Cement:
The mixture of calcium silicate (fine grey) and calcium aluminate is called cement. Cement is prepared by heating calcium carbonate (CaCO₃ ) and special kind of clay (Al₂O₃ .SiO₂ ) at a temperature of 1600°C. Uses
Plastering of walls, between the bricks Used for roofing and flooring
Glass
Glass is the transparent homogeneous mixture of the silicates of alkaline and alkali metals. Ordinary glass is made from a mixture of 50% Silica, 15% Sodium Carbonate, 10% Calcium Carbonate and 25% glass pieces.
It's useful properties are as follows:
It is used in light bulbs and other objects.
It is used in laboratory apparatus, windowpanes, glass sheets etc
Hard glass is made by heating silica with potassium carbonate and calcium carbonate at 1500°C. Hard glass is used in making hard glass laboratory apparatus like test tubes, beakers and tube lightest.
Soft glass is made by the mixture of 50% Silica, 15% sodium carbonate, 10% calcium carbonate and 25% glass pieces. Soft glass is used in making windowpanes, light bulbs and other objects.
Ceramics
Ceramics is a special type of clay containing compounds of silica, nitrogen and oxygen. It is the clay made up of clay, feldspar, silicates. For the production of ceramics, clay is crushed, grinded and sieved to get fine clay. Then it is mixed in water to make a paste known as slip. The slip formed is molded into different shapes and dried. The hardened shapes are put into furnace and little salt is added to make it shiny. This makes porcelain non porous, smooth and shiny. Colors are added to make the ceramics objects attractive. Fibers
Fibers are the extremely long sand thin hair-like strands. Natural fibers are the fibers which are obtained from natural sources. Example: Animal fibers, Cotton fibers etc. Artificial fibers are the fibers which are made artificially. Example: Rayon, Nylon etc. Plastics
Plastic is widely used than any other materials because of its properties like transparency, lightness, less brittleness, non-decaying, harmless effect in body, colorfulness, flexibility, hardness, insulating heat and electricity etc.
Soap and detergents
Sodium and potassium salt of fatty acid is called soap . It is the sodium salt of long chain fatty acids that has cleansing property in water. Detergents are the soap less soaps because they have cleansing property in water like soap but their chemical nature is different from soap. In other words, any substance which removes dirt is known as detergents. They are sodium salts of long chain benzene sulphonic acids. Example: Sodium n-dodecyl benzene sulphonate, Sodium n-dodecyl sulphate.
Pesticides
Insecticides are used in killing insects that destroy the crops and eat the fruits. If not used properly it degrades the crops as well as the fertility of the soil and causes pollution. So, we should be careful while using insecticides. There are two types of insecticides. They are: Organic Insecticides and Inorganic Insecticides
Organic Insecticides: They are the synthetic compounds made up of carbon, hydrogen, and oxygen. There are three kinds of organic insecticides. They are chlorinated hydrocarbon, organic phosphate and carbamates. Example: BHC (Benzene hexachloride), DDT (Dichloro Diphenyl Trichloro ethane) etc.
Inorganic insecticides: Inorganic insecticides are made from minerals. They include calcium arsenate, lead arsenate, fluoride and lime sulphur. They are used in order to protect cotton, fruits vegetables etc. Example: Baygon, Temik etc.
Fertilizers
A good fertilizer not only supplies the essential nutrients required by the plant but also nourishes the micro organisms, which helps to maintain the fertility of the soil. It also improves the physical condition of the soil. So fertilizers are necessary for the maintaining the quality of the soil. There are two types of fertilizers. They are Organic fertilizers and Chemical fertilizers
Organic fertilizers: Organic fertilizers are the substance obtained from the decay of animals and plants or the waste products of animals. They provide necessary nutrients to plants. It can be further categorized into two types:
I. Green manure
II. Compost manure
Chemical fertilizers: Chemical fertilizers are the fertilizers, which are prepared artificially using inorganic compounds that are used in order to overcome the deficiencies of the plant nutrients. It can be further sub divided into three parts: a. Nitrogen fertilizers b. Phosphorous fertilizers c. Potassium fertilizers
Some important questions and their answers.
