Glossary
- Natural Fibres
Fibres obtained from plants or animals, such as cotton, jute, wool, and silk. - Synthetic Fibres
Fibres made by humans using chemical processes; also known as man-made fibres, like nylon and polyester. - Polymer
A large molecule formed by the repeated joining of smaller molecules (monomers). - Monomer
A small molecule that joins with other monomers to form a polymer. - Polymerisation
The chemical process by which monomers are linked together to form polymers. - Semi-Synthetic Polymers
Polymers obtained by chemically treating natural polymers, like vulcanised rubber. - Rayon
A fibre made by chemically treating wood pulp; also known as artificial silk or viscose rayon. - Nylon
The first fully synthetic fibre, known for its strength, elasticity, and silk-like appearance. - Terylene
A durable, elastic, and wrinkle-resistant synthetic fibre used for fabrics and sails. - PET (Polyethylene Terephthalate)
A strong, lightweight synthetic polymer used for making bottles, containers, and packaging. - Acrylic Fibres
Synthetic fibres resembling wool, used for sweaters, blankets, and shawls. - Lustre
The shine or brightness of a material’s surface. - Non-Biodegradable
Materials that do not decompose naturally by microorganisms and persist in the environment for a long time. - Thermoplastics
Plastics that soften on heating and can be reshaped multiple times, like polyethene and PVC. - Thermosetting Plastics
Plastics that become permanently hard when heated and cannot be reshaped, like bakelite and melamine. - Linear Arrangement (of monomers)
A straight chain formation of molecules found in thermoplastics. - Cross-Linked Arrangement (of monomers)
An interconnected formation of molecules, found in thermosetting plastics. - Teflon
A special plastic known for its non-stick properties, used in cookware coatings. - Melamine
A heat and flame-resistant plastic used for making kitchenware and fire-resistant fabrics. - Biodegradable
Materials that can decompose naturally by the action of microorganisms. - Plastic Pollution
Environmental contamination caused by the accumulation of plastic products. - 4 R’s Principle
An environmental conservation strategy: Reduce, Reuse, Recycle, Recover. - Drainage Clogging
Blocking of sewage or water pipes, often caused by improper disposal of plastic waste.
Something To Know
A. Fill in the blanks.
- Fill in the blanks.
- ___________ and ___________ are examples of natural fibres.
Answer. Cotton, Jute
- The simplest molecule of a polymer is known as a ___________.
Answer. Monomer
- Rayon is also known as a ___________ fibre.
Answer. Regenerated
- Nylon is a ___________ fibre.
Answer. Synthetic
- ___________ plastics cannot be remoulded again on heating.
Answer. Thermosetting
B. State True or False for the following statements.
- Natural fibres are highly resistant to the effects of chemicals like acids and alkalis.
Answer. False
- Synthetic fibres absorb very little water.
Answer. True
- Thermoplastics can be easily remoulded on heating.
Answer. True
- The plastic, used for insulating electrical wires, is teflon
Answer. False
- All types of plastics are biodegradable.
Answer. False
C. Tick (✓) the correct option.
- The correct choice, for the box, in the following sequence, is—
thermoplastic : PVC ; thermosetting plastic : ?
nylon
polystyrene
bakelite
polythene
Answer. bakelite
- Which of the following is also known as the ‘wonder polymer’?
nylon
polystyrene
polythene
acrylic
Answer. nylon
- A highly durable synthetic fibre, used for making parachutes and ropes for rock climbing and fishing nets, is—
Rayon
terylene
nylon
PET
Answer. nylon
- Which of the following is NOT one of the characteristics of synthetic fibres?
easy to clean and dry quickly,
biodegradable.
long lasting lustre.
do not shrink on washing.
Answer. Biodegradable
- Melamine is a thermosetting plastic; for it one can say that—
it can be easily remoulded on heating.
it cannot resist fire.
it has a cross-linked arrangement of molecules.
its ‘tolerance’, towards heat is very much lower than those of other plastics.
Answer. It has a cross-linked arrangement of molecules.
