This lesson defines reactants within chemical reactions and how reactants are written in chemical reactions. read more
In this reaction, all reactants and products are invisible. The heat being evolved is the clue that tells you a reaction is taking place. This is a good example of an exothermic reaction, a reaction in which heat is given off. A lot of reactions are exothermic. Some reactions, however, absorb energy rather than release it. read more
Another example of a reactant is found in the equation 2 H 2 O → 2 H 2 + O 2 where water produces both oxygen and hydrogen gas. In this reaction, the reactant is H 2 O, the water, and the products are the gases H 2 and O 2. read more