doesn’t oxidize. The filament is connected to the two terminals via
a thick wire. With other wires being in place to support the filament.
The reason for the use of tungsten in the filament are:
1. It has high resistance which allows it to reach high temperature
2. It has high melting point which allows it to survive its working temperature
of 2900◦ C
3. Its property of being oxidized at high temperature is negated by the inert gas
filled glass bulb
Filament lamp is extremely inefficient as it only coverts 10% of the input electric
energy into light energy. It also only has a lifespan of 1000 hours.
Fluorescent Lamp
It is the device which converts electrical energy into light energy with the help of
mercury vapor and fluorescent powder.
The device is made up of a long tube with electrodes connected at the two ends,
one being the cathode and the other being the anode. The tube’s interior surface
is lined with fluorescent powder with the volume of the tube being occupied by
mercury vapor.
When electron is passed from the cathode to the anode after the device is connected to a circuit, the electrons excite the mercury atoms causing them to release
ultra-violet rays due to their electrons being knocked into higher energy orbitals.
Those ultra-violent rays are then turned to visible rays thanks to the fluorescent
powdering coating the inner walls.
Fluorescent lamps are more efficient when compared to filament lamps as they
convert 30% of the input electrical energy into light energy with the rest being converted into heat. They also last longer at 3,000 hours.
Compact Fluorescent Lamp
Compact fluorescent lamp is a special type of fluorescent lamp. It is condensed in
nature and much more efficient. It’s efficiency is close to 90%.
41
LED
LED or light emitting diodes are special types of diodes which release light when
current passed through them. LED lamps use these diodes to convert electrical
energy into light energy.
Due to the nature of the diodes, they are extremely efficient with its efficiency being around 90%. Furthermore, due to its high efficiency−thus low energy consumption−,
better life span or physical robustness, smaller size, and faster switching is the most
the popular type of lighting device in the world and is used for various applications
such as:
1. Automotive headlamps
2. General Lighting
3. Traffic Signals etc.
1.6.3
Magnetic Effect
Hans Christian Oersted discovered the magnetic effect of current electricity in the
year 1819 AD. He did so by observing that a compass needle moved in the presence
of a conducting conductor i.e., a conductor through which an electric current was
flowing through.
Thus we can say that the phenomenon where a magnetic field is produced due
to an electric current passing through a conductor is known as the magnetic effect
of electric current. This effect is used in various devices such as:
1. Microphone
2. Speakers
3. Televisions
4. Electromagnets etc.
1.6.4
Electric Bell
It is a device based upon the magnetic effect of electric current. It is used in schools,
offices, etc. to notify the people about the time.
Making of the device is simple. The bell has a U-shaped iron core with a solenoid
wrapping around it. There is an iron in front of the electromagnet. The iron plate
is connected with a hammer which hits a gong.
The contraption is made in such a way that when the switch the turned on the
flow of current creates a magnetic field on the U-shaped iron core which attracts
the iron plate in front of it causing the hammer to hit the gong in the process as
the distance between the magnet and the plate is farther than the distance between
the hammer and the gong. As the plate itself is responsible for a part of the circuit,
when it moves towards the magnet the circuit breaks thus the current stops flowing.
42
This causes the plate to go back to its original place. But this again makes the
circuit again thus through the periodic motion of the iron plate connecting and
disconnecting the circuit, the hammer continuously hits the gong when there is
power.
1.6.5
Electromagnetic Induction
Electromagnetic induction is the phenomenon where an electric current is produced
in a conductor when it cuts against the magnetic flux of a magnet. The electric
current is produced because the when the conductor cuts against the magnetic flux
emf is produced in the conductor i.e., positive charge and negative charge builds in
the ends of the conductor. The current produced in the conductor is called Induced
Current.
This phenomenon was first discovered by Micheal Faraday in 1831AD. He had
propounded the following laws which are also known as laws of electromagnetic
induction:
1. Whenever a conductor is placed in a changing magnetic field, emf is produced
on the conductor
2. The emf induced in the conductor only lasts as long as there it cuts through
the magnetic flux
3. Emf is proportional to the rate of change in the magnetic flux
In general, to increase the amount of induced current in a conductor we can do the
following:
1. Have more coils
2. Increase the rate at which the flux change i.e., intersection
3. Increase the strength of the magnet
4. Decreasing the distance between the magnet and the conductor
1.6.6
Bicycle Dynamo
43
fig: Bicycle Dynamo
It is a device based upon electromagnetic induction which converts mechanical energy into electrical energy.
A dynamo is made up of a bottle with a movable lid which is placed against the
wheel of the bicycle. That lid is connected with a permanent magnet. The magnet
is placed closed to a conductor which is wrapped with a wire.
When the bicycle moves, the magnet is rotated which converts mechanical energy
into electrical energy through the phenomenon of electromagnetic induction. The
generated electrical energy is then used to turn on the headlight on the bicycle.
1.6.7
Generator
fig: AC Generator
fig: DC Generator
Generator is a device which is used to convert large amount of mechanical energy
into electrical energy. It works on the principle of electromagnetic induction.
44
In a generator, there is a rectangular coil which is called an armature which is
capable of rotating. The armature is made up of a conductor around which the
wires are wrapped around.
The armature is attached to a handle so that it can be rotated i.e., moved. The
armature is connected to slip rings or split rings depending on which type of current
needs to be produced. Slip rings produce AC whilst split rings produce DC current.
The slip rings are attached to carbon brushes which are attached to wires which are
responsible for delivering the current.
1.6.8
Electric Motor
fig: AC Motor
fig: DC Motor
Electric motor is a device which converts electrical energy into mechanical energy.
This device is based upon the principle of motor effect. Motor effect is the phenomenon caused when a current carrying conductor’s magnetic field interacts with
another magnetic field to create a force on the conductor which causes it to move.
45
An electric motor consists of an armature which is attached to either a slip ring
or split ring connected with wires with the help of carbon brushes. The armature
is surrounded by magnet of opposite poles to create the required external magnetic
field. Current is provided through a sourced attached to the wires connecting to the
carbon brushes. The carbon brushes caused the current to jump to the armature
which due to motor effect convert that electrical energy into mechanical energy.
1.6.9
Transformer
Transformer is a device which is used to change the voltage of an AC current. This
device is based upon the principle of mutual induction.
Transformer works only on AC as DC doesn’t create a changing magnetic field
which can’t induce current in another conductor due to the fact that the conductor
on the other side doesn’t cut any magnetic flux i.e., there is no change in the magnetic
flux.
On the same note, a transformer can’t change the amount of input energy. Thus,
the input and output energy will be equal. It can also be used to change the
frequency of the current.
A transformer consists of a layers of thin rectangular iron frames to reduce energy
lost due to heat. The rectangular body thus formed is known as the iron core. Each
layer is covered with varnish or shellac to insulate it. Then insulated copper wires
are wrapped around opposite breadths of the rectangular frame.
The voltage of the current which is going into the transformer is known as input
voltage or primary voltage. This voltage is responsible for generating the magnetic
field within the primary coil−the coil which takes in the input voltage. The output
voltage is recovered from the secondary coil.
The relation between the voltage and the number of coils is given by the following
equation:
N1
V1
=
V2
N2
The reason the above equation is true is because of the following reasons:
Voltage is proportional to the coil due to the resistance the coil provides. We
know this relation from Ohm’s law. Thus we can say:
V1 ∝ N1
V2 ∝ N2
We can rewrite the above expression as:
V1 = kN1
V2 = kN2
(1)
(2)
The reason for the same constant is the the coils are made up from the same materials. Thus their resistivity is the same.
Now dividing (1) and (2)
N1
V1
=
V2
N2
46
1.6.10
Some Electrical Appliances and their Uses
Battery Charger
It is the device which is used to provide energy to electric batteries. One of the
charger is connected to the battery and the other end is connected to the supply
current.
It allows charge to be stored in the battery. It also stops when the battery is full
due to the help of the cut off system in the charger.
Adapter
It is the electrical device which is used to convert AC to low voltage DC.
Inverter
The term inverter was first introduced by David Chandler Prince in 1925AD. It
converts AC current into DC current.
It helps to store direct current in a battery by converting the AC provided in our
outlets into DC to charge whilst changing the DC of the battery into AC to provide
electricity to the required appliances in case of load shedding.
Solar Cell
Solar cell is the electric device which converts light energy into electrical energy.
Solar cell works due to photovoltaic which was discovered by Alexander Edmond
Becquerel.
A photovoltaic’s major component is the solar module. They’re made out of
semi-conducting material which is silicon which is laminated in n-type or p-type
layers. When photons of light hit these layers, a potential difference is generated in
a phenomenon called the photovoltaic effect.
1.6.11
Safety measures when working with Electricity
Working with electricity is dangerous as thus the following measures should be
followed to protect oneself from harmful effects of electricity.
1. Use high quality wires
2. Make sure to follow proper standards for example: the wires are all of the
right color
3. Make sure that there are no faulty sockets etc
4. Make sure that there are no open live wires
5. Make sure that everything is plugged in properly such as the live wire being
connected to switches
6. To wear protection when handling circuits, i.e., rubber gloves etc
7. All electrical appliances must be properly earthed
47
1.6.12
Electric Consumption
The amount of electricity that one uses in their house is measured in unit. Unit is
common unit of electrical energy used in households. It is equal to 1 kilowatt hour.
1 Unit = 1kW hr
= 1000W × 60 × 60s
= 3.6 × 10 × J × s−1 × s
∴ 1 Unit = 3.6 × 103 J
Depending on the power consumption of the load, the number of load, and the
time it was run for, the electrical energy consumption for that set of load(s) can be
calculated with the following equation:
E = npt
Where, n = number of loads, p = power consumption of load, and t = time the load
was run in
Due to the unit of Unit being kW hr the power consumption should be in kW
instead of just watt, and the time must be in hours instead of seconds.
Just like how 1 kilowatt is equivalent to 1,000 watt, here is a list of a few more
units used to measure greater amount of power:
1kW = 1000W
1M W = 1 × 106 W
1hp (Horse Power) = 746W
With the knowledge of the total amount of energy cost, one can calculate the cost
by multiplying E with the unit cost of energy.
48
Chapter 2
Chemistry
2.1
Classification of Elements
The division of elements according to their similarities and dissimilarities is called
the classification of elements.
2.1.1
Periodic Table
A table or chart where elements are grouped based upon their similarities and dissimilarities is called a periodic table.
2.1.2
Mendeleev’s Periodic Table
Russian chemist Dimitri Mendeleev (1834-1907AD) formulated the Mendeleev’s periodic table according to the Mendeleev’s periodic law. The table had arranged all
63 elements according to Mendeleev’s periodic law.
Mendeleev’s periodic law states that: ”The physical and chemical property of
the elements is the periodic function of its atomic weight (or mass).”
In Mendeleev’s periodic table, there are 8 groups (vertical columns) and 7 periods
(horizontal rows).
Characteristics of Mendeleev’s Periodic Table
1. The elements are listed on the basis of their increasing atomic mass
2. There are seven horizontal rows called periods and eight vertical columns called
groups
Advantages of Mendeleev’s Periodic Table
1. There was a regular progression in the physical and chemical properties
2. The group number of an element indicates highest oxidation state it can attain
3. There were many vacant spaces in table for the elements to be discovered
4. It arrangement helped to correct the atomic of a number of elements
49
Disadvantages of Mendeleev’s Periodic Table
1. It isn’t always accurate with its placement
2. It doesn’t provide clear idea about the structure of the atom
3. Lathanide and actinide have been assigned in the periodic table which is
against the periodic law
4. Alkali metal and coinage metals (Cu, Ag, and Au) which differ widely in
property are kept in the same group
5. There are no separate positions for isotopes. Isotopes are the elements having
same number protons but different number of neutrons.
6. It is hard to predict the number of missing elements because the change in
mass between two consecutive elements isn’t constant
2.1.3
Modern Periodic Table
Henry Gwyn-Jefferys Moseley in 1991 figured out that an atom’s atomic number is
a more fundamental property of an element as the atomic number equals the number of protons and electrons within an atom. The modern table is based upon the
new and improved, modern periodic law which states: ”The chemical and physical
property of the elements is the periodic function of their atomic number.” Due to
that, the elements are arranged based on their increasing atomic number.
Characteristics of the Modern Periodic Table
1. Elements are arranged based upon their increasing atomic number
2. There are 18 groups (vertical columns) and 7 periods (horizontal rows) in the
modern periodic table where, period 1: very short (2 elements), period 2 and
3 short: short (8 elements each), period 4 and 5: long (18 elements each); and
lastly period 6 and 7: very long (32 elements each)
3. Metals are kept in the left, non-metals in the right, and metalloid are kept
between them
4. Noble gases (inert elements) are kept on the rightmost group (18th Group or
0 Group)
5. Lathanides and actinides are kept separately as f block elements
Advantages of the Modern Periodic Table
1. The position of hydrogen is almost solved. It is kept in s-block and group
IA because its last electron entered the s-sub shell, has a similar electronic
configuration to the elements of group IA and it having similar properties to
group IA elements.
50
2. There are separate places for noble gases (inert elements), lathanides and
actinides
3. Chemically dissimilar elements are kept in separate groups
4. It separates non-metals from metals
5. there are suitable places for isotopes
Disadvantages of the Modern Periodic Table
1. The position of hydrogen isn’t fully solved
2. Lathanides and actinides are kept separately
Differences between modern periodic table and Mendeleev’s periodic table
SN
1
2
3
4
2.1.4
Modern Periodic Table
SN
Elements are arranged on 1
the basis of their increasing
atomic number
There is suitable place for 2
isotopes
There are 7 periods and 18 3
groups
Similar elements are kept in 4
the same group
Mendeleev’s Periodic Table
Elements are arranged on
the basis of their increasing
atomic mass/weight
There isn’t suitable place
for isotopes
There are 7 periods and 8
groups
Similar elements are not always kept together in the
same group
Groups and Periods
In a period, groups are the vertical columns whilst the horizontal rows are called
periods. Each groups hold chemically similar elements whilst each period holds elements of increasing atomic number and valence electron.
Characteristics of Period
1. The atomic number and the number of valence electrons increases as we go
from left to right in a period
2. The valency first increases from 1 to 4 and then decreases from 4 to 0 as we
go from left to right in a period
3. The chemical reactivity of metals decreases as we go from left to right but the
chemical reactivity of non-metals keeps on increasing in a period
4. The electropositivity of metals decrease and the electronegativity of nonmetals increases as we go from left to right in a period
51
Characteristics of Group
1. The atomic number and the number of valence electrons remains the same as
we go from top to bottom
2. The valency remains goign from top to bottom
3. The chemical reactivity of metals increases as we go from top to bottom but
the chemical reactivity of non-metals keeps on decreasing as we go top to
bottom
4. The electropositivity of metals increases and the electronegativity of nonmetals decreases as we go from top to bottom in a group
2.1.5
Valency
The combining capacity of an atom or radical is called its valency. Valency is determined by the number of valence electrons. Electrons whose orbits lie on the
outermost shell of an atom (which is also known as the valence shell) are known as
valence electron. The amount of valence electrons also determines the character of
an element, i.e., if its a metal, non-metal, or metalloid; and the group alongside the
atom’s valency.
If the V E (valence electron) is less than 4, then:
Valency = V E
Else,:
Valency = 8 − V E
2.1.6
Electronegativity and Electropositivity
Electronegativity is the tendency of an element to form negative ions by gaining
electrons whilst electropositivity is the tendency of an element to form positive ions
by losing electrons.
Ionization energy is the minimum energy required to remove the most loosely
bound electron from an atom.
2.1.7
Block and Groups
Blocks
Elements are divided into blocks depending on which sub-shell the last electron
filled. They are: s block, p block, d block, and f block.
d block elements, elements whose last electron enter d sub-shell, are also known
as transition elements. They lie between s block (IIA or 2nd group) and p block
(IIIA or 13th group) and have an incomplete d sub-shell.
52
f block elements are known as lathanides and actinides also can be called inner
transition elements. Lanthanides and actinides are the group of elements after lanthanum and actinium respectively. They have their valence electrons in f-orbital.
Groups
There are 18 groups in the periodic table.
The elements of 1st group or group IA, with the exception of hydrogen, are
called alkali metals as when they react with water they form their respective alkali.
Examples include: Lithium (L), Potassium (K), Sodium (Na), etc.
The elements of 2nd group or group IIA are known as alkali earth metals as
they’re common in the earth’s crust and they form their respective alkali when they
reach with water. Examples include: calcium (Ca), beryllium (Be), magnesium
(Mg), etc.
Group VIIA elements are known as halogens as they form salts after combining
with metals. Examples include, Fluorine (F), chlorine (Cl), bromine (Br), iodine
(I), etc.
2.1.8
Electronic Configuration
The systematic arrangement of electrons into different shells in an atom is called
electronic configuration. The division of a shell of electron is called sub-shell or
orbital.
Bohr Bury’s formula i.e, 2n2 isn’t capable of fully explaining the electronic configuration of every element as such, Aufbau’s principle was introduced to solve the
problem.
According to Aubfau’s principle, the electrons of an atom fill different sub-shells
or orbitals labelled as s, p, d, and f which can store 2, 6, 10, and 14 electrons respectively. Electrons fill each of the following sub-shell starting from the lowest energy
level to the highest level. Note: d4 and d5 do not exist due to half-spin rule
Aufbau’s principal
1s
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
7s
53
2.1.9
Chemical Reactivity
The tendency of an atom to take in part in a chemical reaction is called chemical
reactivity. The higher the chemical reactivity of an atom, the more reactive it is.
Chemical reactive is based upon how quick it tends to lose or gain electrons. The
gaining or losing tendency (electronegativity and electropositivity) is based upon
the size and nature of the atom.
Chemical Reactivity of Metals
Metals are categorized by their electropositivity (i.e., their tendency to form positive
ions by losing electrons), as such metals which loses their electrons faster are more
reactive than those that don’t. The electropositivity is determined by the
size of
the atom, as the greater the atomic size, lower the atomic force F ∝ R12 .
Metal’s electropositivity increase as we go from top to bottom in a group but
decreases when we from left to right in a period (as more valence electron increases
the nuclear force of attraction, hence making the atoms smaller in size). [Hydrogen
and Boron aren’t metals]
Chemical Reactivity of Non-metals
Unlike metals, non-metals are categorized by their tendency to form covalent bonds,
i.e, their electron gaining tendency. Therefore, the greater the electronegativity of a
non-metal, the greater their reactivity. This means, that non-metal get more reactive
as their atomic size gets smaller and the greater their nuclear force of attraction.
This means that in a particular group of non-metals, their reactivity gets lower
as we go from top to down as atomic size increases as we go from top to bottom in a
group (hence, lower nuclear force of attraction) and that it increases in a particular
period as the atomic size of an atom increases as we go from left to right in a period.
54
2.2
Chemical Reaction
A chemical reaction is a reaction which causes chemical change to occur in the
substances. There are 2 types of changes which takes place in matter: physical and
chemical change.
Physical change is a temporary change which doesn’t create new substances. It
is reversible and only changes the physical state of the substances. Chemical change,
on the other hand, is a permanent change in which new substances are formed. It
is irreversible in nature and changes both the physical and chemical nature of the
substance.
2.2.1
Chemical Reaction
Chemical reaction is defined as a chemical change that takes place by addition,
decomposition, or displacement of atoms or molecules of the matter. It involves
reactants and products.
Reactants are the substances which undergo a chemical change during the reaction whilst the products are the end result of the reaction. Reactants are written
on the left hand side and products on the right hand side of a chemical equation.
2.2.2
Chemical Equation
The symbolic representation of an actual chemical reaction in terms of symbol and
molecular formula is called chemical equation.
Essentials of Chemical Equation
All chemical equations must satisfy these conditions:
1. It must represent an actual chemical reaction.
2. It must be balanced.
Limitation of a chemical equation
1. It does not tell us about the condition such as temperature, pressure, light, or
catalyst
2. It does not tell us about the physical state of the reactants and product
3. It does not tell whether heat is absorbed or evolved in the reaction
2.2.3
Types of Chemical Reactions
There are four types of chemical reaction:
1. Decomposition Reaction
2. Combination Reaction
55
3. Displacement Reaction
4. Acid-Base Reaction
Combination or Synthesis Reaction
The chemical reaction in which two or more reactants combine together to form a
single product is called combination/addition/synthetic reaction. The product is
more complex.
A + B −→ AB
2N a + Cl2 −→ 2N aCl
4F e + 3O2 −→ 2F e2 O3
Decomposition or Analysis Reaction
The chemical reaction in which a reactant decomposes to give two or more products
is called decomposition reaction. The product is simpler.
AB −→ A + B
CaCO3 −→ CaO + CO2
2KClO3 −→ 2KCl + 3O2
Displacement Reaction
The chemical reaction in which an atom or radical in a molecule is replaced by
another atom or radical to form new product is called displacement reaction. There
are two types of displacement reaction. They are:
1. Single displacement Reaction
2. Double displacement Reaction
Single Displacement Reaction
The chemical reaction in which an atom in a molecule is replaced by another atom
is called single displacement reaction. An example of this reaction is the reaction
between a metal and acid which produces salt and hydrogen.
A + BC −→ AC + B
Ca + H2 SO4 −→ CaSO4 + H2
Double Displacement Reaction
The chemical reaction in which the atom or molecule of the reactants are exchanged
to form new substances is called double displacement reaction.
AB + CD −→ AD + CB
N aCl + AgN O3 −→ N aN O3 + AgCl
Acid-Base Reaction
The chemical reaction in which acid combines with base to form salt and water is
56
called acid-base reaction. It is also called neutralization reaction as the acid loses
its acidity and the base loses it basicity and forms a neutral substance.
Acid + Base −→ Salt + W ater
HCl + N aOH −→ N aCl + H2 O
H2 SO4 + F eO −→ F eSO4 + H2 O
2.2.4
Rate of Chemical Reaction
The change in the concentration of reactants to form product per unit time is called
rate of chemical reaction.
