Grade -8 (Science ): Matter

                                         Unit :- 11                Matter

Chemistry : The branch of Science consisting the study of matter is called chemistry .

Matter :Any substance which occupies space and have mass is called mater .For example :air water, Hydrogen, stone etc.

Element: The pure substance which can not be converted or broken down into two or more simpler substance by any physical or chemical process is called element .There are about 118 elements in the nature .Out up these 92 elements are found in nature or formed naturally are called natural elements .Remaining 26 elements are man made, are called artificial elements .

Atom : The smallest particles element is called atom .For example: Atoms of  H. O, N, Na, Al, C, etc.

Properties of atoms: i.) They takes part in chemical reaction  without division.

ii.)They are electrically neutral .

iii.)They can neither created  nor destroyed .

iv)  They can not be further divided .

iv)It is the smallest unit of an element .

Sub –atomic particle :According to Lord Earnest Rutherford an is made of three smallest particles i.e. Proton ,neutron, and electron are called subatomic particles .

Proton: The positively  charged subatomic particles is called proton .They are located in the Nucleus of atom .The mass of proton is equal to the mass of hydrogen i.e. 1 a.m.u. (atomic mass of unit ). It is denoted by P⁺ .

Neutron :The charge less  or Neutral subatomic particles of is called Neutron .They are located in the nucleus of an atom .The mass of neutron is equal to proton i.e. 1 a.m.u. It is denoted by n⁰ .

Electron : The negatively charged subatomic particle is called neutron .They are revolving around nucleus in an elliptical orbit .The mass of electron is about 1/1837 times the mass of hydrogen  or 1/1837 a.m.u. .It is denoted by e^- .

Nucleus   and Nucleons: The small   positively charged central part of an atom is called Nucleus .All protons and neutrons are present in the nucleus .

The protons and Neutrons present in the nucleus of an atoms are collectively known as nucleus .

Atomic number :The number of protons or electrons in an electrically neutral atom of an element is called atomic number .For example :H =1, He =2 ,Li =3 etc

Atomic number = N. of protons or N. of electrons

Atomic weight :The sum of number of protons and number of electrons in an atoms of element is called atomic mass . For example :atomic mass of He =2+2 =4  ,carbon =6+6=12 ,Nitrogen =7+7=14

Isotopes :-The elements having same atomic number but different atomic mass are called isotopes i.e.due to same atomic number but different neutrons are called isotopes .For example :Isotopes of hydrogen are protium  (₁H¹),Deuterium (₁H²) and tritium (₁H³).

Atomic number and atomic weight :

Atomic N. or Proton or electron	Name of element	Symbol	N. of Neutrons	Atomic mass or weight
1	Hydrogen	H	0	1
2	Helium	He	2	4
3	Lithium	Li	4	7
4	Berelium	Be	5	9
5	Boron	B	6	11
6	Carbon	C	6	12
7	Nitrogen	N	7	14
8	Oxygen	O	8	16
9	Fluorine	F	10	19
10	Neon	Ne	10	20
11	Sodium	Na	12	23
12	Magnesium	Mg	12	24
13	Almunium	Al	14	27
14	Silicon	Si	14	28
15	Phosphorus	P	16	31
16	Sulphur	S	16	32
17	Chlorine	Cl	18	35
18	Argon	Ar	22	40
19	Potassium	K	20	39
20	Calcium	Ca	20	40

Electronic configuration :The systematic  distribution of electrons according of their shell and is called electronic configuration .

2n² rule :The rule that gives the maximum number of electrons present in the shell is called 2n²   rule .For example :

i)K- shell = 2n²  

               = 2 x1²  =2 electrons.

ii)L- shell  = 2n²

           =2x 2²    = 8 electrons

iii)  M  -Shell =  2n²

                       = 2x 3²  =18 electrons

 

Name of shell                                  Number of shell

K  =                                         1

L  =                                          2

M  =                                       3

N=                                          4

O  =                                        5

P  =                                         6

Q   =                                       7

Compound :The substance which is formed by the combination of two or more elements by any chemical reaction in definite proportion by weight is called compound .

Properties of compound :

i)Compounds are formed by the combination of two or more elements in definite proportion by weight .

ii)They are formed by chemical reaction .

iii)Properties of compound are different from the properties of their constituents due to chemical reaction and chemical change .

iv)Compound are chemically pure substance .

v)Element of compound can be separated by chemical method.