1. What are fibres?
Ans: Fibres are hair-like strands which are strong, flexible and extremely long in comparison to its width.
2. What is polymerization?
Ans: The process of preparation of polymer from monomers is called polymerization.
3. What are fertilizers?
Ans: The substances which are added in the soil to increase the fertility of soil are called fertilizers.
4. Write two-two examples of nitrogen fertilizers and phosphorus fertilizer.
Ans: The two examples of nitrogen fertilizers are:
a. Ammonium Nitrate (NH4NO3)
b. Ammonium Sulphate (NH4)2SO4
The two examples of phosphorus fertilizers are:
a. Ammonium Phosphate (NH4)3PO4
b.Calcium super phosphate Ca(H2PO4)2.2CaSO4
5. Define compost manure.
Ans: Compost manure is a kind of natural fertilizer which is prepared by mixing of cattle dung, poultry droppings and crop residue like remaining of the straw, rotten vegetables etc.
6. Define mixed fertilizers.
Ans: The fertilizers which contain more than one primary plant nutrients are called mixed fertilizers. For Eg: Ammonium hydrogen phosphate, potassium nitrate etc.
7. Write the full form of
a)DDT
b) BHC
c) PVC
Ans: a. Dichloro diphenyl trichloroethaneb) BHC
c) PVC
b. Benzene Hexachloride
c. Polyvinyl chloride
8. What are organic fertilizers? How do the chemical fertilizers trigger pollution?
Ans: Organic fertilizers are made by decaying plants and waste products of animals. They do not cause chemical pollution. Chemical fertilizers are made by using different chemicals. They cause chemical pollution.
9. Write the name of the fertilizers containing Potassium as their main constituent.
Ans: Potassium Nitrate (KNO3) and Potassium Sulphate(K2SO4)
10. Write the name of the fertilizers containing Nitrogen as their main constituent.
Ans: Urea (NH2CONH2) and Ammonium nitrate.(NH4NO3)
11. Write the name of the fertilizers containing Phosphorous as their main constituent.
Ans: Ammonium phosphate(NH4)3PO4 and Calcium super phosphate
12. What is NPK fertilizer?
Ans: The chemical fertilizer containing all plants nutrients ie. nitrogen, phosphorous and potassium is called NPK fertilizer. NPK fertilizer is also called the complete fertilizer.
13. Enlist the advantages and disadvantages of fertilizer.
Ans: The advantages of fertilizer are:
1. It promotes fast growth and development of plants.
2. It helps to increase the yield of crops.
3. It helps to resist disease.
The disadvantages of fertilizers are:
1. Low growth of plants
2. Reduce disease resistant power of the plants.
3. The wilting and withering of leaves.
14. Why is nitrogen required for plants?
Ans: Nitrogen is important to plants because it promotes fast growth and development of plants. It helps to form a large amount of protein and chlorophyll.
15. What are insecticides?
Ans: The poisonous chemical substances which are used to kill harmful insects are called insecticides.
16. What are mixed fertilizers?
Ans: Fertilizers having more than one plant nutrient elements are called mixed fertilizers.
17. What are organic insecticides?
Ans: The synthetic compounds which are composed of carbon, hydrogen and oxygen are called organic insecticides.
18. What are pests?
Ans: The harmful living organisms such as insects, rats, fungi, etc. are called pests.
19. What are pesticides? Write any one of its harmful effect.
Ans: Pesticides are the chemical compounds which are used to control or kill the pest.
Excessive use of pesticides can destroy crops and the fertility of soil.
eg.: Insecticides and Herbicides.
