Synthetic Fibres and Plastics Class 8 Important Questions and Answers

Important questions of Class 8 Science Chapter 3 Synthetic Fibres and Plastics is given below. These important questions will help students while preparing for the exam.  Practising these important questions will analyse their performance and work on their weak points. Score well in exam of Class 8 Science by going through these important questions. Students of Class 8 can download important questions of Class 8 Science Chapter 3 Synthetic Fibres and Plastics PDF by clicking the link provided below.

Important Questions of Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Synthetic Fibres and Plastics for Class 8 Science subject.

Very Short Answer Questions

1. What are clothes made up of?
Answer:
 The clothes we wear are made of fabrics.

2. What are fabrics made up of?
Answer:
 The fabrics are made of fibres.

3. How many types of sources of fibre are there?
Answer:
 There are two types of sources of fibres:
(i) Natural sources
(ii) Artificial sources.

4. What are natural fibres?
Answer: 
The fibres obtained from plants or animals are called natural fibres.

5. Give two examples of natural fibres.
Answer:
 (i) Cotton (ii) Jute.

6. What are synthetic fibres?
Answer: 
The fibres made by human beings are called synthetic or man-made fibres.

7. Name two man-made fibres.
Answer:
 (i) Nylon (ii) Rayon.

8. What are polymers?
Answer:
 When a large number of small units combine to form a single large unit, then the large unit is called polymer.

9. What is the word meaning of polymer?
Answer:
 Polymer consists of two words, poly and mer. Poly means many and mer means repeating units.

10. Name a natural polymer.
Answer:
 Cellulose.

11. What are the units of cellulose?
Answer:
 Cellulose is made up of a large number of glucose units.

12. Name the fibre having properties similar to that of silk.
Answer: 
Rayon.

13. What is the common name of rayon?
Answer:
 Rayon is known as artificial silk.

14. How is rayon obtained?
Answer:
 Rayon is obtained by chemical treatment of wood pulp.

15. Name a man-made fibre which is made without using natural raw materials.
Answer: 
Nylon.

16. When was nylon made?
Answer:
 Nylon was made in 1931.

17. What are the raw materials used in making nylon?
Answer: 
Nylon is prepared from coal, water and air.

18. Which is the first fully synthetic fibre?
Answer:
 Nylon.

19. Name two articles made by rayon.
Answer:
 Socks and tents.

20. Write the names of two articles made by nylon.
Answer:
 Parachutes and ropes for rock climbing.

21. Name a polyester which is commonly used.
Answer:
 Terylene is a popular polyester.

22. What is polyester?
Answer:
 The polymer made up of the repeating units of ester.

23. Which is more stronger, a wire of steal or a wire of nylon?
Answer: Wire made of nylon.

24. Name a synthetic fibre which works like wool.
Answer:
 Acrylic.

25. What are petrochemicals?
Answer:
 All the synthetic substances which are formed by using petrolium as raw material are called petrochemicals.

26. What are plastics?
Answer:
 The plastics are a polymer like the synthetic fibres which are mouldable.

27. How many types of arrangement of units are in plastics? Name them.
Answer:
 There are two types of arrangement of units in plastics:
(i) Linear linking (ii) Cross linking.

28. Name two types of plastics.
Answer:
 (i) Thermoplastics (ii) Thermosetting plastics.

29. Give two examples of thermoplastics.
Answer: 
Polythene and PVC.

30. What is the full form of PVC?
Answer: 
PVC stands for Poly Venyl Chloride.

31. Name two thermosetting plastics.
Answer:
 Bakelite and Melamine.

32. Why plastics are not ecofriendly?
Answer:
 Plastics take several years to decompose, so they are not ecofriendly.

33. What are 4Rs?
Answer: 
4Rs stand for Reduce, Reuse, Recycle and Recover.

Short Answer Type Questions

1: Differentiate between natural and artificial fibres.
Answer:
 

Natural FibresSynthetic Fibres
Comes from natureMan-made fibres
Natural colourColour as per requirement is added in colour bath
During spinning process spinneret is not necessaryDuring spinning process spinneret is necessary for the production of filament
Chances of containing dust or impuritiesNo chance of any dust or impurities
Less durable than syntheticMore durable than natural

2: Define polymer and give example of a polymer occurring in nature.

