Which one of the following is not a characteristic of a compound?

A compound is a pure substance formed when two or more elements combine chemically in a fixed ratio [2]. Unlike mixtures, which have variable compositions, compounds have a constant and definite chemical composition. Because the elements in a compound are chemically bonded, they cannot be separated by simple physical methods like filtration or evaporation; instead, chemical reactions are required to break these bonds [2]. Furthermore, a compound is considered a pure substance because all its constituent particles (molecules or formula units) are identical and behave the same way [1]. While the particles of a compound contain two or more different types of atoms, the substance itself is homogeneous and possesses unique properties distinct from its constituent elements [3]. Therefore, the statement that composition is variable is incorrect for a compound, as it describes a characteristic of a mixture [2].

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > Snapshots > p. 130
2. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > 8.3.2 Compounds > p. 124
3. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > Snapshots > p. 131