Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
Worksheet – FULL Answers (Step-by-Step)

---

Q1. What are synthetic fibres?

Answer: Synthetic fibres are fibres made by humans using chemical substances. They are not obtained from plants or animals.
Examples: Nylon, Rayon, Polyester, Acrylic.

Q2. Why is rayon called artificial silk?

Answer: Rayon is called artificial silk because it looks like silk and has a shiny appearance like silk, but it is made from wood pulp using chemical treatment.

Q3. Write two uses of nylon.

Answer:
1. Nylon is used to make ropes, parachutes and fishing nets.
2. It is used in making seat belts and toothbrush bristles.

Q4. What is polyester? Write one use.

Answer: Polyester is a synthetic fibre made from chemical substances.
Use: It is used to make clothes, curtains and bedsheets.

Q5. Name two types of plastics.

Answer:
1. Thermoplastics
2. Thermosetting plastics

Q6. What are thermoplastics?

Answer: Thermoplastics are plastics which soften on heating and harden on cooling. They can be moulded again and again.
Examples: Polythene, PVC.

Q7. What are thermosetting plastics?

Answer: Thermosetting plastics are plastics which do not soften when heated once. They cannot be reshaped.
Examples: Bakelite, Melamine.

Q8. Why should plastics be avoided?

Answer: Plastics should be avoided because:
• They are non-biodegradable
• They cause soil and water pollution
• Burning plastics releases toxic gases

Q9. Why is bakelite used for electrical switches?

Answer: Bakelite is a poor conductor of heat and electricity. Therefore, it is safe to use for making electrical switches and plugs.

Q10. Write two advantages of synthetic fibres.

Answer:
1. They are strong and durable.
2. They are lightweight and easy to maintain.

---

🌟 Step-by-step answers help students understand concepts clearly

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
MCQs (Exam Level)

---

1. Synthetic fibres are made from
   A. Natural plants
   B. Animal hair
   C. Chemical substances
   D. Cotton fibres
   Answer: C


2. Which of the following is known as artificial silk?
   A. Nylon
   B. Rayon
   C. Polyester
   D. Acrylic
   Answer: B


3. Which fibre is commonly used to make sweaters and shawls?
   A. Rayon
   B. Nylon
   C. Acrylic
   D. Polyester
   Answer: C


4. The plastic which can be recycled is called
   A. Thermosetting plastic
   B. Bakelite
   C. Melamine
   D. Thermoplastic
   Answer: D


5. Which plastic is used for making electrical switches?
   A. Polythene
   B. PVC
   C. Bakelite
   D. Teflon
   Answer: C


6. Why should plastics not be burnt?
   A. They melt easily
   B. They produce toxic gases
   C. They dissolve in water
   D. They shrink
   Answer: B


7. Which of the following is NOT a property of plastics?
   A. Lightweight
   B. Durable
   C. Biodegradable
   D. Strong
   Answer: C


8. Nylon was first prepared in the year
   A. 1911
   B. 1920
   C. 1931
   D. 1940
   Answer: C


9. Which material is best suited for making parachutes?
   A. Cotton
   B. Wool
   C. Nylon
   D. Silk
   Answer: C


10. Plastics are non-biodegradable because
    A. They are heavy
    B. Microorganisms cannot decompose them
    C. They dissolve in soil
    D. They melt easily
    Answer: B

---

⭐ These MCQs are important for school & competitive exams

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
Important Exam Questions

---

🟢 Very Short Answer Questions (1 Mark)

1. What are synthetic fibres?
2. Name the fibre that looks like silk.
3. Which plastic is used to make electrical switches?
4. Give one example of thermoplastic.
5. From which raw material is nylon made?

🟡 Short Answer Questions (2–3 Marks)

1. Why is rayon called a semi-synthetic fibre?
2. Write any two characteristics of synthetic fibres.
3. Differentiate between thermoplastic and thermosetting plastic.
4. Why should plastics not be burnt?
5. What is meant by biodegradable and non-biodegradable substances?

🔵 Short Answer Questions – Concept Based

1. Why are plastic containers preferred for storing food?
2. Why is nylon used for making parachutes and ropes?
3. Why are synthetic fibres wrinkle-resistant?
4. What happens when plastics are thrown in water bodies?

🟣 Long Answer Questions (4–5 Marks)

1. Explain different types of synthetic fibres with examples.
2. Write advantages and disadvantages of plastics.
3. Explain why plastic is considered a threat to the environment.
4. Describe the properties of plastics that make them useful in daily life.

🔴 Case-Based / HOTS Questions

1. Plastic bags block drains during rains. (a) Why does this happen? (b) Suggest two ways to reduce plastic pollution.
2. A student wants a material that is strong, lightweight, and water-resistant. Which synthetic fibre will you suggest? Give reasons.

---

⭐ These questions are very important for exams – prepare thoroughly

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
Worksheet – FULL Answers (Step-by-Step)

---

🟢 Section A: Very Short Answer – Answers

1. Synthetic fibre: Fibres made by humans using chemical substances are called synthetic fibres.
2. Fibre from wood pulp: Rayon.
3. Artificial silk: Rayon.
4. Thermoplastic example: Polythene.
5. Plastic for switches: Bakelite.

