- Cement is a fine gray powder of Calcium Silicate(2CaO.SiO2) and Calcium Aluminate (5CaO.3Al2O3), which becomes hard when mixed with water and dried for some time.
- For the manufacture of cement,calcium carbonate(CaCO3) and special type of clay(Al2O3.SiO2) are taken in the ratio 2:1.These two are then powdered and mixed with water to form a paste called slurry. The slurry is then put into a rotary furnace called kiln and heated to 16000C. After heating, a mixture of Calcium Aluminate and Calcium Silicate is formed which is called cement clinker. Finally 1-2% gypsum is added & the mixture is grinded to form cement.
- Chemically cement is a mixture of calcium silicate and calcium aluminate
- During manufacture of cement when slurry is heated in the furnace, it changes into lump of chemical which is called cement clinker. By grinding the cement clinker with gypsum salt (1-2%) cement is made.
- Uses of cement are:
- A mixture of cement, gravel, pebble and water is called concrete, which is used for roofing and flooring.
- A thick paste of cement, sand and water is called mortar which is used for plastering walls and to join bricks, stones etc.
- Cement is used in the construction of buildings, roads, bridges etc.
- Gypsum is added in the manufacture of cement to increase the setting time of cement. It makes convenient to use the cement.
- Cement Mortar: The thick paste of cement, sand(1:3) and water is known as cement mortar. It is used for plastering of walls, joining bricks, stones etc.
- Cement Concrete: The mixture of cement, sand, water and gravel is known as cement concrete. It is used for roofing of buildings and making pillars.
- Reinforced Cement Concrete (RCC): The mixture of cement, sand, water and gravel (cement concrete) having an iron framework inside is called RCC. It is used for making roofs and pillars.
- Glass is a metallic silicate of various metals. It is hard,transparent, amorphous and supercooled liquid.
- Glass in an important industrial substance which is used in making windows, laboratory equipments, mirrors, domestic utensils, etc
- The main raw material for the manufacture of glass is silica ( ).
# Water Glass
- A mixture of silica ( ) and sodium carbonate ( ) or potassium carbonate ( ) melts on heating at high temperature and forms sodium silicate or potassium silicate. As it is soluble in water, it is called water glass.
# ordinary glass or soda lime glass or soft glass
- A glass obtained by heating a mixture of 50% silica, 15% sodium carbonate, 10% calcium carbonate and 25% glass pieces is known as ordinary glass or soda lime glass or soft glass. It is used im making ordinary glass vessel, window pans, etc. It has the composition of Na2SiO3.CaSiO3. It is insoluble in water. It is also called soft glass because it is easily soften on heating.
- Some other types of glass are hard glass, borosilicate glass (Pyrex glass), lead crystal glass, quartz glass, coloured glass etc.
# Hard Glass or Potash Lime Glass:
# Lead Crystal Glass or Potash Lead Glass:
# Borosilicate Glass or Pyrex Glass:
- Glass is called super cooled liquid because of its flowing property. It is found that in old buildings the pane of glass of window is thicker at lower surface than upper surface due to this property.
- Ceramics are objects made from clay, feldspar and silicates.
- Clay used in making ceramics is chemically hydrated aluminum silicate ( )
# Manufacture of ceramics
- For the manufacture of ceramics a mixture of China clay, lime stone, are crushed and grind to powder. The powder is then mixed with water to form paste known as slipwhich after moulding changes into articles of definite shapes. They are then dried to form porous articles. Porous articles after glazing becomes ceramics of our desire.
- Glazing: Some articles made by ceramics are coated with tin oxide or lead oxide are heated again. The coating of tin oxide or lead oxide melts and forms a thin layer over the surface. This process is glazing. Glazing makes the surface of articles smooth, attractive and waterproof.
# Properties of ceramics
- They can withstand high temperature.
- They are poor conductor of heat and electricity.
- They are attractive, hard and brittle.
- They are not affected by acids and bases or other chemicals.
# Uses of ceramics
- They are used in making crockery
- They are used as insulators in TV sets.
- They are used in making artificial tooth & bone joints.
- They are used in making bathroom tiles, sinks, etc
- Water proof ceramics or porcelain is used in laboratory.
- A fibre is hair-like strand which is strong and flexible. Generally, it is used in making ropes, clothes,nets etc.
# Natural fibre
- Natural fibres are obtained from naturally occurring sources e.g. cotton, wool, silk, etc.
- Merits of natural fibres are
- The cotton fabrics are light, soft and comfortable for summer as it has high absorbing capacity of sweat.
- They have property of retaining our body heat.
- Demerits of natural fibre are
- They are not so durable and eaten by insects.
- Silk fiberes are expensive where as cotton and wool doesn’t retain their creases.