- Which of the following is a correct statement about synthetic plastics?
thermoplastics cannot be deformed easily on heating.
synthetic plastics are biodegradable.
synthetic plastics get easily affected by acids and alkalis.
synthetic plastics have quite high tensile strengths.
Answer. Synthetic plastics have quite high tensile strengths.
D. Answer the following questions in brief:
- Define the term ‘synthetic fibres’.
Answer. Synthetic fibres are man-made fibres prepared by chemical processes using raw materials like petroleum products.
- Write two uses of rayon.
Answer. It is used for making clothes and bed sheets.
It is used for making curtains and carpets.
- Name two to three articles that can be made from nylon.
Answer. Ropes, parachutes, fishing nets, toothbrush bristles, and seat belts.
- Why are clothes made from synthetic fibres uncomfortable in summer?
Answer. Clothes made from synthetic fibres are uncomfortable in summer because they do not absorb sweat and trap heat, making the body feel hotter.
- Give two examples each of thermoplastics and thermosetting plastics.
Answer. Thermoplastics: Polyvinyl chloride (PVC), Polythene
Thermosetting plastics: Bakelite, Melamine
E. Answer the following questions.
- How is a ‘regenerated fibre’ different from a true synthetic fibre? Give one example of each of these two types of fibres.
Answer. A regenerated fibre is made from natural raw materials (like cellulose) but processed chemically; whereas a true synthetic fibre is entirely made from chemicals derived from petroleum.
Example of regenerated fibre: Rayon
Example of true synthetic fibre: Nylon
- Why do clothes made of nylon last longer?
Answer. Clothes made of nylon last longer because nylon is strong, elastic, resistant to abrasion, and does not wear out easily.
- Write two points of differences between thermosetting plastics and thermoplastics.
Answer.
hermosetting Plastics | Thermoplastics |
Cannot be remoulded once set; they become hard permanently. | Can be softened on heating and remoulded repeatedly. |
They have a cross-linked structure of molecules. | They have a linear or slightly branched structure of molecules. |
- State any three advantages of synthetic fibres.
Answer. hey are strong and durable.
They dry quickly and are easy to maintain.
They are resistant to shrinking and wrinkling.
- Give your views on the following: ‘Excessive use of plastics is a threat to environment.
Answer. Excessive use of plastics harms the environment because plastics are non-biodegradable, cause soil and water pollution, harm wildlife, and contribute to landfills and ocean waste problems.
- Why is bakelite a good choice for making electrical switches and handles of cooking utensils?
Answer. Bakelite is a good choice because it is a poor conductor of heat and electricity, and it is heat resistant and hard.
Value Based Question
Ankita is a keen and observant student of Science. She felt concerned when she noticed that the lady, who had joined their household for working in their kitchen, was wearing a nylon saree. She told her mother about the danger of using such a saree in the kitchen. Her mother immediately bought two cotton sarees for that lady and politely advised her to wear them only while working in the kitchen.
- State the values displayed by Ankita and her mother.
Answer. Ankita and her mother displayed values of care, responsibility, safety awareness, kindness, and empathy towards others.
- Give reason(s) that make it unsafe to use a nylon saree in the kitchen.
Answer. It is unsafe to use a nylon saree in the kitchen because nylon is a synthetic fibre that catches fire easily and melts when exposed to heat, causing severe burns and injuries.
- Have a ‘group discussion’ in which different students give their suggestions/opinion about making the kitchen a ‘safe working place’.
Answer: Group Discussion Points:
Ravi: Always wear cotton clothes in the kitchen to avoid fire accidents.
Meera: Keep a fire extinguisher handy and know how to use it.
Sahil: Avoid keeping flammable items like plastic bags near the stove.
Anita: Always turn off gas burners properly after cooking.
Tina: Use oven mitts or thick cloth to handle hot utensils.
Aman: Keep children away from cooking areas.
Pooja: Install smoke detectors in the kitchen for early warnings.
