Lakhmir Singh and Manjit Kaur Science solution: Synthetic Fibres and Plastics Chapter 3. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 3 . Here we give Chapter 3 all solution of Class 8. Its help you to complete your homework.
Board – CBSE
Text Book – SCIENCE
Class – 8
Chapter – 3
VERY SHORT ANSWERS TYPE QUESTIONS Answer
1) Name the units of which cellulose polymer is made ?
Ans: Monomers.
2) Name the man-made fibre prepared from natural materials.
Ans: Cotton, Wool
3) Name the man-made fibre which is regarded as artificial silk ?
Ans: Rayon
4) Name the fibre obtained by the chemical treatment of wood pulp (or cellulose).
Ans: Rayon
5) Name the first fully synthetic fibre.
Ans. Nylon
6)Name the fibre used for making parachutes and rock climbing ropes.
Ans: Nylon.
7)which synthetic fibre contains the organic group similar to those which give fruits their sweet smell ?
8) Which synthetic fibre feels like wood and used as a substitute for wool ?
Ans: Polyester
9) To which kind of synthetic fibres does terylene belong ?
Ans: polyester.
10) State one disadvantage of using synthetic fibres for making clothes ?
Ans: Clothes made of synthetic fibres are not suitable for wearing during hot summer.
11) Name the form of polyester which is replacing materials like glasas and used for making bottles and jars .
Ans: PET
12) Name four different plastics.
Ans:
- Bakelite
- Polythene
- Melamine
- Teflon
13) Give one use of Teflon ?
Ans: Teflon is used for giving non-stick coating on cook wares.
14)Which of the two is a thermosetting plastic: PVC or Bakelite ?
Ans: Bakelite
15)fill in the following blanks with suitable words:
a> Synthetic fibres are also called MAN-MADE or ARTIFICIAL fibres.
b> synthetic fibres are made from raw materials called RAYON.
c> Like synthetic fibres, plastic is also a POLYMER.
d> The used of plastic can be reduced by using bags made of PAPER BAGS or STAINLESS STEEL BOX instead of polythene bags.
SHORT ANSWER TYPE QUESTIONS:
16) What is a polymer ? Name the natural polymer of which cotton is made ?
Ans: A polymer is a ‘ very big molecule’ formed by the combination of a large number of a small molecules.
Cotton fibre is made of a natural polymer called cellulose.
17) State the characteristics of synthetic fibres.
Ans. The characteristics of synthetic fibre are:-
1> they are more durable.
2> they are less expensive.
3> they are readily available and easy to maintain.
4> they dry up quickly and are wrinkle resistant
18) What is nylon ? State the important properties of nylon.
Ans. Nylon is a synthetic fibre.
The important properties of nylon is :
- Nylon fibres are very strong, fairly elastic.
- Nylon fibres absorb very little water.
- Nylon is wrinkle resistant.
19) Give the important uses of nylon ?
Ans:
- Nylon is used for making textiles like sarees, shirts, neck-ties, tights, socks, and other garments.
- Nylon is used in making curtains, sleeping bags and tents.
- Nylon is used in making ropes, car seat belts, fishing nets, tyre cord, strings for sports rackets and musical instruments.
20) What is polyester ? Name the popular polyester ?
Ans: Polyester is a type of synthetic fibre.
Name of the popular polyester is terylene.
21) Arrange the following fibres in the orders of increasing strength (keeping the fibre of least strength first)
Ans:
- Cotton
- Wool
- Silk
- Nylon
- Polyester
22) What is PET ? State the uses of PET ?
Ans: PET is a very popular form of polyester. PET stands for ‘Poly-Ethylene Terephthalate’,
Uses of PET :
- Making bottles.
- Making jars.
- Making utensils.
23) What is acrylic ? State one important property of acrylic ?
Ans: Acrylic is a synthetic fibre. Acrylic fibre is made from a chemical called ‘acrylonitrile’ by the process of polymerisation.
One important property of acrylic is its wool like feel, acrylic fibre is often used as a substitute for wool.
24) Write the uses of acrylic fibres.
Ans.
- Making sweaters
- Making shawls
- Making blankets
- Making jackets
- Making sportswear
- Making socks
25) Why should we not wear clothes made of synthetic fibres (like nylon or polyester) while working on the kitchen ?
Ans: If a person is wearing clothes made of synthetic fibres and his clothes catch fire accidently then the synthetic fibres of clothes melt and stick to body of that person causing severe burns. So that’s why we should not wear cloths made of synthetic fibres while working on the kitchen.
26) What type of shirts should we buy for summer ; cotton shirts or shirts made with synthetic materials ( like polyester) give reason for your answer ?
Ans: we should buy cotton shirts for summer.
