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Category: Class 9th

  • Structure of the Atom Notes Class 9th Science Chapter 4

    CHAPTER -4 “STRUCTURE OF ATOM” CONCEPTDETAILS

    KEY CONCEPTS : [ *rating as per the significance of concept]

    1. Dalton’s Atomic theory **
    2. J J Thomson Experiments ***
    3. Rutherford’s Scattering Experiments ********
    4. Sub atomic particles ******
    5. Atomic number & Mass number *****
    6. Neil Bohr’s Atomic Model ***
    7. Electronic Configuration & Valency *******
    8. Isotopes & Isobars ****

    • Pre requisites:
    • Difference between an atom & molecule.
    • Gram atomic mass & Molar mass.
    • Dalton’s Atomic theory.

    SURVEY ANALYSIS

    Conceptual levels of comprehension on the basis of feedback taken from the students


    • First recorded evidence that atoms existed.
    • Using his theory, Dalton rationalized the various laws of chemical combination

    Dalton’s theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights.

    • Limitations

    o The indivisibility of an atom was proved wrong , for, an atom can be further subdivided into protons, neutrons and electrons. o The atoms of same element are similar in all respects , but isotopes of same element have different mass.

    Dalton’s theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights.

    • An electron is a negatively charged component of an atom which exists outside the nucleus. Each electron carries one unit of negative charge and has a very small mass as compared with that of a neutron or proton.

    Effects of Electric Field on Cathode Rays

    JJ Thomson used cathode ray tubes to demonstrate that the cathode ray responds to both magnetic and electric fields.

    Since the ray was attracted to a positive electric plate placed over the cathode ray tube (beam deflected toward the positive plate) he determined that the ray must be composed of negatively charged particles.

    He called these negative particles “electrons.”

    Limitation: Model failed to explain how protons and electrons were arranged in atom so close to each other.


    Eugene Goldstein:

    • E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge and called them canal rays. These rays were positively charged radiations which ultimately led to the discovery of another sub-atomic particle.
    • Used a Cathode Ray Tube to study “canal rays” which had electrical and magnetic properties opposite of an electron
    • Canal Rays: The positively charged radiation produced in the discharge tube at low pressure and high voltage are called canal rays.

    Protons:

    The canal rays have positively charged sub-atomic, particles known as protons (p).

    Q.1 What was the model of an atom proposed by Thomson? Q.2 What is the nature of charge on electrons?

    Q.3 What are canal rays ?

    Q.4 State the nature of the constituents of canal rays.


    Experiment: Rutherford took a thin gold foil and made alpha particles , [ He2+ ] positively charged Helium fall on it.

    S.No OBSERVATION INFERENCE
    1. Most of the a-particles passed through Most of the space inside the atom is
    the gold foil without getting deflected. empty.
    2. Very few particles were deflected. Positive charge of the atom occupies
    very little space.
    3. A very few alpha particles, 1 in 100000 Nucleus of an atom is very small as
    completely rebound on hitting the gold compared to the total size.
    foil.

    • Limitation: In Rutherford’s atomic model , Nucleus & electrons are held together by electrostatic force of attraction which would lead to the fusion between them. This does not happen in the atom.

    Atomic radius ~ 100 pm = 1 x 10-10 m Nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m

    • In 1932, James Chadwick proved that the atomic nucleus contained a neutral particle which had been proposed more than a decade earlier by Ernest Rutherford officially discovered the neutron in 1932,
    • Chadwick received the Nobel Prize in 1935.

    A neutron is a subatomic particle contained in the atomic nucleus. It has no net electric charge, unlike the proton’s positive electric charge.

    Q.1 Who discovered the nucleus of the atom?

    Q.2 What is the charge on alpha particles ?

    Q.3 Which observation of Rutherford’s scattering experiment established the presence large empty space in atom?

    Q.4 What is the nature of charge on nucleus of atom?

    Q.5 Who discovered neutron ?

    1. Sub Atomic Particles:
    Name Symbol Location in the atom Charge Relative Mass Actual Mass (g)
    Electron E Around the nucleus 1- 1/1840 9.11 x 10 -28
    Proton P In the nucleus 1+ 1 1.67 x 10 -24
    Neutron n In the nucleus 0 1 1.67 x 10 -24

    Protons & Neutrons collectively are known as NUCLEONS.

    Q.1 Why is the relative mass of an electron is taken as negligible ? Q.2 Give the actual masses of electron & proton in kg?

    Q.3 What are nucleons?

    1. Atomic Number & Mass Number:

    “Atomic number of an element is defined as the number of unit positive charges on the nucleus (nuclear charge) of the atom of that element or as the number of protons present in the nucleus.”

    Atomic number, Z = Number of unit positive charge on the nucleus = Total number of unit positive charges carried by all protons present in the nucleus.

    = Number of protons in the nucleus (p)

    = Number of electrons revolving in the orbits (e)

    Eg :- Hydrogen – Atomic number = 1 (1 proton)

    Helium – Atomic number = 2 (2 protons)

    Mass number[ A] : It is defined as the sum of the number of protons & neutrons present in the nucleus of an atom.

    Mass Number = Mass of protons + Mass of neutrons Eg :- Carbon – Mass number = 12 (6 protons + 6 neutrons) Mass = 12u Aluminium – Mass number = 27 (13 protons + 14 neutrons) Mass = 27u




    Main Postulates of the Bohr Model [refer NCERT Text Book article 4.3 page number-49]

    Q.1 What happens when an electron jumps from lower to higher energy level?

    Q.2 Which energy shell is nearest to the nucleus of an atom?

    Q.3 Which energy shell has higher energy L or N ?

    1. Electronic configuration & Valency: Bohr and Bury Scheme – Important Rules
    S.No Electron Shell 2n2

    where n = shell number

    		 Maximum Capacity
    1 K Shell 2 x (1) 2 2 electrons
    2 L Shell 2 x (2) 2 8 electrons
    3 M shell 2 x (3) 2 18 electrons
    4 N shell 2 x (4) 2 32 electrons

    The outermost shell of an atom cannot accommodate more than 8 electrons, even if it has a capacity to accommodate more electrons. This is a very important rule and is also called the OCTET RULE. The presence of 8 electrons in the outermost shell makes the atom very stable.

    Q.1 An atoms has atomic number 13. What would be its configuration.

    Q.2 What is octet rule?

    Q.3 How many electrons M shell can accommodate?

    Q.4 If an atom has complete K and L shell, what would be its atomic number?

    1. Isotopes & Isobars:
    ISOTOPES ISOBARS
    Chemically same , physically different Chemically different , physically same
    Number of electrons is same Number of electrons is different .
    Cannot be separated by chemical means Can be separated by chemical means

    [ for application of isotopes refer NCERT Text Book article 4.6 page number-53]

    Q.1 Why atoms of isotopes are chemically same?

    Q.2 Give the representation of three isotopes of carbon which are C-12, C-13 and C-14.


    |L_QUESTIONJANKJ^HOTSJJ

    1. Mark Questions:
    2. Write the names of three elementary particles which constitute an atom.
    3. Name the scientist & his experiment to prove that nucleus of an atom is positively charged.
    4. Which is heavier , neutron or proton ?
    5. *How many times a proton is heavier than an electron?
    6. What was the model of an atom proposed by Thomson ?
    7. How many electrons at the maximum can be present in the first shell ?
    8. What type of charge is present on the nucleus of an atom?
    9. Give the number of protons in 35Cl17
    10. *What are iso bars ?
    11. Name the particles which determine the mass of an atom.
    12. Marks Questions:
    13. Define the following terms: a) Atomic number b) Mass number
    14. Write the charges on sub atomic particles.
    15. Identify the isotopes out of A , B , C & D ? 33A17 , 40B20 , 37C17 , 38D19
    16. * Give one Achievement and one limitation of J.J Thomson’s model of atom?
    17. What are valence electrons? Give example.
    18. *Which kind of elements have tendency to lose electron ? Give example.
    19. How many electrons are present in the valence shell of nitrogen & argon?
    20. State the maximum capacity of various shells to accommodate electrons.
    21. Give the symbol , relative charge & mass of the three sub atomic particles.
    22. From the symbol 32 S16 state :

    i) Atomic number of sulphur, ii) Mass number of sulphur iii) Electronic configuration of sulphur.

    1. Marks Questions:
    2. Why do Helium has Zero valency?
    3. An atom contains 3 protons , 3 electrons and 4 neutrons .What is its atomic number , mass number & valency?
    4. *How are the isotopes of hydrogen represented ?
    5. Write the complete symbol for the atom with the given atomic number [Z] & mass

    number[A].

    i) Z= 17 , A = 15 ; ii) Z=4 , A = 9; iii) Z= 92 ; A=233

    1. *What would be the electronic configuration of Na+ , Al3+ , O2- , Cl –.

    5 Marks Questions:

    1. * a) Give the observations as well as inferences of Rutherford’s Scattering experiment for determining the structure of an atom.

    b) On the basis of above experiment write the main features of atomic model.