20. Enlist the disadvantages of pesticides.
Ans: The disadvantages of pesticides are:
1. It kills crops and the fertility of soil if they are used excessively.
2. It also kills non targeted animals and insects.
21. What are insecticides? Enlist the advantages of insecticides.
Ans: The poisonous chemicals which are manmade and used to control or destroy harmful insects are called insecticides.
The advantages of insecticides are:
1. They kill or destroy harmful insects quickly.
2. They help to control several diseases by killing germs.
3. They can destroy all the stages of the lifecycle of harmful insets. As result there is increase in crop yield.
22. What is cement?
Ans: Cement is a grey powder, made by heating a mixture of powdered limestone and a special type of clay, which sets hard when mixed with water.
23. What is cement clinker?
Ans: Cement clinker is a complex mixture containing calcium silicates and calcium aluminates.
24. What is concrete?
Ans: The mixture of cement, sand, gravel and water is known as concrete.
25. What is mortar?
Ans: The mixture of cement, sand and water is known as mortar. It is used as plastering material and to join bricks, stone etc.
26. What is cement? Why is gypsum added to it?
Ans: Cement is the mixture of fine gray powder of calcium silicate and calcium aluminates.
Gypsum salt is added in the cement because it slows down the setting time of the cement.
27. What are the raw materials used for the manufacture of cement?
Ans: Three main raw materials required for manufacture of cement are as follows:
• Limestone which is calcium carbonate, CaCO3
• Clay which is mainly a mixture of aluminium silicates containing alumina, Al2O3 and silica, SiO2
• Gypsum which is CaSO4.2H2O
28. Define cement clinker.
Ans: Cement clinkers is a mixture of pea sized balls which consists of calcium silicate and calcium aluminate .It is produces by heating a paste of calcium carbonate, clay and water in rotary kiln.
29. Define RCC.
Ans: RCC stands for Reinforced Concrete Cement. It is the concrete having an iron frame inside it as a support. It is very strong material for construction.
31. Define slurry.
Ans: Slurry is a material which makes the particle flow able.
32. What are the uses of cement in our daily life?
Ans: The uses of Cement are:
1. Cement is used for making houses, buildings, roads etc
2. It is used for flooring and roofing.
3. RCC is used for framework of iron rods.
4. It is used for making pillars, bridges etc.
33. Give any two differences between quick lime and slaked lime.
Ans:
| Quicklime | Slaked lime |
| 1. It is prepared by burning of calcium carbonate. | 1. It is prepared by reacting the calcium oxide with water. |
| 2. It is a metallic oxide. | 2. It is a hydroxide of metal. |
34. How is plaster of paris prepared? Write its uses.
Ans: Plaster of Paris (CaSO4. ½H2O) is prepared by heating gypsum (CaSO4.2H2O). It is used for making casts and patterns and for plastering the walls, pillars and ceilings and to make ornamental patterns on them.
35. Describe the processes involved during the manufacture of cement.
Ans: Limestone and clay are mixed in definite proportion and ground to a fine powdery state. This dry powder is used as such or mixed with water to form a paste and heated in a rotary kiln (a type of furnace). It is slowly made to pass through the kiln wherein limestone and clay combine chemically and form a mixture of calcium silicate, CaSiO3 and calcium aluminate, CaAl2O3. This mixture is in the form of small greenish black or grey-coloured hard balls known as clinkers. These clinkers are allowed to cool down and then ground to very fine powder. To this powder, 2-3% gypsum is added and the mixture is again ground to obtain a grayish coloured powder, which is cement. It is then packed in airtight bags to exclude the moisture. Gypsum is added to decrease the setting time of cement.
36. Define pollution.
Ans: Pollution is the contamination of environment by harmful substances. For eg: Air pollution, Water pollution etc.
37. What is chemical pollution? What are the causes of environmental pollution?
Ans: The environment pollution caused by various chemicals like insecticides, chemical fertilizers, synthetic cleanser and other industrial chemicals is called chemical pollution.
