2. As History Tells Us
Stone Age and Bronze Age:
Humans have used metals for thousands of years.
Gold and silver, found as native metal, were used as
jewellery. These metals were known in the Stone Age but
gold and silver are too soft to be used as tools. The first
really useful metallic alloy to be discovered was bronze in
the Bronze Age. Bronze is not an element (like gold and
silver) but an alloy (metal mixture) of copper and tin.
Bronze was used extensively for tools and weapons.
3. As History Tells Us
Iron Age:
After the Bronze Age came the Iron Age.
People discovered that a high temperature coal
fire could be used for the extraction of iron from
iron ore. The discovery of electricity at the
beginning of the nineteenth century allowed the
extraction of the more reactive metals.
Aluminium has been extracted on a large scale
since about 1870.
4. Some Terms – Lets Have a Look
Minerals: A solid element or compound which
occurs naturally in the Earth's crust is called a
mineral.
Ore: A mineral from which metals can be extracted
profitably is called a metal ore. Profitable extraction
means that the cost of getting the metal out of the
ore is sufficiently less than the amount of money
made by selling the metal. So All Ores Are Minerals
But All Minerals Are Not Ores.
The most common metal ores are oxides and
sulphides. Metals are obtained from their ores by
reduction.
5. Be Aware!!
Metal ore deposits are a finite resource (there are
only a certain amount of them) and non-renewable
(once used, they are gone and will not be
replaced). Many metals are obtained today from
recycling (melting and refining) scrap metals.
Native Metals: Gold and platinum occur in the
Earth as native metal, which means that they are
found as the element, not the compound, and so do
not need to be reduced. Silver and copper may also
be found as native metal.
6. Occurrence of Iron
Iron is very reactive and is found in nature in form of
its oxides, carbonates and sulphates. The main
ores are:
i) Haematite (Fe2O3)
ii) Magnetite (Fe3O4)
iii) Iron Pyrites (FeS2)
o The main iron ore is Haematite (iron (III) oxide -
Fe2O3).
o The iron ore contains impurities, mainly silica
(silicon dioxide).
o Since iron is below carbon in the reactivity
series, iron in the ore is reduced to iron metal by
heating with carbon (coke).
7. Extraction of Iron
Step1: Concentration
The ore is crushed in crushers and is
broken to small pieces. It is concentrated with
gravity separation process in which it is
washed with water to remove clay, sand, etc.
8. Steps of Extraction
Step1: Concentration
Step2: Calcination
The ore is then heated in absence of air
(calcined). This results in decomposition of carbonates
into oxides and then ferrous oxide is converted into
Ferric Oxide.
3
2
2
2
3
CO
Fe
2
O
FeO
4
CO
FeO
FeCO
9. Steps of Extraction
Step1: Concentration
Step2: Calcination
Step3: Smelting
The concentrated ore is mixed with
calculated quantity of coke, limestone and the
mixture is put in the Blast Furnace from top.
10. Blast Furnace
It is a tall cylindrical furnace
made of steel.
It is lined inside with fire
bricks.
It is narrow at the top and has
an arrangement for the
introduction of ore and outlet for
waste gases.
Heated with help of Hot Gases.
11. Chemical Reactions
Following Chemical Reactions Take Place in a
Blast Furnace
i) Formation of Carbon Monoxide:
Near the bottom of the furnace, coke burns in air to
form Carbon Dioxide and a lot of heat is produced.
We get a temperature of about 1875 K.
This CO2 further reacts with more coke and is
reduced to CO.
CO
CO
C
Heat
CO
O
C
2
2
2
2
12. Chemical Reactions
ii) Reduction of Haematite to Iron:
In the upper part of the furnace, the temperature is
between 975K to 1075K. Here Haematite is
reduced to Iron by CO. This molten Iron is
collected at the bottom of the furnace.
2
3
2
CO
3
Fe
2
CO
3
O
Fe
13. Functions of Limestone
1. It acts as flux to remove sand from Haematite in form
of liquid Slag. In the middle of the furnace, the
temperature is about 1075-1275 K. Here Limestone
decomposes to produce calcium oxide (CaO) and
CO2.This CaO reacts with reacts with silica (sand)
present in the ore to form slag(CaSiO3).
2. Slag is lighter than molten iron so it floats over
molten iron and protects it from oxidising back into its
oxides.
3
2
2
3
CaSiO
SiO
CaO
CO
CaO
heat
CaCO
14. Commercial Forms of Iron
There are three major commercial forms of Iron.
They differ in their carbon content.
1. Cast Iron (or Pig Iron)
It contains 2-5% Carbon along with traces of other
impurities like Sulphur, Phosphorus, Manganese
etc.
2. Wrought Iron
It is the purest form of Iron and contains carbon to
the extent of 0.25%
3. Steel
It contains 0.5 to 1.5 % of carbon along with varying
amount of other elements.
15. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
16. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
17. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
18. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
19. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
20. Testing Zone..
Match the following:
a) Haematite a) Extraction of Iron
b) Calcination b) Ore of Iron
c) Smelting c) CaSiO3
d) Slag d) Acts as Flux
e) Lime Stone e) Type of Iron
f) Heating in absence of air.
21. Testing Zone..
Mark True of False
1. Metals can be extracted profitably from ores.
2. All minerals are ores.
3. Chief ore of Iron is Iron Pyrites.
4. Iron is reduced with the help of Coke.
5. Slag is formed by reaction between CaCO3 and SiO2
22. Testing Zone..
Mark True of False
1. Metals can be extracted profitably from ores. (True)
2. All minerals are ores. (False)
3. Chief ore of Iron is Iron Pyrites. (False)
4. Iron is reduced with the help of Coke. (True)
5. Slag is formed by reaction between CaCO3 and SiO2.
(False)
23. Testing Zone..
Choose the right Answer out of
The given choices:
Ques1: The actual reducing agent in Blast Furnace is:
A) Coke
B) Carbon Dioxide
C) Carbon Monoxide
D) Iron
24. Testing Zone..
Choose the right Answer out of
The given choices:
Ques1: The actual reducing agent in Blast Furnace is:
A) Coke
B) Carbon Dioxide
C) Carbon Monoxide
D) Iron
25. Testing Zone..
Choose the right Answer out of
The given choices:
Ques2: The formula for Haematite is:
A) FeO
B) FeO2
C) Fe2O3
D) Fe3O4
26. Testing Zone..
Choose the right Answer out of
The given choices:
Ques2: The formula for Haematite is:
A) FeO
B) FeO2
C) Fe2O3
D) Fe3O4
27. Testing Zone..
Choose the right Answer out of
The given choices:
Ques3: Which is the purest form of Iron?
A) Cast Iron
B) Wrought Iron
C) Pig Iron
D) Steel
28. Testing Zone..
Choose the right Answer out of
The given choices:
Ques3: Which is the purest form of Iron?
A) Cast Iron
B) Wrought Iron
C) Pig Iron
D) Steel
29. Do it Yourself
Q 1: Name three ores of Iron
Q 2: Write the chemical reactions taking place in a blast
furnace during extraction of Iron
Q3: What are three major types of Iron. How do they
differ from each other?
Q4: Draw a neat labelled diagram of Blast Furnace.