Answer: Synthetic fibres and plastics are made up of very large units called polymers, and polymers are made up of many smaller units. For example cotton is a polymer made up of cellulose and cellulose is made from large number of glucose units.

3: What are the advantages of artificial silk over natural silk?

Answer: Advantages of artificial silk over natural silk are:

  • Artificial silk or rayon is cheaper than silk,
  • It can be dyed in a variety of colours
  • It can be used to make bed sheets on mixing with cotton, and on mixing with wool can be used to make carpets.

4: Explain the first ‘’fully synthetic fibre’’.

Answer: The first fully synthetic fibre was nylon. It was prepared from coal, water and air. It is very strong, elastic and light, very easy to wash and is used for making variety of things like socks, ropes, bags, curtains, parachutes etc.

5: Why nylon fibre became popular for making clothes?

Answer: The first fully synthetic fibre was nylon. It was prepared from coal, water and air. It is very strong, elastic and light, it is very easy to wash and used for making variety of things like socks, ropes, bags, curtains, parachutes etc.

6: Why nylon is used for making parachutes and ropes for rock climbing?

Answer: Nylon thread is very strong infact it is stronger than steel wire, because of this property of nylon it is used for making parachutes and ropes for rock climbing.

7: State the unique characteristic of polyester fabric and is applications

Answer: Polyester fabrics do not get wrinkled easily and it remains crisp and can be washed easily than any other fabrics. Thus it is used to make dress, shirts etc. PET is one of the familiar form of polyester that is used to make bottles, utensils, wires and many other things

8: Name two polyester fabrics and their uses.

Answer: Terylene and PET are two widely used polyester fabrics. Terylene is used to make very fine yarn by which various dress materials are made. PET is one of the familiar form of polyester that is used to make bottles, utensils, wires and many other things

9: Name and explain a fibre which appears to resemble wool.

Answer: Acrylic fabric resembles wool, it is cheaper than wool and available is variety of colours. It is also more durable than wools.

10: State the behaviour of natural fibre and synthetic fibre on burning.

Answer: On burning a natural fibre while on burning a synthetic fibre the fabric melts rapidly and in case of synthetic clothes it sticks to the body of person wearing it and cause severe burn to that person, it is totally disastrous.

11: Why we should avoid polyester clothes while working in kitchen?

Answer: Synthetic clothes like polyesters on burning, sticks to the body of person wearing it and cause severe burn to that person, it is totally disastrous.

12: State the characteristics of synthetic fibre because of which it is used as dress materials.

Answer: Characteristics of Synthetic fibres are:

  • Less expensive than natural fibres
  • Strong and long lasting
  • Easily available
  • Easy to maintain
  • Dry up quickly

13: Do all plastics have same type of arrangement of units?

Answer: No, all plastics do not have same type of arrangement of units. In some plastics there are linear arrangement of units while in others there are cross linked arrangement of units.

14: State some of the characteristics of plastics because of which it is used for making various articles.

Answer: Characteristics of Plastics are:

  • Light weighted
  • Cheaper than metals
  • Strong and long lasting
  • Easy to handle
  • Non-reactive: they do not react with water or air, and do not get corroded easily
  • Plastics can be moulded into different shapes and sizes
  • They are easily mouldable and can be shaped in any form to make different articles.
  • They are poor conductors of heat and electricity.
  • Thus they are used on large scale in industries and for making household articles.

15: What are plastics and its different types?

Answer: Plastics are synthetic or semi-synthetic organic solids that are mouldable. Units of some plastics have linear arrangement while some plastics are formed by the cross linked arrangement of their units. Thus, plastic is used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items. Polythene is one of the most famous types of plastic, which is used in manufacturing of carry bags.
Different types of plastics are:

  • Thermoplastic
  • Thermosetting

16: Why handles of screw drivers are made of plastics?

Answer: Handles of screw drivers are made of plastics because plastics are poor conductors of heat and electricity..

17: State some of the uses of plastics in health care Industry. 

Answer: Plastics are used in healthcare industry for the following purposes:

  • Packaging of tablets
  • For making threads used for stitching wounds
  • For making syringes
  • Making gloves used by doctors
  • For making many medical instruments

18: What type of cookware is used in microwave oven and why?

