Final answer:
A precipitate is evidence for a chemical reaction because it is a solid product that forms from a reaction and settles out of a liquid solution. It indicates that a chemical reaction has taken place. For example, when a colorless solution of lead (II) nitrate is mixed with a colorless solution of potassium iodide, a yellow solid precipitate called lead iodide is instantly formed. This color change and formation of a precipitate are visual clues that a chemical reaction has occurred.
Step-by-step explanation:
A precipitate is evidence for a chemical reaction because it is a solid product that forms from a reaction and settles out of a liquid solution. It indicates that a chemical reaction has taken place. For example, when a colorless solution of lead (II) nitrate is mixed with a colorless solution of potassium iodide, a yellow solid precipitate called lead iodide is instantly formed. This color change and formation of a precipitate are visual clues that a chemical reaction has occurred.