Classifying Changes

• Practice classifying everyday processes as physical or chemical.
• Some processes involve both — candle burning (wax melts + burns).
• Ripening fruit — chemical (starch to sugars, colour change).
• Making popcorn — physical burst + chemical browning.
• Fermentation — chemical (idli batter, alcohol in toddy — note responsibly).
• NCERT exercise pairs for exam preparation.

Level 1 — Core idea

1. Melting ice — physical.

2. Burning wood — chemical.

3. Dissolving salt in water — physical.

Level 2 — Process and representation

1. Vinegar + baking soda — chemical (CO₂ gas).

2. Diagram (text) — flowchart: new substance? yes → chemical; no → physical.

3. Souring milk to curd — chemical.

Level 3 — Applications and NCERT links

1. Stretching rubber band — physical (until it snaps — then chemical bonds break).

2. Photosynthesis in plants — chemical (glucose formed).

3. Real world — fireworks: chemical (colour, light, gas).

Classifying ten daily processes

Process list:
1. Cutting apple — physical (expose surface; browning later is chemical oxidation).
2. Cooking rice — chemical ( starch gelatinisation, texture change).
3. Evaporating seawater for salt — physical (salt already present).
4. Iron gate rusting — chemical.
5. Making ice cubes — physical.
6. Digestion of roti — chemical.
7. Crushing ice — physical.
8. Lighting matchstick — chemical.
9. Folding paper boat — physical.
10. Milk going sour — chemical.
Step — For each, ask: new substance with new properties? reversible easily?
Conclusion: systematic questions help classify correctly in exams.

• Classify: melting wax, burning wax.
• Is ripening of mango physical or chemical?
• Give one example that shows both types of change.
• Why is rusting chemical?
• Sort: dissolve sugar, ferment batter, freeze water.
• Classify: making curd, folding paper, burning LPG.

Open the Practice tab for graded questions on Classifying Changes.