    1. Write the main postulates of Bohr’s Model of Atom.

    |poUare^xpectedto^now^^^|

    • The scientists who discovered subatomic particles.
    • Rutherford established the existence of nucleus.
    • Difference between Atomic number and Mass number
    • Electronic configuration & its relation with Valency.
    • Difference between Isotope and Isobar.

  • Atoms and Molecules Notes Class 9th Science Chapter 3

    CHAPTER – 3 Atoms and Molecules _concept details

    KEY CONCEPTS : [ *rating as per the significance of concept]

    1. Laws of Chemical Combination

    ***

    2. John Daltons Atomic Theory

    **

    3. Atoms, ions & Chemical Formula

    ****

    4. Mole Concept

    *****

    5. Molar Mass & Avogadro constant

    ****

    Verification of “Law of Conservation of mass”

    l.Laws of Chemical Combination |

    A solution of sodium chloride and silver nitrate are taken separately in the two limbs of an ‘H’ shaped tube. The tube is sealed and weighed precisely. The two reactants are made to react by inverting the tube. The following reaction takes place.

    AgNO3(aq) + NaCl (aq) -> AgCl (s) + NaNO3 (aq)

    The whole tube is kept undisturbed for sometime so that the reaction is complete. When the tube is weighed again it is observed that:

    Weight before the reaction = Weight after the reaction Limitation of “Law of definite proportion”

    This law does not hold good when the compound is obtained by using different isotopes of the combining elements .

    Q.1 Why chemical reactions are in accordance with the Law of conservation of mass? Q.2 Calculate the ratio of atoms present in 5 g of magnesium and 5 g of iron.

    [Atomic mass of Mg=24 u, Fe=56 u]

    1. John Daltons Atomic Theory |

    [ for postulates ,refer NCERT text book article 3.1.2 -page no.32 ]

    Using his theory, Dalton rationalized the various laws of chemical combination which were in existence at that time. However, he assumed that the simplest compound of two elements must be binary.

    Q.1 In what respect does Dalton’s Atomic theory hold good even today?

    Q.2 Which of the following is not the postulate of Dalton’s Atomic theory of matter ?

    1. Each element is made up of extremely small particles called atoms.
    2. Atoms of a given element are identical in chemical properties but have different

    physical properties.

    1. Atoms cannot be created nor destroyed.
    2. Compounds are formed by the chemical union of atoms of two or more elements in fixed proportion .
    3. Atoms ,Molecules, Ions & Chemical Formula |

    Atom

    Molecule

    -o-

    An atom is the smallest particle of an element which can take part in a chemical reaction. It may or may not exist freely.

    The smallest particle of matter (element or compound) which can exist in a free state.

    -0-

    O

    Each atom of an element shows all the properties of the element.

    The properties of a substance are the properties of its molecules.

    • MOLECULES OF ELEMENT: The molecules of an element are constituted by the same type of atoms.
    • MOLECULES OF COMPOUND: Atoms of different elements join together in definite proportions to form molecules of compounds.(hetero atomic molecules)
    • ATOMICITY : The number of atoms contained in a molecule of a substance (element or compound) is called its atomicity.

    Element

    Formula

    Atomicity

    Ozone

    O3

    3

    Phosphorus

    P4

    4

    Sulphur

    S8

    8

    Oxygen

    O2

    2

    • Based upon atomicity molecules can be classified as follows.

    Monoatomic molecules: Noble gases helium, neon and argon exist as He Ne and Ar

    respectively.

    Diatomic molecules: H2 , O2, N2,Cl2, CO , HCl .

    Triatomic molecules: O3 ,CO2 , NO2.

    • SYMBOLS
    • The abbreviation used to represent an element is generally the first letter in capital of the English name of element.

    Oxygen -> O Nitrogen -> N

    • When the names of two or more elements begin with the same initial letter, the initial letter followed by the letter appearing later in the name is used to symbolize the element

    Barium -> Ba Bismuth -> Bi

    Symbols of some elements are derived from their Latin names

    ELEMENT

    LATIN NAME

    SYMBOL

    Sodium

    Natrium

    Na

    Copper

    Cuprum

    Cu

    Potassium

    Kalium

    K

    Iron

    Ferrum

    Fe

    Mercury

    Hydragyrum

    Hg

    Tungsten

    Wolfram

    W

    Q.1 Give one example each of molecule of element & molecule of compound.

    Q.2 How does an atom differ from molecule ?

    Q.3 Name a triatomic gas.

    Q.4 Name the element represented by Hg, Pb, Au.

    Q.5 What is the difference between an atom of hydrogen and a molecule of hydrogen?

    Polyatomic Ion : A group of atoms carrying a charge is as polyatomic ion.

    eg: NH4+ – Ammonium Ion ; CO32- – Carbonate ion

    Valency : The number of electrons which an atom can lose , gain or share to form a bond.

    OR

    It is the combining capacity of an atom of the element.

    [ for valency of various cations & anions ,refer NCERT text book table 3.6, page no. 37 ]

    ♦♦♦ Chemical Formula: A chemical formula is a short method of representing chemical elements and compounds.

    Writing a Chemical Formula -CRISS-CROSS rule

    [ b]

    RULE 1 [a]

    write the correct symbols of two elements.

    Ex : Aluminium & Oxygen

    Al O

    above each symbol, write the correct valence

    Al3+ O2-

    [c]

    Criss-cross the valence and drop the algebraic sign.

    Al2O3

    RULE 2 >

    When the subscript is number 1, subscript is not written.

    Ex. Sodium Chloride

    – Na1+ Cl1- — NaCl

    RULE 3> When the valence of both elements are numerically equal , the subscripts are also not written.

    Ex. Calcium Oxide- – Ca2+ O2- — CaO

    RULE 4 > When there are multiple numbers of an individual polyatomic ion ,

    parentheses must be used to separate the polyatomic ion from the subscirpt.

    Ex. Ammonium Sulphate- – NH41+ SO/ ‘ (NH4)2 SO4

    EXAMPLES

    1. Mole Concept \

    The mole (mol) is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of 12C

    The Avogadro constant is named after the early nineteenth century Italian scientist Amedeo Avogadro.

    S.No.

    Symbol / formula of atom / molecule

    Atomic / molecular mass ( u)

    lmole ( in g)

    Avogadro no.

    Molar mass ( g mol -1)

    1.

    O

    16 u

    16 g

    6.022 x 1023 atoms

    16 g mol -1

    2.

    Nz

    28 u

    28 g

    6.022 x 1023 molecules

    28 g mol -1

    3.

    HCl

    36.5 u

    36.5 g

    6.022 x 1023 molecules

    36.5 g mol -1

    GRAM MOLECULAR MASS

    Gram molecular mass is the mass in grams of one mole of a molecular substance.

    Ex: The molecular mass of N2 is 28, so the gram molecular mass of N2 is 28 g.

    ATOMIC MASS UNIT

    An atomic mass unit or amu is one twelfth of the mass of an unbound atom of carbon-12. It is a unit of mass used to express atomic masses and molecular masses.

    Also Known As: Unified Atomic Mass Unit (u).

    MOLECULAR MASS : A number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom, which is taken to have a mass of 12.

    Examples: The molecular mass of C2H6 is approximately 30 or [(2 x 12) + (6 x 1)]. Therefore the molecule is about 2.5 times as heavy as the 12C atom or about the same mass as the NO atom with a molecular mass of 30 or (14+16).

    Q.1 What term is used to represent the mass of 1 mole molecules of a substance? Q.2 What is the gram atomic mass of i) Hydrogen ii) oxygen ?

    Q.3 Calculate molar mass of C2H2.

    1. Molar Mass & Avogadro Constant |

    Ex: i) Convert 35 g of Al into mol.

    A: Molar mass of Al= 27 g

    27 g = 1mol

    1mol

    = 35 g x

    27 g

    = 1.3 mol of Al

    ii) How many grams of SiO2 are present in 0.8 mol ?

    A: Molar mass of SiO2 = 60.1 g

    1 mol = 60.1 g

    60.1g of SiO2

    = 0.8 mol of SiO2 x

    1mol of SiO2

    = 48.1 g SiO2

    Q.1 Calculate the mass of one atom of sodium?

    Q.2 The atomic mass of calcium is 40 u. What will be the number of calcium atoms in 0.4 u of calcium?

    Q.3 How many atoms of oxygen are present in 120 g of nitric acid ?

