CBSE Class 8 Science Synthetic Fibres And Plastics Notes

CBSE Class 8 Science Synthetic Fibres and Plastics Chapter Notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

SYNTHETIC FIBRES & PLASTICS

INTRODUCTION

The clothes which we wear are made up of fabrics. Fabrics are made from fibres.A fibre is a thread or filament like material which is so strong & flexible that can be converted in to clothes, ropes and nets etc.
They are of two kinds :- (1) Natural fibres (2) Synthetic fibres

(1) Natural fibres : - These are long thin threads which are obtained from natural polymers obtained from animals or plants eg.

(i) Cotton & Jute – From cell wall of plant cells (Cellulose, is natural polymer)
(ii) Wool – From the fleece of sheeps & goats
(iii) Linen – From stalk of a plant (Flax)
(iv) Silk – From cocoons of silk worm.

(2) Synthetic fibres :-Those fibres which are synthetically man made, and are polymer of small units are called synthetic fibre.

• The word polymer is made up of two Greek words poly which means many and mer means unit.
• All the synthetic fibres are prepared from raw materials of petroleum origin called petrochemical. eg. Nylon, Polyester etc.

POLYMERISATION

Synthetic fibres are polymers. A polymer is a large molcule formed by the combining of many small molecules, each of which is called a monomer. The process of combining the monomers to form a polymer is called polymerisation. Polymerisation can be of various kinds, for example : addition polymerisation and condensation polymerisation.

Types of Synthetic fibres

1. Rayon 2. Nylon 3. Polyester 4. Acrylic 5. Spandex

1. RAYON

It was prepared by chemical treatment (viscose process) of wood pulp (cellulose). It is also called artificial silk because it resembles in appearance like natural silk.

Process :

Properties :
(i) Rayon can absorb sweat because of its tendency to absorb moisture. So it is preferred over other synthetic fabrics in summer season.
(ii) It is shiny and lustrous and resembles to silk.
(iii) It can be dyed in a wide variety of colours.

Uses :
(i) Rayon is mixed with cotton to make bed sheets and mixed with wool to make carpets.

(ii) Shirts, ties and linings are made up of rayon fibre.
(iii) It is used to manufacture tyre cords
(iv) It is used to make bandages and surgical dressings.

2. NYLON

• Nylon was first introduced in 1930s.
• It was developed in Newyork (Ny) & London (Lon) so it was named as Nylon.
• It was the first man made fully synthetic fibre.
• It is a polymer made from two monomers, a diacid and a diamine, by the process called condensation polymerisation.
• There are various nylons such as nylon 6, nylon 6-6 and nylon 5-10.

Properties :
(i) Nylon has high strength and high elasticity. It does not lose strength even after repeated use.
(ii) It is lustrous and easy to wash.
(iii) It absorbs very little water hence known to have drip-dry property.
(iv) It is wrinkle resistant and keeps permanent creases.
(v) It is moth and mould resistant.
(vi) It is light, fine and durable.

Uses :
(i) In making socks, sarees, shirts and other garments.

(ii) It is used to blend with wool to increase the strength & used in making carpets.
(iii) Used to make tents, parachutes, umbrella, fishing nets, climbing ropes, tyre cord, strings for sports goods.
(iv) It's fibres are used for making tooth brush, car seat belt, slipping bags and curtains.
(v) It is used to make machine parts.

MAKING NYLON 6-6 : Nylon 6-6 is a commerically successful variety of nylon made from adipic acid and hexamethylene diamine. First 6 in 'nylon 6-6' refers to the 6 carbons of adipic acid and the second 6 to the 6 carbons of the diamine.

Adipic acid + hexamethylene diamine → nylon 6-6 + water

The reaction is carried out at high temperature and pressure. The molten nylon 6-6 is then forced through a spinneret, with very fine holes into air where it hardens into filaments. The fibres are then stretched upon cooling.

Q. Explain why some fibres are called synthetic?
Q. Why Rayon is different from synthetic fibre?
Q. Give examples which indicate that Nylon is very strong?

3. POLYESTER

It is made of repeating units of a chemical called "ester" which has fruit like smell. Most polyester fabrics have excellent wash and wear characteristics and therefore requires minimum care eg. Terylene and Dacron.

