Evidences of chemical change

  • formation of gas
  • formation of a precipitate (insoluble solid)
  • unexpected change in color
  • unexpected change in odor
  • release of heat energy
  • release of light
  • production of sound
  • unexpected change in temperature
  • absorption or release of electrical energy

Pure substances are composed of the same kind of matter, they are either elements or compounds.


A chemical change is a change in which the composition of the substance is altered.


Chemical Reactions