NCERT Class VIII Science Solutions: Chapter 4-Materials: Metals and Non-Metals Part 4

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Question 21:

Which of the following metals can displace the other two metals from their salt solutions? Zinc, iron, copper

Answer:

Zinc

SHORT ANSWER QUESTION

Question 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.

Answer:

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).

Question 23:

In 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.

Result for electric cricuit

Electric Cricuit

Result for electric cricuit

  1. __________ is a metal.

  2. Metals are good __________ of electricity.

Answer:

  1. Iron is a metal.

  2. Metals are good conductor of electricity.

Question 24:

If in iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer.

Answer:

The bulb will not glow as wood is not a good conductor of electricity.

Image of conductor of electricity

Conductor of Electricity

Image of conductor of electricity

Question 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?

Answer:

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.

Question 26:

A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain.

Answer:

The tablet is not made of iron metal, instead it contains a salt of iron