Ch 3 covers human-made fibres and plastics. Students learn about different synthetic fibres (rayon, nylon, polyester, acrylic), types of plastics, their properties, uses, and the environmental impact.
Polymers: long chains of repeating units. Rayon: made from wood pulp, feels like silk. Nylon: the first fully synthetic fibre — strong, elastic, used in ropes, textiles, toothbrush bristles. Polyester: wrinkle-resistant (PET for bottles, polyester for clothes). Acrylic: resembles wool, used in sweaters and blankets.
Thermoplastic (PVC, polythene): softens on heating, can be remoulded. Thermosetting (bakelite, melamine): once set, cannot be softened again. Plastics are non-biodegradable — take hundreds of years to decompose. Solution: 5R — Reduce, Reuse, Recycle, Recover, Refuse single-use plastics.
Download: https://ncert.nic.in/textbook/pdf/hesc103.pdf | Complete book: https://ncert.nic.in/textbook/pdf/hesc1ps.zip
Burning plastics releases toxic gases (dioxins, furans) that pollute the air and are harmful to health. Some plastics release poisonous hydrogen cyanide gas. Recycling or proper disposal is much safer than burning.
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