    1. Mark Questions:
    2. Who gave law of conservation of mass ?
    3. What term is used to represent the mass of 1 mole molecules of a substance?
    4. What name is given to the number 6.023 x 10 23 ?
    5. What is molecular mass?
    6. Give Latin names for sodium & mercury.
    7. *How many atoms are there in exactly 12 g of carbon ?
    8. Define mole.
    9. Calculate formula unit mass of CaCl2. [ At. Mass : Ca = 40 u , Cl = 35.5 u ]
    10. Name a diatomic gas.
    11. How many atoms are present in H2SO4.
    12. Marks Questions:
    13. Give the chemical symbols for the following elements: Gold, Copper , Potassium & Iron.
    14. *What do the following symbols represent – i) 1 H & i) H2
    15. Neon gas consists if single atoms , what mass of neon contain 6.022 x 1023 atoms.
    16. What elements do the following compounds contain ? i) Water ii) Lead nitrate
    17. State the differences between an atom or a molecule.
    18. Molar Mass of water is 18 g mol-1 , what is the mass of 1 mole of water? .
    19. *The number of atoms in 1 mole of hydrogen is twice the number of atoms in one mole of helium. Why?
    20. Write the chemical formulas for the following:

    i) Silver oxide ii) Iron (III) sulphate

    1. Calculate molar mass of H2O2 & HNO3.
    2. What is the mass of 0.2 moles of oxygen molecules?
    3. Marks Questions:
    4. State the main postulates of John Dalton’s atomic theory.
    5. What are polyatomic ions ? Give two examples.
    6. State the following
    7. Law of conservation of mass. ii) Law of constant proportion
    8. What is the mass of :
    9. 1 mol of N atoms. ii) 4 mol of Al atoms.
    10. What is meant by the term atomicity ? State the atomicity of i) Phosphorous
    11. Sulphur

    5 Marks Questions:

    1. i) What is molecular formula ? State with example what information can be derived from a molecular formula .
    2. Write the names of the compounds represented by the following formulas: a) Mg(NO3)2 b) K2SO4 c )Ca3N2
    3. * i) What is gram molecular mass?
    4. Write the formulas & names of the compounds formed between :

    a) Ferrous and sulphide ions b) Aluminium and sulphate ions

    1. Potassium and chlorate ions d) Barium and chloride ions
    2. i) Calculate the number of moles for the following:

    a) 52 g of He b) 17 g of H2O

    1. How many molecules are present in 34 g of ammonia ?
    2. Calculate the mass of 0.5 mole of sugar (C12H22O11).

    You Are expected to know..

    • Laws of Chemical combination.
    • John Dalton’s imagination about atom & the limitation of his theory.
    • Difference between an atom & molecule.
    • Types of ions
    • Writing chemical formula of compounds.
    • Relationship between Mole , Molar Mass & Avogadro Constant

  • Is Matter Around Us Pure Notes Class 9th Science Chapter 2

    CHAPTER – 2 “Is Matter Around Us Pure”

    CONCEPT DETAIL

    KEY CONCEPTS : [ *rating as per the significance of concept ]

    1. Pure Substance & Mixture

    ***

    2. Types of Mixtures

    ****

    3. Methods of Separation of Mixtures

    ******

    4. Concentration & Types of Solutions

    *****

    5. Physical & Chemical Changes

    ***

    6. Alloys

    **

    -I- Pre requisites

    • Basic knowledge of particle nature of matter
    • Different states of matter

    SURVEY ANALYSIS

    Conceptual levels of comprehension on the basis of feedback taken from the students

    120%

    PURE SUBSTANCE

    MIXTURE

    • Pure substance consists of a single type of substance .

    • Mixture consists of two or more pure substances.

    • Pure substance cannot be

    separated into other substances by physical methods.

    • Mixture can be separated into its components by physical methods.

    • Pure substance has its own definite properties.

    • Mixture shows the

    properties of its components.

    Elements are made up of one kind of atoms only. Compounds are made up of one kind of

    1. Pure Substance & mixture |

    molecules only.

    Difference between Compound &Mixture [ refer NCERT text Book Tab.2.2, page 26]

    Q.1 Is air around us a compound or mixture?

    Q.2 Water is a compound. Justify.

    Q.3 Classify the following as element, compound and mixture: Iron, sea water, Milk Q.4 Are the naturally occurring material in nature chemically pure substances?

    ^TypesofMixtures^J

    Mixtures can also be grouped

    1. on the basis of their physical states:
     

    SOLID

    LIQUID

    GAS

    SOLID

    • Salt and sugar

    • Salt and water

    • Dust in air

    LIQUID

    • Mercury and copper

    • Alcohol and water

    • Clouds

    GAS

    • Hydrogen and palladium

    • Oxygen and water

    • Air

    ii) on the basis of miscibility:

    Homogeneous Mixture

    Heterogeneous Mixture
    • It consists of single phase.
    • Uniform composition.
    • Example: Sugar dissolved in water
    • It consists of two or more phase.
    • Does not have uniform composition.
    • Example: Air, sand and common salt.

    Q.1 Give one example for each of the following mixtures: i) Solid/solid (homogeneous)

    1. Solid/solid (heterogeneous) iii) Liquid/liquid (homogeneous) iv) Liquid/liquid (heterogeneous) v) Gas/liquid (homogeneous)..

    Q.2 Classify the following as homogeneous & heterogeneous mixture:

    1. sodium chloride & water ii) glucose & water iii) sand & water iv) air
    2. Separating the components of a mixture |

    The components of a heterogeneous mixture can be separated by

    • simple methods like –

    hand picking, sieving, & Winnowing

    • special techniques like –
    1. Evaporation : a mixture of salt and water or sugar and water.
    2. Centrifugation : Butter from curd, Fine mud particles suspended in water.
    3. Decantation (Using separating funnel) : Oil from water.
    4. Sublimation : Camphor from salt,
    5. Chromatography : Different pigments from an extract of flower petals.
    6. Distillation and fractional distillation : Separating components of Petroleum viii) Magnetic separation: Iron pins from sand.

    Q.1 Name the process you would use to :

    1. recover sugar from an aqueous sugar solution.
    2. separate mixture of salt solution and sand.

    Q.2 How will you separate a mixture of sand, water and mustard oil ?

    1. Concentration of Solution |

    The amount of solute present in a given amount (mass or volume) of solution.

    Amount of solute Amount of solute

    Concentration of a solution = OR

    Amount of solvent Amount of solution

    The concentration of a solution can be expressed as mass by mass percentage or as mass by volume percentage.

    Mass of solute

    Mass by mass percentage of a solution = x 100

    Mass of solution Mass of solute

    Mass by volume percentage of a solution = x 100

    Volume of solution

    lypefii^

    a) on the basis of size of solute particles:

    True solution

    Sol [ Colloid]

    Suspension

    • Homogeneous

    • Heterogeneous

    • Heterogeneous

    • Size of solute

    particles is less than

    q

    1 n m or 10 m .

    • Size of solute particles is between 1 nm to 1000 nm.

    • Size of solute particles is more than 1000 nm.

    • Particles cannot pass through filter paper.

    • Particles can pass through filter paper.

    • Particles cannot pass thorough filter paper.

    • Stable

    • Stable and settle only on centrifugation.

    • Unstable and settle down on its own.

    • Solution of sodium chloride in water, sugar & water.

    • Milk , Fog
    • muddy water, chalk & water,
    • smoke in the air.

    [ types of colloids : refer NCERT Text Book table 2.1, page 18 ]

    Colloidal solution is a heterogeneous mixture. It consists of two phases:-

    1. Dispersed phase : component present in small proportion
    2. Dispersion medium : component present in large proportion

    The particles of colloid are large enough to scatter a beam of light passing through it and make its path visible. Thus, they show Tyndall effect.

    The colloidal particles are moving at random in a zigzag motion in all directions.

    This type of zig-zag motion of colloidal particles is called Brownian movement.

    b) on the basis of amount of solute:

    Unsaturated solution

    Saturated Solution

    Supersaturated solution

    A solution which has lesser amount of solute that it can dissolve at a given temperature is known as unsaturated solution.

    A solution which has maximum amount of solute that it can dissolve at a given temperature is known as saturated solution.

    A solution which can dissolve amount of solute by increasing temperature saturated solution is known as supersaturated solution.

    c) on the basis of nature of solvent

    Aqueous solution

    Non-Aqueous solution

    The solution in which the solvent is water is known as aqueous solution.

    The solution in which the solvent is other than water (ether, alcohol or aceton) known as non-aqueous solution.

    Q.1 Classify the following substances into true solutions and colloidal solutions.

    Milk , ink , starch dissolved in water.

    Q.2 A solution has been prepared by dissolving 5g of urea in 95 g of water. What is the mass percent of urea in the solution?

    Q.3 Give an example of an aqueous solution in which gas is dissolved.

    1. Physical & Chemical Changes I

    Physical changes – Changes that do not result in the production of a new substance.

    • If you melt a block of ice, you still have H2O at the end of the change.
    • If you break a bottle, you still have glass.

    Examples : melting, freezing, condensing, breaking, crushing, cutting, and bending.

    Chemical changes – Changes that result in the production of another substance.

    • As in the case of autumn leaves, a change in color is a clue to indicate a chemical change.
    • a half eaten apple that turns brown.

    Q.1 Which of the following is an example of physical change?

    1. Mixing baking soda and vinegar together, and this causes bubbles and foam.
    2. A glass cup falls from the counter and shatters on the ground.
    3. Lighting a piece of paper on fire and the paper burns up and leaves ashes.
    4. Baking a birthday cake for your mother.

