Q14 of 20 Page 34

Tearing of paper is said to change that cannot be reversed.

What about paper recycling?

In paper recycling, the old, waste paper is used to make a new type of paper. In this, the original form, shape, size, and texture of paper are replaced by new shape, size and texture. Therefore, tearing of paper remains a change which cannot be reversed, as the actual form of torn paper used in recycling is not got back.


More from this chapter

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12

Which of the following changes cannot be reversed?

(a) Blowing of a balloon


(b) Folding a paper to make a toy airplane


(c) Rolling a ball of dough to make roti


(d) Baking cake in an oven


(e) Drying a wet cloth


(f) Making biogas from cow dung


(g) Burning of a candle

 13

Boojho’s sister broke a white dove, a symbol of peace, made of plaster of paris (POP). Boojho tried to reconstruct the toy by making a powder of the broken pieces and then making a paste by mixing water. Will he be successful in his effort? Justify your answer.

 15

Give one example in each case

(a) Change which occurs on heating but can be reversed.


(b) Change which occurs on heating but cannot be reversed.


(c) Change which occurs by mixing two substances, but can be reversed.


(d) Change which occurs by mixing two substances, but cannot be reversed.

 16

A potter working on his wheel-shaped a lump of clay into a pot. He then baked the pot in an oven. Do these two acts lead to the same kind of changes or different? Give your opinion and justify your answer.