NCERT Solution Class 8 Science – Chapter 4 Materials: Metals and Non-Metals

Question 1: Which of the following can be beaten into thin sheets?

(a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen

Answer

(a) Zinc

Question 2: Which of the following statements is correct?

(a) All metals are ductile.

(b) All non-metals are ductile.

(c) Generally, metals are ductile.

(d)Some non-metals are ductile.

(c) Generally, metals are ductile

However, mercury metal− a liquid at room temperature − cannot be drawn into wires and is not ductile.

Question 3: Fill in the blanks:

(a) Phosphorus is a very__non-metal.

(b) Metals are__conductors of heat and__.

(c) Iron is__reactive than copper.

(d) Metals react with acids to produce__gas.

a)   Phosphorus is a very reactive non-metal.

b)   Metals are good conductors of heat and electricity.

c)   Iron is more reactive than copper.

d)   Metals react with acids to produce hydrogen gas.

a)   Generally, non-metals react with acids. ( )

b)   Sodium is a very reactive metal. ( )

c)   Copper displaces zinc from zinc sulphate solution. ( )

d)   Coal can be drawn into wires. ( )

a)  Generally, non-metals react with acids. (F)

b)  Sodium is a very reactive metal. (T)

c)    Copper displaces zinc from zinc sulphate solution. (F)

d)    Coal can be drawn into wires. (F)

Question 5: Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.

Can be beaten into thin sheets

Cannot be beaten into thin sheets

Can be drawn into wires

Cannot be drawn into wires

Good conductors of heat

Poor conductors of heat

Conduction of Electricity

Good conductors of electricity

Poor conductors of electricity

Question 6: Give reasons for the following.

a)   Aluminum foils are used to wrap food items.

b)   Immersion rods for heating liquids are made up of metallic substances.

c)   Copper cannot displace zinc from its salt solution.

d)   Sodium and potassium are stored in kerosene.

a) Aluminum foils are used to wrap food items because aluminum metal is malleable. Therefore, it can be beaten into thin foils.

b) Metals are good conductors of heat and electricity. Therefore, immersion rods for heating liquids are made of metallic substances.

c) A metal can displace a less reactive metal from its salt in an aqueous solution.

But zinc is more reactive than copper. Therefore, copper cannot displace zinc from its salt solution.

Cu(s) + ZnSO4 (aq) → No reaction

d) Sodium and potassium are stored in kerosene because they are highly reactive elements. They can easily catch fire even when in contact with air.

Lemon pickle cannot be stored in aluminium utensils because lemon pickle contains acids, which can react with aluminium (metal) liberating hydrogen gas. This can lead to the spoiling of the pickle.

Question 8: Match the substances given in Column A with their uses given in Column B.

Question 9: What happens when

a)   Dilute sulphuric acid is poured on a copper plate?

b)   Iron nails are placed in copper sulphate solution?

Write word equations of the reactions involved.

a) When dilute sulphuric acid is poured on a copper plate, the copper metal reacts with sulphuric acid to liberate hydrogen gas.

b) Iron being more reactive displaces copper from copper sulphate solution. In this reaction, the blue colour of copper sulphate fades and there is deposition of copper on the iron nail.

Question 10: Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

a) How will she find the nature of the gas?

b) Write down word equations of all the reactions taking place in this process.

a) Add a few drops of water in the test tube containing gas. Now, cover the test tube and shake it well. After shaking, test the solution with blue litmus and red litmus. It will turn blue litmus red. Thus, the gas is acidic in nature.

b) Charcoal reacts with oxygen to form carbon dioxide gas.

b) Carbon dioxide reacts with water to form carbonic acid, which turns blue litmus paper red.

Question 11: One day Reeta went to a jeweller’s shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

To polish a gold ornament, it is dipped in a liquid called aquaregia (a mixture of hydrochloric acid and nitric acid). On getting the environment of aquaregia, the outer layer of gold dissolves and the inner shiny layer appears. The dissolving of the layer causes a reduction in the weight of the jewellery.