Answer: Elements or compounds that enter are Reactants.
The substances that are formed are the Products
Reactants in C6H12O6 + 602 ---> 6CO2 + 6H2O are C₆H₁₂O₆ + 6 O₂
Reactants in 6 CO2 + 6H2O --->C6H12O6 + 602 are 6 CO₂ + 6 H₂O
Reactants in 2 H2 +O2 ---> 2 H2O are 2 H₂ +O₂
Reactants in 2 H2O ---> 2 H2 + O2 are 2 H₂O
Explanation:
The number of atoms in the reactants have to balance with the number of atoms in the products.
The first two examples given are for metabolism of carbohydrates (similar to combustion of hydrocarbons) and photosynthesis.