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ROLL NO -16ROJALIN SAHOO

ROLL NO -19

INTRODUCTION

• Can you say few things you can change around you ?

• Did you realise that so many changes are taking place around you all the time?

• Can some of the changes be grouped together?

• Can all the changes always be reversed?

EXPLANATION

• Let us perform some day to day life activities. Take a balloon and blow it. Take care

that it does not burst. The shape and size of the

balloon have now changed. Now let the air escape the balloon.

IMAGE OF BLOWING A BALLOON

Activity - 2

• Now take a piece of paper and fold it. change the shape of the paper into a toy aeroplane . Now you have changed the shape of the paper into a toy aeroplane.

• Now again unfold the paper.

IMAGE OF PAPER AEROPLANE

ACTIVITY- 3

• Now take some dough and make a ball. • Try to roll out a roti.• Now again change it back into a ball of dough

again.

OBSERVING THE THREE ACTIVITIES

• Now think about the three changes you observed in activity 1,2,3.Now tell what do they have in common ?

• Was it possible to get the ballon back to its origional shape and size ?

• Was the size of the paper same as before and after making an aeroplane ?

• Was it possible to get back the ball of dough again ?

CONCLUSION FROM THE THREE ACTIVITIES

• In each of the three activities ,is it possible to get back to the materials with which we strated our activity ?

The answer is yes.It means that the changes ocuuring in these activities can be reversed.

So, the chanes in which we can again get back the origional substanse are called reversible changes.

REPEAT OF THE ACTIVITY-1 WITH A DIFFERENCE

• Now take the same balloon again which you already used in activity 1.

Blow it to its full size and tie its mouth with a string tightly.

Prick it with the pointed tip of your pencil. Then now what is the result . It bursts.

IMAGE OF A BURSTING OF A BALLOON

REPEAT OF ACTIVITY-2

• Take the same piece of paper, which you used in activity 2.Draw an aeroplane on it and cut along its outline.

IMAGE OF CUTTING OF A PAPER

REPEAT OF ACTIVITY- 3

• Now roll out a roti from the ball of dough again and bake it on a tawa .

IMAGE OF BAKING A ROTI

OBSERVATION OF REPEATING ACTIVITIES

• Now tell was it possible to get the ballon back to its origional shape and size ?

• Was the size of the paper Same as before and after making an aeroplane ?

• Was it possible to get back the ball of dough again ?

CONCLUSION OF REPEATING ACTIVITIES

• Now it is sure that all the three repeating activities are not reversed. That is in these changes we can not again get back the origional substances.

So, the changes in which we can not get back the origional substances again are called reversible changes.

ONE OF THE VIDEO INVOLVING REVERSIBLE AND IRREVERSIBLE CHANGES

REVERSIBLE CHANGE

• The changes in which we can again get back the origional substances are called reversible changes.

• EXAMPLES - Boiling of water. Melting of ice. Blowing of ballon. folding of paper.

IRREVERSIBLE CHANGES

• The changes in which we cannot again get back the origional substances are called irreversible changes.

EXAMPLE – Cutting of paper. Bursting of balloon. Making of chapati. Formation of curd from milk.

SUMMARIZATION

• THE CHANGES IN WHICH WE CAN AGAIN GET BACK THE ORIGIONAL SUBSTANCES ARE CALLED REVERSIBLE CHANGES.

• THE CHANGES IN WHICH WE CANNOT AGAIN GET BACK THE ORIGIONAL SUBSTANCES ARE CALLED IRREVERSIBLE CHANGES.

EVALUATIONA drawing sheet changes when you

draw a picture on it . Can you reverse this change ?

You accidentaly dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed ?

To walk through a waterlogged area , you usually shorten the length of your dress by folding it. Can this change be reversed ?

Which of the following is a reversible change

a) Bursting of balloonb) Burning of paperc) Blowing of balloond) Rusting of Iron

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Which of the following is a irreversible change

a)Blowing of balloon b) Melting of Ice c)Boiling of Water d)Cutting of paper

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