Five factors that affect the rate of chemical reaction are:
1. Temperature
2. Pressure
3. Light
4. Surface Area
5. Catalyst
Effects of temperature in the rate of chemical reaction
Temperature increases the rate of chemical reaction as it increases the average kinetic energy of the molecules and thus the rate of collision between the reactants
increase. This increases the rate of reaction.
Experiment to show the effect of temperature in the rate of chemical
reaction
Materials Required
Oxalic acid, sulfuric acid, water, potassium permagnet (KM nO4 ), two beakers, glass
rod, spirit lamp, match sticks
Procedure
Put few oxalic acid crystals in two different beakers. Put about 10ml dilute sulfuric
acid in each beaker. Put about 5ml potassium permagnet solution in each and them
stir the substances with the help of a glass rod for an instant. The solution in both
the beakers turn in pink color. Now, heat one beaker to about 60◦ C − 80◦ C with
the help of crystal lamp.
Observation
The pink color disappears quickly from the hot beaker. The pink color disappears
after a long time for the cold beaker
Conclusion
57
The rate of chemical reaction increases with the increase of temperature.
Effects of pressure in the rate of chemical reaction
The rate of chemical reaction increases with the increase of temperature.
200atm
N2 + 3H2 −−−◦−→ 2N H3
500 C
Effect of light in the rate of chemical reaction
Green plants require sunlight (solar energy) to prepare their food n the presence of
water and carbon dioxide.
6CO2 + 6H2 O −→ C6 H12 O6 + 6O2
There are some reaction in which a certain substance decomposes through the interaction with the photons of light, such reactions are called photo decomposition
reaction an an example of the reaction is:
light
2AgCl −→ 2Ag + Cl2
Effect of surface area in the rate of chemical reaction
The chance of collision is greater when there is more surface area between the reactants. This increases the rate of chemical reaction and vice versa.
Experiment to show that the surface area affects the rate of chemical
reaction
Materials Required
Two beakers, water, glass rod, top pan balance, spoon, measuring cylinder, two
watch glasses
Chemicals Required
Zinc powder, zinc pieces, dilute hydrochloric acid
Procedure
Put 20/20ml dilute hydrochloric acid in two beakers. Measure 2gm zinc powder
and 2gm zinc pieces separately using top pan balance and then keep them in two
different watch glasses. Now put zinc powder in one of the beaker and zinc pieces
in another beaker.
Observation
The gas is evolved in faster in the beaker containing zinc powder
Conclusion
The rate of chemical reaction increases with the increase of surface area of the reactant.
58
2.2.5
Catalyst
The chemical substance which alters the rate of chemical reaction without undergoing any chemical change is called a catalyst. There are two types of catalyst:
1. Positive Catalyst: Increases the rate of reaction, example: Manganese dioxide
(M nO2 ) for the decomposition of potassium chlorate and iron for the manufacture of ammonia.
M nO
2
2KClO3 −−−−−−−
−→ 2KCl + O2
F e/M d
3H2 + N2 −−−
−−−−−→ 3N H3
◦
500 C, 250atm
2. Negative Catalyst: The catalyst which decreases the rate of chemical reaction
is known as negative catalyst. Glycerin (C3 H5 (OH)3 ) acts as a negative catalyst in the decomposition of hydrogen peroxide and gypsum acts as a negative
catalyst in cement.
Characteristics of Catalyst
1. The mass and chemical properties of the catalyst remains same before and
after the reaction
2. It alters the rate of chemical reaction
3. It does not initiate the rate of chemical reaction
2.2.6
Endothermic and Exothermic Reaction
The chemical reaction in which is heat is absorbed is called endothermic whilst the
chemical reaction in which heat is produced is called exothermic reaction.
59
2.3
Acid, Base, and Salt
2.3.1
Acid
Acid is derived from the Latin word acidus which means sour. Acid is defined as
any substances which gives H+ ion when it dissolves in water. It is sour in taste
because it gives hydronium (H3 O+ ) ion after dissolving in water.
Ionization of some acids:
HCl −→ H + + Cl−
H2 SO4 −→ 2H + + SO4−−
CH3 COOH −→ H + + CH3 OO−
H2 CO3 −→ 2H + + CO3−−
Types of Acid
There are two types of acid on the basis of source:
1. Organic Acid : Acid found and obtained from plants is called organic acid. It
is weak in nature. Examples: citric acid (found in lemon and orange), malic
acid (found in apple), tartaric acid (found in grape fruit and bhogote), lactic
acid (found in milk), acetic acid (found in vinegar), ascorbic acid (found in
vitamin C), etc.
2. Inorganic Acid : Acid which is obtained from minerals and prepared in laboratory is called inorganic acid. They’re strong in nature. Examples: HCL,
H2 SO4 , HN O3 , etc.
Now, based upon the strength of acid, there are two types of acid:
1. Strong Acid : The acid which gives more hydrogen ion after dissolving in water
is called strong acid. They dissociate almost completely. Example: HCL,
H2 SO4 , HN O3 , etc.
2. weak Acid : The acid which gives less hydrogen ion after dissolving in water
is called weak acid. It partially dissociates into ions. Examples: H2 SO3 ,
HCOOH, CH3 COOH, etc.
SN
1
Weak Acid
A weak base less ions after
dissolving in water
SN
1
2
3
They are less reactive
They conduct electricity
worse
They partially disassociate
into ions
2
3
4
4
60
Strong Acid
A strong acid gives more
ions after dissolving in water
They are more reactive
They conduct electricity
better
The completely disassociate
into ions
2.3.2
Physical Properties of Acid
1. It is sour in taste
2. It is corrosive in nature
3. it is a good conductor of electricity
4. It turns blue litmus paper red, methyl orange into red, and phenolphthalein
into a colorless liquid.
2.3.3
Chemical Properties of Acid
1. Acid reacts with metal to give metallic salt and hydrogen
2. Acid reacts with base to give salt and water
3. Acid reacts with metal carbonates to give salt, water, and carbon dioxide
4. Acid reacts with metal bicarbonates to give salt, water, and carbon dioxide
2.3.4
Uses of Acid
1. HCl is used as a lab reagent, for bleaching purposes in textiles etc.
2. Sulphuric acid is used as lab reagent, for making chemical fertilizer, detergent,
etc.
3. Nitric acid is used as lab reagent, for making chemical fertilizer, explosives,
etc.
4. Carbonic acid is used to prepare cold drinks
5. Boric acid is used for washing eyes and wounds
6. Acetic acid is used to give the sourness to vinegar
7. Citric acid is consumed as a source of vitamin C
8. Tartaric acid is used in baking powder
2.3.5
Base
Metallic oxides and hydroxides are called bases. The water soluble bases are called
alkali. All alkali are bases but not all bases are alkali. As all alkali dissolve in water
but not all bases dissolve in water. Also, alkali give OH − or O− ions.
61
2.3.6
Types of bases
There are two types of bases:
1. Strong Base: The base which give more OH − or O− ions after dissolving
in water is called strong base (alkali). Example: N aOH, KOH, M g(OH)2 ,
Ca(OH)2 , etc.
2. Weak Base: The base which give less OH − or O− ions after dissolving in water
is known as a weak base. Example: N H4 OH, F e(OH)3 , Cu(OH)2 .
SN
1
Weak Base
A weak base give less ions
after dissolving in water
SN
1
2
3
They are less reactive
They conduct electricity
worse
They partially disassociate
into ions
2
3
4
2.3.7
4
Strong Base
A strong base gives more
ions after dissolving in water
They are more reactive
They conduct electricity
better
The completely disassociate
into ions
Physical Properties of bases
1. They are bitter in taste
2. It is soapy in touch
3. Strong base is good conductor of electricity
4. They turn red litmus paper into blue, methyl orange into yellow, and phenolphthalein into pink color.
2.3.8
Chemical Properties of Bases
1. Base reacts with acid to give salt and water
2. Base react with carbon dioxide to give carbonate salt and water
3. Alkali reacts with ammonium salts on heating to give ammonia gas
4. Insoluble hydroxide are reduced from alkali by some salts
2.3.9
Use of Base
1. Causatic soda (N aOH) is used for manufacture of soap, detergent, paper,
rayon, etc.
2. Causatic potash (KOH) is used for the preparation of soft soaps.
3. M g(OH)2 and Al(OH)3 are used for the preparation of soft soaps
62
4. Lime water or slaked lime (Ca(OH)2 ) is used as lab reagent to prepare ammonia gas as well as bleaching powder.
5. Ammonium hydroxide is used as lab reagent as well as producing chemical
fertilizer
6. Quick lime (CaO) is used for the manufacture of cement as well as the softening
of hard water.
2.3.10
Salts
Salts are substances formed by the reaction between an acid and base with all or
part of the hydrogen or hydroxide of the acid or base respectively being replaced.
There are three types of salts:
1. Neutral Salt: The salt which is produced by the reaction of strong acid and
strong base or weak acid and weak base is known as neutral salt. It is formed
by the complete replacement of H + ion from an acid or OH − ion from a base.
E.g: N aCl, CaSO4 , K2 SO4 , etc.
2. Acid Salt: The salt formed by the partial replacement of hydrogen ion from
an acid is called acidic salt. It is formed by the reaction of strong acid and
weak base. Example: N aHSO4 , N H4 Cl, etc.
3. Basic Salt: The salt formed by the partial replacement of hydroxide ions from
a base is called a basic salt. It is formed by the reaction of strong base and
weak acid. E.g: N a2 CO3 , CH3 COON a, etc.
2.3.11
Acid and Basic Radical
Radicals derived from an acid in a salt is called acidic or non-metallic radical, e.g.
Cl− , SO4−− , etc. On the other hand, radicals derived from a base in a salt is called
basic or metallic radical, e.g: N a+ , M g ++ , etc.
2.3.12
Hydrated Salt
The salt which contains a fixed amount of water molecule in it is known as a hydrated
salt. Example: N aCO3 · 10H2 O, CuSO4 · 5H2 O, CaSO4 · 2H2 O, etc.
2.3.13
Physical Characteristics of Salts
1. Some salts are tasteless whereas most of them are bitter but N aCl is salty in
taste
2. Most of the salts are soluble in water and they get electrolised in solution form
except lead chloride, silver chloride, lead sulphate, and barium sulphate
63
3. Salts of N a, N H4 , and K are solube in water. All bicarbonates and nitrates
are soluble in water. All chloride except silver chloride and P dCl2 are soluble
in water. All sulphates except P dSO4 and BaSO4 are soluble in water.
4. Salts of sodium, magnesium, aluminum, potassium, calcium, and barium are
colorless whilst the salt of cobalt, nickel, iron, manganese, copper, etc. are
colorful.
2.3.14
Preparation of Salt
1. By the direct combination of metals and non-metals
2. By action of acid on some metals
3. By the reaction of acid and base
2.3.15
Uses of Salts
1. N aCl is used as edible salt
2. N aCO3 · 10H2 O is used for the preparation of glass, soap, and detergent
3. AgN O3 is used as lab reagent for silver plating
4. CuSO4 · 5H2 O is used as lab reagent as fumigate to preserve food and copper
plating
5. CaSO4 · 2H2 O is used in chalk, cement, etc. It is also called gypsum or blue
vitriol.
6. N H4 Cl is used in electrolyte in dry cell
7. (N H4 )2 SO4 is used as chemical fertilizer.
8. Sodium bisulphate N aHCO3 is used in backing powder
2.3.16
Neutralization Reaction
The reaction in which acid reacts with base and neutralize each other to form salt
and water is called neutralization reaction. Its applications are:
1. To control pH of soil by using base such as quick lime to remove the acidity
of the soil
2. To manufacture antacid to reduce hyperacidity in our stomach
3. To cure bee or ant stings by using baking soda or soap
4. To cure was sting by using vinegar
64
2.4
2.4.1
Some Gases
Carbon Dioxide
Carbon dioxide is a compound gas having the molecular formula CO2 −thus making
it compound formed through the valence bond between one carbon atom and two
oxygen atoms. Thus, its molecular weight is 44amu.
Carbon dioxide gas was discovered by Van Helmont in 1630AD by burning
wood. In 1755AD, Joseph Black prepared the gas by burning magnesium carbonate (M gCO2 ). Similarly, in 1783AD, Lavoisier proved that carbon dioxide is the
compound made of carbon and oxygen.
Carbon dioxide is found in both combined and free state as:
1. Carbon dioxide occupies 0.03% of the atmosphere by volume
2. All forms of plants and animals release carbon dioxide gases
3. As the gas is soluble in water, some of it is dissolved in bodies of water
4. Burning of carbon-based compounds (wood, coal, etc.) CO2 is released into
the atmosphere as the byproduct of the process
5. It is found within carbonates such as calcium carbonate, magnesite, etc.
Laboratory Preparation of Carbon Dioxide Gas
Principle
In laboratory, carbon dioxide gas is prepared by the chemical reaction between pieces
65
of marble or limestone CaCO3 , with dilute hydrochloric acid HCl.
CaCO3 + 2HCl −→ CaCl2 + H2 O + CO2
(dil.)
Materials Required
Wouldfe’s bottle, thistle funnel, corks, delivery tube, gas jar, pieces of limestone or
marble and dilute hydrochloric acid
Procedure
Pieces of limestone were kept within the woulfe’s bottle. Then the apparatus was
set such that the thistle funnel and the delivery tube were fitted in one of each cork.
Through the thistle funnel, HCl was poured.
Observation
After the chemicals were poured, the reaction started quickly. the gas was collected
through the delivery tube which poured it in within the gas jar. The gas was captured through upward displacement of air as carbon dioxide is heavier than air.
Conclusion
Thus the reaction produced carbon dioxide gases.
Precaution
1. The apparatus must be made air tight
2. Carbon dioxide gas must be collected through the upward displacement of air
3. The lower end of the thistle funnel must be immersed in the acid
Test for Carbon Dioxide Gas
To test if the gas produced is carbon dioxide or not, we can do the following steps:
1. As carbon dioxide is neither a supporter of combustion nor a gas which combusts, a piece of flame near to it gets extinguished
2. Carbon dioxide dissolves in water to form carbonic acid H2 CO3 which results
in moist blue litmus paper being turned red
3. Still, the best test to check for carbon dioxide is to pass it through lime water
as the carbon dioxide reacts with the calcium hydroxide to form insoluble
(water) calcium carbonate
CO2 + Ca(OH)2 −→
CaCO3
Water Insoluble
+ H2 O
Industrial Preparation of carbon dioxide gas
For large volume of carbon dioxide, the gas is prepared by heating limestone or
calcium carbonate in a kiln.
∆
CaCO3 −−→ CaO + CO2 ↑
66
Limestone, Quick Lime, and Slaked Lime
Limestone is a type of stone naturally found in the earth’s crust. Chemically, it is
known as calcium carbonate CaCO3 .
When calcium carbonate is heated, it splits into calcium oxide CaO and carbon
dioxide CO2 . Calcium oxide is also known as quick lime. It reacts with water in an
exothermic reaction to produce calcium hydroxide a water soluble substance. It is
also known as slaked lime.
CaO + H2 O −→ Ca(OH)2
Methods of Carbon Dioxide Production
1. Carbon dioxide is prepared by burning carbon in sufficient oxygen (carbon
forms carbon monoxide when there isn’t enough oxygen)
2. When hydrocarbons are burned in oxygen, the release carbon dioxide and
water
3. Carbon by heating calcium carbonate
4. Carbon dioxide is prepared by the reaction of carbonates and bicarbonates
with acids
Physical Properties of Carbon Dioxide
1. Carbon dioxide is colorless and odorless gas
2. It is slightly acidic in taste as it forms carbonic acid when it dissolves in water
3. It is about 1.5 times heavier than air
4. It turns moist blue litmus paper into red (it dissolves in water to form an acid)
5. It freezes when cooled down to -78◦ C, which is commonly known as dry ice
6. It does not support combustion and thus is used to extinguish burning objects
7. Though being a non-poisonous gas, it is harmful when it is present in greater
amount
Chemical Properties of Carbon Dioxide
1. Carbon dioxide reacts with metallic oxides and hydroxides to give carbonates
and bicarbonate plus water respectively.
N a2 O + CO2 −→ N a2 CO3
Ca(OH)2 + CO2 −→ CaCO3 + H2 O
2. Carbon dioxide dissolves in water to form carbonic acid which is used in cold
drinks to give them a sour taste
CO2 + H2 O −→ H2 CO3
67
3. Though being neither a supporter of combustion or a combustible substance,
it reacts with burning magnesium and forms white solid powder and carbon.
4. Carbon dioxide reacts with the solution of lime water and makes white precipitate (CaCO3 ). When it is passed through for a longer time, the milky color
disappears as the CaCO3 , carbon dioxide, and water reacts to form calcium
bicarbonate Ca(HCO3 )2
Ca(OH)2 + CO2 −→ CaCO3 + H2 O
CaCO3 + H2 O + CO2 −→ Ca(HCO3 )2
5. Green plants use carbon dioxide to prepare food in leaves in the presence of
the sunlight in the process called photosynthesis.
sunlight
6CO2 + 6H2 O −−−−−−→ C6 H12 O6 + 6O2
chlorophyll
6. Carbon Dioxide reacts with hot coke at about 900◦ C and forms carbon monoxide
900◦ C
CO2 + C −→ 2CO
Uses of Carbon Dioxide
1. Carbon dioxide is used in cold drinks
2. Green plants use carbon dioxide for photosynthesis
3. It is used for the manufacturing of urea N H2 CON H2 and sodium carbonate
N aCO3 · 10H2 O
4. It helps to form carbogen (a mixture of 95% oxygen and 5% carbon dioxide)
which is used to stimulate breathing to treat pneumonic patients
5. It is used to extinguish fire as it is used in fire extinguisher
Fire Extinguisher
In a fire extinguisher, sodium bicarbonate or sodium carbonate and concentrated
sulphuric acid are kept separately. They’re separated into two different glass containers. When in emergency, the handle is pressed which breaks the division of the
two containers, mixing the chemicals and thus producing large amount of CO2 gas.
2N aHCO3 + H2 SO4 −→ N a2 SO4 + 2H2 O + 2CO2
N a2 CO3 + H2 SO4 −→ N aSO4 + H2 O + CO2
68
2.4.2
Ammonia
Ammonia is a compound gas having molecular formula N H3 meaning it is a molecule
formed by the covalent bond of one nitrogen atom and three hydrogen atom. Thus,
its atomic weight is 17amu.
Ammonia gas was discovered by Lavoisier by heating the mixture of ammonium
chloride N H2 Cl and calcium hydroxide Ca(OH)2 . The composition of ammonia
gas was discovered by Davy and Berthecol.
Ammonia gas is found in nature in free as well as in combined form, they’re:
1. Slight amounts of ammonia is found within the air and soil in free state
2. It is formed when nitrogenous compound decay in the absence of air (oxygen)
3. It is found in forms of ammonium salts, ammonium nitrate, ammonium sulphate, etc.
Laboratory Preparation of Ammonia Gas
Principle
In a laboratory, ammonia gas is prepared by heating two parts of ammonium chloride
N H4 Cl and one part of calcium hydroxide Ca(OH)2
2N H4 Cl + Ca(OH)2 −→ CaCl2 + 2H2 O + 2N H3
Materials Required
Hard glass test tube, bunsen burner, stand, cork, delivery tower, lime tower, gas jar,
match box, ammonium chloride, and calcium hydroxide
Procedure
The mixture of ammonium chloride and calcium hydroxide is kept within the hard
glass test tube. Then, the stands were kept side by side with one of the stands
clamping down upon the test tube (which is tilted downwards to avoid breakage
due to water vapor formed in the reaction). The test tube is heated by a burning
bunsen burner and then through a delivery tube the gas is passed to the lime tower
which leads to to the gas jar which is held down by the other stand.
Observation
The mixture reacts with itself and forms water, calcium chloride, and ammonia gas.
The moist gases passes through the lime tower to lose the moisture (CaO absorbs
the water) and then is stored within the gas jar by the downward displacement of air.
Precautions
1. The apparatus must be made air tight
2. The gas must be collected in the gas jar through downward displacement of
air as ammonia is lighter than air
69
3. The hard test should be kept in inclined position facing the mouth of the
test tube downward to prevent if from cracking due to evaporation of water
produced during the chemical reaction
4. Ammonia gas should be passed through a lime to get dry ammonia as the
calcium oxide absorbs the water
Test of Ammonia Gas
To check that ammonia gas is actually produced the following checks can be done:
1. When a moist red litmus paper is inserted in the gas jar containing ammonia,
the litmust turns into blue as ammonia is basic in nature
N H3 + H2 O −→ N H4 OH
2. It can be identified by the pungent smell which it produces
3. White fumes of ammonium chloride are formed when a glass rod dipped in
concentrated hydrochloric acid is kept in the gas jar containing ammonia gas
Manufacture of Ammonia gas
In large an industrial scale, ammonia gas is prepared by heating on part nitrogen
gas with three part parts hydrogen gas under high temperature and pressure. This
process is called Haber’s process.
