STRUCTURE OF ATOM CLASS 9TH

1. Charged Particles in Matter

 

Protons were discovered by Ernest Ruther by  gold foil experiment.

Electrons were discovered by J.J. Thomson, by cathode ray tube experiment.

Neutrons were discovered by James Chadwick.

Charged Particles in Matter

  • Atoms consist of protons and electrons
  • Protons exist in the inside  of the atom and electrons form the outer part  of the atom. Therefore, electrons can be removed from an atom.

2. Dalton’s Atomic Theory

The postulates of the atomic theory by John Dalton

  • The matter is made up of tiny particles called Atoms that cannot be divided.
  • Atoms are never formed or destroyed during a chemical reaction.
  • Atoms of an element exhibit same nature. They have the same size, mass, and character.
  • Atoms of different elements exhibit variant nature. They do not have same characteristics.
  • Atoms form compounds by combining in a ratio of whole numbers.
  • A compound contains a constant number and kinds of atoms

Thomson’s Model of an Atom

According to J.J. Thomson, the structure of an atom can be compared to Christmas pudding where electrons are present inside a positive sphere.

Thomson’s Model of an Atom

An atom is composed of a positively charged sphere in which electrons are embedded.

Atom is neutral as the positive and negative charged are equal in proportion.

Rutherford’s Model of an Atom

Rutherford’s Experiment

  • He experimented with thin gold foil by passing alpha rays through it.
  • He expected that the gold atoms will deflect the Alpha particles.

Thus, Rutherford gave the nuclear model of an atom based on his experiment which suggests that –

  • Atoms contain a lot of unoccupied space
  • There is a heavily positively charged substance present in the center of the atom which is called the nucleus
  • The nucleus contains an equal amount of positive and negative charge.

The Nucleus of an Atom

  • The nucleus id located at the center of the atom.
  • All the mass of the atom is because of the nucleus.
  • The electrons revolve around the nucleus in circular parts which are called Orbits
  • If we compare the size of the atom and nucleus, the nucleus is much smaller than the atom.

 

Drawbacks of the Nuclear Model of an Atom

The Nuclear Model of the Atom failed to explain how an atom remains stable despite having positive and negative charges present in it. Maxwell has suggested a theory according to which if any charged particle moves in a circular motion it radiates energy. So, if electrons start moving in a circular motion around the nucleus they would also radiate some energy which would decrease at the speed of the electrons. As a result, they would fall into the nucleus because of its high positive charge.

What are nucleons? –  Protons and Neutrons are collectively called as Nucleons.

Bohr’s Model of an Atom

Bohr suggested that –

  • Electrons spin around the nucleus in an individualized separate path or unattached orbit.
  • The electrons do not emit any energy while moving Indies special orbits.
  • These orbits are also called as Energy Levels.
  • They are represented using letters or numbers as shown in the figure below –

Bohr's Model of an Atom

The Neutrons

J. Chadwick discovered that there is another sub-atomic particle present in the atom. This particle carries no charge and is known as a Neutron. Therefore, we can conclude that atom consists of three types of particles –

Electronswhich carry a negative charge
Protonswhich carry a positive charge
Neutronsthey are neutral

The distribution of electrons in different shells or orbits

  • If Orbit number = n
  • Then number of electrons present in an Orbit = 2n2
  • So, for n =1
  • Maximum electrons present in shell – K = 2 * (1)2 = 2
  • The outermost shell can contain at most 8 electrons.
  • The shells in an atom are filled in sequence.
  • Thus, until the inner shells of an atom are filled completely the outer shells cannot contain any electrons.

Valency

  • Valence Electrons – Electrons existing in the outermost orbit of an atom are called Valence Electrons.
  • The atoms which have completely filled the outermost shell are not very active chemically.
  • The valency of an atom or the combining capacity of an atom is given by the number of elements present in the outermost shell.
  • For Example, Helium contains two electrons in its outermost shell which means its valency is two. In other words, it can share two electrons to form a chemical bond with another element.
  • What happens when the outermost shell contains a number of electrons that are close to its maximum capacity?