Answer: Special plastic cookware is used in microwave oven for cooking food, such that inside the oven the heat cooks food but does not affect the plastic container containing food items to be cooked.

19: Identify whether the following wastes are biodegradable or non- biodegradable?
(a) Paper
(b) Aluminium
(c) Plastic bags
(d) Cotton clothes

Answer: 
(a) Biodegradable
(b) Non- biodegradable
(c) Non- biodegradable
(d) Biodegradable

20: What do you mean by environment friendly?

Answer: Products or articles that do not cause environmental pollution, and get burnt completely with releasing less poisonous fumes into the atmosphere are called environmental friendly products. They cause less harm to the environment and are thus called as eco- friendly products.

21: Why we should not throw polybags in the water bodies or on the road?

Answer: We should not throw polybags in the water bodies or on the road because animals like cow while eating garbage waste food items swallow the polythene bags and food wrappers, the plastic materials chokes the respiratory system of these animals and form a lining in their stomachs and may cause death of these animals.

22: State some of the ways to reduce the use of plastic bags in our day to day life.

Answer: Ways to reduce the use of plastic bags in our day to day life

  • Avoid use of plastics as far as possible
  • Use bags made from cotton or jute while going for shopping
  • Try to recycle plastic wastes by returning them back to your grocery shop for recycling, and by using them as garbage bag liners.
  • We can urge plastic manufacturers to develop biodegradable plastic.
  • We can urge our legislators to ban plastic in children’s toys and food and beverage containers.

23: What do you mean by the “4R principle” to develop environment friendly habits? 

Answer: The “4R principle” to develop environment friendly habits:

  • Reduce
  • Reuse
  • Recycle
  • Recover

24: Write short notes on plastics and the environment.

Answer: Plastic is polymers like synthetic fibres, it is non-eco- friendly as it takes several years to decompose and it causes environmental pollution. When it burns it releases lot of poisonous fumes, and harmful gases into the atmosphere causing air pollution.

25: Explain the differences between thermoplastics and thermosetting plastics 

Answer:

ThermoplasticThermosetting Plastic
Thermoplastic can be synthesized by the process called addition polymerization.Thermosetting plastics are synthesized by condensation polymerization.
Thermoplastic is processed by injection moulding, extrusion process, blow moulding, thermoforming process, and rotational moulding.Thermosetting Plastic is processed by compression moulding, reaction injection moulding.
Thermoplastics have secondary bonds between molecular chains.Thermosetting plastics have primary bonds between molecular chains and held together by strong cross-links.
Thermoplastics have low melting points and low tensile strength.Thermosetting plastics have high melting points and tensile strength.
Thermoplastic is lower in molecular weight, compared to thermosetting plastic.Thermosetting Plastic is high in molecular weight.

26: Neha want to buy a shirt for summer, should she buy shirt made from synthetic fibre or cotton fibre and why?

Answer: She should purchase cotton clothes for summer because it is very light fabric, easy to wear and air flow process is also good in cotton clothes so it keeps body cool during summer season.

27: Give some examples illustrating the fact that plastics are non-corrosive in nature. 

Answer:   Following examples show that plastics are non-corrosive in nature

  • They are used to store chemicals in laboratories as they don’t react with chemicals or other items in the laboratory.
  • Plastic does not decompose even when left in the open for a long period.
  • Plastic does not react even with air and water and so it dies not get rusted.
  • They are used to store all types of food, as plastic does not react to materials stored in it.

28: State the source of following fibres
a.  Cotton b. Rayon c. Nylon

Answer: a. Plants b. Wood pulp c. coal water and air

29: What is Terylene?

Answer: Terylene is an artificial textile fibre made from polyester, it is used to make light, crease-resistant clothing, bed linen, and sails.

30: Why rayon is different from other synthetic fibres?

Answer: Rayon is the only synthetic fibre obtained from a natural source that is wood pulp, that’s why it is different from other fibres.

31: What are the disadvantages of synthetic fibres?

Answer: Following are the disadvantages of synthetic fibres:

  • Synthetic fibres cannot absorb moisture. This makes them unsuitable to be warm during summer because in summer when our body sweats. These fibres make body sticky and sometimes cause skin irritation.
  • They are dangerous to be worn near fire or heat, as they easily catch fire and is unfit to be worm.
  • They cannot be easily ironed as they melt very easily.