The reason is clothes made of synthetic fibres do not sufficient pores for the sweat to come out, evaporate and cool our body. Due to this, clothes made of synthetic fibres make us feel hot and uncomfortable during summer.
27) Explaining how, manufacturing of synthetic fibres is actually helping in the conservation of forests.
Ans: Synthetic fibres doesn’t use natural substances as they use petrochemical but natural fibres uses natural substances. For example : Cotton, Jute.
Thus, manufacturing of synthetic fibres is actually helping in the conservation of forests.
28) What are plastics ? Name five commonly used articles made of plastics ?
Ans: A Plastic is a synthetic materials which can be moulded into desired shape when soft and hardened to produced a durable article .
Five commonly used articles made of plastics are :
- Water-bottles
- Mugs
- Water tanks
- Water pipes.
29) What are the various types of plastics ? Give two example of each type of Plastics ?
Ans: The various types of plastics are:
- Polythene
- Polyvinyl chloride
- Bakelite
- Melamine
Two example of each type of plastics are given below :
- Polythene – making polythene bags, bottles etc,
- Polyvinyl chloride – making electric wires, pipes, garden hoses etc.
30) Why are thermoplastics not used for making frying pan handles ?
Ans: Thermoplastics is a plastic which can be softened repeatedly by heating and can be moulded into different shapes that’s why thermoplastics are not used for making frying pan handles.
31) Explain why, frying pan handles are made of thermosetting plastics ?
Ans: Frying pan handles are made of thermosetting plastics because they don’t soften on getting heated and they are poor conductors of heat.
32) Why are electric switches, plugs and sockets made of thermosetting plastics ?
Ans: Thermosetting plastics are used for making those articles which may get too hot during use and are hard and rigid (so that they do not bend at all) so that’s why electric switches, plugs and sockets made of thermosetting plastics.
33) Explain the difference between thermoplastics and thermosetting plastics ?
Ans:
| Thermoplastic | Thermosetting |
| 1> This plastic can be softened repeatedly by heating and can be moulded into different shapes | 1> This plastic which once set, does not become soft on heating and cannot be moulded a second time. |
| 2> Examples are : polythene and polyvinyl chloride | 2> Examples Are : bekalite and melamine |
| 3> Uses are : making plastic bottles, jars, combs, raincoats etc. | 3> uses are: making electric switches, floor tiles, ballpoint pens etc. |
34) Should the bristle of a toothbrush be made of thermosetting plastics ?
Ans: No, the bristle of a toothbrush can not be made of thermosetting plastics.
35) Explaining why plastic containers are preferred for storing food ?
Ans: Plastic containers is strong and impact resistant and also plastic containers I is lightweight and shatterproof , so that’s why plastic containers are used for storing food.
36) choose the thermoplastics and thermosetting plastic from the following:
Ans:
- Thermoplastics : polythene and polyvinyl chloride
- Thermosetting plastics : melamine and Bekalite
37) State two uses of polythene ?
Ans: Two uses of polythene are:
- Making comb
- Making plastic bags
38) Write the full form of PVC ? Is it thermoplastic or thermosetting plastic ?
Ans: The full form of PVC is ‘ Polyvinyl chloride’
PVC is a thermoplastic.
39) Write two uses of Bakelite ?
Ans: Two uses of Bakelite is
- Making electric fittings such as electric switches,
- Making plugs and sockets.
40) State two uses of melamine ?
Ans: Two uses of melamine is :
- Making floor-tiles
- Making unbreakable kitchenware (cups, plates etc)
41) Give two uses of PVC ?
Ans.
- Insulation cover for electric wires.
- Making comb plastic bags etc.
42) Write some of the uses of plastic in healthcare industry.
Ans. Making bandages, syringe and some another surgical dressings.
43)Classify the following as biodegradable and non-biodegradable materials :
Ans:
- Biodegradable : Woolen clothes, paper, peels of vegetables and fruits, cotton clothes, jute bag,
- Non-biodegradable : Polythene bags, Aluminium cans, Toothbrush, Electric switch, Frying pan handle.
44) State whether plastic is biodegradable or non-biodegradable ? give reasons for your answer ?
Ans: Plastic is a Non-Biodegradable product.
The reasons are biodegradable products are decomposed through natural process but Non-Biodegradable products are not decomposed through natural process.
45) Explain how , the use of plastic has a a bad effect on the environment ?
Ans. The following points are
- The articles made of plastic are non-biodegradable, so they don’t decompose easily.
- The burning of plastic wastes gives out harmful gases which pollute the air.
46) Explain why , the disposal of plastic wastes is a major problems. Give two reasons only.