Valency in such cases is generated by subtracting the number of electrons present in the outermost orbit from octet (8). For example, oxygen contains 6 electrons in its outermost shell. Its valency is calculated as: 8 – 6 = 2. This means oxygen needs two electrons to form a bond with another element.

Atomic Number of an Element

Atomic Number (Z) = Number of protons in an atom

Mass Number of an Element

Mass Number = Number of protons + Number of neutrons

Isotopes

  • The atoms of an element can exist in several forms having similar atomic numbers but varying mass numbers.
  • Isotopes are pure substances.
  • Isotopes have a similar chemical nature.
  • Isotopes have distinct physical characteristics.

 

Where can we use Isotopes?

1. The fuel of Nuclear Reactor – Isotope of Uranium

2. Treatment of Cancer – Isotope of Cobalt

3. Treatment of Goiter – Isotope of Iodine

Example: Consider two atomic species namely U and V. Are they isotopes?

UV
Protons55
Neutrons56
Mass Number5 + 5 = 105 + 6 = 11
Atomic Number55

From the above example, we can infer that U and V are isotopes because their atomic number is the same.

Isobars

The atoms of several elements can have a similar mass number but distinct atomic masses. Such elements are called Isobars.

IS MATTER AROUND AS PURE CLASS 9TH

1. What is a substance?

  • Anything that cannot be broken into  more small  particles by applying any physical processes is called a Substance.
  • Matter can be classified into two types of substances – Pure substances and Mixtures

2. What is a pure substance?

A substance which  consists of only one type of particle is called a Pure SubstanceFor Example, Diamond, Salt, Sulfur, Tin, oxygen , etc

3. What is a mixture?

  • When we combine different substances into each other a mixture is formed. For Example,  water is a mixture of hydrogen and oxygen etc.
  • 4. Types of Mixtures

There are two  type of mixtures:

Homogeneous Mixtures ,and

Heterogeneous Mixtures..

5. Homogenous Mixtures

  • When we add sugar, water and lemon juice together they all uniformly mix with each other. Now it is no possible to separate these substances from the mixture. when the composition of particles  is same through out the  mixture

6.Heterogeneous Mixtures

  • The components in a heterogeneous mixture do not completely dissolve in each other and we can separate them by physical means. In other words, the composition of such mixtures is not uniform.
  • For Example, If we mix sand in water the sand settles down in water after some time and we can separate it by filtration.

Here are a few differences between homogeneous and heterogeneous mixtures –

Homogenous MixturesHeterogeneous Mixtures
They have a uniform composition throughoutThey have a non-uniform composition
We cannot separate the components of the mixture through physical processesWe can separate the components through physical processes
Components cannot be seen through naked eyesComponents can easily be seen through naked eyes
The mixture is in single phase throughoutThe substances can be of two different phases and we may see separate layers of the substances
Example: A mixture of water and milkExample: A mixture of oil in water

7.What is a solution?

Homogenous Mixtures   is called solution

ex.. tea, lemonade.. etc

8.What is an alloy?

An alloy is a mixture of different metals or non-metals and metals that cannot be separated from each other using physical methods. For Example:

Brass – Copper with zinc

Bronze – Copper with  tin

note ;Solution constitutes of two types of substances, a solute and a solvent.

10. Solution = Solute + Solvent

Solvent – The substance in which another substance is mixed is called the SolventFor Example, Water is a solvent in which we can mix different substances such as salt or sugar.

Solute – The substance that is added to the solvent to form a solution is called a SoluteFor Example, Salt, when mixed in water, acts as a solute for the mixture.

11. Properties of a Solution:

  • A solution is a homogenous mixture.
  • We cannot see the particles of a solution through naked eyes as they as are small as 1 nanometer in diameter.
  • The path of light is not visible through the solution. The particles of a solution do not scatter light through them as they are extremely small.

12. What is concentration?

Concentration  can be defined as the ratio of solute in solvent ..

To calculate the concentration consider the formulae below:

  • Percent by Mass = (Mass of solute / Mass of solution) X 100
  • Percent by Volume = (Volume of solute / Volume of solution) X 100

13. What is a suspension?

Heterogenous mixture is known as suspension .

