Man-Made Substances Explained

Man-Made Substance

Fertilizers

The substances added to the soil to make up the deficiency of essential elements are known as fertilizers. These are either natural or synthetic (chemical).

For a chemical fertilizer, the following requirements should be met:

(a) It must be sufficiently soluble in water.

(b) It should be stable so that the element in it may be available for a longer time.

(c) It should contain nothing injurious to plants.

Phosphatic Fertilizers

The minerals of phosphorous such as phosphorite [Ca₂(PO₄)₂] and apatite [3Ca₂(PO₂)₂CaF] are sparingly soluble in water and thus serve as a source of phosphorous for plants. Therefore, these are converted into soluble materials which can act as good fertilizers.

Important phosphatic fertilizers are:

1. Calcium superphosphate

2. Nitrophosphate

3. Triple phosphate

4. Phosphatic slag

Nitrogenous Fertilizers

Plants need nitrogen for rapid growth and increase in their protein content. For this reason, nitrogenous fertilizers become more important.

The chief nitrogenous fertilizers are:

• Ammonium sulphate

• Calcium cyanamide

• Ammonium nitrate

• Urea

• Calcium ammonium nitrate

Note: Urea contains 46.6% nitrogen.

Potash Fertilizers

Potassium gives the structural strength to plants.

Important potash fertilizers are:

• Potassium nitrate

• Potassium chloride

• Potassium sulphates

NPK Fertilizers

• Fertilizers containing N, P, and K in suitable adjusted proportions are known as NPK fertilizers.

• These are obtained by mixing nitrogenous, phosphatic, and potash fertilizers in suitable proportions.

Example: Expression like 4-8-2 used for a mixed fertilizer indicates that it contains 4% N₂, 8% P₂O₅, and 2% K₂O.

Dyes

Coloured substances used for colouring textiles, foodstuffs, silk, wool, etc. are called dyes.

Different classes of dyes

Nitro dyes:

• These are polynitro derivatives of phenol where the nitro group acts as a chromophore and the hydroxyl group as auxochrome.

Azo dyes:

• These are an important class of dyes and are characterised by the presence of the azo group (-N=N-) as the chromophore. Groups like -NH₂, -NR₂, or -OH present in the molecule, or more azo groups, act as auxochromes.

Triphenylmethane dyes:

• These dyes contain the paraquinoid moiety as a chromophore and -OH, -NH₂, or -NR₂ as auxochrome.

• These dyes are not light washing and hence are mainly used for colouring paper or typewriter ribbons, e.g., malachite green, which is used for dyeing wool and silk directly and cotton after mordanting with tannin.

Mordant dyes:

• Those dyes which are fixed on the fibre with the help of a mordant are known as mordant dyes.

• For acidic dyes, basic mordants (such as hydroxides of iron, aluminium, and chromium) are used, while for basic dyes, acidic mordants (like tannic acid) are used.

• The fabric is first dipped into a solution of mordant and then into the dye solution. The colour produced depends on the nature of the mordant used.

Vat dyes:

• These are water-insoluble dyes and are introduced into the fibre in its soluble reduced form, also known as leuco form (colourless). They are called vat dyes because the reducing operation (using sodium hydrosulphite) was formerly carried out in wooden vats.

• Indigo is a vat dye and is used for dyeing cotton.

Cement

Cement is a complex material containing the silicates of calcium and aluminium. A paste of it in water sets to a hard rocky mass, called the setting of cement.

• A mix of sand, cement, and water, called mortar, is very convenient for joining bricks and plastering walls.

• A mixture of stone chips (gravel), sand, cement, and water, known as concrete, sets harder than ordinary mortar. It is used for flooring and making roads.

• Concrete with steel bars and wires, called reinforced concrete (RC), forms a very strong material. It is used for constructing roofs, bridges, and pillars.

History

• In 1824, by an English mason, Joseph Aspdin observed that when a strongly heated mixture of stone and clay was mixed with water and allowed to stand, it hardened to a stone-like mass which resembled Portland rock—a famous building stone of England.

• Since then, the name Portland cement has been given to a mixture containing a high percentage of lime with silica, iron oxide, alumina, etc.

Caution: Cement factory workers are prone to Cytosilicosis.

