Multiple choice

Which of these is not a sign that a reaction has taken place?

  1. The substance catches fire

  2. The substance has changed from a solid to a liquid

  3. A gas is given off

  4. There is an explosion
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A change from solid to liquid is a physical change, specifically melting, not a chemical reaction. Chemical reactions typically involve gas production, color changes, temperature changes, or the formation of a precipitate.

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