Substances, elements, compounds and mixtures
Chemical composition and spatial uniformity describe different features of matter.
Key knowledge
An element contains atoms of one atomic number; a compound combines elements chemically. A pure substance is one chemical substance, whereas a mixture contains multiple substances. A homogeneous mixture is uniform at the specified observation scale; a heterogeneous mixture is not. A solution can therefore look uniform without being a pure substance.
Conditions and scope
- Introductory classification of ordinary materials; specify sample, phase and observation scale.
- A phase label alone does not establish chemical purity. Variable-composition solids need more detailed composition models.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Paul Flowers, Klaus Theopold, Richard Langley and William R. Robinson · OpenStax/Rice University2 sources
- Chemistry 2e (2019), §1.2 Phases and classification of matterPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson · OpenStax/Rice UniversityTextbook chapter
- Chemistry 2e (2019), §2.3 Atomic structure and symbolismPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson · OpenStax/Rice UniversityTextbook chapter
Evidence and review
Inspected §1.2 classification paragraphs on pure substances, elements, compounds and homogeneous/heterogeneous mixtures, and §2.3's explicit proton-count/atomic-number definition of an element. Retains composition and uniformity distinctions; excludes unconditional claims of identical properties without specifying conditions and the adjacent overbroad electron-count inference for ions.
2026-10-10 · Independent Mathematics and Information editor (/root/core_math_information). Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
Permanent link to this entry ↗- Record identity
- foundation-chem-substances-mixtures
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions