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gsenviro eNotes educator| Certified Educator

Reactants and products: these terms are commonly used in relation to chemical reactions, where some chemicals undergo chemical reaction and form new chemical species. The chemical species that undergo reaction are termed as the reactants and the chemicals that are formed are called products. In a chemical reaction, reactants are consumed, while the products are generated. 

We can understand reactants and products with an example, say photosynthesis.

`6CO_2 + 6H_2O + sunlight -> C_6H_12O_6 + 6 O_2`

In this reaction, the reactants are carbon dioxide, water and sunlight; while the products are glucose and oxygen. 

In order to figure out what the reactants and products are in a chemical reaction, one has to first find out the direction of reaction, whether the reaction is going forward or backward. The components being consumed or decreasing in concentration are the reactants and the components whose concentration is increasing are the products of that reaction.

Hope this helps.