NCERT Solutions for Class 6 Science Chapter 6 - Changes Around Us
Chapter 6 - Changes Around Us Exercise 51
Yes, because the folded portion of the dress can be unfolded. It is a reversible physical change.
Physical changes can be reversed but chemical changes cannot be reversed.
Change can be reversed or not
The sawing of a piece of wood
The melting of ice candy
Dissolving sugar in water
The cooking of food
The ripening of a mango
Souring of milk
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.
(i) If we inflate 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 inflating a balloon can be reversed. But, if the balloon bursts after being inflated, 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 chapatti from a ball of dough, the chapatti 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.
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