Man made substances

Man made substances

1. 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 [Ca3(PO4)2] and apatite [3Ca3(PO4)2 CaF2] are sparingly soluble in water and thus do not serve as 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 nitrogeneous fertilizers are ammonium sulphate, calcium cyanamide, ammonium nitrate, urea, calcium ammonium nitrate. Urea contains 46.6% nitrogen.
Potash Fertilizers Potassium gives the structural length to plants. Potassium nitrate, potassium choride and potassium sulphates etc are important potash fertilizers.
NPK Fertilizers Fertilizers containing N, P and K in suitable adjusted proportions are known as NPK fertilizers. These are obtained by mixing nitrogeneous, phosphatic and potash fertilizers in suitable proportions. Expression like 4-8-2 used for a mixed fertilizer indicates that it contains 4% N2, 8% P2O5 and 2% K2O
2. Dyes: Coloured substances used for colouring textiles, foodstuffs, silk, wool, etc. are called dyes.
Different classes of dyes are given below.
(a) Nitro These are polynitro derivatives of phenol where nitro group acts as a chromophore and hydroxyl group as auxochrome.
(b) Azo dyes: These are an important class of dyes and are characterised by the presence of azo group (—N=N—) as the chromophore. The groups like NH₂, NR, or –OH, etc., present in the molecule containing or more azo groups act as the auxochromes.
(c) Triphenylmethane dyes: These dyes contain the paraquinoid moiety as a chromophore and -OH, -NH2 or -NR2 as auxochrome. These dyes are not fast to light and 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.
(d) 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. Here 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.
(e) Vat dyes: These are water insoluble dyes and are introduced into the fibre in its (soluble) reduced form, also known as leuco form (colourless). These are called vat dyes because reducing operation (using sodium hydrosulphite) was formerly carried out in wooden vats. Indigo is a vat dye and is used for dyeing cotton.
3. Cement: It is a complex material containing the silicates of calcium and aluminium. A paste of it in water sets into a hard rocky mass-called the setting of cement. A paste of sand, cement and water called mortar, is very conveniently used 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.
In 1824, by an English Mason, Joseph Aspdin who observed that when strongly heated mixture of limestone and clay was mixed with water and allow to stand, it was 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 high percentage of lime with silica, iron oxide, alumina etc.
Cement factory workers are prone to Cytosilicosis.
The function of cement in masnory is based on the phenomenon of Adhesion.
Main constituents of cement are following-
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 (Na3O)-1.0%, Potassium oxide (K2O)-1.0%
4. Glass Supercooled liquid is called glass. SiO2 is its common constituent.
(a) Soda glass or soda lime glass: It is Sodium calcium silicate (Na2O CaO5 SiO2). It is the cheapest of all glasses and used for making window panes and bottles and easily attacked by chemicals.
(b) Potash glass: It contains potassium in place of sodium. it has higher softening temperature as also a greater resistance to chemicals. So it is used for chemical apparatus; beakers, flasks, funnels etc.
(c) 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: 1. Crown glass : Contains K2O & BaO as the basic oxide
2. Flint glass: Contains PbO as the basic oxide.
(d) Crooks glass for spectacles Absorbs ultraviolet rays which are harmful for the eyes.
(e) Lead crystal and crystal glass : Lead glass sparkles used for making decorative items. It contains 24% or more of PbO called lead crystal. If it contains term than 24% lead oxide called crystal glass.
(f) Borosilicate glass : It contains less alkali (K2O or CaO) and more SiO2 than potash glass and some B2O3.
(g) Coloured glass : photo
It is used for making artificial jewellery, crockery and stained glass windows.
(h) Milky glass: Milky glass is prepared by adding tin oxide (SnO2). Calcium phosphate Ca3(PO4)2 or cryolite (AlF33NaF) to the melt glass. All these substances are white so look milky.
(i) Glass laminates: It is made by fixing polymer sheets between layers of glass. It is used to make windows & Screens of cars, trains and aircraft specially manufactured glass laminates are used bulletproof material.
Polymerisation: The simple molecules which combine to form a macro molecule is called polymer. The process by which the simple molecules (monomers) are converted polymer is called polymerisation.
Natural occurring polymers are protein, nucleic acid, cellulose, starch etc.
Plastics : Plastics are cross linked polymers and are very tough. Lac is a natural plastic chemically plastic can be of two types.
1. Thermoplastic .          2. Thermosetting plastics
1. Thermoplastic: These are the polymers which can be easily softened repeatedly when heated and hardened when cooled with little change in their properties.
Examples – Polyethylene, polystyrene, polyvinyl chloride, teflon. etc.
2. Thermosetting plastics : These are the polymers which undergo permanent change on heating. On heating they undergo extensive cross linking in moulds and become hard and infusible therefore, they can not be reused.
Examples-Bakelite, glyptal, terrylene etc.
Bakelite (Phenol-formaldehyde resins): It is a condensation polymer and is obtained from phenol and formaldehyde in presence of either an acid or a base catalyst. It is used for making combs, fountain pens, photographs records, electrical goods etc.