14. Properties of Suspensions:

  • A suspension is a heterogeneous mixture.
  • We can see the particles of suspensions through naked eyes.
  • We can see the path of light through the particles of a suspension.
  • The particles of suspension tend to settle down when left undisturbed. Then, they can be separated using filtration.

15.What are colloids or colloidal solutions?

is a type of mixture which look like a homogenous but actually its act like a heterogenous mixture .

16. Properties of colloids:

  • Colloids are heterogeneous in nature.
  • The particles of a colloid cannot be seen through naked eyes.
  • The particles scatter a beam of light passed through a colloid and produce Tyndall effect.
  • Colloids are stable in nature. The particles of colloids do not settle down if left uninterrupted.
  • We cannot separate the particles of a colloid through filtration. We use a method called Centrifugation to separate the particles of a colloid.
  • 17.What is the Tyndall Effect?

When a beam of light is passed through a colloid the particles of the colloid scatter the beam of light and we can see the path of light in the solution. For Example, when a ray of light enters a dark room it is scattered by the dust particles present in the air and we can see the path of light clearly

18.Types of Colloids

ExampleDispersing MediumDispersed Substance Colloid Type
Fog, Aerosol spraysGasLiquidAerosol
Smoke, Airborne bacteriaGasLiquidAerosol
Whipped cream, Soap sudsLiquidGasFoam
Milk, MayonnaiseLiquidLiquidEmulsion
Paints, Clays, GelatinLiquidSolidSol
Marshmallow, StyrofoamSolidGasSolid foam
Butter, cheeseSolidLiquidSolid emulsion
Ruby glassSolidSolidSolid sol

19. How to separate components of a mixture?

We can separate the heterogeneous mixtures into their constituents by means of physical methods like:

  • Filtration
  • Evaporation
  • Centrifugation
  • Sublimation
  • Chromatography
  • Distillation

1. Evaporation – For separating a mixture of a non-volatile and a volatile substance

  • Applications:
    • Separating coloured component from the ink
    • Salt from water
    • Sugar from Water
  • Method:
    • Mix some ink into water and heat it. After some time the water will evaporate leaving behind the coloured substance.

2. Centrifugation – Separating dense particles from lighter particles

  • Applications:
    • Separating milk from cream
    • Separating butter from cream
    • Squeezing out water from wet clothes
  • Method:
    • Milk is put in a centrifuging machine or milk churner and the cream thus separates from milk.

3. Using a Separating funnel – To separate two immiscible liquids

  • Applications:
    • Oil from water
    • Iron and iron ore
  • Method:
    • The immiscible liquids are allowed to settle in the funnel. They soon form separate layers due to varying densities. The first liquid is allowed to flow out of the funnel and as soon as it is completely poured out, the stopcock is closed thereby separating the two liquids from each other.

4. Sublimation – To separate a sublimable component from a non-sublimable component

  • Applications:
    • Ammonium chloride / camphor / naphthalene and salt
  • Method:
    • Heat the mixture in an inverted funnel so that the sublimable component sublimes in the air and settles over the walls of the funnel and the non-sublimable component, on the other hand, is left behind.

5. Chromatography – To separate solutes that can dissolve in the same solvent

  • Applications:
    • Separating colour components of a dye
    • Drugs from blood
  • Method:
    • Take a filter paper or a blotting paper and place a drop of ink at the rear end. Dip the end in water. Since ink is a mixture of two or more colors, the component of ink which is soluble in water mixes into it and then separates quickly from the other components that are less soluble in water.