500◦ C,F e/M o
N2 + 3H2 −−−−−−−−→ 2N H2 + Heat
200−900atm
The process is reversible thus it is a very slow reaction. It needs the following
conditions to further increase the rate of the reaction:
Temperature = around 500◦ C
Pressure = 200 - 900 atm
Catalyst = Iron (Fe)
Promoter = Molybdenum (Mo)−Promoter is a substance which enhances the
function of the catalyst
This process was discovered by the German Chemist Fritz Harber, thus is called
Harber’s Process
Physical Properties of Ammonia Gas
1. It is a colorless gas
2. It possess strong pungent smell which may produce tear in the eyes
3. It is highly soluble in water
70
4. It turns moist red litmus paper into blue as it is basic in nature
5. It neither burns nor supports combustion
6. It solidifies -78◦ C and liquifies at -33.4◦ C
Chemical Properties of Ammonia Gas
1. Ammonia gas is highly soluble and forms ammonium hydroxide when it dissolves
2. Ammonia reacts with acids and produces salts
3. Ammonia reacts with hydrochloric acid and forms ammonium chloride
4. Ammonia reacts with oxygen and forms greenish yellow flame wihich contains
nitrogen and water
4N H3 + 3O2 −→ 6H2 O + 2N2
5. Ammonia reacts with carbon dioxide to form urea and water
150atm
2N H3 + CO2 −−−◦−→ N H2 CON H2 + H2 O
200 C
6. Ammonium solution (ammonia hydroxide) reacts with acid and forms salt and
water (acid-base reaction)
7. Ammonium carbonate decomposes into ammonia, carbon dioxide, and water
when it is heated
∆
(N H4 )2 CO3 −→ N H3 + CO2 + H2 O
Use of Ammonia Gas
1. Liquid ammonia is used in refrigerator as a cooling agent
2. It is used for manufacturing nitric acid, plastic, washing soda, alkalis, etc.
3. It is used as a cleansing agent to remove oil, grease etc.
4. It is used to develop blue prints of maps
5. It is used for making chemical fertilizers like urea, ammonium sulphate, ammonium chloride, ammonium nitrate, etc.
6. It is used for manufacturing ammonium salts like N H4 Cl, (N H4 )2 SO4 , etc.
that are used in medicines
7. It is used for making dyes, rayon, nylon, explosives, etc.
8. It is used in cold stores for cooling purposes
71
9. It is used in water and waste treatment such as pH control
10. It used in rubber, leather, and paper industries
11. It is used as a source of nitrogen for yeast and microorganisms in food and
beverage industries
72
2.5
Metals
Among the 118 elements discovered so far, 95 are metals. Metals can be defined as
the elements that form electropositive ions (except hydrogen) and conduct heat and
electricity. The properties of metals are:
1. They are malleable and ductile
2. They are good conductors of electricity
3. They form electropositive ions
4. They are shiny (lustrous)
2.5.1
Iron
Iron is an abundant metal found in the earth’s crust. In Latin, iron is called ferrum
thus its symbol is F e. Its atomic number is 26 and it weights 56amu.
The electronic configuration of iron is:
Shell
No. of electrons
Orbital
K
2
1s2
L
8
2
2s 2p6
M
14
2
3s 3p6 3d6
N
2
4s2
Position of iron in Modern Periodic Table
Iron belongs to d-block, group 8 and 4th period of the modern period table. The
valency of iron is 2 or 3.
It is placed in d-block as the last electron of iron filled the 3d orbital. Hence it
is known as a transitional metal and has properties differing from normal elements.
Iron forms ferrous ion F e++ by losing two electrons and ferric ion F e+++ by
losing three electrons.
Occurrence of Ores of Iron
Iron isn’t found commonly in its free state due to its reactivity.
1. Iron is found in the form most commonly in the form of its ores
2. Extremely little amount of iron is found in the blood in the form of haemoglobin
Main ores of iron are:
1. Haematite F e2 O3
2. Magnetite F e3 O4
3. Limonite F e2 O3 · 3H2 O
4. Iron Pyrite F eS2
5. Siderite F eCO3
73
Hamatite is the most common as it is 72.5% iron and extremely abundant.
Physical Properties of Iron
1. Pure iron is an ash colored gray white metal
2. It is a good conductor of heat and electricity
3. It is malleable and ductile
4. Its specific gravity is 7.86
5. Iron melts at 1500◦ C and boils at 2500◦ C
6. Iron loses its magnetic properties when heated above 770◦ C
Uses of Iron
1. It is used for manufacturing building materials like rods, pipes, wires, and
machinery parts
2. It is used for making parts of vehicles, railway tracks, etc.
3. It is used for making nails, nuts and bolts are household utensils
4. It is for making cooking utensils and agricultural tools
5. It is used for making weapons and different type of tools
6. It is used to various chemical reaction as a catalyst
7. It is used to manufacture steel
2.5.2
Aluminum
Aluminum is an abundant metal found in the earth’s crust. Its atomic symbol is Al.
Its atomic number is 13 and it weighs 27amu. Its electronic configuration is:
Shell
No. of electrons
Orbital
K
2
1s2
L
8
2
2s 2p6
M
3
2
3s 3p1
The outer most shell of aluminum consists of three electrons thus it is kept in group
13 of the modern periodic table. It is kept in p-block and 3rd period of the periodic
table. Aluminum loses three electrons from its valence shell thus forming aluminum
ion Al+++ thus having a valency of 3.
Occurrence and ores of aluminum
Aluminum is a highly reactive nature, thus its free state is uncommon in nature.
Its main ores are:
74
1. Bauxite Al2 O3 · 2H2 O
2. Feldspar KAlSi3 O8
3. Cryolite N a3 AlF6
4. Kaolin Ali2 Si2 O7 · H2 O
Bauxite is the principal ore, thus the metal is typically extracted from this ore
Physical Properties of Aluminum
1. It is a shiny and silver-white colored metal
2. It is a good conductor heat and electricity
3. It is highly malleable and ductile
4. Its specific gravity is 2.7
5. It is highly resistant to corrosion
6. It melts at about 660◦ C and boils at about 1800 ◦ C
7. It is very light and strong metal
Uses of Aluminum
1. It is used for making cooking utensils due to its light weight and rust free
nature
2. It is used for making bodies and parts of aeroplanes, ship, car, motorcycles,
etc.
3. It is used for making electric wires, photo frames, etc.
4. It is used for making materials for construction like windows, doors, roofs, etc.
5. It is used for making silver paint by mixing its powder with oil
6. It is used for making aluminum foil for packaging medicines, chocolates, packaging foods, etc.
7. It is used for making coins and alloys
8. It is used for making overhead electric cables
75
2.5.3
Copper
Copper is a reddish brown shiny metal. Its Latin name is cuprum thus its symbol
is CU. Its atomic number is 29 and its atomic weight is 63.57.
Its electronic configuration
Shell
No. of electrons
Orbital
K
2
1s2
L
8
2
2s 2p6
M
18
2
3s 3p6 3d10
N
1
4s1
Copper has one electron in its outermost shell, thus it is placed in group 11 of the
modern periodic table. It belongs to d-block and 4th period of the modern periodic
table. Its valency is 1 or 2. It forms cuprous ion Cu+ by losing one electron cupric
ion Cu++ by losing two electrons from the valence shell.
Occurrence and Ores
Copper is found in pure a swell as in combined state in nature. The main ores are:
1. Copper pyrite or chalcopyrite CuF eS2
2. Chalcocite Cu2 S or copper glance
3. Cuprite Cu2 O
4. Malachite Cu(OH)2 · CuCO3
5. Azurite Cu(OH)2 · 2CuCO3
Copper is generally extracted from copper pyrite or chalcopyrite
Physical Properties of Copper
1. Copper is a shiny reddish - brown metal
2. It is a very good conductor of heat and electricity
3. It is highly malleable and ductile
4. Its specific gravity is 8.95
5. It melts at about 1083◦ C and boils at about 2350◦ C
6. It is soft in nature
Uses of Copper
1. Copper is used for making household utensils
2. It is used for making electric wires, electric motor, dynamo, and other electronic appliances
3. It is used for making steam pipe, vacuum pan and calorimeter
76
4. It is used for electroplating
5. It is used for making coins
6. It is used for making various chemicals, insecticides, germicides, and fungicides
7. It is used in electrotyping
8. It is used for making alloys like brass, bronze, bell metal, etc
Alloys of copper
1. Brass: It is a mixture of copper and zinc, it is used to make nutbolts, medals,
condeser tube and household utensils
2. Bronze: It is the mixture of copper, tin and zinc. It is used for making coins
and household utensils
3. German silver: It is the mixture of copper, zinc, and nickel. It is used for
making bells and household utensils.
4. Bell metal: It is the mixture of copper and tin. It is used for making bells and
decorative metals
5. Gun metal: It is the mixture of copper, tin, zinc, and lead. It is used for
making ball bearings and parts of machines.
2.5.4
Silver
Silver is a shiny white metal its Latin name is Argentum thus its symbol is Ag. Its
atomic number is 47 and its atomic weight is 107.9.
Its electronic configuration:
Shell
No. of electrons
Orbital
K
2
1s2
L
8
2
2s 2p6
M
18
2
3s 3p6 3d10
N
18
2
4s 4p6 4d10
O
1
5s1
The outermost shell of silver consists of only one electron thus it is kept in group
11 of modern periodic table. It is placed in d-block and 5th period modern periodic
table. It forms Ag + by losing one electron from its valence shell (thus having valency
of 1).
Occurrence of Ores of silver
Silver is a less reactive metal thus it is found is free state as well. Its main ores are:
1. Argentite or silver glance Ag2 S
2. Silver copper glance (AgCu2 )2 S
3. Horn Silver AgCl
77
4. Pyrargylite Ag2 Sb2 S3
The principal ore of silver is argentite
Physical Properties of Silver
1. Silver is a shiny white metal
2. It is a very good conductor of heat and electricity
3. It is highly malleable and ductile
4. Its specific gravity is 10.5
5. It melts about 960◦ C and boils at about 1955◦ C
Uses of silver
1. Silver is used for electroplating
2. It is used for making coins, decorative items, idols statues, etc.
3. It is used for making medals and ornaments
4. It is used for shining mirrors
5. It is used for making ornaments and idols
6. It is used for making ornaments and idols
7. It is used for making medicines and silver salts
8. It is used for photography of silver bromide in the negative of a photograph
and x-rays
9. It is used for feeling teeth as silver amalgam
10. Silver is used for making watch, hearing equipment, and battery of calculator
11. It is used for making solar panel
12. It is used in water purifiers to prevent algae and bacteria from growing in the
filters
13. Silver nitrate is used as a laboratory reagent
78
2.5.5
Gold
Gold is a shiny yellow metal, it is a very expensive metal which is used for making
jewelries and medals. Its Latin name is Aurum thus its symbol is Au. The atomic
number of gold is 79 and its atomic weight is 197.2. Its electronic configuration:
Shell
No. of electrons
Orbital
K
2
1s2
L
8
2
2s 2p6
M
18
2
3s 3p6 3d10
N
32
2
6
4s 4p 4d10 4f 14
O
18
2 5
5s 5s 5d10
P
1
6s1
The outermost shell only contains 1 electron so it is located in group 11. Gold belongs to d-block and 6th period. Its valency maybe 1 or 3. Gold forms aurous ion
Au+ by losing one electron and auric ion Au++ by losing three electrons
Occurrence of Gold
Gold is a noble metal thus it is only found in free state in nature. It’s found in:
1. Alluvial soil
2. Suphide oxide, carbonate, sulphate ions, etc.
Physical Properties of Gold
1. Gold is a soft and bright yellow metal
2. It is a very good conductor of heat and electricity
3. It is a noble metal
4. Its specific gravity is 19.3
5. It melts at about 1063◦ C and boils at about 2530◦ C
Uses of Gold
1. It is widely used for jewelries, statues, and other ornaments
2. It is used for making medals and idols of gods
3. It is used for making coins
4. It is for electroplating
5. It is used for photography and dentistry
6. It is used for making anti-inflammatory medicines
7. It is used for making alloys
8. It is used for making gold leaf electroscope
9. It is used for making corrosion resistant electrical connectors in electronic
devices
79
2.5.6
Occurrence of Metals in Nepal
S.N
1.
Metals
Copper
Ores/Sources
Chalcopyrite, Copper Glance
2.
3.
Gold
Iron
Free gold, Sandy alluvial soil
Haematite, Magnetite
4.
Calcium
Limestone
5.
6.
7.
8.
9.
Magnesium
Bismuth
Lead
Zinc
Cobolt
Magnesite
Bismuth
Lead Deposit
Zinc Deposit
Cobaltite
80
Occurrence
Udaypur,
Dhading,
Makwanpur,
Solukhumbu
Rapti, Mustang, Kathmandu
Lalitpur,
Bhojpur,
Ramecchap,
Tanahun, Chitwan, Pyuthan
Makwanpur, Dhading, Udayapur,
Kathmandu
Dolakha, Udaypur
Makwanpur
Lalitpur, Raswa
Lalitpur, Raswa
Gulmi, Palpa
2.6
Hydrocarbons and its Compounds
Every compound in the world can be divided into two categories:
1. Organic Compound: The compounds obtained from living beings which contain hydrocarbons are called organic compounds. All compounds of cabon
except oxide, carbonate, bicarbonate, and carbide are organic compounds.
Example: methane CH4 , propane C3 H3 , alcohol, glycerol, ether, etc.
2. Inorganic Compound: These compounds are obtained from minerals e.g., water H2 O, carbon dioxide CO2 , calcium carbonate CaCO3 , magnesium carbonate M gCO3 , etc.
Hydrocarbons are the compounds which consists of hydrogen and carbon atoms.
These are the most basic organic compounds
Hydrocarbons can be divided into two types on the bases of the bond present
between the carbon atoms.
1. Saturated Hydrocarbon
2. Unsaturated Hydrocarbon
2.6.1
Saturated Hydrocarbon
Hydrocarbons in which all the carbon atoms are joined through a single covalent
bond are called saturated hydrocarbon. Example: ethane, methane, etc.
Due to their stable nature nothing can be added in these compounds so they’re
also called paraffins.
They’re commonly called as alkanes and their general formula is:
Cn H2n+2
Where, n represents the amount of carbon atoms.
Examples of Saturated Hydrocarbons
1. Methane
Molecular Formula: CH4
H
Structural Formula: H
C
H
H
Condensed Formula: CH4
2. Ethane
81
Molecular Formula: C2 H6
Structural Formula: H
H
H
C
C
H
H
H
Condensed Formula: CH3 − CH3
3. Propane
Molecular Formula: C3 H8
Structural Formula: H
H
H
H
C
C
C
H
H
H
H
Condensed Formula: CH3 − CH2 − CH3
4. Butane
Molecular Formula: C4 H10
Structural Formula: H
H
H
H
H
C
C
C
C
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH3
5. Pentane
Molecular Formula: C5 H12
Structural Formula: H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH2 − CH3
6. Hexane
Molecular Formula: C6 H14
82
H
Structural Formula: H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH2 − CH2 − CH3
7. Heptane
Molecular Formula: C7 H16
Structural Formula: H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH2 − CH2 − CH2 − CH3
8. Octane
Molecular Formula: C8 H18
Structural Formula: H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
Condensed Formula: CH3 −CH2 −CH2 −CH2 −CH2 −CH2 −CH2 −CH3
9. Nonane
Molecular Formula: C9 H20
Structural Formula:
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH2 − CH2 − CH2 − CH2 −
CH2 − CH3
10. Decane
Molecular Formula: C10 H22
Structural Formula:
83
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
Condensed Formula: CH3 − CH2 − CH2 − CH2 − CH2 − CH2 − CH2 −
CH2 − CH2 − CH3
2.6.2
Unsaturated Hydrocarbons
The hydrocarbons having a double or triple covalent bond between any two
carbon atoms are called unsaturated hydrocarbons. They become saturated
hydrocarbons when they are given more hydrogen.
There are two types of unsaturated hydrocarbons based upon the type of bond:
(a) Alkenes
(b) Alkynes
Alkenes
The hydrocarbons having a double covalent bond with any two carbon atoms
are known as alkenes.
Alkenes are also called olefins because they produce oil-like substances. They
are more reactive than alkanes and in the presence of sufficient hydrogen they
form alkanes. Their generation formula is:
Cn H2n
Few examples of alkenes are: ethene, propene, and butene.
Examples of Alkenes
(a) Ethene
Molecular Formula: C2 H4
H
H
C
C
Structural Formula: H
Condensed Formula: H2 C = CH2
(b) Propene
Molecular Formula: C3 H6
84
H
H
Structural Formula: H
H
H
H
C
C
C
H
H
Condensed Formula: H2 C = CH − CH3
(c) Butene
Molecular Formula: C4 H8
Structural Formula: H
H
H
H
H
C
C
C
C
H
H
H
Condensed Formula: H2 C = CH − CH2 − CH3
Alkyne
The hydrocarbons having a triple covalent bond with any two carbon atoms are
known as alkyne.
They are more reactive than alkanes and alkenes and in the presence of sufficient
hydrogen they form alkanes. Their generation formula is:
Cn H2n−2
Few examples of alkenes are: ethene, propene, and butene.
Examples of Saturated Hydrocarbons
1. Ethyne or Acetylene
Molecular Formula: C2 H4
Structural Formula: H
C
C
H
Condensed Formula: HC ≡ CH
2. Propyne
Molecular Formula: C3 H6
H
Structural Formula: H
C
C
C
H
Condensed Formula: HC ≡ C − CH3
3. Butyne
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H
Molecular Formula: C4 H8
Structural Formula: H
C
C
H
H
C
C
H
Condensed Formula: HC ≡ C − CH2 − CH3
H
H
Differences between saturated and unsaturated hydrocarbons
S.N Saturated Hydrocarbon
1. The carbon atoms are in a single
covalent bond
2. They are stable compounds
3. They are less reactive
4. Their general formula is Cn H2n+2
2.6.3
S.N
1.
2.
3.
4.
Unsaturated Hydrocarbon
The carbon atoms are either in
double or triple covalent bond.
They are unstable compounds
They are more reactive
Their general formula is either
Cn H2n or Cn H2n−2
Some Common Hydrocarbons
1. Methane
Methane is the simplest aliphatic hydrocarbon. Its molecular formula is CH4 .
It is the smallest and the first member of alkane series.
It is found in marshy places thus it is also called marsh gas. It is formed due
the decomposition of organic matter. It is commonly found above mineral oil.
This is the gas found in gobar gas, biogas, and sewage gas.
The properties of methane:
(a) It is colorless
(b) It is odorless
(c) It is tasteless
(d) It is insoluble in water
(e) It is soluble in organic solvents
Uses of methane:
(a) It is used as a source of heat
(b) It is used to produce carbon black which is used for making color, paint,
shoe polish, ink, etc.
(c) It is used in the manufacture of hydrogen gas
(d) it is used for making chloroform and carbon tetrachloride
86
(e) It is used for making methyl alcohol, formaldehyde, etc.
2. Ethane
Ethane is the alkane having two carbon atoms, it is the second member of the
series. It is found alongside methane in natural gas, coal gas, and petroleum
mines.
The properties of ethane:
(a) It is colorless
(b) It is odorless
(c) It is tasteless
(d) It is insoluble in water
(e) It is soluble in organic solvents
Uses of ethane:
(a) It is used for welding as it produces a lot of heat
(b) It is used as a source of heat (in the form of biogas)
(c) It is used for making shoe polish and diethyl ether
(d) It is used for making ethyl alcohol (ethanol)
3. Propane
It is found in natural gas and petroleum mine.
The properties of propane:
(a) It is colorless
(b) It is odorless
(c) It is tasteless
(d) It is insoluble in water
(e) It is soluble in organic solvents
Uses of propane
(a) It is used for fuel due to its high inflammability
(b) It is used as a cooling agent in the petroleum industry
(c) It is used for making propyl alcohol and other organic compounds
(d) It is used in gas lighters
4. Butane
It is found in natural gas and petroleum mines. The properties of butane:
(a) It is colorless
(b) It is odorless
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(c) It is tasteless
(d) It is insoluble in water
(e) It is soluble in organic solvents
Uses of Butane:
(a) Butane gas is used in LPG (liquefied petroleum gas) alongside methane
because it easily becomes a liquid on applying pressure
(b) It is used as a raw material for making synthetic rubber
2.6.4
Homologous Series
The group of organic compound having similar structures and chemical properties which can be denoted by the same general formula is known as homologous
series.
2.6.5
Alkyl Radical
The group of organic compound formed by removing one hydrogen atom from
alkane is called alkyl radical.
Examples: methyl radical CH3+ , ethyl radical C2 H5+ , etc. Alkyl radical is represented by Cn H2n+1 , it is denoted by R.
Formation of Alkyl Radicals
−1H
CH4 −−→ CH3+
−1H
C2 H6 −−→ C2 H5+
2.6.6
Functional Groups
An atom or group of atoms that determine the chemical properties of a hydrocarbon is called a functional group. Alkyl radicals combine with functional
groups and from different types of organic compounds.
Some common groups are:
(a) Hydroxyl −OH which makes alcohol
(b) Ether −O− which makes ether (an organic solvent)
(c) Carboxylic acid −COOH which makes acid
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2.6.7
IUPAC
IUPAC stands for International Union of Pure and Applied Chemistry. They
introduced a system to maintain uniformity in the nomenclature of inorganic
and organic compounds throughout the world. It is on the basis of this system
which determines the the name of the compound.
2.6.8
Isomers and Isomerism
Isomers are the organic compounds having similar molecular formula but different structures and properties. Similarly, isomerism is the existence of two or more
organic compounds having the same molecular formula but different chemical structures and properties.
Examples:
1. Butane C4 H10 shows isomerism. It has two isomers: n-butane and iso-butane.
(a) n-butane
H
H
H
H
H
C
C
C
C
H
H
H
H
H
(b) iso-butane
H
H
H
H
C
H
H
C
C
C
H
H
H
H
2. Pentane also shows isomerism. The three isomers of pentane are n-pentane,
iso-pentane, and neo-pentane.
(a) n-pentane
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
(b) iso-pentane
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H
H
H
H
H
C
H
H
H
C
C
C
C
H
H
H
H
H
(c) neo-pentane
H
H
H
H
C
H
H
C
C
C
C
H
H
H
H
H
H
2.6.9
Alcohol
The organic compound containing hydroxyl group −OH is called alcohol. It is prepared from alkane by replacing one or more hydrogen atom(s) by hydroxyl radical(s).
