Reaction Definition

Definition of Reaction

A chemical reaction changes substances into new materials.
A chemical reaction changes substances into new materials. Paper Boat Creative, Getty Images
Reaction Definition: A reaction or chemical reaction is a chemical change which forms new substances.

Reaction Examples: The chemical reaction H 2(g) + ½ O 2(g) → H 2O(l) describes the formation of water from its elements.

Also Known As: Chemical Reaction, Chemical Change

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