RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Rajasthan Board RBSE Class 8 Science Chapter 3 Synthetic Fibres and Plastics

RBSE Solutions for Class 8 Science

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

RBSE Class 8 Science Synthetic Fibres and Plastics Intext Questions and Answers

Page No 27.

Question 1.
List the different types of fibres in following table –
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-1
Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-2

Page No 28.

Question 2.
What are polymers?
Answer:
A chain of small units called monomers joined together is called polymer.

RBSE Class 8 Science Synthetic Fibres and Plastics Text Book Questions and Answers

Choose the correct options:

Question 1.
The material used for making non – stick utensils of kitchen is …………..
(a) PVC
(b) Polyether
(c) Teflon
(d) Rayon
Answer:
(c) Teflon

Question 2.
Which of the following group is of synthetic fibres ?
(a) Nylon, terelene, rayon
(b) compound
(c) Acrylic, silk, wool
(d) PVC, polyether, Bakelite
Answer:
(a) Nylon, terelene, rayon

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 3.
The handles of utensils are made from.
(a) Polyether
(b) Nylon
(c) PVC
(d) Bakelite
Answer:
(d) Bakelite

Question 4.
Which is not the property of plastics ?
(a) Inert
(b) Durable
(c) Light weight
(d) Conduction of electricity
Answer:
(d) Conduction of electricity

Question 5.
Thermoplastics is …………..
(a) Bakelite
(b) Melamine
(c) Polyether
(d) None of the above
Answer:
(c) Polyether

Fill in the blanks:

  1. Synthetic fibres are also called _________ and fibres.
  2. Rayon is also called _________ .
  3. The polymerisation of acetonitryl gives _________ .
  4. Plastic is also a type of __________ .

Answer:

  1. Artificial fibre, man made fibre,
  2. Artificial silk,
  3. Anon,
  4. Synthetic Polymer

Match Column A with Column B

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-3
Answer:

  1. (b)
  2. (d)
  3. (a)
  4. (c)

Short Answer type Questions:

Question 1.
Why it is not advised to burn plastics and synthetic fibres ?
Answer:
On burning synthetic fibres, they catches fire easily and also stick to the body when come in contact with it. Moreover during the burning process of plastics and synthetic fibres various poisonous gases are also evolved which pollute the environment. Thus it is advised not to burn plastics and synthetic fibres.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 2.
What are thermoplastics ? Explain with example.
Answer:
The plastic which gets deformed easily on heating and can be bent easily are called thermoplastics. They can be bent to make different new items i.e., polythene, PVC, polyesterene, etc. various types of containers, water pipes, etc. are made of PVC.

Question 3.
Terecot is obtained by mixing two types of fibres ? Name these fibres.
Answer:
Terecot is a mixture of following Two fibres –

  1. Natural fibre and
  2. Synthetic fibre.

Question 4.
What are non-biodegradable substances?
Answer:
The substances which arc not easily decomposed by natural processes are called non – biodegradable substances. For example : tin, aluminium and other metal container, plastic bags, etc.

Question 5.
What is polymerization?
Answer:
Synthetic libre is a chain of small units joined together and each small unit is a chemical substance. Many such small units combine to form a large single unit called polymer. This process is polymerization. For example: polythene, polyester. PVC, cellulose, etc.

Long answer type Questions:

Question 1.
Write the uses of synthetic fibre in our daily life.
Answer:
Synthetic fibres are made by human beings through artificial methods i.e., rayon, nylon, etc. Uses of synthetic fibres in daily life are –

  1. Rayon is mixed with cotton to make bed- sheets or mixed with wool to make carpets.
  2. Nylon is used for making parachutes and ropes for climbing.
  3. Socks, ropes, brushes, tents, curtains, etc. are inade of nylon.
  4. Polyester is used for making clothes.
  5. Synthetic fibres are more shiny and soft.
  6. Synthetic fibres soak less water and dry up easily.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 2.
Explain the statement “Do not use plastics in daily life as far as possible.”
Answer:
Despite of being very useful, plastic is not environment friendly. It does not get completely burnt easily and is not easily decomposed by micro – organisms. Polybags carelessly thrown here and there are responsible for clogging the drains. For example: Sometime careless people throw the wrappers of chips, biscuits, other eatables on the road or ¡n parks or in picnic places.