Something To Do
- Take three big plastic containers. In the first, add a few pieces from a polythene bag and fill it with garden soil. In the second, add pieces of paper and fill it with garden soil. In the third, add vegetable waste from your kitchen and fill it with garden soil. Keep the three containers on the roof and water them for 7-10 days. Check after 10 days and find out which material undergoes decomposition faster. Make a project report on the above activity.
Answer. Aim:
To study the rate of decomposition of polythene, paper, and vegetable waste.
Materials Required:
Three big plastic containers
Pieces of polythene bag
Pieces of paper
Vegetable waste
Garden soil
Water
Procedure:
In the first container, add polythene pieces and fill with garden soil.
In the second container, add paper pieces and fill with garden soil.
In the third container, add vegetable waste and fill with garden soil.
Keep all containers on the rooftop and water them daily for 7–10 days.
After 10 days, observe the level of decomposition.
Observations:
Polythene pieces showed no change or decomposition.
Paper pieces started breaking down partially.
Vegetable waste decomposed the most, turning into moist, crumbly organic matter.
Conclusion:
Vegetable waste decomposes the fastest because it is biodegradable. Polythene does not decompose as it is non-biodegradable.
- Visit a few families in your neighbourhood and enquire about the kind of clothes they use, the reason for their choice and advantages of using them. Make a short report on your ‘findings’.
Answer. Title:
Survey Report on the Choice of Clothes in the Neighbourhood
Method:
Visited five families and asked about the kind of clothes they prefer, reasons, and advantages.
Findings:
Most families preferred cotton clothes for daily use because they are comfortable, breathable, and absorb sweat, especially in summers.
Some preferred synthetic clothes (like polyester blends) for party wear as they have good shine, require less ironing, and dry quickly.
In winters, families used woollen clothes for warmth.
Conclusion:
Cotton remains the first choice for comfort, while synthetic fibres are preferred for special occasions due to ease of maintenance.
- Design posters, with ‘catchy slogans’ and ‘relevant pictures’, to spread awareness about the judicious use of plastics.
Answer. Poster Ideas: Judicious Use of Plastics
Poster 1:
Slogan:
“Use Less Plastic, Save More Earth!”
Picture:
A globe trapped in a plastic bag with a warning sign.
Poster 2:
Slogan:
“Say No to Plastic Bags – Carry Your Own Cloth Bag!”
Picture:
A happy family shopping with cloth bags.
Poster 3:
Slogan:
“Refuse, Reuse, Recycle – For a Cleaner Tomorrow!”
Picture:
Three arrows forming a recycling symbol with plastic bottles being reused.
Additional Questions and Answers – 01
Short Questions:
Question – What is a polymer?
Answer: A polymer is a large molecule made up of repeating structural units called monomers, which are chemically bonded together.
Question – What is the difference between rayon and silk?
Answer: Rayon is an artificial fibre made from wood pulp, while silk is a natural fibre obtained from silkworms.
Question – Why is nylon called the ‘wonder polymer’?
Answer: Nylon is called the ‘wonder polymer’ because of its strength, elasticity, and wide range of uses in various industries.
Question – What is the raw material used in the preparation of rayon?
Answer: The raw material used in the preparation of rayon is wood cellulose.
Question – What is the main advantage of synthetic fibres over natural fibres?
Answer: Synthetic fibres are more durable, easy to maintain, and less expensive compared to natural fibres.
Long Questions:
Question – Explain the process of polymerisation. How do synthetic fibres form in this process?
Answer: Polymerisation is the process in which small molecules, called monomers, chemically bond together to form long-chain molecules called polymers. In the case of synthetic fibres, monomers such as nylon, polyester, or acrylic are chemically treated to join together, creating long chains that form the fibres. These fibres are then spun into yarn and used to make various fabrics.
Question – Describe the characteristics and uses of synthetic fibres.
Answer: Synthetic fibres like nylon, polyester, and acrylic are durable, resistant to wrinkles, and easy to maintain. They are lightweight and dry quickly. These fibres are commonly used in making clothes, ropes, and upholstery, and are also used in industrial applications such as making parachutes, tyres, and fishing nets. The advantages of synthetic fibres include low cost, high durability, and easy maintenance. However, they have drawbacks like low breathability and non-biodegradability.
