NCERT Solutions for Class 8 Chapter 3 Synthetic Fibres and Plastics
NCERT Solutions for Class 8 Chapter 3 Synthetic Fibres and Plastics includes all NCERT Solutions for Class 8 in pdf, worksheet form.
The topics that we learn this lesson:
3. Synthetic Fibres and Plastics
3.1 What are Synthetic Fibres?
3.2 Types of Synthetic Fibres
3.3 Characteristics of Synthetic Fibres
3.4 Plastics
3.5 Plastics as Materials of Choice
3.6 Plastics and the Environment
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Board CBSE
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TextBook NCERT
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CLASS Class 8
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SUBJECT Science
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CHAPTER Chapter 3
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SUBJECT Synthetic Fibres and Plastics
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Category NCERT Solutions
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Keywords that we know now:
Acrylic: Acrylic is a synthetic fibre. Due to its wool-like feel, acrylic fibre is often used as a substitute for wool. Clothes made from acrylic are relatively cheaper but more durable than those made from natural wool It resists shrinkage and wrinkles.
Acrylic is used for making sweaters, shawls, blankets and carpets
Artificial Silk: A fibre was obtained by chemical treatment of wood pulp which was called rayon or artificial silk. It has properties similar to that of silk. It is man-made fibre. Since, rayon is made from naturally occurring polymer (cellulose) present in wood pulp, therefore it is neither a fully synthetic fibre nor a fully natural fibre. It is a semi synthetic fibre
It is chemically identical to cotton but it shines like silk.It absorbs sweat.
Nylon : Nylon is a synthetic fibre. It is the first fully synthetic fibre, made by man without using any natural material obtained from plants and animals). Nylon is a polyamide.
Nylon fibres are clastic, lustrous, strong and light. Nylon does not absorb water. Nylon is wrinkle resistant and is not attacked by fungus, moth etc
Nylon is used for making textiles (fabrics) like neck-ries, socks, shirts and other garments, used in making curtains, tents, sleeping bags, etc
Plastic : Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. The plasticity during production makes it possible for plastic to be moulded, extruded or pressed into solid objects of various shapes, making it an adaptable material for many different uses.
Polyester : Polyester is actually made up of the repeating units of a chemical called ester (fruity smell). Terylene is a popular polyester.
Polyester fibres are quite strong. Polyester fibres are wrinkle resistant and easy to wash and dry.
Polyester is used in making fabrics for sarees, dress materials and curtains (II) for making sails for sailboats, water hoses and conveyor belts.
NCERT Solutions for Class 8 Chapter 3 Synthetic Fibres and Plastics
Polymer : A polymer is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life.
Polythene : Polythene is a plastic obtained by the polymerisation of a chemical compound known as ethene, Polythene is tough and durable. Polythene is used in making polythene bags (plastic bags), waterproof plastic sheets, bottles, buckets and dustbins. Polythene is a strong and hard plastic.
Rayon : A fibre was obtained by chemical treatment of wood pulp which was called rayon or artificial silk. It has properties similar to that of silk. It is man-made fibre. Since, rayon is made from naturally occurring polymer (cellulose) present in wood pulp, therefore it is neither a fully synthetic fibre nor a fully natural fibre. It is a semi synthetic fibre
It is chemically identical to cotton but it shines like silk.It absorbs sweat.
In the textile industry for making fabric, to make furnishings such as bed sheets, curtains, blankets, etc.
Synthetic Fibres : The man-made fibres produced from chemical substances are called synthetic fibres. Synthetic fibres are made in industry by the chemical process called polymerisation. A synthetic fibre is a polymer made from the molecules of a monomer. Synthetic fibres are also known as man-made fibres or artificial fibres.
Types of Synthetic Fibres
(1) Rayon
(2) Nylon,
(3) Polyester,
(4) Acrylic.
Terylene : Terylene is a synthetic polyester fibre produced by polymerizing ethylene glycol and terephthalic acid which is obtained from petroleum.
Thermoplastics : The plastics which get deformed easily on heating and can be bent easily are known as thermoplastics. Examples are polythene and Polyvinyl Chloride (PVC). These plastics can be moulded into different shapes again and again. Thermoplastics are used for making insulation of electric wires and cables, various types of plastic containers (bottles, jars, etc.), comb, toys, raincoat packaging materials etc
Thermosetting Plastics : Thermosetting Plastics The plastics which when moulded once cannot be softened by heating are known as thermosetting plastics. Examples: bakelite and melamine. An article made up of thermosetting plastic will retain its original shape permanently, even on heating Thermosetting plastics are used for making handles of cooking utensil plates, cups, electric witches, plugs, rockets, telephone instruments, etc.
NCERT Solutions Synthetic Fibres and Plastics :
Exercises :
Question 1:
Explain why some fibres are called synthetic.
Answer 1:
Some fibres are called synthetic because they do not occur in nature.They are obtained by chemical processing of petrochemicals, e.g. nylon, polyester, acrylic, etc.
