2. TABLEOFCONTENTS
❏ Introduction.
❏ Chemical equations.
- Writing an chemical equation.
- Balanced chemical equations.
❏ Types of chemical reactions.
- Combination reaction.
- Decomposition reaction.
- Displacement reaction.
- Double displacement reaction.
❏ Oxidation and reduction.
- Oxidising and reducing agent.
- Effects of Redox reaction in everyday life and how to prevent it.
4. WhatisChemistry?
A branch of science
that deals with
matter
WhatisaChemical
reaction?
A process in which one or more
substance is changed or transfered into
a new compound with new chemical
properties. It is also called as
Rearrangement of atoms
Example: Ca +O2 > CaO
Reactants: Ca and O2
Products: CaO
6. EXAMPLES
ChangeinColor
ChangeinState
EvolutionofGas
ChangeinTemperature
The reaction between the
lead nitrate solution and
potassium iodide
solution. In this reaction
the lead Iodide colour
changes from colourless
to yellow
The chemical reaction
between zinc and dilute
sulphuric acid is
characterized by the evolution
of hydrogen gas.
When the wax is burnt
in the form of the wax
candle then water and
carbon dioxide are
formed. Wax is solid,
water is a liquid
whereas carbon
dioxide is a gas.
The action of
dilute sulphuric
acid on zinc:In this
reaction, heat is
evolved.
Pb(NO3)2(aq)+2KI→PbI2(s)+2KNO3(aq
)
Zn (s)+H2SO4 (aq)→ZnSO4 (s)+H2
(g)
7. ACTIVITY:BURNINGOFMAGNESIUMRIBBON
Materials required: 3-4 cm long Magnesium Ribbon, Sandpaper, Watch glass, Pair of tongs
Procedure: Clean a magnesium ribbon about 2 cm long by rubbing it with sandpaper.
Hold it with a pair of tongs. Burn it using a spirit lamp or burner and collect the ash so
formed in a watch-glass. Burn the magnesium ribbon keeping it as far as possible
from your eyes
Observation: The magnesium ribbon burns with a
dazzling white flame and changes into a white
powder. This powder is magnesium oxide.
Reason: It is formed due to the reaction
between magnesium and oxygen present in
the air.
9. WhatisaChemicalequation?
The phenomenon that links the substances
undergoing a chemical reaction
There are two types of chemical reaction:
- Word equation - Symbolic equation
Eg;
- Word Equation:
Zinc + Hydrochloric acid > Zinc Chloride +Hydrogen
- Symbolic Equation:
Zn + 2Hcl > Zncl2 + H2
10. BalancingaChemicalEquation
Hit and Trial Method
Hit and Trial Method
Step I : List the number of atoms of different elements present in the unbalanced
equation
Step II : Start balancing with the compound that contains the maximum number of atoms.
It may be a reactant or a product. In that compound, select the element which has the
maximum number of atoms.
WhytobalanceaChemicalreaction?
Mass can neither be created nor destroyed in a chemical reaction.
That is, the total mass of the elements present in the products of a chemical reaction has to
be equal to the total mass of the elements present in the reactants.
In other words, the number of atoms of each element remains the same, before and after a
chemical reaction. Hence, we need to balance a chemical equation.
Fe+H2O→Fe3O4+H2
11. BalancingaChemicalEquation
Iron (Fe)
Hydrogen (H)
Oxygen (O)
Reactant Product
Balancing
1
2
1
3
2
4
R: x3
P: x4
R: x4
Step III: There are four oxygen atoms on the RHS and only one on the LHS. Then s
balance hydrogen atoms in the partly balanced equation. To equalise the number of
H atoms, make the number of molecules of hydrogen as four on the RHS. To equalise
Fe, we take three atoms of Fe on the LHS.
Hit and Trial Method
BalancedEquation:3Fe+4H2O→Fe3O4+4H2
12. TOMAKETHEEQUATIONSMOREINFORMATIVE
By writing the physical states of substances, a
chemical equation becomes more informative.
● Gaseous state is represented by symbol (g).
● Liquid state is represented by symbol (l).
● Solid state is written by symbol (s).
● Aqueous solution is written by symbol (aq).
● Writing the condition in which reaction takes
place: The condition is generally written above
and/or below the arrow of a chemical equation.
15. COMBINATIONREACTION
When two reactants combine to form a
product it is called a combination reaction
• Calcium oxide reacts vigorously with water
to produce slaked lime (calcium hydroxide)
releasing a large amount of heat
CaO +H2O --------) Ca(OH)2
Calcium hydroxide react slowly with the
carbon dioxide in the air to form a thin layer
of calcium carbonate on the walls Calcium
carbonate is formed after two to three days
of white washing and gives a shiny finish to
the wall.
16.
17. DECOMPOSITIONREACTION
When a product breaks up into its constitutive
reactants the reaction is termed as
decomposition reaction.
2FeSO4 -------) Fe2O3 +SO2 + SO3
In this reaction we can observe that a single
reactant breaks down to give simple product
this is decomposition reaction.
Ferrous sulphate crystals lose water when
heated and the colour of the crystal changes it
then decomposition to ferric oxide Sulphur
dioxide and sulphur trioxide ferric oxide is a
solid while SO2 and SO3 are gases.
18.
19. TYPESOFDECOMPOSITIONREACTIONS
THERMAL
PHOTO
A photodecomposition
reaction is a type of
decomposition reaction
in which the reactant is
broken down to its
constituents by
absorbing energy from
photons.
A thermal decomposition
reaction can be defined
as a decomposition
reaction which is
activated by thermal
energy. In other words, a
thermal decomposition
reaction requires energy
to be supplied to the
reactants in the form of
heat.