# Artificial fibre
- Man made fibre is called artificial fibres. They are of two types:
- Recycled or Regenerated fibres
- Synthetic fibres
- Rayon is an artificial silk made from cellulose of cotton and wood pulp. It is recycled fibre. Rayon is used in making fabrics, tyres cords, carpets, etc
- Fibres made by chemical process are called synthetic fibres. Nylon, terylene, polyester, accryline, olefin, etc are its examples.
- Nylon is the first synthetic fiber because it is manufacture by polymerization of adipic acid(CH2)4(COOH)2 and hexamethyne-diamideH2N(CH2)6NH2.
- Nylon fiber is widely used as
- In making socks, ropes, tyre cords, bristles for tooth brush, nets etc.
- In making fabrics in textiles.
- The common properties of synthetic fibers are
- They are fine, light, strong, durable and not eaten by insects.
- They absorb less water and therefore dry up quickly.
Plastics are the artificial substances created through the polymerization process of monomers containing carbon.
- Hazards of plastics are
- It is non bio degradable substance
- It causes air pollution when burn in air.
- Plastic is very popular because
- It is light and cheap
- It can be recycled
- It can be cleaned easily and rusting doesn’t occur in it.
- It can be made in attractive colour.
# Soap and Detergents
- Soap is cleansing agent. It is prepared by using fat or oil and sodium hydroxide. Soaps are the sodium salt of higher fatty acids. For example sodium stearate, sodium oleate, etc.
- Detergents are also cleansing agent prepared from hydrocarbons obtained from petroleum.Detergents are the sodium salt of long chain benzene sulphonic acid which are mostly non-biodegrable with more cleansing property than soap. For example sodium lauryl Sulphate, alkyl benzene sulphonate and sodium pyrophosphate.
- Insecticides are poisonous chemical used for the control of insects.
- Insecticides are of two types:
- Organic Insecticides
- Inorganic Insecticides
- Organic insecticides are made up of carbon, hydrogen and oxygen and are of three major types called organophosphorous, Organochloride and Organocarbamate.
- DDT (dichloro diphenyl trichloroethane), BHC (Benzene hexachloride) Aldrin, Dieldrin, etc. are some examples of Organochlorine insectrcides.
- Baygon and Turmic are examples of carbamate insecticides.
- Calcium arsenate, lead arsenate, lime sulphur etc, are some examples of inorganic insecticides.
- Advantages of insecticides are:
- They can kill or destroy insects.
- They help to increase the production of crops.
- They are easy to use.
- Disadvantages of insecticides are-
- They destroy ecosystem of nature.
- They can pollute the soil and water of lake, ponds, streams etc.
- Long time expose to DDT causes cancer to human beings.
- Insecticides deposited on food crops causes adverse effect on the users.
- Precautions to be taken while usinginsecticides are as follows:
- They should be kept away from the reach of children.
- Mouth, nose and eyes should be covered during the use of insecticides.
- Instructions given on the container of the insecticides should be strictly followed.
- Hands should be washed properly after spraying or dusting insecticides.
- Fertilizers are the substances which can provide nutrients to increase the fertility of the soil.
- There are two types of fertilizers.
- Organic fertilizers (manures
- Inorganic fertilizer (chemical fertilizers).
- Compost manure is a natural fertilizer prepared by decaying cattle dung and organic residue (like leaves, grasses etc)
- Chemical fertilizers are artificially prepared inorganic chemical compounds used to provide essential nutrients to increase the fertility of soil.
- Ammonium Sulphate [(NH , ammonium nitrate ( urea [CO(NH2)2] calcium cyanamide [Ca(CN)2] etc. are some examples of nitrogenous fertilizers. Nitrogen helps in the growth of glucose, etc.
- Ammonium phosphate [(NH4)3PO4], calcium super phosphate [Ca(H2PO4)2 2CaSO4], triple super phosphate 3Ca(H2PO4)2 etc, are some examples of phosphorous fertilizer. Phosphorous helps in the proper growth of root, formation of glucose, etc.
- Potassium chloride (KCI), potassium nitrate (KNO3), potassium Sulphate protects from diseases from diseases and makes the stem stout.
- NPK means nitrogen, phosphorus and potassium elements found in nitrogenous, phosphorous and potassium fertilizer.
# Chemical pollution
- The pollution caused by improper use of chemical substances is known as chemical pollution.
- Some causes of chemical pollution are:
- Insecticides and chemical fertilizers
- Refuses, waste materials and plastics.
- Smoke from the means of support and industries.
- Colour used in foodstuffs.
- Synthetic clingers.
- Solution to pollution are:
- Noxious smokes from industries should not be allowed to spread in air.
- Dirts must be properly disposed.
- We must emphasize in recycling and reusing of dirts as fertilizers.
- Gypsum salt is also added in the manufacture of cement.
Ans- Gypsum is used in cement to increase and regulate the setting of cement. It makes convenient to use the cement.
