Webenhanced.lbcc.edu/chemjk/chem2jk/downloads/lab/Demo_lab_604.pdf. Chemical Reactions - Signs of a Reaction. There are a number of observations that indicate a chemical reaction has occurred.
One is the formation of a precipitate. A precipitate is a solid formed in a chemical reaction that is different from either of the reactants. Atlantis.coe.uh.edu/texasipc/units/changes/chemistry.pdf.