Aluminium: Aluminium is one of the most abundant metals found on Earth. it is silvery-white in appearance, soft and malleable in form. It is a very versatile metal used from kitchen utensils to aircraft parts. However, it has to be extracted from minerals such as bauxite and cryolite through mining. It is a very modern metal since only very recently, we have learned how to extract and utilize it. It is always used in the form of an alloy combined with other metals such as copper, manganese, magnesium, and silicon. It is extracted primarily using the Hall–Héroult process and further purified using the Hoopes process. Currently, it is used to produce aluminum cans (for soft drinks), for electrical components such as coils, wiring, and capacitors, for auto parts in aircraft, trucks, railway cars, marine vessels, bicycles, and even spacecrafts.

In this article, we will learn about a thrilling element called “Aluminium”. Let us learn more about the properties and uses of Aluminium in this article.

What is Aluminium?

Aluminium is a chemical element with a symbol of Al with an atomic number of \(13\) and an atomic mass of \(26.982\) a.m.u. This metal was first extracted in \(1827\) from Aluminium chloride by treating it with sodium: \({\rm{AlC}}{{\rm{l}}_{\rm{3}}}{\rm{ + 3Na}} \to {\rm{Al + 3NaCl}}\)

Impressed by its properties, metallurgists worldwide attempted to develop a strategy for the commercial production of Aluminium. It remained an expensive metal till \(1886\) when Heroult in France and Hall in the USA succeeded in independently developing a process for the extraction of Aluminium. Thus, large-scale production of Aluminium in several parts of the world and the Hall-Heroult process came into extensive use towards the end of the nineteenth century.

Aluminium is the third most abundant element in the Earth’s crust (\(8.3\% \) by mass). It is also the third most common chemical element after oxygen and silicon. Aluminium is a bright silvery-white metal with high tensile strength. It has a high electrical and thermal conductivity. It has a high affinity towards oxygen and forms a protective layer of oxide on the surface when exposed to air.

Properties of Aluminium

Physical Properties of Aluminium

1. Aluminium possesses a bluish-white lustre.
2. It melts at \(933\,{\rm{K}}\) and boils at \(2740\,{\rm{K.}}\)
3. It is amphoteric and corrosion-resistant.
4. Aluminium is soft, malleable, ductile, and tenacious, and can compare its tensile strength with iron and copper.
5. It is a good conductor of heat and electricity.

Chemical Properties of Aluminium

Valency

The outermost shell or the valence shell of Aluminium contains \(3\) electrons. Aluminium can give up all three electrons to form an Aluminium ion. Thus, the valency of Aluminium is \(3\), i.e., Aluminium is a trivalent metal.

The reaction of Aluminium with Oxygen (of Air)

When metal is burnt in a supply of air, the metal oxide formed by most of the metals in reaction with the oxygen of the air, the vigour of the reaction is different for each

\({\rm{Metal + Oxygen\;}} \to {\rm{Metal\;Oxide}}\)

The Aluminium metal burns on heating in air to form Aluminium oxide.

\(\mathop {{\rm{4Al}}\left( {\rm{s}} \right){\rm{\;}}}\limits_{{\rm{Aluminium}}} {\rm{\; + }}\mathop {{\rm{3}}{{\rm{O}}_{\rm{2}}}\left( {\rm{g}} \right)}\limits_{{\rm{Oxygen}}} {\rm{\;}} \to \mathop {{\rm{2A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\left( {\rm{g}} \right)}\limits_{{\rm{Aluminium\;oxide}}} {\rm{\;}}\)

Certain metal oxides like \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\) and \({\rm{ZnO}}\) are amphoteric. They show both acidic and basic behaviour. Their amphoteric nature can be shown by the reaction with both acids and alkalis.

