 When a substance bubbles it may be a clue that a chemical reaction is taking place.

 Precipitate- a solid that forms during a chemical reaction of two solutions

 When mixing chemicals the product is a different color than the reactants

 Can give off light or change temperatures  Endothermic- energy is absorbed or the product is colder than the reactant  Exothermic-energy is released or the product is warmer than the reactant

The only definitive evidence is the formation of a new substance