Grade 8
  1. Introduction to Chemistry  1.1. Nature and scope of chemistry  1.2. Importance of chemistry in daily life  1.3. Chemistry and its relation with other sciences  1.4. The role of chemistry in industry, medicine and the environment  1.5. Scientific investigation and experimental methods in chemistry
  2. Matter and its properties  2.1. Definition and classification of matter  2.2. Physical and chemical properties of matter  2.3. Law of conservation of matter  2.4. Extensive and Intensive Properties of Matter  2.5. Kinetic molecular theory of matter  2.6. States of matter: solids, liquids, gases, plasmas, and Bose-Einstein condensates  2.7. Changes in state and energy are involved  2.8. Diffusion and Brownian motion
  3. Elements, Compounds, and Mixtures  3.1. Definition and differences between elements, compounds, and mixtures  3.2. Atomic Structure and Atomic Number  3.3. Chemical symbols and formulas  3.4. Trends in the Periodic Table (Groups and Periods)  3.5. Classification of Elements: Metals, Nonmetals and Metalloids  3.6. Rare Earth Elements and Transition Metals  3.7. Types of mixtures: homogeneous and heterogeneous  3.8. Separation of Mixtures Using Physical and Chemical Methods
  4. Separation Techniques  4.1. Filtration, Sedimentation and Decantation  4.2. Evaporation and crystallization  4.3. Distillation and Fractional Distillation  4.4. Chromatography and its applications  4.5. Sublimation in the purification of compounds  4.6. The role of centrifugation in biochemical processes
  5. Atomic Structure  5.1. Dalton's atomic theory  5.2. Structure of the atom: protons, neutrons and electrons  5.3. Bohr's atomic model  5.4. Introduction to Quantum Mechanical Model  5.5. Electron Configuration and Energy Levels  5.6. Excitation and emission spectra  5.7. Isotopes and their applications
  6. Periodic Table and Chemical Trends  6.1. History and Development of the Periodic Table  6.2. Modern periodic law  6.3. Periodicity and trends in atomic and ionic sizes  6.4. Ionization Energy, Electron Affinity and Electronegativity  6.5. Introduction to Lanthanides and Actinides  6.6. Application of periodic trends in chemistry
  7. Chemical Bonding and Molecular Structure  7.1. Types of chemical bonds: ionic, covalent and metallic bonds  7.3. Polar and Nonpolar Molecules  7.4. Hydrogen bonding and its applications  7.5. Intermolecular forces: dipole-dipole, London dispersion force
  8. Chemical Reactions and Stoichiometry  8.1. Chemical Equations and Balance  8.2. Types of Chemical Reactions: Combination, Decomposition, Displacement and Redox  8.3. Introduction to stoichiometry and the mole concept  8.4. Limiting reactant in chemical equations  8.5. Reaction rate, catalyst, and factors affecting reaction rate
  9. Acids, Bases and Salts  9.1. Definition and Properties of Acids and Bases  9.2. Strong vs. Weak Acids and Bases  9.3. pH Scale and pH Calculation  9.4. Neutralization reactions  9.5. Buffer solutions and their importance  9.6. Applications of Acids, Bases and Salts in Daily Life
  10. Solutions and Solubility  10.1. Definition of Solution, Solute, and Solvent  10.2. Factors Affecting Solubility  10.3. Concentration units: molarity and molality  10.4. Saturated, unsaturated and supersaturated solutions  10.5. Concept of osmosis and reverse osmosis  10.6. Concentrative properties of solutions
  11. Gases and Gas Laws  11.1. Properties of gases  11.2. Introduction to Ideal and Real Gases  11.3. Boyle's Law, Charles' Law and Avogadro's Law  11.4. Ideal Gas Equation and Its Applications  11.5. Application of Gas Laws in Real Life
  12. Thermochemistry and energy transformation  12.1. Energy in Chemical Reactions  12.2. Exothermic vs. Endothermic Reactions  12.3. Heat and Enthalpy Changes  12.4. Calorimetry and heat transfer in reactions
  13. Metals and Nonmetals  13.1. Physical and Chemical Properties of Metals and Nonmetals  13.2. Reactivity Series of Metals  13.3. Corrosion and its prevention  13.4. Extraction of metals from ores  13.5. Uses of metals and non-metals in daily life
  14. Introduction to Organic Chemistry  14.1. Characteristics of carbon and organic compounds  14.2. Functional groups and their importance  14.3. Simple Hydrocarbons: Alkenes, Alkenes and Alkynes  14.4. Isomerism in organic compounds  14.5. Introduction to polymers and their uses
  15. Environmental Chemistry and Sustainability  15.1. Green Chemistry Principles  15.2. Effects of Chemical Pollution on Ecosystems  15.3. Acid rain and its effects  15.4. Ozone layer depletion and global warming  15.5. Waste Management and Recycling in Chemistry

Grade 8 → Metals and Nonmetals ↓


Extraction of metals from ores


Metals are incredibly important to our daily lives; they form the basis of our transportation, construction, manufacturing, and many other industries. However, these metals are not just found in usable form; most of them are extracted from minerals found in the Earth's crust. In this comprehensive guide, we will explore the processes of extracting metals from ores, focusing on the processes that go into them, and the principles behind these methods.