The function of cement in masonry is based on the phenomenon of adhesion.

Main constituents of cement

• Lime (CaO) – 62%

• Silica (SiO₂) – 22%

• Alumina (Al₂O₃) – 7.5%

• Magnesia (MgO) – ≤ 2.5%

• Iron oxide (Fe₂O₃) – ≤ 2.5%

• Sulphur trioxide (SO₃) – ≤ 1.5%

• Sodium oxide (Na₂O) – 1%

• Potassium oxide (K₂O) – ≤ 1%

Glass

Supercooled liquid is called glass. SiO₂ is its common constituent.

Types of Glass

1. Soda Glass or Soda Lime Glass

• It is Sodium calcium silicate (Na₂O·CaO·5SiO₂). It is the cheapest of all glasses and used for making window panes and bottles and easily attacked by chemicals.

2. Potash Glass

• It contains potassium in place of sodium. It has higher softening temperature as well as greater resistance to chemicals. So it is used for chemical apparatus, beakers, flasks, funnels, etc.

3. Optical Glass

It is used for making lenses, prisms, and optical instruments like telescopes and microscopes. It contains boric oxide (B₂O₃) and silica (SiO₂).

Types of Optical Glass:

• Crown glass: K₂O is the basic oxide.

• Flint glass: Contains PbO as the basic oxide.

• Crooks glass: For spectacles; absorbs ultraviolet rays which are harmful to the eyes.

• Lead crystal and crystal glass: Lead glass sparkles and is used for decorative items. Lead crystal contains ≥24% PbO; if <24%, called crystal glass.

4. Borosilicate Glass

• It contains less alkali (K₂O, CaO) and more SiO₂ than potash glass and some B₂O₃.

5. Coloured Glass

Substances added to the glass include:

• Selenium (Se) or copper(I) oxide (Cu₂O)

• Chromium(III) oxide (Cr₂O₃)

• Manganese(IV) oxide (MnO₂)

• Copper(II) oxide (CuO) or cobalt oxide (CoO) – Brown

• Iron(III) oxide (Fe₂O₃)

Used for artificial jewellery, crockery, and stained glass windows.

6. Milky Glass

• Prepared by adding tin oxide (SnO₂), calcium phosphate (Ca₃(PO₄)₂), or cryolite (AlF₃·3NaF) to the melt.

• All these substances are white, so the glass looks milky.

7. Glass Laminates

• Made by placing polymer sheets between layers of glass.

• Used for windows & screens of cars, trains, and aircraft. Specially manufactured glass laminates are used as bulletproof material.

Polymerisation

The simple molecules which combine to form a macromolecule are called polymers. The process by which simple molecules (monomers) are converted into polymers is called polymerisation.

Example:

CH₂= CH₂ → Polymerisation → (-CH₂- CH₂-)ₙ

Naturally occurring polymers: Protein, nucleic acid, cellulose, starch, etc.

Plastics

Plastics are cross-linked polymers and are very tough. Lac is a natural plastic. Chemically, plastics can be of two types:

1. Thermoplastic

• Polymers which can be softened repeatedly when heated and hardened when cooled with little change in properties.

Examples: Polyethylene, polystyrene, polyvinyl chloride, Teflon.

2. Thermosetting Plastics

• Polymers which undergo permanent change on heating. They undergo extensive cross-linking in moulds, become hard and infusible, and cannot be reused.

Examples: Bakelite, glyptal, terrylene.

Bakelite (Phenol-Formaldehyde Resin)

It is a condensation polymer obtained from phenol and formaldehyde in presence of either acid or base catalyst. Used for combs, fountain pens, photograph records, electrical goods, etc.

Rubber

Rubber is a polymer capable of returning to its original length, shape, or size after being stretched or deformed.

• Natural rubber: Obtained from natural sources.

• Synthetic rubber: Prepared in the laboratory to mimic natural rubber.

Vulcanization of Rubber

Natural rubber is soft and sticky, so to give strength and elasticity, it is vulcanized.

• Process: Treating natural rubber with sulfur (S₆F₆) under heat.

• Uses: Rubber bands, gloves, car tyres, etc.

Fibres

Fibres are polymers with strong intermolecular forces, such as hydrogen bonding.

