If attempts to decompose a substance prove unsuccessful, the substance is probably?

• A. A liquid
• B. An element
• C. A compound
• D. A mixture

Answer: (B)

Decomposition attempts test whether a substance can be broken into simpler substances by chemical reactions. Elements are the simplest substances and cannot be decomposed into anything simpler by chemical means. If your attempts to decompose fail, the material is most likely an element because nothing chemically simpler exists for it to become.

State of matter (being a liquid) doesn’t determine decomposability, and a compound would be expected to break down into elements or simpler compounds under the right conditions. A mixture can be separated into its components by physical methods without chemical change. So the failure to decompose points to it being an element.