Gypsum is added to cement to slow down the initial setting of cement when water is added. As a result it leads to greater hardening and makes convenient to our work.
- Cement is filled in airtight bags.
Ans- Cement is filled in airtight bags to avoid moisture.
- Sodalime glass or ordinary glass or soda glass is also called soft glass.
Ans- Soda glass is also called soft glass because it is easily soften on heating.
- Lead crystal glass is used for making expensive glassware.
Ans- The lead crystal glass shows an extraordinary sparkle as it has high refractive index. So it is used for making expensive glassware (like decoration pieces)
- Potash glass is also called as hard glass.
Ans- Potash glass is also called as hard glass because it has a higher melting point and can with stand higher temperature and also of more resistant to the action of acids.
- Use of plastics is disadvantageous also.
Environmentalists request to request to avoid the use of plastic.
Ans- Use of plastics is disadvantageous also because they are not degradable chemicals and do not decay. Their burning also produces harmful smoke that may cause many diseases.
- Plastic materials are used more than other meterials.
Ans- because of the following reasons.
- It is cheap and durable.
- It does not rot and corrode.
- It is a bad conductor of heat and electricity.
- It is lighter and can be changed into any desirable shape.
- PVC is not used to cover the handle of pressure cooker but Bakelite is used.
Ans- PVC is a thermoplastic which softens and melts on heating whereas Bakelite is a thermosetting plastic which does not soften and melt on heating. So, PVC is not used to cover the handle of pressure cooker but Bakelite is used.
- The thermosetting plastic is used to cover the handle of pressure cooker.
Ans- Thermosetting plastic (e.g.Bakelite) is heatresistant and non-conducting material. It does not change its shape on heating. It hardens more on heating instead of melting. So thermosetting is used to cover the handle of pressure cooker.
10. Rayon is called artificial silk.
Ans- Rayon is called artificial silk because it resembles natural silk in appearance but it is man-made gibrt.
11. Glazing is done during the manufacture of ceramics.
Ans-Glazing is done during the manufacture of ceramics to make the surface of the ceramics smooth, attractive and waterproof.
12. Ceramic materials are brought into use.
Ans- because of the following reasons:
– It is poor conductor of heat and electricity.
– It is resistant to the action of chemicals.
– It is hard and brittle.
13. Detergents are suitable for washing clothes with hard water.
Ans- Detergents are suitable for washing clothes with hard water because they do not form insoluble scum with hard water.
14. Soap is not suitable for washing clothes with hard water.
Ans- because of the following reasons:
– A large amount of soap is wasted in reacting with the Ca and Mg ions of hard water to form an insoluble precipitate i.e.scum.
– The scum formed by the action of hard water on soap, sticks to the clothes being washed and interferes with the cleaning ability of the additional soap which makes the cleansing of clothes difficult.
15. Detergents are also called soapless soaps.
Ans- Detergents are also called soapless soaps because they have cleansing property in water like soap but their chemical nature is different from soaps..
16. Detergents are cheaper than soaps.
Ans- Detergents are cheaper than soaps because they are prepared from the hydrocarbons extracted from petroleum instead of vegetable oils and fats.
17. Synthetic detergents are better than soaps.
Ans- Synthetic detergents are better than soaps because of the following reasons:
– They can be used even with hard water but soaps are not suitable.
– They have a stronger cleansing action than that of soaps.
18. Detergents are more efficient in comparison to soaps.
Ans- because of the following reasons:
– These are used even in hard water.
– Their Ca and Mg salts are soluble in water.
19. Sodium chloride is added during the preparation of soap.
Ans- Sodium chloride is added during the preparation of soap in order to precipitate out all the soap from its aqueous solution.
Sodium chloride decreases the solubility of soap due to common ion effect.
20. Use of chemical fertilizers is not advantageous only.
Ans- Use of chemical fertilizers is not advantageous only because they imbalance pond ecosystem, pollute the soil and water.
21. It is essential to use chemical fertilizers with organic fertilizers.
Ans- It is essential to use chemical fertilizers with organic fertilizers because organic fertilizers have nutrients in very less amount which are not sufficient.
22. Use of pesticides is not advantageous only.
Ans- Use of pesticides is not advantageous only because it causes different type of diseases in human beings, kills also useful insects and pollutes the environment.
23. The complete fertilizers are also called NPK fertilizers.
Ans- The complete fertilizers are also called NPK fertilizers because the fertilizers contain all the three nutrients i.e. nitrogen, phosphorus and potassium as primary plant nutrients.
10. Lead monoxide is added in glass.
Ans- Lead monoxide is added in glass to improve the transparency and refractive index of glass.
11. Boric Oxide is added in glass.
Ans- Boric oxide is added in glass to make the glass heat and chemicals resistant.