Class 10 Chemistry Chapter 6 Notes Kerala Syllabus Metals Questions and Answers

Students rely on SCERT Kerala Syllabus 10th Standard Chemistry Textbook Solutions and Class 10 Chemistry Chapter 6 Metals Notes Questions and Answers English Medium to help self-study at home.

SSLC Chemistry Chapter 6 Notes Questions and Answers Pdf Metals

SCERT Class 10 Chemistry Chapter 6 Metals Notes Pdf

SSLC Chemistry Chapter 6 Questions and Answers – Let Us Assess

Question 1.
Define the following and answer the given questions.
(1) Ore – What is the ore of aluminium?
(2) Roasting – Which type of ores are subjected to roasting?
(3) Reducing agent – What is the reducing agent used in the manufacture of aluminium?
(4) Flux – Which flux is used in the manufacture of copper? Why?
(5) Leaching – Which metal ore is leached with sodium cyanide?
Answer:
(1) Ore – Any mineral from which a metal can be extracted easily and economically is called an ore of that metal. Ore of Aluminium is Bauxite

(2) Roasting – Roasting refers to heating the concentrated ore at a temperature below the melting point in the presence of air. Sulphide ores are subjected to roasting,

(3) Reducing agent – The chemical species that helps reduction is the reducing agent. The reducing agent gets oxidised in a chemical reaction. The reducing agent used in the manufacture of aluminium is electricity.

(4) Flux – The ore may contain impurities that cannot be removed in the first stages of concentration methods. In order to remove these impurities, a substance is added during the metallurgical stage. This substance is known as Flux.
Flux used in the manufacture of Copper is Sand (SiO₂). The ore contains basic impurities such as iron oxide even after concentration. So acidic flux is used.

(5) Leaching – The powdered ore is mixed with a suitable solvent. The ore dissolves in it or undergoes a chemical reaction to become a solution. The gangue remains insoluble in it. It is then filtered out. This process is called leaching. Metal ore leached with sodium cyanide is gold and silver.

Question 2.
Find the relation and write the answer.
Zinc sulphide: Roasting
Calcium carbonate: …………(a)…………..
Magnetite: Magnetic separation
Bauxite: …………(b)…………..
Answer:
(a) Calcination
(b) Leaching

Question 3.
The chemical reaction that occurs when calcium carbonate is heated is given.
CaCO₃ CaO + CO₂
How is this chemical change of calcium carbonate utilised in the industrial preparation of iron?
Answer:
The chemical change of calcium carbonate (CaCO₃) is utilised in the industrial preparation of iron to remove impurities from the iron ore. The product of this reaction, calcium oxide (CaO), acts as a flux in the blast furnace.

When heated, calcium carbonate decomposes into calcium oxide and carbon dioxide. The calcium oxide then reacts with the silica (SiO₂) impurities present in the iron ore, forming a molten substance called slag (calcium silicate, CaSiO₂). This slag is less dense than the molten iron, allowing it to float on top and be easily separated, thus purifying the iron. The overall reaction for slag formation is:
CaO(s) + SiO₂(s) → CaSiO₂(l)

Question 4.
Following are two facts related to the manufacture of an industrially important metal.
• The ore is treated with hot NaOH solution.
• Electricity is used as the reducing agent to extract the metal.
(i) These facts are related to the production of which metal?
(ii) What is the reason for using electricity as the reducing agent?
(iii) Which substance is used as the electrolyte here?
(iv) Which gas is liberated at the anode?
Answer:
(i) Aluminium
(ii) Aluminium is a highly reactive and electropositive metal.
(iii) Molten cryolite (Na₃AlF₆)
(iv) Oxygen (O₂)

Question 5.
A portion of the periodic table is given.

(i) Which method given below is more possible for the production of gallium?
(Reduction using carbon, electrolysis)
(ii) If gallium chloride (GaCl₃) is electrolysed, what is the product formed at the cathode. Write the chemical equation.
(iii) Write the subshell electron configuration of the outermost shell of gallium.
Answer:
(i) Electrolysis. Gallium is a highly reactive metal.
(ii) Gallium metal.
Ga³⁺ + 3e^– → Ga
(iii) 4s² 4p¹ (Atomic number: 31)

Question 6.
Corrosion is a process by which iron is converted into its oxide. This is an oxidation reaction.
(i) What is oxidation?
(ii) Complete the following chemical equation.
….Fe + …O₂ → ..Fe₂O₃
(iii) Suggest two methods for preventing the corrosion of iron.
Answer:
(i) The process involving loss of electrons in a chemical reaction is called oxidation.
(ii) 4Fe + 3O₂ → 2Fe₂O₃
(iii)

1. Painting or coating
2. Galvanization

Question 7.
Alloys containing iron are given. Find a, b, c, d.

