Chemical substances and process final1

CHAPTER - 1
CHEMICAL SUBSTANCES
AND PROCESSES
CLASS :- VII
MADE BY :- RAVI PRAKASH SINGH
SUBJECT :- CHEMISTRY
Friday, December 1, 2017RAVI PRAKASH SINGH 1

MATTER
Matter exist in three states :-
• Solid
• Liquid
• Gas
ATOM
All matter is made up of smallest particles called atom.
Ex- Hydrogen atom, Oxygen atom, Nitrogen atom
CHEMICAL SUBSTANCES AND PROCESS

MOLECULES
When two or more atoms combine together
chemically is called molecules
Diatomic molecules are made of two atoms
of the same element.
Ex- Hydrogen – H2, Oxygen – O2

PURE SUBSTANCES
Sample of the
Element Lead
Sample of the
Element Chlorine
Materials made up of same kind of atoms or molecules are called Pure Substances.
Pure Substances is classified into ELEMENT or COMPOUND
ELEMENTS
Pure Substances which is made up of same types of atoms are called Element.
It Cannot be broken down by physical and chemical methods
Examples: Oxygen, Nitrogen, Carbon

COMPOUNDS
Friday, December 1,
RAVI PRAKASH SINGH 5
 Compound are substances made of two or more different kinds of elements
chemically combined in a specific ratio.
H2O – ratio of Hydrogen is 2:1 Oxygen
 Compound is made up of same types of molecules
Compound Can be separated only by chemical methods
Properties of a compound are totally different than the properties of the
elements that form them
Examples: Water, Carbon dioxide, Sugar
A formula is just chemical shorthand for the compound.
The subscript lets us know how many atoms are present.
The coefficient lets us know how many molecules or moles are present.

Compounds

MIXTURE
 Material which contains two or more Substances
mixed in any proportion are called MIXTURE.
 Mixture can be homogeneous or heterogeneous
 Mixture can be separated by physical methods
 Properties of a mixture are related to its
components
 Mixture composition varies from sample to sample
 Examples of Mixtures: Tea, Perfume, Air, Salad,
Beach sand, oil and vinegar salad dressing, etc.

Mixtures
Friday, December 1,RAVI PRAKASH SINGH
8
Mixture of
Different Elements
Mixture of Different
Compounds

Distinguishing between Elements,
Compounds, and Mixtures

CHEMICAL SYMBOLS
Name of element Symbol Atomic No. atomic mass
Hydrogen H 1 1
Helium He 2 4
Lithium Li 3 7
Beryllium Be 4 9
Boron B 5 11
Carbon C 6 12
Nitrogen N 7 14
Oxygen O 8 16
Fluorine F 9 19
Neon Ne 10 20
Sodium Na 11 23
Magnesium Mg 12 24
Aluminium Al 13 27
Silicon Si 14 28
Phosphorous P 15 31
Name of element symbol Atomic No. atomic mass
Sulfur S 16 32
Chlorine Cl 17 35
Argon Ar 18 39
Potassium K 19 39
Calcium Ca 20 40
Scandium Sc 21 45
Titanium Ti 22 46
Vanadium V 23 51
chromium Cr 24 52
Manganese Mn 25 55
Iron Fe 26 56
Cobalt Co 27 59
Nickel Ni 28 59
Copper Cu 29 63
Zinc Zn 30 65

Name of element Symbol Atomic No.
BROMINE Br 35
SILVER Ag 47
MERCURY Hg 48
TIN Sn 50
IODINE I 53
GOLD Au 79
LEAD Pb 80

PERIODIC TABLE

SYMBOL OF COMMON IONS
NAME OF CATIONS SYMBOL
SODIUM Na+
MAGNESIUM Mg2+
ALUMINIUM Al3+
CALCIUM Ca2+
HYDROGEN H+
COPPER Cu2+
IRON Fe2+
ZINC Zn2+
AMMONIUM NH4
+
LITHIUM Li+
POTASSIUM K+
NAME OF ANIONS SYMBOL
CHLORIDE Cl-
BROMIDE Br-
IODIDE I-
FLORIDE F-
OXIDE O2-
HYDROXIDE OH-
CARBONATE CO3
2-
SULPHATE SO4
2-
NITRATE NO3
-
ACETATE CH3COO-
PHOSPHATE PO4
3-

CHEMICAL FORMULA indicates the types & number of atoms (composition) of
each kind present in that substance.
IN CHEMICAL FORMULA , the symbols of all the elements and the number of
atoms of each element is written as a subscript to the right side of its symbol.
The chemical formula of water is H2O.(2 atom of hydrogen + 1 atom of oxygen)
Similarly, the formula of carbon dioxide is CO2. (1 atom of carbon + 2 atom of
oxygen)
CATIONS :- Positively Charged Atoms i.e. Na
+
ANIONS :- Negatively Charged Atoms i.e. Cl
-
CHEMICAL FORMULA

Writing chemical Formulas of Substances
Steps 1-
• 1st word = CATION Symbol (positive ion)
• 2nd word = ANION Symbol (negative ion)
Steps 2-
Their charge is written on the top right corner of symbol
Steps 3-
Remove common factor in charge (if any present)
Steps 4-
Charges of two ions are criss-crossed
Steps 5-
Criss-crossed numbers are now written at bottom right (as
subscript) of symbols of ions.