Examples: Nylon-6,6, Dacron, Orlon, etc.

• Rayon: Synthetic fibre obtained from cellulose.

• Teflon: Common name of polytetrafluoroethylene.

Rubber

Natural Rubber

• Natural rubber is a linear polymer of isoprene (2-methyl-1,3-butadiene) and is also called cis-1,4-polyisoprene.

• The cis-polyisoprene consists of various chains held together by weak van der Waals interactions and has a coil structure, allowing it to be stretched like a spring and exhibit elastic properties.

• Natural rubber is manufactured from rubber latex, which is a colloidal dispersion of rubber in water. This latex is obtained from the bark of the rubber tree found in India, Sri Lanka, Indonesia, Malaysia, and South America.

Synthetic Rubber

Synthetic rubbers include Neoprene, Buna-S, Buna-N, and Thiokol.

• Neoprene: Polymer of chloroprene (2-chloro-1,3-butadiene), also called polychloroprene.

• Thiokol: Prepared by copolymerisation of ethylene dichloride with sodium tetrasulphide (Na₂Sₓ), also called polysulphide rubber.

Common Man-Made Polymers and Their Uses

Polymer	Use
Polythene	Packaging material, carry bags, bottles
Polypropene	Bottles, Crates
Polyvinyl chloride (PVC)	Pipes, insulation
Nylon (Polyester)	Fibres, ropes
Teflon	Nonstick kitchenware
Vinyl rubber	Rubber erasers
Polystyrene	Foam, Thermocole
Poly(Styrene butadiene)	Rubber, bubble gum
Bakelite	Electrical insulation, buttons
Lexan	Bulletproof glass
Melamine	Crockery

Paints

Paints can be applied on a surface to protect it from corrosion and weathering or to give it an attractive look.

• A paint contains a pigment, a vehicle, and a thinner.

• Pigments: Zinc oxide, white lead, titanium oxide.

• Vehicle: Oil like linseed or soybean oil or a polymer.

• Thinner: Solvent such as turpentine oil or kerosene for easier application.

Luminous Paints

• Glow when exposed to light; also protect surfaces and enhance appearance.

Soap and Detergents

Soaps

Soaps are generally the sodium or potassium salts of high fatty acids such as Palmitic acid (C₁₆H₃₂COOH), Oleic acid (C₁₈H₃₄COOH), and Stearic acid (C₁₈H₃₆COOH).

• Potassium salts: Soft soaps or toilet soaps

• Sodium salts: Hard soaps used for washing

Manufacturing of Soap

Soaps are normally manufactured from edible oils such as groundnut oil, til oil, etc., by saponification:

(Oil or fat) + NaOH → glycerol + soap

• Salting out: Separates soap from glycerol.

• Toilet soaps: High-quality oils + potassium hydroxide.

• Transparent soaps: Dissolve soap in ethanol.

• Shaving soaps: Add glycerol for stickiness and reosin for lather.

• Laundry soaps: Fillers like sodium silicate, borax, or sodium carbonate.

Soap in Hard Water

• Hard water contains bicarbonates, sulphates, and chlorides of Ca or Mg.

• Sodium salts convert to insoluble Ca or Mg salts, forming precipitates, wasting soap.

• Soap micelles scatter light, making solutions appear cloudy.

Synthetic Detergents

• Also called soap-less soaps, act like soap but do not contain traditional soaps.

• Advantages: Work in hard water, acidic media, more soluble, form better lather.

• Disadvantages: Mostly non-biodegradable, can cause water pollution affecting aquatic life.

• Soaps, in contrast, are biodegradable and safe for the environment.

Tranquilizers

Tranquilizers are chemical compounds used for the treatment of stress and mild or even severe mental diseases. These relieve anxiety, stress, irritability, or excitement by inducing a sense of well-being. They form an essential component of sleeping pills.

• Examples: Noradrenaline, Iproniazid, Phenelzine (Nardil).

Analgesics

Analgesics are neurologically active pain-killing drugs. They reduce or abolish pain without causing impairment of consciousness, mental confusion, incoordination, or paralysis.

Classification

1. Non-narcotic analgesics: Aspirin, Paracetamol.

2. Narcotic analgesics: Morphine, Heroin, Codeine.

Antipyretics

Antipyretics are chemical substances used to bring down the body temperature in case of high fever.