Alloys	Constituent elements	Uses
Alnico	(a)	(b)
(c)	Fe, Cr, Ni, C	Resist the corrosion of iron. Making of utensils
Silicon steel	Fe, Si, C	(d)

Answer:
(a) Fe, Al, Ni, CO
(b) For the manufacture of permanent magnets
(c) Stainless steel
(d) Also known as electrical steel. As it reduces electric loss, it is used in the core of electromagnetic instruments like motors, generators, transformers etc.

Chemistry Class 10 Chapter 6 Notes Kerala Syllabus Metals

Question 1.
Metals are used in many forms in different fields of our life. Try to find some of them and complete the table.

Answer:

Transport sector	Cars, cycles. Trains. Buses. Airplanes. Ships, Trucks
Agricultural sector	Agricultural tools, tillers. Tractors. Combine harvesters, ploughs. Watering cans
Construction sector	Buildings, bridges, pipes. Steel beams. Nails. Screws. Cranes
Technology sector	Phones, laptops, electrical wires. Microchips. Computer casings. Circuit boards
Consumer goods	Jewellery, household articles. Utensils, Appliances. Furniture. Coins

Question 2.
Which metals are. mostly used in these situations? List them.
Answer:
Iron, Gold, Steel, Aluminium, Copper, Silver, Platinum
Metals are used in various fields because of some of their common properties.

Question 3.
What properties of metals are utilised in various fields?
Answer:

• Sonority
• Ductility
• High melting point
• Thermal conductivity
• Malleability
• Metallic lustre
• Hardness

Question 4.
The nature of ores is given. Complete the table using appropriate concentration methods.

Answer:

Nature of ore	Concentration method
1. Ores are less dense than the impurities	Froth floatation
2. Ores have magnetic properties but impurities are non magnetic	Magnetic separation
3. A solvent which dissolves the ore is used.	Leaching
4. Ores are denser than the impurities.	Levigation or Hydraulic washing

Question 5.
How are metals arranged in the reactivity series?
Decreasing order of reactivity / increasing order of reactivity
Answer:
Decreasing order of reactivity
Here are some metals in the reactivity series.

Mercury can be easily separated from its ores by controlled heating.

Metals with comparatively moderate reactivity like, are generally found as oxides, sulphides or carbonates.
Eg. ZnCO₃, ZnS, Fe₂O₃, SnO₂, PbS
There are two stages for the production of metal from them.

1. Conversion of concentrated ore to oxide
Two methods are commonly used for this.

(a) Calcination
Metal carbonates or hydroxides are converted to their oxides by a process called calcination.

Calcination refers to heating the concentrated ore in limited quantities or absence of air at a temperature below the melting point.

Eg. CaCO₃(s) CaO(s) + CO₂(g)
ZnCO₃ (s) ZnO(s) + CO₂ (g)

(b) Roasting

Roasting refers to heating the concentrated ore at a temperature below the melting point in the presence of air.

Zinc sulphide and lead sulphide can be easily

c) converted into their oxides by this method
2ZnS(s) + 3₂ (g) 2ZnO(s) + 2S₂ (g)
2PbS (s) + 3₂ (g) 2PbO (s) + 2S₂ (g)

When the concentrated ore is subjected to roasting, the water content in them gets released as vapours. They become pure and moisture free oxide ores.

2. Reduction of oxide ore
The metal part of the ores is in the form of positive ions, and hence it can be extracted by a reduction process.

Question 6.
Note the process that separates zinc from zinc oxide.
ZnO + C → Zn + CO
Which is the reducing agent in this case?
Answer:
Carbon
Reducing agents such as coke (an allotrope of carbon) and carbon monoxide are used to extract moderately reactive metals such as iron, zinc and tin from their oxide ores. Carbon has a greater tendency to react with oxygen at high temperatures, so oxygen is easily removed from the ore.

Strong reducing agents are required to extract highly reactive metals such as sodium, potassium, calcium, magnesium and aluminium from their ores. Such metals are produced by electrolysis.

Question 7.
Complete the table regarding the manufacture of metals.

Answer:

Method of separating metals from ores	Metals
Electrolysis	Sodium, Potassium, Calcium, Magnesium and Aluminium
Reduction using coke	Iron, Zinc and Tin
Heating in controlled ways	Mercury

Question 8.
The order of reactivity of some metals is given.
Al > Zn > Fe > Au
a) Which metal forms the most stable compound?
Answer:
Aluminium

b) Which metal is produced by electrolysis?
Answer:
Aluminium

c) Which metal can displace zinc from compounds of zinc? Why?
Answer:
Aluminium can displace Zinc from its compounds. A metal can displace another from a compound if it is more reactive. Since A1 is higher than zinc in the reactivity series, it can displace Zinc.

d) Which metal is found in the free state in nature?
Answer:
Gold (Least reactive one)

e) Which metal is produced by reduction using carbon?
Answer:
Zinc and Iron

Question 9.
Complete the table regarding the manufacture of iron.

