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.


  • 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


  • 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?

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.


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


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


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


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



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.


It is a hollow cage which exits in the form of sphere. Its structure is similar to fullerene. But along with hexagonal rings, sometimes pentagonal or heptagonal rings are also present.


Carbon has atomic no. 6

electronic configuration-  2,4

valance- 4

Food, clothes, medicines,books or many of the things that you listed are all based on this versatile element carbon. in addition, all living structure are carbon based.

The amount of carbon present in earth crust and in the  atmosphere is quite meagre .

The earth crust has only 0.02% carbon in a form of minerals (  like carbonates, Hydrogen-carbonate, coal, and petroleum) and the atmosphere has 0.03% of carbon dioxide


The bond formed by sharing a pair of electrons between two atoms are known as Covalent Bond. Carbon forms covalent bond. Carbon exists in two forms- as free state and as combined state. Free form of carbon is found in graphite, diamond and fullerene. In combined state, carbon exists as Carbon-dioxide, Glucose, Sugar etc


A. SINGLE BOND – It is a type of bond which is formed by the sharing of single electron

ex.- bond between two hydrogen atom

H•+H•→H••H or H–H
b. DOUBLE BOND – It is a type covalent bond which is  formed by sharing of two electron
ex-  bond between two oxygen atom
O: + O: —- O==O or O::O
C. TRIPLE BOND-  It is a type of covalent bond which is formed by sharing of triple electron
N:. + N:. —-  N\\\N
Triple bond formation of nitrogen.
  Electron forming ionic compound achieve thus either by gaining and losing electron from the outermost shell . In the case of carbon, it has four electrons in its outermost shell and needs to gain or lose four electron to attain noble gas configuration .if it were to gain or lose it
1. it could gain four electron forming C4- anion. but it would be difficult for the nucleus with 6 proton to hold on to ten electron that is four extra electron.
2. it could lose four electrons formingC4+ cation . but it would require  a large amount of energy to remove four lectron leaving behind a carbon with six proton in its nucleus holding on to just two electrons.
5.Allotropes of Carbon

Different forms of an element that has same chemical properties but different physical properties are known as Allotropes. There are three allotropes of carbon- diamond, graphite and fullerene.


Diamond exits as three-dimensional network with strong carbon-carbon covalent bonds. Diamond is hard in nature with high melting point. It shines in presence of light and it is a bad conductor of electricity. The most common use of diamond is in making jewellery. It is also used in cutting and drilling tools.


Graphite is made from weak van der wall forces. Each carbon atom is bonded with other three carbon atoms in order to form hexagonal rings. It serves as good conductor of heat and electricity. It is used as dry lubricant for machine parts as well as it is used in lead pencils.


It is a hollow cage which exits in the form of sphere. Its structure is similar to fullerene. But along with hexagonal rings, sometimes pentagonal or heptagonal rings are also present.

Structure of fullerene


Compounds which are made up of carbon and hydrogen they are known as Hydrocarbons. There are two types of hydrocarbons found – Saturated Hydrocarbons and Unsaturated Hydrocarbons. Saturated Hydrocarbons consist of single bonds between the carbon atoms. For Example, Alkanes. Alkanes are saturated hydrocarbons represented by a formula, CnH2n+2.

Unsaturated Hydrocarbons are the one with double or triple bonds between the carbon atoms. For Example, Alkenes and Alkynes. Alkenes are represented as CnH2n  they have carbon carbon double bond .

whereas alkynes are represented as CnH2n-2. they have carbon carbon triple bond

ydrocarbons are represented as –

Saturated hydrocarbons

Unsaturated hydrocarbons

Structure of hydrocarbons can be represented in the form of electron dot structure as well as open structures as shown below-

Electron dot structure and open structure of ethane

. Electron dot structure and open structure of ethane

Electron dot structure and open structure of ethyne

5. Electron dot structure and open structure of ethyne


Carbons Compounds based on the basis of structure

Carbon Compounds can be classified as straight chain compounds, branched chain compounds and cyclic compounds.They are represented as –

Straight chain carbon compound

. Straight chain carbon compound

Branched chain compounds7. Branched chain compounds

Cyclic carbon compounds

Fig.8. Cyclic carbon compounds

Functional Groups

One of the hydrogen atoms in hydrocarbon can be replaced by other atoms according to their valencies. The atoms which decides the properties of the carbon atoms, are known as Functional GroupsFor Example, Cl, Br, -OH, Aldehyde, Ketone, Carboxylic Acid etc.

