Prasanna

On this page, you will find Probability Class 10 Notes Maths Chapter 15 Pdf free download. CBSE NCERT Class 10 Maths Notes Chapter 15 Probability will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Maths Chapter 15 Notes Probability

Probability Class 10 Notes Understanding the Lesson

Theoretical probability: The theoretical (or classical) probability of an event E [denoted by P(E)] is given by
\(\mathrm{P}(\mathrm{E})=\frac{\text { Number of outcomes favourable to } \mathrm{E}}{\text { Number of all possible outcomes of the experiment }} \text { i.e., } \frac{n(\mathrm{A})}{n(\mathrm{S})}\)

Number of all possible outcomes of the experiment when the outcomes of the experiment are equally likely.

Equally likely outcomes: All the outcomes of an experiment are said to be equally likely when the chances of there occurrence are equal.
e.g. When a coin is tossed, the two possible outcomes are head and tail, which are equally likely.

Elementary event: An outcome of a random experiment is called an elementary event. e.g. In tossing a coin, possible outcomes are head and tail.
⇒ H and T are elementary events.

• The sum of the probabilities of all the elementary events of an experiment is 1.
• For an events E, P(E) + P(\(\overrightarrow{\mathrm{E}}\)) = 1, where \(\overrightarrow{\mathrm{E}}\) is the event ‘Not E’. E and \(\overrightarrow{\mathrm{E}}\) are called complementary events.
• If P(E) = 1, then E is called ‘sure or certain event’.
• If P(E) = 0, then E is impossible event.
• For any event E,
  0 < P(E) <1

On this page, you will find Periodic Classification of Elements Class 10 Notes Science Chapter 5 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 5 Periodic Classification of Elements will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 5 Periodic Classification of Elements

Periodic Classification of Elements Class 10 Notes Understanding the Lesson

1. At present, 118 elements are known to us. All these have different properties. Out of these 118, only 98 are naturally occurring. These elements have different characteristic properties, so it is very difficult to study these elements individually. Scientists made several attempts to classify elements according to their properties.

2. Dobereiner’s Triads (1817): He identified some triads (groups having three elements). Dobereiner showed that when the three elements in a triad were written in the order of increasing atomic masses; the atomic mass of the middle element was the average of the atomic masses of the other three elements. For example,

Dobereiner could identify only three triads from the elements known at that time. Hence, this system of classification into triads was not found to be useful.

3. Newland’s Law of Octaves (1866): He arranged the known elements in the order of increasing atomic masses. He found that every eighth element had properties similar to that of the first like the musical note. It is known as Newlands law of octaves.

sa (do)	re (re)	ga (mi)	ma (fa)	pa (so)	da (la)	ni (ti)
H	Li	Be	B	C	N	O
F	Na	Mg	A1	Si	P	s
Cl	K	Ca	Cr	Ti	Mn	Fe
Co and Ni	Cu	Zn	Y	In	As	Se
Br	Rb	Sr	Ce and La	Zr	–	–

4. Limitations

• Law of octaves was applicable only upto calcium.
• Discovery of Noble gases disturbed the octaves.
• Octaves worked well only for lighter elements.
• Properties of new elements could not fit in it.

5. Mendeleev’s Periodic Table

Mendeleev’s Periodic Law: Physical and chemical properties of elements are the periodic function of their atomic masses.
Mendeleev’s periodic table is based on the chemical properties of elements. Mendeleev’s periodic table contains vertical columns called ‘groups’ and horizontal rows called ‘periods’.

6. Achievements of Mendeleev’s Periodic Table: 63 elements were known at the time of classification.

• Elements with similar properties could be grouped together.
• Mendeleev left some gaps in his periodic table. Mendeleev boldly predicted the existence of some elements that had not been discovered at that time.
• Noble gases discovered, could be placed without disturbing the existing order.

Remember
Scandium, gallium and germa-nium have properties similar to Eka-boron, Eka-aluminium and Eka-silicon respectively.

7. Limitations of Mendeleev’s Classification

• The position of hydrogen in the table was not certain because it could be placed in the group of alkali metals as well as in halogens.
• Isotopes of elements were placed in the same position in the table though according to their atomic masses, they should have been placed in different positions.
• Certain elements of higher atomic mass preceed those with lower atomic mass. For example, tellurium (atomic mass 127.6) precedes iodine (atomic mass 126.9). Iodine was placed after tellurium though it had lower atomic mass because Iodine had properties similar to bromine and not selenium.

8. The Modern Periodic Table
Henry Moseley (1913) exhibited that the atomic number of an element is a more fundamental property than its atomic mass. Mendeleev’s periodic law was modified and atomic number was adopted as the basis of the modern periodic table.

9. The Modern Periodic Law states that:
The physical and chemical properties of the elements are the periodic function of their atomic numbers.
It means that if the elements are arranged in order of increasing atomic numbers, the elements with similar properties recur after regular intervals. Many new forms of periodic table have been proposed in recent times with modern periodic law as the guiding principle, but the general plan of the table remains the same as proposed by Mendeleev. The most commonly known periodic table is the Long form of the periodic table.

• Modern periodic table contains 18 vertical columns known as groups and 7 horizontal rows known as periods.
• Elements in a group have the same number of valence electrons.
• Number of the shells increases as we go down the group.
• Elements in a period have same number of shells.
• Number of elements placed in a particular period depends upon the fact that how electrons are filled into various shells.
• Maximum number of electrons that can be accommodated in a shell depends on the formula 2n² where n is the number of the given shell. For example, in K shell the number of electrons is 2 x (1)² = 2 in the first period, L shell – 2 x (2)² = 8 elements in the second period.
• Position of the element in the periodic table tells about its reactivity.

10. Trends in the Modern Periodic Table

Valency: Number of valence electrons present in the outermost shells. Valency remains the same down a group but changes across a period.

Atomic Size: Atomic size refers to radius of an atom.

Atomic size or radius decreases in moving from left to right along a period due to increase in nuclear charge. Atomic size increases down the group because new shells are being added as we go down the group.

Metallic Character: Metallic character means the tendency of an atom to lose electrons.

Metallic character decreases across a period because the effective nuclear charge increases, that means the tendency to lose electrons decreases. Metals are electropositive as they tend to lose electrons while forming bonds.

Class 10 Science Chapter 5 Notes Important Terms

Atomic number of an element is equal to the number of protons in the nucleus of its neutral atom.
Atomic number = Number of protons = Number of electrons

Electronic configuration corresponds to the distribution of electrons in the different shells.

Element is a chemical substance that cannot be decomposed by chemical means into simple substances. It contains the same kind of atoms.

Groups are the vertical rows in the periodic table.

Periods are the horizontal rows in the periodic table.

Periodic table is a tabular arrangement of elements in groups (vertical columns) and periods (horizontal rows) highlighting the regular trends in physical and chemical properties.

Shell is a region around the nucleus in an atom where electron revolves.

Valence shell is the outermost shell of an atom.

Periodicity. The properties which reoccur after a regular intervals in a periodic table are called periodic properties and the phenomenon is called periodicity of element.

Modern. Modern periodic law can be stated as follows:
“Physical and chemical properties of elements are a periodic function of their atomic number”.

On this page, you will find Gravitation Class 9 Notes Science Chapter 10 Pdf free download. CBSE NCERT Class 9 Science Notes Chapter 10 Gravitation will seemingly help them to revise the important concepts in less time.

CBSE Class 9 Science Chapter 10 Notes Gravitation

Gravitation Class 9 Notes Understanding the Lesson

1. Newton’s law of gravitation
“Every particle in the universe attracts every other particle with a force, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between the two masses. The direction of force is along the line joining the two particles.”

Force of attraction between A and B

Where G is constant of proportionality called universal gravitational constant.

2. Universal gravitational constant
\(\mathrm{G}=\frac{\mathrm{F} r^{2}}{m_{1} m_{2}}\)
SI unit of G is Nm² kg^-2
Value of G = 6.67 x 10^-11 Nm² kg^-2.

3. Properties of gravitational force

• It is always attractive in nature.
• It obeys inverse square law  \(\mathrm{F} \alpha \frac{1}{r^{2}}\)
• Gravitational force is independent of the medium.
• It is a long range force.
• It is a weak force.
• Force of gravitation due to the Earth is called gravity.

4. Definition of G
Take = m2 = m = 1 kg r = 1 m
Hence, the force of attraction between two point masses separated by a unit distance is called universal gravitational constant.

5. Importance of the universal law of gravitation:
The universal law of gravitation successfully explained several phenomena

• The force that binds us to the Earth.
• The motion of the moon around the Earth.
• The motion of planets around the Sun; and
• The tides due to the moon and the Sun.

6. Free fall
Whenever objects fall towards the Earth under gravitational force alone, we say that the objects are in free fall.

