Question

which of these are signs that a chemical reaction has taken place? select one: change of color production of light change in temperature production of a gas or solid product all of the above

Explanation:

To determine signs of a chemical reaction:

• Color change (e.g., rusting, indicator changes) is a sign.
• Light production (e.g., combustion, bioluminescence) is a sign.
• Temperature change (exothermic/endothermic reactions) is a sign.
• Gas/solid product (precipitate, gas evolution like in acid - metal reactions) is a sign.

Since all these (color change, light production, temperature change, gas/solid product) are signs of a chemical reaction, "All of the above" is correct.

Answer:

All of the above