Blended fibres :
Fabrics are sold by names like polycot, polywool, terrycot, etc. As the name suggests, these are made by mixing two types of fibres.
Polycot → Polyester + Cotton.
Terrycot → Terrylene + Cotton.
Polywool → Polyester + Wool

Properties :
(i) It absorbs very little water so dry quickly.
(ii) It is strong, light weight, wrinkle resistant and elastic fibre.
(iii) It is not attacked by moths and ordinary chemicals.
(iv) It can be drawn in to very fine fibres that can be woven like any other yarn.

Uses :
(i) Polyester fibres are used in manufacture of textiles.
(ii) Terry wool, a blend of terylene and wool, is used for making suits,Terrycot is used for making skirts, shirts and other dress materials.
(iii) It is used to make light weight sails, conveyor belts.
(iv) Polyester films, which is known as "mylar" are used for making magnetic recording tapes in audio cassettes, video cassettes and floppy discs.

Making Polyester : PET (polyethylene terephthalate), the commonly used polyester, is made from two monomers.terephthalic acid and ethylene glycol, by the process called condensation polymerisation terephthalic acid + ethylene glycol → polyethylene terephthalate (PET) + water.

4. ACRYLIC

Synthetic fibre prepared from acrylonitrile (Monomer unit). Acrylic fibre is also known as polyacrylonitrile ("PAN") or "Orlon" or Acrilan"

Properties :
(i) It is warm, soft, light and flexible fibre.
(ii) It closely resembles to wool in its properties & cheaper than natural wool.
(iii) Acrylic yarn can be easily knitted.
(iv) They are available in variety of colours.

Uses :
(i) Acrylic fibre is used for making sweaters, socks & shawls.
(ii) It is used for making carpets and blankets.

5. SPANDEX

Spandex is known for its high elasticity which makes it suitable for use in clothes, that require snug fitting eg swimming costumes. It is also known as "LYCRA" .When spandex is blended with cotton fabrics, stretched fabric is obtained which is used for making T-shirts and caps.

Uses : It is used in the making of costumes, caps, T-shirts etc.

PLASTICS

Material that can be shaped by applying heat and pressure. Plastic means easy to mould. Plastic is a polymeric substance that can be moulded when soft and then hardened to produce a durable article. It is made soft by applying heat and pressure before moulding.

Types of Plastics :- On the basis of their reaction to heat, all types of plastic can be classified into two groups.
(i) Thermoplastics
(ii) Thermosetting plastics

(i) Thermoplastics :- Those plastics which can be melted by heating and moulded into desired shapes and sizes, repeatedly are called thermoplastics. On heating these softens and on cooling they becomes hard. This cyclic process of heating, moulding & cooling is adopted to get desired shaped article. e.g Polythene, PVC, Nylon, Terylene and Polystyrene etc.

(ii) Thermosetting Plastics :- These are harder and stronger than thermoplastics and can retain their shape and size even at high temperature. These polymers once set in a given shape on heating, can not be resoftened or remelted on being reheated. eg. Bakelite, Melamine.

General Properties :-
(i) Plastic can be recyled, reused, coloured, melted, rolled into sheets or made into wires.
(ii) Plastic is non-reactive with moisture & air and insoluble in water. It is not corroded easily.
(iii) Plastic is light in weight, strong & durable and moulded into different shapes and sizes.
(iv) Plastics are poor conductor of heat and electricity, that's why electrical wire coverings, handles of screw drivers and frying pans are made of plastics.

Uses :

Q. Why plastic containers are favoured for stroring food?
Q. Explain the difference between theromoplastics and thermosetting plastics.
Q. Explain why the following are made of thermosetting plastics?
(i) Saucepan handles.
(ii) Electric plugs/ Switches/Plug boards
Q. Should the handle & bristles of a tooth brush be made of the same material? Explain your answer?
Q. Give example that plastics are noncorrosive in nature?

Plastic and Environment :

(i) Plastic takes several years to decompose so it is not environment friendly. It causes environmental pollution
(Air, Water & Land)
(ii) (a) When plastic burns, it releases lots of poisonous gases into atmosphere causing air pollution.
(b) When plastic wastes are dumped in water they cause water pollution.
(c) Accumulation of plastic waste on road sides & collection of ugly dumps causes many diseases to humans
and animals.

Q. Categorise the materials of the following products into "can be recycled" and "can not be recycled"Telephone instruments, plastic toys, cooker handles, carry bags, Ball point pens, Plastic bowls, Plastic covering on electrical wires, plastic chairs, electric switches.

Q. Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise rana, Giving your reason?

