Class 12 Chemistry in Service to Mankind Notes

Polymer

Definition: A polymer is a high molecular weight complex compound composed of a large number of simple repeating units.

Monomer

Definition: A monomer is a low molecular weight simple compound that forms the repeating units in a polymer.

Polymerization

Definition: Polymerization is the process of converting monomers into a polymer.

Examples of Polymers

  • Polythene
  • PVC
  • Nylon
  • Protein

Classification of Polymers

A) On the Basis of Types of Component Monomers: Homopolymers & Copolymers

  1. Homopolymer:
  • Definition: A polymer made from only one kind of monomer.
  • Process: The process of making such polymers is called homopolymerization.
  • Examples: Polythene (from ethylene), Teflon (from tetrafluoroethylene).
  1. Copolymer:
  • Definition: A polymer made from more than one kind of monomer.
  • Process: The process of making such polymers is called copolymerization.
  • Examples: Nylon 6,6 (from hexamethylene diamine and adipic acid), Bakelite (from phenol and formaldehyde).

B) On the Basis of Nature of Chemical Reaction: Addition & Condensation Polymers

  1. Addition Polymer:
  • Definition: A polymer made by the addition of monomers without the elimination of any molecule.
  • Process: The process of making such polymers is called addition polymerization.
  • Examples: Polythene, PVC, Teflon.
  1. Condensation Polymer:
  • Definition: A polymer made by the addition of monomers with the elimination of smaller molecules.
  • Process: The process of making such polymers is called condensation polymerization.
  • Examples: Nylon 6,6, Bakelite.

C) On the Basis of Source: Natural & Synthetic Polymers

  1. Natural Polymer:
  • Definition: Naturally occurring polymers.
  • Examples:
    • Polysaccharides like Starch and Cellulose (Monomers: Glucose)
    • Proteins like Wool, Natural Silk, Leather (Monomers: α-amino acids)
    • Nucleic acids like RNA and DNA (Monomers: Nucleotides)
    • Natural rubber (Monomers: Isoprene)
  1. Synthetic Polymer:
  • Definition: Polymers synthesized or prepared in a laboratory or factory.
  • Examples: Polythene, Bakelite.

One Step Manufacture and Structure of Some Synthetic Polymers

  1. Polythene (Polyethylene):
  • Manufacture:
    <code>n (CH2 = CH2) --300°C/High Pressure--> [CH2–CH2]n (Ethene) (Polythene)</code></code>
  • Monomer: Ethene (Ethylene)
  • Uses: Making pipes, buckets, wires, etc.
  1. PVC (Polyvinyl Chloride):
  • Manufacture:
    n[CH2=CHCl] --Organic Peroxide, ∆--> [CH2–CHCl]n (Vinyl Chloride) (PVC)
  • Monomer: Vinyl chloride
  • Uses: Making pipes, PVC tape, electric insulators, etc.
  1. Teflon:
  • Manufacture:
    <code>n [ F F C = C --Organic Peroxide, ∆--> [ F F F F] C C]n (Tetrafluoroethylene) (Teflon)</code></code>
  • Monomer: Tetrafluoroethylene
  • Uses: Making non-stick coatings on cooking utensils.

Nylon 6,6:

  • Manufacture:
    [ n\text{[NH}_2\text{–(CH}_2\text{)}_6\text{ – NH}_2\text{]} + n\text{[HOOC–(CH}_2\text{)}_4\text{ – COOH]} \xrightarrow{\Delta,\text{High pressure}} [\text{N – (CH}_2\text{)}_6\text{ – N – C – (CH}_2\text{)}_4\text{ – C}]_n ]
    (Hexamethylene diamine) + (Adipic acid) → (Nylon 6,6)
  • Monomer: Hexamethylene diamine and adipic acid
  • Uses: For making clothes, ropes, buckets, etc.

Bakelite:

  • Manufacture:
    [\text{Phenol} + \text{Formaldehyde} \xrightarrow{\Delta, \text{dil. NaOH}} \text{Bakelite}]
  • Monomers: Phenol and formaldehyde
  • Uses: For making combs, fountain pens, electric goods, etc.

