Questions of Mixed Changes - Questions at the end of the chapter - Chapter 5 Class 7 - Changes Around Us: Physical and Chemical (Curiosit

Last updated at April 25, 2026 by

Q3 (Medium): State whether True or False: (i) Melting of wax is necessary for burning a candle. (ii) Collecting water vapour by condensing involves a chemical change. (iii) The process of converting leaves into compost is a chemical change. (iv) Mixing baking soda with lemon juice is a chemical change.

Answer:
We have studied that candle burning involves both physical and chemical changes and decomposition forms new substances . This is why we can identify each statement.

  • (i) True - wax must melt first
  • (ii) False - condensation is physical change
  • (iii) True - decomposition forms new substances
  • (iv) True - carbon dioxide gas forms
True vs False Statements Reason True Statements False Statements Wax melting needed Physical change first Water condensing Composting New substances form Baking soda + lemon CO₂ gas produced
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