In the process of eating the food waste animals swallow materials like polythene bags, wrappers of food, etc. These plastic material chokes the respiratory system of these animals or forms a lining in their stomachs and can be the cause of their death. To avoid these problems. avoid usc of plastic and use cotton carry bag or jute bags.

Question 3.
How synthetic fibre nylon is formed? Write it different properties.
Answer:
Nylon is prepared by mixing of Adipic Acid and Hexamethylene Diamine. It is completely a synthetic fibre. Nylon has following properties –

  1. Nylon fibre is strong elastic and light.
  2. It is lustrous and easy to wash.
  3. Clothes made from nylon does not get wrinkled and stable for long time.
  4. This is durable.
  5. They soak less water and dry up easily.
  6. Clothes of nylon does not have threat of clothes worn.
  7. They do not need extra care.

RBSE Class 8 Science Synthetic Fibres and Plastics Important Questions and Answers

Objective Questions:

Question 1.
The fibre obtained by polymerization of acetonitrile is ……………
(a) Dacron
(b) Anon
(c) Nylon
(d) Rayon
Answer:
(b) Anon

Question 2.
The component serving as hindrance in the water drainage system is ……………
(a) Agriculture
(b) Animals
(c) Plastic
(d) None of these
Answer:
(c) Plastic

Question 3.
The material used to make electric switches etc. is ……………
(a) PVC
(b) Polythene
(c) Bakelite
(d) Melamine
Answer:
(c) Bakelite

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 4.
The plastic used to make heat resistance materials …………..
(a) Bakelite
(b) Polythene
(c) Melamine
(d) All of the above
Answer:
(c) Melamine

Fill In the blanks:

  1. On heating thermoplastic, they becomes …………… (soft/hard)
  2. …………..is made by combining synthetic and natural fibers. (Nylone / Terrycot)
  3. The dresses of fire brigade man has a layer ………….. of plastic which is heat resistant. (B akelite/Mel amine)
  4. The substances that cannot decompose easily by natural processes are called ………….. (biodegradable/non biodegradable)
  5. Plastic is a type of ________ polymer. (synthetic/natural)

Answer:

  1. soft
  2. Terrycot
  3. Melainine
  4. non – biodegradable
  5. synthetic.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

State whether the followings statements are True or False:

  1. The components obtained by plastic are eco friendly.
  2. Polythene and PVC are thermosetting plastic.
  3. Maximum thermoplastics can be recycled.
  4. Tetìlon is used to make non-stick utensils.
  5. In plastic small organic molecules combine together to form higher molecular weight structures.
  6. The clothes made from synthetic fibres absorbs more sweat compare to the clothes made from natural fibres.

Answer:

  1. False
  2. False
  3. True
  4. True,
  5. True
  6. False.

Math the Column –

Question 1.
Match the following:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-4
Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-5

Question 2.
Match the following correctly:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-6
Answer:

  1. (iv)
  2. (iii)
  3. (ii)
  4. (i)

Very Short Questions:

Question 1.
Naine two articles made by nylon fibres that indicates the strength of nylon fibre?
Answer:

  1. Parachute
  2. The ropes used to climb rocks.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 2.
What is meant by polymers?
Answer:
The synthetic fibres made from small units which combines to form long chain are called polymers. Polymer is a Greek word in which ‘Poly’ means ‘many’ and ‘mer’ means ‘part’. Thus many units.

Question 3.
What is viscose?
Answer:
Viscose is an orange-brown solution Obtained by treating cellulose with sodium hydroxide and carbon disuiphide. It is used as the basis of manufacturing rayon fibre and transparent cellulose film.

