Synthetic Fibres and Plastics – MCQs with Answers and Explanations
Class 8
Science — Chapter 3: Synthetic Fibres and Plastics
CBSE Board Examinations
CBSE Board Examinations — Systematic order (how to use these MCQs)
- Use in class tests and quick quizzes to check understanding of key concepts.
- Practice before unit tests and half-yearly exams to revise important facts and applications.
- Use the explanations to clear concepts, not just memorize answers.
Topic A: Introduction to Synthetic Fibres (1–10)
1. Which of the following is a synthetic fibre?
Correct: C. Nylon
Nylon is a man-made (synthetic) fibre produced by polymerisation of chemical monomers. Cotton, wool and silk are natural fibres.
Nylon is a man-made (synthetic) fibre produced by polymerisation of chemical monomers. Cotton, wool and silk are natural fibres.
2. Which synthetic fibre was the first to be fully synthetic and commercially successful?
Correct: B. Nylon
Nylon, invented in the 1930s, was the first fully synthetic fibre to achieve wide commercial use, notably in stockings and parachutes.
Nylon, invented in the 1930s, was the first fully synthetic fibre to achieve wide commercial use, notably in stockings and parachutes.
3. Rayon is considered an artificial fibre because it is made from:
Correct: B. Cellulose from wood pulp
Rayon (viscose) is a regenerated cellulose fibre made from wood pulp; hence it is called artificial or regenerated fibre, not fully synthetic.
Rayon (viscose) is a regenerated cellulose fibre made from wood pulp; hence it is called artificial or regenerated fibre, not fully synthetic.
4. One advantage of synthetic fibres over natural fibres is:
Correct: C. Greater elasticity and durability
Synthetic fibres like nylon and polyester are usually more elastic, strong and durable compared to many natural fibres.
Synthetic fibres like nylon and polyester are usually more elastic, strong and durable compared to many natural fibres.
5. Which synthetic fibre is commonly used to make fishing nets and ropes?
Correct: B. Nylon
Nylon is strong, elastic and resists water damage, making it suitable for fishing nets and ropes.
Nylon is strong, elastic and resists water damage, making it suitable for fishing nets and ropes.
6. Synthetic fibres are mainly produced by which chemical process?
Correct: C. Polymerisation
Synthetic fibres are produced by polymerisation where many small molecules (monomers) join to form long chains (polymers).
Synthetic fibres are produced by polymerisation where many small molecules (monomers) join to form long chains (polymers).
7. Which of the following is NOT a property commonly associated with synthetic fibres?
Correct: B. High absorbency of water
Most synthetic fibres have low moisture absorbency compared to natural fibres like cotton, so they dry quickly rather than absorb much water.
Most synthetic fibres have low moisture absorbency compared to natural fibres like cotton, so they dry quickly rather than absorb much water.
8. Polyester is derived from:
Correct: C. Petroleum-derived chemicals
Polyester is a synthetic polymer made using petrochemical feedstocks through chemical reactions.
Polyester is a synthetic polymer made using petrochemical feedstocks through chemical reactions.
9. Which fibre is often used in warm clothing due to its insulating property?
Correct: B. Acrylic
Acrylic fibre resembles wool and is used in sweaters and blankets for insulation and warmth.
Acrylic fibre resembles wool and is used in sweaters and blankets for insulation and warmth.
10. A fabric that combines cotton and polyester aims to:
Correct: C. Combine comfort of cotton with durability of polyester
Blending fibres lets manufacturers combine desirable properties — comfort and breathability from cotton and strength and wrinkle-resistance from polyester.
Blending fibres lets manufacturers combine desirable properties — comfort and breathability from cotton and strength and wrinkle-resistance from polyester.
Topic B: Properties and Tests (11–25)
11. During a burn test, synthetic fibres generally:
Correct: B. Melt and form beads
Synthetic fibres often melt on heating and may form hard beads, unlike cotton which burns to ash and wool which chars.
