CBSE Class 8 Science Exemplar Chapter 3: Synthetic Fibres and Plastics NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

CBSE Class 8 Science Chapter 3 introduces synthetic fibres and plastics, materials integral to our modern world. This chapter explores the distinctions between natural and man-made fibres, detailing the characteristics and applications of common synthetic materials such as rayon, nylon, and polyester. It also covers the classification of plastics into two main categories: thermoplastics and thermosetting plastics, explaining their unique properties and uses. The solutions provide clear, step-by-step explanations to help students understand the formation, properties, and environmental impact of these materials. By breaking down complex ideas into manageable parts, these resources enhance comprehension and solidify knowledge, offering a comprehensive guide for students to master the concepts of synthetic fibres and plastics for their academic success.

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Quick info

BoardCBSE
ClassClass 8
SubjectScience Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 3

Chapter summary

Chapter 3 of the Class 8 Science Exemplar focuses on Synthetic Fibres and Plastics. The NCERT Solutions cover multiple-choice questions that test students' understanding of identifying synthetic fibres, sources of materials like rayon, and properties of plastics. It clarifies the distinction between natural and synthetic sources, the characteristics of thermosetting plastics, and the suitability of materials for specific applications like cooking utensil handles.

Learning outcomes

  • Identify synthetic fibres from natural ones.
  • Understand the sources and properties of synthetic fibres like rayon and nylon.
  • Differentiate between thermosetting and thermoplastic plastics.
  • Recognize the applications of different synthetic materials based on their properties.
  • Explain why certain materials are suitable for specific uses, such as cooking utensil handles.

Topics covered

Paper topics

  • Synthetic Fibres
  • Plastics
  • Nylon
  • Rayon
  • Polyester
  • Cotton
  • Wool
  • Jute
  • Thermosetting Plastics
  • Thermoplastics
  • Material Properties
  • Applications of Materials

Important topics

  • Identification of Synthetic Fibres
  • Source of Rayon
  • Thermosetting vs. Thermoplastic Plastics
  • Properties and Uses of Bakelite
  • Blended Fabrics (Polycot)

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Questions and Solutions

Question 1

Pick the synthetic fibre out of the following options: Cotton, Nylon, Jute, Wool.
Solution: The correct option is (b) Nylon.

Explanation: Natural fibres are obtained from plants or animals. Cotton and jute are plant-based fibres, while wool is an animal-based fibre. Nylon, on the other hand, is a man-made fibre, which means it is synthetic.

Question 2

Which of the following is a source of rayon? Options are: Wool, PET, Wood pulp, Silk.
Solution: The correct option is (c) Wood pulp.

Explanation: Rayon is a versatile fibre that is manufactured from a natural source, specifically wood pulp, through a chemical process. It is often referred to as a semi-synthetic fibre.

Question 3

Polycot is obtained by mixing which of the following materials? Options are: nylon and wool, polyester and wool, nylon and cotton, polyester and cotton.
Solution: The correct option is (d) polyester and cotton.

Explanation: Polycot is a blended fabric created by combining polyester fibres with cotton fibres. This mixture leverages the desirable properties of both materials, such as durability from polyester and comfort from cotton.

Question 4

Which of the following is a thermosetting plastic? Options are: Melamine, Polythene, PVC, Nylon.
Solution: The correct option is (a) Melamine.

Explanation: Thermosetting plastics are polymers that irreversibly harden when heated. Melamine is a thermosetting plastic, meaning it cannot be softened by reheating once moulded. Polythene, PVC, and Nylon are examples of thermoplastics, which can be softened and reshaped by heating.

Question 5

The material that is similar to silk in appearance is: Nylon, Rayon, Polyester, Terylene.
Solution: The correct option is (b) Rayon.

Explanation: Rayon is a manufactured fibre known for its lustrous appearance and soft texture, which closely resembles that of silk. It is produced from wood pulp and is often more affordable than natural silk.

Question 6

The most suitable material for the preparation of handles of cooking utensils is: Polythene, PVC, Nylon, Bakelite.
Solution: The correct option is (d) Bakelite.

Explanation: Bakelite is a thermosetting plastic that possesses excellent heat-insulating properties and does not soften upon heating. These characteristics make it an ideal material for manufacturing the handles of cooking utensils, ensuring safety and durability.

Common mistakes

  • Confusing natural fibres (cotton, wool, jute) with synthetic ones (nylon, rayon).
  • Incorrectly identifying the source material for synthetic fibres like rayon.
  • Misclassifying plastics as either thermosetting or thermoplastic.
  • Selecting inappropriate materials for applications due to a lack of understanding of their properties.

Revision tips

  • Create flashcards to remember the names and properties of different synthetic fibres and plastics.
  • Draw diagrams to illustrate the differences between thermosetting and thermoplastic materials.
  • Practice identifying the correct material for specific uses based on heat resistance and malleability.
  • Review the explanations for each question to understand the reasoning behind the correct answers.

Practice MCQs

Q1. Which of the following is classified as a synthetic fibre?

Q2. Rayon, a fibre that resembles silk, is primarily derived from which source?

Q3. The fabric 'Polycot' is a blend created by mixing which two materials?

Q4. Which of the following plastics is an example of a thermosetting plastic?

Q5. Which material is most suitable for making the handles of cooking utensils due to its properties?

Frequently asked questions

What is the main difference between synthetic and natural fibres?

Natural fibres are derived from plants (like cotton, jute) or animals (like wool, silk), while synthetic fibres are man-made through chemical processes (like nylon, rayon, polyester).

What is rayon and where does it come from?

Rayon is a semi-synthetic fibre that is produced by the chemical treatment of wood pulp. It is known for its silk-like appearance.

Can you give an example of a thermosetting plastic?

Yes, Melamine and Bakelite are examples of thermosetting plastics. They undergo irreversible changes upon heating.

Why is bakelite used for making handles of cooking utensils?

Bakelite is used because it is a bad conductor of heat, meaning it doesn't transfer heat easily, and it does not soften when heated, making it safe to handle.

What does 'Polycot' refer to?

Polycot is a fabric made by mixing polyester and cotton fibres, combining the benefits of both materials.

Important links

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