Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Metals and Nonmetals ↓


Extraction of metals


Metals have various applications in our daily lives due to their exceptional properties such as conductivity, ductility, and strength. Before we can use metals in various industries and practical applications, they must be extracted from their natural state. In this guide, we will explore the fascinating world of metal extraction in simple terms. We will go deep into both the chemistry and processes involved in extracting metals from ores.

Understanding ores and minerals

Metals are usually found in the Earth's crust combined with other elements. These combinations are called minerals. When a mineral contains a sufficient quantity of a particular metal and can be extracted economically, it is called an ore.

For example, the mineral hematite (Fe 2 O 3) is an ore of iron, bauxite (Al 2 O 3 ·2H 2 O) is an ore of aluminum, and chalcopyrite (CuFeS 2) is an ore of copper.

Stages of metal extraction

Extraction of metals involves several main stages. Let's understand them in detail:

1. Concentration of ore

The first step is the concentration of the ore, also known as ore dressing. This is important because raw ore extracted from the earth often contains clay and other impurities.

Common methods for concentrating ores include:

  • Gravity separation: This uses the difference in density between the ore particles and the impurities. A substance such as water is used, causing the denser ore to sink and the impurities to float.
  • Magnetic separation: This is used when the ore or impurities are magnetic. When the crushed ore is passed over a magnetic roller, the magnetic ore particles are attracted and the non-magnetic particles are retained.
  • Froth flotation: This is used mainly for sulphide ores. The process involves mixing crushed ore with water and adding a froth-producing substance. The ore sticks to the froth and rises to the surface, causing the impurities to separate.
  • Leaching: In this method a suitable solvent, often a chemical, is used to dissolve the desired metal, while the impurities remain undissolved.

2. Extraction from concentrated ore

After concentrating the ore, the next step is the extraction of the metal. Different methods are used depending on the chemical properties of the metal.

Reduction of ores

Most metal ores are oxides or are found in combination with oxygen. To extract the metal we have to remove the oxygen. This method varies according to the reactivity of the metal.

For highly reactive metals: Metals such as sodium, potassium, calcium and aluminium are extracted through electrolysis.

For example, in the electrolysis of molten NaCl (sodium chloride), sodium is produced at the cathode (negative electrode), while chlorine gas is evolved at the anode (positive electrode).

2NaCl(l) → 2Na(l) + Cl 2 (g)

For moderately reactive metals: These metals like iron, zinc, lead, etc. are often extracted by carbon reduction (using carbon in the form of coke) or reduction by another chemical agent like carbon monoxide.

An example of this is the extraction of iron from hematite in a blast furnace, where coke acts as a reducing agent:

Fe 2 O 3 + 3C → 2Fe + 3CO

For less reactive metals: Metals like gold, silver and platinum are either found in the free state or require minimal reduction. Methods like physical separation or mild chemical reactions are sufficient for their extraction.

3. Purification of the extracted metals

Metals often contain impurities even after extraction. The process of removing these impurities and refining the metals is important to ensure that they meet the desired standards and quality.

The following are the techniques used for purification:

  • Distillation: Ideal for metals with low boiling points, such as zinc and mercury, where the metal is vaporized and then condensed into a pure form.
  • Electrolytic refining: Used for high-value metals such as copper and silver. An impure anode and a pure cathode are immersed in an electrolyte solution, causing the metal ions to be deposited in pure form at the cathode.
  • Field refining: This method, often used for semiconductors, involves passing an induction coil along a metal body, causing the metal to melt and purify it locally, with impurities being driven to one end.

Metallurgical processes: Phases and examples

Let us look at some major metallurgical processes and practical examples:

Example 1: Extraction of aluminium from bauxite

Ore: bauxite (aluminum oxide hydroxide), mainly Al 2 O 3 ·2H 2 O

Stage 1: Concentration: The ore is initially purified using the Bayer process, where bauxite is dissolved in sodium hydroxide, separating the aluminium from impurities.

Step 2: Reduction: Pure alumina is reduced through electrolysis using the Hall–Heroult process, where aluminum oxide is dissolved in molten cryolite.

2Al 2 O 3 + 3C → 4Al + 3CO 2

Example 2: Extraction of iron from hematite

Ore: Hematite Fe 2 O 3

Stage 1: Concentration: The ore is crushed and concentrated using gravity separation.

Step 2: Reduction: The concentrated ore is reduced in a blast furnace to extract iron.

Fe 2 O 3 + 3C → 2Fe + 3CO

Environmental considerations

Extraction of metals is not only a matter of chemistry and physics, but also of environmental responsibility. Extractive industries have a significant impact on the environment due to deforestation, soil erosion and pollution. Therefore, it is important to ensure that these processes are conducted with minimal damage to the ecosystem.

New methods, particularly relating to green chemistry and sustainable mining, are being developed to ensure that the industry moves towards a more environmentally friendly approach. This includes advances in the recycling of metals and the reduction of toxic by-products and gases released during extraction processes.

Conclusion

The extraction of metals is a complex but essential process that involves various steps including concentration, reduction, and purification. With advances in technology, new eco-friendly and efficient methods of extraction are being developed. Understanding these basic principles behind metal extraction can provide practical knowledge about how everyday materials are produced and refined.

In short, metallurgy, the science of the extraction and processing of metals, plays a vital role in the development of materials that contribute to technological advancements and everyday conveniences.


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Extraction of metals

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