Lesson eLearning

Identify the key indicators that distinguish a chemical change from a physical change. Provide at least three indicators.

hard 5 marks Class 7 · Science · Physical and Chemical Changes
Answer
Color change, gas evolution, formation of precipitate

The correct answer is Color change, gas evolution, formation of precipitate — Thus, colour change, gas evolution and precipitate formation are reliable indicators.

Step-by-step solution

  1. Chemical reactions often show a visible colour change.
  2. Many chemical reactions evolve a gas, e.g., CO₂, H₂.
  3. Some reactions form a solid precipitate, e.g., silver chloride.
  4. Thus, colour change, gas evolution and precipitate formation are reliable indicators.
Common mistake: Overlooking temperature change as the sole indicator

Concept tested: Indicators of chemical change

Published · How this solution was prepared and checked

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