CHEMICAL REACTIONS
AND EQUATIONS
In
our surroundings we find two types of changes
1)
Physical Change
2)
Chemical Change
When
the chemical change occurs, chemical reaction takes place.
Q. Which factors help us
to determine the chemical reaction?
·
Change
in state
·
Change
in colour
·
Evolution
of gas
·
Change
in temperature
Q. Which are the methods
of representing chemical reactions?
·
Descriptive
method
The entire chemical reaction is described
in words in long sentences.
·
Word
– equation method
Chemical reaction is described using
names of the substance.
·
Chemical
equation
Chemical reaction is represented by
using the symbols and formulae of the reactants and products.
Q. What are the reactants
and the products?
·
Reactants
– The substances entering the chemical reaction are called as ‘Reactants’.
·
Products
– The new substances formed in the chemical reaction are called as ‘Products’.
Q. What is balanced
chemical equation?
Chemical
reaction in which the number of atoms of each element on the reactant side is
equal to the number of atoms of the same element on the product side are called
as Balanced Chemical Equation. (This is based on Law of Conservation of Mass)
There
is no particular method to balance the given chemical equation.
We
do it by Hit and Trial Method.
(Explained
in my YouTube tutorial – how to balance chemical equation (VrushuRaj classes)
Q. Which are the
different types of Chemical Reactions?
combine together to form a single product.
CaO(s) + H2O(l) à
Ca(OH)2(aq)
Quick lime Slaked lime
Calcium
Hydroxide (Slaked Lime) is used for white washing.
Ca(OH)2(aq) + CO2(g) à CaCO3(s) + H2O(l)
Calcium hydroxide calcium carbonate
Chemical Decomposition – A reaction in
which one substance breaks down to form two or more products.
FeSO4(s) à Fe2O3(s) + SO2(g) + SO3(g)
Electrolysis – When
decomposition is carried out with the help of electric current, the process is
called as “Electrolysis”.
Electrolysis of
water
2H2O(l) à
2H2(g) + O2(g)
Chemical Displacement – A reaction in which more active
element displaces the less active element from a compound.
Fe(s) + CuSO4(aq) à FeSO4(aq) +
Cu(s)
Copper sulphate Iron sulphate
Chemical Double Displacement (Double
Decomposition)
– A reaction in which
two compounds react to form two new compounds by mutual
exchange of
radicals.
Na2SO4(aq) + BaCl2(aq) à BaSO4(s) +
2NaCl(aq)
Q. Difference between
Exothermic and Endothermic Reactions
EXOTHERMIC REACTION
|
ENDOTHERMIC REACTION
|
The
reactions in which heat is released along with the formation of the products
are called “Exothermic Reactions”.
Egs.
Burning of natural gas
CH4(g) + O2(g) à
CO2(g) + H2O(g)
|
The
reactions in which energy is absorbed are called “Endothermic Reactions”.
Egs.
2AgCl(s) à
2Ag(s) + Cl2(g)
|
Q. Explain Oxidation and
Reduction reactions
OXIDATION
|
REDUCTON
|
If
a substance gains oxygen (or loses hydrogen) in the reaction, it is said to
be Oxidised.
|
If
a substance loses oxygen (or gains hydrogen) in the reaction, it is said to
be Reduced.
|
Q. What is Redox
reaction?
In
a chemical reaction if one substance is oxidised and one is reduced then such
reaction is called Oxidation-Reduction or Redox reaction.
CuO
+ H2 à Cu
+ H2O
Here, copper oxide is reduced and hydrogen is
oxidised.
Q. Define Corrosion
When
a substance is attacked by moisture, acids, etc. It gets corrodes and the
process is called Corrosion.
Egs.
Black coating on silver, green coating on copper.
Q. Define Rancidity
Rancidity
is the process of slow oxidation of oil or fat present in the food materials
which results in foul odour and taste.
Preventive measures
·
Pack
food material in an air tight container
·
Refrigerate
cooked food at low temperature.
Q. Define Antioxidants
These
substances are added to the fatty and oily substances to avoid its oxidation.
Egs.
Chips bags are filled with nitrogen to avoid oxidation of chips.
for the video of this lesson click the given link :
chemcial reaction (part 1) - https://youtu.be/WCAXsNXIMYc
chemical reaction (part 2) - https://youtu.be/KCWnVfGnoWY
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