Homologous Series

Series of compounds in which same functional group substitutes for the hydrogen atom in a chain of carbon.

Homologous series

Fig.9. Homologous series

Nomenclature of Carbon Compounds

  • First of all, identify the number of carbon atoms in compounds. And in it identify the longest chain
  • Then functional group can be indicated by suffix or prefix.
  • Cyclic hydrocarbon is designated by prefix cyclo.
  • If there are two or more different substituents they are listed in alphabetical order
  • If the same substituent occurs more than once, the location of each point on which the substituent occurs is given

Different functional groups

Fig.10. Different functional groups

Chemical Properties of Carbon Compounds


Carbon along with its compound is used as a fuel as it burns in presence of oxygen to release energy. Saturated hydrocarbons produce blue and non-sooty flame whereas unsaturated hydrocarbons produce yellow sooty flame.

CH4 + 2O2 → CO2 + 2H2O


Alcohol can be oxidized to aldehydes whereas aldehydes in turn can be oxidized to carboxylic acid. Oxidizing agent such as potassium permanganate can be used for oxidation.


Addition Reaction

Hydrogenation of vegetable oil is an example of addition reaction. Addition of hydrogen in presence of catalyst such as nickel or palladium. This converts oil into ghee.

Addition Reaction

Substitution Reaction

When one atom in hydrocarbon is replaced by chlorine, bromine, etc. this is known as Substitution Reaction.

Substitution Reaction.

Important Carbon Compounds: Ethanol and Ethanoic Acid

Ethanol is a volatile liquid with low melting point. It reacts with sodium to form sodium ethoxide.

This above reaction is used to test the presence of ethanol by the evolution of hydrogen gas.

Dehydration of ethanol in presence of hot sulphuric acid forms alkene.

Ethanoic Acid

Ethanoic acid is a colourless liquid. When pure ethanoic acid freeze like ice, it is known as Glacial Acetic Acid.  It is formed at a temperature of about 16.6 degree centigrade

Ethanoic Acid/Acetic acid when reacts with ethanol it forms an ester. Ester can be identified by its sweet smell.

Ethanol and Ethanoic Acid

Reaction of ester with strong base is used to form soap. This is known as Saponification. Acetic acid also reacts with strong base to form sodium acetate and water.


Soaps and Detergents

Sodium or potassium salt of carboxylic acid is known as Soap. They work most effectively in soap water. Detergents are sulphonate or ammonium salt of long chain of carboxylic acid. They can work effectively on soft as well as hard water.

Cleansing Action of Soaps and Detergents

Cleansing action of soaps and detergents is due to ability to minimize the surface tension of water, to emulsify oil or grease and to hold them in a suspension of water. When soap dissolves in water, it forms soap anions and soap cations. The hydrophobic part of soaps and detergents are soluble in grease and hydrophilic part is soluble in water.

Soap and Micelle Formation

When dirt and grease are mixed with soap water, soap molecules arrange them in tiny clusters known as Micelle. The hydrophilic part sticks to the water and form outer surface of the micelle and hydrophobic part binds to oil

and grease.

Soap and Micelle Formation

Matter in our surrounding ( Important question 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
    iv.Freezingv. Sublimationvi. .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 compressible 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 ?

Chemical reaction and equations ( Imporatnt question cum test ) class 10

1.What is a redox reaction? explain with 2 examples
2. What is corrosion? how we can avoid corrosion.
3. What is rancidity? How can we get raid of rancidity?
4. How is corrosion different from rusting?
5. What is meant by endothermic and exothermic reactions? Give two example for each.
6. Define all types of chemical reaction and give examples for each.
7. photosynthesis is considered as an endothermic reaction. explain why ?
8. Give one use of quick lime..
9. Give three types of decomposition reaction
10. Which one is a chemical change-rusting of iron or melting of iron?
11. What happens when quicklime is added to water?
12. balance the following chemical reaction and write the name of the reaction
i. Barium Chloride + Aluminium Sulphate

Barium Sulphate + Aluminium Chloride
ii. quike lime + water —— calcium hydroxide
13. Predict the type of each reaction.

2Ag +S—-Ag2S
NH4NO2—-N2 + 2H2O
2NAI + CI2—- 2NaCI + I2
CuCI2 + 2NaOH—- Cu (OH)2 + 2NaCI
14. Predict the products for the following reactions and balance.