Question – What are the environmental impacts of synthetic fibres and plastics? Suggest ways to mitigate these impacts.
Answer: Synthetic fibres and plastics contribute to environmental pollution because they are non-biodegradable. They take hundreds of years to decompose and can clog drains, harm wildlife, and pollute oceans. To mitigate these impacts, people can reduce the use of single-use plastics, recycle synthetic materials, and opt for biodegradable alternatives like jute, cotton, or paper. It’s also important to follow the 4 R’s principle: Reduce, Reuse, Recycle, and Recover.
Question – How do thermoplastics and thermosetting plastics differ in terms of their properties and uses?
Answer: Thermoplastics can be softened on heating and moulded into new shapes, making them versatile and easy to recycle. Examples include polyethylene and PVC. Thermosetting plastics, on the other hand, cannot be remoulded once they are set because their molecules are cross-linked. These plastics are heat-resistant and used in products like electrical switches and handles. Examples include Bakelite and melamine.
True/False Questions:
Question – Synthetic fibres are biodegradable.
Answer: False
Question – Nylon is an example of a natural fibre.
Answer: False
Question – Rayon is made from wood pulp, a natural source.
Answer: True
Question – Thermosetting plastics can be reshaped when heated.
Answer: False
Question – Polythene is an example of a thermoplastic.
Answer: True
Multiple Choice Questions (MCQs):
Question – Which of the following is a synthetic fibre?
- a) Cotton
- b) Silk
- c) Nylon
- d) Wool
Answer: c) Nylon
Question – Which of the following is used to make non-stick cookware?
- a) Bakelite
- b) Teflon
- c) PVC
- d) Polystyrene
Answer: b) Teflon
Question – Which of these is a characteristic of thermosetting plastics?
- a) They can be remoulded on heating.
- b) They are made of linear arrangements of molecules.
- c) They cannot be remoulded once set.
- d) They are easily soluble in water.
Answer: c) They cannot be remoulded once set.
Question – Which synthetic fibre is commonly used in the manufacture of parachutes?
- a) Rayon
- b) Nylon
- c) Terylene
- d) Polyester
Answer: b) Nylon
Question – Which material is used for making magnetic tapes for audio and video recorders?
- a) PET
- b) Acrylic
- c) Nylon
- d) Rayon
Answer: a) PET
Additional Questions and Answers – 02
Short Questions & Answers
Question – What are natural fibres?
Ans: Natural fibres are obtained from natural sources like plants (cotton, jute) and animals (wool, silk).
Question – Why are synthetic fibres developed?
Ans: Synthetic fibres are developed to meet the increasing demand for fibres that natural fibres cannot fulfill.
Question – What is polymerisation?
Ans: Polymerisation is the process of joining small molecules (monomers) to form a long-chain polymer.
Question – What is the raw material for rayon?
Ans: Wood cellulose (a natural fibre) is the raw material for rayon.
Question – Why is nylon called a “wonder polymer”?
Ans: Nylon is the first fully synthetic fibre with high elasticity, strength, and durability.
Question – Give two uses of terylene.
Ans: Used for making sails and raincoats.
Used in conveyor belts and home furnishings.
Question – What is PET used for?
Ans: PET is used for making bottles, food containers, and magnetic tapes.
Question – Why are acrylic fibres popular?
Ans: They resemble wool, are lightweight, less expensive, and available in many colours.
Question – What is the main disadvantage of synthetic fibres?
Ans: They have a low melting point, do not absorb sweat, and are non-biodegradable.
Question – What are thermoplastics?
Ans: Plastics that can be melted and reshaped repeatedly (e.g., PVC, nylon).
Question – What are thermosetting plastics?
Ans: Plastics that cannot be reshaped after setting (e.g., Bakelite, melamine).
Question – Why is melamine used in firemen’s uniforms?
Ans: Because it is flame-resistant.
Question – What are biodegradable materials?
Ans: Materials that decompose naturally (e.g., paper, cotton).
