Materials Metals and Non Metals - Exemplar Solutions 3

CBSE Class 8 Science
NCERT Exemplar Solution
Materials: Metals and Non-Metals

22. Paheli bought a statue made of copper. To her surprise, it acquired a dull green coating after a couple of months. Explain the reason.
Ans. The green material is a mixture of copper hydroxide and copper carbonate formed due to reaction of copper with moist air (water, oxygen and carbon dioxide).

23. In Fig 4.1 you find that the bulb glows when an iron nail is placed between two ends of wire. Complete the following sentences on the bases of this fact.
(a) __________ is a metal.
(b) Metals are good __________ of electricity.
Ans. (a) iron (b) conductor

24. If in Fig. 4.1 iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer.
Ans. The bulb will not glow as wood is not a conductor of electricity so circuit will not be completed .

25. Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour?
Ans. In beaker A, a reddish-brown layer of copper will deposit on the iron nail and the blue coloured solution will become yellowish green. On the other hand, no change is observed in beaker B.

26. A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain.
Ans. The tablet is not made of iron metal, instead it contains a salt of iron. 

27. Match the substances in Column A with their applications given in Column B.
Ans. (a)-(iii), (b)-(iv), (c)-(i), (d)-(v), (e)-(ii).