7. Acceleration due to gravity (g):
The acceleration with which a body falls towards the Earth due to Earth’s gravitational pull is known as acceleration due to gravity. It is denoted by ‘g’.

8. Expression for acceleration due to gravity on the surface of the Earth:
The gravitational force between a body of mass ‘m’ and the Earth (of mass M) can be represented as
\(\mathbf{F}=\frac{\mathrm{G} \mathrm{Mm}}{r^{2}}\) …………….. (1)
Force of gravity is expressed as, F=Mg ……………(2)
From (1) and (2),\(g=\frac{\mathrm{GM}}{r^{2}}\)
The Earth is not a perfect sphere. As the radius of Earth increases from the poles to the equator, the value of g becomes greater at the poles than at the equator.

9. Calculate the value of g on the Earth:
\(g=\frac{G M}{r^{2}}\)
By putting the value of mass, radius of Earth and universal gravitational constant we can find out the value of acceleration due to gravity on the Earth.

10. Acceleration due to gravity at

• the surface of the Earth, g = 9.8 m/s²
• the centre of the Earth, g = 0.

11. Mass
Mass of a body is the quantity of matter contained in it.

• Mass of an object is constant and does not change from place to place.
• SI unit of mass is kilogram (kg).
• Mass of an object is a measure of its inertia.

12. Weight
The weight of an object is the force with which it is attracted towards the Earth.
w = mg

• SI unit of weight is newton (N).
• Weight is a vector quantity.
• Weight is directly proportional to mass of the body. So at a given place, weight of a body is a measure of its mass. w α m.
• Weight of a body changes from place to place because, acceleration due to gravity varies with position and location of a body.

13. Weight of an object on the moon
The acceleration due to gravity of moon is one sixth of Earth.
\(g_{\text {moon }}=\frac{1}{6} g_{\text {Earth }}\)
Due to this, the weight of an object on the moon is one sixth of the weight of the object on the Earth.
\(\frac{\text { Weight of the object on the moon }}{\text { Weight of the object on the Earth }}=\frac{1}{6}\)
Weight of the object on the moon = 1/6 x weight of the object on the Earth.

14. Gravitation (Flotation)
Thrust: The force acting on an object perpendicular to its surface is called thrust.

• SI unit of thrust is newton (N).

Pressure: The thrust on unit area is called pressure.

• SI unit of pressure is N/m² or Nm^-2.
• In honour of scientist Blaise pascal, the SI unit of pressure is called pascal (pa).
  1 pa = 1 N/m²
  Pressure = Thrust/Area

15. Consequences of pressure

(i) Nails and pins have painted ends so that these can be fixed with minimum force because the pressure on the painted ends would be large.

(ii) Wide wooden or metal or concrete sleepers are kept below railway lines to reduce pressure on the railway tracks and prevent them from sinking into the ground.

(iii) The foundation of a building or a dam has a large surface area so that the pressure exerted by it on the ground is less. This is done to prevent the sinking of the building or dam into the ground.

(iv) Skiers use flat skies to slide over snow as the long flat skies increase the area of contact, which reduces pressure exerted by the skier on the snow enabling the skier to slide over the snow without sinking.

(v) Broad handles are provided in bags and suitcases. Due to broad size of the handles, the area of contact increases which reduces the pressure exerted by the weight of the bag or suitcase.

(vi) A camel walks easily on the sandy surface than a man inspite of the fact that a camel is much heavier than a man. This is because their legs are padded and flat which provides greater surface area of contact with the sand and hence exerts less pressure on the sand. On the other hand, a man has very small surface area, so he exerts greater pressure and is likely to sink in sand.

16. Pressure in fluids
A substance which can flow is called a fluid. All liquid and gasses are fluids.

• A fluid contained in a vessel exerts pressure at all points of the vessel and in all directions.
• Pascal’s law: In an enclosed fluid, if pressure is changed in any part of the fluid, then this change in pressure is transmitted undiminished to all the other parts of the fluid.

17. Buoyancy
When a body is partially or wholly immersed in a fluid, an upward force acts on it which is called upthrust or buoyant force. The property of the fluids responsible for this force is called buoyancy.

18. Why do objects float or sink when placed on the surface of a fluid?

1. A body sinks if its weight is greater than the buoyant force acting on it.
Weight > buoyant force
Apparent weight = weight – buoyant force

2. A body floats if buoyant force balance the weight of the body.
A body having an average density greater than that of water (fluid), sinks into it while a body of average density smaller than that of water (fluid), floats on it.

19. Archimedes principle
When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.

20. Density and relative density
Density: Density of a substance is defined as its mass per unit volume.
\(\text { Density }=\frac{\text { Mass }(\mathrm{M})}{\text { Volume }(v)} \text { or, } d=\frac{\mathrm{M}}{\mathrm{V}}\)
SI unit of density is kg/m³ or kg m^-3

21. Relative density: The relative density of a substance is the ratio of its density to that of water.
Relative density = Density of substance/Density of water.
It has no unit.

Class 9 Science Chapter 10 Notes Important Terms

Newton’s law of gravitation: Every particle in the universe attracts every other particle with a force, which is directly proportional to the product of their masses and inversely proportional to square of distance between the two masses.

Freefall: Whenever objects fall towards the Earth under gravitational force alone, we say that the objects are in free fall.

Acceleration due to gravity: The acceleration with which a body falls towards the Earth due to Earth’s gravitational pull is known as acceleration due to gravity.

Mass: Mass of a body is the quantity of matter contained in it.

Weight: The weight of an object is the force with which it is attracted towards the Earth.

Density: Density of a substance is defined as its mass per unit volume.

Relative density: The relative density of a substance is the ratio of its density to that of water.

Thrust: The force acting on an object perpendicular to the surface is called thrust.

Pressure: The thrust per unit area is called pressure.

Pascal’s law: In an enclosed fluid, if pressure is changed in any part of the fluid, then this change in pressure is transmitted undiminished to all the other parts of the fluid.

Buoyancy: When a body is partially or wholly immersed in a fluid, an upward force acts on it which is called upthrust or buoyant force.

Archimedes principle: When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.

On this page, you will find Force and Laws of Motion Class 9 Notes Science Chapter 9 Pdf free download. CBSE NCERT Class 9 Science Notes Chapter 9 Force and Laws of Motion will seemingly help them to revise the important concepts in less time.

CBSE Class 9 Science Chapter 9 Notes Force and Laws of Motion

Force and Laws of Motion Class 9 Notes Understanding the Lesson

1. Force
It is entity which when applied on a body changes or tends to change a body’s

• state of rest
• state of uniform motion
• direction of motion
•  shape

2. Balanced forces
When a number of forces acting simultaneously on a body do not bring about any change in state of rest or of uniform motion along a straight line, then forces acting on a body are said to be balanced forces.

3. Unbalanced forces
When a number of forces acting simultaneously on a body bring about a change in its state of rest or of uniform motion along a straight line, then these forces acting on the body are said to be unbalanced forces.

4. Newton’s first law of motion
An object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.

5. Inertia
Inertia is the natural tendency of an object to resist a change in its state of motion or of rest.

6. The mass of an object is a measure of its inertia.
Examples:

• Passenger tends to fall backward, when a bus starts suddenly.
• Falling of fruits and leaves by a shaking tree.
• When a carpet is beaten with a stick, dust particles come out.
• When the card covering a glass tumbler is flicked with the finger coin placed over it falls in the tumbler.

7. Momentum (P)

• Momentum gives an idea about the quantity of motion contained in a body.
• The momentum (P) of an object is defined as the product of its mass (m) and velocity (v).
  P = mv
• Momentum is vector quantity and its unit is kg ms^-1.

8. Second law of motion
The second law of motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of force.

9. Mathematical formulation of second law of motion
Suppose an object of mass, m is moving along a straight line with an initial velocity, v. It is uniformly accel-erated to velocity, v in time, t by application of constant force F throughout the time, t. The initial and final momentum of the object will be, P₁ = mu and P₂ = mv
respectively.


∴ F =ma
K is proportionality constant and the value So,
SI unit of force is newton.

10. First law of motion can be stated from the second law
F = ma
\(F=\frac{m(v-u)}{t}\)
Ft = mv – mu
when F = 0, v – u. This means that the object will continue moving with uniform velocity, u throughout the time, t. If u is zero then v will also be zero. That is, the object will remain at rest.

11. Example of second law of motion:
As we know that \(\text { F } \alpha \frac{1}{t}\)

• A cricket players lowers his hand while catching the ball to increase the time so that impact of force decreases.
• A karate player can break a pile of tiles with a single blow of his hand. This is because, as time decreases impact of force increases.
• Vehicles are fitted with shockers. The shockers increase the time of transmission of the force of the jerk to reach the floor of the vehicle. Hence less jerk is experienced by the passengers.