    Q.2. Which of the following is an example of chemical change?

    1. Filling up a balloon with hot air.
    2. Taking a glass of water and freezing it by placing it in the freezer.
    3. A plant collecting sunlight and turning it into food.
    4. Your dog ripping up your homework.
    5. Which change can be easily be reversed?
    6. Chemical Change
    7. Physical Change
    8. Both a physical and chemical change
    9. Neither a physical or chemical change

    |^.ANoysJ

    A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal .

    • These cannot be separated into their components by physical methods.
    • However, these are considered as mixture because these show the properties of its constituents and can have variable composition.

    The benefit of alloys is that you can combine metals that have varying characteristics to create an end product that is stronger, more flexible, or otherwise desirable to manufacturers.

    • Aluminium alloys are extensively used in the production of automotive engine parts.
    • Copper alloys have excellent electrical and thermal performance, good corrosion resistance, high ductility and relatively low cost.
    • Stainless steel alloys are used for many commercial applications such as watch straps, cutlery etc.
    • Titanium alloys have high strength, toughness and stiffness & are used in aerospace structures .

    Q,1 Why should we use alloys instead of pure metals? Q.2 State uses of Aluminium & Stainless steel alloys.

    ILQUESTIONJANKJ^HOTSJJ

    1. Mark Questions:
    2. What is meant by pure substance?
    3. What is meant by mass percentage of solution?
    4. Name the process of separation of miscible liquids.
    5. Arrange the following in decreasing order of size of the particles.

    True Solution , Suspension , Colloid.

    1. *Give an example of an aqueous solution in which gas is dissolved.
    2. Name the dispersion medium and dispersed phase in the white material inside an egg.
    3. What happens when hot saturated solution is cooled?
    4. How would you separate a mixture of chalk and water?
    5. *How much water should be added to 15 grams of salt to obtain 15 % salt solution?
    6. What type of mixtures are separated by technique of crystallization ?
    7. Marks Questions:
    8. Which of the following materials fall in the category of a pure substance?

    a) Ice b) Milk c) Iron d) Hydrochloric acid

    e) Calcium oxide f) Mercury g) Brick h) Wood.

    1. What do you understand by saturated solution and unsaturated solution?
    2. *What do you observe when sunlight passes through a dense forest?
    3. List two points of differences between homogeneous and heterogeneous mixtures.
    4. State the difference between aqueous & non aqueous solution .
    5. Which of the following will show “Tyndal Effect” & Why ?

    a) Salt Solution b) Milk c) Copper Sulphate Solution d) Starch Solution

    1. *How can we obtain pure copper sulphate from an impure sample?
    2. Give two differences between compounds and mixtures.
    3. Why is hydrogen considered as element ? Give two reasons.
    4. Why water is a compound and not a mixture?
    5. Marks Questions:
    6. Classify the following into elements, compounds and mixtures:

    a) Sodium b) Soil c) Sugar solution d) Silver e) Calcium carbonate f) Tin g) Silicon h) Coal i) Air j) Soap k) Methane l) Carbon dioxide m) Blood.

    1. Give any two applications of centrifugation.
    2. Which of the following is chemical change?

    a) Growth of a plant b) Rusting of iron c) Mixing of iron fillings and sand d) Cooking of food e) Digestion of food f) Freezing of water g) Burning of a candle.

    1. *State the difference between simple distillation & fractional distillation.
    2. * A solution contains 40 ml of ethanol mixed with 100 ml of water. Calculate the concentration in terms of volume by volume percentage of the solution.

    5 Marks Questions:

    1. *What is meant by Tyndall effect? What is its cause? Illustrate with example.
    2. How would you separate the mixture containing sulphur and sand ?
    3. What is crystallization? Give its two applications.
    4. How are sol, solution and suspension different from each other?
    5. How do we obtain coloured components, i.e. dye from Blue/Black ink ?

    |^ou^re^xpected^o^now^J

    • Types of mixtures.
    • Method of Separation of mixtures.
    • Types of solutions.
    • Concentration terms of solution.
    • Physical and Chemical Change.
    • Significance of alloys.

  • Matter in Our Surroundings Notes Class 9th Science Chapter 1

    CHAPTER – 1 “Matter in our Surroundings”

    conceptdetails

    KEY CONCEPTS : [ *rating as per the significance of concept]

    1. Particle nature of Matter

    ***

    2. States of Matter

    ****

    3. Interchange in states of Matter

    *****

    4. Evaporation & Boiling

    ****

    5. Kelvin , Celsius scale

    ***

    -I- Pre requisites

    • Definition of matter.
    • Elementary idea of three physical states of matter.

    SURVEY ANALYSIS

    Conceptual levels of comprehension on the basis of feedback taken from the students

    1. Particle Nature of Matter j

    [ refer NCERT text book activities 1.1 to 1.8 1

    • Anything that occupies space and has mass and is felt by senses is called matter.
    • Matter is the form of five basic elements the Panch tatva – air , earth fire , sky and water.
    • Characteristics of particles of matter
    • Made of tiny particles.
    • Vacant spaces exist in particles.
    • Particles are in continuous motion.
    • Particles are held together by forces of attraction.

    Q.1 Define matter.

    Q.2 What happens if you put copper sulphate crystals in water?

    [ refer NCERT text book activities 1.9 to 1.111

    Basis of Classification of Types

    • Based upon particle arrangement
    • Based upon energy of particles
    • Based upon distance between particles
    • Five states of matter
    • Fixed shape and definite volume .
    • Not fixed shape but fixed volume.
    • Neither fixed shape nor fixed volume.
    • Inter particle distances are smallest.
    • Inter particle distances are larger.
    • Inter particle distances are largest.

    Almost incompressible.

    Incompressible.

    Highly compressible.

    • High density and do not diffuse.
    • Inter particle forces of attraction are strongest.
    • Constituent particles are very closely packed.
    • Density is lower than solids and diffuse.
    • Inter particle forces of attraction are weaker than solids .
    • Constituent particles are less closely packed.
    • Density is least and diffuse.
    • Inter particle forces of attraction are weakest.
    • Constituent particles are free to move about.
    1. Plasma (non -evaluative)

    A plasma is an ionized gas.

    A plasma is a very good conductor of electricity and is affected by magnetic fields.

    Plasma, like gases have an indefinite shape and an indefinite volume. Ex. Ionized gas

    1. Bose-Einstein condensate (non -evaluative)
    • A BEC is a state of matter that can arise at very low temperatures.
    • The scientists who worked with the Bose-Einstein condensate received a Nobel Prize for their work in 1995.
    • The BEC is all about molecules that are really close to each other (even closer than atoms in a solid).

    Microscopic Explanation for Properties of Solids

    Solids have a definite shape and a definite volume because the particles are locked into place

    Solids do not flow easily because the particles cannot move/slide

    past one another past one another

    Solids are not easily compressible because there is little free space between particles

    Microscopic Explanation for Properties of Liauids

    Liquids are not easily compressible and have a definite volume because there is little free space between particles.

    Liquids have an indefinite shape because the particles can lide

    past one another. past one another.

    Liquids flow easily because the particles can move/slide past one another.

    Microscopic Explanation for Properties of Gases

    Gases are easily compressible because there is a great deal of free space between particles

    Gases have an indefinite shape and an indefinite volume because the particles can move past one another.

    Gases flow very easily because the particles randomly move past one another.

    (non -evaluative)^

    Microscopic Explanation for Properties of Plasmas

    Plasmas have an indefinite shape and an indefinite volume because the particles can move past one another.

    Plasmas are easily compressible because there is a great deal of free space between particles.

    Plasmas are good conductors of electricity &are affected by magnetic fields because they are composed of ions

    Microscopic Explanation for Properties of BEC

    Particles are less energetic than solids because Exist at very low temperature .

    Particles are literally indistinguishable because they are locked into same space .

    BEC shows superfluidity because Particles can flow without friction.

    Q.1 A substance has a definite volume but no definite shape ? State whether this substance is a solid, a liquid or a gas.

    Q.2 Arrange the following substances in increasing order of force of attraction between the particles. (a) Milk (b) Salt (c) Oxygen.

    Q.3 A substance has neither a fixed shape nor a fixed volume . State whether it is a solid, a liquid or a gas.

    Q.4 The melting point of a substance is below the room temperature . Predict its physical state.

    3.Interchange in states of matter

    [ refer NCERT text book activities 1.12 to 1.14 1 Matter Can Change its State

    Water can exist in three states of matter –

    • Solid, as ice ,
    • Liquid, as the familiar water, and
    • Gas, as water vapour.

    Sublimation : The changing of solid directly into vapours on heating & vapours into solid on cooling. Ex. Ammonium chloride , camphor & iodine.

    1. Effect of change in temperature

    The temperature effect on heating a solid varies depending on the nature of the solid & the conditions required in bringing the change .