32. Name five articles. Write the type of fibre used?

 Answer: (i) Coconut rope: Natural fibre
(ii) Cotton clothes: Natural fibre
(iii) Polyester clothes: Synthetic fibres
(iv) Basket: Synthetic fibre
(v) Parachute: Synthetic fibre.

33. What are synthetic fibres? Give two examples.

Answer: A synthetic fibre is a chain of small units joined together like necklace beads. Each small unit is actually a chemical substance. Example: Rayon and Nylon.

34. What is rayon? Why is it called an artificial silk?

Answer: Rayon is synthetic fibre having properties similar to that of silk. So it is called artificial silk. It was obtained by chemical treatment of wood pulp.

35. What are the uses of rayon?

Answer: Although rayon is obtained from a natural source called wood pulp, yet it is a man-made fibre. It is cheaper than silk. Rayon is mixed with cotton to make bedsheets or mixed with wool to make carpets.

36. What are the properties of nylon?

Answer: (i) Nylon fibres are strong.
(ii) They are elastic and light.
(iii) They are easy to wash and lustrous.

37. What are the uses of nylon?

Answer: Nylon fibres are used to make many articles, such as socks, ropes, tents, toothbrushes, car seat belt, sleeping bags, curtains, etc. Nylon is also used in making parachutes and ropes for rock climbing.

38. Why is polyester quite suitable for making dress materials?

Answer: Polyester is a synthetic fibre which is quite suitable to make dresses and other clothes due to its properties. It does not wrinkle easily. It remains crisp and is easy to wash. It is light and durable. It takes very less time to dry.

39. What are the raw materials used in making polyester?

Answer: Actually polyester is made up of the repeating units of chemical called an ester. Esters are the chemicals which give fruits their smell. The fabrics are sold by the names like polycot, polywool and terrycot.

40. What are the qualities of synthetic fibres which make them more popular than natural fibres?

Answer: The following properties make the synthetic fibres more popular:
(i) They are cheaper than natural fibres.
(ii) They are available in variety of colours.
(iii) They are more durable than natural fibres.
(iv) They are affordable.

41. Why is it convenient to store food in plastic containers than metals?

Answer: Plastic containers seem most convenient than metal containers. This is because of their light weight, lower price, good strength and easy handling. Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts also.

42. Why are plastics used widely in the industries and household articles?

Answer: Plastic is very light, strong, durable and can be moulded into different shapes and sizes. It is used in various purposes. Plastics are generally cheaper than metals.  It is also bad conductor of heat and electricity. This is because they are widely used in industries and household articles.

43. Write some uses of plastics based on the poor conductivity of heat and electricity.

Answer: Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastics. Handles of frying pans are also made of plastics.

44. What are biodegradable and non-biodegradable materials? Explain with examples.

Answer: Biodegradable material: A material, which gets decomposed through natural process, such as action by microorganisms, is called as biodegradable material. For example, paper, leaves, vegetable, fruits, etc.

Non-biodegradable material: A material, which is not easily decomposed by natural processes, such as action of microorganisms, is called as non‑biodegradable material. For example, glass, copper, plastics and synthetic fibres, etc.

45. Write disadvantages of plastics.

Answer: Plastics take several years to decompose, so they are not environment‑friendly. Plastic causes environmental pollution; besides the burning process in the synthetic materials is quite slow and it does not get completely burnt easily. In this process it releases lots of poisonous fumes into atmosphere causing air pollution.

46. Say ‘no’ to polythene bags and say ‘yes’ to paper bags. Comment on this slogan.

Answer: When we use polythene bags and throw them here and there, they are eaten by the animals like cows. The plastic materials choke the respiratory system of these animals or form a lining in their stomachs that can cause their death. Polythene bags are responsible for clogging the drains. So we should say ‘no’ to polythene bags and say ‘yes’ to paper bags.

47. Explain 4R principle.

Answer: 4R stands for:
(i) Reduce the use of non‑biodegradable things.
(ii) We should use the thing again and again (Reuse).
(iii) We should use the things which can be recycled (Recycle).
(iv) Recover the lacking substances.