Answer:

Ores of iron and its chemical formula	Haematite (Fe2O3) Magnetite (Fe3O4)
Methods used for concentration	Washing in stream of water, roasting. Magnetic separation
Substance used to reduce the ore	Carbon (Coke)

Iron is produced in steel towers, known as blast furnaces, which are 25 to 30 meters high. Its interior is lined with bricks (Refractory bricks) capable of withstanding high temperatures

The concentrated ore mixed with limestone ( CaCO₃) and coke (C) is fed from the top of the furnace via cup and cone arrangement. This mixture is called charge.

A blast of hot air is blown into the furnace from its bottom. As the charge descends from the top of the furnace, various chemical changes take place inside it. The coke combines with the oxygen in the air, when the blast of hot air flows from the bottom to the top of the blast furnace.
C + O₂ → CO₂ + heat
This is an exothermic reaction. Coke reacts with carbon dioxide to produce carbon monoxide. This is an endothermic reaction.
CO₂ + C+ heat → 2CO
The main chemical reaction taking place in the blast furnace is the reduction of iron ore using carbon monoxide.
Fe₂O₃ + 3CO → 2Fe + 3CO₂
Even though the iron ore fed into the furnace is in the most refined form, it may contain acidic impurities such as sand (silica SiO₂) that cannot be removed in the first stages of concentration methods. For this, a substance known as flux is added during the metallurgical stage. As the impurities are acidic in nature, a basic substance is used as the flux. The flux combines with gangue to form molten slag.
Gangue + Flux → Slag
When heated at high temperature, the limestone decomposes to calcium oxide (Quick lime). Calcium oxide produced in this reaction acts as flux.
The chemical changes of limestone inside the blast furnace.
CaCO₃ CaO(s) + CO₂(g)
Calcium oxide reacts with sand (SiO₂) to form calcium silicate (slag), which melts easily.

If the gangue in the ore is basic in nature, acidic flux should be used.

Since the molten slag is less dense, it floats on the molten iron. These are removed at regular intervals through a separate tube/ tap. This slag is used in the production of cement and in the construction of roads.

The molten iron obtained from the blast furnace contains 4% carbon and small amounts of other impurities such as manganese, silicon, phosphorus and sulphur. This is called pig iron.

If the percentage of impurity in it is reduced, the iron obtained can be cast as desired. It is called cast iron. It contains more than 2% carbon.

Wrought iron is a relatively pure form of iron, containing 0.02% – 0.05% carbon and small amounts of phosphorus, silicon, manganese, sulphur etc.

Question 10.
Prepare a list of different types of steels, their methods of manufacture and use. ICT can be utilised.
Answer:

• Tool Steel: Contains elements like tungsten, molybdenum, and cobalt to increase hardness, heat resistance, and wear resistance. It is used for tools, dies, and cutting instruments.
• Structural Steel: Used in construction and contains manganese to improve strength. It is used in buildings, bridges, and other large structures.

Methods of Manufacture
The primary method for producing steel involves the following steps:

1. Blast Furnace: Iron ore is melted in a blast furnace to produce pig iron.
2. Steel Making: The pig iron is then processed in a Basic Oxygen Furnace (BOF) or an Electric Arc Furnace (EAF) to reduce carbon content and add alloying elements.
3. Casting: The molten steel is cast into various shapes, such as slabs, blooms, or billets.
4. Finishing: The cast steel is then rolled, shaped, and heat-treated to achieve the desired properties.

Alloy steel
The use of metals in their pure form is relatively less. Most of the metals are converted into alloys to be used for various purposes in daily life.

Question 11.
List the alloys familiar to you.
Answer:
Brass, Bronze, Solder, Amalgam, Duralumin
Alloys are mixtures of two or more metals. Nonmetals like carbon, nitrogen and phosphorus are also used for the production of alloys.

Question 12.
What are the constituents of steel?
Answer:
Iron, Chromium, Nickel, Carbon
Alloy steels are made by adding other metals to steel. Their properties are different from those of steel.
Some important alloy steels:

Alloy steels	Constituent elements	Properties and uses
Stainless steel	Fe, Cr, Ni, C	Resists corrosion. Manufacture of household appliances and blades.
Manganese steel	Fe, Mn, C	High hardness. Used for the manufacture of drills, safes, plates and railway tracks.
Silicon steel	Fe, Si, C	Also known as electrical steel. As it reduces electric loss, it is used in the core of electromagnetic instruments like motors, generators, transformers etc.

Question 13.
Expand the list by finding more alloys, their constituents and uses.
Answer:

Alloy steels	Constituent elements	Properties	Uses
Alnico	Fe, Al, Ni, Co	Magnetic nature	For the manufacture of permanent magnets
Nichrome	Fe, Ni, Cr, C	High resistance	For making heating coils

Question 14.
Complete the table regarding the production of zinc.

