SOLUTIONS OF BACK EXERCISE, Chapter 6 Changes Around us

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

Solution:

Yes, the process can be reversed.

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

Solution:

No, this change cannot be reversed

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

Sl No	Change	Can be reversed Yes/No
1	The sawing of a piece of wood
2	The melting of ice candy
3	Dissolving sugar in water
4	The cooking of food
5	The ripening of a mango
6	Souring of milk

Solution :

Sl No	Change	Can be reversed Yes/No
1	The sawing of a piece of wood	No
2	The melting of ice candy	Yes
3	Dissolving sugar in water	Yes
4	The cooking of food	No
5	The ripening of a mango	No
6	Souring of milk	No

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

Solution:

This change can be reversed if a pencil is used to draw the picture. If a pen, paint, oil /water colours are used to draw the picture, change cannot be reversed.

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

Solution:

Changes that can be reversed

i) Opening and closing the door

ii) Filling glass with water

Changes that cannot be reversed

i) Conversion of milk into curd

ii) Ripening of fruit

6. 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 immobilized. Can the change in POP be reversed?

Solution:

No, the change cannot be reversed

7. 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?

Solution: No, the change cannot be reversed