• Examples: Analgin, Hanacetin, Paracetamol.

Antibiotics

Medicinal compounds produced by moulds or bacteria, capable of destroying or preventing the growth of bacteria in animals, are called antibiotics.

• Discovered by Alexander Fleming in 1929.

• Penicillin from mould Penicillium notatum.

• Common antibiotics: Ampicillin, Ciprofloxacin, Rifampicin, Chloramphenicol, Streptomycin, Neomycin, Chloromycetin, Erythromycin.

• 1947: Broad-spectrum antibiotics were related.

Antiseptics

Antiseptics are chemicals that either kill or prevent the growth of micro-organisms and can be safely applied on living tissues.

Examples: Furacine, Soframicine, Dettol, Bithionol, Tincture of Iodine, Iodoform, Boric acid.

• Dettol: Mixture of chloroxylenol and terpineol.

• Bithionol: Added to soap for antiseptic properties.

• Tincture of iodine: 2-3% alcohol-water solution used on wounds.

• Boric acid: Weak antiseptic for eyes.

Disinfectants

Disinfectants are chemical substances that kill micro-organisms but are not safe for living tissues, used only on inanimate objects.

• Some substances can act as antiseptics or disinfectants depending on concentration:

  • 0.2% phenol → antiseptic

  • 1% phenol → disinfectant

Examples:

• Chlorine: Water purification (0.2-0.4 ppm).

• Sulphur dioxide: Sterilizing squashes.

• Formaldehyde (HCHO): Disinfecting hospital wards and operation theatres.

Antifertility Drugs

Antifertility drugs are birth control pills containing synthetic estrogen and progesterone derivatives.

• Progesterone: Suppresses ovulation.

• Synthetic progesterone derivatives: More potent.

  • Example: Norethindrone

• Estrogen derivative: Ethynylestradiol (Novestrol) used in combination with progesterone derivative.

Antacids

Overproduction of acid in the stomach causes irritation, pain, and ulcers.

• Antacids neutralize acidity and raise pH level.

• Common antacids: Sodium hydrogen carbonate (NaHCO₃), Magnesium hydroxide (Mg(OH)₂), Aluminium hydroxide (Al(OH)₃).

Pesticides

Pests include insects, fungi, rodents, and unwanted plants (weeds).

Types of Pesticides

1. Insecticides: D.D.T., Aluminium phosphate, Gammesane, Nicotine, Aldrin, Dieldrin.

2. Fungicides: Thiram, Bordeaux mixture (CaSO₄·SHO + Ca(OH)₂).

3. Herbicides: Benzipram, Benzadox, Sodium chlorate (NaClO₃), Sodium arsenite (Na₃AsO₃).

4. Rodenticides: Aluminium phosphide.

Artificial Sweeteners

Artificial sweeteners provide sweet taste without adding significant calories.

• Examples: Saccharin, Aspartame, Alitame, Sucralose.

• Saccharin: 550 times sweeter than sugar, good for diabetics.

• Aspartame: 100 times sweeter, used in soft drinks and cold foods.

• Sucralose: 600 times sweeter, can be used in hot foods.

• Alitame: 2000 times sweeter, difficult to control quality.

Food Preservatives

Food preservatives prevent spoilage due to microbial growth.

• Common preservatives: Table salt, sugar, vegetable oils, Sodium benzoate (CH₃COONa).

• Sodium benzoate: Used in limited quantities, metabolized in the body.

• Other preservatives: Salts of sorbic acid and propanoic acid.

Final Thoughts

Man-made substances play a vital role in modern life, from fertilizers that boost soil fertility to materials like cement, glass, and plastics that shape our infrastructure. Fertilizers such as nitrogenous, phosphatic, and potash types enhance plant growth, while dyes bring colour to fabrics and food. Cement and glass are key in construction, offering durability and versatility.

Polymers, including plastics, fibres, and rubbers, serve countless uses — from daily household items to industrial applications.

Essential chemical compounds like soaps, detergents, medicines, and antiseptics ensure hygiene and health, while artificial sweeteners and preservatives improve food safety and quality, making life more convenient and sustainable.