Ch 6 distinguishes between physical changes (no new substance) and chemical changes (new substance formed). Students learn about rusting, galvanisation, and crystallisation as key examples.
Physical change: appearance may change but no new substance forms (tearing paper, melting ice, dissolving sugar). Chemical change: a new substance with different properties forms (burning, rusting, cooking). Signs of chemical change: colour change, gas production, heat/light, precipitate.
Rusting: iron + oxygen + moisture → iron oxide (rust). Rust is brown, flaky, and weakens iron. Prevention: painting, oiling, galvanisation (coating with zinc), making alloys (stainless steel = iron + chromium + nickel).
Download: https://ncert.nic.in/textbook/pdf/gesc106.pdf | Complete book: https://ncert.nic.in/textbook/pdf/gesc1ps.zip
It is both. Melting of wax is a physical change (wax changes state). Burning of the wick and wax vapour is a chemical change (produces CO₂, water vapour, heat, and light — new substances are formed).
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