Answer:

Sulphide ore of zinc (Common name, chemical formula)	Zinc blende (ZnS)
Concentration method	Froth floatation
Carbonate ore of zinc (Common name, chemical formula)	Calamine (ZnCO3)

Question 15.
What are the processes used in the conversion of zinc ore to zinc oxide after the concentration of ore?
Answer:
Roasting. Zinc sulphide can be easily converted into their oxides by this method.
2ZnS (s) + 3O₂(g) 2ZnO(s) + 2SO₂ (g)

When the concentrated ore is subjected to roasting, the water content in them gets released as vapours. They become pure and moisture free oxide ores.

Coke is mixed with the zinc oxide obtained after these processes.

This mixture is put into a furnace similar to a blast furnace. At high temperature in the furnace, the coke reduces zinc oxide to zinc.

ZnO (s) + C (s)Zn(s) + CO (g)
Zinc has comparatively low boiling point (907°C) and hence it vapourises at high temperature and comes out. It is immediately cooled to liquid form.

Question 16.
You are familiar with the purification process of zinc. What is it known as?
Answer:
Distillation
Brass is an important alloy containing zinc.

Question 17.
Prepare a note on the production of zinc and its use. Record it in the science diary.
Answer:
Production and Use of Zinc
Zinc is primarily produced from the mineral sphalerite through a process that involves roasting, followed by either electrolysis or smelting. Its main use is for galvanizing to protect steel and iron from rust. It is also used in alloys like brass, in die-casting, and for batteries.

Question 18.
What method of concentration is suitable for these sulphide ores?
Answer:
Froth floatation

Question 19.
The ore contains basic impurities such as iron oxide even after concentration. What type of flux is suitable to remove it? (Acidic / Basic)
Answer:
Acidic flux
Sand (SiO₂) having acidic nature is added to the ore and heated to form cuprous sulphide (Cu₂S) of maximum purity. It is partially converted to cuprous oxide (Cu₂O) when heated under controlled flow of air. The cuprous oxide converts the remaining cuprous sulphide into copper.

Note that no reducing agent is added here. Molten copper is cooled in moulds. The copper lumps thus obtained are called blister copper. The sulphur dioxide gas produced during the production of copper is released when the metal condenses. As a result blisters are formed and they appear as such on the surface of copper lumps.

Question 20.
Brass and bronze are important alloys that contain copper. List the constituent metals in them.
Answer:
Brass is an alloy of copper and zinc. Bronze is traditionally an alloy of copper and tin.

Purification of Copper
The method of refining copper is electrolytic refining. Copper used for electrical purposes should be 99.99% pure. A high quality product is obtained through electrolytic refining. The diagram of refining of copper is given.

Question 21.
Observe the diagram and complete the table.

Answer:

Anode	Impure Copper
Cathode	Pure copper
Electrolyte	Copper Sulphate solution with H2SO4
Chemical equation of the reaction taking place at anode.	Cu → Cu2+ + 2e–
Chemical equation of the reaction taking place at cathode.	Cu2+ + 2e– → Cu

Question 22.
Prepare a note on the process involved in the purification of copper and record it in the science diary.
Answer:
Copper is purified using electrolytic refining. Impure copper acts as the anode (positive electrode) and pure copper as the cathode (negative electrode). Both are placed in a copper sulphate solution. When electricity is applied, copper from the anode dissolves and is deposited onto the cathode, leaving impurities behind.

Question 23.
What reaction takes place at the cathode?
Answer:
Al³⁺ + 3e^– → Al

Question 24.
What reaction takes place at the anode?
Answer:
2O^2- → O₂(g) + 2e^–

Question 25.
Which gas is liberated at the anode?
Answer:
Oxygen

Question 26.
In the electrolytic cell, the positively charged carbon rods are replaced periodically. What is the reason?
Answer:
The oxygen produced at the anode will cause the carbon rods to oxidise into carbon dioxide. As a result, the size of the anode rod decreases. So, Carbon rods need to be replaced periodically.

Question 27.
Complete the – Table related to the electrolysis of alumina.

Answer:

Anode	Carbon lining
Cathode	Molten cryolite and Alumina
Electrolyte	Oxygen gas
The product formed at anode	Aluminium
The product formed at cathode	Electricity
Reducing agent	Carbon lining

Duralumin and alnico are important alloys which contain aluminium. The constituents of alnico are Fe, Al, Ni, CO etc. Alnico is used for making permanent magnets.

Question 28.
What are the factors influencing the corrosion of iron?
Answer:

• Presence of Water and Oxygen
• Presence of Electrolytes
• pH of the Environment
• Temperature

The metals occupying higher positions in the reactivity series readily corrode upon contact with atmospheric air. The rate of corrosion decreases as we move down. Metals higher up the reactivity series are more electropositive, meaning they have a greater tendency to lose electrons and form positive ions. Corrosion, or oxidation, is the process where a metal loses electrons. Therefore, more reactive metals readily lose electrons to elements in the atmosphere, like oxygen and water, causing them to corrode faster than less reactive metals.

