Class 7 Science Chapter 5, Changes Around Us: Physical and Chemical, explores why melting ice, folding paper, ripening bananas, rusting iron and burning magnesium behave differently, distinguishing physical changes from chemical changes and reversible changes from irreversible ones.
What Class 7 Science Chapter 5 Covers
5.1–5.2 Physical vs Chemical Changes contrasts changes where only shape, size or state changes without forming a new substance (5.1) against chemical changes where one or more new substances form, such as lime water turning milky with carbon dioxide or vinegar reacting with baking soda (5.2).
5.3–5.4 Rusting, Combustion & Combined Changes examines rusting (5.3.1), combustion and the fire triangle of fuel, oxygen and ignition temperature (5.3.2), and processes like a burning candle where both physical (melting wax) and chemical (burning wax vapour) changes occur together (5.4).
5.5–5.7 Reversible/Irreversible, Desirable/Undesirable & Slow Natural Changes compares reversible and irreversible changes (5.5), desirable vs undesirable changes (5.6), and slow geological changes like weathering of rocks (5.7.1) and soil erosion (5.7.2).
Exercises in Chapter 5
- In a Nutshell key points summary and Let Us Enhance Our Learning chapter exercises.
- Exploratory Projects and Dive Deeper hands-on science activities.
Read Class 7 Science Chapter 5 Online
More Chapters
- Previous: Chapter 4: The World of Metals and Non-metals
- Next: Chapter 6: Adolescence: A Stage of Growth and Change
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FAQ
Why is burning a candle both a physical and a chemical change?
Melting and solidification of wax is a physical change because no new substance is formed, whereas burning of wax vapour with a flame produces carbon dioxide and water vapour, which is a chemical change.
Why does lime water turn milky when carbon dioxide is passed through it?
Carbon dioxide reacts with calcium hydroxide (lime water) to form calcium carbonate, an insoluble white substance that makes the solution look milky.