Synthetic Fibres and Plastics Class 8 Questions Answers for Science

What Are Synthetic Fibres and Plastics?

Synthetic fibres are man-made fibres produced from chemical substances, mainly derived from petroleum products. Unlike natural fibres such as cotton or wool, synthetic fibres are created through chemical processes in factories. Common synthetic fibres include nylon, polyester, and acrylic.

Plastics are also synthetic materials made up of long chains of molecules called polymers. They can be moulded into various shapes when heated and are widely used in everyday items like containers, toys, and packaging.

Understanding these materials helps Class 8 students grasp how modern materials are developed and their applications in daily life.

Types of Synthetic Fibres and Their Uses

Synthetic fibres are classified based on their chemical composition and properties. Here are some common types:

• Nylon: Strong and elastic, used in making ropes, parachutes, and clothes.
• Polyester: Durable and wrinkle-resistant, commonly used in garments and home furnishings.
• Acrylic: Soft and warm, often used as a wool substitute in sweaters and blankets.

Uses of Synthetic Fibres

• Clothing and fashion industry
• Carpets and upholstery
• Industrial applications like tyre cords and seat belts

These fibres are preferred for their strength, durability, and resistance to wrinkles and shrinking.

Understanding Plastics: Thermoplastics vs Thermosetting Plastics

Plastics are broadly divided into two categories:

Thermoplastics are flexible and recyclable, making them useful for packaging films and containers. Thermosetting plastics are hard and heat-resistant, ideal for electrical switches and kitchenware.

Knowing these differences helps students understand material selection in manufacturing.

How Synthetic Fibres and Plastics Are Made

Synthetic fibres are made through a chemical process called polymerisation, where small molecules called monomers join to form long chains called polymers.

For example, nylon is made by combining hexamethylenediamine and adipic acid:

$$\text{Hexamethylenediamine} + \text{Adipic acid} \rightarrow \text{Nylon polymer}$$

Plastics are also formed by polymerisation of monomers like ethylene (for polythene) or vinyl chloride (for PVC). These processes happen in factories under controlled conditions.

Understanding these chemical processes is important for Class 8 Science students to connect theory with real-world manufacturing.

Advantages and Disadvantages of Synthetic Fibres and Plastics

Advantages

• Synthetic fibres are strong, durable, and resistant to insects.
• Plastics are lightweight, waterproof, and versatile.
• Both materials are cost-effective and widely available.

Disadvantages

• Synthetic fibres are not biodegradable and can cause environmental pollution.
• Plastics contribute significantly to waste and take hundreds of years to decompose.
• Some plastics release harmful chemicals if burnt.

Comparison Table

Awareness about pros and cons helps students appreciate sustainable use.

Important NCERT Questions and Answers for Practice

Here are some important synthetic fibres and plastics class 8 questions answers to help you prepare:

Q1: What is the main difference between natural and synthetic fibres?

• Natural fibres come from plants or animals; synthetic fibres are man-made from chemicals.

Q2: Name two thermoplastic and two thermosetting plastics.

• Thermoplastics: Polythene, PVC
• Thermosetting plastics: Bakelite, Melamine

Q3: Why are synthetic fibres preferred over natural fibres in some cases?

• They are stronger, more durable, and resistant to wrinkles and insects.

Q4: Write a chemical equation for making nylon.

• Hexamethylenediamine + Adipic acid → Nylon polymer

Practice these to strengthen your understanding and score well in exams.