    • On increasing the temperature of solids, the kinetic energy of the particles increases which overcomes the forces of attraction between the particles thereby solid melts and is converted to a liquid.
    • The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
    • The melting point of ice is 273.16 K.
    • The process of melting, that is, change of solid state into liquid state is also known as fusion.
    1. Effect of Change of Pressure
    • Increasing or decreasing the pressure can change the state of matter. Applying pressure and reducing temperature can liquefy gases.
    • Solid carbon dioxide (CO2) is stored under high pressure. Solid CO2 gets converted directly to gaseous state on decrease of pressure to 1 atmosphere without coming into liquid state. This is the reason that solid carbon dioxide is also known as dry ice. Latent Heat :

    The hidden heat which breaks the force of attraction between the molecules during

    change of state.

    Fusion

    Vaporisation

    Heat energy required to change 1kg of solid into liquid.

    Heat energy required to change 1kg of liquid to gas at atmospheric pressure at its boiling point.

    Thus, we can say that pressure and temperature determine the state of a substance, whether it will be solid, liquid or gas.

    [ refer fig. 1.9 NCERT Text Book, page-8 ]

    Q.1

    What is vapour ?

    Q.2 Name the temperature at which the solid and liquid states of substance can exist

    together .

    Q.3

    What is the effect of pressure on boiling point?

    Q.4

    Name any two substances which sublime.

    Q.5

    Define Condensation.

    Q.6 For any substance, why does the temperature remain constant during the

    change of state?

    4. Evaporation & Boiling |

    • Particles of matter are always moving and are never at rest.
    • At a given temperature in any gas, liquid or solid, there are particles with different

    amounts of kinetic energy.

    • In the case of liquids, a small fraction of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction of other particles and gets converted into vapour .
    • This phenomenon of change of a liquid into vapours at any temperature below its boiling point is called evaporation.
    • Factors Affecting Evaporation
    • The rate of evaporation increases with an increase of surface area.
    • With the increase of temperature, more number of particles get enough kinetic energy

    to go into the vapour state.

    • Humidity is the amount of water vapour present in air. The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount of water in air is already high, the rate of evaporation decreases.
    • Wind speed : the higher the wind speed , the more evaporation.

    Evaporation cause cooling.

    The particles of liquid absorb energy from the surrounding to regain the energy lost during evaporation,

    Evaporation Vs Boiling

    • Boiling is a bulk phenomenon. Particles from the bulk (whole) of the liquid change into vapour state.
    • Evaporation is a surface phenomenon. Particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state.

    Q.1 Which is the slow process, Evaporation or Boiling ?

    Q.2 State the effect of surface area on rate of evaporation.

    Q.3 Why are we able to sip hot tea faster from saucer rather than from a cup?

    5. kelvin & Celsius Scale

    • Kelvin is the SI unit of temperature, 00 C =273.16 K. we take 00 C = 273 K.
    • SI unit of temperature is Kelvin. T (K)= T (oC) +273
    • Kelvin scale of temperature has always positive sign , hence regarded as better scale than Celsius.
    • Atmosphere (atm) is a unit of measuring pressure exerted by a gas. The SI unit of pressure is Pascal (Pa):
    • 1 atmosphere = 1.01 x (10 to the power 5) Pa. The pressure of air in atmosphere is called

    atmospheric pressure. The atmospheric pressure at sea level is 1 atmosphere, and is

    taken as the normal atmospheric pressure.

    Q.1 What is the SI unit of temperature?

    Q.2 Kelvin scale of temperature is regarded as better scale than Celsius. Why?

    Q.3 Convert 10oC into Kelvin scale.

    QUESTIONANK HOTS

    1. Mark Questions:
    2. Pressure on the surface of a gas is increased. What will happen to the inter particle forces?
    3. Name the three states of matter.
    4. What happens when a liquid is heated ?
    5. A gas can exert pressure on the walls of the container. Assign reason.
    6. Convert the following temperature to Kelvin Scale (a) 100°C (b) 37°C
    7. What is meant by density?
    8. Give the characteristics of the particles of matter.
    9. Water droplets seen on the outer surface of a glass containing ice-cold water is due

    to .

    1. Change of gaseous state directly to solid state without going through liquid sate is

    called .

    1. . is a surface phenomenon.
    2. Marks Questions:
    3. Define Latent heat of vaporisation.
    4. Explain why temperature remain constant during the change of state of any substance?
    5. Define Sublimation with examples.
    6. *Do we sweat more on a dry day or humid day ? Justify your reason.
    7. Why do we see water droplets on the outer surface of a glass containing ice cold water?
    8. Convert the following temperature to the Kelvin scale (a) 25°C (b) 373°C
    9. List two properties that liquids have in common with solids.
    10. List two properties that liquids have in common with gases.
    11. *What will happen to the melting point temperature of ice if some common salt is added to it? Justify your answer.
    12. *How will you show that air has maximum compressibility?
    13. Marks Questions:
    14. Define the term (a) Latent heat of fusion (b) Latent heat of vaporization
    15. *State the effect of (i) surface area (ii) nature of the liquid on the rate of evaporation.
    16. *Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Why?
    17. What is the physical state of water at 250°C, 100°C, 0°C?
    18. Give reasons :
    19. A sponge can be pressed easily; still it is called a solid.
    20. Water vapours have more energy than water at same temperature.

    6 . What are intermolecular forces ? How are these related to the three states of matter ?

    1. Is it possible to liquify atmospheric gases? If yes, suggest a method.

    5 marks Questions:

    1. a) What is meant by evaporation? What are the factors on which the rate of evaporation depend upon?

    1. How does evaporation causes cooling?
    2. State the properties of all the five states of matter.
    3. Define : Melting point , Freezing point & Boiling point

    You are expected to know

    • Particle nature of matter.
    • All five states of matter & their behaviour
    • Inter conversion of states of matter
    • Latent heat
    • Conversion between Kelvin scale & Celsius scale

  • Class 9th Science Notes | NCERT Based Short & long Notes

    Get Best NCERT Notes Of Science Class 9th online & Free PDF Download.

  • Chapter 6 Population Notes Class 9th Social Science Geography

    MAJOR QUESTIONS ABOUT THE POPULATION OF A COUNTRY.

    (a) Population size and distribution- How many people are there and where are they located?

    • Population growth and change. How has the population grown and changed over time?
    • Characteristics of the population- What are their age, sex, literacy levels, occupation structure and health condition.

    Population size and distribution

    • According to the census of 2001, India has the population of 1028 million (102 crores 8 lakh)
    • They are unevenly distributed over the vast area of 3.28 million sq. km.
    • The most populous state with 166 million people in U.P.
    • A least populous state is Sikkim with 0.5 million and Lakshadweep has only 60,000 population.
    • About half of India’s population lives just in 5 states. They are Uttar Pradesh, Maharashtra, Bihar, West Bengal and Andra Pradesh.

    Density of Population

    • The number of person per unit area [1 sq. km]
    • According to 2001 census, the average calamity of the population is 324 person/ sq. km. The highest density of population is in West Bengal with 904/ sq. km. Least density of population is in Arunachal Pradesh with 13/ Sq. km.

    Reason for differences in density of population.

    • Rugged terrain and unfavorable climatic conditions are responsible for the sparse population in the states like Jammu and Kashmir and Rajasthan etc.
    • Assam and most of the peninsular state have moderate population density, due to hilly, rocky nature, low rainfall and less fertile soil.
    • Northern Plains and Kerala have a high density of population due to flat plains with fertile soil and abundant rainfall.

    Population Growth

    It refers to the change in the number of inhabitants of a country during a specific period of time. It can be expressed in two ways:-

    1. Absolute number- It can be obtained by subtracting the earlier population from the latest population.
    2. Percentage change- It is studied that in percent per annum.

    Processes of population change

    There are 3 processes of population change

    1. Birth rate- The numbers of live births per 1000 persons in a year.
    2. Death rate- The number of deaths per 1000 persons in a year.
    3. Migration- The movement of the people across regions be territories. Migration is of two types.
    • Internal  Migration- The movement of the people within the country.
    • International Migration- The movement of the people b/w the countries.
    ‘Push’ and ‘Pull’ factors of Migration

    Push Factors- Most of the migrations are from rural to urban areas due to poverty and unemployed in rural areas.

    Pull Factor- Increase employment opportunities and better living conditions in urban areas.

    Age Composition

    It refers to the number of people in different age group.

    The population is grouped into 3 categories.

    1. Children (below 15 years)- They are economically unproductive and need to be provided with food, shelter, clothing etc.
    2. Working age (15-59 years)- They are economically productive and biologically reproductive.
    3. Aged (above 59 years)- They can be economically productive through retired.

    Sex Ratio

    • It refers to the numbers of females per 1000 males in the population.
    • The sex ratio has always been unfavorable for females in India.

    Literate

    A person aged 7 years and above who can read and write with understanding in any language.

    Occupational Structure

    The distribution of the population according to different types of occupation-

    Occupation is classified as primary secondary and tertiary.

    (a) Primary occupation includes agriculture, animal husbandry, fishing etc.