Its general formula is:
CH2n+1 OH
On the basis of number of hydroxyl groups, alcohols are divided into three groups:
1. Monohydric alcohol: It is formed by having only one hydroxyl group.
2. Dihydric alcohol: It is formed by having two hydroxyl group.
3. Trihydric alcohol: It is formed by having three hydroxyl group.
2.6.10
Some common Alcohol
1. Methyl Alcohol
Its IUPAC name is methanol and its molecular is formula is CH3 OH. It is the first
member of monohydric alcohol series.
Uses:
1. It is used for making methylated spirit
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2. It is used for making perfume, dyes, color, medicine, etc.
3. It is used as fuel in spirit lamp as it produces heat without smoke
4. It is used in dry cleaning
5. It is used to dissolve fat, oil, paint, varnish, etc.
6. It is used for making formaldehyde
7. It is used for making synthetic fibers
8. It is used for making methyl chloride
2. Ethyl Alcohol
It is IUPAC name of ethyl alcohol is ethanol. It is also known as drinking alcohol.
Uses
1. It is used as thermometric liquid
2. It is used for making alcoholic drinks
3. It is used to preserve specimens
4. It is used in hospitals, clinics, health posts, etc. to clean cuts and wounds
5. It is used manufacturing polythene, terylene, soap, color, paint, etc.
6. It is used as a solvent to dissolve resin, fat, oil, paint, etc.
7. It is used for making chloroform, ether, iodoform, etc.
8. It is used as a fuel
9. It is used for making medicine
10. It is used for making synthetic rubber
3. Glycerol
It is a trihydric alcohol which has sweet taste. Its is derived from the Greek word
’glyceros’ which means sweet in taste. Glycerol is also called glycerine.
It is a thick and colorless liquid having sweet taste. It is soluble in water and
alcohol but insoluble in ether.
The IUPAC name of glycerol is propane 1, 2, 3 triol. The molecular formula of
glycerol is C3 H5 (OH)3
Uses
1. It is used in face creams, lip guards, etc. to prevent skin from cracking
2. It is used for making printing ink and ink for stamp pads
3. It is used as a sweetening agent in sweet house, confectioneries, beverages, and
medicines
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4. It is used for making high quality soap, lotion, cosmetics, and shaving creams
5. It is used for moistening tobacco
6. It is used for preserving foods and fruits
7. It is used as a lubricant in watches
2.6.11
Glucose
It is a water-soluble white crystalline powder. Its molecular formula C6 H12 O6 . It
is also called dextrose. It is one of the three monosaccharide that are used directly
by our body to our produce ATP (Adenosene Triphosphate). Monosaccharides, also
called simple sugars, are the simplest forms of sugar and the most basic units from
which all carbohydrates are built. The name of glucose is derived from the Greek
word ’glukus.’
It is formed during photosynthesis from water and carbon dioxide in the presence.
It is also broken down into water, carbon dioxide, and energy during respiration.
It can also be obtained by the hydrolosis of carbohydrates like sugar, milk,
cellulose, etc. It is an important source of energy in most organisms.
It is sweet in taste. It is a carbohydrate and monosachharide sugar. It is found
in fruits and honey.
Its functions are:
1. It helps in transportation of free sugar in the blood of animals.
2. It is the main source of energy for cells.
It is both beneficial and harmful for animals. Low levels and high levels both cause
problems in the body. Thus it must be in a balanced amount in the body.
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2.7
Materials Used in Daily Life
2.7.1
Cement
Cement is a fine gray powder of calcium silicate and calcium aluminate. It is prepared from calcium carbonate CaCO3 and special type of clay (aluminum silicate
Al2 O3 SiO2 ). It used for construction as it sets into a hard rock-like state when
mixed with sand and water.
Manufacture of cement
The raw materials that are used for the manufacture of cement are:
1. Lime stone CaCO3
2. Aluminium Silicate Al2 O3 SiO2
3. Gypsum CaSO4 · 2H2 O
Then, these followings steps are done:
1. Crushing and Grinding: The big lumps of limestone and aluminum silicate are
first crushed and grounded into fine powder separately
2. Slurry Formation: The powder of limestone and the clay is mixed in 2:1 ratio
along with water to make semi-liquid mixture called cements slurry
3. Heating of slurry: The slurry thus formed is fed into the rotary kiln where it
is heated at the temperature of about 1400◦ C to 1600◦ C.
Then the limestone decomposes into calcium oxide and carbon dioxide. The
former combines with alumina Al2 O3 and silica SiO2 to form calcium aluminate.
This forms small pea sized balls of cement called cement clinkers which is a
mixture of calcium silicate and calcium aluminate.
∆
2CaCO3 + Al2 O3 SiO2 −−−−−−−◦→ CaSiO3 + CaAl2 O3 + 2CO2 ↑
1400−1600 C
4. Mixing with gypsum: Gyupsum is added to improve the setting time and
quality of the cement clinkers.
5. Final grinding: The mixture again ground into fine which is thus called cement.
Around 2% gypsum is added in the cement.
The cement is at last packed into air tight bags and stored in dry place to protect
it from moisture.
Uses
1. It is used to make cement mortar (a mixture of cement, sand, and water)
which is used for building and plastering of walls
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2. It is used to make concrete (mixture of cement, sand, water, and sand) which
is used for roofing, flooring, and making pillars of buildings
3. It is used to make reinforced cement concrete (RCC) that is a mixture of
cement, sand, water and gravel along with iron framework
2.7.2
Glass
Glass is hard, transparent, amorphous metallic silicate of different metals. Whilst
seeming solid, the molecules are found moving very slowly like that occurs in extremely cold liquid so it is also called a super cooled liquid.
The main raw material of glass is silica which is found in sand.
Also, as it is found neither in solid state or gaseous state but always found in
liquid state so it is also considered as the fourth state of matter.
The main properties of glasses are:
1. It is a homogeneous mixture of metallic silicates
2. It is transparent and hard solid object
3. It is a super-cooled liquid
4. It is a bad conductor of heat and electricity
5. It doesn’t react with chemicals
Depending upon the components and chemicals mixed in, glass is of different
types.
1. Quartz Glass: When pure silica is strongly heated at 1600◦ C and allowed to
cool slowly it turns into quartz cool.
It is different from other glasses as it doesn’t contain any ingredients except for
silica. Thus it is purer than other glass. It is used for making lab equipment,
lenses, gems, basins, crucibles, etc.
1600◦ C
Silica −→ Quartz Glass
2. Water Glass: It is formed when a mixture of silica, and sodium carbonate or
potassium carbonate is heated at 800◦ C.
∆
SiO2 + N a2 CO3 −→ N a2 SiO2 + CO2
Sodium Silicate
∆
SiO2 + K2 O3 −→ K2 SiO2 + CO2
Sodium Silicate
It is called water glass as it is soluble in water.
Uses:
(a) To make fire proof materials
94
(b) To make adhesive
(c) To make chemical garden
A chemical garden is an experiment where metal salts are added to an aqueous
solution of water glass. It results in the formation of plant like forms in minutes
to hours.
3. Ordinary glass or soda glass: It is formed by fusing a mixture of 50% silica,
15% sodium carbonate, 10% calcium carbonate and 25% glass pieces at 850◦ C
in a special type of tank furnace.
It is the most common type of glass.
The molten mixture is poured into moulds or blown with iron pipe to make
different glassware. This process is called annealing (heat treatment process
which changes physical and sometimes chemical properties of a material).
Which makes the glass more resistance to temperature fluctuation.
It is used to make bottles, light bulbs, window panes. It is also known as soft
glass.
2SiO2 + N a2 CO3 + CaCO3 −→ N a2 SiO3 · CaSiO3 + 2CO2
4. Hard glass or potash lime glass: It is the glass formed by fusing a mixture of
potassium carbonate, calcium carbonate and silica. It has high melting point
and can withstand high temperature.
2SiO2 + K2 CO3 + CaCO3 −→ K2 SiO3 · CaSiO3 + 2CO2
It is used for making lab apparatus like beakers, had glass test tube, tube
lights, etc.
5. Borosilicate glass: It is the glass formed by fusing a mixture of silica, sodium
carbonate, calcium carbonate and boric oxide is called borosilcate glass or
pyrex glass. It is resistance to chemicals and heat.
∆
5SiO2 + N a2 CO3 + CaCO3 + B2 O3 −→ N a2 SiO3 · CaSiO3 B2 (SiO3 )3 + 2CO2
It is used to make laboratory appratus such as test tubes, breakers, flasks,
condensers, and kitchenware.
6. Lead Crystal Glass: It is made by fusing a mixture of silica, potassium carbonate, and lead monoxide. This type of glass has high refractive index.
∆
2SiO2 + K2 CO3 + P bO −→ K2 SiO3 · P bSiO3 + CO2
Colored Glass
The glass is made colored by adding different metal oxide in molten glass.
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S.N Color
Metal Oxide
1
Blue
Cobalt Oxide
2
Black
Nickel Oxide
3
Green Cupric Oxide, Chromium Oxide
4
Purple
Manganese dioxide
5
Yellow
Ferric Oxide
6
Red
Cuprous Oxide
7
White
Tin Oxide
2.7.3
Ceramics
Ceramics is a special type of clay used for pottery, bricks kitchen wares, etc. Chemically, it is a hydrated aluminum silicate. It may have other substances such as
magnesium, carbonates, oxides of manganese, limestone, and iron. Basically, it is
the compound of carbon, nitrogen, oxygen, and silicon. The pure white clay is also
known as kaolin or china clay.
Clay is crushed, ground and seived and then mixed with water to make a paste.
It is molded into the desired shape and then dried and heated in kilns at high
temperature which makes it hard and strong and durable but they’re still porous
and absorb water.
Then, it is coated with a tin or lead oxide and again heated this process is called
glazing. It makes the object waterproof. It is also painted with metal salts and
different designs to make it more attractive.
Properties of ceramics:
1. They can withstand high temperature
2. Resistance to chemicals
3. Poor conductors of heat and electricity
4. Hard and brittle
Uses of ceramics:
1. They’re used to make different kitchen ware
2. They are used as insulators in electrical appliances
3. They are used to make artificial teeth and bone joints
4. They are used to make bathroom tiles, sinks, commodes, roof tiles, and bricks
2.7.4
Polymers and Plastics
Polymers is an extremely large molecule consisting of chain or network of small organic molecules called monomers. In other words: monomers are the simple organic
molecules which make up polymers whilst polymers are complex organic molecules
96
formed by the combination of two or more monomers. The process of forming polymer by chaining large number of monomers is called as polymerization.
Polymers may be natural such as protein, starch, cellulose, silk, wool, rubber, or
synthetic such as plastics, nylon or terylene.
2.7.5
Plastics
The word plastics comes from the greek word ’plastikos’ which means capable of
being moulded. Hence, plastics are manmade polymer which can be moulded to any
shape when they are warm. The starting monomers for plastics are obtained from
crude oil and small quantities of other substances often used to improve performance
or to reduce cost.
There are two types of plastics:
1. Thermoplastics:
Plastics which become soft on heating and hard on cooling are known as thermoplastics. The monomers here are connected via straight chain. In other
words, its molecules are linked in the form of linear polymers. They can be
moulded again and again into different shapes. They are soft, elastic, and less
brittle. Examples: polyethene, polyvinyl chloride, polystyrene or polyster, etc.
Uses of thermoplastics:
S.N
1
2
3.
Plastics
Uses
Polyethene
Polyethene bags, sheets, pipes
Polyvinyl Chlorine Pipes, raincoats, soles of shoes, handbags, boots, floor covering bottles
Polystyrene
Packing materials, thermocole
2. Thermosetting Plastics:
Plastics which are hard and strong and resistance to heat are known as thermosetting plastics. The monomers in thermosetting plastic are arranged in
cross linkage which cannot be broken down by heating. So they cannot be
remoulded. They are hard, non-elastic, and brittle in nature. Examples of
thermosetting plastics are, bakellite, melamine, etc.
Uses of thermosetting plastics:
S.N
1
2
3
Plastics
Bakellite
Uses
Housing radio, TV, switches, plugs,
handles of cooker, kettles, astrays, etc.
Melamine Unbreakable kitchenwares such as cup,
plates, bowls, glasses, etc.
Teflon
Used for making non-stick pans and can
handle very high temperature
Advantage of plastics
97
1. They can be easily shaped and moulded
2. They do not not rust
3. They are unaffected by chemicals
4. They are cheap and light
5. They can be used insulators for heat and electricity
6. They can be recycled (except thermosetting plastics)
Disadvantages of plastics:
1. They are non-biodegradable and cause pollution
2. They produce poisonous gas and smoke then burnt
3. They easily catch fire
4. They do not look as good as wood, stone, or metals
Differences between thermoplastics
SN Thermoplastics
1
They soften on heat readily
2
They can be reshaped
3
They can be recycled
4
They are soft, elastic, and less
brittle; example:
polyethene,
polyester
and thermosetting plastics
SN Thermosetting Plastics
1
They do not soften on heating
2
They can’t be reshaped
3
They can’t be recycled
4
They are hard, non-elastic, and
more brittle; example: teflon,
bakelite, and melamine
Bakelite
It is a thermosetting plastic prepared by the polymerization of carbonic acid (H2 CO3 )
and formaldehyde (HCHO).
Some of its properties are:
1. It is very hard in nature
2. It is used to prepare electrical switches, plugs, handles of cookers, etc.
2.7.6
Soap
Soap is a substance used for cleaning purposes. Chemically, it is a salt of fatty acids
that is capable of carrying away dirt along with water.
They’re obtained by treating vegetable or animals oils and fats with strong base
such as sodium hydroxide or potassium hydroxide in an aqueous solution. Their
general chemical formula can be written as:
∆
Fats or oil + base −→ Soap + Glycerol
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The process of making soap is known as saponification.
An example of soap is Sodium Stearate: N aOOCR or N aCOOC17 H35 . Where
R represents alkyl radical of long chain hydrocarbons
R = C17 H35 = Stearate
R = C18 H34 = Oleate
R = C15 H21 = P almitate
When soap is used (for cleaning) in hard water, it reacts with the salt of calcium
and magnesium present in hard water to form a brown layer on the clothes known
as scum. So soaps are not very good for cleaning in hard water, but since soaps are
biodegradable, they do not cause any pollution.
2.7.7
Detergents
Detergents are sodium salts of long chain of benzene sulphonic acid.
As they don’t react with calcium and magnesium salt they don’t form any scum.
So they’re good for cleaning in hard water. They are also cheaper than soaps because
they are formed from the byproduct of petroleum.
Detergents are also called soapless soap as they have cleansing action like soap
but are formed by chemicals that are different from soap i.e, from petroleum products. One example of detergent sodium lauryl suplhate C12 H25 SO4− N a+
Differences between Soap and Detergents
SN Soap
SN Detergents
1
They are the sodium or potas- 1
They are long chains of sulphonic
sium salts of fatty acids
acid
2
Their are not suitable for cleaning 2
They can be used for washing
in hard water
even in hard water
3
Animals fats or vegetable oils are 3
Petroleum products is used for
used for the preparation of soaps
the preparation of detergents
4
They are biodegradable
4
Not all detergents are biodegradable thus some of them cause water pollution
5
They have weak cleansing action 5
They have strong cleansing action
2.7.8
Fertilizers
Fertilizers are the substances which provides essential elements to the growing plants
as well as nourishes the microorganism. It replenishes the nutrients consumed by
the plants in the soil.
A good fertilizer should be easily soluble in water and it should not leave any
harmful impact to the soil.
There are two types of fertilizers:
Organic Fertilizers
99
They’re the fertilizers derived from the decomposition of organic compounds i.e.,
plants and animals.
1. Green manure is a type of organic fertilizer where green plants are directly
mixed with the soil. They provide nutrients and prevent soil erosion. They
increase the amount of humus in the soil.
2. Compost Manure is another type of organic fertilizer. They are made from
dead, decayed plant and animal matter.
Role of Compost Fertilizer
1. Compost fertilizer is rich in carbonic matter. This helps for healthy growing
and better yield.
2. It does not show any adverse effect in the atmosphere.
3. It protects the water in soil
4. It protects environment from pollution from chemical fertilizers and pesticides.
Inorganic Fertilizers
The fertilizers prepared from various chemical substances (minerals) are known as
chemical fertilizers. Similarly, the fertilizers prepared by mixing nitrogen, phosphorous, and potassium are called NPK fertilizers.
1. Nitrogen Fertilizer:
The fertilizer containing nitrogen as nutrients is known as nitrogen fertilizer.
Examples: ammonium nitrate N H4 N O3 , urea N H2 CON H2 , ammonium sulphate (N H4 )2 SO4 etc.
Deficiency Symptoms for Nitrogen In Plants
(a) Yellow leaves
(b) Low growth and development of plants
(c) Small sized fruits and seeds
Advantages of nitrogen in plants
(a) It helps in the fast development and growth of plants
(b) It helps to produce large amount of chlorophyll and protein
(c) It helps to increase crop productivity
2. Phosphorous Fertilizer
The fertilizer which contains phosphorous as nutrient is called phosphorous
fertilizer. Some examples are ammonium phosphate (N H4 )3 P O4 , super phosphate Ca(H2 P O4 ) · 2CaSO4 , triple phosphate 3Ca(H2 O4 )2 etc.
Deficiency Symptoms of phosphorous in plants
100
(a) Less development of roots
(b) Decrease in cell division
(c) Less development of grains
Advantages of Phosphorous in Plants
(a) It helps in proper root development
(b) It helps in ripening of the fruit
(c) It helps in the protein synthesis, cell division, and development of leaves
Potassium Fertilizer
The fertilizer which contains potassium as nutrient is called potassium fertilizer. Some examples are: potassium nitrate KN O3 , potassium chloride KCl,
potassium sulphate K2 SO4 , etc.
Deficiency Symptoms of Potassium in Plants
(a) Difficulty in the protein synthesis and cell division
(b) Wilting and withering of leaves
(c) Reduction in disease resistant capacity
Advantages of Potassium in Plants
(a) It helps in protein synthesis and cell division
(b) It helps in photosynthesis
(c) It increases the disease resistance capacity
Advantages of chemical fertilizers
1. It increases crop productivity
2. It gets absorbed by plants quickly
Disadvantages of chemical fertilizers
1. It causes air, water, and soil pollution
2. Same type of chemical fertilizer decreases soil fertility
2.7.9
Insecticides
Manmade poisonous chemicals which are used for destroying or killing harmful insects are known as insecticides.
Generally, most insecticides are poisonous and non-biodegradable. One needs to
practice precaution as they’re toxic to humans and animals. Their disadvantages
are long-therm so they should be used less.
There are two types of insecticides:
101
1. Organic Insecticides
(a) Organochlorine: DDT (Dichloro Dephenyl Trichloroethane), BHC (Benzene Hexachloride), Dialdrin, Methoxychlor
(b) Organophosphorous: Malathion, parathion, phosdrin, etc.
(c) Carbamate: Baygon, Turmic
2. Inorganic insecticides: Calcium arsenate, fluorides, lead arsenate, lime sulphur
Advantages of insecticides:
1. They control harmful insects
2. They also help in disease control
Disadvantages of insecticides:
1. The continuous use of insecticides makes the insects more resistant to them
2. Insecticides may kill useful insects and disturb ecosystems
3. Consumption of fruits and vegetables with insecticides residue may lead to
cancer
2.7.10
Fibers
Fibers are thread like strong materials used for making clothes, nets, ropes, etc.
There are two types of fibers. They are:
1. Natural Fibers: Fibers that are obtained from animals and plants are called
natural fibers such as cotton from cotton plants, silk from silkworm, wool
from sheep, rabbit, etc. Natural fibers are warm. But they’re not in abundant
amount. Few disadvantages of natural fibers are:
(a) They shrink when washed with water
(b) Insects easily attack them
(c) They are expensive
(d) They absorb a lot of water so they are difficult to dry off
(e) They do not retain crease on ironing
2. Artificial Fibers: The man made fibers are called artificial fibers. There are
two types of artificial fibers:
(a) Synthetic Fibers: Man made fibers made through a chemical process.
Examples: nylon, terylene, terywool, etc.
(b) Recycled Fibers: These are the man made fibers by recycling the natural
fibers. Rayon is produced by cotton cellulose and wood pulp and as it
looks like silk it is also called ’artificial silk’
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Artificial fibers are strong and more convenient. They do not shrink shrink on
washing. They are not attacked by insects. They are easy to was and dry up
quickly. They are also cheap and can be produced in bulk.
2.7.11
Chemical Pollution
The pollution caused by the excessive use and improper disposal of chemicals is
called chemical pollution.
They are caused because of:
1. Use of chemical fertilizers:
Chemical fertilizers degrades the quality of soil and reduces its crop productivity if it is used in excessive amounts.
When unused chemical fertilizers reached to the water resources such as rivers,
lake, ponds etc, etc, then aquatic plants use to grow rapidly. These plants
use large amount of oxygen present in th water. Due to the lack of oxygen
the number of aquatic animals decreases in such places and hampers aquatic
ecosystem.
2. Automobile and Industrial Waste
The chemical substances emitted from automobiles and industries are called
automobile and industrial waste. Examples: carbon dioxide, carbon monoxide,
sulpher dioxide, nitrogen dioxide, mercury, lead, etc.
When industrial gases come in contact with rain water, they form different
types of acids. The rain which contains different types of acids due to the
combination of industrial gases with rain water is known as acid rain.
Some effects of acid rain are:
(a) It destroys physical and biological environment
(b) It decreases soil fertility
The phenomenon of increasing the temperature of the earth due to the presence
of green house gases is called the green house effect.
3. Synthetic Cleanser
Synthetic cleanser such as soap, detergent, etc. possess different poisonous
chemical substances. When these substances are exposed to plants, they destroy them as well as cause chemical pollution.
4. Plastic
Plastic materials are not biodegradable and they produce harmful gases when
they are burned. These emitted gases pollute the environment and cause
chemical pollution.
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5. Coloring Matter
Coloring matter (dye) is used in food stuffs to make them attractive. Many of
them are inedible and show adverse effect.