Ans: The disposal of plastic wastes is a major problems. This is because of the following two big disadvantages of plastics are:
- The articles which are made of plastics are non bio-degradable and also they don’t decompose easily.
- The burning of plastic wastes gives out harmful gases which pollute the Air.
47) What are the various ways to save the environment from excessive plastic wastes ?
Ans: Some steps to save the environment from excessive plastic wastes are as follows:
- We should try to reduce the use of plastics by using other materials in their place.
- We should not throw polythene bags, wrappers of chips, biscuits and other eatables in water bodies, on the roads, or picnic spots.
- We should reuse the plastic containers which comes with jams, pickels, oils and other packed food.
48) How do carelessly thrown plastic bags affect:
a> dirty water drains and sewers ?
b> animals (such as cows)
Ans:
a> if the plastic bags thrown carelessly into the dirty water drains then the plastic bags clog (block them) them. This makes the dirty drains water to flow over the streets and roads causing unhygienic conditions.
b> if the plastic bags thrown carelessly, the animals will eat up along with the left over food and vegetables and that plastic wastes choke the respiratory system or lining in their stomach.
49) What is meant by 3R’s ? Principle in the context of use of plastics ?
Ans: The three R’s stand for : Reduce, Reuse, Recycle.
50) State the various ways in which we can avoid the use of plastics ?
Ans: The various ways that we can avoid the use of plastics
- We should try to reduce the use of plastics by using other materials in their place.
- We should not throw polythene bags, wrappers of chips, biscuits and other eatables in water bodies, on the roads, or picnic spots.
- We should reuse the plastic containers which come with jams, pickels, oil and other pacekd food.
LONG ANSWER TYPE QUESTIONS :
51) Ans: Rayon is a man-made fibre prepared from a natural raw materials (called cellulose) by chemical treatment.
Rayon is made as follows :
- ‘Wood pulp’ is dissolved in an alkaline solution (sodium hydroxide solution) to form a sticky liquid called ‘viscose’.
- Viscose is forced to pass through the tiny holes of a metal cylinder into a solution of sulphuric acid when a silk like thread of rayon is formed.
b> Two uses of rayon are:
- Rayon is used in textile industry for making clothes like sarees, blouses, dresses etc.
- Rayon is used in medical field for making bandages and surgical dressings.
52) (a) The man-made fibres produced from chemical substances are called synthetic fibres. The name of two synthetic fibres are: Rayon, Nylon.
(b) Natural fibres are very costly and also weak textile quality but synthetic fibre are cheaper than natural fibres and also stronger quality than natural fibres. That’s why synthetic fibres are become so popular.
53) a> A plastic which can be softened repeatedly by heating and can be moulded into different shapes again and again is called thermoplastic.
Two example of thermoplastics are: polythene and polyvinyl chloride.
b> A plastic which once set, does not become soft on heating and cannot be moulded a second time, is called a thermosetting plastic.
Two example of thermosetting plastics are : Bekalite and melamine.
54) Thermopalstics can be softened by heat but thermosetting plastics cannot be softened by heat. It can be explained as follows : both the two plastics are made up of long chain molecules called polumers. In thermoplastics, the long polymer chains are not cross-linked with one another. This heating the individual polymer chains can slide and plastic becomes soft.
On the other hand, thermosetting plastics, the long polymer chains are cross linkeds with one another . these cross-links prevent the displacement of individual polymer chains on being heated. Due to this, thermosetting plastics do not become soft on heating .
55) Biodegradable : A material which gets decomposed through natural processes is called biodegradable.
Non-Biodegradable : A material which is not easily decomposed by natural processes is called non-biodegradable.
The two example of biodegradable materials are: Animal wastes and paper.
The two example of non-biodegradable materials are: Plastic and Aluminium cans.
Next Chapters Solution Link:
- Chapter 1) Crop Production And Management
- Chapter 2) Micro Organisms : Friend And Foe
- Chapter 4) Materials : Metals And Non-Metals
- Chapter 5) Coal And Petroleum
- Chapter 6) Combustion And Flame
- Chapter 7) Conservation Of Plants And Animals
- Chapter 8) Cell Structure And Functions
- Chapter 9) Reproduction In Animals
- Chapter 10) Reaching The Age Of Adolescence
- Chapter 11) Force And Pressure
- Chapter 12) Friction
- Chapter 13) Sound
- Chapter 14) Chemical Effects Of Electric Current
- Chapter 15) Some Natural Phenomena
- Chapter 16) Light
- Chapter 17) Stars And The Solar System
- Chapter 18) Pollution Of Air And Water
Sooo interesting !!!!!
It was so useful for our study and I want to say thank’s the coder or inventer of this website
Very useful for kids.
Nice
Thank you for this amazing website it’s help a student very well