Problems and solutions associated with Plastic disposal :

Problems :

Environmental and health hazards problems arises with their disposal because they are nonbiodegradable.
Accumulation of plastics is a serious problem, because most of the method used to dispose them results in some type of pollution to the environment.
(i) Buried plastic materials prevent rain water from seeping into earth, so plant growth is affected in those areas.
(ii) Plastic waste may end up in littering road sides, floating in lakes and streams and collecting in ugly dumps.These provides homes for many diseases.
(iii) When wastes are dumped in water. It causes water pollution through toxic substances present in plastics. It can cause death or reproductive failure in fish and other aquatic animals.
(iv) When cows eats garbage they swallow materials like polythene bags and wrappers of food. It chokes the respiratory system of cows and forms a lining in their stomach and can be the cause of their death.
(v) The polybags thrown carelessly here and there are responsible for clogging the drains.

Solutions :

(i) Avoid the use of plastics as far as possible.
(ii) Use cotton or jute bags instead of plastic bags when we go for shopping.
(iii) Biodegradable and Nonbiodegradable waste should be collected separately and disposed off separately.
(iv) Recycle the plastic waste. Take care in collection, sorting and processing the plastic waste with this aim that it can be used in manufacturing of other products.
(v) Knowledge should be given to people about "green bin" and "blue bin" provided by municipality for separation of biodegradable waste such as food items (Green bin) and Nonbiodegradable waste such as plastics (Blue bin).
(vi) People should also be advised to follow 4R principles. The "4R" principles are –
(a) Reduce (b) Reuse (c) Recycle (d) Recover
It will make environment friendly.
To overcome the problem of disposal of solid polymer waste, scientists were trying to make such type of plastics which should be "biodegradable" (decomposed by microorganisms) and "Photodegradable"
(decomposed by sunlight) some polymers have been made. examples are –

(i) Poly β – Hydroxybutyrate – co – β – Hydroxy valerate (PHBV)
It is biodegradable and used in speciality packaging, orthopaedic devices and in controlled release of drugs.

(ii) Nylon – 2 – Nylon – 6 (Biodegradable)
To identify the plastics, numbers have allotted to different types of plastics. The principle used for it is, smaller the number, easier is to recycle. 

Q. Avoid plastics as far as possible, comment on this advice
Q. Manufacturing synthetic fibres is actually helping conservation of forests. Comment

ACTIVITY

To determine effect of flame on different kinds of fibres.

Materials required :

- 10 cm long fibre of (i) cotton, (ii) Rayon (iii) Wool, (iv) Silk, (v) nylon (vi) Polyester and (vii) acrylic
- A spirit lamp or a candle
- Fire-tongs
- A plate made of chine clay or glass.

Method
Light the spirit lamp or the candle and place it on the table. Next to it place a plat of chine clay or glass. Hold the cotton fibre in the fire-tongs and then hold it over the flame, till it catches fire. Shift the burning fibre over china clay plate and make observations till a small amount of it is left. Drop this small burning fibre in the china plate.
Repeat the activity with the fibres of other materials. Your observations wil be as listed under: 

