Which answer below correctly identifies the type of change and the explanation when potassium iodide and lead nitrate are mixed?
a. physical change because the observation of a solid forming is evidence of a state change, which is reversible
b. 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
c. chemical change because two substances were mixed, which always results in the formation of a new substance
d. chemical change because both a color change and a solid formation were observed, which provide strong evidence of a new substance