NCERT Solutions Class 8 Science Chapter 4 Materials: Metals and Non-Metals
1. Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Solution:
Answer is a) Zinc
Explanation:
Here, Zinc is a metal with malleability and ductility whereas Phosphorus, Sulphur and Oxygen are nonmetals which lack malleability and ductility.
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.
Solution:
Answer is (c) Generally, metals are ductile.
Explanation:
Ductility is a property where a substance can be drawn into thin wires, Generally, metals are ductile with mercury as the exception.
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) 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.
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 |
1. Appearance |
|
|
2. Hardness |
|
|
3. Malleability |
|
|
4. Ductility |
|
|
5. Heat Conduction |
|
|
6. Conduction of Electricity |
|
|
Solution:
Properties |
Metals |
Non-metals |
1. Appearance |
Lustrous |
Dull |
2. Hardness |
Hard |
Soft |
3. Malleability |
Have property of Malleability |
Do not have a property of Malleability |
4. Ductility |
Have property of Ductility |
Do not have the property of Ductility |
5. Heat Conduction |
Good conductor of Heat |
Bad Conductor of Heat |
6. Conduction of Electricity |
Good conductor of Electricity |
The bad conductor 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 is malleable and can be drawn into thin sheets hence Aluminium foils are used to wrap food items
b) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity.
c) Copper cannot displace zinc from its salt solution because Zinc is more reactive than copper.
d) Sodium and Potassium are highly reactive metals which readily reacts with atmospheric Oxygen to catch fire hence Sodium and Potassium are stored in kerosene.
7. Can you store the lemon pickle in an aluminium utensil? Explain.
Solution:
Pickle consists of acids which react with Aluminium metal to produce salt and Hydrogen. Hence pickle is not stored in aluminium utensil.
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 |
(d) Jewellery |
(vi) Mercury |
(f) Fuel |
Solution:
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 |