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 helps students do better and memorize more easily during times of intense pressure. NCERT Solutions helps you in getting good grades by providing solutions for all chapters that are related to the test.

Chapter 4 CBSE Class 8 Science NCERT Solutions are prepared by experts who are familiar with the latest CBSE guidelines. You can use them to score maximum marks in your exams. It is difficult for students to prepare for tests.

Chapter 4 Materials: Metals and Non-metals Class 8 Science NCERT Solutions

Exercises

1. Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
▶ (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.
▶ (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.

Solution

(a) vigorous
(b) good, electricity
(c) more
(d) 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.

Solution

(a) False
(b) True
(c) False
(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
Appearance
Hardness
Malleability
Ductility
Heat Conduction
Conduction of Electricity

Solution

Properties	Metals	Non-metals
Appearance	They have silvery or grey lustre.	They have a dull appearance.
Hardness	They are hard.	They are soft.
Malleability	They are malleable materials.	They are non-malleable materials.
Ductility	They are ductile.	They are non-ductile.
Heat Conduction	They are good conductors of heat.	They are poor conductors of heat.
Conduction of Electricity	They are good conductors of electricity.	They are poor conductors of electricity.

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.

Solution

(a) Aluminium foils are used to wrap food items because aluminium is malleable and a good conductor of heat, so it will keep the food hot, and used to wrap food items.
(b) Since metals conduct heat and electricity well, immersion rods used to heat liquids are made from metallic substances.
(c) The more reactive the metal, the more likely it is to displace the less reactive metal from its solution. Copper is less reactive than zinc, so it cannot displace zinc from its salt solution.
(d) As sodium and potassium react with moist air and produce a lot of heat, they can easily start a fire and cause a lot of damage, so they are kept in kerosene.

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

Solution

There is no way to store lemon pickles in aluminium containers since lemon contains citric acid, which reacts with aluminium to produce a salt of aluminium and hydrogen gas, which spoils food.

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

Column A	Column 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

Solution

Column A	Column 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.

Solution

(a) When sulphuric acid is poured on a copper plate, copper reacts with the acid and produces copper sulphate and hydrogen gas.
Copper + Sulphuric Acid → Copper Sulphate + Hydrogen Gas
(b) Iron is a more reactive metal than copper. When iron nails are placed in the copper sulphate solution, iron displaces copper and forms iron sulphate. This reaction fades the blue colour of the copper sulphate solution and a brown deposit of copper is seen at the bottom of the beaker.
Iron + Copper Sulphate → Iron Sulphate + 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?
(b) Write down word equations of all the reactions taking place in this process.

Solution

Charcoal is a form of carbon and when carbon reacts with oxygen then carbon dioxide gas is evolved from it. If we pass carbon dioxide from lime water then it will turn milky. This is CO2 gas test
C (Carbon) + O₂ (Oxygen) → CO₂ (Carbon dioxide)
Carbon dioxide reacts with water to form carbonic acid which turns blue litmus paper red.
CO₂ (Carbon dioxide) + H₂O (Water) → H₂CO₃ (Carbonic acid)

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?

Solution

To polish gold jewellery, jewellers usually use a strong acidic solution. As the gold is dipped in the acidic solution, it reacts with the acid. A small amount of gold dissolves in the acid from the outer layer of the jewellery, resulting in a slight reduction in weight.