Rubber: It is a polymer which is capable of returning to its original length, shape or size after being stretched or deformed. The rubber obtained from natural sources are called natural rubber and polymer prepared in laboratory which are similar to natural rubber are known as synthesize rubber.
Vulcanization of rubber: Natural rubber is soft and sticky and therefore, in order to give strength and elasticity Natural rubber is vulcanized. Vulcanization is a process of treating the natural rubber with sulphur or some compound of sulphur (SF6) under heat. Vulcanized rubber is used for manufacturing rubber bands, gloves, car, tyres etc.
Fibres Fibres are the polymers which have quite strong intermolecular forces such as hydrogen bonding. Nylon-6,6, dacron, orlon etc are the examples of this type.
Rayon : Synthetic fibre obtained from cellulose is known as Rayon.
Teflon is common name of polyterafluoro ethyline.
Natural rubber
Natural rubber is a linear polymer of isoprene (2-methy-1, 3-butadiene) and is also called as cis-1, 4-polyisoprene. The cis-poly isoprene consists of various chains held together by weak vanderwaal’s interaction and has a coil structure. Thus, it can 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 rubber tree which is found in India, Srilanka, Indonesia, Malaysia and South America.
Synthetic rubber
Synthetic rubbers are Neoprene, Buna-S, Buna-N, and Thiokol.
Neoprene is a polymer of chloroprene (2-chloro-1, 3butadiene) and is also called polychloroprene. Thiokol is prepared by copolymerisation of ethylene dichloride with sodium tetrasulphide (Na₂S). It is slso called polysulphide rubber.
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. Zinc oxide, white lead and titanium oxide are the commonly used white pigments. The pigments is mixed with oil like linseed or soya bean oil or a polymer. A thinner is a solvent such as turpentine oil or kerosene. It makes the paint more fluid so that it may be applied easily.
Luminous paints: Glow when exposed to light, paints are applied on a surface to protect it from corrosion and weathering or to give it an attractive look.
Soap and Detergents
Soaps are generally the sodium or potassium salts of high fatty acids such as Palmitic acid (C15 H31COOH), Oleic acid (C17H33COOH) and Stearic acid (C17H35COOH). The potassium salts of these acids are called soft soaps or toilet soaps while the corresponding sodium salts are called hard and are used as washing soaps.
Soaps are normally manufactured from edible oils such as ground nut oil, til oil etc. by a reaction called saponification.
The saponification reaection gives soap in colloidal form only. The separation of soap from glycerol can be done with the help of process known as salting out of soap.
1. In toilet soaps (soft soaps) oils of better quality are used and alkali is potassium hydroxide.
2. Some soaps look transparent. This can be achieved by dissolving the soap in ethanol.
3. In shaving soaps, glycerol is added in small amount so that soap may become sticky and may not dry quickly. A gum known as reosin is added in their manufacturing process. It forms a compound sodium resonate which gives enough lather needed in shaving.
4. Substances known as fillers are added to launday soaps. They may be sodium silicate, borax or sodium carbonate.
5. Soaps form Lather easily in soft water but in a hard water, a lot of soap gets wasted. Hard water contain bicarbonates, sulphates and chlorides of calcium or magnesium. When soap is added to hard water, the soluble sodium salts of higher fatty acids present in the soap are converted to their calcium or magnesium salts. These are no longer soluble in water and form precipitates. Thus, a lot of soap get wasted without forming any lather. Even hair washed with soap dissolved in hard water look dull and sticky because soap particles stick to these.
6. The soap micelles are large enough to scatter light. Hence a soap solution appears cloudy.
Synthetic detergents are also called soap-less soaps because they actlikesoapinhaving similar cleaning properties but do not contain the usual soaps. These are better cleaning agents than soaps because they can also be used in case of hard water. Actually, detergents are the sodium sulphonates or sulphates of the long chain hydrocarbons. When added to hard water, they change into the corresponding calcium and magnesium salts. Since these dissolve in water, detergents are not wasted unlike soaps. There fore, readily form lather and can be used in hard water as well.
(i)Synthetic detergents can be used in acidic medium while soaps fail to do so because of their hydrolysis to free acids.
(ii) Synthetic detergents are more soluble in water and hence form better lather than soaps.
(iii) Although detergents are better than soaps in many ways, they have some harmful effects as well. These are mostly non-biodegradable and are not decomposed by micro-organisms like bacteria. As a result, they cause water pollution which is harmful for the aquatic life. Soaps on the other hand are bio-degradable and do not cause water pollution.
Transquilizers
Transquilizers are chemical compounds used for the treatment of stress and mild or even serve mental diseases. These relieve anxiety, stress, irritability or excitement by inducing a sense of well-being. They form an essential component of sleeping pills. Noradrenaline, Iproniazid, Phenelzine (Nardil) etc. are example of transquilizers.
Analgesics
Analgesics are neurologically active pain killing drugs. They reduce or abolish pain without causing impairment of consciousness, mental confusion, incoordination or paralysis or some other disturbance of nervous system. These are classified as (i) Non-narcotic and (ii) narcotic drugs. Aspirin and paracetamol are non-narcotic analgesics. Morphine, Heroin and Codeinine are narcotic drugs.
