Change of odor. Change of color (for example, silver to reddish - brown when iron rusts). Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat. Change of composition - paper turning to ash when burned. Light and / or heat given off. Formation of gases, often appearing as bubbles in liquids. Formation of a precipitate (insoluble particles). The decomposition of organic matter (for example, rotting food). The change is difficult or impossible to reverse.
list three types of evidence that indicate a chemical reaction
Change of odor Change of color Change in temperature or energy