Amphoteric nature of the Aluminium oxide

Aluminium oxide acts as a basic oxide on reaction with hydrochloric acid.
\(\mathop {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium\;oxide}}} {\rm{ + }}\mathop {{\rm{6HCl}}\left( {{\rm{aq}}} \right)}\limits_{{\rm{Hydrochloric\;acid}}}  \to \mathop {{\rm{2AlC}}{{\rm{l}}_{\rm{3}}}\left( {{\rm{aq}}} \right)}\limits_{{\rm{Aluminium\;chloride}}} {\rm{ + }}\mathop {{\rm{3}}{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( {\rm{l}} \right)}\limits_{{\rm{Water}}} \)
Aluminium oxide acts as an acidic oxide in reaction with sodium hydroxide.
\(\mathop {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium\;oxide}}} {\rm{ + }}\mathop {{\rm{2NaOH}}\left( {{\rm{aq}}} \right)}\limits_{{\rm{Sodium\;hydroxide}}}  \to \mathop {{\rm{2NaAl}}{{\rm{O}}_{\rm{2}}}\left( {{\rm{aq}}} \right)}\limits_{{\rm{Sodium\;aluminate}}} {\rm{ + }}\mathop {{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( {\rm{l}} \right)}\limits_{{\rm{Water}}}\)
Since Aluminium oxide reacts with both acid and alkali, it is amphoteric in nature.

Reaction of Aluminium with Water

Metals react with water to form a metal hydroxide and hydrogen gas. All the metals do not react with water. The intensity of the reaction of a metal with water depends on its chemical reactivity.
Metals like Aluminium, zinc, and iron do not react with either cold water or hot water. Instead, they react with steam to form a metal oxide and hydrogen.
Metal + Steam → Metal oxide + Hydrogen
\(\mathop {{\rm{2Al}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium}}} {\rm{ + }}\mathop {{\rm{3}}{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( {\rm{s}} \right)}\limits_{{\rm{Steam}}}  \to \mathop {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium\;oxide}}} {\rm{ + }}\mathop {{\rm{3}}{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right)}\limits_{{\rm{Hydrogen}}}\)
Aluminium does not react with water under ordinary conditions because of the passive layer of Aluminium oxide on its surface.

Reaction of Aluminium with Acids

The rate of reaction of a metal with acid also depends upon the nature of the acid. Thus, Aluminium reacts with dilute hydrochloric acid and dilute sulphuric acid at a reasonably fast rate. These acids are known as strong acids. On the other hand, Aluminium reacts with weak acids, such as phosphoric acid and acetic acid, very slowly.

\({\rm{2Al\;\; + \;\;6HCl\;}} \to \mathop {{\rm{2AlC}}{{\rm{l}}_{\rm{3}}}{\rm{\;}}}\limits_{{\rm{Aluminium\;chloride}}} {\rm{ + \;3}}{{\rm{H}}_{\rm{2}}}{\rm{\;}}\left( {{\rm{rapid}}} \right)\)
\({\rm{2Al\; + \;2}}{{\rm{H}}_{\rm{3}}}{\rm{P}}{{\rm{O}}_{\rm{4}}}{\rm{\;}} \to \mathop {{\rm{2AlP}}{{\rm{O}}_{\rm{4}}}}\limits_{{\rm{Aluminium\;phosphate}}} {\rm{ + \;3}}{{\rm{H}}_{\rm{2}}}{\rm{\;}}\left( {{\rm{slow}}} \right)\)
\({\rm{2Al + \;6C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH\;}} \to \mathop {{\rm{2Al(C}}{{\rm{H}}_{\rm{3}}}{\rm{COO}}{{\rm{)}}_{\rm{3}}}}\limits_{{\rm{Aluminium\;acetate}}} {\rm{ + \;3}}{{\rm{H}}_{\rm{2}}}{\rm{\;}}\left( {{\rm{slow}}} \right)\)
\({\rm{2Al}}\left( {\rm{s}} \right){\rm{\; + 3}}{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}\left( {{\rm{aq}}} \right) \to {\rm{A}}{{\rm{l}}_{\rm{2}}}{\left( {{\rm{S}}{{\rm{O}}_{\rm{4}}}} \right)_{\rm{3}}}\left( {{\rm{aq}}} \right){\rm{ + 3}}{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right)\)