The causes of environmental pollution are:
1. The use of insecticides and fertilizers.
2. Household waste and plastics.
3. Smoke from vehicles and factories.
4. Synthetic cleanser.
38. “We, human beings can contribute to a great extent to control environmental degradation.” Justify with reasons.
Ans: Humans are more responsible to degrade the environment than other living beings on earth. Vehicles, big factories and large amount of chemicals that we use cause environmental degradation. To control environmental degradation, following steps can be used
a) We should dispose of non-biodegradable waste in proper place rather than throw them randomly.
b) Old vehicles should be replaced with new one so that air will not get polluted by carbon monoxide released by them.
c) Awareness campaign should be held so that people will get knowledge to protect the environment.
By adopting the above-mentioned points, we can contribute to a great extent to control the environmental degradation.
39. What is glass?
Ans: A glass is an amorphous, transparent, hard and homogeneous mixture of silicates of different alkaline earth metals.
41. Define pyrex glass.
Ans: The homogenous mixture of sodium silicate, calcium silicate and boron silicate is called borosilicate glass or Pyrex glass.
42. What is glass? What are the constituents of the ordinary glass?
Ans: A glass is an amorphous transparent homogenous mixture of silicates of alkali metals and silicates of alkaline earth metals.
Ordinary glass is the mixture of 50% silica, 15% sodium carbonate, 10% calcium carbonate and 25% glass piece.
43. What are the characteristics of the ordinary glass?
Ans: Ordinary glass is used for making laboratory apparatus, windowpanes, light bulbs, glass sheets etc.
44. What is water glass? How is it prepared?
Ans: A mixture of silica and sodium carbonate or potassium carbonate while heating at 8000C melts and forms sodium silicate or potassium silicate. It is soluble in water, so it is called water glass.
45. Differentiate between hard glass and soft glass.
Ans: The difference between the hard and soft glass is tabulated below:
| Soft Glass | Hard Glass |
| 1. It is produced by heating sodium carbonate and calcium carbonate with silica. | 1. It is obtained by heating potassium carbonate and calcium carbonate with silica. |
| 2. It is used for making window panes, mirror etc | 2. It is used for making heat-resistant equipment. |
46. How are the coloured glasses prepared? Which metallic oxide is used to prepare the blue glass?
Ans: Coloured glass is made by adding a small amount of various metallic oxides to the hot molten raw material used to manufacture glass. Cobalt oxide is used in preparing blue glass.
47. What type of glass is made for making eye lens and why?
Ans: Lead Crystal Glass (PbSiO3.K2SiO3) is used for making eye lens.
It is because it have more refractive index and is more resistant than the other type of glasses.
48. Write the name of industrial chemical formed by: i. Silica, Lead oxide and Potassium carbonate
Ans: The industrial chemical formed by silica, lead oxide and potassium carbonate is lead crystal glass.
49. What is the common name for borosilicate glass? Give two reasons why laboratory equipments are usually made from borosilicate glass.
Ans: The common name for borosilicate glass is Pyrex glass. Borosilicate glass is used to make laboratory equipments because
a. It is resistant to chemicals.
b. It can withstand high temperature.
50. Which glass will be formed if the mixture of silica and sodium carbonate is heated? Write its one special property and use.
Ans: When the mixture of silica and sodium carbonate is heated, water glass is formed. Water glass is soluble in water and it is used to make fire proof materials.
51. What is mean by hard glass and soft glass? Write their uses.
Ans: The glass which is made by heating of the mixture of potassium carbonate, calcium carbonate, and silica is called hard glass. It is used for making different types of laboratory equipment like a beaker, hard glass-test-tubes, etc. and electric bulbs and tube lights. The glass which is prepared by heating the mixture of sodium carbonate, calcium carbonate and silica is called soft glass. It is used for making bottles, windows pans, ordinary glass tubes, glass sheets, etc.
52. How is soda-lime glass manufactured?
Ans: The glass produced as given above is called sodalime glass or soft glass. It is used for manufacture of bottles ordinary crockery, ordinary laboratory glass apparatus like soda glass test tubes etc.
