Single correct option
Which one of the following is a chemical change?
- A. Melting of wax
- B. Burning of magnesium ribbon in air
- C. Dissolving sugar in water
- D. Evaporation of alcohol
Show answer and solution
Answer: (B) Burning of magnesium ribbon in air
A chemical change forms new substances with different properties. Burning magnesium forms white magnesium oxide, and the change cannot be reversed by simple means. Melting wax, dissolving sugar and evaporating alcohol are physical changes, as no new substance forms and the original can be recovered by cooling or evaporation. Colour and light emission are clues for chemical change.
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