HCI + Zn—
NaBr + Cl2—
H2SO4 + Fe—-
Na + H2O—-
Cu + AgNO3—-
KHO + H2SO4—
Al2 (SO4)3 + NaOH—
BaCI2 + Na2SO4—

PbSO4 + Na2CO3—
15. What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?

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
    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 ?


  1. CHEMISTRY-  chemistry is the branch of science that studies the composition , structure , properties, and transformations of matter and also energy associated with these changes.
  2. MATTER- matte is anythin/g that occupies space and has mass .
  3.  matter  exists in 3 physical state …… SOLID , LIQUID , GAS
  4. solid  is composed of matter where the particles have strong attractive force , aare closed together and have fixed position . solid have definite shape and definite volume .
  5. liquid – a liduid is composed of matter where the particle are closed together but have weak attreactive force so that, they are able to move past one another therefore , liquid have a definite volume but  not fixed shape.
  6.   GAS –  a gas is made up of atom or molecule with large interparticle distance, which moves independently in all directions in random motion . gases neither have definite volume nor definite shape .
  7. Matter is classified as  pure substance  and misture 
  8. pure substance  are either element or compound are always homogenous in composition .
  9. mixture –  mixture are always contain two or more susbstance which may be either homogenous or heterogenous .
  10. Homogenous mixture   has uniform composition , apperence and properties throught out the solution
  11. Heterogenous mixture  has 2 or more physically distinct phase and composition is not uniform throught the solution .
  12. The  international system  or metric system  is a decimal system of  unit for measurment of mass , lenght, time etc..
  13.  The mass is the amount of matter  present in a substance and is measure very accuratly in the laboratry by using an analytical  balance .
  14. The  weight  of substance is firce exerted by gravity on an object
  15. The mass of an object is constant whereas the weight changes from place to place .
  16. Density   of substance is its amount of mass per unit volume . Its unit is kg /m3
  17. The SI UNIT of  TEMPERATURE   is K ( KELVIN ) .It also measure in °C  and °F                                                                                                                            °F=9/5 °C +32                                                                                                  K= °C =273.1
  18.   laws of chemical combination , ;  compound are formed from element and their formation is governed bu the 5 rules .                                                                                                                     1.  law of conservation of mass –  It state that the matter can neither be created nor be destroy  .                              2.  law of definite proportion –  the ratio of the mass of element in any compound is constant regardless of its source of its preparartion .                                                                          3.  law of multiple proportion –  if 2 element can combine to form more than 1 compound  the mass of one element that combine with fixed mass of the other element , are in the ratio of small whole no.                                         4.  gay lussac’s law of gaseous volume –  when gases combine or are produce in chemical rxn they do so in a simple ratio by volume provided all gases are at same temprature and pressure .                                                                            5.  avogadro law –  equal volume of gases at the same temprature and pressure should contain equal no. of molecule .
  19. DALTON’S ATOMIC THEORY ;                                                              1.  matter consist of indivisible atoms                                               2. all the atom of given element have identical properties including mass. atoms of different elements differ in mass.                                                                                                                  3. compound are formed when atom of different element combine in fixed ratio .                                                             4. chemical rxn involve reorganisation of atoms. These are niether be created  nor be destroy  in chemical rxn.
  20. ATOMIC MASS-    of an element is the average relative mass of its atom on a scale in which an atom of carbon -12 has a mass opf exactly 12u and 1u= 1.67377 x 10 -27 kilogram (kg), or 1.67377 x 10 -24 gram (g)
  21. one  atomic mass unit  is defined as a mass exactly equal to 1/12 mass of carbon-12 atom .
  22. the sum of atomic masses of elements present in a molecule is called  molecular mass  and in an ionic compound is called  formula mass . 
  23. one mole  of a substance is the amount of substance that contain as many particles or entities as there are atom in exactly 12g of C-12
  24. for determinng the % composition  of each element in a compound ;                                                                                                        mass percent = (mass of chemical/total mass of compound) x 100.
  25. The  empirical formula  is the simplest whole no. ratio of atom present in a compound . The  molecular formula  is exact no. of different types of atoms present in a molecule of compound
  26. stoichiometry  deals with the calculation of masses of reactant and limits the amoumnt of product formed is called  limiting reagent.
  27. concentration of the solution  cab be expressed in following way.                                                                                                    1. mass percent = (mass of chemical/total mass of compound) x 100.                                                                                                                                                                                                                               2. Mole fraction of solute = (moles of solute) / (total number of moles)                                                                                                                                                                                                                                 3.    Molarity (M)=
    moles solute
    liters solution  
         4. molality = moles of solute/kilograms of solvent.