Basics of Chemical Equations and Reactions Video Lecture - Class 10

Hello students today
we will study chemical reaction and equations
first question which comes into the mind is
what the chemical reaction is all about ? before
answering the question,
I would like you to think what happen when
food is cooked
what happen, when candle wax burns
what happen when souring of milk occurs
what happen when you think !
and thing that he would had find is that final
substance differs from original
substance
either physically or chemically.
so we can say that chemical reaction is the
formation of new substance
which differs in properties of original substance
either physically or chemically.
what is change in physical properties ? change
in physical properties includes
change in color, change in physical state
which means substance has changed the state
from solid to liquid,
liquid to gas, or vice-versa.
next one is, change in odour and change in
temperature
if any of these change occurs we can say
that chemical reaction has taken place.
and chemical properties includes,change in
heat of combustion which means,
change in amount of heat required for combustion
or burning
change in reactivity of the substance, and
change in pH value of the substance
if any of these chemical changes occur we
assume that
chemical reaction has taken place.
now,the next topic is how to represent a chemical
reaction
there are two ways of representation of chemical
reaction
one is word equation another is chemical equation
To explain word equation and chemical equation
let us do an activity,of burning magnesium
ribbon in presence of oxygen,
the ash collected during this process is magnesium
oxide
if we write this process like when magnesium
ribbon is burnt in presence of
oxygen
it converted into magnesium oxide this is
sentence form of the process
and but, if we want to make it short
we can write into Words like magnesium plus
oxygen we get magnesium oxide
when magnesium and oxygen are reactants and
magnesium oxide is product
Here,
arrow shows the direction of the word equation
now is there any more shorter way of representation?
Answer is yes, the other way is writing chemical
equation
in which he writes chemical symbol inspite
of writing full words
so,
if we write the same process and chemical
equation
it would be mg which is chemical symbol of
magnesium plus 02 which is oxygen
here
02 is written because oxygen can not exist
in single atom state
since it is highly reactive element and that
results in to the formation of
magnesium oxide
here 2mg0 is written is, as to balance atom
on both sides, now we come to the types of
chemical reaction
combination reaction
decomposition reaction, displacement reaction
double displacement reaction and oxidation-reduction
reaction
now we take them one by one,
combination reaction are those reactions in
which two reactants combine to form
one product.
like here in this general reaction two reactants
A & B combine
to give product AB example if this type of
reaction is the one which we
have learnt earlier
the burning of magnesium ribbon in presence
of oxygen
which gives magnesium oxide.
next is decomposed reactions
decompose reactions are those reactions
in which one substance or one compound is
decomposed into or more
substances or compounds example if this type
of reaction is
when you heat calcium carbonate which is usually
available worldwide,
mostly you find it in rocks pearls,
so when you heat it. it decomposes into calcium
oxide
which is in solid form and carbon dioxide
which is in gas form.
Displacement reactions are those reactions
in which
atom moves from one compound to another compound
to form a new compound.Like in this general
displacement
reaction atom C moves from compound BC to
compound A
to form new compound AC, it is only possible
when A is more reactive than
B if it is not,it would have not gone to
B to form new compound, Example if this type
of reaction is
when zinc reacts with hydrochloric acid
giving zinc chloride and hydrogen gas.
zinc chloride is useful in chemical synthesis
and textile processing.
double displacement reactions are those reactions
in which atoms are exchanged between two reactants
and form two new compounds. when sodium hydroxide
reacts with
hydrochloric acid
forms sodium chloride which is sold
In this reaction chloride ion which is negative
and
combine with sodium ion which is more positive
ion than hydrogen-ion
now we come to oxidation reduction reactions,
these are also called redox reaction
as too half words of reduction and oxidation
are combined with each other
they complement to each other this is because
in redox reaction if there is reduction then
there would be oxidation as well
reduction cannot be done without oxidation
and vice versa.Let us see what is oxidation
if there is additional oxygen or removal of
hydrogen element
reaction is called oxidation reaction.
Reduction is just reverse. if there is additional
hydrogen element
or removal of oxygen element from compound,
reaction is called reduction
Now, let us take an example
Radox reaction.In this example there is reduction
of copper oxide,
as oxygen is removing from it and oxidation
of hydrogen,
as oxygen is adding to it. I hope
you would have learnt from this video please
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