Even though aluminium is a metal at the top of the reactivity series, it resists corrosion to some extent. Aluminium’s corrosion resistance stems from its immediate reaction with atmospheric oxygen to form a thin, durable, and non-porous layer of aluminium oxide (Al₂O₃) on its surface. This protective layer acts as a barrier, preventing further oxidation and corrosion of the metal beneath. The oxide coatings on metals such as aluminium, zinc and tin are thin and nonporous and therefore protect the metal from further corrosion.

The corrosion of iron differ from this, because the hydrated iron oxide (rust) that forms on the surface of iron is porous and powdery. So this process of corrosion continues until the metal is destroyed.

The factors given below influence the corrosion of metals.?

• Nature of the metal
• Moisture in which gases or salts are dissolved
• Contact with other metals

Question 29.
Let us do an experiment.

Prepare a very dilute solution of sodium chloride in two large test tubes. Place iron nails, one tightly wrapped with copper wire and the other with magnesium wire. Observe the test tube for five to six days. Record the results of the observation in the science diary.

a) In which test tube, the iron nail undergoes rusting?
Answer:
The iron nail in contact with copper.

b) It is found that the iron nail in contact with copper corrodes easily while that in contact with magnesium is protected. Why does this happen?
Answer:
When a metal comes in contact with another metal in the presence of an electrolyte, it acts as a simple voltaic cell. This phenomenon is due to galvanic corrosion, an electrochemical process. When iron is in contact with copper, the more reactive iron acts as the anode and corrodes to protect the copper, the cathode. Conversely, when in contact with magnesium, the highly reactive magnesium acts as a sacrificial anode, corroding preferentially and preventing the less reactive iron from rusting.

c) When iron comes into contact with copper, which metal will release electrons? Why?
Answer:
When iron comes into contact with copper, iron will release electrons. This is because iron is more reactive than copper, meaning it has a greater tendency to lose electrons. As a result, in the presence of an electrolyte, iron becomes the anode and corrodes, while copper acts as the cathode and is protected from corrosion.

The iron atoms, that lose electrons, change into ions. The rate of corrosion of iron increases. Here iron acts as anode and copper acts as cathode.

d) Why is iron protected when it is in contact with magnesium?
Answer:
It is because the more reactive magnesium donates electrons. In the cell formed here, magnesium acts as anode and iron as cathode.

Question 30.
Which metal will corrode when two metals are in contact in the presence of moisture in the air?
The more reactive / The less reactive
Answer:
The more reactive
It is seen that the metal acting as anode is destroyed and the metal acting as cathode is protected. This is an important method to prevent corrosion of iron. This is known as cathodic protection.

Question 31.
Why is it not advisable to join aluminium wires and copper wires, and to join iron materials to copper piping
for electrical purposes?
Answer:
Joining aluminium and copper wires or iron and copper pipes is a bad idea due to galvanic corrosion and thermal expansion.

• Galvanic Corrosion: When in contact, the more reactive metal (aluminium or iron) corrodes faster to protect the less reactive one. This increases resistance and can cause fires.
• Thermal Expansion: Aluminium expands more than copper when heated. This difference can loosen the connection over time, increasing fire risk.

Question 32.
Why are zinc or magnesium blocks always attached to sea bridges and ship hulls?
Answer:
Zinc or magnesium blocks are attached to ships and bridges as sacrificial anodes. Being more reactive than steel, they corrode instead of the structure, providing cathodic protection.

Question 33.
Discuss various methods to prevent corrosion of metals and list them in the science diary.
Answer:
To prevent corrosion, you can:

• Coat the metal with paint or oil.
• Use a sacrificial coating, like galvanizing steel with zinc.
• Create alloys like stainless steel.
• Use cathodic protection with sacrificial anodes or electric current.
• Electroplate with a non-corrosive metal.

Metals play a crucial role in the human body also. We can learn more about it in the higher classes.

Std 10 Chemistry Chapter 6 Notes – Extended Activities

Question 1.
Thermite process

Mix equal amounts of anhydrous aluminium powder and iron oxide in a crucible. Immerse it in a tin pot filled with sand. Place a little of barium peroxide and magnesium powder mixture on top of the first mixture. Fix a 6 cm long polished magnesium ribbon in slanting position on its top. After lighting the ribbon, watch it from a distance.

After the reaction stops, examine the crucible and you will find a small globule of iron.
Fe₂O₃ + 2Al Al₂O₃ + 2Fe
a) Analyse the chemical changes that took place here based on the metallurgical process.
b) Find instances where thermite process is used in daily life.
c) Write the chemical equation for the production of chromium from chromic oxide (Cr₂O₃) in this way.
Answer:
a) The thermite process is a redox reaction. The aluminium powder acts as a strong reducing agent because it is more reactive than iron. It has a greater tendency to lose electrons and combine with oxygen. Aluminium reduces the iron oxide (Fe₂O₃) to molten iron (Fe), while the aluminium itself gets oxidised to aluminium oxide (Al₂O₃). The reaction is highly exothermic, releasing a large amount of heat that melts the iron. The barium peroxide and magnesium ribbon mixture acts as an igniter to initiate this high-temperature reaction.

b) The thermite process is utilised in daily life for its ability to produce extremely high temperatures and molten metal quickly. Common uses include:

Thermite Welding: It is widely used to weld railway tracks and other large metal parts in situ, as the process can generate molten iron to join the ends of the metal sections.

