NCERT Solutions Science for Class 8 Chapter 4 MATERIALS METALS AND NONMETALS
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NCERT Solutions Science for Class 8 Chapter 4 MATERIALS METALS AND NONMETALS
class8 science Chapter 4
NCERT Solutions Science for Class 8 Chapter 4 MATERIALS METALS AND NONMETALS
science for class 8 Chapter 4 question answer
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 :
| (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 ) |
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 | All metals are generally shiny. Exception – mercury |
Generally non-metals are not shiny. |
| 2. Hardness | generally hard Exceptions – sodium and potassium |
Generally non-metals are soft. Exception – Diamond is hard. |
| 3. Malleability | Metals can be beaten into thin sheets. That is, it is malleable. | Non-metals are brittle. On beating them, it breaks into pieces. |
| 4. Ductility | Metals are ductile, meaning they can be drawn into wires. | Non-metals are not ductile. |
| 5. Heat Conduction | Metals are good conductors of heat. | Metals are not good conductors of heat. |
| 6. Conduction of Electricity | Metals are good conductors of electricity. | Metals are not good conductors of heat. |
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) Aluminium foils are used to wrap food items.
Aluminum is a metal that can be beaten into thin sheets. Also, it is a metal that does not rust even in the presence of air. Hence it is used for wrapping food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
Metals are good conductors of electricity. Due to which it gets hot after receiving heat and also heats the water. Therefore, metallic materials are used in immersion rods to conduct electricity.
(c) Copper cannot displace zinc from its salt solution.
This is because copper is less reactive than zinc. A less reactive metal cannot displace a more reactive metal.
(d) Sodium and potassium are stored in kerosene.
Both metals are highly reactive, and when left open in air, they activate immediately and catch fire. Therefore, to break the contact of these metals with air, they are kept in kerosene.
7. Can you store lemon pickle in an aluminium utensil? Explain.
Answer : No, lemon pickle cannot be stored in aluminum utensil. Because lemon contains citric acid which reacts with aluminum to form harmful substances. which is injurious to health.
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) Dilute sulphuric acid is poured on a copper plate?
When dilute sulfuric acid is poured on a copper plate, copper sulphate, water and sulfur dioxide are produced.
2H2SO4 + Cu → CuSO4 + 2H2O + SO2
Dilute Sulfuric + Copper → Copper Sulphate + Water + Sulfur Dioxide
(b) Iron nails are placed in copper sulphate solution?
When an iron nail is placed in a solution of copper sulphate, iron displaces copper from the sulphate solution in a chemical reaction between the two. As a result, iron sulphate and copper are produced.
Fe + CuSO4 → FeSO4 + Cu
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. |
Answer :
(a) How will she find the nature of the gas ?
Saloni will first dissolve water in the gas filled in the test tube. We know that coal burns in the presence of air, which produces carbon dioxide gas and this gas dissolves in water to produce carbonic acid. Which can be tested with the help of litmus paper. If it turns blue litmus paper red, the solution is acidic in nature, otherwise it is alkaline.
(b) Write down word equations of all the reactions taking place in this process.
C + O2 → CO2
carbon + oxygen → carbon dioxide
CO2 + H2O → H2CO3
carbon dioxide + water organic → 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?
Answer : When we take the jewelery to the goldsmith for polishing, first of all he dissolves them in concentrated nitric acid and hydrochloric acid. This solution dissolves the gold inside itself. When the jewelery is put in this solution, the top layer of the jewelery gets dissolved in this solution. Due to which the shiny layer below comes out. As the top layer of the ornament is dissolved in the solution, the whole is reduced.
