Which of the following is a characteristic property of compounds?

Compounds are substances formed when two or more elements are chemically bonded together. A defining characteristic of compounds is that they have a fixed composition and distinct properties, which sets them apart from mixtures that can vary in composition and do not have uniform properties.

The fixed composition means that a compound always consists of the same ratio of atoms, regardless of its source or how it's obtained. For example, water (H2O) always has two hydrogen atoms for every one oxygen atom. This consistent atomic arrangement gives compounds their unique chemical and physical properties, such as boiling point, melting point, and reactivity.

This characteristic also indicates that compounds cannot simply be separated into their constituent elements through physical means, as they require chemical reactions to break the bonds between atoms. Thus, the fixed composition and properties of compounds underline their identification in the realm of chemistry.