Reactivity of Aluminium Towards Alkalis

Aluminium reacts with aqueous alkali and liberates dihydrogen.
\({\rm{2Al}}\left( {\rm{s}} \right){\rm{ + 2NaOH}}\left( {{\rm{aq}}} \right){\rm{ + 6}}{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( {\rm{l}} \right) \to \mathop {{\rm{2N}}{{\rm{a}}^{\rm{ + }}}{{\left[ {{\rm{Al}}\left( {{\rm{O}}{{\rm{H}}_{\rm{4}}}} \right)} \right]}^{\rm{ – }}}\left( {{\rm{aq}}} \right){\rm{\;\;}}}\limits_{{\rm{Sodium\;Tetra\;Hydroxy\;aluminate\;}}\left( {{\rm{III}}} \right)} {\rm{ + 3}}{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right)\)

Reaction of Aluminium with Chlorine

Aluminium reacts with chlorine on heating to form Aluminium chloride.

\(\mathop {{\rm{2Al}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium}}} {\rm{ + }}\mathop {{\rm{3C}}{{\rm{l}}_{\rm{2}}}\left( {\rm{g}} \right)}\limits_{{\rm{Chlorine}}} \to \mathop {{\rm{2AlC}}{{\rm{l}}_{\rm{3}}}\left( {\rm{s}} \right)}\limits_{{\rm{Aluminium\;chloride}}} {\rm{\;}}\)

Reducing action of Aluminium

Aluminium has a high affinity for oxygen. For this reason, it replaces many substances from their oxides. Thus, Aluminium is a powerful reducing agent. It reduces \({\rm{CO}}\) and \({\rm{C}}{{\rm{O}}_2}\) to carbon.
\({\rm{3CO + 2Al}} \to {\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{ + 3C}}\)
\({\rm{3C}}{{\rm{O}}_{\rm{2}}}{\rm{ + 4Al}} \to {\rm{2A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{ + 3C}}\)

Reduction with Aluminium (thermite process or alumino-thermic process)

Metal oxide reduction to form the metal using Aluminium powder as a reducing agent is known as a thermite reaction. This reaction is used to reduce metal oxide to form metal. For example,
(i) Manganese dioxide is reduced to manganese by heating with Aluminium.
\({\rm{3Mn}}{{\rm{O}}_{\rm{2}}}{\rm{ + 4Al}} \to {\rm{3Mn + 2A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\)
(ii) Ferric oxide \(\left( {{\rm{F}}{{\rm{e}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}} \right)\) is reduced by Aluminium to iron.
\({\rm{F}}{{\rm{e}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{ + 2Al}} \to {\rm{2Fe + A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\)
(iii) Chromium oxide is reduced by Aluminium to chromium metal.
\({\rm{C}}{{\rm{r}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}{\rm{ + 2Al}} \to {\rm{2Cr + A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}\)

Uses of Aluminium

1. Aluminium is a good conductor of heat, and it does not get corroded. Hence, it is used to make domestic utensils like pans, kettles, etc.
2. Aluminium is a good conductor of electricity. Hence, it extensively used in making electrical wires.
3. Aluminium foils \(0.05\,{\text{mm}}\) thick) are used for wrapping foodstuff and drugs.
4. Aluminium is a light metal. Hence, it is used to make bodies and parts of aircraft, buses, cars, furniture, etc. Since pure Aluminium is not very strong, alloys of Aluminium are used for these purposes.
5. Aluminium powder is used in making anti-corrosion paints and in explosives.
6. Aluminium powder is also used in the alumino-thermic process for welding two iron objects.

