SEBA Class 8 Science Chapter 3 Materials: Metals and Non Metals Solutions English Medium to each chapter is provided in the list so that you can easily browse through different chapters SEBA Class 8 Science Chapter 3 Materials: Metals and Non Metals Question Answer and select need one. SEBA Class 8 Science Chapter 3 Materials: Metals and Non Metals Solutions Download PDF. SEBA Class 8 Science Texbook Solutions English Medium.
SEBA Class 8 Science Chapter 3 Materials: Metals and Non Metals
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Materials: Metals and Non Metals
Chapter: 3
PART – I
EXERCISE
Choose the Correct Option:
1. Which of the following can be beaten into thin sheets?
(a) Zinc.
(b) Phosphorus.
(c) Sulphur.
(d) Oxygen.
Ans: (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.
Ans: (c) Generally, metals are ductile.
3. Fill in the blanks:
(a) Phosphorus is a very ______ non-metal.
Ans: Phosphorus is a very reactive non-metal.
(b) Metals are __________ conductors of heat and _________.
Ans: Metals are good conductors of heat and electricity.
(c) Iron is ________ reactive than copper.
Ans: Iron is more reactive than copper.
(d) Metals react with acids to produce ________ gas.
Ans: 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. ()
Ans: False.
(b) Sodium is a very reactive metal. ()
Ans: True.
(c) Copper displaces zinc from zinc sulphate solution. ()
Ans: False.
(d) Coal can be drawn into wires. ()
Ans: 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 |
| (i) Appearance | ||
| (ii) Hardness | ||
| (iii) Malleability | ||
| (iv) Ductility | ||
| (v) Heat Conduction | ||
| (vi) Conduction of Electricity |
Ans:
| Properties | Metals | Non-metals |
| (i) Appearance | Shiny and lustrous | Dull, non-lustrous (except graphite and iodine) |
| (ii) Hardness | Generally hard (except sodium, potassium) | Generally soft (except diamond) |
| (iii) Malleability | Can be beaten into thin sheets | Brittle, cannot be beaten into sheets |
| (iv) Ductility | Can be drawn into wires | Non-ductile, break when stretched |
| (v) Heat Conduction | Good conductors of heat | Poor conductors (except graphite) |
| (vi) Conduction of Electricity | Good conductors of electricity | Poor conductors (except graphite) |
6. Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
Ans: Aluminium foils are used to wrap food items because aluminium is highly malleable, which means it can be easily beaten into thin sheets. Moreover, aluminium does not react with food and acts as a barrier to moisture, light, and bacteria, keeping the food fresh.
(b) Immersion rods for heating liquids are made up of metallic substances.
Ans: Immersion rods are made up of metals because metals are good conductors of heat and electricity. This property allows the rod to efficiently transfer heat from the electric current to the liquid, making the heating process quick and effective.
(c) Copper cannot displace zinc from its salt solution.
Ans: Copper cannot displace zinc from its salt solution because zinc is more reactive than copper. According to the reactivity series of metals, a less reactive metal (like copper) cannot displace a more reactive metal (like zinc) from its compound.
(d) Sodium and potassium are stored in kerosene.
Ans: Sodium and potassium are stored in kerosene because they are highly reactive metals. They react vigorously with oxygen and moisture in the air, which can cause them to catch fire. Storing them in kerosene prevents contact with air and moisture, thus avoiding accidental reactions.
7. Can you store lemon pickle in an aluminium utensil? Explain.
Ans: No, lemon pickle should not be stored in an aluminium utensil.
Lemon pickle contains acids (like citric acid) which can react with aluminium. When acidic substances come in contact with aluminium, a chemical reaction takes place, leading to the formation of toxic aluminium salts. These salts can contaminate the pickle, making it unsafe for consumption.
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) Carban | (d) Jewellery |
| (iv) Copper | (e) Machinery |
| (v) Mercury | (f) Fuel |
Ans:
| A | B |
| (i) Gold | (d) Jewellery |
| (ii) Iron | (e) Machinery |
| (iii) Aluminium | (c) Wrapping food |
| (iv) Carban | (f) Fuel |
| (iv) Copper | (b) Electric wire |
| (v) 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.
Ans: (a) No reaction occurs because copper is less reactive than hydrogen and cannot displace it from dilute sulphuric acid.
Equation: Cu+H2SO4→No reaction
(b) Reaction occurs because iron is more reactive than copper and displaces it.
Observation: Blue colour of CuSO₄ fades, and iron nails get a reddish-brown copper coating.
Equation: Fe+CuSO4→FeSO4+Cu
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?
Ans: To find the nature of the gas, Saloni can pass the gas through lime water. If the lime water turns milky, it indicates the presence of carbon dioxide gas.
(b) Write down word equations of all the reactions taking place in this process.
Ans: The word equations of the reactions taking place are:
(i) Combustion of Charcoal:
Carbon (C) + Oxygen (O₂) → Carbon Dioxide (CO₂)
(ii) Reaction with Lime Water:
Carbon Dioxide (CO₂) + Calcium Hydroxide (Ca(OH)₂) → Calcium Carbonate (CaCO₃) + Water (H₂O)
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?
Ans: When gold jewellery is polished, the goldsmith uses certain chemicals and abrasives to clean and remove the outer layer of the jewellery. This outer layer often contains impurities, dirt, or tarnished gold. During the polishing process, a small amount of gold may get scraped off or dissolved, resulting in a slight reduction in the overall weight of the jewellery.
In addition, polishing may also involve using acids or solutions that can slightly erode the surface, especially if the jewellery had a thin layer of impurity or oxidation. This process naturally causes a minor loss in weight.
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