Question 4.
How is nylon prepared?
Answer:
Nylone is made by mixing adipic acid and hexamethylene diamine.

Question 5.
Which synthetic fibre is used to prepare bedsheet or carpets?
Answer:
Rayon is mixed with cotton to make bedsheets and rayon is mixed with wool to make carpets.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 6.
How is anon obtained?
Answer:
Anon is obtained by the polymerization of acetonitriles. Its tibres are similar to wool.

Question 7.
How many types a plastics are there on the basis of structure? Write their names.
Answer:
On the basis of structures the plastics are of two types –

  1. Thermoplastic
  2. Thermosetting plastic.

Question 8.
Give two examples of thermosetting plastics.
Answer:

  1. Bakeifte
  2. Melamine.

Question 9.
What is meant by biodegrdabale substances?
Answer:
Those substances that can be decomposed into smaller, harmless substances by small micro – organisms are called biodegradable substanccs. e.g. compost, manure, etc.

Question 10.
How dacron is obtained?
Answer:
Dacron is obtaitied by the polymerization of ethylene glycol and terpthalic acid.

Question 11.
Write two uses of I3akelite.
Answer:

  1. It is used for making electrical switches.
  2. it is used for making handles of kitchen utensils.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 12.
Give two uses of rayon.
Answer:

  1. Its used as dress material.
  2. To make carpets, cushions, bedsheets, etc.

Question 13.
What are natural fibres?
Answer:
The fibres which are obtained from nature either plants or animals are called natural fibres. e.g. wool, cotton, etc.

Question 14.
Give two examples of natural fibres obtained from plants and animals.
Answer:

  1. Plant – Jute, Cotton.
  2. Animals – Wool, Silk.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Short Answer Type Questions:

Question 1.
Rajesh wish to purchase shirts for summer. Whether he should buy cotton shirts or synthetic ? Suggest RaJesh with reasons.
Answer:
Rajesh should buy cotton shirts for summer because –

  1. Cotton cloth is had conductor of heat so outer heat will not enter in our body, therefore this will protect our body from heat.
  2. Cotton cloth can absorb sweat excreted from our body so our body remains cool, but synthetic shirts do not absorb sweat and are not porous.

Question 2.
How is rayon prepared? Write its uses.
Answer:
Rayon is also known as artificial silk. This fibre is obtain by chemical treatment of naturally occurred higher polymer cellulose. First of all cellulose is purified then sodium hydroxide and carbon dsuiphide is mixed with it. Then it is converted into a viscous liquid.

This is known as ‘Viscose’. This viscose is passed through fine pores and treated with dilute sulphuric acide then rayon fibre is obtained. Rayon is just similar to natural silk. It is cheaper than natural silk. It can be woven easily. Rayon is mixed with cotton to make bedsheets or mixed with wool to make beautiful carpets.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 3.
Give any three main advantages of storing food items in plastic containers.
Answer:
The main advantages of storing food items in plastic containers are—

  1. They do not react with food, water and air.
  2. They are strong and light weighted.
  3. They are long durable.

Question 4.
Differentiate between thermoplastic and thermosetting plastics.
Answer:
Thermoplastic The plastic which gets deformed easily on heating and can bern easily is. known as thermoplastic. Examples – Polythene and polyvinyl chloride(PVC) Thermosetting PlasticThe plastic which getsmoulded once, cannot besoftened on heating is called thermosetting plastic. Examples – B akelite and melamine.

Question 5.
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 howls, plastic covering on electrical wires, plastic chairs, electrical switches.
Answer:

  1. Materials which can be recycled are plastic toys, carry bags. ball point pans, plastic howls, plastic covering on electric wires and plastic chairs.
  2. Materials which can not be recycled are telephone instruments, cooker handles, electrical switches.

