What are Reversible and Irreversible Changes? Video Lecture - Class 6

hello friends this video on changes
around us part two is brought to you by
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it's now the question is there are many
different types of changes for example
some changes might cause a change in
shape for example when in tear a paper
into four pieces so what happens the
shape changes because the shape of each
piece is very much different from the
original piece of paper so there is a
change in shape sometimes there is a
change in form for example the chocolate
until it got melted before that it was
like solid but now when it is small and
it is a semi liquid so sometimes there
is a change in form sometimes there is a
change in style
you also see a change in form here also
for example when you put water inside
the refrigerator and it inside the deep
filter deep freezer
what happens after some time ice cubes
are formed so it would fall from the
same water so whatever something which
was solid now ice cubes or something
which are whatever something which was
liquid and now ice cubes or something
which are solid so a change has taken
place but here the change has taken in
the form so I did it was liquid now it
is solid so when any if you boil water
what will happen what you vapor will
before
so here again liquid is getting changed
to vapor but here also there is a change
that is involved so this is example of
change of state so here this teeth is
changing so change of stick so that
means solid to liquid liquid to gas
those kind of changes are involved when
you talk about this tearing the paper so
here change in shape and size are
involved now when you take an example
like this where you have you take a
beaker and inside the beaker you put
some copper sulphate solution so let's
say we have copper sulphate solution in
the beaker and inside this vehicle if
you put up a bath of magnesium so this
white thing which you see here is
magnesium what happens
sometimes we see that the blue color of
the copper sulfate changes to white
color so now the color has changed to
white while the color change that's
because when we have put this magnesium
into the copper sulphate solution so
there is a chemical reaction that is
taking place so basically the magnesium
bar reacts with the copper sulphate
solution and it forms magnesium sulfate
and copper as a result what happens is
the color of the solution earlier was
blue now the color of the solution
becomes colorless because magnesium
sulfate is colorless initially the color
of the bar was right it is colorless but
now it changes to copper color which is
blue so now you say the color of the bar
is change to blue and the color of the
solution has changed to Cullen's now
please do not bother yourself with these
chemical equations because I am just
trying to tell you that how changes
happen so in a lot of changes chemical
reactions take place inside because of
which some new substances are formed and
you do which we observe a difference in
the appearance or shape or size or state
and that's how we see that a change has
taken place so whenever there is a
change that means a change has occurred
either it's a shape or size or color or
texture or state so one of these
parameters must have undergone a change
now when we talk about types of changes
so at this level we are going to talk
about two categories of changes certain
changes which are reversible that is you
can reverse them so you start with some
original substance or maybe some initial
substance you start with an initial
substance and after some time it
undergoes a change so you get something
new or something different so that is
the changed product but it is also
possible to get back the original
substance from the change substance
let's say you you got a haircut so what
was the initial state when you had long
hair now after you took a heifer you
have short hair so short hair is the
final
and long is the initial state so when I
am saying that a change is reversible
that means that the short hair again can
be reversed back to long hair that is
the short hair can even give rise to
login so that would be an example of
reversible change now when you talk
about heat a percival change that means
in this type of change the in from the
initial state you will go to the final
state only then you say that a change
has taken place but it is not possible
to come back to the initial state again
that is let's say you have something
like this let's say you have a piece of
paper and you burn it now when you burn
that piece of paper what is the result
so your initial thing was the paper
right so paper was your initial
substance now after you burn it what do
you get after it is burnt completely you
get ashes now can you get back the paper
from the ashes you can't so that means
that as an example of irreversible
change but let me give you an example of
reversible change let's say you have the
same piece of paper and in this case
what you do is you fold that piece of
paper to make a paper plane or a paper
board so you just hold the paper make
curves and that's how you create a paper
coat now can you get back the paper from
the paper boat yes if you just unfold it
you will again get back the same sheet
of paper so this would be an example of
reversible change so getting a paper
boat from paper is reversible change but
burning the paper into ashes is an
irreversible change so that is the main
difference between reversible and
irreversible change so now what we are
going to do is we are going to keep
unload and lot of examples from around
us and we are going to analyze whether
that change is a reversible change or an
irreversible change thank you please
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