Plastics

Plastics:

  • Definition: Plastics are carbon-containing synthetic polymers that can be molded when soft and set into durable articles when hardened.
  • Examples: Polythene, PVC, Nylon, Bakelite, etc.

Types of Plastics:

  1. Thermoplastics:
  • Definition: Thermoplastics can be melted repeatedly without any change in their chemical composition and mechanical properties.
  • Examples: Polythene, PVC, Polystyrene, etc.
  1. Thermosetting Plastics:
  • Definition: Thermosetting plastics can be melted once but cannot be melted again after they set into a permanent solid mass due to first heating and cooling.
  • Examples: Phenol-formaldehyde (Bakelite), Melamine-formaldehyde, Urea-formaldehyde, etc.

Dyes

Dyes:

  • Definition: Dyes are colorful organic compounds that show fastness while coloring and are resistant to light, heat, soap, and bleaching.

Types of Dyes:

  1. Natural Dyes:
  • Definition: Colorful organic compounds extracted from plants.
  • Examples: Alizarin (Red dye), Indigo (blue dye).
  1. Synthetic Dyes:
  • Definition: Colorful organic compounds synthesized or prepared in a laboratory or factory.
  • Examples: Methyl orange, Para red, etc.

Classification of Dyes:

  1. Nitro and Nitroso Dyes:
  • Definition: Dyes containing one or more Nitro (–NO2) or Nitroso (–NO) groups.
  • Examples: Martius Yellow (2,4-Dinitro-1-naphthol), Mordant Green (1-Nitroso-2-naphthol).

2. Azo Dyes:

  • Definition: Dyes containing one or more azo (–N=N–) groups.
  • Examples: Bismark Brown, Para-red, Orange-I, Methyl Orange.

3. Phthalein Dyes:

  • Definition: Dyes containing phthalein groups.
  • Examples: Phenolphthalein dye.

Drugs:

  • Definition: Substances used for the treatment or prevention of diseases and for reducing pain.

Types of Drugs:

  1. Antipyretics:
  • Definition: Drugs used to decrease body temperature.
  • Examples: Aspirin, Paracetamol.

2. Antimalarials:

  • Definition: Drugs used for the treatment of malaria.
  • Examples: Chloroquine, Paraquine.

3. Tranquilizers:

  • Definition: Drugs used for the treatment of mental diseases or disorders by reducing mental tension and anxiety.
  • Examples: Barbiturates, Vitalin, Cocaine, Opium, Heroin, Pethidine.

4. Antibiotics:

  • Definition: Drugs used for the treatment of diseases caused by microorganisms by inhibiting their growth or destroying them.
  • Types:
    • Broad Spectrum Antibiotics: Used when a bacterial infection is suspected but the specific bacteria are unknown.
    • Examples: Penicillin, Ampicillin, Azithromycin, Doxycycline, Ciprofloxacin, Metronidazole, Erythromycin, Amoxicillin-clavulanate, Cefixime, Chloramphenicol.
    • Narrow Spectrum Antibiotics: Used for specific bacterial infections.
    • Examples: Streptomycin, Amoxicillin, Tetracycline, Vancomycin, Fidaxomicin.

5. Analgesics:

  • Definition: Drugs used to decrease pain.
  • Examples: Brufen, Novalgin.
  • Note: Some antipyretics and narcotics also function as analgesics.

6. Anaesthetics:

  • Definition: Drugs used to produce general or local unconsciousness.
  • Examples: Chloroform, Ether, Cocaine, Novocain.

7. Germicides:

  • Definition: Substances used to kill or inactivate germs or microorganisms.
  • Types:
    • Antiseptics: Used in wounds, cuts, or diseased skin to kill or inhibit microorganisms.
    • Examples: Chloroxylenol (Dettol), tincture of iodine, methylene blue.
    • Disinfectants: Used to kill microorganisms on non-living surfaces.
    • Examples: 1% solution of phenol (for washing floors).

