Question 15 Marks
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
(i) Do you think rust is different from iron?
(ii) Can you change rust back into iron by some simple method?
(iii) Do you think formation of rust on iron is a chemical change?
(iv) Give two other examples of a similar type of change.
(i) Do you think rust is different from iron?
(ii) Can you change rust back into iron by some simple method?
(iii) Do you think formation of rust on iron is a chemical change?
(iv) Give two other examples of a similar type of change.
Answer
View full question & answer→(i) Yes, rust is iron oxide $\left( Fe _2 O _3\right)$. Thus, rust and iron are not the same substance.
(ii) No, in the process of rusting, a new substance, rust (iron oxide) is formed. It cannot be reversed by any method.
(iii) Yes, rusting of iron is a chemical change. During the rusting of iron, it combines with the oxygen in the presence of water (moisture) to form a new compound 'iron oxide'. This iron oxide is a rust.
It is a permanent change which cannot be reversed back. So, rusting of iron is a chemical change.
(iv) Two other examples of chemical change are
(a) Setting of curd from milk.
(b) Burning of magnesium ribbon to form magnesium oxide.
(ii) No, in the process of rusting, a new substance, rust (iron oxide) is formed. It cannot be reversed by any method.
(iii) Yes, rusting of iron is a chemical change. During the rusting of iron, it combines with the oxygen in the presence of water (moisture) to form a new compound 'iron oxide'. This iron oxide is a rust.
It is a permanent change which cannot be reversed back. So, rusting of iron is a chemical change.
(iv) Two other examples of chemical change are
(a) Setting of curd from milk.
(b) Burning of magnesium ribbon to form magnesium oxide.