SOME IMPORTANT POINTS FOR COMPETITIVE EXAMINATION

- Stones are readymade building material.
- Granite stones are very strong and long lasting.
- Most famous temples of South India are made of granite stones.
- Nagarjunsagar dam on river Krishna is made of granite stones.
- Red Fort at Delhi and palaces of Fatehpur Sikri (Agra) are made of sandstone.
- The famous Taj Mahal at Agra is made of white marble.
- Bricks were extensively used by the people of the Indus Valley Civilization.
- In 1824, British engineer Joseph Aspdin discovered Portland cement.
- Cement is manufactured from silica, alumina, limestone and iron oxide.
- Gypsum is mixed during manufacture of cement to slow the setting (hardening) process.
- Cinder concrete is used to build bridges.
- Glasses are super cooled liquids.
- Glasses are made from silica and silicates.
- Soda-lime silica glass is used to make bottle, crockery, mirrors, etc.
- Plate glass is used in shop windows and doors.
- Bullet proof glass is made by safety glass and is laminated with a thin layer of plastic (polyvinyl butyral).
- Lead crystal glass has high refractive index.
- Boro silicate glass is resistant to heat.
- Photochromic glasses contain silver iodide.
- Glass fibres are woven with cotton fibres to make water-proof and fire-proof sheets.
- Water proof sheet layers are joined together by adhesives to form fibre glass material.
- Optical fibres are very fine glass tubes.
- Optical fibres are used in endoscopy.
- Ceramic pottery is produced by treating clay at high temperatures.
- The simplest and oldest type of pottery is earthenware.
- Terra cotta is a primitive unglazed kind of pottery.
- Porcelain is made from white clay and is translucent.
- Porcelain was first made in China and is also known as Chinaware or Bone China.
- Porcelain is used as insulator for high tension electric cables.
- Plant cellulose is a natural polymer.
- Wool and silk are also natural polymers having long chains of protein molecules.
- Polythene is thermoplastic and is used for packing milk.
- Polystyrene is very light, when blown contains many air bubbles.
- Perspex is extermely light and transparent.
- Teflon is used as a nonstick coating for cooking utensils.
- Rayon has silky look and is similar to cotton.
- Soap has two-headed molecule, i.e., hydrophilic (have affinity with water) and hydrophobic (repel water molecule).
- Soaps do not produce lather in hard water.
- Detergents are made chemically from petroleum hydrocarbons.
- Household detergents are mostly alkaline in nature.
- Ammonia is main basic constituent of nitrogenous fertilizers.
- Weedicides are used to eliminate weeds.
- Use of DDT and BHC is banned in some countries.
- DDT and BHC are pesticides having long lasting effects.
- Some pesticides enter in food chains, thus cause serious health hazards.
- Glass is made by fusing sand (silica) with sodium carbonate and calcium carbonate.
- Many man-made substances are not biodegradables.
- Formica and Melamine are generally used for making cups and crockery.
- Thermosets do not soften upon heating.
- Bakelite is a common example of thermoset. 

SUMMATIVE ASSESSMENTS

Question. Which of the following is a natural fabric ?
(A) Polyethylene
(B) PVC
(C) Nylon
(D) Cotton
Answer : D

Question. ................. is an example of natural fibre.
(A) Nylon
(B) Rayon
(C) Jute
(D) Terylene
Answer : C

Question. Which is known as artificial silk ?
(A) Rayon
(B) Nylon
(C) Dacron
(D) Polyester
Answer : A

Question. The fibre obtained from cellulose is ..........
(A) Polyester
(B) Nylon
(C) Acrylic
(D) Rayon
Answer : D

Question. Which resembles in properties with wool ?
(A) Acrylic
(B) Orlon
(C) Acrilan
(D) All of these
Answer : D

Question. By which fabrics terrycot is made ?
(A) Polyester + Cotton
(B) Cotton + Orlon
(C) Cotton + Nylon
(D) Cotton + Rayon
Answer : A

Question. The raw material used in preparation of synthetic fibres is :
(A) Petrochemicals
(B) Petrol
(C) Gasoline
(D) Coaltar
Answer : A

Question. Which of the following do not contain polyester fabric ?
(A) Terrywool
(B) Terrycot
(C) Terylene
(D) Orlon
Answer : D

Question. South-Indian temples are made of :-
(A) Granite
(B) Sandstone
(C) Limestone
(D) Concrete
Answer : A

Question. Dams on rivers are mostly made by :-
(A) Sandstone
(B) Limestone
(C) Metamorphic rocks
(D) Granite
Answer : D

Question. Red Fort at Delhi and palace of Fatehpur Sikri are made of :-
(A) Granite
(B) Sandstone
(C) Limestone
(D) Concrete
Answer : B

Question. Who discovered cement?
(A) Agassiz
(B) Albertus Magnus
(C) Joseph Aspdin
(D) Janseen
Answer : C

Question. Which of the following is used to build bridges?
(A) Cinder concrete
(B) Sandstone
(C) Limestone
(D) None of these
Answer : A

Question. Which of the following is used to reinforce cement?
(A) Bricks
(B) Stones
(C) Steel rods or bars
(D) Mortar
Answer : C

Question. Photochromic glass contains :-
(A) Silver bromide
(B) Silver iodide
(C) Silver chloride
(D) All of these
Answer : B

Question. Which of the following is used in endoscopy?
(A) Optical fibres
(B) Glass fibres
(C) Glass wool
(D) None of these
Answer : A

Question. Purple-blue coloured glass is obtained by the addition of :-
(A) Chromium salts
(B) Ferrous oxide
(C) Cobalt salts
(D) None of these
Answer : C

Question. Terra cotta is :-
(A) Kaolin
(B) Clay
(C) Unglazed primitive pottery
(D) Porcelain
Answer : C