12. Third law of motion
According to the third law of motion, every action there is an equal and opposite reaction and they act on two different bodies.

Example of third law of motion:

• Recoiling of gun.
• When a man jumps out from a boat, the boat moves backward.

13. Conservation of momentum
In an isolated system (where there is no external force), the total momentum remains conserved.
m_Au_A + m_Bu_B = m_Av_A + m_Bv_B

14. Derivation
Suppose two objects of mass m_A and m_B are travelling in the same direction along a straight line at different velocity u_A and u_B respectively, and there are no external unbalanced forces acting on them. Let u_A > u_B and two balls collide each other. During collision which last for a time t, ball A exerts force on ball B and ball B exerts force F_BA on ball A. Suppose v_A and i>_B are the velocities after collision.

15. Illustration of conservation of momentum

• Recoil of gun.
• Rocket propulsion.
• Inflated balloon lying on the surface of a floor moves forward when pierced with a pin.

Class 9 Science Chapter 9 Notes Important Terms

Force: It is entity which when applied on a body changes or tends to change a body’s.

• state of rest
• state of uniform motion
• direction of motion
• shape

Balanced forces: When a number of forces acting simultaneously on a body do not bring about any change in state of rest or of uniform motion along a straight line, then forces acting on a body are said to be balanced forces.

Unbalanced forces: When a number of forces acting simultaneously on a body bring about change in its state of rest or of uniform motion along a straight line, then these forces acting on the body are said to be unbalanced forces.

Inertia: Inertia is the natural tendency of an object to resist a change in its state of motion or of rest.

Momentum: Momentum of a body is product of its mass and velocity.

Conservation of momentum: In an isolated system the total momentum remains conserved.

On this page, you will find Statistics Class 10 Notes Maths Chapter 14 Pdf free download. CBSE NCERT Class 10 Maths Notes Chapter 14 Statistics will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Maths Chapter 14 Notes Statistics

Statistics Class 10 Notes Understanding the Lesson

The measures of central tendency are:

• Arithmetic mean or mean
• Median
• Mode

Mean of Raw Data

Mean of n observations x_1; x₂, x₃, ..x_n is given by
\(\bar{x}=\frac{x_{1}+x_{2}+x_{3}+\ldots+x_{n}}{n}=\frac{\Sigma x_{i}}{n}\)
where ∑ (sigma) means “summation of’.

1. Mean of Grouped Data

(i) Direct method:
\(\bar{x} \doteq \frac{\Sigma f_{i} x_{i}}{\Sigma f_{i}}\)
For each class interval, Class mark = \(\frac{\text { Lower limit }+\text { Upper limit }}{2}\)

(ii) Short-cut method or assumed mean method:

Where a = assumed mean

(iii) Step-deviation method:

h=Class-Size

2. Mode of Groped Data
Class with the maximum frequency is called the modal class.
\(\text { Mode }=l+\left[\frac{f_{1}-f_{0}}{2 f_{1}-f_{0}-f_{2}}\right] \times h\)

Where l = lower limit of the modal class
h = size of the class-interval
f₁ = frequency of the modal class
f₀ – frequency of the class preceeding the modal class
f₂ = frequency of the class succeeding the modal class

3. Median of Ungrouped Data
To find the median of ungrouped data, first arrange the data values of the observations in the ascending or descending order. Then,

4. Median of Grouped Data
\(\text { Median }=l+\left[\frac{\frac{n}{2}-c \cdot f \cdot}{f}\right] \times h\)
l – lower limit of median class.
n = number of observation
c.f. = cumulative frequency of the class preceeding the median class
f = frequency of the median class
h = class size

Median class: Class whose cumulative frequency is greater than (and nearest to) \(\frac{n}{2}\)

On this page, you will find Motion Class 9 Notes Science Chapter 8 Pdf free download. CBSE NCERT Class 9 Science Notes Chapter 8 Motion will seemingly help them to revise the important concepts in less time.

CBSE Class 9 Science Chapter 8 Notes Motion

Motion Class 9 Notes Understanding the Lesson

1. Rest: A body is said to be at rest if its position does not change with respect to a fixed point taken as a reference point in its surrounding with the passage of time.

2. Motion: A body is said to be in motion if its position is changes with respect to a fixed point taken as a reference point in its surrounding with the passage of time.

3. Scalar quantity: A physical quantity which is described completely by its magnitude only, is called a scalar quantity.

4. Vector quantity: A physical quantity that has magnitude as well as direction is called a vector quantity. Distance: The total path length travelled by a body in a given interval of time is called distance. Displacement: The shortest distance measured from initial to the final position of an object is known as displacement.

5. Difference between distance and displacement

Distance	Displacement
1.   It is the actual length of the path covered by a moving body. 2.   It is always positive or zero. 3.   It is a scalar quantity.	1.    It is the shortest distance measured between the initial and final position. 2.    It may be positive, negative or zero. 3.    It is a vector quantity.

SI unit of distance and displacement is metre (m).

6. Uniform motion: A body moving in straight line has a uniform motion if it travels equal distance in equal intervals of time.

7. Non-uniform motion: A body has a non-uniform motion if it travels unequal distances in equal intervals of time.

8. Speed: The speed of a body is defined as distance travelled by it per unit time.

Speed is scalar quantity and SI unit of speed is m/s.

9. Average speed: It is defined as the total distance travelled by a body divided by the total time taken to cover this distance.

SI unit of speed and velocity is same.

Difference between speed and velocity

Speed	Velocity
1.   Speed is the ratio of distance and time. 2.   Speed is always positive. 3.   Speed is a scalar quantity.	1.  Velocity is ratio of displacement and time. 2.  Velocity may be negative or positive. 3.  Velocity is a vector quantity.

10. Acceleration: The rate of change of velocity of a body with respect to time is called its acceleration.

\(\text { Acceleration }=\frac{\text { Change in velocity }}{\text { time taken }}\)
\(a=\frac{v-u}{t}\)

Here, u – initial velocity
v = final velocity
t = time

11. Acceleration is a vector quantity and its SI unit is m/s².

12. If a body is travelling with uniform acceleration then its average velocity can be expressed as

\(v_{\text {avg }}=\frac{u+v}{2}\)
Here, u = initial velocity
v – final velocity

13. If the speed of a body is continuously increasing, the body is said to be continuously accelerating. If the speed of body is continuously decreasing, the body is said to be retarding.

14. Graphical Representation of Motion
Distance-time graph (Position time graph)

15. Slope of velocity-time graph gives speed and velocity

16. velocity-time graph

17. Slope of velocity-time graph gives distance and displacement.

18. Equation of motion by graphical method
Let us consider a body moving with acceleration a where u is initial velocity and v is final velocity, s is displacement of the object and t is time interval.

(i) v = u + at
We know that slope of v – t graph gives acceleration so slope
\(=a=\frac{v-u}{t-o}\)
\(\begin{array}{l}
a=\frac{v-u}{t} \\
v=u+\text { at }
\end{array}\)

(ii) \(s=u t+\frac{1}{2} a t^{2}\)
We know that area under v -1 graph gives displacement.
Area = s = area of triangle CDE + area of rectangle ABCE
\(s=u t+\frac{1}{2} \times t \times(v-u)\)
Putting the value of v – u.
\(s=u t+\frac{1}{2} \mathrm{at}^{2}\)

(iii) v² – u² = 2as
a where u is initial velocity and v is final velocity, s is displacement of the object and t is time interval.
\(s=\frac{1}{2} \times(v+u) \times t\)
\(\text { from } 1\left(t=\frac{v-u}{a}\right)\)
Putting the value of t.
v² – u² = 2as

19. Uniform circular motion
When an object moves in a circular path with uniform speed, its motion is called uniform circular motion.
\(v=\frac{2 \pi r}{t}\)

If a body is moving in a circular path and completes one round (2πr distance) in time, speed is given by
Uniform circular motion is accelerated motion.

Class 9 Science Chapter 8 Notes Important Terms

State of rest: A body is said to be at rest if it does not change its position with respect to a fixed point taken as a reference point in its surroundings with passage of time.

State of motion: A body is said to be in motion if it changes its position with respect to a fixed point as a reference point in its surroundings with the passage of time.

Scalar quantity: A physical quantity which is described completely by its magnitude only, is called scalar quantity.

Vector quantity: A physical quantity which has magnitude as well as direction and obeys the vector addition is called vector quantity.

Distance: The total path length travelled by a body in a given interval of time is called distance.

Displacement: The shortest distance measured from initial to the final position of an object is known as displacement.

Uniform motion: A body moving in a straight line has a uniform motion, if it travels equal distance in equal intervals of time.

Non-uniform motion: A body has a non-uniform motion, if it travels unequal distances in equal intervals of time.

