Lab: Physical and Chemical Changes

Question 11 • *26-27 CFISD TX-Chemistry A CR

Which answer below correctly identifies the type of change and the explanation when potassium iodide and lead nitrate are mixed?

Answer

physical change because the observation of a solid forming is evidence of a state change, which is reversible

physical change because even though the mixture had a color that was different from either of the two solids alone, each solid’s physical properties remained exactly the same

chemical change because two substances were mixed, which always results in the formation of a new substance

chemical change because both a color change and a solid formation were observed, which provide strong evidence of a new substance

Explanation

When potassium iodide and lead nitrate are mixed, they react to form lead iodide, a new yellow solid, and potassium nitrate. The color change and formation of a solid (a precipitate) are strong evidence of a chemical change. A solid forming here is not merely a reversible state change, as choice A suggests.

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