    (b) Secondary occupation includes manufacturing industry building and construction work.

    (c) Tertiary occupation includes transport, trade communications, banking etc.

    National Population Policy (NPP) 2000

    In 2000, government of India invited National Population Policy.

    Features

    • Imparting free and compulsory education up to 14 years of age.
    • Reducing infant mortality rate.
    • Achieving universal immunization of children.
    • Promoting delayed marriage for girls.
    • Creating awareness among the adolescents about sexually transmitted diseases (STD), need of food supplements etc.

  • Chapter 5 Nature Vegetation & Wildlife Notes Class 9th Social Science Geography

    • 47000- plants species are found in India. India stands the 10th place in the world and 4th in Asia.
    • 15000 species of flowering plants.
    • India has many non-flowering plants like firm, fungi etc.
    • 90000 species of animals.
    • A variety of fish are also found in water.

    Natural Vegetation

    • It refers to a plant community which has grown naturally without human aid and has been left undisturbed by a human for a long time, also known as a virgin vegetation.

    So, cultivated crop, fruits and orchards do not come under Natural Vegetation.

    Endemic species- Purely Indian

    Exotic Species – Come outside from India.

    Flora- refers to plant life.

    Fauna – refers to animal life.

    Factors that help in the growth of flora and fauna.

    • Relief Factors

    Land – Land affects the natural vegetation directly and indirectly. The nature of the land influences the types of vegetation.

    Soil – Different types of soils provide the basis for different types of vegetation.

    • Climatic factors

    Temperature – The fall in the temperature affects the types of vegetation and its growth.

    Photoperiod (Sunlight) – Due to longer duration of sunlight, trees grows faster in Summer.

    Precipitation – Areas of heavy rainfall have a dense forest in comparison with low rainfall.

     Importance of Forest

    • Forests are renewable resources and enhance the quality of the environment.
    • They modify local climate, control soil erosion and regulate stream flow.
    • They support a variety of industries, provide a livelihood for many communities.
    • It controls wind force and temperature and causes rainfall.
    • It provides humus to the soil and shelter to wildlife.

    The factors that cause the decline of forests

    • The growing demand for cultivated land.
    • Development of industries.
    • Mining
    • Urbanisation
    • Gazing of pastures.

    Eco-System

    • All the plants and animals in an area are interrelated and interdependent to each other in their physical environment.
    • Humans are also the part of eco-system.

    Types of Vegetation

    • Tropical Evergreen Forests (heavy rainfall areas)
    • Tropical Deciduous Forests (Rainfall b/w 200-70)
    • Tropical thorn forests and shrubs (less than 70 cm)
    • Montane Forests (Higher and decrease temperature areas)
    • Mangrove Forests (Coastal Reign)

    Tropical Evergreen Forests

    • These forests are found in the heavy rainfall areas, E.G. Western Ghats, Assam etc.
    • The trees are very tall up to 60 m height.
    • All kinds of vegetation i.c. tress, shrubs, and creepers are grown here giving multi layered structures.
    • There is no definite time for the trees to shed their leaves. So these forests appear green through out the year.
    • E Body, Mahogany, rosewood etc. are the important trees are found.
    • Elephant, Monkeys, Lemur etc. are the important animals.

    Tropical Deciduous Forests

    • These are the widespread forests in India.
    • They are found in the areas receiving rainfall between 200-700 cm.
    • Trees shed their leaves during the dry season.
    • On the basis of the availability of water. These are divided into moist and dry deciduous forests.

    Moist Deciduous Forests

    • They are found in the areas receiving rainfall between 200-100 cm. Eg- Jharkhand, west Orissa.
    • Teak bamboo sake etc. are the important trees.

    Dry Deciduous Forests

    • They are found in the areas receiving rainfall b/w 100-70 cm eg- Bihar and U.P.
    • Teak, Sal, Peepel etc. the important trees.

    The Thorn Forests and Shrubs

    • These are the forest found in the areas receives less than 70 cm rainfall. Eg- Parts of Gujarat, Rajasthan.
    • Acacias, palms cacti etc are the important plan species.
    • Trees are scattered and have long roots to get moisture.
    • The stems are succulent (sponge) to conserve water.
    • The leaves are thick and small to minimize evaporation.
    • Rat, mice, rabbits and camels etc are the important animals.

    Montane Forests

    In mountainous areas, the decrease in temperature affects the growth of vegetation.

    • Wet Temperate Forests- They are found between a height of 1000 and 2000 m eg. Oaks, chestnut.
    • Temperate Forests- They are found at the height of 1500-3000 m eg. pine, silver fir
    • Temperate Grasslands-  They are found in the higher elevation (height).
    • Alpine Vegetation- Found at the height of more than 3600 m. eg. Jumpers, pine.
    • The trees get (stunted) at the snow line.
    • Alpine grasslands are used by nomadic tribes like Gujjars and Bakarwals.
    • Tundra Vegetation- Lichens mosses are found at the higher altitude.

    Mangrove Forests

    • They are found in the coastal areas influenced by tides(winds).
    • roots of the plant are submerged under water.
    • Sundari trees are found in the Ganga-Brahmaputra delta, which provides durable hard timber.
    • Palm, coconut etc are the important trees.
    • Royal Bengal tiger, turtles crocodiles are animals.

    Wild Life

    • India is rich in wildlife.
    • There are 90000 animal species, 2000 species of birds and 2546 species of fish.
    • India also shares b/w 5 and 8 percent of worlds, amphibians, reptiles, and mammals.
    • Elephants are found in the forests of Assam, Karnataka etc.
    • One horned rhinoceros, Indian Bison, Nilgri etc are important animals.
    • India is the only country that has both tigers and lions.
    • Lions-Gir forests in Gujarat.
    • In the rivers and lakes turtles, crocodiles and gharials are found.
    • Peacocks, ducks, cranes, pigeons etc are the colorful birds.

    Importance of conservation of Wildlife

    • The animals provide us drought power, transportation, meats, and eggs.
    • The fish provide nutritive food.
    • Insects help in pollination of crops.
    • Every species has a role to play in the ecosystem.

    How are human beings responsible for balancing the ecosystem?

    • Hunting by greedy hunters.
    • Pollution due to chemical and industrial waste.
    • Acid deposits.
    • Reckless cutting of the forests.

    What are the steps taken by the Government to protect flora and fauna?

    • 14 biosphere reserves have been set up
    • Financial and technical assistance is provided too many botanical gardens since 1992.
    • Project Tiger, project Rhino etc have been introduced.
    • 89 National parks, 490 wildlife sanctuaries, and zoological gardens are set up.

  • Chapter 4 Climate Notes Class 9th Social Science Geography

    Climate

    It is a sum total of weather conditions and variations over a large are for a long period of time (more than 30 years)

    Weather 

    It is the state of the atmosphere over an area at any point in time.

    Elements of Weather and Climate

    The temperature, atmosphere, pressure, wind, humidity, and precipitation. (rainfall)

    India has monsoon type climate.

    Q. Temperature and precipitation vary from place to place and season to season why?

    • In Summer, the temperature reaches 50°C in some parts of Rajasthan while it is 20°C in Jammu and Kashmir.
    • On a winter night, the temperature in Jammu and Kashmir is minus 45°C whereas it is 22°C in thiruwanthpuram.
    • The annual precipitation in Meghalaya is more than 400 cm while it is less than 10 cm in parts of Rajasthan and Jammu and Kashmir.
    • Most of the parts of the country receive rainfall from June to September whereas Tamilnadu receives rainfall during October and November.
    • Coastal areas do nor experience much variations in climate conditions.

    Climate controls of any place

    There are six major controls of the climate of any place.

    They are latitude, altitude, pressure and wind system, distance from the sea, ocean currents be relief features.

    1. Latitude– Due to the curvature(curve) of the earth, solar energy received varies according to the latitude.
    2. Altitude– Temperature decreases with higher altitude (height)
    3. Wind System and Pressure- They affect the climate of any place.
    4. Distance from the sea – The places wear the sea have a moderate climate and the places away from the sea have extreme climate (continentality)
    5. Ocean Currents – The onshore winds affect the climate of coastal areas.
    6. Relief Features – High mountains act as barriers for cold or hot winds.

    Factors affecting India’s Climate

    1. Latitude – The tropic of cancer passes through the middle of the country. So, in the south of tropic of cancer we have a tropical climate and in the north of Tropic of cancer have a sub-tropical climate.
    2. Altitude – The Himalayas prevent the cold winds from central Asia from entering India, So we have milder winter.

    Pressure and Wind System

    The weather and climate are influenced by the following at atmospheric conditions. They are

    1. Pressure and winds
    2. Upper air circulation
    3. Cyclons

    The air always moves from high pressure are the too low-pressure area.

    In winter, a high pressure is formed north of Himalayas and so, the cold and dry winds blow towards the south.

    Jet System

    • These are the high altitude winds in the atmosphere. Their speed varies from 110 km/hr in summer and 184 km/hr in winter.
    • They have located over 27°-30° North Latitude (Westly) Jetstream
    • Easterly Jetstream blows over India over 14°N Latitude.