Speed: The speed of a body is defined as distance travelled by it per unit time.

Velocity: Velocity is defined as displacement per unit time.

Acceleration: The rate of change of velocity of a body with respect to time is called its acceleration.

Retardation: When acceleration of a body is opposite to its velocity, it is called retardation.

Uniform circular motion: When an object is moving in a circular path with a constant speed, the motion of the object is said to be uniform circular motion.

On this page, you will find Diversity in Living Organisms Class 9 Notes Science Chapter 7 Pdf free download. CBSE NCERT Class 9 Science Notes Chapter 7 Diversity in Living Organisms will seemingly help them to revise the important concepts in less time.

CBSE Class 9 Science Chapter 7 Notes Diversity in Living Organisms

Diversity in Living Organisms Class 9 Notes Understanding the Lesson

1. What is classification?
Grouping the organisms on the basis of their similarities and differences is called classification.

2. Need for classification

• To provide information regarding diversity of plants and animals on the Earth.
• Understand the interrelationship between different groups of plants and animals.
• To find similarities or dissimilarities in their characteristic features.
• To identify the organism.
• To indicate evolutionary trends.

3. Characteristics or criteria of classification

• Complexity of structure: Prokaryotes or Eukaryotes
• Body organisation: Unicellular or Multicellular
• Mode of obtaining Nutrition: Autotrophic or Heterotrophic
• Evolutionary relationship
• Presence or absence of cell wall

4. Kingdom
It is the highest category of classification. Each kingdom has some similar fundamental characteristics in all organisms grouped under that kingdom. The five-kingdom classification was given by R.H. Whittaker.

Characteristics	Monera	Protista	Fungi	Plantae	Animalia
Complexity of structure	Prokaryotes	Eukaryotes	Eukaryotes	Eukaryotes	Eukaryotes
Body organisation	Unicellular	Unicellular	Multicellular (at some stage of life)	Multicellular	Multicellular
Mode of nutrition	Autotrophic or Heterotrophic	Autotrophic or Heterotrophic	Heterotrophic Parasitic Saprophytic Symbiotic	Autotrophic	Heterotrophic

 

Characteristics	Monera	Protista	Fungi	Plantae	Animalia
Cell wall	Present or absent	Present or absent	Present (made up of chitin)	Present (made up of cellulose)	Absent
Appendages	Cilia or flagella for movement	Cilia, flagella or pseudopodia for movement	Do not move	Do not move	Different appendages
	e.g., Bacteria	e.g., Amoeba	e.g., Mushroom	e.g., Rose	e.g., Monkey

Differentiate between:

S. No.	Thallophyta	Bryophyta	Pteridophyta
1.	Plant body thallus like, not differentiated into root, stem or leaf.	Plant body does not have true root, stem or leaf but shows root­like and leaf-like structures.	Plants have true root stem or leaf.
2.	Vascular system absent.	True vascular system is absent.	True vascular system is present.
3.	Predominantly aquatic.	They live on land and in water. They are known as the Amphibians of the plant kingdom.	They are terrestrial, i.e., they live on land.
4.	No embryo formation after fertilization. e.g., Algae	Embryo formed after fertilisation. e.g., Mosses, liverworts .	Embryo formed after fertilisation. e.g., Ferns

 

S. No.	Cryptogamae	Phanerogamae
1.	Reproductive organs are hidden.	Reproductive organs are visible.
2.	Fertilisation results in the formation of a naked embryo called spores.	Fertilisation results in the formation of seeds which consists of embryo and cotyledons.
3.	Water is required for fertilisation.	Water is not required for fertilisation always except for aquatic phanerogams.
	e.g., Thallophyta, Bryophyta, Pteridophyta	e.g., Gymnospermae and Angiospermae

 

S. No.	Gymnospermae	Angiospermae
1.	Plants bear naked seeds.	Seeds are present inside fruits.
2.	Xylem is without vessels and phloem is without companion cells.	Well developed vascular tissue present.
3.	Plants are perennial, woody and evergreen.	Plants are annual, biennial, perennial, woody or green.
	e.g., Pinus, Cycas	e.g., Neem, Rose, Mango

 

S. No.	Monocotyledonous Plants	Dicotyledonous Plants
1.	Single cotyledon in seeds.	Two cotyledons in seeds.
2.	Fibrous roots.	Tap roots.
3.	Parallel venation.	Reticulate venation.
	e.g., Lily, Rice, Wheat	e.g., Hibiscus, Pea, Gram

5. Characteristic features of different Phyla of Kingdom Animalia Porifera

• Porifera means organisms with holes.
• Non-motile animals attached to solid support
• Holes or pores all over body
• Have canal system that helps in circulating water throughout the body to bring in food and oxygen.
• Body covered with hard outside layer or skeleton
• Minimal differentiation of body and division into tissues
• Commonly called sponges found in marine habitats
• Acoelomate (without body cavity)
  Examples: Euplectella, Sycon, Spongilla

6. Coelenterata

• Animals living in water
• More body design differentiation
• Diploblastic body
• Some species live in colonies (corals) while others have a solitary life span (Hydra)
  Examples: Jelly fish, Sea Anemone, Hydra

7. Platyhelminthes

• Body is complexly designed
• Bilaterally symmetrical body
• Triploblastic body
• Acoelomate
• Body flattened dorsi-ventrally, so called flatworms
• Free living or parasitic
  Examples: Planarian (free living) liver flukes, tapeworms (Parasitic)

8. Nematodes

• Bilaterally symmetrical
• Triploblastic body
• Cylindrical body
• Tissues present but no real organs
• Presence of pseudo coelom, a sort of body cavity
• Familiar as parasitic worms causing diseases, present in intestines
  Examples: Ascaris, Wucheraria

9. Annelida

• Bilaterally symmetrical
• Triploblastic
• Coelomate (having a body cavity or coelon)
• Extensive organ differentiation
• Segmented body (Metamerism)
• Found in fresh water, marine and on land
  Examples: Earthworms, Leech, Nereis

10. Arthropoda

• Largest group of animals
• Bilaterally symmetrical
• Segmented body
• Open circulatory system
• Coelomate
• Arthropoda means jointed legs
  Examples: Prawns, Butterflies, Housefly, Cockroach

11. Mollusca

• Bilaterally symmetrical
• Coelomic cavity is reduced
• Little segmentation
• Open circulatory system
• Kidney like organ for excretion
• There is a foot like structure for moving around
  Examples: Snails, mussels, Chiton, Octopus, Unio, Pila

12. Echinodermata

• They are spiny skinned organisms
• Echinos’ means hedgehog and ‘Derma’ means skin.
• Exclusively free living marine animals
• Triploblastic
• Acoelomate
• Peculiar water driven tube system
• Hard calcium carbonate structures as skeleton
  Examples: Star fish, sea urchin, feather star, sea cucumber

13. Protochordate

• Bilaterally symmetrical
• Triploblastic
• Coelomate
• Notochord present during larval stage
• Provides place for muscles to attach for easy movement
• Marine animals
  Examples: Balanoglossus, Herdmania, Amphioxu

14. Vertebrata

• Have a true vertebral column and internal skeleton
• Bilaterally symmetrical
• Triploblastic
• Coelomate and segmented
• Complex differentiation of body tissues and organs

15. All chordates possess the following features:

• Have a notochord
• Have a dorsal nerve cord
• Are triploblastic
• Have paired gill pouches in some stage of their life cycle
• Are coelomate

16. Vertebrates are grouped into 5 classes
Pisces

• Exclusively aquatic animals
• Skin covered with scales or plates
• Obtain oxygen dissolved in water
• Streamlined body and muscular tail for movement in water
• Cold-blooded
• Two-chambered heart
• Lays eggs in water

17. Are of two types:

• Cartilaginous fish (skeleton made entirely of cartilage), e.g., Shark
• Bony fish (skeleton made of both cartilages and bones), e.g., Rohu, Tima

18. Amphibia

• Lack scales
• Have mucus glands in skin
• Cold-blooded
• Three-chambered heart
• Respiration through gills, lungs or skin
• Lay eggs in water
• Live both on land and in water
  Examples: Frogs, toads, salamander, etc.

19. Reptilia

• Have scales
• Three-chambered heart but crocodiles have four chambered heart
• Cold-blooded
• Breathe through lungs
• Lay eggs with tough coverings so they do not lay eggs in water
  Examples: Snakes, turtles, lizards, crocodiles, chameleon

20. Aves

• Outside covering of feathers
• Four-chambered heart
• Warm-blooded
• Breathe through lungs
• Lay eggs
• Two forelimbs modified into wings for flight
  Examples: All birds like crow, pigeon, peacock, etc.