Molecules: A smallest particles of an element or compound which can exist freely in nature is called molecule .The molecule of an element is made up one or more atoms of the same type .For example : molecule of oxygen (O₂), molecules of Hydrogen(H₂) .

But molecule of compound made up dissimilar atom .For example :molecule of water which consist of two atoms of hydrogen and one atoms of oxygen .They do not take part in chemical reaction .

Properties of molecules :

i)Molecules is smallest particles of an element or compound which can exist freely in nature .

ii) They are chemically decomposible .

iii)In molecule atoms are bonded together by chemical bond .

Radical :A radical is an atom or group of atoms different element having positive or negative charge and act as single unit during chemical reaction is called radical

Radical          Valency of elements                    Valency of radicals

Carbonate (CO₃)  = +4-6                          = -2

Bicarbonate (HCO₃)  = +1+4 -6                   = -1

Sulphate (SO₄)     = +6-8                          =2

Bisulphate (HSO₄)  =+1+6 -8                       =  -1

Nitrate (NO₃)  = +5-6                               = -1

Hydroxide (OH) = -2+1                            = -1

 Valency chart :

S.N.	Name of element s	Symbol		Valency
		Electro positive	Electro Negative
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21	Hydrogen  or hydride Potassium Sodium Silver Gold-I(Aurous) Copper –I (Coprous) Mercury –I(Mercurous) Ammonium Bicarbonate Bisulphate Hydroxide Nitrate Nitrite Chlorate Chlorite Chlorine or chloride Bromine or bromide Fluorine  or fluoride Iodine or iodide Cyanide Bisulphite	H K Na Ag Au Cu Hg (NH4)	(HCO3) (HSO4) (OH) (NO3) (NO2) (ClO3) (ClO2) Cl Br Fl I CN (HSO3)	1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43	Barium Calcium Magnesium Nickel Zinc Coppper –II(Cupric) Iron –II(Ferrous) Mercury –II(Mercuric) Lead –II (Plumbous) Tin-II(Stannous) Magnanese Iron –II(Ferrous) Oxygen or oxide  Sulpher or Sulphide Peroxide Carbonate Sulphate Sulphite Chromate Dichromate Silicate Stanate 11	Ba Ca Mg Ni Zn Cu Fe Hg Pb Sn Mn Fe	O S O2 (CO3) (SO4) (SO3) (CrO3) (Cr2O7) (SiO3) (SnO3)	2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
44 45 46 47 48 49 50	Aluminium Nitrogen or Nitride Phosphrous  or phosphide Chromium Iron-III (Ferric) Gold –III (Auric) Phosphate	Al     Cr Fe Au	N P       (PO4)	3 3 3 3 3 3 3
51 52 53 54 55	Lead –IV (Plumbic) Tin-IV(Stanic) Sulpher or sulphide Silicon Carbon or carbide	Pb Sn S Si C		4 4 4 4 4
56 56	Nitrogen or nitride Phosphrous	N P		5 5
57	Sulpher	S		6

Molecular formula :The symbolic representation of molecules of substance which show actual number of atoms present in the molecules is called molecular formula or chemical formula .For example :i) Magnesium chloride =MgCl₂, Sodium sulphate =Na₂(SO₄ ) etc.

Ways of writing molecular formula : This method is called criss –cross method.

i)Write the symbols side by side but electropositive is written first and then electronegative .

ii)Write the valency of each atom at top of its symbol .

iii)Divide the valency numbers by highest common factor then inter change the valency of symbol .

iv)Write the  inter changed valency number to the lower of the symbol .

Molecular formula of some compounds :

Name of compounds           Molecular formula

Water =                    H₂O

Carbondixide          =            CO₂

Carbonmonoxide =           CO

Ammonia       =        NH₃

Castic soda              =    Na(OH)

Castic Potash                      = K(OH)

Methene                  = CH₄

Calcium carbonate  or limestone        =Ca(CO₃)

Lime water              = Ca(OH)₂

Lime                           ₌ CaO

Hydrochloric acid =HCl

Sulphuric acid                     H₂(SO₄)

Nitric acid                =H(NO₃)

Carbonic acid                      =H₂(CO₃)

Nitric oxide                         =NO

Hydrogen peroxide          =H₂O₂

Iron oxide (rust)                =Fe₂O₃

Manganese dioxide         =MnO₂

Silica(Silicon oxide )         =SiO₂

Urea                           =NH₂-CO-NH₂

Diatomic elements           =H_2,O_2,N_2,Cl_2,Br_2,I_2,F_2,

Chemical reaction :-The exchange ,combustion or decomposition that occurs in the molecules of substances during a chemical change is called chemical reaction .