Antipyretics
Antipyretics are chemical substances used to bring down the body temperature in case of high fever. Analgin, phenacetin and Paracetamol are antipyretics.
Antibiotics
Medicinal compounds produced by moulds, bacteria, capable of destroying or preventing the growth of bacteria in animal systems are called antibiotics. Penicillin was the first discovered antibiotic by Alexander Fleming in 1929 from mould penicillium notatum. Some common antibiotics are streptomycin, neomycin, chloromycetin, erythromycin ampicillin, ciprofloxacin and rifampicin. Chloramphenicol isolated in 1947, is a broad spectrum antibiotic.
Antiseptics
Antiseptics are the chemicals which either kill or prevent the growth of micro-organisms. They can be safely applied on living tissues. These are widely used for the dressing of wounds, cuts and diseased skin surfaces. Examples are furacine, soframicine etc. Commonly used antiseptics are dettol, Bithionol, Tincture of iodine, Iodoform, Boric acid etc. Dettol is a mixture of chloroxylenol and terpineol. Bithionol is added to soap to impart antiseptic properties, Iodine is a powerful antiseptic. Its 2-3% solution in alcohal-water mixture is known as tincture of iodine. It is applied on wounds. Iodoform is also used as an antiseptic for wounds. Boric acid in dilute aqueous solution is weak antiseptic for eyes.
Disinfectants
Disinfectants are chemical substances which kill microorganisms but not safe for contact with living tissues. These are used only on inanimate (non-living) objects such as floors, drainage system instruments etc. Same substances can act as antiseptic as well as disinfectants by varying the concentration. For example 0.2 % solution of phenol is an antiseptic while its 1% solution is disinfectants.
Chlorine is used in India for making water fit for drinking at a concentration of 0.2 to 0.4 ppm (part per million). Low concentration of sulphur dioxide is used for sterlizing squashes for preservation. Formaldehyde (HCHO) in the gaseous form is used for disinfecting wards, rooms in hospitals and also the operation theatres.
Antifertility Drugs
Antifertility drugs are birth control pills essentially contain a mixture of synthetic estrogen and progesterone derivatives. Both of these compounds are hormones. Progesterone suppresses ovulation. Synthetic progesterone derivatives are more potent than progesterone. Norethindrone is an example of synthetic progesterone derivative most widely used as antifertility drug. The estrogen derivative which is used in combination with progesterone derivative is ethynylestradiol (novestrol).
Antacids
Over production of acid in the stomach causes irritation and pain. Hyperacidity leads to the formation of ulcers in stomach of the most of the patients. The role of the antacids is to neutralise the acidity and raise the pH level. Thus, antacids are chemical substances which can reduce or neutralise the acidity in the stomach and raise the pH to some appropriate level. The most commonly used antacids are sodium hydrogen carbonate (NaHCO3), magnesium hydroxide (Mg(OH)2) and aluminium hydroxide (Al(OH)3).
Pesticides
Pests include insects (like ants and cockroaches) and fungi (like the one that affects potato leaves). To kill them we use insectides and fungicies respectively. Rodents like rats, mice and moles are also pests. They eat up grain stored in granaries and our home. Rodenticides are used to kill rodents. Unwanted plants in crop fields are called weeds. Weeds affect the growth of crops by consuming nutrients from soil. They are destroyed by using herbicides. Insecticides, fungicides, herbicedes and rodenticides are collectively known as pesticides.
Insecticides:D.D.T.aluminiumphosphate, gammexane, micotine, aldrin, dieldrin.
Fungicide: Thiram, Bordeanx mixture CaSO4·5H2O + Ca(OH)2.
Herbicides: Benzipram, benzadox, sodium chlorate (NaClO3), sodium arsinite (Na3AsO3).
Rodenticides: Aluminium phosphide.
Artificial sweetners
Natural sweetners e.g sucrose are the traditional sweetners and are essential constituents of our diet. In present life style, people lack physical activities and exercise and it becomes rather difficult to burn the extra calories that are produced by the sucrose. Therefore, chemists have provided certain chemicals known as artificial sweetners which prove the desired sweet taste to the food articles but hardly affect the calorie intake by the body. Saccharin, Aspartame, Alitame, Sucroloseetc are artificial sweetners.
The saccharin is first most popular artificial sweetener. It is 550 times more sweet than sugar. It is a boon for diabetic patients which do not want to take carbohydrates. Aspartame is 100 times as sweet as cane sugar. It can be used in soft drinks and cold food only, since it decomposes upon heating.
Sucralose is 600 times as sweet as cane sugar. It is better artificial sweetner than aspartame in the sense that it can be used in hot food at the cooking temperature since it does not decompose on heating.
Alitamine is 2000 times as sweet as cane sugar. However, it is very difficult to control its quality that should be used in different food materials.
Food Preservatives
Food preservatives prevent spoilage of food due to microbial growth. The most commonly used preservatives include table salt, sugar, vegetable oils and sodium benzoate (C6H5COONa). Sodium benzoate is used in limited quantities and is metabolised in the body. Salts of sorbic acid and propanoic acid are also used as preservatives.

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