Question. Porcelain is made from :-
(A) Clay
(B) Kaolin
(C) Quartz
(D) White clay
Answer : D

Question. Which of the following is a natural polymer?
(A) Cellulose
(B) Nylon
(C) Polythene
(D) PVC
Answer : A

Question. Which of the following have long-chains of protein?
(A) Jute
(B) Cotton
(C) Silk and wool
(D) All of these
Answer : C

Question. Thermocole is made from
(A) Polythene
(B) Polystyrene
(C) Perspex
(D) Teflon
Answer : B

Question. Which of the following is thermoplastics?
(A) Polythene
(B) Bakelite
(C) Both of these
(D) None of these
Answer : A

Question. Contact lenses are made from :-
(A) Polyvinyl chloride
(B) Polystyrene
(C) Lucite
(D) Teflon
Answer : C

Question. Which of the following is used as non-stick coating for cooking utensils?
(A) Perspex
(B) Styrofoam
(C) Polystyrene
(D) Teflon
Answer : D

Question. Which of the following are thermosets?
(A) Formica and Melamine
(B) Polystyrene
(C) Polythene
(D) Thermocole
Answer : A

Question. Which of the following is similar to cotton?
(A) Nylon
(B) Dacron
(C) Rayon
(D) Terylene
Answer : C

Question. Which of the following do not soften upon heating?
(A) Lucite
(B) Bakelite
(C) Polystyrene
(D) Polythene
Answer : B

Question. Which of the following does not produce insoluble carbonates in hard water?
(A) Soap
(B) Detergent
(C) Both of these
(D) None of these
Answer : B

Question. Which of the following is alkaline in nature?
(A) Soap
(B) Detergent
(C) Both of these
(D) None of these
Answer : B

Question. Which of the following is the basic constituent of Nitrogenous fertilizers?
(A) Amide
(B) Ammonia
(C) Sulphuric acid
(D) Hydrochloric acid
Answer : B

Question. Heptachlor is :-
(A) Fungicide
(B) Weedicide
(C) Insecticide
(D) All of these
Answer : C

Question. Which of the following pesticide is banned in some contries?
(A) DDT
(B) Dieldrin
(C) Chlordane
(D) Parathion
Answer : A

Question. The correct order of increasing size of particles is :-
(A) Sand, silt, clay
(B) Clay, sand, silt
(C) Clay, silt, sand
(D) Sand, clay, silt
Answer : C

Question. Why one should not wear polyester clothes while working in kitchen ?
(A) It catches fire & sticks on the body
(B) Clothes are costly
(C) Moisture absorbing capacity is less
(D) They are uncomfortable
Answer : A

Question. Which of the following is a thermoplastic ?
(A) Bakelite
(B) Melamine
(C) Phenol
(D) P.V.C.
Answer : D

Question. Which is used in making of thermocoal ?
(A) Polypropylene
(B) Polyethylene
(C) Polystyrene
(D) High density polyethylene
Answer : C

Question. Which polymer is used in making automobile battery casing ?
(A) High density polyethylene
(B) Polyester
(C) PVC
(D) Poly propylene
Answer : D

Question. Which of the following plastic is a thermosetting plastic ?
(A) Polystyrene
(B) Polyethylene
(C) PVC
(D) Bakelite
Answer : D

Question. Which is used to make disposable cups?
(A) Low density polyethylene
(B) Polypropylene
(C) Polystyrene
(D) PVC
Answer : C

Question. Plastic products are identified by the use of some special numbers. These numbers represent for :-
(A) Electrical conductivity of plastic product
(B) Thermal resistance of plastic product
(C) Durability of plastic product
(D) Recycling of plastic product
Answer : D

Question. Why the waste created by plastics is not friendly with environment ?
(A) Plastics are non biodegradable
(B) Plastics are biodegradable
(C) On burning it causes pollution due to evolution of poisonous gases
(D) A & C both
Answer : D

Question. Disposal of plastic is a major problem becasue :-
(A) It is non biodegradable
(B) It is biodegradable
(C) It takes several years to decompose
(D) A & C both
Answer : D

Question. PET bottles and utensils are made from :-
(A) Polyester
(B) Nylon
(C) Teflon
(D) Orlon
Answer : A

SELECTION TYPE QUESTIONS

Question. Cotton, silk, linen and wool are .................. fibres.
Answer : Natural

Question. The fibre developed in Newyork & London, Simultaneously is ..................
Answer : Nylon 

Question. Rayon is mixed with .................. to make .................. and mixed with .................. to make ..................
Answer : Cotton, bed sheets, wool, carpets.