What are ores?

An ore is a naturally occurring substance or rock that contains a metallic compound from which the metal can be extracted economically and profitably. Ores often contain unwanted substances, collectively called gangue. In order to use the metal, the ores must be processed to separate the metal into a form we can use.

Example 1: Bauxite is an ore from which aluminum is extracted. It consists mainly of aluminum oxide (Al 2 O 3). Other elements in bauxite include iron oxide and clay minerals.

Stages of metal extraction from ores

The extraction of metals from ores involves several major stages:

  1. Mined from the earth.
  2. It is crushed and ground to free the metallic mineral from the surrounding gangue.
  3. Concentration process to remove unwanted materials.
  4. Reduction process to extract pure metal.

Mental mining techniques

Mining is done using a variety of methods, but depending on the depth of the ore, it can generally be classified into two types:

1. Surface mining

Surface mining, also known as open-pit mining, involves removing surface vegetation, soil, and possibly bedrock layers to access buried ore deposits. This method is cost-efficient for shallow deposits.

Example 2: Iron ore is often mined through surface mining techniques due to its large quantity and relatively shallow depth.

2. Underground mining

Underground mining is used for deeper ore deposits, which requires more manpower and also costs more because of the necessary infrastructure, ventilation and safety measures.

Example 3: Precious metals such as gold and platinum are often extracted through underground mining.

Crushing and grinding

Once the ore is mined, it must undergo further processing in the form of crushing and grinding to break the rock containing the ore into smaller, more manageable pieces. This increases the surface area of the ore, making it easier to extract the metal inside it.

Concentration of ore

Concentration of ore involves washing away unwanted substances (gange) from the metal ore. It often involves a combination of different physical processes:

Physical processes

  • Gravity separation: uses the density difference between the ore and waste.
  • Magnetic separation: Uses the magnetic properties of the metal, if applicable.
  • Froth flotation: Uses differences in surface properties to separate valuable minerals from waste materials.
Example 4: Froth flotation in copper mining. Finely ground ore is mixed with water to form a slurry, air is blown into the mixture, and the copper minerals cling to the bubbles and float to the surface.

Reduction: Extraction of pure metal

Reduction is the final step, where the metal compound is reduced to the actual metal. Three primary techniques are used:

Chemical reduction

It involves using reducing agents such as carbon (in the form of coke), hydrogen or aluminium to reduce the metal compound to its metallic form. A classic example of this method is blast furnace operation.

        Fe 2 O 3 + 3C → 2Fe + 3CO

Here, iron(III) oxide is reduced to iron using carbon as the reducing agent.

Electrolytic reduction

In this process, electricity is used to bring about reduction. Metals such as aluminium and sodium are extracted using this technique, which are divided into two categories:

  • Electrolysis of molten compounds: Used in the extraction of very reactive metals.
  • Electrolysis of aqueous solutions: for metals that can be deposited from water-based solutions.
        2Al 2 O 3 + 3C → 4Al + 3CO 2

Aluminium is produced from bauxite ore and chrysolite by electrolytic reduction.

Roasting and baking

These thermal processes are used depending upon the chemical nature of the metal ore:

Roast

This involves heating the ore in the presence of oxygen, where applicable, to remove volatile impurities. Sulfide ores such as zinc and lead often undergo a process called roasting.

        2ZnS + 3O 2 → 2ZnO + 2SO 2

Cook

Calcination involves heating the ore in the absence or limited supply of oxygen, which helps remove moisture and volatile substances. In this process carbonates are often converted to oxides.

        CaCO 3 → CaO + CO 2

Metallurgical methods used for different metals

Specific methods have been adopted for the extraction of each metal depending on its source, physical and chemical properties and cost-effectiveness.

  • Iron: Blast furnace method for extraction from iron ore.
  • Aluminium: Electrolysis of Bauxite Ore.
  • Copper: Froth flotation followed by roasting and then electrolysis.

Visualization of metal extraction

To understand these processes, imagine a company working on a mountain of ore. Initially, machines and workers remove the topsoil and vegetation, revealing the heavy deposits beneath the surface. Large trucks transport these rocks to a processing facility, where the rocks are crushed into smaller pieces. Next, the crushed ore is washed, filtered, and finally subjected to heat to obtain the pure metal.

Mining Ore Processing

As we have explained, extracting metals from ores is a multi-step process that involves a combination of mechanical, chemical, and sometimes electrical means to obtain pure metals. Though often complex, understanding the extraction process is important in understanding how raw materials are transformed into the metals that are fundamental to modern civilization.


Grade 8 → 13.4


U
username
0%
completed in Grade 8

← Prev (13.3)
Corrosion and its prevention
Next (13.5) →
Uses of metals and non-metals in daily life

Comments 



Extraction of metals from ores

https://www.chemistryelite.com/g8/13.4?ceal=en