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Q8 (Medium): Read the story titled 'Eco-friendly Prithvi', and tick the most appropriate option(s).
Answer:
We have studied that
eco-friendly practices
involve
reducing waste
and
choosing reversible changes
over
irreversible ones
. This is why sustainable choices matter.
- Reusable materials show physical changes
- Biodegradable waste undergoes natural chemical changes
- Recycling involves physical processing
- Composting involves beneficial chemical changes
Q9 (Medium): Some changes are given here. Write physical changes in the area marked A and chemical changes in the area marked B. Enter the changes which are both physical and chemical in the area marked C.
Answer:
The changes given are classified as follows:
Area A (Physical Changes Only):
- Tearing paper — shape changes, no new substance forms
- Melting ice — state change (solid → liquid), no new substance
- Folding clothes — shape change only, reversible
Area B (Chemical Changes Only):
- Rusting iron — iron reacts with oxygen and moisture → new substance (iron oxide)
- Curdling milk — proteins change chemically → new substance (curd)
- Ripening fruits — chemical changes produce new flavours and colour
- Burning magnesium ribbon — Mg reacts with O₂ → magnesium oxide (new substance)
- Mixing baking soda with vinegar — acid-base reaction → CO₂ gas produced (new substance)
Area C (Both Physical and Chemical Changes):
- Burning candle — wax melts (physical: liquid wax) and burns (chemical: wax vapour reacts with oxygen → CO₂ + H₂O)
