A chemical substance is defined as any form of matter that possesses a fixed, characteristic chemical composition and uniform properties. In chemistry, substances are broadly classified into elements and compounds, which differ from mixtures. Elements represent the simplest components of matter, consisting of atoms that cannot be broken down into simpler chemical constituents by conventional means. Conversely, compounds are chemical substances formed when two or more elements are chemically bonded together in a definite proportion. The properties of a substance are dictated by the arrangement and bonding of its constituent atoms, and the study of these interactions allows for the understanding of how substances react and transform into new chemical forms.