Substances that can be decomposed into elements by chemical means are known as...

• A. Elements
• B. Mixtures
• C. Solutions
• D. Compounds

Answer: (D)

Decomposability into the elements by chemical means identifies a compound. Elements themselves cannot be broken down chemically, and mixtures or solutions are just physical blends whose components aren’t held together by chemical bonds, so they can be separated without chemical reactions. A compound, by contrast, is formed from two or more elements bonded together in fixed proportions and can be decomposed into its constituent elements through chemical changes. Water, for example, can be split into hydrogen and oxygen, and table salt can be decomposed into sodium and chlorine under the right conditions.