Science & Technology · Chapter 17

30 solved questions

Chapter 17: Metal and Non-metals

Every question in this chapter, answered and explained — step-by-step solutions drawn live from the chapter library across 8 question sections.

Very Short Answer Questions10 Short Answer Questions3 Q4. List the methods used for concentration of ore.1 Give Reason Questions5 Differentiate Between4 Long Answer Questions2 Application / Conceptual Questions2 Additional SEE Practice3

Very Short Answer Questions

1SEE Boardqb-q0

What is a mineral?

Ans.: A mineral is a naturally occurring pure, solid, crystalline element or compound found in the earth's crust, having a fixed chemical formula.

2SEE Boardqb-q1

What is an ore?

Ans.: An ore is a mineral from which a metal can be extracted in large amounts economically.

3SEE Boardqb-q2

What is gangue?

Ans.: The impurities such as mud, sand, and rock present in an ore are called gangue.

4SEE Boardqb-q3

What is metallurgy?

Ans.: Metallurgy is the science that deals with the properties, production, and purification of metals from their ores.

5SEE Boardqb-q4

Name the chief ore of iron.

Ans.: Hematite (Fe2O3) is the chief ore of iron.

6SEE Boardqb-q5

Name the chief ore of aluminium.

Ans.: Bauxite is the chief ore of aluminium.

7SEE Boardqb-q6

Which metal is found in a pure (free) state in nature?

Ans.: Gold is found in a pure (free) state in nature.

8SEE Boardqb-q7

What is grinding?

Ans.: Grinding is the process of crushing ore into small particles using rollers of machines.

9SEE Boardqb-q8

What is smelting?

Ans.: Smelting is the process of heating a metal oxide with a reducing agent above the melting point of the metal to obtain molten metal.

10SEE Boardqb-q9

Which method of purification is used for mercury?

Ans.: Distillation is used to purify mercury because it has a low boiling point and vaporizes easily.

Short Answer Questions

1SEE Boardqb-q10

What are the sources of metals?

Ans.: Metals are mainly obtained from minerals and ores found in the earth's crust. Non-reactive metals like gold and silver occur in a free state, while reactive metals like sodium, iron, and aluminium occur in the form of compounds (ores) such as oxides, sulphides, and carbonates.

2SEE Boardqb-q11

What is concentration of ore? Why is it necessary?

Ans.: Concentration is the process of removing gangue (impurities like mud, sand, rock) from an ore to increase the percentage of metal in it. It is necessary because it makes the further steps of extraction (oxidation, reduction, smelting) easier and more efficient.

3SEE Boardqb-q12

What is reduction? Name the common reducing agents.

Ans.: Reduction is the process of removing oxygen from a metal oxide to obtain the free metal. Common reducing agents are carbon, carbon monoxide, and hydrogen. Very reactive metal oxides are reduced only by electrolysis.

Q4. List the methods used for concentration of ore.

1SEE Boardqb-q13

What happens during electro-refining?

Ans.: In electro-refining, impure metal is made the anode and pure metal the cathode in a solution of the metal's salt. On passing electricity, the impure metal at the anode dissolves and pure metal deposits on the cathode, giving about 99% pure metal.

Give Reason Questions

1SEE Boardqb-q14

All ores are minerals, but all minerals are not ores. Why?

Ans.: Because an ore is a mineral from which metal can be extracted in large amounts at low cost. Some minerals contain very little metal, or the metal cannot be extracted from them economically, so such minerals are not called ores. This is why every ore is a mineral, but not every mineral is an ore.

2SEE Boardqb-q15

Ores are oxidised after concentration. Why?

Ans.: Because it is easier to extract metal from a metal oxide than directly from sulphide or carbonate ores. So the concentrated ore is first converted into its oxide (by roasting or calcination) before it is reduced to obtain the free metal.

3SEE Boardqb-q16

Zinc oxide is reduced only by carbon, not by hydrogen or electrolysis. Why?

Ans.: Zinc oxide has a moderate stability that makes it reducible by carbon, which is a strong, cheap, and effective reducing agent for it. Its reactivity does not require the more expensive electrolysis method, which is reserved for highly reactive metal oxides.