53. What changes are made in the raw materials in the manufacture of optical glass and Borosil glass? How is colour imparted to glass?
Ans: Borosilicate glass is sodium aluminium borosilicate and can withstand rapid heating and cooling. It is used for making kitchen and laboratory ware. Flint glass is used for making lenses, prisms, spectacles, etc. Coloured glass is made by adding small quantities of oxides of different metals.
54. Write short notes on: Borosilicate glass
Ans: It is sodium aluminium borosilicate. It can withstand rapid heating and cooling without breaking. It is used for making kitchenware and laboratory apparatus. It is sold under the trade names Borosil and Pyrex.
55. Write short notes on:
Flint or optical glass
Ans: It is used for making lenses, prisms, spectacles, etc. because of its excellent optical properties. It is composed of alkalis, lead oxide and silica. It is also known as flint glass. A superior variety of optical glasses is made by adding cerium oxide. It cuts harmful ultraviolet rays that are harmful to eyes. It is known as Crooke’s glass.
56. Write short notes on:
Hard glass
Ans: If instead of sodium carbonate, potassium carbonate is used for making glass another variety of glass known as a hard glass is produced. It can withstand very high temperatures. It is used for making hard glass laboratory apparatus like hard glass test tubes, beakers, conical flasks etc.
57. What is ceramics?
Ans: Ceramics is a special type of clay containing the compounds of carbon, nitrogen, silica and oxygen, which are used to make different objects like a cup, plate, dishes, etc.
58. Define bakelite.
Ans: Bakelite is made by condensation and polymerization of formaldehyde and carbonic acid. It is dark brown in color which is brittle and hard. It is used in electric fitting, to make handles of cook wares.
59. What is ceramics? How is glazing done?
Ans: Ceramics is the science of pottery which may be defined as objects made from a special type of clay, hydrated aluminium silicate, feldspar and silicates. The hard, brittle and porous article is heated and coated with a tin oxide or lead oxide which forms a thin layer over the surface. In this way, glazing is done.
60. Mention the uses of ceramics.
Ans: The uses of ceramics are:
1. Ceramics are used for making household pottery, jugs, tiles, bowls etc
2. It is used to make a furnace, as insulators in television sets etc
3. They are used for making artificial teeth, bone joints and porcelain.
61. ”Glazed pottery is superior to earthen pots.” Justify.
Ans: Glazed pottery is superior to earthen pots because they are hard, brittle and attractive. They are not affected by acids, alkali and other chemicals and they can withstand high temperature.
62. What are the uses of antibiotics in our daily life? Write with examples.
Ans: Antibiotics are medicines which are used to kill bacteria, fungi and moulds. The first antibiotic discovered was penicillin which is very effective for pneumonia, bronchitis, sore throat, etc. Ampicillin is a slight modification of penicillin. It has wider applications. Other commonly used antibiotics are streptomycin, tetracycline and chloramphenicol.
63. Define humus.
Ans: Humus is a large group of natural organic compound found in the soil formed from the chemical and biological decomposition of plants and animals residues and from the synthetic activities of micro organisms.
64. What is kaolin?
Ans: The pure white soil which is used to make ceramics is called kaolin.
65. Write any two differences between polythene and Bakelite.
Ans:
| Polythene | Bakelite |
| It becomes soft on heating. | It becomes hard on heating. |
| It can be remolded. | It cannot be remolded. |
66. Write any two differences between thermosetting and thermoplastic.
Ans:
| Thermosetting plastic | Thermoplastic |
| It becomes hard on heating. | It becomes soft on heating. |
| The articles made from thermosetting plastic cannot be remolded. | The articles made from thermoplastic can be remolded. |
67. What are fibres?
Ans: Fibres are hair-like strands which are strong, flexible and extremely long in comparison to its width.
68. What is polymerization?
Ans: The process of preparation of long chain of polymer from monomers is called polymerization.
