(Q.4) Answer the following questions in brief.
(1) Give examples to explain the difference between
change that can or can not be reversed?
2) What is sieving? Where it is used?
(3) What is winnowing? Where it is used ?
(4) How will you separate sand and water from their mixture?
5) You accidently dropped your favourite toy and broke it This is a change you
did not want can this change be reversed
Answers
Explanation:
1 Melting of ice is a reversible change. ... When ice cubes are kept at room temperature, they turn into water after some time. On the other hand, burning of a piece of paper is an irreversible change. 2 Sieving is a simple technique for separating particles of different sizes. A sieve such as used for sifting flour has very small holes. ... Sieves are also used to separate stones from sand. 3 Winnowing: The process of separating heavier and lighter components of a mixture by wind or by blowing air is called winnowing. This method is used by farmers to separate lighter husk particles from heavier seeds of grain. 4 When sand is added to water it either hangs in the water or forms a layer at the bottom of the container. Sand therefore does not dissolve in water and is insoluble. It is easy to separate sand and water by filtering the mixture. Salt can be separated from a solution through evaporation. 5 No, this change cannot be reversed. Because breaking of a toy is as irreversible change, one cannot regain the same toy.