6. Insecticides
Insecticides are the chemical substances that is used to kill harmful insects.
But they also kill useful insects.
They cause imbalances of the ecosystem of a particular area. Some examples of
insecticides are: DDT (Dichloro Diphenyl Tricholoroethane), BHC (Benzene
hexachloride), methoxychloride, aldrin, dialdrin, etc.
Adverse effects of DDT are as follows:
(a) It pollutes the physical and biological aspect
(b) It shows adverse effect to the aquatic animals
(c) It affects the reproductive system of animals
(d) It causes respiratory tract diseases
(e) Birds give useless eggs
(f) All eggs aren’t fertile
Control of chemical pollution
1. Public awareness should be raised
2. Population growth and unplanned urbanization should be controlled
3. Use of insecticides and chemical fertilizer should be limited
4. Proper monitoring mechanism should be developed
5. Biodegradable and non-biodegradable waste should be separated
6. Use of color and dyes in food materials should be prohibited
7. Industries should be established far from human settlement
8. Industries should be established far from human settlement
2.7.12
Solid Waste
Solid wastes are the waste products which are solid in nature. There are biodegradable and non-biodegradable solid wastes. Biodegradable solid wastes are the solid
wastes which can get decomposed after a short period of time. Examples: paper,
cloth, dead plants, etc. Non biodegradable solid wastes are the solid wastes which
don’t decompose. Examples: plastic, glass, iron, etc.
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2.7.13
Solid Waste Management
The collection, transportation, treatment, and recycling of solid waste in a proper
manner is called solid waste management.
Some steps to manage solid wastes are as follows:
1. Reduction in the generation of solid wastes
2. Reuse of solid waste materials
3. Production of fertilizers from wastes
4. Incineration: Incineration is the process of burning wastes at high temperature
i.e., at about 500-1200◦ C
5. Land Filling
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Chapter 3
Biology
3.1
Some Invertebrates
3.1.1
Invertebrates
Those animals which don’t possess a backbone (spine) are called invertebrates.
Arthropoda
It is one of the many phylum of the sub-kingdom Invertebrates. Animals of this
phylum are characterized by:
1. Their jointed legs
2. Division of their bodies into head, thorax, and abdomen
3. Possession of at least one pair of compound eyes
4. Respiration through spiracles, generally
3.1.2
Silkworm
Classification
Kingdom: Animalia
Sub-Kingdom: Invertebrates
Phylum: Arthropoda
Type: Silkworm
A silk worm is a commercially cultivated insect due to their ability to produce
extremely strong natural fibers which is known as silk, which are used to make
clothes.
The species of silk worm which are typically cultivated in the country are:
1. Bombyx Mori ”Seri Silk Worm”
2. Attacus Ricini ”Eri Silk Worm”
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3.1.3
External Structure of Silkworm
An adult silk worm is about 2.5cm in length and creamy white in color. Its body is
divided into three parts i.e., head, thorax, and abdomen. It has three pairs of legs,
two pairs of wings on its throax, and a pair of antennae on front.
Female silkworms are larger than male silkworms.
3.1.4
Life Cycle of a Silk Worm
Silkworm goes through four stages in its life cycle. Those are:
1. Egg
2. Larva
3. Pupa
4. Adult
In Silkworm fertilization is internal and the female lays eggs after mating with a
male. It takes a silkworm 45 days to complete its life cycle.
Egg
A female silkworm lays about 300 eggs at a time and dies afterwards. Its eggs are
white in color. The eggs of a silkworm are kept in cold places in the lack of mulberry
leaves in winter season to prevent eggs from hatching. When there is a sufficient
amount of mulberry available, the temperature of the place gets maintained between
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18◦ C and 25◦ C and the eggs hatch. It takes 10 to 12 days for the eggs to hatch.
Larva
The larva is brown colored and about 6mm in length when it hatches from its egg.
Its body is divided into three parts: head, thorax, and abdomen. It is extremely
voracious and grows rapidly in size by consuming mulberry leaves for 25 to 32 days.
The periodic shedding of skin during the larva stage of the silkworm is called
moulting. A silkworm larva moults 4 times during its larva stage. The silkworm
larva doesn’t eat anything for 20 to 24 hours after molting.
Pupa
The capsule or case formed by sticky fluid made by the larva of a silkworm to enclose
itself is called a cocoon.
To obtain silk threads, the cocoon is heated up in boiling water or a hot oven
to destroy the glue of the cocoon. Then the silk thread is unrounded from the hot
cocoon.
Some silkworm cocoon are not destroyed to continue the next generation of silk
worm.
Adult
3 pairs of legs and 2 pairs of wings are developed within the pupa through active
metamorphosis. The adult silkworm is capable of flying immediately after hatching
out of its cocoon.
Metamorphosis is the process through which major change occurs within the
form or structure of a pupa of an insect.
An adult silk worm lives for 7 days.
3.1.5
Silk
The rearing of silkworm for commercial purpose is known as sericulture. Sericulture
increases the economic condition of an individual and nation. The clothes produced
through silk threads can be worn in any season.
Properties of Silk
1. Silk thread is light, soft, strong, durable, and shiny in nature
2. Silk thread can be modified into different color
3. It absorbs water easily
4. It is elastic in nature and is the strongest natural fiber
3.1.6
Honey Bee (Apis Mellifera)
Classification
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Kingdom: Animalia
Sub-kingdom: Invertebrates
Phylum: Arthropoda
Type: Honey Bee
Honey bees live in a large group in a single colony, as such they are called social
insects. They produce nutritive honey. It consumes juices of flowers. They have
extremely high discipline and live in an organized group. Honey bees have different
functions depending on their type. There are three types of honey bee:
1. Queen Bee
2. Drone Bee
3. Worker Bee
3.1.7
Types of Honey Bee
Queen Bee
The largest type of bee. It has small and round head with a short sting at the end
of its abdomen. It’s body is divided into head, thorax, and abdomen. It is diploid
in nature, has 2 pair of chromosomes. The queen has the following functions:
1. To lay eggs
2. To coordinate all the other honey bees according to the condition
Drone Bee
The second largest type of bee. It is black in color and doesn’t possess poisonous
gland, nectar collecting gland, and pollen sacs. It is fed by worker bees. Its function
is to fertilize a queen. It is haploid in nature, as it only one set of chromosome for
each homologous pair.
Worker Bee
The smallest type of bee. It possess pollen basket and has various glands which get
activated and deactivated depending on its age. It is diploid in nature. Its functions
are:
1. To collect nectar from flowers
2. To make the hive and keep it warm
3. To defend the hives from enemies
Note: There are 16 chromosomes in unfertilized haploid egg and 32 chromosomes
in fertilized diploid eggs.
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3.1.8
Nuptial Flight
When a colony of bees exceeds a certain number of worker bees, the old queen bee
leaves the hive alongside a number of worker bees and drones to create a new hive.
When such a thing happens, a new queen is made for old hive.
After 3 to 5 days, the new queen goes to mate with a drone bee. The flight taken
by the queen bee and a number of drone bee for mating outside the hive is called
the mating or nuptial flight.
3.1.9
Life Cycle of a Bee
A bee’s life cycle is divided into four parts: egg, larva, pupa, and adult.
Egg
A queen bee lays about 3000 eggs in a day, which can be different depending on the
exact species, after 2 to 3 days after mating. This stage lasts for 3 days. On the
first day, the egg is positioned vertically, on the second the egg is inclined, and it
becomes completely horizontal on the third day. Depending on which cell its layed,
an egg can result in a drone, worker, or a queen.
Larva
The larva stage lasts for 5 to 5.5 days, 6 days, and 6 days, for queen, worker, and
drone respectively. The nature of the food consumes determines the type of honey
bee produced. The time for consuming royal jelly is 5 to 5.5 days, 6 day, and 6
days for queen, worker, and drone respectively. Royal jelly is a special type of food
produced by worker bees to feed the larvae.
A honeybee larva moults 4 to 5 times.
Pupa
It is called resting of an insect. A queen bee remains in pupa stage for about 8 days,
and worker bees and drones for 14 days.
Adult
Generally, queen takes 15-16 days, workers 20-21 days, and drones 22-24 days to
reach the adult stage.
3.1.10
List of age and work relation of worker bees
ˆ 1-3 days: Learning to walk. Giving warmth to egg, larvae, and pupa. Eating
waste food nearby
ˆ 4-6 days: Feeding pollen and honey to aged larvae; consuming sufficient food
itself
ˆ 7-11 days: Produces royal jelly and feeds it to the queen and larvae
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ˆ 12-17 days: Glands to produce royal jelly dries out. Starts to produce beeswax
and builds hive
ˆ 18-20 days: Wax glands dry up. Gains poisonous gland and stinger develops;
begins to guard the hive
ˆ 21st day: Starts to fly to gather resource (nectar, water, flower juice) etc.
3.1.11
Uses of Honey Bees
Honeybees are a major pollinator and produces honey, which is a good source of
income. The process of rearing honeybees is called apiculture.
Advantages of Honey
1. It is a good source of nutrition and tonic
2. It is fruitful patient suffering from various illness and diabetes
Advantages of honey wax
1. it is used to make toilets and some materials
2. It is used to make candle, shaving cream, cold cream etc.
Economical Advantages of Honey Bees
1. They produce honey which is a good source of income
2. They help to produce bees wax which can be made into candle, shaving cream,
cold cream etc. to sell for monetary value
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3.2
3.2.1
Human Nervous and Glandular System
Nervous System
The system which is responsible for receiving and transmitting message to different
parts of our body with the help of nerve is called the nervous system. Its main
functions are:
1. It gives information about the external world with the help of sense organs
2. It coordinates and controls the activity of voluntary and involuntary muscles
The nervous system can be divided into three parts:
1. Central Nervous System: Includes brain and spinal cord
2. Peripheral Nervous System: Includes cranial and spinal nerve tissues
3. Autonomic Nervous System: Includes ganglia and involuntary muscles controlling nerve tissues
3.2.2
Central Nervous System
Brain
The brain is the largest part of the central nervous system. It is protected inside
our skull.
It is protected by a three layered outer-covering membranes called meninges.
The layers are:
1. dura matter: it is attached to the inner layer of the skull
2. pia matter: it is attached to the surface of the brain
3. arachnoid: it is in the middle, between dura and pia matter.
The space between the arachnoid and pia matter is called subarachnoid space. It
contains crebrospinal fluid which protects our brain from mechanical shock.
The brain is divided into three parts:
1. Cerebrum
2. Cerebellum
3. Medulla Oblagata
Cerebrum
The uppermost and largest part of our brain is the cerebrum. It occupies about
80% of our brain. It is located in the region of frontal, parietal, and occipital bone
of our skull. It is divided into two cerebral hemisphere. A deep fissure is located
between the hemisphere.
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The human brain is littered with convolutions. Convolutions are a number of
ridges and groves which increase the surface area of the brain.
The outer part of the cerebrum is made out of gray matter whilst the inner part
is made up of white matter. Any injury in the cerebrum leads to coma.
Functions of cerebrum are:
1. It coordinates and controls activities, such as emotion, hearing, speaking,
thought, analysis, anger, prediction, sensations, etc.
2. It controls the activities of the other parts of the brain.
Cerebellum
The lemon sized hemispherical part located below the cerebrum and above the
medulla oblangata is called cerebellum. Like the cerebrum, the outer part is made
up of gray matter and the inner of white matter. Any injury to it leads to vomiting
and imbalance, it may even lead to paralysis. It is the part of the brain affected by
alcohol.
Its functions are:
1. It maintains the posture of our body
2. It coordinates the muscles properly
3. It coordinates the voluntary movements of our body
Medulla Oblangata
The lowermost cylindrical part of our brain is called the medulla oblangata. It
is cylindrical in shape. It is located above the spinal cord. Unlike cerebrum and
cerebellum, its outside is made up of white matter and the inside is made up of gray
matter.
Any injury to this part leads to immediate death.
Some of the functions medulla oblangata are:
1. It coordinates and controls activities such as vomiting, sneezing, swallowing
food, coughing etc.
2. It coordinates respiration
3. It helps in the elongation and contraction of blood vessels
4. It coordinates and controls peristalsis (rhythmic contraction and relaxation of
the digestive track), flow of digestive juice, hormone, saliva, etc.
Spinal Cord
The long and soft spinal tissue located inside the vertebral column which elongates
from lower part of the medulla oblangata to lumbar vertebrae is called spinal cord.
It is made up of white matter on the outside and gray matter on the side.
Any injury to the spinal cord stops the functions the part of the body lower than
the injured section. Injury of this type is called spinal injury. Nerve fiber is located
in white matter of the spinal cord. It is also covered in meninges.
Some functions of the spinal cord are:
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1. It is center of reflex actions
2. It coordinates spinal nerves and brain
3.2.3
Neuron
The smallest unit of the nervous system is called the neuron. It is also called nerve
cell but they’re not exactly the same. It is composed of cell body, dendrites, and an
axon. The cell body or cyton contains the nucleus and cytoplasm. Cyton receives
messages through dendrites.
1. Axon: It is the long tube like structure originated from the cell body which
is responsible for bringing in impulses from the cell body to send it to other
dendrites
2. Dendrite: It is the highly branched thin structure which surrounds the cell
body which is responsible for sending impulses to other cell bodies through
their axons.
Nerve fiber is formed by the combination of axon of neuron. There are three types
of nerve fibers:
1. Afferent or sensory nerve: It transmits nerve impulses from receptors to the
brain or spinal cord
2. Efferent or motor nerve: It transmits nerve impulses from brain or spine to
different parts fo the body
3. Inter neuron: It converts sensory impulse. The inter neuron functions to read
the signals from sensory nerves and give signals to the efferent nerves. They
facilitate the communication between sensory and motor nerves.
Reflex Action
Reflex action can be defined as the sudden and involuntary reaction to stimulus. It
is governed by the spinal cord.
At first, the receptors pick up upon the stimulus and send it to afferent nerves.
Afferent nerves then send that to the inter-neuron. From there, the body reads the
signal and a then signal is passed from the inter-neuron to the afferent nerves. The
afferent nerves give the desired signals to the effectors, muscles, and in this way a
reflex action is carried out.
3.2.4
Ganglia
A group of nerve tissues composed of gray matter found near the spinal cord of
vertebral column is called ganglia. It connects brain and spinal cord.
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3.2.5
Peripheral Nervous System
It includes brain and nerve tissue. Nerve tissue is composed of cranial nerve tissue
and spinal nerve tissue.
Cranial Nerve Tissue
The nerve tissue which starts from brain and ends at the brain is called cranial nerve
tissue. 12 pairs of nerve tissues are originated from the brain. They coordinate different organs of head such as eyes, ear, nose, tongue, etc. with the brain. Note: The
speed of DC in a conducting wire is 150,000,000m/s. The speed of a nerve impulse
is 1,000m/s.
3.2.6
Autonomous System
The nervous system which controls the activities of muscles and fixed type of gland
when we are sleeping or awake is called autonomous nervous system. It is divided
into two parts:
1. Sympathetic Nerve System: Increases the activity of heart, respiration, intestine, urination, etc.
2. Parasympathetic Nerve System: Decreases the activity of heart, respiration,
intestine, urination etc.
The above two nervous systems are opposite of each other as they do the opposite
work of one another.
3.2.7
Glandular System
The system of our body which secrets different types of juices needed by our body
with the help of glands is called glandular system. There are two types of glands:
1. Exocrine Gland: Ducted glands which secrete enzymes and whose production
and working region are close to each other. They send their juices through
their duct. Examples: tear gland, sweat gland, etc.
2. Endocrine Gland: Ductless gland which secrete hormones. As they send their
juices into the blood stream, their working and production area are from each
other. They stimulate body cell and other glands’ activities.
Hormones are called chemical messengers are they are a chemical substance and
serve as a means of communication between the various body parts to stimulate one
another.
Types of endocrine gland are:
1. Pituitary Gland
(a) It is located under the brain inside the cranium and is shaped like a pea
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(b) It secrets many hormones including growth hormone which help in the
physical and mental development of our body
(c) It controls and coordinates the activities of the other ductless glands so
it is called the master gland
(d) Hypersecretion of growth hormone causes gigantism whilst hyposecretion
causes dwarfism
2. Thyroid Gland
(a) It is located in the neck and comes in a pair, one on the left and the other
on the right
(b) It secrets thyroxin (which contains iodine) and thryotrobin hormone
(c) Thyroxin affects the activities of the cell and helps in the physical development of our body
(d) Excess secretion of thyroxin hormone causes increase in the rate of metabolism,
excessive sweating and hunger, loss in weight, mental irritability etc.
(e) Hyposecretion causes physical and mental retardation, dry skin, hoarse
voice, less sweating, etc.
(f) The swollen thyroid gland due to the lack of iodine is called goiter
3. Parathyroid Gland
(a) It located at the back of the thyroid gland, thus it also comes in a pair
(b) It secretes hormone called parathrome or parathyroid hormone which
helps in the exchange of calcium in blood
(c) Hypersecretion causes tumor and kidney stone
(d) Hyposecretion causes tetany (twitching of muscles) and decrease in amount
of calcium in blood
4. Adrenal Gland
(a) It is located at the top of each kidney thus coming in pair
(b) It secretes adrenaline manages blood pressure, sugar level etc. During
emergencies, the adrenaline is released which prepared and helps our
body by giving it more energy and making it function with more alertness.
Hence, for this reason adrenaline is called emergency hormone. Similarly,
adrenal gland is called emergency gland.
(c) Hypersecretion causes high blood pressure
(d) Hyposecretion causes low blood pressure, weakness, less sugar, etc.
(e) Adrenal cortex is the outer part of the gland which secrets several hormones such as cortiron hormone that helps in the regulation of metabolism
and helps in responding to stress, aldosterone which helps to control pressure, and androgen the sex hormone found in both male and female body
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(f) Hypersecretion of androgen causes males to develop feminine characteristics whilst females to develop masculine characteristics
5. Pancreas
(a) It is located at the loop of duodenum
(b) It is called a mixed gland as it secrets both enzymes and hormones
(c) It secrets insulin and glucagon, insulin controls the amount of sugar in
blood whilst glucagon supplies the amount of sugar in the blood
(d) Hyposecretion of insulin causes an increase of sugar level in blood, excessive hunger, thirst, and frequent urination, this disease is called diabetes
6. Gonads
(a) Testes in males and ovaries females are called gonads
(b) It is called mixed gland as it produces gametes and hormones
(c) Ovary secretes oestrogen and progesterone whilst testes secretes testosterone
(d) Testosterone plays a major role in the changes which occur in adolescent
boys, lack of testosterone causes infertility
(e) Similarly, oestrogen also plays a major role in the changes which occur in
adolescent girls whilst progesterone helps in the development of uterus.
Lack of these hormones cause infertility in women.
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3.3
3.3.1
Blood Circulatory System
Introduction
The system of our body responsible for transporting oxygen and nutrients to the
cells and which helps to excrete out waste material with the help of the blood is
known as the circulatory system.
Structure of the blood
Blood is the red colored fluid connective tissue which flows in the blood vessels. It
transports oxygen and nutrients to the cell and excretes out the waste materials
from the cell. It contains all the necessary materials required for our body. About
5.5 liters of blood is present in the body of an average adult person
Composition of blood
Blood contains about 55% plasma and 45% blood cells. There are three types of
blood cells:
1. Red Blood Cells
2. White Blood Cells
3. Platelets
3.3.2
Plasma
The pale yellowish colored transparent fluid found in the blood in which blood cells
are suspended is called plasma. The name of plasma protein is fibrinogen. Plasma
contains about 90% water and 10% protein, fats, salts, carbohydrates, etc.
Some functions of plasma are:
1. It circulates and controls the amount of water in our body
2. It helps to excrete and waste materials from different organs of our body
3. It transports urea to the kidney from liver
4. It transports hormones from endocrine glands to the tissues
5. It helps in blood clotting by the help of fibrinogen
6. It helps to transport digested food to different parts of our body
Haemophilia
The sex linked disease in which blood does not clot in wounds and cuts is called
haemophilia. Fibrinogen helps in the clotting of blood, blood does not clot well in
wounds and cuts in the lack of its presence.
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3.3.3
Red Blood Cells (RBCs)
The scientific name of RBCs is erythrocytes. It is circular and biconcave in shape.
It lacks a nucleus. There are about 4,500,000 to 5,000,000 RBCs found in 1mm3 of
blood. They are formed in bone marrow and are destroyed in the liver and spleen.
The average lifespan is 90 to 120 days. About 2,000,000 RBCS are formed and
2,000,000 RBCs are destroyed per second. RBCs is red in color due the presence of
haemoglobin which serves as a red pigment.
Iron is found within the haemoglobin of the blood for the transportation of
oxygen.
People suffering from anemia lack RBCs in the blood. They do no get sufficient
oxygen in their cells. Due to the lock of oxygen in the cells, they get tried quickly.
The main function of RBC is to transport oxygen and carbon dioxide in our
body.
3.3.4
White Blood Cells (WBCs)
The scientific name of WBCs is leukocytes. It has no fixed shape. It possess nucleus.
There are about 6,000 to 10,000 WBcs found in 1mm3 of blood. They are formed
in lymph node and spleen.
WBC is the largest blood cell. It does not contain haemoglobin. Its average life
span is about 15 days. There are two types of WBCs:
1. Granular: Neutrophyll, Eaosinophyll, and Basophyll
2. Non-Granular: Monocyte and Lymphocyte
Lack of WBCs in blood causes leucopenia (decrease in immunity power) and excess
of WBCs causes leukemia (blood cancer).
The main functions of WBCs are:
1. It fights with causative agents of the diseases
2. It destroys some causative agents of the diseases
3. It removes the destroyed materials near the wound and treats the wound
3.3.5
Platelets
The scientific name of platelets is thrombocytes. It is small and round or oval in
shape. Platelet is the smallet blood cell. It lacks nucleus. It is colorless. It is formed
in the red bone marrow. Its life on average is between 2 to 3 days. There are about
200,000 to 400,000 platelets found in 1mm3 of blood.