6. Distillation – To separate miscible liquids (the boiling points of the liquids must be sufficiently different)

  • Applications:
    • Acetone and water
  • Method:
    • The mixture is heated in a distillation apparatus. The one substance with lower boiling point evaporates first, condenses and gets separated from the one with a higher boiling point.
    • Simple Distillation – when the miscible liquids have a satisfactory difference in their boiling points
    • Fractional Distillation – when the difference between the boiling points of the liquids is less than 25 K

20. Separating different Gases from the Air

Method – Fractional Distillation

  • Compress and cool the air by increasing the temperature and decreasing the pressure. The air turns to liquid air.
  • Liquid air is warmed up slowly in a fractional distillation apparatus
  • The several components of air get separated and are collected at various heights on the basis of their boiling points

Purifying Solids

Method used – Crystallization

In the crystallization method, we can obtain a pure solid in the form of crystals from its solution

  • Applications:
    • Salt from sea water
    • Purification of copper sulphate
  • Method:
    • The impurities of a substance are filtered out.
    • Water is evaporated to obtain a saturated solution.
    • The solution is covered with filter paper and left as it is.
    • After some time, the crystals of pure solid are formed

Physical Change and Chemical Change

Physical Property of a Substance:

Properties of a substance such as rigidity, colour, fluidity, boiling point, melting point, density and hardness which we can observe are called as Physical Properties.

Physical Change:

When physical properties of a substance change it is known as a Physical Change. When we convert a substance from one state to another, such as a solid into a liquid or vice-versa, it is also a physical change as only the physical nature of the substance changes without affecting its chemical nature.

For Example, Change of ice into water. The chemical properties of water remain the same.

Chemical Property of a Substance:

The chemical nature of a substance is known as its Chemical Property such as its odour or its chemical composition.

Chemical Change:

When the chemical properties or chemical composition of a substance gets altered it is called a chemical change. It is also called as a Chemical Reaction.

For Example, Burning of paper

Types of Pure Substances

Pure substances are classified as elements and compounds

Elements

An element is the simplest form of matter.  Elements cannot be broken down into further elements by chemical reactions. Elements are further characterized as Metals, Non-Metals and Metalloids

Metals – Silver, Mercury, Copper, Gold

1. Metals are lustrous (shiny)

2. Metals conduct heat and electricity

3. Metals have a silver-grey or gold-yellow colour

4. We can hammer metals and form thin sheets (Malleability)

5. We can convert metals into wires (Ductility)

6. Metals always produce a ringing sound if they are hit (Sonorous)

Non-Metals – Carbon, Iodine, Chlorine, Oxygen, Hydrogen

1. Non-Metals do not conduct heat and electricity

2. Non-Metals are not sonorous, lustrous or ductile

3. Non-Metals have varied colours

Metalloids – Silicon, Germanium

They show some properties of metals and some of the non-metals

Compounds

It is a substance that consists of two or more substances. These substances are combined chemically with each other in fixed proportions. The properties of a compound are different than that of its constituents. For Example, Ammonium Sulphate, Sulphur Chloride, Water.

Mixtures vs. Compounds

Mixtures

Compounds

Properties of a mixture Reflect the properties of the materials it contians.Different properties from that of the elements that make up the compounds.
No uniform compositionDefinite composition. Definite ratio/formula
Can be separated by physical means.Cannot be separated by physical means.

matter in our surrounding ( important questions cum test ) class 9

  1. Explain why?
    i. A gas fill a vessel completely.
    ii. Camphor disappears without leaving any residue.
    iii.  why The temperature does not rise or fall  during the process of melting and boiling, through heat energy is constantly supplied.
    iv. Water stored in an earthen vessel becomes cool.
  2. Which phenomenon occurs during the following changes?
    ii. Wax melts in the sun.
    iii. Drying of wet clothes
    iv. Formation of clouds
  3. . Define following
    i.Melting point
    ii.Boiling point
    iii.Vapourisation
    iv.Freezing                                                                                                      v. Sublimation
    vi. .Diffusion
  4. What is latent heat?
  5. Give reasons-
    a.The water kept in earthen pot (matka) remain cool?
    b.Smell of perfume or foood  is spread all over the room.
  6. Convert-
    a.84° C to Kelvin
    b.309 K to ° C
    c. 0 ° C to Kelvin
  7. describe  the characteristics of particle of matter?
  8. why are liquids more compressable than  solid ?
  9. why should wet clothes  be spread while drying ?
  10. write down full form of LPG and  CNG . Mention their properties which make them so important .
  11. rubber band changes its shape . Is it solid ?
  12. why do liquid flow?
  13.  what is evaporation ? write down name of factors which affect the rate of evaporation .
  14.  differentiate between states of matter on the base of following properties                                                                                 i . intermolecular force                                                                             ii. arrangment of molecules.
  15. why should  we wear cotton clothes in summer ?
  16. why we feel cool when we pour some acetone on our palm ?
  17. why small drop of water appear on glass when it is fill with cold water?
  18. why we use dessert cooler in summer ?