Writing chemical Formulas of Substances

Chemical Reactions
PHYSICAL CHANGE are the change in physical state of substances i.e.
shape, size, or color. It does not change into another substances.
CHEMICAL CHANGE are the change in which substances changes into
another new substances.
 A CHEMICAL REACTION is a process by which one substance is
transformed into a new substance.
 REACTANTS – the substances that exist before a chemical reaction
(or the substances which undergo a chemical change in reaction).
 PRODUCTS – the new substances that are formed during the chemical
changes.
 CHEMICAL EQUATION indicates the reactants and products of a reaction.
REACTANTS  PRODUCTS
Friday, December 1,

CHEMICAL EQUATION
CHEMICAL EQUATION are the representation of a chemical reaction using symbols
and formulae of substances involved in the reaction
Or A CHEMICAL EQUATION is a symbolic representation of a chemical reaction.
EX- The burning of methane gas in oxygen is:
CH4 + 2 O2 → CO2 + 2 H2O
In chemical equation, Symbols of reactants are written on left hand side and
Symbols of products are written on right hand side & arrow is put between them
General form: Reactants  Products
Example : Formation of Water
Skeletal equation H2 + O2  H2O
Balanced equation . H2 + O2  2H2O

Signs of Chemical Reactions
Friday, December 1,
2017RAVI PRAKASH SINGH 20
These are signs that indicate a chemical reaction has taken place:
change in color change in odor production of new
gases or vapor
input or release
of energy
difficult to reverse
release
input
Formation of a
precipitate

Symbols used in Chemical Equations
Friday, December 1,
RAVI PRAKASH SINGH
22
Symbol Purpose
+ Separates more than one reactant or
product
 Separates reactants from products.
Indicates direction of reaction
(s) Identifies a solid state
(aq) Identifies that something is dissolved
in water
(l) Identifies liquid state
(g) Identifies gaseous state

BALANCED & UNBALANCED CHEMICAL EQUATION
AN EQUATION IN WHICH THE NUMBER OF ATOMS and the total
charge OF EACH ELEMENT ARE EQUAL ON BOTH SIDES OF THE
EQUATION IS CALLED A BALANCED CHEMICAL EQUATION.
In other words, the mass and the charge are balanced on
both sides of the reaction.
Friday, December 1,
IF THE NUMBER OF ATOMS OF EACH
ELEMENT ARE NOT EQUAL ON BOTH THE
SIDES OF THE EQUATION THEN IT IS
CALLED UNBALANCED OR SKELETAL
EQUATION.

Chemical Equations
Because of the principle of the conservation of matter,
an equation must be balanced.
It must have the same number of atoms of the same kind on both sides.
The Law of Conservation of Matter
Chemical
Factory
100% 100%
80%
20%
Lavoisier, 1788

BALANCING CHEMICAL EQUATIONS
To balance chemical equation, number of atoms of various element on both side of the equation
is balanced by writing a suitable coefficient (number) before the formula of that substances but
chemical formula of substance is not changed.
Example: Reaction between hydrogen & oxygen gas gives water.
Steps1: Write chemical formula of reaction.
hydrogen + oxygen  water
H2(g) + O2(g)  H2O(g)
In reactant H atom =2 and O atom = 2
In product H atom =2 and O atom = 1
Steps2 : Find the number of atoms for each element on both side.
Determine where to place coefficients in front of formulas in order to balance the equation.
Number of atom of oxygen is different on both side. So balance it by writing coefficient 2
before H2O in product.
H2(g) + O2(g)  2 H2O(g)
In reactant H atom = 2 and O atom = 2
In product H atom = 4 and O atom = 2
Steps2 : Number of atom of hydrogen is different on both side. So balance it by writing coefficient 2
before H2 in reactant.
2 H2(g) + O2(g)  2 H2O(g)
Now equation is balanced as number of atoms of various element on both side of the equation are equal.