Synthetic fibres often melt on heating and may form hard beads, unlike cotton which burns to ash and wool which chars.
12. Which fibre would you expect to feel cool and breathable in hot weather?
Correct: A. Cotton
Cotton is a natural fibre with good breathability and moisture absorbency, making it comfortable in hot climates.
Cotton is a natural fibre with good breathability and moisture absorbency, making it comfortable in hot climates.
13. Which test would best distinguish between wool and nylon?
Correct: B. Burning test (smell and residue)
Wool smells like burning hair and chars; nylon melts and forms hard beads — burn test (with safety) helps distinguish them.
Wool smells like burning hair and chars; nylon melts and forms hard beads — burn test (with safety) helps distinguish them.
14. Synthetic fibres are preferred for sportswear because they:
Correct: B. Dry quickly and resist wrinkles
The low moisture absorbency and quick-drying nature of synthetic fibres make them suitable for activewear.
The low moisture absorbency and quick-drying nature of synthetic fibres make them suitable for activewear.
15. Which of these properties is typical of polyester?
Correct: C. Resistant to wrinkles and shrinking
Polyester resists creasing and shrinking, contributing to low-maintenance clothing.
Polyester resists creasing and shrinking, contributing to low-maintenance clothing.
16. Which fibre is known as 'artificial silk'?
Correct: A. Rayon
Rayon has a shiny, smooth texture similar to silk and is often called artificial silk.
Rayon has a shiny, smooth texture similar to silk and is often called artificial silk.
17. A fabric that stretches a lot and returns to its original shape likely contains:
Correct: B. Elastic synthetic fibres like nylon or spandex
Elasticity is provided by synthetic fibres designed to stretch and recover, useful in activewear and hosiery.
Elasticity is provided by synthetic fibres designed to stretch and recover, useful in activewear and hosiery.
18. Which property of a polymer determines whether it is a thermoplastic or thermosetting plastic?
Correct: B. Whether its chains are cross-linked permanently
Thermosetting plastics have permanent cross-links making them irreversibly set; thermoplastics soften on heating due to lack of permanent cross-links.
Thermosetting plastics have permanent cross-links making them irreversibly set; thermoplastics soften on heating due to lack of permanent cross-links.
19. Which test is UNSAFE to perform by students without supervision?
Correct: B. Burning test of fibres
Burn tests involve open flames and noxious fumes — only trained teachers should conduct them with precautions.
Burn tests involve open flames and noxious fumes — only trained teachers should conduct them with precautions.
20. Which of the following is true about synthetic fibres?
Correct: B. They often have lower moisture regain than natural fibres
Synthetic fibres typically absorb less water and hence have lower moisture regain, affecting comfort and drying properties.
Synthetic fibres typically absorb less water and hence have lower moisture regain, affecting comfort and drying properties.
Topic C: Plastics — Types and Uses (21–35)
21. Which of the following is a thermosetting plastic?
Correct: B. Bakelite
Bakelite is a thermosetting plastic that does not soften on heating due to its cross-linked structure; used in electrical fittings and handles.
Bakelite is a thermosetting plastic that does not soften on heating due to its cross-linked structure; used in electrical fittings and handles.
22. Which plastic is commonly used for making water bottles and food containers and is often recyclable?
Correct: A. PET (Polyethylene terephthalate)
PET is widely used for bottles and is identified by recycling code 1; it is recyclable through suitable processes.
PET is widely used for bottles and is identified by recycling code 1; it is recyclable through suitable processes.
23. Which plastic is used for electrical insulation and is heat-resistant?
Correct: B. Bakelite
Bakelite's thermosetting nature and heat resistance make it useful in electrical insulators and switches.
Bakelite's thermosetting nature and heat resistance make it useful in electrical insulators and switches.
24. Which plastic softens on heating and can be remoulded?
Correct: B. Thermoplastic like polythene
Thermoplastics soften when heated and can be remoulded multiple times; polythene is a common example.