Question – Why is plastic harmful to the environment?
Ans: It is non-biodegradable, clogs drains, harms animals, and releases toxic gases when burnt.
Question – What is the 4 R’s principle?
Ans: Reduce, Reuse, Recycle, Recover.
Long Questions & Answers
Question – Explain the difference between natural and synthetic fibres with examples.
Ans: Natural fibres are obtained from plants (cotton, jute) or animals (wool, silk).
Synthetic fibres are man-made (rayon, nylon, polyester).
Natural fibres are biodegradable but limited in supply, while synthetic fibres are durable, non-biodegradable, and mass-produced.
Question – Describe the properties and uses of nylon.
Ans: Properties: Strong, elastic, durable, lightweight, resistant to chemicals.
Uses:
Clothing (socks, carpets).
Military (ropes, parachutes).
Household items (toothbrushes, fishing nets).
Question – What are the advantages and disadvantages of synthetic fibres?
Ans: Advantages:
Long-lasting, wrinkle-resistant, quick-drying, affordable.
Disadvantages:
Low melting point, non-absorbent, non-biodegradable.
Question – Differentiate between thermoplastics and thermosetting plastics.
Ans: Thermoplastics (e.g., PVC, nylon) can be remoulded on heating.
Thermosetting plastics (e.g., Bakelite, melamine) cannot be reshaped once set.
Question – How does plastic waste harm the environment? Suggest solutions.
Ans: Harm: Clogs drains, kills animals, pollutes soil and air.
Solutions:
Use cotton/jute bags.
Separate biodegradable/non-biodegradable waste.
Follow the 4 R’s principle.
True/False Questions
Question – Rayon is a natural fibre.
Ans: False (It is semi-synthetic).
Question – Nylon is the first fully synthetic fibre.
Ans: True.
Terylene absorbs water easily.
Ans: False (It is water-resistant).
Question – PET is used for making bottles.
Ans: True.
Question – Acrylic fibres are a substitute for wool.
Ans: True.
Thermoplastics can be remoulded.
Ans: True.
Question – Melamine is a thermosetting plastic.
Ans: True.
Question – Plastic is biodegradable.
Ans: False.
Question – Burning plastic releases harmless gases.
Ans: False (It releases toxic gases).
Question – The 4 R’s principle includes “Repair.”
Ans: False (Reduce, Reuse, Recycle, Recover).
MCQs (Multiple Choice Questions)
Question – Which fibre is obtained from wood pulp?
- a) Cotton
- b) Rayon
- c) Nylon
- d) Silk
Ans: b) Rayon
Question – Which synthetic fibre is known as ‘artificial silk’?
- a) Nylon
- b) Acrylic
- c) Rayon
- d) Polyester
Ans: c) Rayon
Question – Which plastic is used for making non-stick cookware?
- a) Bakelite
- b) Teflon
- c) Melamine
- d) PVC
Ans: b) Teflon
Question – Which of the following is a thermosetting plastic?
- a) PVC
- b) Nylon
- c) Bakelite
- d) Polyethene
Ans: c) Bakelite
Question – Which property is NOT true for synthetic fibres?
- a) Absorbs sweat
- b) Lightweight
- c) Durable
- d) Wrinkle-resistant
Ans: a) Absorbs sweat
Question – PET is used for making:
- a) Bottles
- b) Electrical switches
- c) Cookware
- d) Blankets
Ans: a) Bottles
Question – Which of these is biodegradable?
- a) Plastic bag
- b) Cotton cloth
- c) PVC pipe
- d) Polystyrene
Ans: b) Cotton cloth
Question – The term ‘polymer’ comes from Greek words meaning:
- a) Many parts
- b) Strong material
- c) Artificial fibre
- d) Long chain
Ans: a) Many parts
Question – Which fibre is used in making parachutes?
- a) Jute
- b) Nylon
- c) Silk
- d) Rayon
Ans: b) Nylon
Question – Which plastic is flame-resistant?
- a) PVC
- b) Melamine
- c) Polyethene
- d) Terylene
Ans: b) Melamine