Question 6.
What is 4R theory?
Ansnwer:
4R theory is given to develop the environment friendly habits in the man. This is as follows –

  1. R (Reduce) – Decrease the use of plastic
  2. R (Reuse) – Use again
  3. R (Recycle) – Recycle the plastic waste
  4. R (Recover) – Again obtain the plastic from waste.

Question 7.
“ManufacturIng of synthetic fibres is actually helping conservation of forests”. Comment.
Answer:
Natural fibres are obtained from natural sources but synthetic fibres are prepared by a number of processes using raw materials of petroleum origin called petrochemicals. So, it is clear that in production of synthetic fibres raw material from forests is no used. Therefore, they help in forests conservation and animals are also not hunted.

Question 8.
Explain with example, ‘Plastic is non reactive substance’.
Answer:
Plastic’s nature is non – reactive because it does not react with water or moisture. Examples –

  1. Water is kept in plastic bottles.
  2. Storing pickles and other food can be easily done in plastic containers.
  3. Many medicines and chemicals are stored in plastic made articles.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 9.
Mention types of plastics with two examples each.
Answer:
Plastic is of two types

  1. Thermoplastic
  2. Thermoseuing plastic

Examples of Thermoplastic

  1. Poly Vinyl Chloride (PVC)
  2. Polythene

Examples of Thermosetting Plastic

  1. Malamine
  2. Bakelite

Question 10.
Write the main characteristics of polyester fibres.
Answer:
Main characteristics of polyester fibres are

  1. Polyester fibres are very strong so the clothes made from polyester are durable for a long time.
  2. Polyester fibres soaks less water so the clothes of polyester dry early after washing.
  3. Polyester fibres have permanent crease
  4. There is no effect of insects and simple chemicals on polyester fibres.
  5. Polyester fibres are very light and thin.

Question 11.
Describe the characteristic properties of plastic.
Answer:
Characteristics properties of plastic are as follows –
1. Plastic is non – reactive
Plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material including many chemicals.

2. Plastic is light strong and durable
Plastic is very light, strong. durable and can he moulded into different shapes and sizes. Plastics are generally cheaper than metals So they are widely used in industry and for household articles.

3. Plastics are bad conductor of heat and electricity
Plastics are had conductor of heat and electricity. Thai is why electrical wires have plastic coverings and handles of frying pans are made of plastic.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 12.
Classify the followin substances in biodegradable and non-biodegradable nature, OH the basis of their degenerating property

  1. Peels of vegetable and fruits
  2. Pieces of glass
  3. Tin can
  4. Paper
  5. Plastic
  6. Wood

Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-7

Question 13.
Is plastic bad conductor of heat and electricity? Explain.
Answer:
Plastic is bad conductor of heat and electricity. That is Why electrical wires have plastic covering and handles of frying pans are made of plastic. The electrical wires having plastic covering show no current when touching them and the handles of frying pans become less hot after a long time.

Question 14.
What is meant by biodegradable and non – biodegradable.
Answer:
A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. A material which is not easily decomposed by natural processes is termed as non – biodegradable.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 15.
How plastic waste creates environ mental pollution? Explain.
Answer:
Since plastic takes several years to decompose so it causes environmental problem. The burning process of plastic materials is quite slow and this process releases lots of poisonous gases which cause environmental pollution.

Question 16.
What are the main points of libre wise?
Answer:
Main points of librewise are as follows

  1. Do not throw the plastic bags on road or in ponds after use.
  2. Make use of bags made of cotton or jute when you go lòr shopping.
  3. Use of plastic materials should he minimum and use utensils of steel in place of plastics.