Thermoplastics soften when heated and can be remoulded multiple times; polythene is a common example.
25. Which plastic is commonly used for making pipes, raincoats and insulation?
Correct: A. PVC and polythene
Pipes are often made from PVC and polythene; raincoats commonly use coated polythene or PVC-based fabrics.
Pipes are often made from PVC and polythene; raincoats commonly use coated polythene or PVC-based fabrics.
26. Which property makes plastics useful in packaging?
Correct: B. Lightweight and mouldability
Plastics are light, can be shaped into films or containers and provide barriers to moisture — ideal for packaging.
Plastics are light, can be shaped into films or containers and provide barriers to moisture — ideal for packaging.
27. Which of these is a common problem caused by careless disposal of plastics?
Correct: B. Blocked drainage and harm to wildlife
Plastics do not decompose quickly and can block drains and be ingested by animals, causing harm.
Plastics do not decompose quickly and can block drains and be ingested by animals, causing harm.
28. Which symbol or feature helps identify the type of plastic for recycling?
Correct: A. Recycling number/symbol on product
Recycling codes (1–7) indicate the polymer type, guiding proper recycling and disposal methods.
Recycling codes (1–7) indicate the polymer type, guiding proper recycling and disposal methods.
29. Which plastic is often used to make toys but must be checked for safety in toddlers?
Correct: A. PVC and other common plastics
Many toys are made from plastics like PVC or ABS; parents should ensure they are non-toxic and free from small parts.
Many toys are made from plastics like PVC or ABS; parents should ensure they are non-toxic and free from small parts.
30. Which of the following plastics is associated with good barrier properties for food packaging?
Correct: A. PET
PET offers a strong barrier to gases and moisture for many beverages and food items, making it suitable for packaging.
PET offers a strong barrier to gases and moisture for many beverages and food items, making it suitable for packaging.
Topic D: Environmental Impact & Waste Management (31–40)
31. Microplastics are:
Correct: B. Tiny plastic particles less than 5 mm
Microplastics come from breakdown of larger plastics and from products containing microbeads; they can enter food chains and water bodies.
Microplastics come from breakdown of larger plastics and from products containing microbeads; they can enter food chains and water bodies.
32. Which is a practical method to reduce plastic waste at home?
Correct: B. Reuse containers and use cloth bags
Reusing items and choosing reusable alternatives reduces demand for single-use plastics and lowers waste generation.
Reusing items and choosing reusable alternatives reduces demand for single-use plastics and lowers waste generation.
33. Which practice helps in proper disposal of plastic bottles?
Correct: B. Rinsing, sorting by type and placing in recycling bin
Cleaning and sorting bottles increases recycling efficiency and reduces contamination in recycling streams.
Cleaning and sorting bottles increases recycling efficiency and reduces contamination in recycling streams.
34. Which of these is NOT an effect of plastic pollution?
Correct: C. Immediate and rapid composting into rich soil
Plastics do not compost rapidly; they persist and cause long-term environmental damage, not beneficial composting.
Plastics do not compost rapidly; they persist and cause long-term environmental damage, not beneficial composting.
35. Which activity can schools do to raise awareness about plastic pollution?
Correct: A. Organise clean-up drives and recycling workshops
Clean-ups and workshops teach practical steps students can take and foster responsible behaviour towards plastic use and disposal.
Clean-ups and workshops teach practical steps students can take and foster responsible behaviour towards plastic use and disposal.
Topic E: Polymers & Industry (36–50)
36. A monomer is:
Correct: B. A small molecule that can join with others to form a polymer
Monomers are the building blocks that polymerise to create long-chain polymers (plastics and synthetic fibres).
Monomers are the building blocks that polymerise to create long-chain polymers (plastics and synthetic fibres).
37. Ethene (ethylene) is the monomer for which polymer?
Correct: B. Polythene (polyethylene)
Polymerisation of many ethene molecules leads to polythene, a common plastic used in bags and packaging.