🟡 Section B: Short Answer – Answers

1. Why rayon is semi-synthetic:
   Rayon is made from natural raw material (wood pulp) but processed chemically. Hence, it is called semi-synthetic.
2. Two properties of synthetic fibres:
   (i) They are strong and durable.
   (ii) They are wrinkle-resistant.
3. Difference between natural and synthetic fibres:
   Natural fibres are obtained from plants or animals, while synthetic fibres are made by chemical processes.
4. Why plastics should not be burned:
   Burning plastics releases poisonous gases which pollute air and harm living beings.
5. Biodegradable and non-biodegradable substances:
   Biodegradable substances decompose naturally, whereas non-biodegradable substances do not decompose easily.

🔵 Section C: Fill in the Blanks – Answers

1. Nylon fibre is obtained from petroleum.
2. Plastics are non-biodegradable in nature.
3. Bakelite is a thermosetting plastic.
4. Rayon resembles silk.
5. Plastic bags cause environmental pollution.

🟣 Section D: MCQs – Answers

1. Strongest fibre:
   Answer: (c) Nylon
2. Plastic used for non-stick cookware:
   Answer: (c) Teflon

🔴 Section E: Long Answer – Answers

1. Types of synthetic fibres:
   Rayon, nylon, polyester, and acrylic are common synthetic fibres. They are strong, durable, and easy to maintain.
2. Advantages and disadvantages of plastics:
   Advantages: Lightweight, durable, waterproof.
   Disadvantages: Non-biodegradable and pollute the environment.
3. Why plastic is a threat:
   Plastic does not decompose easily, blocks drains, harms animals, and pollutes land and water.

---

✅ Practice answers carefully for exam success

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
Worksheet – Practice Questions

---

🟢 Section A: Very Short Answer (VSA)

1. What is a synthetic fibre?
2. Name the fibre obtained from wood pulp.
3. Which synthetic fibre is known as artificial silk?
4. Give one example of thermoplastic.
5. Name a plastic used for making electrical switches.

🟡 Section B: Short Answer (SA)

1. Why is rayon called a semi-synthetic fibre?
2. Write any two properties of synthetic fibres.
3. Differentiate between natural fibres and synthetic fibres.
4. Why should plastics not be burned?
5. What are biodegradable and non-biodegradable substances?

🔵 Section C: Fill in the Blanks

1. _________ fibre is obtained from petroleum.
2. Plastics are __________ in nature.
3. Bakelite is a __________ plastic.
4. Rayon resembles __________.
5. Plastic bags cause __________ pollution.

🟣 Section D: Choose the Correct Answer

1. Which fibre is strongest among the following?
   a) Cotton
   b) Wool
   c) Nylon
   d) Silk
2. Which plastic is used to make non-stick cookware?
   a) PVC
   b) Bakelite
   c) Teflon
   d) Polythene

🔴 Section E: Long Answer (LA)

1. Explain the different types of synthetic fibres with examples.
2. Describe the advantages and disadvantages of plastics.
3. Why is plastic considered a threat to the environment?

---

✍️ Practice regularly to master this chapter

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
MCQs (Exam Level)

---

1. Which of the following is a synthetic fibre?
   a) Cotton
   b) Wool
   c) Nylon
   d) Silk

   Answer: c) Nylon

2. Rayon is obtained from:
   a) Petroleum
   b) Wood pulp
   c) Coal
   d) Cotton seeds

   Answer: b) Wood pulp

3. Which synthetic fibre resembles silk?
   a) Nylon
   b) Polyester
   c) Rayon
   d) Acrylic

   Answer: c) Rayon

4. Which plastic can be softened on heating and reshaped?
   a) Bakelite
   b) Melamine
   c) Thermosetting plastic
   d) Thermoplastic

   Answer: d) Thermoplastic

5. Which of the following is a thermosetting plastic?
   a) PVC
   b) Polythene
   c) Bakelite
   d) Nylon

   Answer: c) Bakelite

6. Plastic is not biodegradable because:
   a) It is soft
   b) It is colourful
   c) Microorganisms cannot decompose it
   d) It dissolves in water

   Answer: c) Microorganisms cannot decompose it

7. Which property makes plastics suitable for storing food?
   a) High conductivity
   b) Reactivity
   c) Non-reactive nature
   d) Transparency

   Answer: c) Non-reactive nature

8. Which plastic is used for making electrical switches?
   a) PVC
   b) Polythene
   c) Bakelite
   d) Polyester

   Answer: c) Bakelite

9. Which fibre is known as artificial wool?
   a) Nylon
   b) Rayon
   c) Acrylic
   d) Polyester

   Answer: c) Acrylic

10. Burning plastics is harmful because:
    a) It releases oxygen
    b) It produces pleasant smell
    c) It releases poisonous gases
    d) It reduces pollution

    Answer: c) It releases poisonous gases

---

✅ Practice MCQs = Better Exam Performance

 

Class 8 Science – Chapter 3
Synthetic Fibres and Plastics
Step 5: Biodegradable and Non-Biodegradable Materials

---

What are Biodegradable Materials?

Biodegradable materials are substances that can be broken down naturally by microorganisms like bacteria and fungi.

Examples:

• Vegetable waste
• Paper
• Leaves
• Wood
• Cotton cloth

What are Non-Biodegradable Materials?

Non-biodegradable materials do not decompose naturally and remain in the environment for a very long time.

Examples:

• Plastic
• Polythene bags
• Glass
• Metal cans
• Synthetic fibres

Comparison Table

Biodegradable	Non-Biodegradable
Decompose naturally	Do not decompose
Eco-friendly	Cause pollution
Short life in nature	Remain for many years

Why Should We Avoid Non-Biodegradable Waste?

• Pollutes soil, water, and air
• Harms animals and plants
• Clogs drainage systems
• Creates long-term environmental problems

---

🌍 Choose Biodegradable – Protect Nature