Electronic Configuration of Aluminium

The atomic number of Aluminium is \(13\). It means that an atom of Aluminium contains \(13\) electrons, distributed among the shells as shown below.

\({\rm{K}}\)	\({\rm{L}}\)	\({\rm{M}}\)
\(2\)	\(8\)	\(3\)

Thus, the outermost shell or valence shell of an Aluminium atom has (3) electrons.

Who Discovered Aluminium?

Aluminium was considered rarer and more precious than gold or silver through most of the 19th century. However, a pure form of the Aluminium metal was first successfully extracted from its ore in 1825 by Danish Chemist Hans Christian. Techniques to produce Aluminium in more but subtle cost-effective ways emerged in 1889.

This lightweight recyclable metal has since become the foundation of our country’s infrastructure. Aluminium is now used in construction, packaging, automotive, energy, transportation, aerospace, and Défense applications industries.

Density

Aluminium is a light metal of density \({\rm{2}}{\rm{.7}} \times {\rm{1}}{{\rm{0}}^3}\,{\rm{kg}}{{\rm{m}}^{ – 3}}\,{\rm{or}}\,2.70\,{\rm{gc}}{{\rm{m}}^{ – 3}}.\) The density of Aluminium is unique in various ways and makes this material a popular choice for many applications.

Occurrence

Aluminium comes third amongst the most abundant elements in nature. However, Aluminium is the most abundant metal in the Earth’s crust. It is a reactive metal. Hence, it does not occur native or in nature. In the combined state, it is widely distributed in nature in the form of compounds. Some of its essential minerals are:

1. Cryolite, \({\rm{N}}{{\rm{a}}_3}{\rm{Al}}{{\rm{F}}_6}\)
2. Corundum, \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\)
3. Bauxite, \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3} \cdot 2{{\rm{H}}_2}{\rm{O}}\)
4. Feldspar or Felspar, \({\rm{KAlS}}{{\rm{i}}_3}{{\rm{O}}_8}\)

However, bauxite is the only mineral from which Aluminium is obtained profitably. Around \(60\% \) of bauxite consists of Aluminium oxide \(\left( {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}} \right){\rm{.}}\)

In India, Bharat Aluminium Corporation, Hindustan Aluminium Corporation, and the Indian Aluminium Company produce Aluminium from bauxite. Orissa, Jharkhand, Chhattisgarh, Andhra Pradesh, and Gujarat are among the states where these bauxite deposits for Aluminium extraction are located.

Extraction of Aluminium from Bauxite

The extraction of Aluminium from bauxite consists of the following steps.

Preparation of Alumina: Bayer process

Crude bauxite is finely powdered and treated with a concentrated solution of caustic soda at \(432\,{\rm{K}}.\) At about \(523\,{\rm{K}}.\) Under \(40\,{\rm{atm}}\) pressure, Aluminium oxide in the ore goes into the solution, forming sodium aluminate, while the impurities are left behind undissolved.
\(\mathop {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}} \cdot 2{{\rm{H}}_2}{\rm{O}}}\limits_{{\rm{bauxite}}} {\rm{ + }}\;\mathop {{\rm{2NaOH}}}\limits_{{\rm{sodium}}\:{\rm{hydroxide}}} \to \mathop {{\rm{2NaAlO}}{{\rm{H}}_{\rm{2}}}}\limits_{{\rm{sodium}}\:{\rm{aluminate}}} {\rm{ + }}\;\mathop {{\rm{3}}{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} \)
The solution is filtered. The filtrate is diluted with water, and a little freshly precipitated Aluminium hydroxide is added for precipitation. Sodium aluminate gets hydrolysed to produce a white precipitate of Aluminium hydroxide.
\(\mathop {{\rm{NaAl}}{{\rm{O}}_{\rm{2}}}}\limits_{{\rm{sodium\;aluminate}}} {\rm{ + \;}}\mathop {{\rm{2}}{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} {\rm{\;}} \to {\rm{\;}}\mathop {{\rm{Al(OH}}{{\rm{)}}_{\rm{2}}}}\limits_{{\rm{Aluminium\;hydroxide}}} {\rm{\; + \;}}\mathop {{\rm{NaOH}}}\limits_{{\rm{sodium\;hydroxide}}}\)
The precipitate of \({\rm{Al}}{\left( {{\rm{OH}}} \right)_{\rm{3}}}\) is filtered off, washed, dried, and ignited to get pure Aluminium oxide (alumina).
\(\mathop {{\rm{2Al}}\left( {{\rm{O}}{{\rm{H}}_{\rm{3}}}} \right)}\limits_{{\rm{Aluminium\;hydroxide}}} {\rm{\;}} \to \mathop {{\rm{A}}{{\rm{l}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}}\limits_{{\rm{Aluminium\;oxide}}} {\rm{ + }}\mathop {{\rm{3}}{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{Water}}} {\rm{\;}}\)

