Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What happens during a decomposition reaction?

1. Two compounds combine to form a new compound

2. A compound is formed from its elements

3. A compound breaks down into its individual components

4. An exchange of ions occurs between compounds

The correct answer is: A compound breaks down into its individual components

During a decomposition reaction, a compound undergoes a process in which it breaks down into its simpler substances or individual components. This can involve the separation of a molecule into its constituent elements or simpler compounds through various means, such as heat, light, or electricity. A classic example of this is the decomposition of water (H₂O) into hydrogen (H₂) and oxygen (O₂) gases through electrolysis. The other options represent different types of chemical reactions: the combination of two compounds to form a new compound describes a synthesis reaction; a compound being formed from its elements depicts another synthesis process; and the exchange of ions between compounds is characteristic of a double displacement reaction. Understanding these distinctions is important for identifying and classifying chemical reactions accurately.