Indicators of a Chemical Reaction (Updated)

A chemical reaction occurs when two or more substances combine, atoms are rearranged, and a new substance is created.

One indicator is the release of gas, which can manifest as fizzing, bubbling, or a change in odor (e.g., baking a cake or a foul smell).

A change in temperature, either getting much hotter or colder, is another sign of a chemical reaction.

The production of energy in the form of light, such as striking a match or an explosion, indicates a chemical reaction.

A permanent change in color, like wood changing from light brown to black when burned, is a fourth indicator.

Finally, the formation of a precipitate, meaning a solid forms or 'falls out' of the solution, is a key indicator.