8.Sulfa Drugs:

  • Definition: Drugs acting against microorganisms similar to antibiotics.
  • Examples: Sulphadiazine, sulphaguanidine.

Names of Some Drugs

  1. Aspirin
  2. Paracetamol
  3. Novalgin
  4. Brufen
  5. Chloroxylenol (Dettol)
  6. Chloramphenicol
  7. Equanil
  8. Penicillin
  9. Sulphadiazine

Fertilizers:
Fertilizers are chemical substances added to soil to maintain its fertility and provide essential elements lost or used up due to continuous cropping.

Types of Fertilizers:

  1. Organic Fertilizers (Manure)
  2. Chemical Fertilizers

Chemical fertilizers contain nitrogen, phosphorus, potassium, calcium, etc., and can be categorized as follows:

  1. Nitrogen Containing Fertilizers (Nitrogen Fertilizer):
  • Plants need nitrogen for growth, increased protein content, and production of chlorophyll.
  • Examples: Ammonium sulphate ((\text{(NH}_4\text{)}_2 \text{SO}_4)), Calcium ammonium nitrate (\text{Ca(NO}_3\text{)}_2.\text{NH}_4\text{NO}_3).
  1. Phosphorus Containing Fertilizers (Phosphatic Fertilizer):
  • Plants need phosphorus to stimulate early root formation and early maturity.
  • Examples: Ammonium Phosphate ((\text{(NH}_4\text{)}_3 \text{PO}_4)), Super phosphate, Bone meal.
  1. Potassium Containing Fertilizers (Potash):
  • Plants need potassium to increase disease resistance.
  • Examples: Potassium Chloride ((\text{KCl})), Potassium sulphate ((\text{K}_2\text{SO}_4)), Potassium nitrate ((\text{KNO}_3)).
  1. Calcium Containing Fertilizers:
  • Soil needs calcium to reduce acidity and stimulate nitrogen-collecting microorganisms.
  • Example: Calcium oxide (CaO) or “Krishi Choon”.

NPK Fertilizer:
NPK fertilizer is a mixture of chemical fertilizers supplying nitrogen, phosphorus, and potassium. It is also known as Mixed Fertilizer.

Advantages of Organic Fertilizer Over Chemical Fertilizer:

  • Organic fertilizers are renewable, biodegradable, sustainable, and environmentally friendly.
  • Little to no risk of toxic buildups of chemicals and salts, unlike chemical fertilizers which may lead to toxic buildups of arsenic, cadmium, and uranium.
  • Organic fertilizers improve soil structure, water retention, and nutrient availability. Long-term use of chemical fertilizers can alter soil pH, disrupt beneficial microbial ecosystems, increase pests, and contribute to greenhouse gas emissions.
  • Organic fertilizers act as slow-release fertilizers, reducing the risk of over-fertilization, whereas chemical fertilizers can easily lead to over-fertilization, harming plants and ecosystems.

Fertilizers as Pollutants:

  • Nitrogen or nitrate-containing fertilizers can wash into nearby water resources, leading to increased algal growth. Decomposers consume excess dissolved oxygen as algae die, causing the death of aquatic animals due to oxygen depletion.
  • Drinking nitrate-rich water can cause dwarfism in children.

Pesticides

Pesticides:
Pesticides are chemical substances used to control pest activity in crops.

Types of Pesticides:

  1. Insecticides:
  • Used to kill insects.
  • Examples: DDT, BHC, Chloropyriphos.

2. Herbicides:

  • Used to kill or control unwanted herbs.
  • Examples: Copper sulphate (for dicotyledonous crops), Propylene (for paddy), Sodium nitrate (for wheat).

3. Fungicides:

  • Used to kill fungi.
  • Examples: DDT, Bleaching powder, phenol (2%).

4. Weedicides:

  • Used to kill weeds.
  • Examples: Chloropicrin, Bentazone, Glyphosate.

5. Rodenticides:

  • Used to kill rodents (rats).
  • Example: Zinc Phosphide (Zn3P2).