NCERT Solutions for Class 6 Science Chapter 6 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 :

(1) Yes, this change can be reversed by unfolding the dress.

(2) The way we folded the dress and made the dress smaller, the same way the dress can be opened and enlarged.

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

Answer :

(1) No, this change cannot be reversed.

(2) Because breaking of a toy is an irreversible change, one cannot regain the same toy.

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 :

1)\(\space \) The sawing of a piece of wood \(\rightarrow \)NO

2)\(\space \)The melting of ice candy \(\rightarrow \)YES

3) \(\space \)Dissolving sugar in water.\(\rightarrow \)YES

4)\(\space \)The cooking of food \(\rightarrow \)NO

5)\(\space \) The ripening of a mango\(\rightarrow \)NO

6)\(\space \)Souring of milk \(\rightarrow \)NO

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

Answer :

(1) If the drawing is made with a pencil then it can be erased and we will get the original sheet back. So, we can reverse the change.

(2) But if a pen, paint, oil /watercolors are used to draw the picture, change cannot be reversed.

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

Answer :

(A) Changes that can be reversed:

(I) Writing with a pencil.

(II) Switching on or off of the fan.

(III) Making ice from water.

(IV) Inflating a balloon


(B) Changes then can not be reversed:

(I) Writing with a pen.

(II) Making curd from milk.

(III) Burning of paper.

(IV) Ripening of fruit

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

Answer :

(1) No, this change cannot be reversed because getting it back is an irreversible change or a chemical change.

(2) The plaster of Paris on getting mixed with water changes into a hard mass and form a new compound.

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, which have occurred in the cement, could be reversed?

Answer :

(1) No, it can not be reversed. It is an irreversible change or chemical change.

(2) When the water is mixed with the cement, it becomes hard and the change cannot be reversed.