Topic outline

    • Changes Around Us

      Q1. Write two examples of slow changes.

      Ans. Germination of seed and ripening of fruits


      Q2. Write two examples of fast changes.

      Ans. Bursting of crackers and Burning of paper


      Q3. Is it possible to obtain wood from sawdust?

      Ans. No, because it is an irreversible change.


      Q4. Does the shape of the eraser changes when it is used repetitively?

      Ans. Yes, the shape of the eraser changes when it is used repetitively.


      Q5. Think of some changes that happen in our body.

      Ans. Growth of nails, growth of hair, increase in height, increase in weight etc.

      Q6. A small size boat is made by folding a paper. Can this change be reversed? Think and write one more example of similar type.

      Ans. Yes, it can be reversed. Another example is ball made by folding paper.


      Q7. Your brother accidently dropped your favorite pencil box and broke it. This is a change you did not want. Can you reverse this change?

      Ans. No, this change is not reversible as broken pieces cannot be fixed.


      Q8. How candles of different shape are made?

      Ans. Molten wax is poured in desired mold and a wick is placed in it. Then it is cooled. This is how we get candles of different shape.


      Q9. What is reversible change?

      Ans. The changes in which we can bring back the products to original form without creating any new substance are known as reversible changes.


      Q10. Is cutting down of a tree is reversible change?

      Ans. No, cutting down of tree cannot be consider as a reversible change because same tree can be planted again after cutting.


      Q11. Is printing of book is a reversible or an irreversible change?

      Ans. Printing is an irreversible change because ink and paper cannot be separated once printing is done.


      Q12. Write two examples each of reversible and irreversible changes.

      Ans. Reversible Change – melting of ice and stretching of rubber band

      Irreversible change – Burning of leaves and Souring of milk

      Q13. You made a picture on a blank sheet and colored it. Can you reverse this change? If not, why?

      Ans. No, this change cannot be reversed as we cannot get fresh blank sheet once a picture is drawn and colored.


      Q14. Explosion of a cracker is an irreversible change. How?

      Ans. Explosion of a cracker is an irreversible change because once crackers are burnt, they cannot be converted back to its original form.


    • Download to practice offline.