21. Mammalia

• Skin has hairs, oil and sweat glands
• Four-chambered heart
• Warm-blooded.
• Most of them give birth to young ones
• Few like Platypus and Echidna lay eggs
• Some like kangaroos give birth to poorly developed young ones
• Mammary glands present for production of milk to nourish their young ones
  Examples: Cat, human, rat, bat, whale, etc.

21. Nomenclature: System of assigning names or terms to the organisms is called as nomenclature. The names given to the organism can be

• Common name or
• Scientific name.

Common names cannot be used in the same way by the scientist world over and can often result in confusion. To avoid this, a system of scientific names has been proposed.

Binomial System of Nomenclature: The binomial system of nomenclature assigns two names to the organism in order to identify it first is the generic name (genus) and the second is the specific epithet (species). This system of nomenclature was given by Carolus Linnaeus.

22. Convention for writing the scientific names:

• The name of the genus begins with a capital letter.
• The name of the species begins with a small letter.
• When printed, the scientific name is given in italics.
• When written by hand, the genus name and the species name have to be underlined separately.

23. Scientific names of some organisms:

• Tiger – Panthera tigris
• Peacock – Pauo cristatus
• Mango – Mangifera indica
• Lotus – Nelumbo nucifera
• Neem – Azadiraehta indica
• Potato – Solanum tuberosum
• Ant – Hymenopetrous formicidae
• Frog – Rana tigrina
• Rose – Rosa indica
• Pea – Pisum sativum

Class 9 Science Chapter 7 Notes Important Terms

Prokaryotes: Organisms which do not have a clearly demarcated nucleus and other organelles.

Eukaryotes: Organisms having membrane bound cell organelles and a well-defined nucleus.

Unicellular: Organisms having only one cell in their body.

Multicellular: Organisms having many cells in their body.

Autotrophs: Organisms synthesising their own food by photosynthesis.

Heterotrophs: Organisms which depend on other organisms for their food.

Bilateral symmetry: The body organisation in which the left and right halves have same body design.

Radial symmetry: Arrangement of similar parts around a central body axis as in a wheel.

Diploblastic: Animals having a body made up of two layers of cells i.e., ectoderm and endoderm.

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CBSE Class 10 Science Chapter 3 Notes Metals and Non-metals

Metals and Non-metals Class 10 Notes Understanding the Lesson

1. Element is the simplest form of matter which contains one kind of atoms. About 118 elements are known today. There are more than 90 metals, 22 non-metals and a few metalloids.

• Sodium (Na), potassium (K), magnesium (Mg), aluminium (Al), calcium (Ca), Iron (Fe), Barium (Ba) are some metals.
• Oxygen (O), hydrogen (H), nitrogen (N), sulphur (S), phosphorus (P), fluorine (F), chlorine (Cl), bromine (Br), iodine (I) are some non-metals.

2. Physical Properties of Metals

• Metals in their pure state, have a shining surface. This property is called metallic lustre.
• Metals can be beaten into thin sheets. This property is called Gold and silver are the most malleable metals.
• Metals have ability to be drawn into thin wires. This property is called ductility. Gold is the most ductile metal.
• Metals are good conductors of heat and have high melting points. The best conductor of heat are silver and copper. Lead and mercury are comparatively poor conductors of heat.
• The metals that produce a sound on striking a hard surface are said to be
• Alkali metal (Li, Na, K) are so soft that they can be cut with a knife. They have low densities and low melting points.
• Metals have high melting point but gallium and caesium have very low melting points. These two metals will melt if you keep them on your palm.

3. Physical Properties of Non-Metals

• Non-metal are either solids or gases except bromine which is a liquid.

4. Some other exceptions:

• Iodine is a non-metal but it is lustrous.
• Carbon is a non-metal which exist in two allotropic forms: diamond and graphite. Diamond is the hardest substance with a very high melting point. Graphite is a conductor of electricity.

5. Chemical Properties of Metals

I. All metals combine with oxygen to form metal oxides.
Metal + Oxygen → Metal oxide
For example,
2Cu + O₂ → 2CuO
4Al + 3O₂ → 2Al₂O₃

6. Remember
Different metals exhibit different reactivity towards oxygen. Metals such as K and Na react so vigorously that they catch fire if kept in the open. Hence, to protect them they are kept immersed in kerosene oil.

Generally metal oxides are basic in nature. But some oxides like aluminium oxide, zinc oxide show both acidic as well as basic behaviour.

Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalies. Sodium oxide and potassium oxide dissolve in water to produce alkali as follows:

Na₂O(s) + H₂O(l) → 2NaOH(aq)
K₂O(s) + H₂O(l) → 2KOH(aq)

II. Metals react with water and produce a metal oxide and hydrogen gas. Metal oxides that are soluble in water dissolve in it further to form metal hydroxide. But all metals do not react with water.

Metal + Water → Metal Oxide + Hydrogen
Metal Oxide + Water → Metal hydroxide

Potassium and sodium react violently with cold water. The reaction is exothermic, so the released hydrogen catches fire immediately.

2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g) + Heat
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Heat

The reaction of calcium with water is less violent. The heat evolved is not sufficient for the hydrogen to catch fire.
Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
Mg(s) + 2H₂O(l) → Mg(OH)₂(aq) + H₂(g)

• Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
• Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen.

Aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

2Al(s) + 3H₂O(g) → Al₂O₃(s) + 3H₂(g)
3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

Lead, copper, silver and gold do not react with water at all.

III. Metals react with acids to give a salt and hydrogen gas.
Metal + Dilute acid → Salt + Hydrogen

• Hydrogen gas is not evolved when a metal reacts with HNO₃. It is because HNO₃ is a strong oxidising agent. It oxidises the H₂ produced to water and itself get reduced to any of the nitrogen oxides.
• Magnesium (Mg) and manganese (Mn) react with very dilute HNO₃ to evolve H₂
• Copper does not react with dilute HCl.

IV. Reactive metals can displace less reactive metals from their compounds in solution or molten form.

Metal A + Salt solution of B → Salt solution of A + Metal B

Fe + CuSO₄ → FeSO₄ + Cu
Zn + CuSO₄ → ZnSO₄ + Cu
Reactivity of metal can be explained on the basis of displacement reactions

7. Knowledge Plus
Aqua regia (Latin for ‘royal water) is a freshly prepared mixture of concentrated HCl and concentrated nitric acid in the ratio of 3:1. It is a highly corrosive, fuming liquid and dissolve gold and platinum.

8. The Reactivity Series
The reactivity series is a list of metals arranged in the order of their decreasing activities.

Metals occupying higher position in the series have more tendency to lose electrons and are more reactive. The metals at the bottom of the series are least reactive. Thus, potassium is the most reactive metal.

9. How do metals and non-metals react?

Reactivity is the tendency of elements (metals and non-metals) to attain a completely filled valence shell. Metal atoms having 1, 2 or 3 electrons in their outermost shell can lose electrons to non-metal atoms having 5,6 or 7 electrons to attain the electronic configuratìoñ of the nearest noble gas (i.e., completely filled valence shell).

Thus the metal atom becomes a positively charged ion or cation and the non-metal atom becomes a negatively charged ion or anion. The cation and anion being oppositely charged attract each other and are held by strong electrostatic forces of attraction to exist as an ionic compound. For example,

Metal ore heated strongly in limited or no supply of air (Calcination).

10. Reduction of Metal Oxide:

(i) Using coke: Coke as a reducing agent.

(ii) Using displacement reaction: Highly reactive metals like Na, Ca and A1 are used to displace metals of lower reactivity from their compounds. These displacement reactions are highly exothermic.

11. Thermite Reaction: Reduction of a metal oxide to form metal by using aluminium powder as a reducing agent. This process is used to join broken pieces of heavy iron objects or welding.

12. Extracting Metals at the Top of the Activity Series:

• These metals have more affinity for oxygen than carbon so they cannot be obtained from their compounds by reducing with carbon.
• They are obtained by electrolytic reduction, for example, Sodium is obtained by electrolysis of its molten chloride                     NaCl→ Na⁺ + Cl^–

As electricity is passed through the solution, metal gets deposited at the cathode and non-metal at the anode.

• At cathode: Na⁺ + e^– →Na
• At anode: 2Cl^– →Cl₂ (g) + 2e^–

III. Refining of Metals

• Impurities present in the obtained metal can be removed by electrolytic refining.

Copper is obtained using this method. Following are present inside the electrolytic tank.

• Anode – slab of impure copper
• Cathode – slab of pure copper
• Solution – aqueous solution of copper sulphate with some dilute sulphuric acid.
• From anode, copper ions are released in the solution and equivalent amount of copper from solution is deposited at cathode.
• Insoluble impurities containing silver and gold gets deposited at the bottom of anode as anode mud.