    The Mechanism of Monsoon in India

    • The differential heating and coding of land and water. The seas experience high pressure and the land experiences low pressure.
    • In summer, equatorial through is positioned over Ganga a plain.
    • The presence of high pressure is last of Madagascar.
    • The Tibetan plateau gets intensely heated during summer which results in strong vertical air current movement of air.
    • The movement of the westerly jet streams and easterly jet streams.

    Southern Oscillation (S.O.)

    Normally the south Pacific Ocean experiences high pressure and the Indian Ocean experience low pressure. But in recent years, there is a reversal in the pressure conditions, i.c. the Indian ocean experience high pressure and pacific ocean experiences low pressure. This periodical change is known as So.

    El Nino

    A warm ocean current flows over the Peruvian coast instead of the cold current, every 2 to 5 years. It is could as EL Nino.

    The Onset of the Monsoon

    • The monsoon in India is pulsating in nature.
    • The duration of the monsoon is between 100-120 days.
    • Monsoon Burst – Around the time of the arrival of monsoon, the normal rainfall increases suddenly and continues for several days.

    The onset of the monsoon in India

    • The monsoon arrives in the southern tip of Indian Peninsular by the first week of June.
    • Then it is branched off. One branch goes to the Bay of Bengal and other branch proceeds to Arabian sea.
    • The Arabian sea branch reaches Mumbai by 10th June and Bay of Bengal branch reaches Assam by this time.
    • The lofty mountain deflects the monsoon towards the west and the Arabian branch also reaches central India.
    • Both branches merge in the north-west and U.P., M.P., and Delhi etc. receive rainfall by June 29th.
    • By mid-July, Himachal Pradesh and the rest of the states receive rainfall.

    The Seasons

    There are 4 seasons identified in India. They are

    1. Cold Weather seasons (Winter)
    2. Hot Weather Seasons (Summer)
    3. Advancing Monsoon (Rainy)
    4. Retreating Monsoon (Transition)

    Cold Weather Seasons (Winter)

    • The cold weather seasons begins from mid-November and stays until February.
    • December and January are the coldest moths.
    • The temperature decreases from south to north.
    • The days are warm and nights are cold. Frost is common in the north.
    • The wind blows from land to see. So far most parts it is the dry season.
    • It is a season of cyclonic disturbances which causes winter rainfall.
    • The winter rainfall locally known as ‘Mahawat’ has great importance for the cultivation of rabi crops.
    • Peninsular India does not have much winter season.

    The Hot Weather Season (Summer)

    • March to May are the not-weather season in India.
    • In March the highest temperature 38°C is recorded in the Deccan plateau.
    • In April the highest temperature 45°C in North-West.
    • In peninsular India, the temperature remains lower due to the influence of Ocean.
    • It experiences rising temperature and falling air pressure.
    • Loo these are the strong, gust hot and dry winds blow during the day in the north.
    • Dust storms are common in north India.
    • It is a season of thunder storms, Violent Winds, and heavy rainfall.
    • In West Bengal, these storms are called ‘Kaal Baisakhi’.
    • Towards the end of the summer, Pre-monsoon showers are common is Kerala and Karnataka known as ‘Mango showers’ which help in the early repinning of Mangoes.

    Advancing Monsoon (The Rainy Season)

    • By early June, the low pressure intensifies in the northern plains which attacks the South-West monsoon winds.
    • The coming of South-West monsoon which brings rainfall in India.
    • Early in the season, Western Ghats receive more than 250 cm rainfall.
    • Mawsynram (Meghalaya) receives the highest rainfall in the world.
    • Rajasthan and parts of Gujarat receive scanty (less) rainfall.
    • An important feature of this season is ‘Monsoon break’.
    • Monsoon Break – Monsoon rains take place only for a few days at a time when there are rainless intervals known as ‘Monsson Break’.
    • Monsoon through determines the distribution of rainfall i.e., the places near the axis of through receives rainfall.
    • The monsoon is known for its uncertainties. It causes a flood in one part and causes drought in the other.
    • Since it is irregular, it disturbs the farming schedule of millions of farmer.

    Retreating Monsoon (Transition)

    • During October-November, South-West monsoon winds become weaker.
    • It is a period of transition from hot rainy season to dry winter.
    • Day temperature is high and nights are cool.
    • The weather becomes oppressive during the day due to high temperature and humidity are known as ‘October heat’.
    • It is the period of cyclones which are very destructive and causes great damage to life and property.

    Distribution of Rainfall

    • Parts of western coast and north-east receives more than 400 cm rainfall annually.
    • Parts of Gujarat, Rajasthan, Haryana, and Punjab receives less than 60 cm rainfall.
    • Leh in Jammu and Kashmir receives the lowest rainfall.
    • Monsoon is variable from year to year. So the areas of heavy rainfall are affected by floods and the areas of low rainfall are affected by droughts.

    Why is monsoon considered a unifying bond?

    • The seasonal alteration of the Wind Systems provides a rhythmic cycle of the season.
    • The Indian landscape, its animal and pant life, its agricultural calendar and the life of the people including their festivities revolve around monsoon.
    • Year after year, people throughout India eagerly await the arrival of the monsoon.
    • The monsoon wind binds the whole country by providing water to set agricultural activities.
    • The river valleys which carry this water unit the country as a single valley unit.

  • Chapter 3 Drainage Notes Class 9th Social Science Geography

    Drainage – The river system is an area.

    Drainage Basin- The area drained by a single river system.

    Water Divide– Any elevated area such as a mountain that separated two drainage Basin

    Drainage system in India

    Indian rivers are divided into two groups:-

    • Himalayan Rivers
    • Peninsular Rivers

    Distinguish between a Himalayan river and Peninsular river.

    Himalayan River

    • Most of the river Himalayan river is perennial because they have water throughout the year.
    • They receive water from rain as well as meeting of snow.
    • The Himalayan river has long courses.
    • They perform crosional activities and carry silt and sand.

    Peninsular River

    • Peninsular River is the seasonal river because their flow is dependent on rainfall.
    • During the dry season, even the large reduce into channels.
    • They have shorter and shallower courses.
    • Most of the peninsula rivers start in the Western Ghats and flow towards Bay of Bengal.

    River System

    A river along with his tributaries.

    Indus River System

    • The river Indus rises in Tibet, near Mansarowar lake.
    • It enters in India in the Ladakh district of Jammu and Kashmir.
    • The tributaries like Beas, Satluj, |Ravi, Chenab and Jhelum join together in the Indus at Mithankot in Pakistan.
    • Indus flows at the length of 2900 km.

    Indus Water Treaty

    This treaty (arguments) was signed between India and Pakistan in 1960. According to this treaty, India can use 20% of its water.

    The Ganga River System

    • The headwaters of Ganga called the ‘Bhagirathi’ is joined by ‘Alaknanda’ at devoprayag in Uttarakhand.
    • The tributaries like Yamuna, Ghaghara, Gandak and Kosi join it.
    • The river Yamuna rises at Yamunotri fancier joined Ganga at Allahabad.
    • The Chambal, the beta and the son are peninsular are the peninsular tributaries join in it.
    • At Tarakka in West Bengal, the river Ganga bifurcates(branched off)
    • One branch goes to southwards and joins the Bay of Bengal and other branch goes to Bangladesh and is joined by the Brahmaputra and is known as Meghma.
    • Largest Delta – Sunderbans Delta.
    • It has the length of 2500 km.

    The Brahmaputra River System

    • The Brahmaputra rises in Tibet east of Mansarovar lake.
    • Most of its course lies outside India.
    • At Namcha Barwa it takes a ‘U’ turn and enters India in Arunachal Pradesh (Dihang)
    • In Tibet, the Brahmaputra carries a smaller volume of water as it is a dry and cold region.
    • But in India, it carries a large volume of water as it passes through heavy rainfall areas.
    • Every year, the river Bhramputra causes widespread destruction due to floods in Assam and Bangladesh.

    Peninsular Rivers

    The Narmada and Tapi flow westwards through a rift valley.

    The Narmada Basin

    • It rises in the Amarkantak hills in Madhya Pradesh.
    • It flows towards the west and creates many beautiful locations like ‘Marble rocks’ near Jabalpur and ‘Deadhar falls’.

    The Tapi Basin

    • The Tapi river rises in the Satpura ranges in the Betul district of Madhya Pradesh.
    • It also flows in a rift valley.

    The Godavari Basin

    The Godavari is the largest peninsular river.

    • It rises in the Western Ghats in the Nasik district of Maharashtra Valley/
    • Its length is about 1500 km.
    • The tributaries like purna, Wardha etc. join in it.
    • The tributaries like Manjira, Pen Ganga, and Wain Ganga are very large. So they are known as ‘Dakshin Ganga’.

    The Mahanadi Basin

    • It rises in the highlands of Chhattisgarh.
    • The length-860 km.

    The Krishna Basin

    • Rises near Mahabaleshwar
    • Length-1400 km.