Cl
Cl
Cl
H
H
H
ClClCl
Cl HH
H
H
H2 + Cl2  HCl H2 + Cl2  2 HCl
reactants products
H
Cl
reactants products
H
Cl
2
2
2 2
2 2
1
1
(unbalanced) (balanced)
Unbalanced and Balanced Equations

CH4 + 2 O2  CO2 + 2 H2O
Friday, December 1,
Reactants Products
1 C atom 1 C atom
4 H atoms 4 H atoms
4 O atoms 4 O atoms

BALANCING CHEMICAL EQUATIONS
Balance the following equations:
(a) P2O5(s) + H2O(l)  H3PO4 (aq)
Answer: P2O5(s) + 3H2O(l)  2H3PO4 (aq)
(b) NO2(g) + H2(g)  NH3(g) + H2O(g)
Answer: NO2(g) + 3 ½ H2(g)  NH3(g) + 2H2O(g)
(c) SO2(g) + O2(g)  SO3(g)
Answer: 2SO2(g) + O2(g)  2SO3(g)
(d) CH4 + O2  CO2 + H2O
Answer: CH4 + 2 O2  CO2 + 2 H2O
Questions -

BALANCED CHEMICAL EQUATION
Friday, December 1,
Fe2O3 + C → Fe + CO2
Answer: 2 Fe2O3(s) + 3 C(s) → 4 Fe(s) + 3 CO2(g)
Al(s) + O2(g) → Al2O3(s)
Answer: 4 Al(s) + 3 O2(g) → 2 Al2O3(s)
H2SO4 + NAOH  Na2SO4 + H2O
Answer: H2SO4 + 2 NAOH → Na2SO4 + 2 H2O
Na (s) + Cl2 (g)  NaCl
Answer: 2Na (s) + Cl2 (g)  2NaCl
Na + O2 → Na2O
Answer: 2Na + O2 → Na2O
Al2(SO4)3 + CaCl2  CaSO4 + AlCl3
Answer: Al2(SO4)3 + 3 CaCl2  3 CaSO4 + 2 AlCl3

Types of Chemical Reactions
1. Combination reaction
2. Decomposition reaction
3. Single-displacement reaction
4. Double-displacement reaction
A + B  AB
AB  A + B
A + BC  AC + B
AB + CD  AD + CB
Acid + Base  Salt + Water5. Neutralisation Reaction

 Reactions in which two reactants combine to form one
or more products is called Combination Reaction.
 E.g. –
1. CaO + H2O  Ca(OH)2
2. C + O2  CO2
3. 2H2(g) + O2(g)  2H2O(g)
4. N2(g) + 3H2(g)  2NH3(g)
5. 2Mg(S) + O2(g)  2MgO(s)
 They are generally exothermic reactions which
involve evolution of heat during reaction.

Combination Reaction
Friday, December 1,
General form: A + B  AB
element or element or compound
compound compound
Na
ClNa
Cl
2 Na + Cl2  2 NaCl

ClNa
Na
Cl

Decomposition Reaction
• Reaction in which a single reactant breaks down to give more than one products
are called Decomposition Reaction.
• Or Reaction where a more complex molecule breaks down to form two or more
simpler product is called Decomposition Reaction.
• The general equation is
• E.g.-
2 H2O  2 H2 + O2
CaCO3(s)  CaO(s) + CO2(g)
• When a decomposition reaction is carried out by heating, it is known as thermal
decomposition.
Friday, December 1,
AB  A + B
compound two or more elements or compounds

H
H
H
H
Decomposition Reaction
Friday, December 1,RAVI PRAKASH SINGH 36
H
H
H
H
O
Decomposition reaction
2 H2O  2 H2 + O2
+
OO
O

H2O H2 + O2
electricity
Decomposition Reactions
H2O2 H2O + O2
NI3 N2 + I2
2 2
Hydrogen Peroxide
Electrolysis of water
2 2
Nitrogen trioxide
AB A + B
General Form
2 3

DISPLACEMENT REACTIONS
• The reaction in which a more reactive
element displaces a less reactive element
from its compound (solution) is known as
displacement reaction.

DISPLACEMENT REACTIONS
They are of two types:-
 SINGLE DISPLACEMENT REACTION
General Form : AB + C  A + BC
EXAMPLE Zn + H2S  H2 + ZnS (zinc displaces Hydrogen)
Fe(s) + CuSO4(aq)  FeSO4(aq) + Cu(s)
 DOUBLE DISPLACEMENT REACTION
General Form : AB + CD  AC + BD
EXAMPLE PbCl2 (aq) + KI (aq)  KCL (aq) + PbI2(aq)

PbI2
K1+Pb2+
lead (II) chloride + potassium iodide
Cl2 I
Pb2+
Pb
K1+
K
Cl1- I1-
Cl1- I1-
KCl
potassium chloride lead (II) iodide+
(aq) (ppt)+ +
Friday, December 1,
2017

Ca
Foiled again –
Aluminum loses to Calcium
Element Reactivity
Friday, December 1,RAVI PRAKASH SINGH 41

NEUTRALISATION REACTION
• The reaction in which an Acid and a Base react to from
Water and Salt is known as Neutralisation Reaction.
• General formula :
Acid + Base  Salt + Water
• It involves the combination of H+ ions and OH- ions to
generate Water
• Example –
NaOH(aq)+ HCl(aq)  NaCl(aq) + H2O(l)
Mg(OH)2(aq) + H2SO4(aq)  MgSO4(aq) + 2H2O(l)

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