69. What is monomer?
Ans: The small molecule of organic compound from which the polymer is obtained is known as monomer.
Or
Monomer is a small organic molecule which can combine together in large number to form a big molecule called polymer. For Eg: Ethene, styrene etc.
70. What is polymer?
Ans: Polymer is a large molecule which is formed by joining together a large number of similar small molecules.
Or
Polymers are big molecules formed when a large number of small molecules join together. Cotton, wool, terylene, etc. are some polymers. Nylon, polyesters, rubber and plastics are some important polymers.
71. What is plastic?
Ans: A plastic is a synthetic material, which can be moulded or set into any desired shape when soft, and then hardened to produce a durable article.
72. What is thermoplastic?
Ans: A plastic substance, which can be melted repeatedly by heating and can be moulded again and again into different shapes is called a thermoplastic.
73. What is thermosetting plastic?
Ans: A plastic substance, which once set, does not become soft on heating and cannot be moulded a second time is called thermosetting plastic.
74. What are natural fibres?
Ans: The fibres which are obtained from animals and plants are called natural fibres.
77. Define synthetic fiber.
Ans: Artificial fibre like nylon, polyester, arcylene and olefin that are prepared by a chemical process are called synthetic fibres.
78. Define polysterene.
Ans: It is a polymer of styrene. It is a hard, transparent and light plastic. It is used for making toys, thermos flask, ceiling tiles etc.
81. What is nylon?
Ans: Nylon is the first man made synthetic polyamide fibre made up of adipic acid and hexa methylene diamine. Nylon fibers are also called polyamide fibers. They are the first synthetic fibers. Nylon fibers are light in weight and strong.
Or
Nylon is a polymer of small monomeric units called amide (-CO-NH-) i.e. it is a polyamide. It is prepared by reaction of adipic acid and hexamethylenediamine. Terylene is crease resistant, durable and is not damaged by insects like moths and by mildew (fungi that form a white growth on plants and materials like cloth and paper).
82. Enlist the advantages of synthetic fibers.
Ans: The advantages of synthetic fibers are:
1. They are light in weight and strong.
2. They melt at low temperature.
3. They are used as fishing net, carpets etc.
83. Define plastics and enlist their uses.
Ans: Plastics are the artificial materials made by the polymerization of carbon containing monomers.
The uses of plastics are:
1. They are used as shopping bags.
2. They can be used as insulators in wires.
3. They are used as waterproof.
4. It is used in surgical cases.
84. Write the disadvantages of plastics.
Ans: The disadvantages of plastics are:
1. It non-biodegradable
2. It causes soil water and water pollution.
3. They are harmful to aquatic creatures.
85. Define non-biodegradable waste with an example.
Ans: Non biodegradable wastes are the poisonous substance which causes environment degradation. For Eg: Plastics and Detergent. These substances are not degradable in the environment.
86. Write down the difference between natural and artificial fibres.
Ans: The differences between natural and artificial fibres are as follows: Artificial fibres are of two types:
| Natural fibres | Artificial fibres |
| 1. Fibres, which are naturally found, are called natural fibres. | 1. The manmade fibres are called artificial fibres. |
| 2. Cotton and wool are natural fibres of own kind | 2. Artificial fibres are of two types: • Recycled fibres• Synthetic fibres |
| 3. It is comparatively less durable. | 3. It is comparatively more durable than natural fire. |
| 4. For natural fibre, we have to depend on nature. | 4. It can grow everywhere. No dependence on nature. |
87. PVC is not used to cover the handle of pressure cooker but Bakelite is used, why?
Ans: PVC is not used to cover the handle of pressure cooker but Bakelite is used because PVC becomes soft on heating while Bakelite becomes hard on heating and is bad conductor of heat.
88. Environmentalists request to avoid the use of plastics, why?
Ans: Environmentalists request to avoid the use of plastic because plastic is non-degradable substance which produces poisonous gas and pollutes the environment.
