Q12 of 20 Page 34

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

(a) Can be reversed


(b) Can be reversed


(c) Can be reversed


(d) Cannot be reversed


(e) Can be reversed


(f) Cannot be reversed


(g) Cannot be reversed


Therefore, from the given options, the changes which cannot be reversed are (d), (f) and (g).


More from this chapter

All 20 →
10

Paheli had bought a new bottle of from the market. She tried to open the metal cap to taste it but could not do so. She then took a bowl a bowl of hot water and immersed the upper end of the bottle in it for five minutes. She could easily open the bottle now. Can you give the reason for this?

 11

Can we reverse the following changes? If yes, suggest the name of the method.

(a) Water into water vapour


(b) Water vapour into water.


(c) Ice into the water.


(d) Curd into milk.

 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.

 14

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

What about paper recycling?