Blood does not clot properly in the wound if there is a lack of platelets. It helps
in the clotting of the at the wound by the help of fibrinogen.
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3.3.6
Functions of blood
There are three major functions of blood:
1. Transportation related functions of blood
(a) It transports oxygen from lungs to cells of our body and brings carbon
dioxide back to the lungs from the cells
(b) It helps to transport waste materials from our body through liver, lungs,
and kideny
(c) It transports the hormone secreted by endocrine glands to different parts
of the body
(d) It transports absorbed nutrients from intestine to different parts of our
body
2. Regulation Related Functions of Blood
(a) It keeps our body warm by maintaining temperature
(b) It controls liquid and other chemical substances in tissues
3. Protection related functions of blood
(a) It protects our body from different diseases
(b) It helps in blood clotting
3.3.7
Heart
The human heart is located in the thoracic cage in between the two lungs. It is
made up of powerful cardiac muscles. It lies tilted to the left side of the chest.
A double layered transparent membranous sac called the pericardium covers it.
Pericardial fluid is found in the pericardium. It protects the heart from mechanical
shock and injuries.
The functions of pericardial fluid or pericardium
1. It protects the heart from mechanical shock
2. It allows for the frictionless movement of the heart during the purification of
the blood
There are four chambers in our heart.
1. Right Auricle
2. Right Ventricle
3. Left Auricle
4. Left Ventricle
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The upper chambers are called auricles whilst the lower chambers are called
ventricles. As auricles pump blood into the ventricles, they’re less muscular and
thin walled. The opposite is the case for ventricles. As they pump blood throughout
the entire bodies they are much more muscular and thus have thicker walls.
Also, due to how thickness is related with the pumping, the walls of the left
ventricle is thicker than the walls of the right ventricle. As left ventricle is responsible
for pumping blood into the various parts of our bodies (systemic circulation) whilst
the right ventricles are responsible for pumping blood into the lungs for purification
i.e., pulmonary circulation. It is obvious that the former requires much more force
than the later.
Aorta is the largest artery found in our body. The blood flows to different parts
of our body through the aorta. The artery that joins the heart to the lungs is called
the pulmonary artery and similarly, the vein which joins the lungs to the heart is
called pulmonary vein.
Pulmonary artery carries impure blood (deoxygenated blood) from the right ventricle to the lungs and the pulmonary vein carries pure blood (oxygenated) from the
lungs to the left auricle (left atrium).
Differences Between Auricles and Ventricles
SN
1
2
3
4
5
3.3.8
Auricle
They are the upper chambers
They are thin walled
They are smaller
They receive blood from different
parts of the body and push it into
the the ventricles
Veins originate from the auricles
SN
1
2
3
4
5
Ventricles
They are the lower chambers
They are thick walled
They are bigger
They receive blood from the auricles and pump it into various
parts of the body
Arteries originate from the ventricles
Chambers of Heart
There are four chambers in the heart, left/right auricle and ventricle. They each
have their own function. Auricles receive blood various parts of the body through
veins which originate from them and the ventricles pump blood into the various
parts of the body which they receive from the auricles.
Due to that, ventricles are bigger, more muscular, and have thicker walls when
compared to auricles.
The auricles are separated from each other by the inter-atrial septum. Likewise,
the ventricles are separated from each other by the inter-ventricular septum. Furthermore, the walls separating the auricles from the ventricle is known as auriculoventricular septum.
The heart has various valves as well within it as well. These valves are muscular
flaps which allow for unidirectional flow of blood. The valves are needed so that the
heart can pump blood properly. The valves in our heart are:
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1. Right atrio-ventricular or tricuspid valve: This valve is present between
the right atrium (auricle) and ventricle. It allows the (deoxygenated) blood
to flow from right auricle to right ventricle only. It is called tricuspid due to
the presence of three triangular leaf-life flaps (cusps). When the ventricle contracts, the valve closes the right atrio-ventricular aperture and thus prevents
back flow. This allows the blood to be pushed into the pulmonary artery.
2. Left atrio-ventricular or bicuspid valve: This valvue is present between
the left atrium and ventricle. It is responsible for the unidirectional flow of
pure blood from the left auricle to the left ventricle. As its name implies,
it consists of two cusps. When the heart contracts, it closes the left atriventricular aperture which prevents the back flow of the blood and causes it
to be pushed into the aorta.
3. Pulmonic Valve: It is the valve located between the right ventricle and the
pulmonary artery. It is made out of three half-moon shaped flaps attached to
the arterial walls. The valve allows the blood to flow from right ventricle to
lungs only. When the heart relaxes, the valve activates and stops the blood
from flowing back into the (right) ventricle from the (pulmonary) artery.
4. Aortic Valve: It is the valve located between the left ventricle and the aorta.
It is made out of three half-moon shaped flaps attached to the arterial walls.
The valve allows the blood to flow from left ventricle to the aorta only. When
the heart relaxes, the valve activates and stops the blood from flowing back
into the (left) ventricle from the aorta.
3.3.9
Blood Vessels
The system of tubes in our body responsible for housing blood and allowing them
to transport throughout the body is known known as the blood vessels. They are
three layered. From lowermost to outermost, they are:
1. Endothelium
2. Smooth Muscles
3. Connective Tissue
3.3.10
Artery
Artery is one of the three blood vessels in the human body. It is defined as the blood
vessel which carries oxygenated blood away from our heart. It has thick walls. The
blood within the artery flows with high speed and great pressure. The artery lacks
any valves. The branch of an artery is called an arteriole. Except for pulmonary
artery, every artery carries pure (oxygenated) blood. Arterioles get divided into
capillaries. They help in the exchange of nutrients, salts, sugar, amino acids, and
gas between blood and cells.
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3.3.11
Vein
The blood vessel which brings deoxygenated blood from different parts of our body
back to the heart is called vein. It has thin walls, The blood flows with low speed
and pressure in the vein. Except pulmonary vein, every vein carries impure (deoxygenated) blood. Artery is deep seated whereas veins are superficial. The branch of
a vein is called a venule. The branches of venules are also called capillaries.
3.3.12
Capillaries
The blood vessels which are directly linked with our body cells are called capillaries.
Nutrients and materials are taken in by the cells through the process of diffusion,
similarly, waste materials are also excreted out of a cell. Both of these (consumption
and excretion of the cells) are done through capillaries.
3.3.13
Pulmonary Circulation
Right Ventricle
Left Auricle
Pulmonary Artery
Lungs
Pulmonary Vein
The movement of blood from heart to lungs is called pulmonary circulation. It starts
from right ventricle and ends at the left auricle. The deoxygenated blood from right
ventricle is passed to the lungs through pulmonary artery for its purification. The
blood becomes oxygenated in the lungs and then it is sent to the left auricle through
pulmonary vein.
3.3.14
Systemic Circulation
Left Ventricle
Capillaries
Venules
Aorta
Artery
Body Cells
Venacava
Arteriole
Capillaries
Right Auricle
This is the circulation which happens between the heart and the other part of our
body through the help of artery and veins.
It starts from the left ventricle. When the left ventricle of the heart contracts,
it pumps oxygenated blood to different parts of the body through aorta, artery,
arterioles, and capillaries. Body cells absorb the oxygen and digested food from the
blood. The carbon dioxide gas and waste products then get excreted into the blood
through diffusion. Then the deoxygenated blood is collected back the right auricle
of the heart through capillaries, venules, veins, and venecava.
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3.3.15
Blood Pressure
The pressure exerted by blood on the walls of the blood vessel is called blood pressure. It depends upon:
1. Flow of blood
2. Size of blood vessel
3. Amount of blood
4. Force exerted during pumping of blood
The two types of blood pressure are systolic and diastolic blood pressure. The device
which is used to measure blood pressure is sphygmomanometer.
The blood pressure exerted during contraction of heart is called systolic blood
pressure. It ranges between 90mmHg and 130mmHg. It is also called arterial pressure. The blood pressure exerted during the relaxation f the heart is called diastolic
blood pressure. It ranges in between 60mmHg and 90mmHg. Its average value is
70mmgHg. The blood pressure of a person depends upon time, mental condition,
age, sex, and physical condition.
A person having blood pressure 120/80mmHg means that the person has 120mmg
systolic blood pressure and 80mm Hg diastolic blood pressure.
Differences between Systolic and Diastolic Pressure
SN Systolic Blood Pressure
1
It is the pressure exerted on the
walls of the blood vessels when
when left ventricle pumps blood
2
Average value: 120mmHg and its
value ranges from 90mmHg to
130mmHg
3
It is exerted when the heart contracts
SN
1
2
3
Causes of High Blood Pressure
1. Regular Smoking
2. Obesity
3. Lack of physical exercise
4. Greater amount of salt in diet
5. Consuming much alcohol
6. Aged more than 40 years
7. Disorder of adrenal and thyroid gland
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Diastolic Blood Pressure
It is the pressure exerted on the
walls of the blood vessels when
ventricles relax
Average Value: 80mmHg and its
value ranges from 60mmHg to
90mmHg
It is exerted when the heart relaxes
8. Genetic disorder
9. Stress
Preventive measures of high blood pressure
1. By avoiding oily food
2. By avoiding smoking and consumption of alcohol
3. By consuming balanced diet in suitable amount
4. By doing physical exercise regularly
5. By managing stress and weight
6. By changing daily life style
3.3.16
Diabetes
The disease caused due to the disorder of the insulin (either failure of proper production or failure to use) which results in high glucose level in blood is called diabetes.
It is caused due to either failure of the pancreas to produce insulin or the failure of
the cells to use insulin.
Symptoms of Diabetes
1. Frequent urination
2. More thirst and hunger
3. Dizziness
4. Unconsciousness
5. Blurred vision
6. Loss in weight
7. Weakness
8. Muscles cramping
9. Slow healing of wounds
Preventive Measures of Diabetes
1. By consuming balanced diet in suitable amount
2. By changing daily life style.
3. By avoiding smoking and consuming alcohol
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4. By doing physical exercise regularly
5. By managing stress
6. By consuming sufficient fruits and vegetables
3.3.17
Uric Acid
The acid produced as the bio-product due to the decomposition of purine found in
cells and diet is called uric acid. Purine is an important chemical substance for our
body because it provides protein to the body and are the building blocks of DNA
and RNA. Uric acid protects the inner part of blood vessels and helps to remove
toxins from the body. In a human body, uric acid is produced due to excessive
metabolism of purine.
Kidney produces uric acid in our body. When kidney fails to function properly.
The removal of uric acid is blocked and its amount in blood vessels increases.
Symptoms of Uric Acid
1. Joint ache
2. Difficulty in walking
3. Red and swollen skin
4. Deep pain in muscles
5. Swelling and burning of skin
6. Swelling of leg joints with pain
Measures to reduce uric acid in blood
1. By drinking sufficient water in less frequency
2. By consuming more baking soda
3. By consuming cherries regularly
4. By avoiding red meat and seafood
5. By providing fiber producing diet
Anthocyanis is found in cherry. At least 10 to 40 cherries should be consumed per
day to control uric acid.
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3.4
3.4.1
Chromosomes and Sex Determination
Introduction
The nucleus it the most important cell organelle as it controls the behavior and
various other functions of the cell. It also takes part in the reproduction of the
cells. A nucleus consists of nuclear membrane, nucleus, nucleoplasm, and a set of
thread-like structures made of DNA and proteins called chromosomes.
Chromosomes are the thread-like structures present in the nucleus of a cell which
contains genetic information of the cell.
Chromosomes are made up of DNA (deoxyribonucleic acid) and proteins. Each
chromosome consists of two strands called chromatids. Centromere or kinetochore
is the structure which joins the two chromatids of a chromosome.
Chromosomes are made from chromatin reticulum. Chromatin reticulum can be
defined as the complex system of threads suspended within a cell which condenses
into chromosomes. They condense into chromosomes during cell division. Likewise,
when in resting state, the chromosomes unwind into chromatid reticulum.
Each species in the world has a fixed number of chromosomes in each cell. The
chromosomes of each species occur in a pair with one part coming from the father
and the other part coming from the other.
Each chromosome of a homologous pair has genes for the same characteristics in
the same place.
Depending upon the position of the centromere (kinetochore) a chromosome can
be divided into four types:
1. Metacentric chromosomes: The chromosome where the centromere is located
in the middle. The two arms are of equal length.
2. Sub-metacentric chromosomes: Here the centromere is located slightly away
from the middle. One arm is slightly longer than the other.
3. Acrocentric chromosomes: Here the centromere is located near the end or tip.
One arm is much longer than the other.
4. Telocentric chromosome: Here the centromere is located at one end. There is
only one pair of arms in this chromosome.
3.4.2
Diploid and Haploid Number of Chromosomes
A cell which has the full number of chromosomes with complete homologous pairs
is called a diploid cell. It is denoted by 2n. All somatic cells are diploid in nature.
A cell which only one set of chromosome for each homologous pair is known as
a haploid cell. It is denote by n. All gametes are haploid in nature. When gametes
fuse together they form a zygote which is diploid in nature because of that gametes
are smaller than the zygote.
All the chromosomes except for the sex chromosomes are called autosomes. Autosomes determine the physical characteristics of an organism whilst the sex chromosomes determine the sex of the organism.
127
The importance of the chromosomes can be summed up in two points:
1. Chromosomes contain genes and hence carry heredity characteristics .
Functions of a Chromosome
1. They are responsible for storing genetic information of an organism
2. They are responsible for transmitting hereditary characteristics, thus they
acting as vehicles of heredity
3. They determine the sex of an individual
4. They bring out variation and help in evolution
5. They help in protein synthesis and metabolism
3.4.3
Number of Chromosomes in Some Organisms
S.N Living Beings
1
2
3
4.
5.
6.
7.
8.
9.
10.
3.4.4
No. of chromosomes in somatic cells 2n No. of chromosomes
in gametes n
Human beings
23 pairs
23
Housefly
12 pairs
12
Gorilla
24 pairs
24
Frog
13 pairs
13
Solanum (Potato) 12 pairs
12
Yeast
1 pair
1
Pine
12 pairs
12
Onion
8 pairs
8
Pea
7 pairs
7
Sugarcane
40 pairs
40
Sex Determination
Chromosomes are made up of genes. Genes are the unit of heredity. Autosomes
control the vegetative characteristics whilst sex chromosomes determine the sex of
an individual. The process of by which the sex of a person is determined is called
sex determination.
XX
X
XX
XY
X
X
XY
Y
XX
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XY
From the figure we can see that: sperm cell having Y chromosome combines with
the egg to have a girl and in the other case there is a boy. Thus it means the chance
of having a male or female is 50/50.
Though in some other animals, sex determination is also controlled by the environmental factors.
3.4.5
Chromosomal Disorder
Chromosomal disorder is defined as the disorder caused due to the increase or the
decrease in the normal amount of chromosomes.
It is caused because of improper cell division. Aneuploidy is defined as the
condition in which there is an improper number of chromosome in a haploid set.
Disease which only affects a particular sex is known as sex linked disease. Some
of them are:
1. Haemophilia
2. Male patterned baldness
3. Uterine Cancer
4. Color blindness
3.4.6
Turner’s Syndrome
It was first described Dr. Herny Turner. It occurs due to the lack of X chromosome.
Thus, it is characterized by 45, OX karyotype. Its symptoms are:
1. Lack of secondary sexual characteristics
2. Poorly developed ovaries
3. Lack of menstrual periods
4. Sterility in females
3.4.7
Down’s Syndrome
It is characterized by 21st pair trisomy. This disorder was first documented by John
Langdon Down. Its major symptoms are:
1. Flat face and small broad nose
2. Protruding tongue
3. Thick palm with creases
4. Lack of physical, mental and psychological development
5. Furrow in tongue
6. Dwarfism
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3.4.8
Klinefelter’s Syndrome
IT is a chromosomal disorder caued due to the addition of one extra X sex chromosome. It is characterized by 47, XXY karyotype. It was documented by Dr. Harry
Klinfelter in 1942 The major symptoms of this disease are:
1. Growth of breasts in males
2. Infertility
3. Tall Stature
4. Small genitals
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3.5
Asexual and Sexual Reproduction
Reproduction is the biological process in which living beings produce their own kinds
asexually or sexually.
There are two types of reproduction:
1. Asexual Reproduction
2. Sexual Reproduction
3.5.1
Asexual Reproduction
The reproduction which takes place without the fusion of a male gamete and a
female gamete is called asexual reproduction. This process is common in primitive
plants and animals.
It is characterized by the following traits:
1. Only one organism can reproduce by this method
2. Gametes aren’t formed
3. Offspring are exactly identical to their parents
4. It is fast
5. Mitosis takes place in this reproduction
Types of Asexual Reproduction
1. Fission
2. Budding
3. Sporulation
4. Fragmentation
5. Regeneration
6. Vegetative Propagation
Fission
Fission is the process of asexual reproduction in which a unicellular organism slits
into more daughter organisms. It is of two types:
1. Binary Fission: Here one unicellular organism divides into two daughter organisms. It is done is favorable condition. This type of reproduction takes
place in diatoms, paramecium, euglena, etc.
131
2. Multiple fission: This method of asexual reproduction in which one unicellular
organisms divides into more than two daughter organisms is called multiple
fission. It is done in unfavorable condition. Here a cyst is formed around the
cell. A cyst is a wall like structure formed when the unicellular organism is in
an unfavorable condition. It is done by plasmodium, chlamydomonas, etc.
Budding
The method of asexual reproduction which takes place with the help of a bud is
called budding. It occurs in: yeast, hydra, etc.
Sporulation
The method of asexual reproduction which takes place by means of spores is called
sporulation. It occurs in : mucor, marchantia, moss, mushroom, fern, etc.
Here, spores are formed inside sporangia. At maturity, sporangia bursts and releases spores on the soil which later germinate and form new plants during favorable
condition.
Fragmentation
Fragmentation is the method of asexual reproduction in which a multicellular organism splits into two or more fragments and each fragments develops into two or
more fragments and each fragments develops into a new organism.
This method of reproduction occurs in: spirogyra, etc.
Here a multicellular organims splits into two or more fragments and each fragment regains its lost body parts and develops into a complete organism.
Regeneration
Regeneration is the method of asexual reproduction in which fragment of an organism regenerates its lost body parts and develops into a complete and new organism.
This method is common in: planaria, hydra, tapeworm, starfish, sponge, etc.
Vegetative Propagation
Vegetative propagation is the method of asexual reproduction in which new plants
are produced from vegetative parts such as roots, stem, and leaf. This occurs in
some flowering plants that don’t produce viable seeds.
Flowering plants like sweet potato, dahila, mint, etc. reproduce asexually by
means of roots.
Flowering plants like potato, onion, rose, sugarcane, garlic, bamboo, banana,
ginger, colocasia, etc. reproduce asexually by stem.
Flowering plants like byrophyllum, begonia, etc. reproduce asexually by leaf.
Advantage of vegetative reproduction
1. It is easy and fast
2. The offsprings are identical to the parents
132
3. Some plants don’t produce viable seeds (potato, rose, sugarcane, etc.) so this
method makes it much easier to propagate them
4. The flowering plants produce by this method start bearing flowers and fruits
earlier than those reproduced from their seeds
5. A large number of flowers and fruits can be produced through this method
6. Species of rare and endangered plants can be reproduced by this method
3.5.2
Sexual Reproduction
The method of reproduction which takes place by the fusion of a male gamete and
female gamete is called sexual reproduction.
Animals that only produce one gamete are known as unisexual animals. Animals that produce both gametes are known as bisexual or hermaphrodite animals.
Example: hydra, tapeworm, liverfluke, earthworm, etc.
Flowering plants have unisexual and bisexual flowers. Pumpkin, cucumber, papaya, etc. produce unisexual flowers whilst mustard, pea, tomato, orange, etc.
produce bisexual flowers.
3.5.3
Sexual Reproduction in Plants
A bisexual flower consists of four whorls.
1. Calyx: It is the outermost whorl. It consists of green leaf like structures called
sepals. It protects the flower during its bud state and assists in photosynthesis
2. Corolla: It forms the second whorl and consists of colorful and attractive structures called petals. It protects the flower’s reproductive organs and attracts
pollinators
3. Androceium: It forms the third whorl of the flower. It consists of a group of
male reproductive organs called stamens. Each stamen consists of a filament,
connective, and an anther. Anther consists of four pollen sacs which forms
haploid pollen grains through the microspore mother cells. Pollens are fine
powdery structures possessing the male gamete
4. Gynoecium: It forms the innermost (forth) whorl of the flower. It consists
of one or more female reproductive organs called carpels or pistils. Each
carpel/pistil consists of three distinct parts. They are stigma, style and ovary.
The uppermost spreading part of a pistil is called a stigma. The middle cylindrical part is called a style and the lowermost swollen part is called a ovary,
at full maturity it produces ovules.
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3.5.4
Pollination
The transfer of pollen grains from the anther to the stigma of the same flower or
different flower is called pollination. There are two types of pollination
1. Self-Pollination: Transfer of pollen grains within the same flower. Common in
bisexual plants
2. Cross-pollination: Transfer of pollen grains from one flower to another. It is
common in unisexual plants.
3.5.5
Fertilization
The process of fusion of a male gamete and a female gamete to form a zygote is
called fertilization.
In a flowering plant, after pollination, pollen grains germinate and form pollen
tubes which grow towards ovary through style to finally reach ovule through a micropyle.
After entering into ovule, the pollen tube enters into the embryo sac. In the
embryo sac three antipodal cells, two synergids, a female gamete or egg cell and a
diploid secondary nucleus are formed. When the pollen tube enters embryo sac, the
apex of the tube dissolves and two male gametes are released. Fertilization then
occurs. The first one makes the zygote and the second one fuses with secondary
nucleus (zygote) and forms endosperm nucleus. This process is called triple fusion.