Demolition and Cutting: The intense heat from the reaction can be used to cut through thick metal plates.

c) The chemical equation for the production of chromium from chromic oxide (Cr₂O₃) using the thermite process is:
Cr₂O₃ + 2Al → Al₂O₃ + 2Cr
In this reaction, aluminium acts as the reducing agent, reducing the chromic oxide to pure chromium metal.

Question 2.
Prepare a note on how the rusted iron materials collected from the scrap iron shop are used in making steel. Present it in the class.
Answer:
Using Rusted Iron to Make Steel
Rusted iron from scrap yards is recycled into new steel through a process that primarily uses an electric arc furnace (EAF).

1. Melting: The scrap is placed in a high- temperature EAF, where the rust (iron oxide) and other impurities are melted.
2. Purification: Impurities like silicon and manganese are oxidised and then removed as slag.
3. Carbon and Alloying: Once purified, specific amounts of carbon and other elements (like chromium or nickel) are added to the molten iron to give it the desired properties of steel.
4. Casting: The new molten steel is then cast into various shapes for use in manufacturing.
   This process efficiently recycles metal, reducing the need for new iron ore mining and making steel production more sustainable.

Question 3.
Prepare a flow chart showing the various steps in the purification of bauxite.
Answer:

Metals Class 10 Notes

Metals Notes Pdf

• Minerals – The metallic compounds generally seen in the earth’s crust.
• Ores – A mineral from which a metal is economically, easily and quickly extracted.
• 3 Steps in metallurgy:
  1. Concentration of ores (removing impurities (gangue) from ore)
  2. Extraction of metals
  3. Refining of metals (Other metals, metal oxides, and small amounts of non-metals may be impurities in reduced metal. Metal refining removes impurities to make pure metal.)
• Concentration of ores
  1. Levigation (Gangue – Lighter, Ore – Heavier)
  2. Froth floatation (Gangue – Heavier, Ore – Lighter)
  3. Magnetic separation (Either ore or Gangue has magnetic nature)
  4. Leaching (when ore particles are soluble in suitable solution)
• Extraction of metals
  a) Conversion of the concentrated ore into its oxide.
  i) Calcination (Heating the ore at a temperature below its melting point in absence of air)
  ii) Roasting (Heating the ore at a temperature below its melting point in presence of air)
  b) Reduction of the oxide.
  Extraction of metal from the oxide.
• Refining of metals
  1. Liquation – Low melting metals
     Ex: Tin & Lead
     (Heating metals on an inclined surface)
  2. Distillation – Metals with low boiling points Zinc, Cadmium, Mercury
  3. Electrolytic Refining – Electrolysis (electrolyte – Solution of salt of metal, -ve electrode – small piece of pure metal, +ve electrode – impure metal)
• Industrial production of Iron
  Ore – Haematite –
  
  The chemical reactions taking place in blast furnace
  C + O₂ → CO₂ + Heat
  CO₂ + C + Heat → 2CO
  Fe₂O₃ + 3CO → 2Fe + 3CO₂
  CaCO₃ → CaO + CO₂
  CaO + SiO₂ → CaSiO₃
  Flux + Gangue → Slag
• Extraction of Zinc

Sulphide ore of zinc (Common name, Chemical formula)	Zinc blende (ZnS)
Concentration method	Froth floatation
Carbonate ore of zinc (Common name, Chemical formula	Calamine (ZnCO3)

The concentrated ore is subjected to roasting. Zinc sulphide converted to Zinc Oxide. Then Coke is mixed with Zinc oxide and put into furnace at high temperature, the coke reduces Zinc oxide to Zinc
Purification method of Zinc – Distillation

• Extraction of Copper – Copper is extracted from copper pyrites (CuFeS₂) through a process of concentration by froth flotation, followed by roasting and smelting with silica to remove iron as slag, which ultimately yields impure blister copper that is refined by electrolysis to obtain a high purity metal.
• Extraction of Aluminium – Aluminium is extracted from its ore, bauxite, in a two-stage process: first process purifies the bauxite to produce pure alumina (Al₂O₃), which is then dissolved in molten cryolite (Na₃ AlF₆) and reduced to pure aluminium metal by electrolysis in the Hall-Heroult process.
• Corrosion of metal is a process in which the metal reacts with a surrounding medium and undergoes chemical change.
• The factors given below influence the corrosion of metals move left.
• Nature of the metal
• Moisture in which gases or salts are dissolved Contact with other metals

INTRODUCTION

The use of metals accelerated the growth of people and the birth of an original culture. The discovery of metals and their role in human progress is amazing. The term ‘metal age’ refers to the transition period from the Stone Age to the use of metals. Our ancient period is marked by the names Copper Age, Bronze Age, Iron Age, etc. At present, metals are used in the making of a wide range of products, ranging from small paper screws to large-scale machinery. The unique features of each metal make them important in different fields.