Chemical equation : The symbolic representation of the chemical reaction by writing the symbol and formula is called chemical equation .It is divided into two parts :

i)Reactant :The substance which takes part in chemical are called reactants .They are always  written in the left side of the chemical equation .

ii)Product :The substance obtained from a chemical reaction are called product .They are always written in the right side of the chemical equation .

  →i)Hydrogen +Oxygen                Water

       →2H₂    +O₂                 2 H₂O

  →i)Hydrogen +Oxygen                Water

     →         2H₂    +O₂                 2 H₂O

  →ii)Sodium +Oxygen                        Sodium oxide

  →Na +O₂                       Na₂O

Word equation :The chemical equation in which the names of substance and products are expressed in the form of word is called word equation . For example :

  → i)  Hydrogen + Oxygen                 water

  →ii) Magnessium + Oxygen                         Magnesium oxide

  →iii)Calcium carbonate                    Calcium oxide +Carbon dioxide

Types of chemical reactions :There are 4 types chemical reaction:

1)Combination reaction :The chemical reaction in which two or more elements or compounds combine to form a single compound is called combination reaction .For example :

  →1)Sodium + Oxygen                       Sodium oxide

  →4Na    `+ O₂                           2Na₂O

  →2)Magnesium + Oxygen                           Magnesium oxide

  →2Mg   +          O₂                               2MgO

  →3)Hydrogen + Chlorine                 Hydrogen chloride

  →H₂   +  Cl₂                                         HCl

  →4)Zinc +Chloride                 Zinc Chloride

  →Zn  + Cl₂                     ZnCl₂

  →5)Nitrogen + Hydrogen                        Ammonia

  →N₂      +     2H₃                       2NH₃

  →6)Iron + Oxygen                 Iron oxide

  →Fe   +  O₂                         Fe₂O₃

  →7)Magnesium +Nitrogen                         Magnesium Nitride

  →3Mg +  N₂                             Mg₃N₂

  →8)Carbon dioxide +Water                                    Carbonic acid

  →  CO₂        +H₂O                     H₂CO₃

  →9)Aluminum + Oxygen                 Aluminum oxide

  →Al  +O₂                          Al₂O₃

  →10)Aluminum + Chlorine                   Aluminum Chloride

  →2Al    + 3Cl₂                        2AlCl₃

  →11)Ammonia +Hydrochloric acid          Ammonium chloride

  →NH₃      + HCl                                     (NH₄)Cl

  →12)Nitrogen +  Oxygen                 Nitric oxide

  →N₂     + O₂                   2NO

  →13)Calcium oxide + Water                       Calcium hydroxide

  →CaO    +  H₂O                       Ca(OH)₂

  →14)Sodium oxide   +Water                     Sodium hydroxide

  →Na₂O  +H₂O                          2Na(OH)

2.)Decomposition  reaction :-The chemical reaction in which a compound split or decompose into two or more elements or compound is called decomposition reaction .For example:

  →1)Water                                Hydrogen   + Oxygen

  →2H₂O                          2H₂     + O₂ 

  →2)Potassium chlorate        Potassium chloride + Oxygen

  →2K(ClO₃)                    2KCl   + 3O₂

  →3)Calcium carbonate         Calcium oxide +Carbon dioxide

  →Ca(CO₃)                                 CaO                + CO₂

  →4)Magnesium oxide                       Magnesium +Oxygen

  →2Mg O                       Mg + O₂

  →5)Hydrogen peroxide                   Water + Oxygen

  →2H₂O₂                                                2H₂O +O₂

  →6)Calcium bicarbonate                 Calcium carbonate +Carbon dioxide +Water

  →Ca(HCO₃)₂                 Ca(CO₃) +CO₂    +H₂O

  →7)Magnesium bicarbonate                      Magnesium carbonate +Carbon dioxide +Water