Question. The fibre used in parachute making and ropes for rope climbing is ..................
Answer : Nylon

Question. Melamine is a .................. plastic.
Answer : Thermosetting 

Question. Like synthetic fibres plastic is also a ..................
Answer : Polymer 

Question. A material which gets decomposed through natural processes is called ..................
Answer : Biodegradable 

Question. The name of the fire proof plastic is ..................
Answer : Melamine 

Question. A special plastic on which oil and water do not stick is ..................
Answer : Teflon 

Question. Plastic which gets deformed easily on heating and can be bent easily is ..................
Answer : Thermoplastic

Question. Plastics which when moulded once, can not be softened by heating is ..................
Answer : Thermosetting

Question Containers which are light weight, lower price, good strength and easy to handling is made up of ..................
Answer : Plastic 

Question. .................. material is responsible for the cause of animal death.
Answer : Plastic 

Question. Most of the thermoplastics can be ..................
Answer :  Recycled

MATCH THE FOLLOWING

1. Match the terms of column A correctly with the statement given in column B.
       Column–A          Column–B
(A) Polyester             (i) Prepared by using wood pulp
(B) Acrylic                (ii) Used for making parachutes and stockings
(C) Rayon                (iii) Used to make sweaters & shawls
(D) Nylon                 (iv) Fabrics do not wrinkle easily

Answer : 1. (A) → (iv) ; (B) → (iii) ; (C) → (i) ; (D) → (ii)

MATCH THE FOLLOWING

1.     Column–A            Column–B
(A) Polymer                (i) Poly tetra fluoroethylene
(B) Polyethene           (ii) Thermosetting plastic
(C) Bakelite               (iii) Thermoplastic
(D) Teflon                  (iv) Biodegradable
(E) Wollen cloth          (v) Small units combine to form large single units

Answer : 1. (A) → (v) ; (B) → (iii) ; (C) → (ii) ; (D) → (i) ; (E) → (iv)

Q6 Which property of Nylon enables it to be used:

A6. a) to make rope for rock climbing - Strong fibre, light in weight, weather resistant.

b) To make tents - Strong, light, does not absorb much water, dries quickly

c) Fishing nets - Strong, elastic, resist water

Q7. From which monomer is polyester prepared ? Name some types of polyester fibres.

A7. Polyester is prepared from the monomer called Ester. Terylene ,Terene and Dacron are some types of polyester fibres.

Q8. List some advantages of polyester over cotton?

A8 As polyester is synthetic fibre, it is -

a. Strong

b. Wrinkle resistant

c. Not attacked by Moth.

d. Does not absorb much water and dries up quickly.

Q9. What are blended fibres ? Give examples.

A9. Fibres formed by mixing natural & synthetic fibres. e.g. Polywool - polyester + wool, Terycot - Terylene + cotton

Q1O. Which form of polyester is used to make bottles, utensils, wires ?

A1O. P.E.T. (PolyEtheneTetraphthalate)

Q11. Explain why storage of Acrylic needs no special care unlike woollen clothes ?

A11. Acrylic is synthetic wool which is resistant to the action of moths and insects while woollen clothes need to be stored in naphthalene as they are attacked by insects.

Q12. Give reasons -

A12. a. Buckets are made of plastics these days - As plastics are light in weight ,strong do not rust

b. Bakelite plastic is used to make electrical switches.- As Bakelite is a poor conductor of heat and electricity.

c. Melamine is used to make crockery - As it is unbreakable, resist fire and tolerate heat better than other plastics.

d. Plastics are used in cars, aircrafts and space crafts - As they are light in weight, corrosion resistant, strong and durable.

e. Chemicals are stored in plastic bottles - As they are resistant to the action of chemicals, light , unbreakable and corrosion resistant.

Q13. Which special plastic is used -

A13. a. For making non-stick coating on cookwares - Teflon

b. To make insulation covering on wires - P.V.C.

c. To make poly bags - Polyethene

d. To make flame resistant uniforms - Melamine

Q14. Why is plastics a cause of environment pollution ?

A14. a. Non biodegradable nature

b. Burning of plastic releases toxic fumes which cause air pollution.

Q15. Suggest a few ways to minimize pollution due to plastics.

A15. a. Reduce use of plastics - use jute, cotton, paper bags.

b. Do not throw plastics on the road or in the water bodies.

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