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Question 2:
Mark (√) the correct answer:
Rayon is different from synthetic fibres because
(a) it has a silk like appearance
(b) it is obtained from wood pulp
(c) its fibres can also be woven like those of natural fibres
Answer 2:
(b) it is obtained from wood pulp
Question 3:
Fill in the blanks with appropriate words:
(a) Synthetic fibres are also called ______ or _______ fibres.
(b) Synthetic fibres are synthesised from raw material called ________.
(c) Like synthetic fibres, plastic is also a __________ .
Answer 3:
(a) Synthetic fibres are also called man-made or artificial fibres.
(b) Synthetic fibres are synthesised from raw material called petrochemicals.
(c) Like synthetic fibres, plastic is also a polymer.
Question 4:
Give examples which indicate that nylon fibres are very strong.
Answer 4:
Nylon fibres are very strong. Nylon is used in making ropes, car seat bells, fishing nets, tyre cord, strings for sports rackets and musical instruments, bristles for toothbrushes and paint brushes. Nylon is used for making parachutes and ropes for rock climbing. All these uses of nylon are due to the high strength of nylon fibres A nylon thread is actually stronger than a steel wire of similar thickness.
Question 5:
Explain why plastic containers are favoured for storing food.
Answer 5:
Ans. plastic containers are favoured for storing food because of following reason :
(i) Plastics do not react with food items.
(ii) Plastics are strong, light and durable.
(iii) Plastic containers are airtight.
(iv) They are easy to handle.
Question 6:
Explain the difference between the thermoplastic and thermosetting plastics.
Answer 6:
Difference between the thermoplastic and thermosetting plastics:
Question 7:
Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards
Answer 7:
a) The handles of the saucepan are made up of thermosetting plastics because it is a poor (bad) conductor of heat and thus, we can hold the hot saucepan safely without getting our hands burnt. Generally we use melamine to make Saucepan handles which are thermosetting plastic.
(b) Electric plugs/switches/plug boards are made up of thermosetting plastics because it is a bad conductor of electricity and thus, protects us from electric current passing through them. Generally we use bakelite to make Electric plugs/switches/plug boards which are thermosetting plastic.
NCERT Solutions for Class 8 Chapter 3 Synthetic Fibres and Plastics
Question 8:
Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’:
Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs and electrical switches.
Answer 8:
Question 9:
Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.
Answer 9:
Synthetic fibres are extremely fine, so the clothes made of synthetic fibres do not have 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.
Clothes made of natural fibres (like cotton) are more comfortable during summer. This is because the large pores of cotton clothes allow the body sweat to come out through them, evaporate and make us feel cool and comfortable.
So, Rana is advised to buy a cotton shirt for summers and not the shirts made from synthetic materials (like polyester).
Question 10:
Give examples to show that plastics are non-corrosive in nature.
Answer 10:
Ans. Examples are given below shows that plastics are non-corrosive in nature
(i) They do not react with any substance. That is why we can store various kinds of chemicals and other materials in plastic containers.
(ii) Plastics do not react with air and water, so it will not show corrosion.
Question 11:
Should the handle and bristles of a toothbrush be made of the same material? Explain your answer.
Answer 11:
The handle and bristles of a toothbrush cannot be made of the same plastile because the handle of a toothbrush has to be hard and rigid whereas the bristles of a toothbrush have to be out and flexible. This means that the handle of a toothbrush should be made of a thermosetting plastic whereas its bristles should be made of a thermoplastic.
Question 12:
‘Avoid plastics as far as possible’. Comment on this advice.
Answer 12:
Now a days, plastics become very important in our daily life, even though we should avoid them as far as possible as for the following reasons:
(i) They are non biodegradable and take several years to decompose.
(ii) It adds to the pollution in the environment.The plastic left in the soil results in soil pollution.
(iii) By burning plastics, poisonous gases are released that cause air pollution.
(iv) The burning process in the synthetic material is quite slow and it does not get completely burnt easily.
(v) Polybags choke the drains and sewage pipes thus causing a lot of trouble.
Question 13:
Match the terms of column I correctly with the phrases given in column II.
Answer 13:
Question 14:
‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment.
Answer 14:
The manufacturing of synthetic fibres (like nylon, polyester and acrylic, etc.) is helping in the conservation of forests. This is because the synthetic fibre is manufactured from petrochemicals (obtained from crude oil petroleum), so no trees have to be cut down for making them. On the other hand, semi-synthetic fibres like rayon are made from wood pulp which requires cutting down of forest trees.
Question 15:
Describe an activity to show that thermoplastic is a poor conductor of electricity.
Answer 15:
Take two wires. One wire is kept naked and another wire has plastic covering. Then we make two circuits, one with naked wire and another with plastic covering. Now when we touch the naked wire, we get shock while plastic covered wire will not give any shock.
It shows that thermoplastic is a poor conductor of electricity.
NCERT Solutions for Class 8 Chapter 3 Synthetic Fibres and Plastics