13. Corrosion

• Metals are attacked by substances in the surroundings like moisture and acids.
• Silver—It reacts with sulphur in air to form a black coating of silver sulphide.
• Copper—It reacts with moist carbon dioxide in air and forms a green coating of copper carbonate.
• Iron—acquires a coating of a brown flaky substance called rust. Both air and moisture are necessary for rusting of iron. Rust is hydrated Iron (III) oxide e., Fe₂O₃.xH₂O

14. Prevention of Corrosion

• Rusting of iron is prevented by painting, oiling, greasing, galvanizing, chrome plating, anodising and making alloys.
• In galvanization, iron or steel is coated with a thin layer of zinc. Zinc oxide formed due to oxidation is impervious to air and moisture protecting further layers from corrosion.

15. Alloys: These are homogeneous mixture of metals with metals or non-metals.
Adding small amount of carbon makes iron hard and strong.

Name of Alloy	Properties	Constituent metal/ Non-metal
1. Steel	Hard	Iron and carbon
2. Stainless steel	Hard, rust free	Iron, nickel and chromium
3. Brass	Low electrical conductivity than pure metal	Copper and zinc
4. Bronze	Hard and easily cast	Copper and tin
5. Solder	Low MP, used to weld wires	Lead and tin
6. Amalgam	Used by dentists	Mercury and any other metal

Class 10 Science Chapter 3 Notes Important Terms

Corrosion is the eating up of metals by the action of air, moisture or a chemical on their surface.

Rust is mainly hydrated iron (III) oxide Fe₂O₃.xH₂O due to corrosion.

Ores are the minerals from which metals can be extracted conveniently and profitably.

Minerals are natural materials in which the metals or their compounds are found in the Earth.

Covalent bond is the chemical bond formed by sharing of electrons between two atoms. Aqua-regia is a freshly prepared mixture of 1 part of concentrated nitric acid and 3 parts of concentrated hydrochloric acid.

Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin.

Metallurgy is the process of extraction of a metal from its ore and its refining.

Activity series is the arrangement of metals in the order of decreasing reactivity.

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CBSE Class 9 Science Chapter 6 Notes Tissues

Tissues Class 9 Notes Understanding the Lesson

1. A single cell performs all the basic functions like digestion, respiration, excretion, etc. in order to sustain life in the unicellular organisms like Amoeba. In multicellular organisms like human beings, each specialised function to sustain life is taken up by a different group of cells.

2. Division of labour: The multicellular organisms show division of labour as each function is carried out by a cluster of specialised cells at a definite place in the body.
For example:
In human beings, muscle cells contract and relax to cause movement, nerve cells carry messages, blood flows to transport oxygen, etc. In plants, vascular tissues called xylem and phloem conduct water and food respectively from one part of the plant to the other parts.

3. Tissue: A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue. Example: Blood, phloem and muscle. Plant tissues are classified as growing or meristematic tissue and permanent tissue.

4. Meristematic tissue: This tissue consists of cells which continuously divide to produce new cells. The cells of this tissue are very active, lack vacuoles, have dense cytoplasm, thin cellulosic cell walls and prominent nuclei.

5. Location of meristematic tissue: This tissue is present only at specific regions of the plant like the root tip, shoot tip and at the base of intemodes and leaves.

6. Types of meristematic tissue: They are classified as apical, lateral and intercalary meristematic tissue based on the region where they are present.

• Apical meristem: It is present at the growing tips of stems and roots and results in increase in the length of the stem and the root.
• Lateral meristem (cambium): It helps to increase the girth of the stem or root.
• Intercalary meristem: It is present at the base of the leaves or intemodes.

5. Permanent tissue: Consists of cells which have taken up a specific role and lost the ability to divide.
It is of two types:

• Simple tissue: It is made up of only one type of cells. Its three types are: parenchyma, collenchyma and sclerenchyma.
• Complex tissue: It is made up of more than one type of cells. They are the conducting tissues called xylem and phloem.

6. Differentiation: The process of taking up a permanent shape, size, and a function by the cells is called differentiation.

7. Types of simple tissue:
(a) Parenchyma: They are loosely packed living cells, with thin cell walls and large intercellular spaces. They provide support to plants and store food. It is called chlorenchyma if it contains chlorophyll and performs photosynthesis. The parenchyma of aquatic plants have large cavities to provide buoyancy to the plants to help them float. Such type of parenchyma is called aerenchyma.

(b) Collenchyma: It consists of living, elongated cells that are irregularly thickened at the corners and have a very little intercellular space. It allows easy bending in various parts of a plant (leaf, stem) without breaking. It also provides mechanical support to plants like in the leaf stalks below the epidermis.

(c) Sclerenchyma: This tissue consists of dead cells which makes the plant hard and stiff. The cells are long and narrow as the walls are thickened (often so thick that there is no internal space inside the cell) due to lignin (a chemical substance which acts as cement and hardens them). This tissue provides strength to the plants and is present in stems, around vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts.

8. Epidermis: The outermost layer of cells covering an organism is called epidermis. It is usually made up of a single layer of cells and gives protection. The epidermis may be thicker in some plants living in dry habitats or often secrete a waxy, water-resistant layer on their outer surface called cutin (chemical substance with waterproof quality) to prevent water loss.

The epidermis of leaves have small pores called stomata which are enclosed by two kidney shaped cells called guard cells. Stomata help in gaseous exchange and transpiration. The epidermal cells of roots bear root hairs that greatly increase the total absorptive surface area of the roots for absorption of water.

9. Cork: A strip of secondary meristem replaces the epidermis of the older stem and cuts off cells towards outside to form a several-layer thick cork or the bark of the tree. Cells of cork are dead, compactly arranged without intercellular spaces and have a chemical called suberin in their walls that makes them impervious to gases and water.

10. Complex Permanent Tissue: These tissues are made of more than one type of cells which coordinate to perform a common function, e.g., Xylem and phloem. They are mainly conducting tissues and constitute a vascular bundle.

(a) Xylem: Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres. All the cells of xylem except the xylem parenchyma are dead. Xylem helps to transport water and minerals. Tracheids and vessels help in vertical transport whereas the parenchyma stores food and helps in the sideways conduction of water. Fibres are mainly supportive in function.

(b) Phloem: Phloem has four elements called sieve tubes, companion cells, phloem fibres and the phloem parenchyma. All cells of phloem are living except the phloem fibres. Phloem transports food from leaves to other parts of the plant.

11. Animal Tissues: The animal tissues are of four types: epithelial tissue, connective tissue, muscular tissue and nervous tissue.

12. Epithelial Tissue: They are the covering or protective tissues and cover most organs and cavities in the animal body. These cells are tightly packed, form a continuous sheet and are almost without any intercellular spaces between them. e.g., skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all made of epithelial tissue. All epithelium is usually separated from the underlying tissue by an extracellular fibrous basement membrane. The types of epithelium on the basis of their structure and functions are:

(a) Squamous epithelium: Consists of flattened cells. Present in oesophagus and lining of the mouth. Skin epithelial cells are arranged in many layers to prevent wear and tear and are called as stratified squamous epithelium.

(b) Columnar epithelium: Has tall or ‘pillar-like’ cells. It forms inner lining of the intestine.

(c) Cuboidal epithelium: Has cube-shaped cells. It forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support.

(d) Ciliated epithelium: Have cilia on the outer surfaces of epithelial cells. The cilia can move and their movement pushes the mucus in the respiratory tract forward to clear it.

(e) Glandular epithelium: Has gland cells which secrete substances at the epithelial surface.

13. Connective Tissue: The cells of connective tissue are loosely spaced and embedded in an intercellular matrix which may be jelly like, fluid, dense or rigid, e.g., blood, bone, cartilage, etc.

(a) Blood: It has a fluid (liquid) matrix called plasma having red blood cells (RBCs), white blood cells (WBCs) and platelets. Blood helps in the transport of gases, digested food, hormones and waste materials to different parts of the body.

(b) Bone: It has bone cells embedded in a hard matrix composed of calcium and phosphorus compounds. It is a strong and non-flexible tissue which forms a framework that supports the body, anchors the muscles and supports the main organs of the body.

(c) Cartilage: It has widely spaced cells and a solid matrix composed of proteins and sugars. It helps to smoothen bone surfaces at joints and is also present in the nose, ear, trachea and larynx.

(d) Areolar connective tissue: It fills the space inside the organs, supports internal organs and helps in repair of tissues. It is found between the skin and muscles, around blood vessels and nerves and in the bone marrow.

(e) Adipose tissue: It is a fat storing tissue having cells filled with fat globules. It is found below the skin and between the internal organs.

(f) Ligament: It is the connective tissue which connects two bones. This tissue has very little matrix, is very elastic and has considerable strength.

(g) Tendon: It is the connective tissue which connects muscles to bones. It is a fibrous tissue with great strength but limited flexibility.