  →Mg(HCO₃)₂                           Mg(CO₃) +CO₂  +H₂O

  →8)Silver Bromide                Silver  + Bromine

  →2Ag Br                                   2Ag  +Br₂

 

3.Displacement reaction :The chemical reaction in which an element or radical of a compound is displaced by another element or radical of compound is called displacement reaction .For example :

  →1)Zinc +Sulphuric acid                Zinc sulphate +Hydrogen

  →Zn +  H₂(SO₄)                  Zn(SO₄ )  +   H₂

  →2)Zinc  + Hydrochloric acid               Zinc chloride + Hydrogen

  →  Zn       +   2HCl                                ZnCl₂   +  H₂

  →3)Potassium + Nitric acid        Potassium Nitrate +  Hydrogen

  →   2 K  + 2H(NO₃)                 2K(NO₃)    +  H₂

  →3)Iron + Copper Sulphate            Iron Sulphate +Copper

  →2 Fe +3 Cu(SO₄)            Fe₂(SO₄)₃            + 3Cu

  →4)Aluminum  + Hydrochloric acid             Aluminum chloride +Hydrogen

  →2 Al    +6 HCl                                   2AlCl₃  + 3 H₂

  →5)Magnesium + Copper Sulphate            Magnesium Sulphate + Copper

  → Mg + CuSO₄                                         Mg(SO₄)  + Cu

  →6)Sodium + Water                         Sodium hydroxide + Hydrogen

  →2 Na +2H₂O                         2Na(OH) +H₂

 

  →











     

4)Acid –Base reaction :The Chemical reaction in which an acid react with a base to form salt and water is called acid- base reaction .In acid base reaction both acid and base loss their properties during chemical reaction and form neutral substance salt and water ,so it is also called Neutralization reaction .

Some acids :

i)Hydrochloric acid=HCl

ii)Sulphuric acid =H₂(SO₄)

iii)Nitric acid =H(NO₃)

iv)Carbonic acid =H₂(CO₃)

Some bases :

i)Metal oxide ePdf = Mgo,Na₂O,K₂O,CaO etc.

ii)Metal hydroxide ePdf = Na(OH),K(OH),Ca(OH)₂ etc.

  →1)Sodium Hydroxide +Hydrochloric acid        Sodium Chloride + Water

  →2Na(OH)+2HCl                   2NaCl +H₂O

  →2)Sodium Oxide +Hydrochloric acid             Sodium Chloride +Water

  →Na₂O  +2HCl                        2NaCl +H₂O

  →3)Calcium Oxide +Sulphuric acid           Calcium Sulphate +Water

  →CaO +H₂(SO₄)          Ca(SO₄)+H₂O

  →4)Magnesium Oxide +Hydrochloric acid         Magnesium Chloride +Water

  →MgO+2HCl               MgCl₂ +H₂O

5)Potassium Hydroxide + Hydrochloric acid        →       Potassium Chloride +Water

 2K(OH)+2 HCl     →                  2KCl +H₂O 

 

Periodic table :A table in which elements are classified into various blocks ,periods, and groups on the basis of their similarities and dissimilarities is called periodic table .There are two types lines in the periodic table :

i)Group :The vertical columns of periodic table are called groups .The valence electrons of all elements in the same groups are the  same .

 ii)Periods :The horizontal rows of periodic table are called periods .

Advantages of periodic table:

i)it help to remember the properties of elements, if its position in the periodic table is known .

ii)It makes the study of chemistry systematic and easy .

iii)It is used as teaching aids in chemistry in school and college .

A.)Mendeleev`s periodic table : The periodic table in which elements are arranged in the table with the increasing order of their atomic weight is called Mendeleev’s periodic table .It was formed by Demitri Mendeleev’s .

Mendeleev’s periodic law: It states that the physical and chemical properties of elements are periodic functions of their atomic weights .

Modern periodic table :The periodic table in which elements are arranged in the table with the increasing order of their atomic number is called Modern  periodic table .It is also called long form periodic table .It was formed by Henry Moseley.

Modern periodic law: It states that the physical and chemical properties of elements are periodic functions of their atomic number

46.Build an Atom

41.Concentration

37.Acid and base solution

35.Balencing chemical equation

36.Balencing Act

34.PH Scale

30.Reactant and product

29.Molecules and shapes

22.State of matter