4SEE Boardqb-q17

Oxides of sodium, potassium, and calcium can be reduced only by electrolysis. Why?

Ans.: Because sodium, potassium, and calcium are highly reactive metals, and their oxides are very stable. Ordinary reducing agents like carbon or hydrogen cannot remove oxygen from such stable oxides, so only the strong reducing action of electrolysis can reduce them.

5SEE Boardqb-q18

Roasting is used for sulphide ores, while calcination is used for carbonate ores. Why?

Ans.: Roasting (heating in presence of air) helps convert sulphide ores into oxides by reacting the sulphide with oxygen. Calcination (heating in absence of air) is used for carbonate ores because heating alone, without needing oxygen, is enough to decompose a carbonate into its oxide and carbon dioxide.

Differentiate Between

1SEE Boardqb-q19

Differentiate between mineral and ore.

Mineral	Ore
A naturally occurring pure element or compound.	A mineral from which metal can be extracted economically.
May or may not have extractable metal content.	Always has metal in extractable, profitable amount.

2SEE Boardqb-q20

Differentiate between roasting and calcination.

Roasting	Calcination
Done in the presence of air/oxygen.	Done in the absence of air.
Used for sulphide ores.	Used for carbonate ores.

3SEE Boardqb-q21

Differentiate between oxidation and reduction.

Oxidation	Reduction
Addition of oxygen to a substance.	Removal of oxygen from a metal oxide.
Done by roasting or calcination.	Done using reducing agents or electrolysis.

4SEE Boardqb-q22

Differentiate between distillation and electro-refining.

Distillation	Electro-refining
Impurities are removed by boiling/vaporizing the metal.	Impurities are removed using electrolysis.
Used for metals with low boiling point, e.g., mercury.	Used for metals like iron, silver, copper, gold.

Long Answer Questions

1SEE Boardqb-q23

How is metallurgy a stepwise process? Explain.

Ans.Metallurgy involves extracting pure metal from its ore through a series of steps, since raw ore mined from the earth contains many impurities.

Each step depends on the properties of the ore and the reactivity of the metal, so metallurgy is carried out stepwise rather than in a single operation.

2SEE Boardqb-q24

Describe the ores of iron, copper, aluminium, and silver with their chief ores.

Metal	Common Ores	Chief Ore	% Metal in Chief Ore
Iron	Hematite, Magnetite, Siderite, Limonite, Iron pyrite	Hematite (Fe2O3)	~75%
Aluminium	Bauxite, Cryolite, Corundum	Bauxite	~40–60%
Copper	Chalcocite, Chalcopyrite, Cuprite, Malachite	Chalcopyrite (CuFeS2)	~34.5%
Silver	Argentite, Horn silver, Ruby silver, Silver copper glance	Argentite (Ag2S)	~87%

Application / Conceptual Questions

1SEE Boardqb-q25

Why can gold jewellery be made without first extracting gold from an ore chemically?

Ans.: Because gold is a non-reactive metal, it occurs in a pure (free) state in nature, mainly in rocks and alluvial soil. So it does not need chemical oxidation-reduction steps like reactive metals do; it mainly needs physical separation and refining.

2SEE Boardqb-q26

A student tries to reduce aluminium oxide using carbon, but it does not work. Explain why.

Ans.: Aluminium is a highly reactive metal, so its oxide is very stable. Ordinary reducing agents like carbon are not strong enough to remove oxygen from such a stable oxide. Only the strong reducing action of electrolysis can reduce aluminium oxide to free aluminium.

Additional SEE Practice

1SEE Boardqb-q27

Which is the primary/first step of metal extraction?

Ans.: Grinding is the first step of metal extraction.

2SEE Boardqb-q28

In which process is smelting included: oxidation or reduction?

Ans.: Smelting is closely linked with the reduction process, as it involves heating the oxide with a reducing agent above the metal's melting point to obtain molten free metal.

3SEE Boardqb-q29

Name two places in Nepal where minerals are found.

Ans.: Minerals are found in places like Dang and Rolpa in Nepal (other examples: Salyan, Gulmi, Pyuthan, Lalitpur, Palpa, Nawalparasi).

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