A chemical reaction is a process in which some substances change into different substances. Substances that start a chemical reaction are called reactants. Substances that are produced in the reaction are called products. Reactants and products can be elements or compounds. Bonds break in the reactants and new bonds form in the products. The reactants and products contain the same atoms, but they are rearranged during the reaction. As a result, the atoms are in different combinations in the products than they were in the reactants.

1. What is a chemical reaction?

2. What starts a chemical reaction?

3. What is the end of a chemical reaction?

4. Compare and contrast reactants and products. (2 sentences)