A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Chemical reactions must be distinguished from physical changes. If a physical change occurs, the physical properties of a substance will change, but its chemical identity will remain the same.

A chemical change occurs when the substance's composition is changed. When bonds are broken and new ones are formed a chemical change occurs. The following are indicators of chemical changes:

-Change in temperature

-Change in color

-Noticeable odor (after reaction has begun)

-Formation of a precipitate

-Formation of bubbles

The shape of an object can be changed and the object will still remain true to its chemical composition. For example, if one were to fold money the money is still chemically the same.

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