NCERT Solutions for Class 6 Science Changes around Us [Old Book]

NCERT
SOLUTIONS
CLASS - 6TH

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Class : 6th
Subject : Science
Chapter : 6
Chapter Name : Changes Around Us

Q1 To walk through a waterlogged area, you usually shorten the length of your dress by folding it.
Can this change be reversed?

Answer. Yes. The length of the dress can again be increased by unfolding it. Hence, this change can
be reversed.

Q2 You accidentally drop your favourite toy and break it. This is a change you did not want. Can
this change be reversed?

Answer. No. This change cannot be reversed.

Q3 Some changes are listed in the following table. For each change, write in the blank column
whether the change can be reversed or not.

Answer.

Q4 A drawing sheet changes when you draw a picture on it. Can you reverse this change?

Answer. If we draw a picture on a drawing sheet with a pencil, we can get back the original drawing
sheet by erasing the drawing with an eraser. In this case, the change can be reversed. However, if
we draw with a pen, then the original drawing sheet cannot be obtained back because we cannot
erase ink. Hence, in this case, the change cannot be reversed.

Q5 Give examples to explain the differences between changes that can or cannot be reversed.

Answer. To explain the differences between changes that can or cannot be reversed, some
examples are given below:
(i) If we in ate a balloon, the size and shape of the balloon undergoes a change. However, the
original size and shape of the balloon can be obtained back by allowing the air to escape from the
balloon. This means that the change that occurs by in ating a balloon can be reversed. But, if the
balloon bursts after being in ated, then its original size and shape cannot be obtained back. Thus,
in this case, the change cannot be reversed.
(ii) If we fold a piece of paper, then the shape and size of the paper undergoes a change. In this
case, the original shape and size of the original paper can be obtained back. Thus, this change can
be reversed. However, if we cut the piece of paper, the change in the shape and size of the paper
cannot be reversed.
(iii) After we roll out a chapati from a ball of dough, the chapati can be converted back into a ball.
Thus, the change occurring here can be reversed. But, if we cook the chapatti on a tawa, then it
cannot be converted back into a ball of dough. Thus, the change is irreversible.

Q6 A thick coating of Plaster of Paris (POP) paste is applied over the bandage on a fractured bone.
It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be
reversed?

Answer. When water is added to plaster of Paris (POP), it changes to another substance and on
drying it hardens. Once the POP has hardened, its shape cannot be changed. Therefore, the
change in POP cannot be reversed.

Q7 A bag of cement lying in the open gets wet due to rain during the night. The next day, the sun
shines brightly. Do you think the changes that have occurred in the cement can be reversed?

Answer. In this case, the changes cannot be reversed. This is because the cement that hardens up
after getting wet cannot be obtained back.