89. What is polyethene?
Ans: Polythene is a polymer made from ethene (CH2=CH2). It is one of the most commonly used materials. It is a soft plastic, which softens on heating. It is used for making bottles, buckets, and pipes, as covering for electrical wires and cables and as film for making bags.
90. What is Bakelite?
Ans: Bakelite (Phenol-formaldehyde resin) is made by reacting phenol and formaldehyde. It is hard and quite a strong material. It is used for making combs, electrical switches, and plugs and for making handles of many kitchen utensils and electrical appliances like pans, pressure cookers, electric irons, kettles, and toasters.
92. Write short notes on: Polysters
Ans: Polyesters are another category of polymers. One important member of this family is dacron which is also known as terylene. It is prepared by reaction between terephthalic acid and ethylene glycol. It is crease resistant, durable and is not damaged by insects like moths and mildew. Therefore, it is suitable for making garments because they can be set into permanent creases and pleats.
93. What are soaps?
Ans: Soaps are the sodium salts of long chain fatty acids which have cleansing properties in water.
94. What is saponification?
Ans: The process of making soap by the hydrolysis of fats and oils with alkali is called saponification.
95. What is soap? What are the raw materials required for the manufacture of soap?
Ans: Soap is the sodium salt of long chain fatty acids that have cleansing property in water.
The raw materials used for manufacturing soap are:
Animals fat or vegetable oil, sodium hydroxide, stearic acid, palmitic acid, oleic acid etc
96. How is the soap made harder?
Ans: Sodium carbonate or starch(also animal fat) is added to make soap harder.
97. Why is detergent called soapless soap?
Ans: Detergents are called the soap less soap because they have cleansing property in water like soap but their chemical nature is different from soap.
98. Differentiate between soap and detergent.
Ans: The difference between soap and detergent is tabulated below:
| Soap | Detergent |
| 1. It is a sodium or potassium salt of fatty acid. | 1. It is a synthetic petrochemical obtained from hydrocarbon. |
| 2. It is not suitable for washing purpose when the water is hard. | 2. Synthetic detergent can be used for washing ever when the water is hard. |
| 3. Soaps are biodegradable. | 3. It is not biodegradable. |
99. How is soap prepared?
Ans: Soap is made by heating oil with sodium hydroxide. The oil and sodium hydroxide solution are fed into an enclosed reaction vessel under high pressure and heated at high temperature. At this temperature, the reaction is completed in a few minutes. The mixture of soap and glycerol is cooled and a concentrated solution of sodium chloride is added. Glycerol dissolves readily in salt solution but soap does not. So, solid soap separates out from the mixture. It is then removed by centrifugation. While still hot it is sprayed into a hot vacuum chamber to dry it. Perfume is added and the particles are compressed into soap cake.
Or
Soap is the sodium or potassium salts of higher fatty acids e.g. sodium stearate. When some fats or oil is heated with sodium solution, it splits into the sodium salt of the higher fatty acid (i.e. soap) and glycerol.
Fat or oil + NaOH (or KOH) → Soap + Glycerol
100. Write short notes on:Cleansing action of soap and detergent.Ans:
Soaps and detergents form lather or foam with water. Lather removes grease and dirt particles from clothes. Water by itself cannot do it as it does not wet oily or greasy dirt. Addition of soap or detergents improves the wetting property of water and thus helps in removing oily or greasy dirt.
102. What is synthetic detergent?
Ans: Synthetic detergent is the sodium salt of a long chain benzene sulphonic acid or the sodium salt of a long chain alkyl hydrogen sulphate, which has cleansing properties in water.
103. What are detergents?
Ans: Detergents are the sodium salts of a long chain benzene sulphonic acid or long chain alkyl benzene sulphate which have more cleansing property in water.
104. Detergent is better than soap to wash clothes, why?
Ans: Detergent is better than soap to wash clothes because it has strong cleansing action than soap since it is more soluble in water than soap and does not form scum with hard water.