Chemical reactions bonds between atoms.

break

make and break

make

Chemical reactions occur when chemical bonds between atoms are formed or broken. 

Explanation:

The substances that go into a chemical reaction are called the reactants, and the substances produced at the end of the reaction are known as the products.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

answer carbon and three oxygen atoms;