ELECTROLYSIS
An electrolytic
decomposition
reaction is a type of
decomposition
reaction in which the
activation energy for
decomposition is
provided in the form of
electrical energy.
01 03
02
O3 + hν → O2 + O.
2H2O→ 2H2 + O2
CaCO3 → CaO + CO2
20. DIFFERENCE
Combination reaction Decomposition reaction
One or more reactants combine to from a single
product.
A single reactant is decomposed to from one or
more products
Energy is released. Energy is absorbed in the form of Heat,
Electricity, and Light
Elements or compounds may be the reactants. Single compound is the reactant
Thus both Decomposition and combination reactions are opposite in nature
21. DISPLACEMENTREACTION
The process in which high reactive substance
displaces or removes the low reactive substance
EXAMPLE
Fe+CuSo4 > FeSo4+Cu
In this reaction; IRON has displaced or removed
another element,
COPPER, from copper sulphate solution.
Zn+CuSo4 > ZnSo4+Cu
Pb+CuCl2 > PbCl2+Cu
In these two reactions; ZINC and LEAD displaced
copper.
22.
23. ACTIVITY:IRONNAILSANDCOPPER SULPHATESOLUTION
Materials Required: Three iron nails, Sand paper, Two test tubes, Copper sulphate solution.
Procedure: Take three iron nails and clean them by rubbing with sandpaper. Take two test
tubes marked as (A) and (B). In each test tube, take about 10 mL copper sulphate solution. Tie
two iron nails with a thread and immerse them carefully in the copper sulphate solution in
test tube B for about 20 minutes. Keep one iron nail aside for comparison. After 20 minutes,
take out the iron nails from the copper sulphate solution.
Observation: The iron nail becomes brownish in colour and
the blue colour of copper sulphate solution fade
Reason: Iron has displaced or removed another element,
copper, from copper sulphate solution. This reaction is known
as displacement reaction.
25. DOUBLEDISPLACEMENTREACTION
The reaction in which there is an exchange of
ions between the reactants
EXAMPLE
Na2So4+ BaCl2 > BaSo4+2NaCl
In this reaction; we can observe that white
substance, which is insoluble in water ; is
formed.
This insoluble substance formed is called as
PRECIPITATE.
CuSo4+2NaOH > Na2So4+Cu(OH)2
Any reaction that produces precipitate can be
called as PRECIPITATION REACTION.
26.
27. DIFFERENCE
Displacement Reaction Double Displacement Reaction
It is a slow reaction. It is a fast reaction.
In this reaction, a change of color takes
place.
In this reaction, precipitate formation
takes place.
28. Endothermic Reaction Exothermic Reaction
The energy is absorbed from the
surrounding into the reaction
The energy is released from the
system to its environment.
Energy in the form of heat Energy is released as heat, electricity,
light or sound.
Melting ice, evaporation, cooking, gas
molecules, photosynthesis are a few
examples
Rusting iron, settling, chemical
bonds, explosions, nuclear fission are
a few examples.
ENDOTHERMICANDEXOTHERMICREACTIONS
29. COMBINATION
● Oxygen combines with carbon
monoxide and forms Carbon
Dioxide.
● magnesium oxide combining with
carbon dioxide to produce
magnesium carbonate.
● iron combining with sulphur to
produce iron(II) sulfide.
DECOMPOSITION
● Manufacture of cement or
calcium oxide.
● For metallurgical processes:
Extraction of metals from their
oxides, chlorides, etc.
● The relief from acid indigestion.
● Thermite welding.
DISPLACEMENT
DOUBLEDISPLACEMENT
● Acid indigestion
● Extraction of metals
● Flame photometry
USES
● Vinegar and baking soda for
a chemical volcano
● Milk with baking powder in
a recipe
● Metathesis reaction
31. OXIDATIONANDREDUCTIONREACTIONS
⚫ If a substance gains oxygen and losses
hydrogen then it is said to be oxidation
reaction.
Example: 2Mg + O2 > 2MgO
⚫ If a substance gains hydrogen and losses
oxygen then it is said to be reduction
reaction.
Example: CuO + H2 > Cu + H2O
34. ACTIVITY:OXIDATIONOFCOPPERTOCOPPEROXIDE
● Heat a china dish
containing about 1g copper
power.
● When copper is heated in
the presence of oxygen, the
surface of copper powder
becomes coated with black
copper oxide.
● This happens because
oxygen is added to copper
and copper oxide is formed.
● Reaction: Cu + O2 > CuO
35. REDOXREACTION
⚫When one reactant gets oxidised while the other gets
reduced during a reaction then we call it as a redox
reaction or it can be called as oxidation-reduction
reaction.
36. EFFECTSOFREDOXREACTIONINEVERYDAYLIFE
RANCIDITY
When fats and oils are oxidised, they become rancid and their smell
and taste change. Prevention: Air tight containers, Refrigeration,
Adding Antioxidants.
For example: butter, cheese, chips etc.
37.
38. RANCIDITYCANBEAVOIDEDBY:
● Adding antioxidants
(substances which prevent
oxidation) to food.
● Storing food in airtight
containers to slow the process
of rancidification.
● Refrigerating food also helps
to slow down rancidification.
● Replacing oxygen in the
containers with another gas.
41. CORROSIONCANBEPREVENTEDBY:
● Use non-corrosive metals, such as
stainless steel or aluminium.
● Make sure the metal surface stays
clean and dry.
● Use drying agents.
● Use a coating or barrier product such
as grease, oil, paint or carbon fibre
coating.
● Lay a layer of backfill, for example
limestone, with underground piping.