Polymerisation of many ethene molecules leads to polythene, a common plastic used in bags and packaging.
38. Which statement about synthetic fibres and environment is correct?
Correct: B. Some synthetic fibres contribute to microplastic pollution when washed
Washing synthetic clothes may release microfibres that enter waterways, contributing to microplastic pollution.
Washing synthetic clothes may release microfibres that enter waterways, contributing to microplastic pollution.
39. Which industry uses synthetic fibres extensively?
Correct: A. Textile industry
The textile industry uses synthetic fibres for clothing, home textiles and technical fabrics due to their varied properties.
The textile industry uses synthetic fibres for clothing, home textiles and technical fabrics due to their varied properties.
40. Which practice would reduce microfibre pollution from washing clothes?
Correct: A. Using a lint filter or washing bag for synthetic clothes
Lint filters and special washing bags (or filters) can capture microfibres released during washing, reducing pollution.
Lint filters and special washing bags (or filters) can capture microfibres released during washing, reducing pollution.
41. Which plastic is identified by recycling code 2 (HDPE)?
Correct: A. High-density polyethylene, used in milk bottles and containers
HDPE is a sturdy plastic used for containers and is commonly recycled (code 2).
HDPE is a sturdy plastic used for containers and is commonly recycled (code 2).
42. Which of these is NOT a suitable way to manage plastic waste sustainably?
Correct: C. Open burning without controls
Open burning releases toxic fumes and is harmful — it is not a sustainable waste management practice.
Open burning releases toxic fumes and is harmful — it is not a sustainable waste management practice.
43. Which of these is a reason manufacturers blend fibres (e.g., cotton-polyester blends)?
Correct: A. To combine desirable properties like comfort and durability
Blending balances properties — cotton adds comfort, polyester adds strength, reducing wrinkles and maintenance needs.
Blending balances properties — cotton adds comfort, polyester adds strength, reducing wrinkles and maintenance needs.
44. Which statement correctly describes thermoplastics?
Correct: B. They soften on heating and can be remoulded
Thermoplastics can be heated and reshaped multiple times, which aids recycling and manufacturing processes.
Thermoplastics can be heated and reshaped multiple times, which aids recycling and manufacturing processes.
45. Which plastic is commonly used for electrical wires insulation?
Correct: A. PVC (Polyvinyl chloride)
PVC is a durable plastic used for insulating wires, pipes and other electrical applications.
PVC is a durable plastic used for insulating wires, pipes and other electrical applications.
46. Which is an advantage of using plastics in medicine (e.g., syringes, tubing)?
Correct: B. They are light, can be made sterile and disposable
Plastics enable manufacture of sterile, single-use medical devices that reduce infection risk and are lightweight.
Plastics enable manufacture of sterile, single-use medical devices that reduce infection risk and are lightweight.
47. Which process converts monomers to polymers?
Correct: A. Polymerisation
Polymerisation joins monomers into long polymer chains — the fundamental process for making plastics and synthetic fibres.
Polymerisation joins monomers into long polymer chains — the fundamental process for making plastics and synthetic fibres.
48. Which of the following helps reduce plastic waste in stores?
Correct: B. Encouraging customers to bring reusable bags
Encouraging reusable bags reduces demand for single-use plastics and lowers waste generation from stores.
Encouraging reusable bags reduces demand for single-use plastics and lowers waste generation from stores.
49. Which term describes breaking down of plastic into tiny particles over time?
Correct: B. Fragmentation into microplastics
Large plastic items fragment under sunlight and mechanical forces into microplastics, which are persistent and problematic.
Large plastic items fragment under sunlight and mechanical forces into microplastics, which are persistent and problematic.
50. Which is a responsible action students can take to manage plastic use?
Correct: B. Carry reusable bottles, avoid single-use plastics and participate in recycling
Practical actions like carrying reusable items and participating in recycling reduce plastic pollution and promote sustainability.
Practical actions like carrying reusable items and participating in recycling reduce plastic pollution and promote sustainability.