Hall-Heroult process of Electrolytic Reduction

The process used in industries for Aluminium smelting or dissolving Aluminium oxide (alumina) is called Hall–Héroult process.

Alumina melts at \({\rm{2303 K}}{\rm{.}}\) It is a bad conductor of electricity. However, when mixed with cryolite \(\left( {{\rm{N}}{{\rm{a}}_{\rm{3}}}{\rm{Al}}{{\rm{F}}_{\rm{6}}}} \right)\) and some calcium fluoride, the mixture becomes a good conductor of electricity and melts at \(1173 – 1223\,{\rm{K}}.\) The cryolite thus considerably reduces the energy cost. The iron cell is lined inside with gas carbon, which serves as a cathode. Carbon rods act as an anode. The electrolyte, thus, contains \({{\rm{N}}^{\rm{ + }}}{\rm{,\;A}}{{\rm{l}}^{{\rm{3 + }}}}{\rm{,\;}}{{\rm{F}}^{\rm{ – }}}{\rm{,}}\) and \({{\rm{O}}^{{\rm{2 – }}}}\) ions.

On passing electric current, \({\rm{A}}{{\rm{l}}^{{\rm{3 + }}}}\) ions are discharged at the cathode and the \({{\rm{O}}^{{\rm{2 – }}}}\) ions at the anode.
\({\rm{A}}{{\rm{l}}^{{\rm{3 + }}}}{\rm{ + 3e}} \to {\rm{Al\;}}\left( {{\rm{at\;the\;cathode}}} \right)\)
\({\rm{2}}{{\rm{O}}^{{\rm{2 – }}}} \to {{\rm{O}}_{\rm{2}}}{\rm{ + 4e\;}}\left( {{\rm{at\;the\;anode}}} \right)\)
Some oxygen forms formed in the reaction escapes, and some react with the anode to form \({\rm{C}}{{\rm{O}}_2}.\) Thus, carbon anode burns away due to its reaction with oxygen.
\({\rm{C + }}{{\rm{O}}_{\rm{2}}} \to {\rm{C}}{{\rm{O}}_{\rm{2}}}{\rm{\;}}\)
Hence, the anode has to be replaced from time to time. Naturally, this increases the cost of production of Aluminium. Being heavier than the electrolyte, Molten Aluminum sinks to the bottom and is taken out through the tapping hole.

Electrolytic Refining of Aluminium

Aluminium thus obtained is \(99\%\) pure. It contains iron and silicon as impurities. It is purified by further electrolysis using Hope’s method. The electrolysis is carried out in an iron box lined with carbon. Three layers differing in densities are placed in the box.
Bottom layer: It consists of impure Aluminium. It acts as an anode.
Middle layer: It consists of a mixture of the fluorides of \({\rm{Al,}}\,{\rm{Na,}}\) and \({\rm{Ba}}{\rm{.}}\) It serves as an electrolyte.
Upper layer: It consists of pure molten Aluminium and serves as the cathode.