Long Answer Type Question

1: “Minimise use of plastics for healthy environment”, comment on this advice.

Answer: Plastic is a polymer that can be recycled, coloured, reused, mould or drawn into wires or various other shapes. When it burns it releases lot of poisonous fumes, into the atmosphere causing air pollution. We should not throw polybags in the water bodies or on the road because animals like cow while eating garbage waste food items swallow the polythene bags and food wrappers, the plastic materials chokes the respiratory system of these animals and form a lining in their stomachs and may cause death of these animals. The polybags carelessly thrown here and there are responsible for clogging the drains too. Thus, we say we should minimise use of plastics for healthy environment by adopting the following ways:

  • Avoid use of plastics as far as possible
  • Use bags made from cotton or jute while going for shopping
  • Try to recycle plastic wastes by returning them back to your grocery shop for recycling, and by using them as garbage bag liners.
  • We can urge plastic manufacturers to develop biodegradable plastic.
  • We can urge our legislators to ban plastic in children’s toys and food and beverage containers.

2: Increasing application of synthetic fibres is actually helping in conservation of forests. Do you agree, if yes comment how?

Answer: Synthetic fibres are made by human beings by using various chemicals, it minimises the use of natural fibres whose source is plants, thus we can say increasing use of man- made fibres are playing very important role in conservation of forests.

3: What are synthetic fibres and its various types?

Answer: Fibres made by human being or man- made fibres are called synthetic fibres

Following are the various types of synthetic fibres:

  • Rayon: Rayon is synthesized from wood pulp. Rayon resembles silk, so it is also known as artificial silk. Rayon can be dyed in different colours and is much cheaper than silk.
  • Nylon: The first fully synthetic fibre was nylon. It was prepared from coal, water and air. It is very strong, elastic and light, it is very easy to wash and used for making variety of things like socks, ropes, bags, curtains, parachutes etc. Nylon thread is very strong infact it is stronger than steel wire, because of this property of nylon it is used for making parachutes and ropes for rock climbing.
  • Polyester: Polyester, one of the most popular man-made fibres. It is made of repeating unit of a chemical called ester. It is widely used to make clothes. Polyester fabrics do not get wrinkled easily and it remains crisp and can be washed easily than any other fabrics. Thus it is used to make dress, shirts etc.
    Terylene and PET are two widely used polyester fabrics. 
  • Acrylic: Acrylic fabric resembles wool, it is cheaper than wool and available is variety of colours. It is also more durable than wools.

4: Write short notes on various characteristics of synthetic fibres and natural fibre.

Answer: Characterstics of Synthetic fibres are:

  • Less expensive than natural fibres
  • Strong and long lasting
  • Easily available
  • Easy to maintain
  • Dry up quickly

Characteristics of natural fibres:
These fibers have higher tensile strength than other fibers. Therefore, these fibers are used for durable yarn, fabric, packaging, and paper. Some examples are flax, jute, industrial hemp, soybean fiber, and even vine fibers and banana fibers.

5. Explain with the help of an activity that nylon thread is stronger than cotton, wool, silk and nylon.

Answer: Take an iron stand with a clamp. Take a cotton thread of about 60 cm length. Tie it to the clamp so that it hangs freely from it as shown in figure. At the free end suspend a pan so that weight can be placed in it. Add weight one by one till the thread breaks. Note the total weight required to break the thread. Repeat the same activity with threads of wool, silk and nylon. We observe that more weight is required to break the nylon thread in comparison to other threads. So we can say that nylon is much stronger than other threads.

Class 8 Science Chapter 3 Synthetic Fibres and Plastics Important Question 1

6. Explain thermoplastics and thermosetting plastics with examples.

Answer: There are following two type of plastics:
(i) Thermoplastics (ii) Thermosetting plastics.

(i) Thermoplastics: The plastics which get deformed easily by heating and can be bent easily are known as thermoplastics. Polythene and PVC are the examples of some thermoplastics.

(ii) Thermosetting Plastics: The plastics which when moulded once cannot be softened again by heating are called thermosetting plastics. Bakelite and Melamine are two most common examples of thermosetting plastics. Bakelite is used in making electrical switches, handles of various utensils. Melamine is used for making floor tiles, kitchenware and fabrics which resist fire.


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