14. Muscular Tissue: This tissue is responsible for movement in our body and consists of elongated cells, also called muscle fibres. Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.

(а) Striated Muscles: These muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement. These muscles show alternate light and dark bands. These are long, cylindrical, unbranched and multinucleate. These are voluntary muscles as we can move them by conscious will, e.g., muscles of our limbs.

(b) Unstriated Muscles: They are also called smooth muscles or unstriated muscles as they do not have light and dark bands. The cells are long, uninucleate, involuntary in nature and spindle shaped. They are present in iris of the eye, ureters, blood vessels, alimentary canal and bronchi of lungs.

(c) Cardiac Muscles: These are the muscles of the heart which show rhythmic contraction and relaxation throughout life. They are involuntary, cylindrical, branched and uninucleate.

15. Nervous Tissue: The cells of this tissue are called nerve cells or neurons. Each neuron consists of a cell body with a nucleus and cytoplasm, a single long part called the axon, and many short branched parts called dendrites. The cells of the nervous tissue are highly specialised for transmitting the stimulus from one place to another within the body on being stimulated. The brain, spinal cord and nerves are composed of the nervous tissue. A nerve consists of many nerve fibres bound together by connective tissue.

Class 9 Science Chapter 6 Notes Important Terms

Tissue: A group of cells that are similar in structure and/or work together to achieve a particular function.

Meristematic tissue: This tissue that consists of cells which continuously divide to produce new cells.

Permanent tissue: The tissue which consists of cells which have taken up a specific role and lost the ability to divide.

Differentiation: The process of taking up a permanent shape, size, and a function by the cells is called differentiation.

Chlorenchyma: Parenchyma which contains chlorophyll and performs photosynthesis.

Aerenchyma: Parenchyma which contains large cavities to provide buoyancy to the aquatic plants to help them float.

Cambium: It is a lateral meristem which helps in increasing the girth of the stem or root.

Lignin: A chemical substance which acts as cement and hardens the cells of sclerenchyma.

Cutin: A chemical substance with waterproof quality present in epidermis of leaves to prevent water loss by transpiration.

Suberin: A chemical present in the walls of cork cells that makes them impervious to gases and water.

Adipose tissue: It is a fat storing tissue having cells filled with fat globules.

Ligament: It is the connective tissue which connects two bones. This tissue has very little matrix, is very elastic and has considerable strength.

Tendon: It is the connective tissue which connects muscles to bones. It is a fibrous tissue with great strength but limited flexibility.

Contractile proteins: Special proteins present in muscles which contract and relax to cause movement of body parts.

Nerve: A nerve consists of many nerve fibres bound together by connective tissue.

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CBSE Class 10 Maths Chapter 13 Notes Surface Areas and Volumes

Surface Areas and Volumes Class 10 Notes Understanding the Lesson

Surface area: Surface area of an object is the measure of the total area that the surface of an object occupies.

Volume: Volume of an object is the measure of space occupied by the object.

Basic Solids: In standard X, we have studied the surface area and volume of solids. Here we will study more about them.

1. Cuboid
(i) Surface area of cuboid = 2(lb + bh + lh) sq.unit
where l is the length
b is the breadth
h is the height

(ii) Area of four walls of cuboid
= 2(l + b) x h
= [Perimeter of floor x Height] sq. unit

(iii) Surface area of cuboid without roof or lid
= lb + 2 [bh + Ih] sq. unit

(iv) Volume of cuboid = l x b x h unit

(v) Diagonal of cuboid or length of longest rod kept =\(\sqrt{l^{2}+b^{2}+h^{2}}\)unit

2. Cube
Let each edge of a cube be of length a unit. Then
(i) Surface area of cube = 6 side² = 6a² unit

(ii) Surface area of four walls of cube = 4 side²
= 4a² sq. unit

(iii) Surface area of a cube without lid (or rod) of a cube
= 5a² sq. unit.

(iv) Length of longest diagonal (or rod) of a cube
\(=\sqrt{a^{2}+a^{2}+a^{2}}=\sqrt{3}\) aunit

(v) Volume of cube = a³ unit

3. Cylinder

(i) Curved surface area of cylinder = 2πr x h
= Perimeter of base x height sq. unit

(ii) Total surface area of cylinder
= CSA + Area of 2 circular ends of cylinder
= 2πrh + 2πr² = 2πr (r + h)

(iii) Volume of cylinder =πr²h

(iv) Volume of material in hollow pipe = Exterior volume – Interior volume
= πR²h – πr²h = πh [R² – r²]

(v) Total surface area of hollow cylinder
= CSA of outer and inner cylinder + 2(area of base ring)
= 2πRh + 2πrh + 2(πR² – πr²)
= 2π(R + r)h + 2π(R² – r²) = 2π(R + r) (h + R – r)

Note:

• Two ends of cylinder are circles having each area = πr²
• Mass of cylinder = Volume of cylinder x Density
  M = V x ρ

4. Cone

h – OA = height of cone
r = OB = radius of cone
l = AB = slant height of cone

(i) \(l=\sqrt{r^{2}+h^{2}}\) units

(ii) Curved surface area of cone or lateral
surface area of cone = πrl sq. unit

(iii) Total surface area of cone = CSA + Area of circular base
= πrl + πr² – πr(r + l) sq. unit

(iv) Volume of cone =\( \frac{1}{3}\) πr²h cu.unit

5. Sphere

• Surface area of sphere = 4πr² unit
• Volume of sphere = \( \frac{4}{3}\)cu.unit

6. Hemisphere

• Curved surface area of hemisphere = 4πr² sq unit
• Volume of hemisphere = \( \frac{2}{3}\) πr² cu unit
• Total surface area of hemisphere = 2πr² + πr² = 3πr² sq. unit

7. Spherical shell

(i) Total surface area of spherical shell = 4πR² + 4πr²
= 4πr(R² + r²) sq. unit

(ii) Volume of spherical shell = \( \frac{4}{3}\)π(R³– r³) cu . unit

Shapes of Frustum

(i) Slant height of frustum = \(\sqrt{(\mathrm{R}-r)^{2}+h^{2}}\) unit
(ii) Curved surface area of frustum = π(R + r)l sq. unit
(iii) Total surface area of frustum of cone
= πl (R + r) + πR² + πr² sq. unit

(iv) Volume of frustum of cone = \(\frac{1}{3}\)πh (R² + r² + Rr) sq. unit

Volume of Combination Solids

The volume of the solid formed by joining two basic solids will actually be the sum of the volumes of the two basic solids.

Conversion of Solid from One Shape to Another

If we melt the candle in the shape of cylinder and pour it into a conical vessel, then it changes into the conical shape. Thus, volume of cylindrical candle = Volume of conical solid.

On this page, you will find Acids Bases and Salts Class 10 Notes Science Chapter 2 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 2 Acids Bases and Salts will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 2 Notes Acids Bases and Salts

Acids Bases and Salts Class 10 Notes Understanding the Lesson

1. Acids and Bases: Acids are sour in taste and change the colour of blue litmus to red. The term has been derived from the Latin word ‘acidus’ which means sour taste. Generally acids have atleast one or more hydrogen atoms in their formulae.

An acid may be defined as a chemical substance which releases one or more H⁺ or HsO⁺ ions in aqueous solution.
For example, HCl, HNO₃, H₂SO₄, etc.

Bases are bitter and change the colour of the red litmus to blue. Generally bases have one or more hydroxyl (OH^–) groups. They produce hydroxyl ions (OH^–) when dissolved in water.

A base may be defined as a chemical substance which releases one or more OH^– ions in aqueous solution.
For example, NaOH, KOH, etc.

• Acid-Base indicator: Natural/synthetic materials which indicate the presence of acid or base in a solution, are called acid base indicator or simply indicator.
• Litmus solution: It is a purple dye which is extracted from lichen, a plant belonging to the division
  .
• Phenolphthalein: It is a colourless organic dye in acidic or neutral medium but it changes to pink in basic medium.
• Methyl orange: It is an orange coloured dye and keeps this colour in the neutral medium. In the acidic medium, the colour of the indicator becomes red and in the basic medium, it changes to yellow.
• Red cabbage juice: Its colour remains red in acidic medium but changes to green if the medium is basic or alkaline.
• Turmeric solution: It is a yellow dye and in the acidic as well as neutral medium, its colour remains yellow. In the basic medium the colour changes to reddish brown.

2. Olfactory indicators: These are chemical substances whose odour changes in acidic or basic medium.
For example, onion, vanilla and clove oil.

3. Reaction of acid or base with metal: Metals react with acids to liberate hydrogen gas and form salt.
Acid + Metal → Salt + Hydrogen gas

A few metals like zinc, lead and aluminium react with bases to give off hydrogen.