The nature of the fertilization in flowering plants is thus called double fertilization
as it involves the fusion of two male gametes separately.
3.5.6
Sexual Reproduction in Animals
The process by which gametes are formed is known as gametogenesis. In animals
fertilization occurs in two types:
1. Internal Fertilization: Where gametes fuse together within the body
2. External Fertilization: Where gametes fuse together outside the body
Advantages of Sexual Reproduction
1. It gives continuity to the generation of a species
2. It brings out variation
3. It helps in the evolution of the organism
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3.5.7
Artificial Vegetative Propagation in Plants
The method of propagating (reproducing) plants artificially through the method
vegetative propagation is known as artificial vegetative propagation.
Some common methods are:
1. Layering
2. Grafting
3. Tissue Culture
3.5.8
Layering
Layering is the method of artificial vegetative propagation where new plants are
obtained in the stem of parent plants.
The different types of layering are:
1. Simple Layering: It is the method of layering where a long and flexible stem
aged more than a year is burred in the soil about 20cm away from its tip.After
2 to 3 months, the buried portion develops roots and a new planet is created.
It is done in lemon, citrus, etc.
2. Compound Layering: It is the type of layering where the entire flexible stem is
buried in the soil. The nodes of the stem produce plants. It is done in walnut,
apple, pear, etc.
3. Air Layering: Here, the bark of the stem of around 2 years is removed in the
shape of a ring. Then the portion of the stem is covered with moist soil and
cloth. Then IBA hormone is administered to enhance the growth of the roots
in the stem, the portion can also be covered with moss and plastic to make it
air proof. The covered portion then develops root within 1 to 2 months. This
is applied in lemon, orange, peach, plum, etc.
4. Tip Layering: The tip of the plant is bent and buried in the soil to grow roots.
The tip develops roots within 2 to 4 months. This method is applied in plants
like raspberry, blackberry, etc.
5. Stool Layering or Mound Layering: Here, the selected plant is cut at the height
of 5 to 10cm from the ground. Then the plant produces many branches. When
these branches grow to a certain height (20 to 25cm), stem is covered with soil
or saw dust with upto height of 10 to 15 cm and watered regularly. These
branches develop roots within 3 to 4 months. This method is used in plants
like mango, guava, apple, peach, plum, etc.
135
3.5.9
Grafting
Grafting is the method of artificial vegetative propagation in which shoot system of
one plant is combined with root system of another planet.
The plant whose root system is used is called stock and similarly the plant whose
shoot system is used is called scion.
Types of grafting:
1. Whip Grafting: In this method the scion and stock of closely related plants
are cut obliquely the length of the portion should be 3 to 5cm. Then both the
stock and scion are combined together and sealed with a tape. Then after 3 to
4 months both stems combine together. This method should be done before
spring season.
2. Cleft Grafting: Cleft grafting is the method where the stock is cut and split
down the middle making a cleft about 5 to 8cm deep. The end of the scion
should be cut slanted in the shape of a wedge and inserted into the cleft. The
portion is sealed with a tape which makes it air tight. They combine within 2
to 3 months.
3. Tongue Grafting: Here a tongue like deep structure (about 3 to 5cm) is cut
into scion and stock. Then they are joined together. The join is sealed with a
tape or plastic until they combine firmly. If they remain undisturbed and air
tight, they both combine within 2 to 3 months.
3.5.10
Tissue Culture
The method of propagation of new plants from cell, tissue, or organ of a parent,
keeping them in a culture solution culture is called tissue culture. It is done for the
following reasons:
1. Exactly identical plants to the parents can be produced by this method
2. A large number of new plants can be produced within a short time
3. The plants which do not produce viable seeds can be propagated by this
method
4. Disease free plants can be produced
5. Hybrid plants of desired quality can be produced
6. Endangered plants can be reproduced
Method of tissue culture
An artificial medium is prepared for tissue culture called the culture solution. It
consists of nutrients and plant hormones.
136
A small lump called the calus is kept within the culture solution under sterile
condition. The callus gets nutrients and hormones (auxin and cytokinin) and develops roots and shoot. As auxin enhances the growth of the roots and cytokinin
enhances the growth of the shoot.
Then the callus is cut into several tiny plantlets which are then planted into the
soil.
137
3.6
Heredity
Heredity can be defined as the phenomenon where the parental characteristics are
transmitted to their offspring.
Heredity is done through genes, which are also known as the functional unit of
heredity. They are located within the chromosomes. Each gene is a segment of DNA
(deoxyribonucleic acid) which is capable of copying itself through a process called
replication.
Genes determine the physical, anatomical, and physiological nature of the organism. They determine their sex and all their other physical characteristics.
Genes are of two types:
1. Autosomes: Physical or morphological characteristics
2. Sex Chromosomes: Sex of the organism
There are a lot of genes within a chromosomes.
The characteristics which are transmitted from parent to progeny are known as
hereditary characteristics.
3.6.1
Terminology Related with Heredity
Allele: An allele can be defined as a form a gene or a pair of matching genes.
Homozygous or Pure Organisms: An organism having two identical pairs
of alleles for a particular characteristics.
Heterozygous or Hybrid Organisms: An organism have different pairs of
alleles for a particular characteristics
Phenotype: It is simply defined as the external appearance of an organism
Genotype: It can be defined as the genetic makeup of the organism
Dominant Characteristics: The characteristics which appear in successive
generation
Recessive Characteristics: The characteristics which remain hidden in successive generations
Monohybrid Cross: The cross between two pure organisms
Dihybrid Cross: The cross between two pairs of contrasting or different
characteristics
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3.6.2
Mendel’s Experiment
The branch of biology which deals with the study of genes is known as genetics.
Gregor Johann Mendel is known as the father of genetics as he was the first person
to study about it. He propounded the law of inheritance after doing his experiments.
Mendel experimented with common garden pea (pisum sativum) to prove that
hereditary characteristics transfer from parents to their offspring. He selected pea
plants for his research because of the following reasons:
1. Pea plants have short life span and can be grown easily
2. Pea plants are bisexual thus they are self-pollinating as well as the fact that
cross-pollination could be done when necessary
3. The hybrids produced fertile progeny
4. Pea plants are available in a number of contrasting characteristics
Mendel selected seven pairs of pea plants having contrasting characteristics.
S.N
1.
2.
3.
4.
5.
6.
7.
Characters
Position of the flower
Height of Plant
Shape of Seed
Color of Seed
Color of seed coat
Shape of pod
Color of Pod
Dominant Characters
Axial (A)
Tall (T)
Round (R)
Yellow (Y)
Brown (B)
Inflated (I)
Green (G)
(Parents)
TT
T
(Gametes)
(F1 )
Tt
(F2 )
tt
T
t
Tt
(Gametes)
T
TT
Recessive Character
Terminal (a)
Dwarf (t)
Wrinkled (r)
Green (y)
White (b)
Constricted (i)
Yellow (g)
t
Tt
t
Tt
T
tt
Tt
t
Tt
The above chart shows the crossing between pure tall and pure dwarf pea plant till
F2 generation. Here T T is pure tall, tt is pure dwarf. T t is hybrid tall and as we
know tall is a dominant trait so T t has the tall phenotype. With all these we can
say that the genotypic and phenotypic ratio the following is: 1:2:1 and 3:1. Same
case follows for other crosses as well.
139
3.6.3
Law of Inheritance
These were the laws propounded by Mendel after his experiments. Though these
laws were figured out from pea plants. They are applicable for all lifeforms that
reproduce sexually. There are three laws:
1. Law of Dominance
2. Law of Segregation or Law of Purity of Gametes
3. Law of Independent Assortment
Law of Dominance
Law of dominance states that: ”When a cross is made between a pair of pure
contrasting characters, only one of them is able to express itself phenotypically
while the other remains hidden in the generation.”
For example, taking a cross between a pure black guinea pig and pure white
guinea pig we can see:
(Parents)
BB
B
(Gametes)
(F1 )
Bb
(Gametes)
(F2 )
B
b
Bb
B
BB
bb
b
Bb
b
Bb
b
Bb
Bb
B
bb
We know that black is dominant and white is a recessive trait so in F1 every single
progeny is black and in F2 we can find the phenotypic ratio of 3:1 of black to white.
Guinea pigs were taken for this as:
1. They are easy to raise
2. They have a short life-cycle
3. They contain many pairs of contrasting characteristics
Like with peas and guinea pigs, humans also have dominant and recessive trait. Few
of them are:
Dominant Characteristics Recessive Characteristics
Curly Hair
Non-curly hair
Free ear-lobe
Attached earlobe
No Hitcher’s thumb
Hitcher’s thumb
Rolling tongue
Non-rolling tongue
Bending thumb
Straight thumb
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Law of Segregation or Law of Purity of Gametes
Law of segregation states, ”Individual alleles separate during gamete formation.”
This means that when the gamates aren’t the genes keep their independent existed
and don’t mix.
It can be shown using a chart consisting up to F2 generation.
(Parents)
BB
B
(Gametes)
(F1 )
Bb
(Gametes)
(F2 )
3.6.4
B
b
Bb
B
BB
bb
b
Bb
b
Bb
b
Bb
Bb
B
bb
Variation
Variation can be defined as the morphological or physical change in an organism
caused due to genetic or environmental effects. There are two types of variation:
1. Hereditary Variation
2. Environmental Variation
Hereditary variation
It is the variation caused by the transfer of hereditary characteristics from parent to
child. This type of variation is only possible in creatures which reproduce sexually.
Miosis cell division occurs during gaemete formation which plays a vital role to
bring out hereditary variation.
This type of variation is caused when two gametes having different characteristics combine together as it leads to genetic variation.
Environmental Variation
This type of variation is caused due to the environmental effect on an organisms.
This causes the offspring produced from the parents to exhibit different characteristics.
3.6.5
Continuous and Discontinuous Variation
Hereditary and environmental Variation both have continuous and discontinuous
variation.
The gradual changed caused through the transfer of hereditary characteristics to
offspring as well as the change caused due to normal adaptation to the environment
is called continuous variation.
141
The sudden chromosomal change where extremely new characters are seen in the
offspring is called discontinuous variation, it is also known as mutation.
These were first proposed by the Dutch Zoologist Hugo De Vries.
The cause of mutation is due to the effect of various chemicals and harmful
radiation such as UV-ray, X-ray, gamma ray etc.
Examples of mutation are: man having six fingers, a boy with tail, etc.
142
3.7
3.7.1
Environment and Pollution
Introduction
Environment pollution refers to the addition of various harmful substances or pollutants/contaminants which cause an overall degradation in the quality of the environment.
Due to the decrease in the quality of the environment, various problems relating
to health, climate, population, etc. occur which have devastating consequences.
3.7.2
Air Pollution
Air pollution can be defined as the addition of harmful pollutants into the air that
causes the air to be filled with dangerous substances causing damages to biotic as
well as abiotic componenets. In simpler words, it can be defined as the addition of
harmful pollutants into the air.
There are two kinds of air pollutants:
1. Primary Air Pollutants: These can be defined as the pollutants which are
immediately released into the atmosphere. Examples of it are: carbon dioxide,
sulpher, methane, etc.
2. Secondary Air Pollutants: These can be defined as the pollutants created due
to the combination of two or more primary pollutants. Examples include:
formaldehyde, peroxyl, acetile nitrates, etc.
The major causes of air pollution are as follows:
1. Dust and smoke emitted from industries, construction, and domestic activities
2. Burning of biomass
3. Stench produced through rotten materials
4. Emission of smoke from vehicles
The place or source through which air pollutants are released are known as sources
of air pollution. There are two types of air pollution:
1. Natural Sources: These sources are naturally formed sources of air pollution.
Their examples are: volcanic eruption, forest fire, etc.
2. Artificial Sources: The sources of air pollution formed because of humans.
Examples: industries, factories, vehicles, etc. The pollutants released from this
source are: carbon dioxide, nitrogen oxide, nitrogen dioxide, sulpher dioxide,
etc.
There are various effects caused by air pollution, some of them are:
143
1. Reduction of visibility: Due to the mixing of various particles (such as dust
and smoke) the atmosphere becomes cloudy and visibility is reduced
2. Reduction of solar radiation: The pollution clouds the skies and absorbs the
radiation before it reaches the surface
3. Greenhouse effect: Greenhouse gases are one pollutants released by various
source of air pollution, these gas trap the solar radiation within the surface
causing the global temperature to gradually rise
4. Inhibition of biological growth: Plants require water, sun, and carbon dioxide
to properly grow. Due to air pollution, solar radiation is lowered which causes
the stomatas of the plants to not fully open which causes them to get less
carbon dioxide thus lowering their growth.
5. Adverse Impact on Human Health: Air pollution harms humans by making us
breathe in harmful substances which can cause various diseases and even lead
to death
6. Depletion of Ozone Layer: Some of the dangerous gases released from air pollution can end up reacting with ozone and destroying the protective covering
of ozone in the stratosphere.
7. Acid Rain: Various chemicals react with water in the atmosphere to form acids
which then later rains down on the ground. This rain devastates crops and
harms life.
8. Destruction of Historical Monuments
9. Change in Climate: This can be defined as the change in the usual pattern
of the climate and weather. It is caused by the influx of various greenhouse
gases and other harmful pollutants.
We can control air pollution by doing the following:
1. Establishment of industries far from human settlement
2. Proper management of wastes produced from factories, industries, etc.
3. Controlling rapid population growth
4. Generating awareness about the cause, effect, and mitigation of air pollution
5. Using alternative sources of energy
6. Stopping or at least reducing the production of harmful gases
7. Afforestation and reforestation programs
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3.7.3
Water Pollution
Water pollution can be defined as the addition of various contaminants or pollutants
into water bodies which has harmful effects on the environment.
Like air pollution, there are natural and artificial sources of water pollution.
But man-made sources are the more major causes thus it is the most pressing issue.
Some of the main artificial causes of water pollution are:
1. Sewage Water: The improper management of sewage water leads it various
bodies of water. Due to the presence of various dirty materials, it pollutes the
water and causes it to be filled with diseases.
2. Contaminated water from industries: Various chemicals are used in industries.
Various reactions produce unwanted byproducts. Due to improper management of those byproducts, they end up finding their way into rivers or other
bodies of water. This devastates the biodiversity of the lakes due to the presence of various kinds of harmful chemicals.
3. Agricultural wastes: Due to the overuse chemical fertilizers, some of the chemicals find their way into rivers through various natural processes. This causes
the ecosystem to be unbalanced due to the mass death it causes in the animal
population
4. Obstruction of flow of water
5. Spilling of oil in water resources
6. Heat: Due to the dumping of heat and energy into the water, various aquatic
animals are destroyed
7. Radioactive Substances: The nuclear produced by countries can find their way
into water bodies which causes water pollution.
Some measures to control water pollution are:
1. Proper management of the sewage system such that no waste ends up polluting
the water
2. Properly disposing of various rotten materials
3. Maintaining sanitation
4. Afforestation around water bodies
5. Managing nuclear wastes
6. Generating awareness regarding water pollution
7. Making proper laws and policies to stop and discourage water pollution
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3.7.4
Land/soil pollution
The degradation in the original quality of the soil due to the addition of harmful
particles etc. is known as soil pollution. It is caused by:
1. Domestic Waste: Improper disposing of domestic wastes causes the land to be
polluted as many wastes can’t be decomposed
2. Excessive use of pesticides: The harmful chemicals harm the soil
3. Excessive use of chemical fertilizers
4. Industrial wastes: Improper management of industrial wastes
5. Municipal Waste: The rapid urbanization and population growth causes a lot
of waste to be produced
6. Acid rain: It destroys plants and causes the acidity of the soil to rise
Measures to control soil pollution are:
1. Reduction in the use of pesticides
2. Reduction in the use of chemical fertilizers
3. Proper management of wastes
4. Various policies against soil pollution
5. Control of rapid population of growth and urbanization
6. Spreading awareness regarding soil pollution
3.7.5
Conservation and Management of Forest
Forests are important for the ecosystem. They serve as habitats of animals and give
us various kinds of resources. Furthermore, they help to control climate change.
Thus conservation and management of forests is an important task, it can be done
so by doing the following:
1. Proper use of the forests
2. Control and putting mitigation in place for forest fires
3. Implementation of laws for the conservation of forests
4. Afforestation and Reforestation
5. Spreading awareness
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3.7.6
Conservation and Management of Water Sources
Water is too an important resource. It serves as the medium where various ecosystems thrive in. Furthermore, it is also responsible for various resources. Thus,
conservation and management of this resource is a very important task. It can be
done so by doing the following:
1. Generating awareness
2. Proper distribution of water
3. Proper deposition of water
4. Proper management of wastes to not pollute water
5. Formation and implementation of laws concerned with water pollution
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Chapter 4
Geology and Astronomy
4.1
4.1.1
History of the Earth
Introduction
Earth is about 4.55 billion years old. There were several hypothesis about its formation. Some of them are:
1. George Wofan Hypothesis (Old Planetesimal hypothesis)
In 1745, George Wofan put forward a theory of origin of the earth. His hypothesis states that a coment moving around the universe crashed with the
sun, thus splashing matter from the sun around causing the formation of the
other heavenly bodies of the solar system
2. Nebular or Kant Hypothesis
In 1755, the German philosopher Kant proposed another hypothesis. It states
that the entire solar system formed from a nebula (a large mass of gas and
dust). It was stated that due to gravitation, particles of the nebula started
to get collected at different places. Large mass collected at the center of the
nebula which became the sun and the other small masses that were revolving
around the large mass became the planets, asteroids, satellites, etc. In 1796,
Laplace modified the hypothesis. According to him, the nebula started to
gradually cool which resulted in the decrease of size and volume. The center
started to spin faster and faster and accumulate more mass. The rest of the
mass formed rings around the center and revolved about it.
3. Tidal or Jean and Jaffery Hypothesis
In 1919, Jean and Jaffery proposed a hyptothesis about the formation of the
earth. According to this hypothesis, a large body of mass passed through the
solar system. The force of gravitational attraction between the sun and the
large body of mass caused various tidal effects which resulted in some mass
getting ejected out from the sun which later formed the remaining heavenly
bodies
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4.1.2
Statistics on Earth
1. Estimated age: 4.55 billion years
2. Mass: 6 × 1021 metric tons
3. Total Surface Area: 509,700,000km2
4. Land Area: 148,400,000km2
5. Water Area: 361,300,00km2
6. Highest Land: 8848m (Mt. Everest)
7. Lowest Land: 399m (Dead Sea)
8. Average Density: 5.5gm.cm−3
9. Number of satellite: 1 (Moon)
4.1.3
Geological Time Scale
Geological time scale is the time scale which is used to describe the scale of time in
earth. It is divided into eons, eras, periods, and epochs which eons lasting for the
longest and epoch lasting for the shortest.
In the whole geological timescales there are four eras.
1. Cenozoic Era
2. Mesozoic Era
3. Paleozoic Era
4. Precambrian Era
4.1.4
Precambrian Era
Precambrian era began about 4.5 billion years ago and ended 570 million years ago.
It is actually the combination of Archezoic (Archean), Proterozoic, and Eozoic era.
The major events of this area are:
1. Metamorphic rocks were formed from igneous rocks
2. Formation of atmosphere, hydrosphere, and lithosphere took place
3. Unicellular and multicellular organism evolved
4. Very primitive bacteria evolved
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4.1.5
Paleozoic Era
Paleozoic era began 570 millions years ago and ended 250 million years ago. Different
terrestrial plants developed in this era so this era can be termed as the era of big
ferns. Major events of this era were as follows:
1. Sedimentary rocks were formed
2. Climate change and change in atmosphere took place
3. Aquatic and terrestrial vertebrates and invertebrates evolved
4. Different bryophytes and pteriodophytes were evolved
4.1.6
Mesozoic Era
This era began 250 million years ago and ended around 65 million years ago. The
era was dominated by giant reptiles like dinosaurs. Thus it is also called the era of
reptiles.
1. Hills and mountains were formed
2. Climate became suitable for aquatic, terrestrial, and aerial animals
3. The giant reptiles like dinosaurs evolved, flourished and were extinct
4. Coniferous plants were developed
5. Flowering plants were developed
6. Mammals began to evolve at the end of this era
4.1.7
Cenozoic Era
Cenozoic era began 65 million years ago and is still going on. This era is known as
the era of mammal. Or the era of human beings. Human dominance began in this
era.
1. Expansion and breaking down of rocks took place
2. The temperature of the earth decreased and the climate changed drastically
3. Mountains were covered with snow due to the decrease in temperature
4. The process of extinction of ancient animals and plants and evolution of new
animals and plants continued in this era
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4.1.8
Evolution of Life
The earth formed 4.55 billion years ago. But at period of time, the temperature
wasn’t suitable for any living creature. Then it slowly cooled down. Water vapor
started to condense in the atmosphere and rain fell upon the earth. Seas were thus
formed (almost 4.4 billion years ago). The surface was still hostile so the only place
for the formation of life was in the ocean. There 3.8 billion years ago, the first
unicellular bacteria developed and 3.2 billion years ago the first algae developed.
In Archean era no life had evolved because no sedimentary rocks were formed. In
Proterozoic era, unicellular organism were evolved and (few) multicellular organism
were developed later. In Paleozoic era, lots of changes in the climate took place
which made the terrestrial environment habitable as well as the aquatic animals.
Thus the first fishes, amphibians and some reptiles evolved. In Mesozoic era, giant
reptiles and toothed birds evolved. Lastly, in Cenozoic era mammals evolved.
4.1.9
Fossils
The impression of either a part or the entirety of the body of animals or plants on
sedimentary rocks which were buried in the earth crust over a long period of time
are called fossils. The branch of science which deals the study of fossils is known as
paleontology.
4.1.10
Formation of Fossils
Fossils are formed only in the sedimentary rocks because the formation of fossils and
sedimentary rocks take place simultaneously.
