Class 6th Science Ch 6 Changes Around Us Written Work

 Exercise Questions

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

Solution :

Sl NoChangeCan be reversed Yes/No
1The sawing of a piece of woodNo
2The melting of ice candyYes
3Dissolving sugar in waterYes
4The cooking of foodNo
5The ripening of a mangoNo
6Souring of milkNo

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


Some Important Questions

Question 1
What are the differences between reversible changes and irreversible changes?
Answer:
The differences between reversible changes and irreversible changes:

Reversible changesIrreversible changes
1.   A change which can be undone or reversed.

2.   It is a temporary change.

3.   Melting and folding are examples of it.

1.  A change which cannot be undone or reversed.

2.  It is a permanent change.

3.  Burning and cooking of food are examples of it.

Question 2
Can you obtain wood from sawdust?
Answer:
No, because it is an irreversible change.

Question 3
Can we say that ironing of a cloth is a reversible change? Give reasons.
Answer:
Ironing removes the wrinkles of the clothes, which can come back in the same condition. Hence, ironing of a cloth is a reversible change.

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