4. Reaction of acids with metal hydrogen carbonate and metal carbonates: All metal carbonates and hydrogen carbonates react with acids to give the corresponding salt, carbon dioxide and water.

Metal carbonate + Acid → Salt + H₂O + CO₂
Metal hydrogen carbonate + Acid → Salt + H₂O + CO₂

For example,
Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)
NaHCO₃(s) + HCl(ag) → NaCl(aq) + H₂O(Z) + CO₂(g)

The released CO₂ gas turns lime water milky due to formation of CaCO₃.

On passing excess CO₂, the milky white precipitate dissolves in water.

5. Neutralisation reaction: A chemical reaction between an acid and a base to give a salt and water is known as neutralisation reaction. In general neutralisation reaction can be written as

Base + Acid → Salt + Water
NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)

(i) Reactions of metal oxides with acids

(ii) Reactions of non-metallic oxide with base
Non-metallic oxide + Base→ Salt + Water
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O

How strong are acid or base solutions: Any aqueous solution, be it acidic, alkaline or neutral, will have both H⁺ and OH^– ions.
The  solution will be acidic or alkaline depending upon which of the two ions is present in larger concentration.

A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. pH scale was given by a Danish chemist Sorensen. The p in pH stands for ‘potenz’ in German meaning ‘power’.

pH should be thought of simply as a number between 0-14 which indicates the acidic or basic nature of a solution. Higher the hydrogen ion concentration, lower is the pH value.

Knowledge +
pH = negative logarithm to the base 10 of the H⁺ ion concentration.
The concentration is in mol/dm³. pH = – log H⁺

Remember: Every one fold change in the pH scale brings about a ten-fold change in H⁺ ion concentration. The strength of acids and bases depends on the concentration of H⁺ ion and OH^–.

If we take two acids HCl and CH₃COOH of the same concentration, then they produce different amount of H⁺. Acids that give rise to more H⁺ ions are said to be strong acids and acids that give less H⁺ ions are said to be weak acids.

6. Importance of pH in everyday life:

(i) If pH of rain water is less than 5.6, it is called acid rain. When acid rain flows into the rivers, it lowers the pH of river water. The survival of aquatic life in such rivers become difficult. Acid rain also damage crops and cause a change in pH of the soil.

(ii) pH in our digestive system: Our stomach produces digestive juices/hydrochloric acid (HCl), which helps in the digestion of food without harming the stomach. However, sometimes the stomach produces too much of acid and this causes indigestion, which is accompanied by pain and irritation. To get rid of this pain, people use antacids like magnesium hydroxide. These antacids neutralise the excess acid formed.

(iii) pH change as the cause of tooth decay: Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium phosphate is the hardest substance in the body. It does not dissolve in water but is corroded when the pH in the mouth is below 5.5. Using toothpaste, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

(iv) Bee-sting leaves an acid which causes pain and irritation. Using a mild base like baking soda on the stung area gives relief. Stinging hair of nettle leaves inject methanoic acid causing a burning pain. A traditional remedy is rubbing the area with the leaf of the dock plant.

(v) Various fluids in our body work within a particular range of pH such as, pH of human blood should be between 7.3 to 7.5.

(vi) For the growth of plants, a particular pH range of soil is essential. Usually neutral soil is best for crops. If the soil is acidic, farmers treat the soil with quick lime or slaked lime.

(vii) The tarnished surface of a copper vessel due to the formation of copper oxide layer (which is basic) can be cleaned by rubbing with lemon (which is acidic).

7. Salts: Salts are generally ionic compounds which are obtained by neutralisation reaction between acids and bases.

Acid + Base→ Salt + Water
HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(Z)

In these salts, the cation is derived from base and anion is derived from acid.
Salts are mostly solids with high melting points. They are soluble in water.

Different types of salts:

• Normal salts : NaNO₃
• Acidic salts : NaHSO₄
• Basic salts : Pb(OH)Cl
• Double salts : FeSO₄.(NH₄)₂.SO₄.6H₂O

8. Remember: Salts of a strong acid and a strong base are neutral with pH value of 7. On the other hand, salts of strong acid and weak base are acidic with pH values less than 7 and those of strong base and weak acid are basic in nature, with pH value more than 7.

Common Salt (NaCl) [Table salt]
Sodium chloride (NaCl) also called common salt or table salt is the most common/essential part of our diet. It is obtained by neutralisation reaction of sodium hydroxide (NaOH) with hydrochloric acid (HC1).

It is obtained on a large scale from sea water.
Large crystals are often brown due to the presence of impurities. This is called rock salt. Beds of rock salt were formed when seas of by gone ages dried up. Rock salt is mined like coal.

9. Uses of Sodium Chloride

• Sodium chloride is a major ingredient of edible salt.
• It is used as a food preservative.
• Compounds like sodium hydroxide (NaOH), baking soda (NaHCO₃) and washing soda are obtained from sodium chloride.
• It is used to melt ice on hill stations and cold countries during heavy snow fall.

10. Sodium Hydroxide (NaOH): Sodium hydroxide (NaOH) is commonly known as caustic soda.

Sodium hydroxide is manufactured by electrolysis of an aqueous solution of sodium chloride (called brine). Chlorine gas is given off at the anode and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.
2NaCl(aq) + 2H₂O(l) → 2NaOH(ag) + Cl₂(g) + H₂(g)

The process is called the chlor-alkali process because of the products formed chlor for chlorine and alkali for sodium hydroxide.

11. Uses of Sodium Hydroxide

1. Sodium hydroxide is used for making soaps and detergents.
2. Sodium hydroxide is used for making artificial textile fibres (such as rayon).
3. It is used the preparation of soda lime (a mixture of NaOH and CaO).
4. It is used as a cleansing agent for machines and metal sheets.

12. Baking Soda (NaHCO_s): The chemical name of baking soda is sodium hydrogencarbonate or sodium bicarbonate (NaHCO₃). It can be prepared from sodium chloride as
NaCl + H₂O + CO₂ + NH₃→ NH₄Cl + NaHCO₃

Since it is slightly soluble in water, it can be removed by filtration.
It is a mild non-corrosive base. The following reaction takes place when it is heated during cooking.

13. Uses of Baking Soda
Being alkaline it is an ingredient in antacids. It neutralises excess acid in the stomach and provides relief.
NaHCO₃ + HCl → NaCl + H₂O + CO₂

• It is used in soda-acid fire extinguisher.
• It is used in making baking powder (a mixture of baking soda and mild edible acid like tartaric acid). When baking powder is heated or mixed in water CO₂ gas is released.
  NaHCO₃ + H⁺→ CO₂ + H₂O + Sodium salt of acid

The released CO₂ causes breads or cakes to rise making them soft and spongy/fluffy.

14. Bleaching Powder [CaOCl₂]: Bleaching powder is calcium oxychloride. It is also known as chloride of lime. Bleaching powder can be prepared by the action of chlorine on dry slaked lime [Ca(OH₂)].
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Bleaching powder is a yellowish white solid.

15. Uses of Bleaching Powder

• It is an oxidising agent.
• It is used for disinfecting drinking water to make it free from germs.
• The most important use of bleaching powder is in:
• textile industry for bleaching cotton and linen
• paper industry for bleaching wood pulp
• laundry for bleaching washed clothes.

16. Washing Soda [Na₂Og.10H₂O]: Sodium carbonate is obtained by heating baking soda. When the sodium carbonate obtained by the above process is recrystallised, we get washing soda.
Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O
Anhydrous sodium carbonate is called soda ash.

17. Uses of Washing Soda

• It is used in glass, soap and paper industries.
• It is used in the manufacture of borax.
• It is used as a cleaning agent for domestic purposes.
• It is used for removing permanent hardness of water.

18. Plaster of Paris \(\left(\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}\right)\)
Plaster of Paris is calcium sulphate hemihydrate, it can be obtained by heating gypsum at 373 K.
Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass.

19. Knowledge Booster
In washing soda, (Na₂CO₃.10H₂O), 10H₂O signify water of crystallisation. Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt. Some other examples are

20. Uses of Plaster of Paris

• Plaster of Paris is used by doctors as plaster for supporting fractured bones in the right position.
• It is also used for making toys, materials for decoration and for making surfaces smooth.

Class 10 Science Chapter 2 Notes Important Terms

Alkalies are water soluble bases.

Rock salt is chemically sodium chloride (NaCl).

Antacid is a substance which can neutralise acidity in the stomach.

Neutralisation is the reaction in which an acid reacts with a base to form salt and water.

Bleaching powder is chemically calcium oxychloride (CaOCl₂) and is formed by passing chloride gas through dry slaked lime.

Amphoteric compound is a compound that can act both as an acid and a base.

Dilute Acid: Contains only a small amounts of acid and a large amount of water.

Concentrated Acid: A concentrated acid contains a large amount of acid and a small amount of water.