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 → Carbon and its compounds ↓


Polymers (Introduction to Natural and Synthetic Polymers)


In chemistry, the study of carbon and its compounds uncovers an important and fascinating world of polymers. Polymers are large, long-chain molecules made up of repeating structural units called monomers. These monomers are bonded together, forming extensive networks, which give polymers their unique properties. Let's explore both natural and synthetic polymers, their structure, uses, and importance in our daily lives.

What are polymers?

Polymers can be thought of as a string of beads, where each bead represents a monomer – a small molecule. These monomers join together to form a long chain or network, and these links are called covalent bonds. The process of forming polymers by joining monomers is called polymerization.

Example of a simple polymer chain:

monomer + monomer + monomer → polymer
      hhhh
      ,
  H - C - C - C - C - H
      ,
      hhhh

Types of polymers

Polymers can be classified based on their origin, structure, and method of polymerization. There are two main types:

Natural polymers

These are found in nature and are essential for life. Some examples include:

  • DNA: The blueprint of life, DNA is a natural polymer composed of nucleotides.
  • Proteins: Made up of amino acids, these proteins are the building blocks of our body.
  • Cellulose: Cellulose, found in the cell walls of plants, provides structural strength to plants.

Synthetic polymers

These are man-made and have been developed for a variety of applications. Some examples include:

  • Polythene (polyethylene): Used in plastic bags and bottles.
  • Nylon: Used in textiles and apparel.
  • Teflon: Known for its non-stick properties, it is used in cooking utensils.

Natural versus Synthetic Polymers:

Natural Polymers Synthetic polymers DNA Protein Polyethylene Nylon

Polymerization

The process by which monomers are chemically combined to form polymers is called polymerization. There are two main types of polymerization:

Addition polymerization

In this process, monomers are joined together without losing any small molecule. This type of polymerization usually involves monomers containing double bonds (unsaturated compounds).

Example: Manufacture of polythene

CH₂=CH₂ + CH₂=CH₂ + CH₂=CH₂ → -CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-
          (ethylene monomers) (polyethylene)

Condensation polymerization

This process involves the joining of monomers, but there is a loss of smaller molecules such as water or alcohol. This process is common in the formation of natural polymers.

Example: Manufacture of nylon

Amine + Carboxylic acid → Polyamide + Water
   H₂N-R-NH₂ + HOOC-R'-COOH → -HN-R-NH-CO-R'-CO- + H₂O

Physical properties of polymers

Polymers exhibit a wide range of physical properties that make them suitable for a variety of applications:

  • Strength: Many polymers are very strong. For example, nylon is used to make ropes and parachutes.
  • Elasticity: Polymers such as rubber can be stretched and return to their original shape.
  • Plasticity: Some polymers can be molded into different shapes, which is useful for making objects such as containers and toys.
  • Thermal insulation: Polymers such as polyvinyl chloride (PVC) are used for insulation purposes due to their heat resistance.

Applications of polymers

Polymers are an integral part of many industries due to their diverse properties. Some applications include:

  • Packaging: Polymers such as polyethylene and polypropylene are widely used in packaging because they are lightweight and durable.
  • Textiles: Fibres such as polyester and acrylic are used to make clothes, carpets and curtains.
  • Automobile parts: Components such as bumpers, dashboards, and fuel tanks are often made from polymers because of their strength and lightness.
  • Healthcare: Polymers are used to make various medical devices such as syringes, tubing, and even prosthetics.

Illustration of Polymer Applications:

Packaging Clothing Automobile Health care

Environmental impact of polymers

Polymers have many benefits, but they also bring environmental challenges, especially synthetic polymers. Non-biodegradable polymers can persist in the environment, causing pollution and harm to wildlife. Efforts are being made to develop biodegradable polymers and improve recycling techniques.

  • Biodegradable polymers: These polymers are designed to decompose easily in the environment. An example of this is polylactic acid (PLA) which is used in some packaging materials.
  • Recycling: The initiative focuses on recycling used polymers to reduce plastic waste and environmental impact.

Conclusion

Polymers, both natural and synthetic, are an essential part of modern life, providing materials for a wide variety of uses. The study of polymers provides insight into designing and developing materials that meet specific needs while addressing environmental concerns. Understanding their structure and properties allows us to make informed decisions that have far-reaching effects on society and the environment.


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Polymers (Introduction to Natural and Synthetic Polymers)

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