What is Synthetic Fibres and Plastics Class 8: Definition & Uses

Understanding What Synthetic Fibres and Plastics Are

Synthetic fibres are fibres made by humans through chemical processes, unlike natural fibres that come from plants or animals. These fibres are created by joining many small molecules called monomers to form long chains known as polymers. Plastics are also polymers but are shaped into solid materials used for making various products.

In Class 8 NCERT Science, synthetic fibres and plastics are introduced to help students understand their importance and widespread use. These materials are preferred for their durability, flexibility, and resistance to water and chemicals.

Key points:

• Synthetic fibres are artificial and made from chemicals.
• Plastics are synthetic materials made from polymers.
• Both are widely used in textiles, packaging, and household items.

Types of Synthetic Fibres and Their Characteristics

Synthetic fibres are classified based on their chemical composition and properties. The common types studied in Class 8 include:

• Nylon: Strong, elastic, and resistant to abrasion. Used in ropes, parachutes, and clothing.
• Polyester: Durable, wrinkle-resistant, and quick-drying. Used in garments and home furnishings.
• Acrylic: Soft and warm, used as a wool substitute in sweaters and blankets.

Each fibre has unique features making them suitable for specific uses. For example, nylon is strong and elastic, making it ideal for tires and fishing nets.

These fibres are produced by polymerisation, where monomers join to form long chains.

What Are Plastics? Types and Uses Explained

Plastics are synthetic materials made from polymers that can be moulded into different shapes. They are lightweight, durable, and resistant to water and chemicals. Plastics are classified into two main types:

• Thermoplastics: These soften on heating and can be remoulded multiple times. Examples include polythene and PVC.
• Thermosetting plastics: These harden permanently after heating and cannot be remoulded. Examples include bakelite and melamine.

Common uses of plastics:

• Packaging materials like bottles and bags
• Household items such as containers and furniture
• Electrical insulation and toys

The ability to recycle thermoplastics helps reduce environmental impact.

Differences Between Natural and Synthetic Fibres

Understanding the difference between natural and synthetic fibres is important for Class 8 students:

Natural fibres are biodegradable, whereas synthetic fibres take longer to decompose.

How Synthetic Fibres and Plastics Impact Daily Life

Synthetic fibres and plastics have transformed modern life by providing affordable, durable materials. Some examples include:

• Clothing made from polyester and nylon
• Plastic containers and packaging
• Electrical insulation and automotive parts
• Household items like furniture and toys

Their resistance to water and chemicals makes them ideal for many uses. However, improper disposal of plastics can harm the environment, so recycling and responsible use are encouraged.

Worked example: If a nylon rope stretches by 5% under a load, and its original length is 2 metres, the stretched length is:

$$ \text{Stretched length} = 2 + (5\% \times 2) = 2 + 0.1 = 2.1 \text{ metres} $$

Summary and Exam Tips for Class 8 NCERT Chapter

To prepare well for exams on synthetic fibres and plastics, remember:

• Define synthetic fibres and plastics clearly.
• Know types and examples of synthetic fibres and plastics.
• Understand differences between natural and synthetic fibres.
• Learn properties and common uses.
• Use diagrams and tables to explain concepts.

Practice questions on identifying materials and their properties to score well. Focus on key terms like polymer, monomer, thermoplastics, and thermosetting plastics.