Mineral Resources(Important questions cum test) class 10

  1. State any two factors affecting the economic viability of mineral reserves?
  2. . How do minerals occur in igneous and metamorphic rocks?
  3. Explain Rat-Hole mining in the tribal areas.
  4. . Mention three properties of mica.
  5. Why is conservation of mineral resources essential? Explain any three
    methods to conserve them.
  6. In which various forms do minerals occur?
  7. Give an account of the distribution of minerals in India.
    Or
    ‘Minerals in India are unevenly distributed’. Explain.
  8. On the given political outline map of India, two features A and B are marked.
    Identify these features with the help of the following information:
    A. Iron-ore mines
    B. Terminal station of North-South Corridor
    On the same map locate and lable the following:
    (i) Gandhinagar Software Technology Park.
  9. Locate and label the following features with appropriate symbols on a political
    outline map of India.
    (i) Balaghat — Manganese (ii) Kendujhar — Manganese
    (iii) Koraput — Bauxite (iv) Bilaspur — Bauxite
    (v) Hazaribagh — Mica
  10. Why is conservation of minerals important?
  11. Why is the use of non-conventional sources of energy becoming essential these days?

Print Culture and the modern world (important question cum test) Class-10

  1. What was the attitude of liberal and Conservative Indians towards women reading? how did women like Kailashbhashini Debi respond to this in their writing?
  2. Explain the role of missionaries in the growth of press in India?
  3. Explain how did the earliest printing technology developed in the world?
  4. Three features of handwritten manuscripts before the age of print in India?
  5. Explain the role of print culture in bringing the french revolution?
  6. Any three factors responsible of new technologies of new printing technique. Explain?
  7. Explain the knowledge of wood block printing came to Europe?
  8. Printing press played a major role in shaping the 19th century Indian society . explain the statement?
  9. How did the print book bring reading and hearing public together. Explain
  10. What was the attitude of liberal and conservative indians towards women reading? How did women like Kailashbhashini debi respond to this in their writing?
  11. Define the role of print culture in bringing of french revolution?
  12. Any three features of handwritten manuscripts before the age of print in India. Explain?

Social Science -Nationalism in India(Test cum important question)

  1. Discuss the Salt March to make clear why it was an effective symbol of
    resistance against colonialism.
  2. Imagine you are a woman participating in the Civil Disobedience Movement.
    Explain what the experience meant to your life.
  3. Why did the Non-Cooperation Movement gradually slowdown in the cities?
    Give three reasons.
  4. What were the three local issues in which Gandhiji experimented his technique of Satyagraha during the years 1917-18? How were these issues resolved?
  5. What was Rowlatt Act? How did the Indians show their disapproval towards
    this Act?
  6. . Mention three main proposals with reference to the Non-cooperation Movement as suggested by Mahatma Gandhiji.
  7. How did Khilafat movement gain momentum? or How did Mahatma Gandhi
    view the Khilafat issue?
  8. An important feature of the Civil Disobedience Movement was the large-scale
    participation of women. Explain.
  9. How was history re-interested in creating a feeling of nationalism? Explain
    with examples.
  10. What was the Inland Emigration Act of 1859?
    Or
    What was the notion of Swaraj for the plantation workers in Assam?
  11. How did the business classes relate to the Civil Disobedience Movement?
    Or
    Who led the business community during the Civil Disobedience Movement?
    How did the community provide a big boost to the Movement?
  12. The First World War created a new economic and political situation. Explain.
  13. “Nationalism spreads when people begin to believe that they are all part of
    the same nation.” Support the statement.
  14. Give a brief description of Gandhiji’s contribution to the Indian freedom
    struggle.
  15. How culture played a vital role in awakening of the feeling of nationalism?