NCERT Solutions for Class 8th Science Chapter 11 Materials: Metals and Non-Metals Questions and answers based on the latest syllabus of CBSE and JKBOSE
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
- Correct 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.
- Correct answer: (c) Generally, metals are ductile.
3. Fill in the blanks:
(a) Phosphorus is a very _ non-metal.
- Answer: reactive
(b) Metals are conductors of heat and _.
- Answer: electricity
(c) Iron is _ reactive than copper.
- Answer: more
(d) Metals react with acids to produce _ gas.
- Answer: hydrogen
4. Mark ‘T’ if the statement is true and ‘F’ if it is false.
(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 | Lustrous (shiny) | Non-lustrous (dull) |
| 2. Hardness | Hard | Soft (except diamond) |
| 3. Malleability | Malleable | Non-malleable |
| 4. Ductility | Ductile | Non-ductile |
| 5. Heat Conduction | Good conductors | Poor conductors |
| 6. Conduction of Electricity | Good conductors | Poor conductors |
6. Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
- Aluminium foils are used to wrap food items because aluminium is highly malleable and can be beaten into thin sheets. It is also non-toxic and helps in keeping the food fresh.
(b) Immersion rods for heating liquids are made up of metallic substances.
- Immersion rods are made of metallic substances because metals are good conductors of heat, which allows efficient heating of liquids.
(c) Copper cannot displace zinc from its salt solution.
- Copper cannot displace zinc from its salt solution because copper is less reactive than zinc.
(d) Sodium and potassium are stored in kerosene.
- Sodium and potassium are highly reactive metals and react vigorously with water and air. To prevent these reactions, they are stored in kerosene.
7. Can you store lemon pickle in an aluminium utensil? Explain.
- No, lemon pickle cannot be stored in an aluminium utensil because lemon contains acids that react with aluminium, leading to the formation of harmful compounds and spoiling the pickle.
8. In the following Table some substances are given in Column I. In Column II some uses are given. Match the items in Column I with those in Column II.
| Column I | Column II |
|---|---|
| (i) Gold | (c) 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?
- The copper plate will react with dilute sulphuric acid to form copper sulphate and hydrogen gas.
Reaction: Cu + H₂SO₄ → CuSO₄ + H₂
(b) Iron nails are placed in copper sulphate solution?
- Iron will displace copper from copper sulphate solution, forming iron sulphate and depositing copper.
Reaction: Fe + CuSO₄ → FeSO₄ + Cu
10. Sarish 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?
- She can pass the gas through lime water. If the lime water turns milky, the gas is carbon dioxide.
(b) Write down word equations of all the reactions taking place in this process.
Reaction: Carbon (charcoal) + Oxygen → Carbon dioxide
Word Equation: Carbon + Oxygen → Carbon dioxide
11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave 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?
- The goldsmith uses an acidic solution called aqua regia to polish the gold, which dissolves a thin layer of gold from the surface, causing a slight loss in weight.
12. Why phosphorus is stored in water?
- Phosphorus is stored in water to prevent it from coming in contact with oxygen in the air, as it is highly reactive and can catch fire spontaneously.
Extended Learning — Activities and Projects
- Prepare Index Cards for any four metals and four non-metals. The card should have information like name of metal/non-metal; its physical properties, chemical properties and its uses.
These solutions and notes provide a detailed understanding of the topics covered in the chapter “Materials: Metals and Non-Metals,” helping students grasp the concepts more effectively.
