Complete the sentence.
In this chemical reaction, carbon dioxide is a ().

 - product
 - reactant
Read the underlined text carefully. Look for information about what happens to carbon dioxide in this chemical reaction.
Plants make glucose, a sugar they can use for food, through a process called photosynthesis. During photosynthesis, plants use energy from sunlight to make glucose from water and carbon dioxide. In the process of making glucose, plants also create most of the oxygen in the air we breathe.
The underlined text tells you that when water and carbon dioxide combine, glucose and oxygen are formed. When water and carbon dioxide react, or go through a chemical change, their atoms are rearranged to form glucose and oxygen. Because carbon dioxide reacts in this chemical reaction, carbon dioxide is a reactant.