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NCERT Solutions for Class 8 Science Chapter 4 Materials Metals and Non Metals

NCERT Solutions for Class 8 Science Chapter 4 Materials Metals and Non Metals

 

Exercises

 

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

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

Answer:- (a) Zinc

 

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

Answer:- (c) Generally, metals are ductile.

 

 

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.

Answer:-

  • (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.

 

 

4. Mark ‘T’ if the statement is true and ‘F ’ if it is false.

  • (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. ( )

Answer:-

  1. a) False
  2. b) True
  3. c) False
  4. d) False

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

Properties

Metals

Non-metals

1. Appearance

 

 

2. Hardness

 

 

3. Malleability

 

 

4. Ductility

 

 

5. Heat Conduction

 

 

6. Conduction of Electricity

 

 

 

Answer:-

Properties

Metals

Non-metals

1. Appearance

Lustrous

Dull

2. Hardness

Hard

Soft

3. Malleability

malleable

Non- malleable

4. Ductility

ductile

Non- ductile

5. Heat Conduction

Good conductor

Bad conductor or insulator

6. Conduction of Electricity

Good conductor

Bad conductor or insulator

 

 

6. Give reasons for the following.

(a) Aluminium 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.

Answer:-

a) As aluminium is highly malleable and can be drawn into thin sheets easily hence Aluminium foils are used to wrap food items.

(b) Metals are very good conductors of heat and electricity, hence Immersion rods for heating liquids are made up of metallic substances.

(c) Copper is less reactive than zinc hence copper cannot displace zinc from its salt solution.

d) Because sodium and potassium are very reactive metals that easily catch fire when exposed to atmospheric oxygen, hence they are stored in kerosene.

 

7. Can you store lemon pickle in an aluminium utensil? Explain.

Answer:-  Lemon pickle is made up of acids that react with the aluminium metal to form salt and hydrogen. As a result, pickles gets spoiled easily hence they are not kept in aluminium utensils.

 

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

     A

B

(i) Gold

(a) Thermometers

(ii) Iron

(b) Electric wire

(iii) Aluminium

(c) Wrapping food

(iv) Carbon

(d) Jewellery

(v) Copper

(e) Machinery

(vi) Mercury

(f) Fuel

 

Answer:-

     A

B

(i) Gold

(d) Jewellery

(ii) Iron

(e) Machinery

(iii) Aluminium

(c) Wrapping food

(iv) Carbon

(f) Fuel

(v) Copper

(b) Electric wire

(vi) Mercury

(a) Thermometers

 

 

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.

Answer:- (a) No reaction will take place because copper is very less reactive.

(b) Iron is more reactive than copper hence it will replace copper from its solution. The blue colour of copper sulphate diminishes in this process, and copper is deposited on the iron nail.

Iron + Copper sulphate (solution) → Iron sulphate (solution) + Copper

 

 

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 ?

Answer:- (a) She can use moist litmus paper to determine the gas’s type. If the acidic gas turns the blue litmus paper red after coming into touch with it, it is acidic. It’s also basic if it changes the red litmus into blue.

 

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

Answer:- (b) (i) Carbon + Oxygen → Carbon dioxide

(ii) Carbon dioxide + Lime water → Milky

 

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?

Answer:-  The gold jewellery must be soaked in a liquid called aqua regia to polish it (a mixture of hydrochloric acid and nitric acid). When gold is dissolved in aqua regia, the outer layer of gold dissolves and a shiny inner layer shows. The weight of the jewellery is reduced due to the layer’s dissolution.