Fossils are formed when a plant or animal dies and their corpse is quickly buried
underground. As the layer of soil keeps on increasing and increasing various physical
and chemical changes start to occur. Due to these changes, fossils are formed.
4.1.11
Identification of Fossils
Fossils are identified by studying the impressions left on the rocks. Furthermore,
these identifications are then compared and contrasted with others whilst getting a
more in-depth look into the morphological structure of the fossil’s specimen.
In short, the ways of identify a fossil can be enumerated below:
1. Identifying the impression left on rocks
2. Comparing and contrasting excavated fossils with known fossils
3. Studying the morphological structure of fossils
4.1.12
Importance of Fossils
1. The study of fossils helps to propose and construct the process of evolution of
living organism
151
2. The study of fossils gives information about the location of coal and petroleum
mines
3. It helps to discover the geological history through the study of the rock’s age
4.1.13
Fossil Fuels
The fuels formed from the buried plants and animals which undergo immense physical and chemical change due to the extreme heat and pressure are called fossil fuels.
Coal, petroleum and natural gas are the most important fossil fuels.
1. Coal
Coal is the fossil fuel derived from ancient plant fossils.
Formation
Those ancient plants which got buried quickly or immediately after they died
formed the fuel. This is because as more soil started to compress them from
above, the temperature started to rise and they were put under even more pressure. They were protected from bio-degradation and oxidation. This process,
i.e., the conversion of plants into coal because of high pressure and temperature is called carbonization.
Importance
(a) It is used to produce electricity and heat
(b) It is used in railway transportation, industries, brick factories, etc.
(c) It is used for the manufacture of organic compound like benzene, phenol,
etc.
2. Mineral Oil (Petroleum)
It is a dark colored viscous liquid which has a bad odor. 90 to 95% of it is
composed of hydrocarbons whilst the rest is oxygen, nitrogen, sulphur, etc. It
is the remains of plants and animals (phytoplankton and zooplanktons).
Formation of mineral oils
When phytoplankton and zooplankton were buried under the ocean the process of mineral oil formation took place. Due to various geological activity
they were crushed whilst also being put under high pressure. This creates
mineral oil.
Importance of mineral oil
As raw mineral oil is is crude it is subjected to fractional distillation. This thus
creates petroleum gas, petrol, kerosene, etc. Also, the byproduct of the process is used for the production of various other important organic compounds.
The usage of such is:
152
S.N
1.
2.
3.
4.
5.
6.
7.
8.
Components of Crude Oil Uses
Petroleum Gas
To make LPG
Petrol
Fuels for automobile
Naptha
To make chemicals
Kerosene/paraffin oil
Fuel for jets, aircrafts, stoves
Diesel
Automobile fuel
Lubricating Oil
For lubricants, waxes, polishes
Heavy fuel oil
Fuel for ships, factories
Residue (tar)
Bitumen for roads and roofs
Note: LPG gas is normally odorless thus ethyl meracaptan is used to give it its
distinctive odor to know when there is a gas leak
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4.2
4.2.1
Climate change and Atmosphere
National Efforts to minimize the effects of Climate
Change
1. National Communication Report: Nepal has submitted the initial national communication report to the COP (Conference of the Parties) of UNO
protocol.
2. Climate Change Policy, 2067
3. Climate Change Adaptation Strategic Programme: Nepal was invited
by climate investment fund, in the year 2009 to participate in the global model
progamme related to the adaptation to the climate change. The model program provides economic backing. The programme of Nepal has been divided
into five sectors:
(a) Climate Change Adaptation of Watersheds of Hilly Regions
(b) Adaptation to Risk Induced by Climate Change
(c) Develop Capable Community for Climate Change Adaptation by the initiation of local sectors
(d) Promotion of Endangered Species for Climate Change Adaptation
(e) Main Stream Flow of the Risk Management of Climate Change in Development Projects
4. National Adaptation Program: It was prepared in the year 2010 by the
Government of Nepal. It it has 250 programmes integrating into 9 different
sectors.
5. Local Adaptation Program: It is designed for the implementation in the
local level. It prepared and coordinates local and national level programs. It
conducts programs to minimize the impacts of climate change at the local level
to provide necessary services to the endangered communities. It includes four
theories while selecting process o climate adaptation:
(a) Progressive
(b) Inclusive
(c) Capability
(d) Flexibility
6. Other Programs: Improved chimneys of brick factories, improved stove, use
of biogas, pre-information system about natural disasters etc.
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4.2.2
International Efforts to minimize the effects of Climate Change
1. The United Nations Framework Convention on Climate Change
(UNFCCC): UNFCCC was held in the year 1992 in Rio de Jenerio. There
were 154 countries in this programme. The conference addressed envionmental
pollution, sustainable development programme etc.
2. UN Climate Change Conference: The UN conference on climate has been
conducted 19 times till 2013AD. Nepal prepared and implemented the climate
change policy-2011 on the basis of UNFCCC 1992. The conference’s goal was
awareness about the problem.
3. Agenda 21: The action plane formulated on the basis of the slogan ”Think
Globally and Act Locally” to conserve environment and ensure sustainable
development.
4. Intergovernmental Forum: It was established in the year 1988AD. It prepares report to support the UNFCCCC. It consist of scientific, tecnical, and
soic-economical information to understand the risk o human caused to climate
change and also its mitigating measures.
5. Kyoto Protocol: It was adopted in December 1997AD. Its main object is to
reduce climage change and production of green house gases to control global
warming. The protocol makes 36 developed countries of the world to reduce
the emission of GHG by 5.25% by 2012AD from their industries. The provision
is now extend for 2020AD by the convention held in 2012AD at Doha.
It encouraged developed and developing countries to work under three market
level mechanisms to meet their GHG emission target. They are international
emission trading, join implementation, and clean development mechanisms
6. Reduction of Emission due to Deforestation
4.2.3
Atmosphere
The layer of air surrounding the earth is called the atmosphere. Air is a mixture of
various gases. The major gases of the atmosphere are:
1. Nitrogen: 78%
2. Oxygen: 21%
3. Argon: 0.9%
4. Carbon Dioxide: 0.03%
5. Other gases
There are five layers of the atmosphere:
155
1. Troposphere
It is the lowermost part of the atmosphere. It extends 8 to 10 kilometers at
the pole and upto 16km at the equatorial region. It contains oxygen, nitrogen,
carbon dioxide, water vapor etc.
95% of the entire atmosphere’s mass is present here. The uppermost layer
is called the tropopause. The temperature of this layer decreases by 6.5◦ C
per km with the rise of altitude from the earth’s surface. This layer is highly
affected by human activities
Troposphere is also called changeable layer as its parameters (temperature,
humidity, wind speed and direction) are continuously changing.
2. Stratosphere
Stratosphere extends from 16km to 50km. The major gas of this layer is ozone
which is a useful gas which protects the planet from highly dangerous UV
bombardment. The tempreature increases in this region.
3. Mesosphere
It extends 50 to 80km. It is the coldest layer with temperature getting as low
as −109◦ C. The temperature decreases with the increase in altitude.
4. Thermosphere
It extends from 80km to 720km. The density of this layer is very low. It
experiences great solar radiation thus this layer rises in temperature as you go
higher. Due to the presence of ions in this region, this region is also called the
ionosphere.
5. Exosphere
The last layer of the atmosphere which extends beyond 720km. This layer is
called the fringe layer. Due to the weakened gravitational attraction, molecules
drift towards space.
4.2.4
Ozone Layer
Ozone layer is the layer present in the stratosphere. It it is made up of three atoms
of oxygen. It is formed because of UV rays breaking an oxygen molecule into nascent
which then combines with an oxygen molecule to form ozone.
UV rays
O2 −−−−→ O + O
UV rays
O2 + O −−−−→ O3
The ozone also breaks down due to UV rays.
UV rays
O3 −−−−→ O2 + O
UV rays
O + O −−−−→ O2
156
This process of decomposition and formation balances the level of ozone in the
layer.
The layer extends from 25km to 40km from the surface. It absorbs 99% of the
ultraviolet rays. Protecting us from disease like blindness, skin cancer, etc. and Due
to its protective nature on all lifeforms, it is also termed as the protective layer.
Ozone also forms on the troposphere starting from the height of 12km but the
production level is low.
4.2.5
Depletion of Ozone Layer
The gradual formation of hole or the gradually thinning within the ozone layer is
called the depletion of ozone layer. It is caused due to the entry of chemicals like
chlorofluorocarbons, methyl cholorofmr, carbon tetrachloride etc.
CFCS are the major chemcials which deplete the ozone layer. They were first
discovered by T. Midgely in 1928 Ad. These are non toxic, non inflammable, and
cheap chemical which is used as refrigerant.
These chemicals go up into the atmosphere and react with ozone, breaking into
chlorine oxide and oxygen. The ozone hole was first observed above Antarctica
above 1885 AD for the first time.
UV rays
CF Cl3 −−−−→ CF Cl2 + Cl
UV rays
Cl + O3 −−−−→ ClO + O2
UV rays
2ClO −−−−→ 2Cl + O2
UV rays
Cl + CF Cl2 −−−−→ CF Cl3
A single CFC molecule can destroy over one hundred thousand ozone molecules.
Effects of depletion of ozone layer
1. Harmful ultraviolent rays reach the surface which causes cataract, skin burns,
skin cancer, etc to the human beings.
2. The ultraviolent rays hinder plant growth
3. It causes more solar radiation to reach the earth causing it to heat up further
4. It causes disorder in the ecosystems
Ways to protect the ozone layer
1. Banning of CFC usage
2. Alternative sources of energy like solar energy, bio gas, and hydroelectricity
should be used
3. We must reduce the excessive use of nitrogen fertilizers
4. We should encourage the use of hydroflurocarbons instead of CFCs
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4.2.6
Industrial Gases
The various harmful gases like carbon dioxide, carbon monoxide, sulphur dioxide,
nitrogen oxide, etc. which are produced by industries are called industrial gases.
The pollution caused by these gases are termed as industrial pollution.
When these gases reach to the atmosphere, they react with rain water and form
acids.
4N O2 + H2 O + O2
SO2 + H2 O
2SO2 + O2
SO3 + H2 O
−→ 4HN O3
−→ H2 SO3
−→ 2SO3
−→ H2 SO4
Effects of Industrial Gases
1. Various gases like SO2 , SO3 , N O2 , etc. reacth with rain water and forms acids
2. Industrial gases cause dizziness, headache, eye problem, chest pain, lung cancer, bronchitis, asthma etc. to the human beings.
3. Carbon monoxide causes disturbance in the oxygen transport mechanism of
blood circulation
4. Oxides of nitrogen also deplete the ozone layer as:
N O + O3 −→ N O2 + O2
2N O2 + O3 −→ N2 O3 + 2O2
5. Accumulation of large amount of carbon dioxide in the atmosphere causes
global warming
158
4.3
Earth and the Universe
The universe can be defined as the vast and unlimited space which contains all mass
and energy.
4.3.1
Solar System
The celestial bodies which revolve around the sun and the sun itself form the solar
system.
There are eight planets in our solar, their satellites/moons, thousands of smaller
heavenly bodies, etc. Every single one of them revolves around the sun in their own
orbit due to gravitational force acting upon them.
The solar system lies 3×104 light years away from the center of the Milky Way
Galaxy.
4.3.2
The Sun
The sun is the medium-sized star found at the center of the solar system. It is the
greatest mass in the solar system. Weighing 770 times more than every other mass
in the system combined.
It produces tremendous amount of heat due to the nuclear reactions going on in
its core which also causes it to release massive amount of radiation in the form of
visible, infrared, ultraviolent, xrays, etc.
It also blows winds of charged particles all around at very high speed (500km.s− 1)
carrying adequate amount of heat and electrostatic energy.
The sun is mostly hydrogen gas which it uses to create helium through the
process of fusion, generating tremendous energy.
4.3.3
Planets
Planets are named after ”wanderer” as they keep on moving.
The massive heavenly body which orbits the sun is called a planet. Planets don’t
produce light but rather reflect the light of the sun. There are eight planets in our
solar system.
The planets which lie inside the asteroid belt are called inner plants, all the inner
planets are also terrestrial planets. But the planets which lie outside are called outer
planets all of them are gas giants.
The rocky belt of asteroids and other debris between the orbit of Mars and
Jupiter is called the asteroid belt.
All planets in the solar system except Mercury and Venus possess a satellite
which are the heavenly body revolving around a planet.
Each planet differ by their size, surface temperature, orbits, etc.
1. Mercury (Budha)
It is the smallest, closest and the fastest revolving planet from the sun. It is
159
extremely dim int he sky and can only see at the horizon just before sunrise
and sunset.
Its distance from the sun and the earth is 5.8×107 km and 9.15×107 kilometer
respectively.
Its diameter is 4,851km.
It is extremely hold in the and cold in the night. During the day its surface
temperature reaches 427◦ C and at night -170◦ C.
Its rotation period is 59 days and revolution is 59 and revolution period is 88
earth days.
2. Venus (Sukra)
It is the brightest, hottest, and closest planet to the earth.
Due to its size and mass it is considered to be earth’s sister planet.
Early in the morning, it can be see on the eastern sky whilst in the evening
it can be see in the western part. Due to its brightness in the sky, it is also
called morning/evening star.
Its distance from the earth and the sun is: 4.2 × 107 km and 1.07 × 108 km
Its diameter is 12,035km.
Its rotation period is 243 days and revolution period is 225 days.
It has no satellite and its atmosphere is mostly CO2 . It has clouds of H2 SO4 .
The thickness of the atmosphere and the presence of large amount of CO2 the
surface temperature can rise as high as 480◦ C.
3. Earth (Prithvi)
Earth is the only known planet where life exists.
It is the fifth largest planet in the solar system. The average surface temperature is 15◦ C.
Earth’s surface consists of 71% water and 29% land.
It is 1.5 × 108 km away from the sun (1AU).
Its rotation period is 24 hours and revolution period is 36 days and 6 hour.
The six hours is the reason for leap year.
It has one satellite.
Its atmosphere is composed of nitrogen (78%), oxygen (21$), carbon dioxide,
water vapor, methane, etc
4. Mars (Mangal)
Due tot he presence of limonite it is red in color thus it is called the red planet
and can be seen from earth.
Its diameter is 6,724km which if half of that of the earth’s.
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It is about 2 × 108 km away from the sun and 7.8 × 107 km away from the
earth.
Its temperature during the day varies like the earth but during the night it
may fall below -38◦ .
Its rotation period is 24hours and 37 minutes whilst its revolution period is
687 days.
It consists of two satellites (Phobos and Deimos) and two polar caps at its
poles made up of snow.
Big craters and volcanoes dominate the surface. One third of the surface is
covered by dark patches. Despite the lack of water on those patches, they’re
still called ’Seas of Mars’.
Mars’ atmosphere consists of CO2 , H2 O, and O2 etc.
5. Jupiter (Brihaspati)
Jupiter is the largest planet of the solar system.
It is around 319 times bigger than the earth.
Its average surface temperature is -143◦ C.
Its rotation period is 10 hours and revolution period is about 12 years.
It has 67 satellites.
Its atmosphere consists of hydrogen and helium. It is always surrounded by
dense clouds of methane and thus its surface is not seen clearly.
It has a red spot in its atmosphere which is assumed to be formed due to a
hurricane.
6. Saturn (Sani)
It is surrounded by three elliptical rings separated by by dark gaps.
The rings are composed of ice and dust particles
It revolves in 10 hours and 30 minutes and its revolution period is 29.5 years.
Its axis subtends an angle of 27◦ against its orbital plane so the day and night
are not equal at all places.
It has 62 satellites, excluding the particles in the ring.
Titan is the largest of them having a diameter of 5,140km.
It is 1.5 × 109 km from the sun and 1.27 × 109 km from the earth.
Its average temperature is -180◦ C and its atmosphere mostly consists of hydrogen and helium.
7. Uranus (Arun)
It is blue in color.
Its atmopshere consists of methane, helium, and hydrogen.
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It is believed that water lies beneath the ammonia and a rocky core is present
in the center.
It is 2.87 × 109 km away from the sun and 2.73 × 109 km away from the earth.
Its diameter is 50,442 km and its average surface temperature is -216◦ C.
Its rotation period is 17 hours 8 minutes and revolution period is 84 years.
It has 27 satellites
8. Neptune (Barun)
Neptune is the farthest planet from the sun.
Its atmosphere consists of hydrogen, helium, neon, silicate, and water.
The planet has a great dark spot as large as the the earth.
It is 4.48 × 109 km away from the sun and 4.36 × 109 km away from the earth.
Its average surface temperature is −220◦ C.
Its rotation period is 16 hours and revolution is 164 years.
It has 14 satellites. Among them Triton is the largest satellite having diameter
2,705km.
4.3.4
Comets
The gaseous mass that revolves around the sun in a highly elliptical orbit is a comet.
They are compsed of gas, dust, and ice. It is the tail or broom shaped member of
the solar system.
They reflect the light of the sun and have a long orbit period.
A comet consists of three parts:
1. Nucleus: a mass of crumbly rock particles trapped inside frozen matter
2. Coma: It is the cloud of evaporating layers and dust particles
3. Tail: When comets approach the sun, due to the heat of the sun the ice and
gaseous vapor evaporates and forms a tail
Coments when they’re approaching the sun can be seen with the naked eyes
otherwise a telescope is required. They’re seen on the eastern sides but gradually
disappear over the course of their orbits.
Name of Comets
Halley’s Comet
Temple-tutle
Enke
Schwassmann-Wachmann
Bennet
Shoemaker Levy
First Observed
240BC
1366AD
1786AD
1796AD
1969AD
1993AD
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Revolution Period (years)
76
33
3.3
15
Collided with Jupiter and Collapsed in 1994AD
Comets can’t be considered as stars because:
1. They’re non-luminous object
2. They’re too light
3. They don’t have a very strong gravitational influence
4.3.5
Meteors and Meteorites
Meteor is a bright streak of lght seen for a short during in the sky on a clear night.
Thus it is also called a shooting or falling star. Large and bright meteor are also
called fire balls.
Meteorites are the ones which manage to reach the surface.
There are three types meteors:
1. Stony: Made up of mostly silica
2. Irony: Made up of mostly iron
3. Stony Iron: Equal amount of silica and iron
Most meteorites are irony nature. Their mass can rang from 0.1kg to 20,000kg.
About 50,000 years ago a meteorite fell in Arizona, USA and created a crater
1,265m wide and 1755m deep.
It is believed that about 250 million visible meteors enter the earths atmosphere
every day with velocities ranging from 35km.s−1 to 95km.s−1 .
4.3.6
Constellations
Constellations are a group of stars which do not change their location relative to
other to always form a fixed pattern.
There are a total of 88 constellations and out of them 12 constellations are used
as the signs of the zodiac.
4.3.7
Ursa Minor
It is the third largest constellation which is visible on Baisakh and Jestha. It has
seven stars.
4.3.8
Ursa Minor
Is is known as little bearh. It has seven bright stars At the end of the ursa minor
there is a polar star. It can be seen in the month of Ashad and Shrawan, Ursa minor
can be seen in the northern sky.
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4.3.9
Orion
It has seven stars. looks like a hunter. It can be seen in the months of Poush and
Magh.
4.3.10
Importance of Zodiacs
It can be used to guess time and direction.
4.3.11
Galaxy
A big cluster of star is called a galaxy. It is a collection of various stars, gas and
dust.
A typical galaxy measures 100,000 light years in diameter and contains a hundred
billion stars.
There are about 100 billion galaxies in the universe. So the total number of stars
in the universe is around 1022
The closest two galaxies from the milky way are the large Magellanic cloud and
the small Magellanic cloud. The other closest is the Andromeda galaxy.
On the basis of their shape, galaxies are classified into three categories:
1. Irregular Galaxy: They have no particular shape and tend to smaller and
fainter than the other types of galaxies. Some astronomers think that these
galaxies might have been caused by gigantic explosions at their centers. Thus,
the stars forming an irregular galaxy are unevenly distrusted in the galaxy.
2. Spiral Galaxy: The have a nucleus of bright star and flattered arms that spiral
around the core. Each spiral contains millions of stars.
3. Elliptical Galaxy: They can vary from being nearly spherical to a flattened
disk. They have a bright center and no spiral arms. They contain very little
dust and gas and are generally older than the other types of galaxies.
4.3.12
Milky Way (Akash Ganga)
It is the spiral galaxy which contains our solar system within it. It is estimated that
there might be 101 1 stars in the galaxy with its total mass being 1.33 × 1011 times
greater than the sun.
4.3.13
Satellites
Satellites are heavenly bodies which orbit a planet. The speed of a satellite around
its planet is called orbital velocity which depends directly upon the mass of the
planet and inversely to the distance from the planet.
In our solar system there are 173 natural satellites with the majority being of
Jupiter’s.
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Moon
The moon is the only natural satellites of the earth. The mean distance between
the earth and the moon is 384,400km. Moons’s surface area is 3.79 × 107 km2 . It
has a diameter of about 3,476km.
The moon takes about 27.33 days to complete a revolution around the earth, this
is called a sidereal month. Synodic month, on the other hand, is the time between
one full moon and next which measures 29 days 12 hours and 44 minutes.
Planets
Number of Satellite
Mercury
0
Venus
0
Earth
1 (Moon)
Mars
2 (Phobos and Deimos)
Jupiter
67 (Ganymede, Callisto, Io, Europa etc.)
Saturn
62 (Titan)
Uranus
27 (Miranda, Ariel, etc)
Neptune
14 (Triton, Neried, etc)
4.3.14
Artificial Satellite
Manmade object which revolve around the sun are called artificial satellite. The
artificial satellite are kept at geocentric orbit at a height of 36,900km from the
Earth’s surface. They are sent with the help of rockets to revolve around the earth
and use solar cells for power.
The purpose of launching them are:
1. To collect more data about the universe
2. To conduct various scientific experiments
3. To forecast weather
4. To spy
5. To research
6. To establish space laboratory and make spaceships in the future
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