On passing electric current, Aluminium ions from the middle layer are discharged at the cathode. As a result, an equivalent amount of Aluminium goes into the middle layer from the bottom layer.

The impurities are left behind. Oxygen is liberated at the anode. Oxygen reacts with the carbon anode. Hence, the anode is gradually consumed.

Corrosion of Aluminium

You would have observed that Aluminium vessels lose their shine and become dull soon after use. Do you know the reason? It is due to the corrosion of Aluminium metal when exposed to moist air. Let us illustrate the corrosion of Aluminium articles. We know that Aluminium metal is more reactive than iron.

So, the Aluminium metal starts to corrode quickly when it comes in contact with moist air. Therefore, a thin layer of Aluminium oxide is formed all over the metal when the metal is exposed to humid air. This layer prevents the metal underneath from getting corroded. In other words, this thin layer of Aluminium oxide protects the surface of Aluminium articles from further corrosion.

Prevention from Corrosion

The layer of Aluminium oxide on the surface of Aluminium articles is made thicker by electrolysis to give the articles more protection from corrosion. This process is called anodising. In this process, the Aluminium article is made as an anode in an electrolytic tank consisting of dilute sulphuric acid. During electrolysis, oxygen gas is liberated at the anode, which reacts with the Aluminium to form a thicker layer of Aluminium oxide on its surface to protect the Aluminium object from corrosion.

Summary

This article concludes that Aluminium is the most abundant metal on Earth’s crust but is rarely found uncombined in nature. We have learned how Aluminium is extracted in different ways and the uses of Aluminium in our day-to-day life.

Related Topic to Study

1. Hydrogen 2. Nitrogen 3. Sulphur 4. Coal

FAQs About Aluminium

Let’s look at some of the commonly asked questions about Aluminium:

Q.1. Is Aluminium stronger than steel?
Ans: Pure Aluminium does not have a high yield, strength, or tensile strength. However, the addition of alloying elements like manganese, silicon, copper, and magnesium can increase the strength properties of Aluminium and produce an alloy with properties tailored to particular applications.

Q.2. Why is Aluminium expensive?
Ans: Aluminium is the third most abundant element in the Earth’s crust, but it is expensive, primarily because of the amount of electricity required in the extraction process. Aluminium oxide has a very high melting point, so it is more costly.

Q.3. Is Aluminium a metal?
Ans: Aluminium comes from bauxite. Pure Aluminium is soft, ductile, corrosion-resistant. It has a high electrical conductivity, widely used for foil and conductor cables, but alloying with other elements is necessary to provide the higher strengths needed for different applications.

Q.4. What are some uses of Aluminium?
Ans: The five uses of Aluminium are:
1. Aluminium is an excellent conductor of heat and is used in making cooking utensils, water boilers, etc.
2. Aluminium foils \(0.05\,{\text{mm}}\) thick) used for wrapping foodstuff and drugs
3. Aluminium is a light metal. Hence, it is used in making bodies and parts of aircraft, buses, cars, furniture, etc. Since pure Aluminium is not very strong, alloys of Aluminium are used for these purposes.
4. Aluminium powder is used in making anti-corrosion paints and in explosives.
5. Aluminium is both strong and lightweight, and it is ideal for architectural applications. 

Q.5. Why is Aluminium used to make utensils for cooking while it’s a highly reactive metal?
Ans: Though Aluminium is a highly reactive metal, it is resistant to corrosion. It reacts with oxygen present in the air to form a thin passive layer of Aluminium oxide. This oxide layer prevents further reaction of Aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make cooking utensils.

Q.6. Who Discovered Aluminium?
Ans: Aluminium was considered rarer and more precious than gold or silver through most of the 19th century. However, a pure form of the Aluminium metal was first successfully extracted from its ore in 1825 by Danish Chemist Hans Christian. Techniques to produce Aluminium in more but subtle cost-effective ways emerged in 1889.

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