Answer:
Color change, production of gas, formation of precipitation
Step-by-step explanation:
Color change: A change in the color of a substance is a clear indication that a chemical reaction has taken place.
Production of gas: The release of a gas during a reaction can indicate a chemical change, especially if the gas produced is not a component of the original substance.
Formation of a precipitate: A precipitate is a solid substance that forms when two liquids are mixed. The formation of a precipitate is a strong indication that a chemical reaction has occurred and that a new substance has been formed