    The Kaveri Basin

    • Rises in the Brahmagiri ranges of Western Ghats.
    • Length- 760 km.

    Types of Lakes

    Lakes differ from each other in shape, size and other characteristics.

    1. Permanent Lakes- Most of the lakes are permanent
    2. Seasonal Lakes- Contain water during the rainy season. Sambhar lake in Rajasthan example of the seasonal lake.
    3. Some lakes are the result of the action of glaciers or ice-sheets.
    4. Ox-bow lakes- In the floodplains. Oxbow lakes ae found.
    5. Fresh water lakes. Eg. Dal lake, Nainital.

    Damming of rivers for the generation of Hydel power led to the formation of lakes.

    Water lake is the result of tectonic activity.

    Importance of lakes and river in the Economy

    • Lakes help to regulate (control) the flow of a river.
    • It prevents floodings during rainfall and maintains even flow of water during the dry season.
    • The river and lakes can be used for developing hydel power.
    • They moderate the climate of the surrounding and maintain aquatic eco-system.
    • They help to develop tourism and provide recreation (enjoy must fun)
    • Water from rivers is a natural resource which is essential for various human activities.
    • Kaveri joins the Bay of Bengal at Cuddalore in Tamil Nadu.

    Largest Salt Lake- Chillka Lake, Orissa.

    Freshwater Lake- Winlar Lake in Jammu and Kashmir.

  • Notes of Physical Features of India Chapter 2 Class 9th Social Science Geography

    Chapter – 2 Physical Features of India

     

    1. Major features of the earth are mountain, plateaus, plains islands and dessert.

    Origin of the Earth

    • Theory of plate tectonics- According to this theory, the upper part of the earth (crust) is made up of 7 major and some minor plates.
    • The movement of the plates results in folding, faulting, and volcanic activity.
    • There are 3 plates movements

    (a) Convergent Boundary- When some plates come towards each other convergent boundary is formed

    (b) Divergent Boundary- When some plates someone away from each other divergent boundary is formed.

    (c)Transform Boundary- When two plates come together, they may either collide or crumble or one may slide under the other.

    How were the Himalayas formed?

    • The Himalayas were once the part of Gondwana land.
    • The Gondwana land included India, Australia, South America, South Africa and Antarctica as one single land mass.
    • The conventional currents split the crust into pieces.
    • The Indo-Australia plate, which was separated from Gondwana land began to move towards the north.
    • Then, it collided with the much larger Eurasian plate.
    • As the result of the collision, Tethys was folded and the Himalayas were uplifted.

    Formation of Northen Plains

    • The Himalayan uplift out of Tethys Sea, resulted is the formation of a large basin.
    • In the due cause of time, these plains get filled with sediments brought down by Himalayan river.
    • A flat land of alluvial deposits led to the formation of Northen Plain.

    Major Physiographic Division

    • The Himalayan Mountains
    • The Northen plains
    • The Peninsular Plateau
    • The Indian Desert
    • The Coastal Plains
    • The Islands

    The Himalayan Mountain

    They are young fold mountains and runs in the west-east direction.

    They are highest and the most rugged mountains barriers in the world.

    They form an arc and covers the distance of 2400 km.

    The Himalayas consists of 3 parallel ranges i.e., Himadri, Himachal, Shivalik.

                                                                Himadri

    Himadri is the northern most range of Himalayas also known as great or inner Himalayas.

    Important Himalayas peaks are located here with the average height of 6000 m.

    It is composed of granite and snow bound.

    Himachal

    The range lying to the south of Himadri is called Himachal, also known as lesser Himalayan.

    Their height varies from 3700 m and 4500 m.

    The famous valleys like Kashmir, Kangra, and Kullu are located here.

    Shivalik

    It is the outer most range of Himalayas.

    These valleys are covered with gravel and aluminum. some important dunes are located like Deharadun, pattidum, and Kotlidum and located here. [Dunes – The valley lying lesser Himalayas and shivaliks]

    How are the Himalayas divided on the basis of the region?

    (i) Punjab Himalayas.

    The region lying between Indus and Satluj river.

    (II) Kumaon Himalayas

    The region lying between satluj and Kali river.

    (III) Nepal Himalayas

    The region lying between kali and Tista river.

    (IV) Assam Himalayas

    The region lying between Tista and Dihag river.

     

    Purvanchal/Eastern Hills

    • Beyond Dihang gorgl, the Himalayas bend sharply towards the south and spread along the eastern boundary.
    • They are composed of sand stone and covered with dense forests.
    • Purvanchal comprised of Parkai Hills, Naga Hills, Manipur hills and Mizo hills.

    Northern Plains

    • Northern Plains has been formed by the three rivers, i.e. Indus, Ganga, and the Brahmaputra.
    • They are formed of alluvial soil and are very fertile.
    • They are densely populated and agriculturally a very productive part of India. Due to sufficient water supply, favorable climate and fertile soil.

    River in Island

    In the lower course, the velocity of the river decrease which results in the formation of the river in the island.

    Distributes

    The river in their lower course split into numerous channels.

    Tributaries

    Many streams/rivers join the main rivers.

    Sections of Northern Plain

    Northern plain is divided into 3 sections.

    Punjab Plain-

    It lies to the western part of Northern Plain. It is formed by Indus and its tributaries.

    Ganga Plain

    It lies between ghagger and Tista rivers.

    Brahmaputra Plain

    It lies to the east of Ganga Plains.

    A region of Northern Plain

    The northern plain is divided into 4 regions.

    • Bhabur 

    The river after descending from mountains, deposit pebbles in a narrow belt of 8 to 16 km.

    • Terai

    All the streams disappear in the Bhabur belt and reemerge in a wet and marsley region.

    • Bhangar

    The region with older alluvium.

    • Khadar

    The region with newer alluvium. They are renewed every year and are very fertile.

    The Peninsular Plateau

    • The peninsular plateau is a tableland and composed of igneous, metamorphic and crystalline rocks.
    • It has broad and shallow valleys and rounded hills. It is divided into two:-

    (i) Central Highlands

    (ii) Deccan Plateau

    Central Highlands Deccan Plateau
     It lies to the north of Narmada

    River.

    		 It lies to the south of Narmada

    River.
    It is wider in the west and narrower

    in the east.

    		 It is a triangular land

    mass
     The Chambal, sind, betwa etc are the

    important river.

    		 It is higher in the west and slops

    eastwards.
     Bundelkhand and Baghilkhand are

    the eastward extension

    		 The Garo, the Khasi, the Jaintia

    are the important hill ranges.

     

    Compare and contrast western ghats and eastern ghats.

    They are continuous and higherthan eastern ghats,

    Western Ghats Eastern Ghats
    Western ghats are the western

    edge of the Deccan Plateau

    		 Eastern Ghats are the eastern

    edge of Deccan Plateau
    They are discontinuous and

    dissected by riveghats,
    Their average elevation is 900-

    1600 meters

    		 The elevation (height) is 600

    meters.
    Anaimade is the highest peak

    (2695 meter)

    		 Mahendragiri is the highest peak

    (1501 meter).

    Deccan Trap

    The black soil are in the peninsular plateau.

    The Indian Desert

    • The Indian desert lies to the western margins of the Aravali hills.
    • It is ab undulating sandy plain covered with sand dunes.
    • This area receive very low rainfall and has an arid climate with low vegetation.
    • Luni is the only large river.

    Barch and – The crescent-shaped dunes.

    Coastal Plains

    India has two coastal plain:-

    • Western Coast.
    • Eastern Coast
    • Western Costs lies between the Western Ghats and Arabian sea.
    • Eastern Coast lies between Eastern Ghats and Bay of Bengal.

    Western Coast

    It is divided into 3 sections

    • Konchan- Northern part of the western coast.
    • Kannad- untral part of the western coast.
    • Malabar- Southern part of the western coast.

    Also, Check: Chapter-1 India- Size and Location Notes Class 9th SST

    Eastern Coast

    It is divided into 2 sections.

    • Northern Circar – The northern part of Eastern Coast
    • Corom andel Coast- The southern part of Eastern Coast.

    The Islands

    India has two island groups

    • Andaman and Nicobar
    • Lakshadweep

    Lakshadweep Islands

    They lie close to Malabar coast of Kerala.

    Earlier they were known as Laccadive, Minicoy and Amindiee.

    In 1973 these islands  are name as Lakshadweep.

    It covers a small area of 32 sq. km.

    Kavaratti flead quarters.

    Andaman and Nicobar Islands

    They are located in Bay of bengal

    They are bigger in size, mumerous and scattered.

    Andaman islands are located in the north and nicobar islands in the south.

    They lie close to the equator and so they have an equatarial climate.

    Portblair is the headquarter of Andaman and Nicobar Islands.

    Each Physiographic divisions complements the others explain.

    The mountains are the major sources of water and forest. The northern plains are the granaries of the country..

    The plateau is the storehouse of minerals.

    The coastal regions and island groups provide sites for fishing and part activities.