Question 17.
What is thermosetting plastic? Explain. Write two uses of thermosetting plastic.
Answer:
Thermosetting plastic – Those plastic which become liarder on heating and do not melt are called thertnosetting plastics. Once they are moulded in any shape they cannot be moulded in other.
Uses :

  1. In making electric switches.
  2. In preparing bearings of vehicles.

Question 18.
Draw a diagram of a useful thing made by you from waste small pieces of clothes and waste woollen threads.
Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-8

Question 19.
Draw a decorating thing made by you from waste plastic bottles.
Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-9

Long Answer Type Questions:

Question 1.
Explain the main advantages and disadvantages of synthetic fibres.
Answer:
Advantages of synthetic fibres:

  1. The fabrics made of synthetic fibres dries faster than cotton fabrics because they are less water absorbent.
  2. Synthetic fibre is soft and shiny.
  3. The fabrics made from this are worm resi slant.
  4. The use of synthetic fibre is easy and less expensive.
  5. They can be easily handled and durable.

Disadvantages of synthetic fibres:

  1. The fabrics made of synthetic fibre catches fire easily and stick to the body on melting.
  2. The fabrics made of synthetic libre does not absorb sweat easily executed by our body at the cotton fabrics.
  3. They stick to the body in summer.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 2.
Write the important uses of plastic in different fields.
(OR)
Write any three uses of plastics.
Answer:
The uses of plastic in different fields are as follows –
1. In the field of health-care industry – Plastics find extensive use in the health-care industry. Some examples of their use are the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.

2. In the cooking of food – Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel. Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.

3. Fire – proof Plastics – Although synthetic fibre catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.

Question 3.
Write the main differences in natural fibres and synthetic fibres.
Answer:
Natural. fibres (Cotton, Wool and Silk)

  1. Natural fibres are less strong so the clothes formed by these fibres are less durable and torn out early.
  2. NaWral fibres soak more water so clothes of these take more time for drying after washing.
  3. Clothes of natural fibres are spoiled due to effect of insects and simple chemicals.

Synthetic Fibres (Nylon and Polyester)

  1. Synthetic fibres arc very strong so the clothes of these fibres are durable for a long time.
  2. Synthetic fibres soak less water so clothes formed by these take less ümc for drying after washing.
  3. There is no effect of insects and simple chemicals on clothes of synthetic fibres.

Question 4.
Give important properties and uses of nylon.
Answer:
Properties of Nylon:

  1. Nylon fibre is very light and strong.
  2. Fabric made from nylon does not get wrinkled and also are durable for long time.
  3. They soak less water and dry up quickly.

Use of Nylon:

  1. Nylon fibres are used for making fabric for parachute, net for fishes and clothes, etc.
  2. Nylon fibres are used for making toothbrushes, car seat belts, etc.
  3. Nylon fibres are more strong than steel wires, so, it is used for making ropes for rock climbing.

RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Question 5.
What is plastic? Highlight its uses.
Answer:
Plastic – Small carbon atoms combine to form high atomic number arrangements, these are called plastics. The use of plastics are –

  1. Electric wires are covered with layer of plastic to make electric resistant.
  2. Firemen uniforms have coating of melamine plastic to make them flame resistant.
  3. Teflon is used for non-stick coating on cook ares.
  4. Pipes used for irrigation are made of plastics.
  5. Special plastic cookware is used in microwave ovens for cooking food.
  6. Handles of food making utensils, cooker, etc. are made of plastics.
  7. Plastic containers are used to store things at home and shops.

Question 6.
Why the disposal of plastic is not easy, and what is harm of plastic to the environment?
Answer:
Now a days polythene and plastics are widely used. Synthetic plastic and polythene are non – biodegradable so become danger for ecosystem up to several years. These are decomposed in thousands of yeàrs so environment is polluted. The burning process of synthetic material is also quite slow so it takes long time and releases lots of poisonous gases in the atmosphere. Use of polythenc is a big problem in urban environment.

The poly bags carelessly thrown in rivers, ponds and open spaces after use are responsible for clogging the drains, too different types of bacteria are also developed due to this. The dirty water and waste are spread out on roads, streets and open spaces block the transport system. So the urban life becomes like hell. Hence use of plastic is very harmful for the environment.

Question 7.
Write the biodegradable and non – biodegradable substances ¡n the form of table.
Answer:
RBSE Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics img-10

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