V. Answer the following questions : 1. A sharpener loses its sharpening power, if used continuously. Is the loss of sharpening
power a reversible change or an irreversible change?
2. Is ironing of clothes an irreversible change? Give a reason for your answer,
3. Is converting wood into saw dust a reversible change? Give one reason for your answer
4. State three ways by which a change can be brought about
5. Differentiate between a reversible and an irreversible change,
6. How the expansion of metals, which is a reversible change, put to good user Support your
answer by an example.
7. How does the solubility of a substance change with :
(a) rise in temperature
(b) fall in temperature?
8. Why is it difficult to dissolve sugar in ice cold water?
9. You have accidently dropped a glass tumbler, which breaks. Is the change reversible? Give
reason.
10. Give four examples of the change which :
(a) cannot be reversed
(b) can be reversed.
11. A thick coating of plaster of Paris paste is applied on a bandage on a fractured bone. The
paste becomes hard on drying. Can this change be reversed?
12. You have boiled some milk on a hot summer day. On cooling it you forgot to place it in
the fridge. What kind of change will take place in the milk after 12 hours and why?
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