Occurrence of metals in nature

• Naturally occurring metals or compounds are generally called minerals. These include metallic compounds and non metallic compounds.
• Any mineral from which a metal can be extracted easily and economically is called an ore of that metal.

Metallurgy

• The process of extraction of metal from ores involves three major stages. Such processes are generally referred to as metallurgy.
  1. Concentration of ores
  2. Extraction of metal from concentrated ore
  3. Refining of metal
• Concentration of ores is the process of increasing the metal content of the ore by removing impurities, known as gangue.
• Concentration methods include Levigation or Hydraulic washing, Froth floatation, Magnetic separation and Leaching. These methods are adopted depending on the nature of the ore and gangue.
• Extraction of metal from concentrated ore – 1. Conversion of concentrated ore to oxide, 2. Reduction of oxide ore
• Calcination refers to heating the concentrated ore in limited quantities or absence of air at a temperature below the melting point.
• Roasting refers to heating the concentrated ore at a temperature below the melting point in the presence of air.
• Refining of metals is the process of removing the impurities to produce pure metal. Refining methods include Liquation, Distillation and Electrolytic refining and these are adopted depending upon the metal to be purified and impurities contained in it.

Manufacturing methods of some industrially important metals

• Extraction of Iron – Iron is extracted from its iron oxide ores, such as haematite, in a blast furnace by reducing the iron oxide with carbon at high temperatures, which separates the iron from the oxygen.
• Extraction of Zinc – Zinc is extracted from its ores, primarily zinc sulphide (ZnS), by first converting the ore to zinc oxide (ZnO) through roasting, then reducing the oxide with carbon in a furnace at high temperatures, and finally purifying the resulting metal.
• Extraction of Copper – Copper is extracted from copper pyrites (CuFeS₂) through a process of concentration by froth flotation, followed by roasting and smelting with silica to remove iron as slag, which ultimately yields impure blister copper that is refined by electrolysis to obtain a high purity metal.
• Aluminium is extracted from its ore, bauxite, in a two-stage process: first process purifies the bauxite to produce pure alumina (Al₂O₃), which is then dissolved in molten cryolite (Na₃ AlF₆) and reduced to pure aluminium metal by electrolysis in the Hall-Heroult process.

Corrosion of metals

• Corrosion of metal is a process in which the metal reacts with a surrounding medium and undergoes chemical change.
• The factors given below influence the corrosion of metals.
  • Nature of the metal
  • Moisture in which gases or salts are dissolved
  • Contact with other metals

OCCURRENCE OF METALS IN NATURE
The earth’s crust is the major source of metals. Metals are generally found in combined state as they are highly reactive. Metal compounds like sodium chloride and magnesium chloride are dissolved in sea water also. A very few metals are seen in free state too. The most common examples include Gold (Au), Platinum (Pt), Silver (Ag).

Naturally occurring metals or compounds are generally called minerals. These include metallic compounds and non metallic compounds.

The same metal can be found in the form of various minerals in nature. Metals are separated from the most suitable ones among these. For example, clay (Al₂O₃.2SiO₂.2H₂O) is an abundant mineral of aluminium. Bauxite
(Al₂O₃.2H₂O) and cryolite (Na₃AlF₆) are also minerals of aluminium. But among these, bauxite is the mineral that is commonly used to produce aluminium.

The qualities of a mineral that is used to extract a metal

• Abundance
• Ease of extraction
• High metal content
• Low production cost.

Based on these characteristics, bauxite is the most suitable mineral for the production of aluminium.
The ores of some metals are listed in the Table

Any mineral from which a metal can be extracted easily and economically is called an ore of that metal.

METALLURGY
Highly reactive metals are found in nature in combined form.
The process of extraction of metal from ores involves three major stages. Such processes are generally referred to as metallurgy.
1. Concentration of ores
2. Extraction of metal from concentrated ore
3. Refining of metal

CONCENTRATION OF ORES
Ores are mined from the earth’s crust. A lot of earthy impurities like soil and sand may be mixed with this. Concentration of ores is the process of increasing the metal content of the ore by removing such impurities, known as gangue. Depending on the nature of the ore and gangue, various methods are adopted for this purpose.

a) Levigation or Hydraulic washing
This method is employed when the density of the ore is more than that of the gangue. The powdered ore is washed in a stream of water. The less dense gangue, which floats, is filtered out. The more dense ore remains at the bottom. Generally, oxide ores can be concentrated by this method.

b) Froth floatation
The froth floatation process is used when the ore is less dense than the gangue. The powdered ore is added to a mixture of water and pine oil and is stirred in a strong current of air. The ore particles stick to the froth formed, and float. It is removed and then the ore is separated and dried. Generally, sulphide ores are concentrated by this method.

c) Magnetic separation
When the powdered ore is passed through a magnetic roller, either the ore or the impurities having magnetic property is separated. In this way, pure ore is obtained by magnetic separation.

