NCERT Solutions for Class- 8 Science Chapter 4 – Materials Metals and Non-Metals
Orchid International School is committed to providing valuable educational resources. We offer free PDF downloads of NCERT Solutions for Class 8 Science (Chemistry) Chapter 4 - "Materials: Metals and Non-Metals." These solutions are meticulously prepared by expert educators in accordance with NCERT (CBSE) guidelines. They encompass all Exercise Questions from Chapter 4, ensuring that students have the necessary tools to comprehensively review the syllabus and achieve higher grades.
Materials Metals and Non-Metals
Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen.
(a) Zinc. It can be beaten into thin sheets.
Which of the following statements is correct?
-
All metals are ductile.
-
All non-metals are ductile.
-
Generally, metals are ductile.
-
Some non-metals are ductile.
(c) Generally, metals are ductile. Mercury, on the other hand, is a liquid metal that cannot be formed into thin wires and is not ductile at normal temperature.
Fill in the blanks in the following statements.
-
Phosphorus is a very ____ non-metal.
-
Metals are ____ conductors of heat and ______.
-
Iron is ______ reactive than copper.
-
Metals react with acids to produce _______ gas.
1 : Phosphorus is a very reactive non-metal.
2 : Metals are good conductors of heat and electricity.
3 : Iron is more reactive than copper.
4 : Metals react with acids to produce hydrogen gas.
Mark 'T' if the statement is true and 'F' if it is false.
(i) Generally, non-metals react with acids. ( )
(ii) Sodium is a very reactive metal. ( )
(iii) Copper displaces zinc from zinc sulphate solution. ( )
(iv) Coal can be drawn into wires. ( )
(i) (F)
(ii) (T)
(iii) (F)
(iv) (F)
Some properties are listed in the following table. Distinguish between metals and nonmetals 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 |
|
Properties |
Metals |
Non-metals |
|
Malleability |
Can be beaten into thin sheets |
Cannot be beaten into thin sheets |
|
Ductility |
Can be drawn into thin wires |
Cannot be drawn into thin wires |
|
Appearance |
Lustrous |
Dull |
|
Hardness |
Hard |
Soft |
|
Conduction of Electricity |
Good conductors of electricity |
Poor conductors of electricity |
|
Heat Conduction |
Good conductors of heat |
Poor conductors of heat |
Give reasons for the following.
-
Aluminium foils are used to wrap food items.
- Immersion rods for heating liquids are made up of metallic substances.
- Copper cannot displace zinc from its salt solution.
- Sodium and potassium are stored in kerosene.
1. Food is wrapped in aluminium foil because the metal can be drawn into thin sheets (malleable).
2 . Metal immersion rods are used to heat liquids because metals are excellent heat and electrical conductors.
3 . Because Copper is less reactive than Zinc, it cannot displace Zinc from its salt solution. Metal reactivity series can help you understand this better.
Cu(s) + ZnSO4 (aq) → No reaction
4 .Because sodium and potassium are very reactive with oxygen in the atmosphere, they are kept in kerosene.
Can you store the lemon pickle in an aluminium utensil? Explain.
Lemon pickle includes acids, thus it cannot be preserved in aluminium utensils.
Acids react with aluminium, releasing hydrogen, causing the pickle to spoil.
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 |
|
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 |
What happens when
-
Dilute sulphuric acid is poured on a copper plate?
-
Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
1 . When dilute sulphuric acid is poured on a copper plate, the copper metal reacts with the sulphuric acid, releasing hydrogengas.
Copper(Cu) + Sulphuric acid(H2SO4) -------> Copper sulphate(CuSO4) + Hydrogen gas(H2)
2 . When a copper sulphate solution is used to soak an iron nail. Copper is displaced by iron in a copper sulphate solution, resulting in copper and iron sulphate. Copper is less reactive than iron.
Iron(Fe) + Copper sulphate(
Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
-
How will she find the nature of the gas?
- Write down word equations of all the reactions taking place in this process.
1 . When a few drops of water are added to a gas-filled test tube. In water, gas is dissolved. Use blue litmus to test the gas and water solution. The blue litmus changes colour to red, indicating that the gas is acidic.
2 .Charcoal releases CO2 when it is burnt. CO2 is a greenhouse gas.
C + O2 -------> CO2
(Carbon
from
charcoal) (Oxygen) (Carbon Dioxide)
Carbonic acid is formed when carbon dioxide gas combines with water, turning blue litmus red.
CO2 + H2O -------> H2CO3
(Carbon Dioxide) (Water) (Carbonic acid)
(Turns blue litmus red)
One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. The next day when they brought the jewelry back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss of weight?
The ancient gold jewellery is soaked in a solution called Aqua Regia to polish it (1:3 molar ratio of HNO3 and HCl). Aqua Regia dissolves the outer layer of the golden jewellery. The removal of the outer layer reduces the weight of gold jewellery.
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