A compound breaks down into multiple simpler compounds.

• A. Decomposition reactions
• B. Synthesis reactions
• C. Combination reactions
• D. Neutralization reactions

Answer: (A)

Breaking down a compound into simpler substances is the hallmark of a decomposition reaction. In these reactions, one reactant splits to yield two or more products, the opposite of synthesis where several substances combine to form a single compound. Energy input is often required to break bonds, so decomposition processes typically need heat, electricity, or light. For example, heating calcium carbonate gives calcium oxide and carbon dioxide, while hydrogen peroxide can decompose into water and oxygen. The other listed types involve building up substances into a more complex compound or neutralizing an acid and base to form a salt and water, which is not what’s described here. So this scenario is best described as a decomposition reaction.