For example, magnetite (Fe₃O₄) ore has magnetic properties, but the gangue is non magnetic. Tinstone (SnO₂) ore is non magnetic, but iron tungstate, the gangue present in it is magnetic.

d) Leaching
The powdered ore is mixed with a suitable solvent. The ore dissolves in it or undergoes a chemical reaction to become a solution. The gangue remains insoluble in it. It is then filtered out. This process is called leaching.

Bauxite, the ore of aluminium, is concentrated in this way.

Metals such as gold and silver occur almost freely in nature. The ores of these metals are leached with a dilute solution of sodium cyanide (NaCN) or potassium cyanide (KCN) in the presence of air to extract the metals.

EXTRACTION OF METAL FROM CONCENTRATED ORE
You have learnt that the reactivity of metals differ. You also know about the reactivity series that is prepared based on this.

REFINING OF METALS
The metal extracted from concentrated ore may contain other elements or their compounds as impurities. Refining of metals is the process of removing these impurities to produce pure metal.

Various methods are adopted for this purpose depending upon the nature of the metal to be purified and the impurities contained in it. Some are given below.

(a) Liquation: When metals with low melting point contain impurities with high melting point, the metal is heated on the inclined surface of the furnace. The pure metal separates from the impurities, melts, flows down and it is collected. This is known as liquation. Metals such as tin (Sn) and lead (Pb) having low melting point can be purified by this method.

(b) Distillation: This method is used to purify metals with relatively low boiling points. When the metal containing impurities is heated under suitable conditions, only the pure metal vapourises. When this vapour condenses, pure metal is obtained. Metals like zinc (Zn), cadmium (Cd) and mercury (Hg) can be purified using this method.

(c) Electrolytic refining: In an electrolytic cell, an impure metal is used as the anode and a thin piece of pure metal is used as the cathode. A suitable salt solution of the same metal is used as the electrolyte. When electric current is passed, the pure metal alone is separated from the anode and deposited at the cathode.
Anode: M → Mⁿ⁺ + ne^–
Cathode : Mⁿ⁺ + ne^– → M
(Hint: M – metal, n – number of electrons involved in the reaction)
Copper (Cu) and zinc (Zn) can be purified in this way.

MANUFACTURING METHODS OF SOME INDUSTRIALLY IMPORTANT METALS
EXTRACTION OF IRON
Iron comprises about 5% of the earth’s crust and it is the second most abundant metal.

Steel
The pig iron obtained from the blast furnace is not suitable either for hammering into various shapes or for drawing into wires. The steel obtained from this is used for various industrial purposes. Steel is iron containing 0.05% to 1.5% carbon. There are different types of carbon steels depending on the amount of carbon. They differ in properties also.

Carbon steel	Amount of carbon (%)	Features
Mild steel	0.05 – 0.2	Easy to draw into wires and hammer into plates. Strong and hard. Used for making agricultural tools.
Medium steel	0.2 – 0.6	High hardness. Used for the construction of railway tracks, handrails, rafters etc.
High carbon steel	0.6 – 1.5	Very high elasticity and hardness. Used for the manufacture of surgical instruments, springs, knives, drills etc.

EXTRACTION OF ZINC
Zinc is another industrially important metal.

EXTRACTION OF COPPER
Principal ores of copper
Copper pyrites – CuFeS₂ Copper glance – Cu₂S

EXTRACTION OF ALUMINIUM
Aluminium is produced by Hall-Heroult process.
It has two stages.

1. Concentration of bauxite
Bauxite is concentrated by leaching. The powdered ore is treated with hot concentrated
sodium hydroxide (NaOH) solution. The ore alone dissolves in it to form sodium aluminate
(NaAlO₂) solution. Impurities are then filtered off.
Al₂O₃.2H₂O + 2NaOH → 2NaAlO₂ + 3H₂O

A little aluminium hydroxide (Al(OH))₃ is added to the solution of sodium aluminate and stirred vigorously. It is diluted by adding water. As a result, pure aluminium hydroxide separates out from the solution.
NaAlO₂ + 2H₂O → Al(OH)₃ + NaOH
If the aluminium hydroxide thus obtained is heated strongly, anhydrous alumina (Al₂2O₃) is obtained.
2Al(OH)₃ Al₂O₃ + 3H₂O

2. Electrolysis of aluminium oxide
Molten cryolite (Na₃AIF₆) is added to the alumina, obtained after concentration, to get a solution. This is the electrolyte used in the production of aluminium. The melting point of alumina is 2017°C. Cryolite is added to reduce the melting point and to increase the electrical conductivity.

Aluminium is separated at the cathode when a high voltage electric current is passed through the molten mixture. Examine the chemical equations of the reactions.
Al₂O₃ → 2Al³⁺ + 3O^2-

CORROSION OF METALS
Corrosion of metal is a process in which the metal reacts with a surrounding medium and undergoes chemical change.