Short answer
A compound is a pure substance made from chemically bonded elements in a defined composition, such as water. A mixture contains two or more substances physically combined in proportions that can vary, such as salt water. A mixture may itself contain compounds. 1 2
A compound is one chemical substance with bonded elements; a mixture contains multiple substances together without making one new substance throughout.
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At a glance
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| Question | Compound | Mixture |
|---|---|---|
| Composition | Defined by chemical formula | Variable proportions |
| Components joined by | Chemical bonding within substance | Physical combination of substances |
| Typical separation | Chemical change needed | Often physical method works |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Compound. A pure substance whose atoms of two or more elements are chemically bonded in a defined composition. 1
Mixture. A physical combination of two or more substances with variable proportions. 1
Key differences
Water remains H₂O wherever a pure sample is taken. Salt water can contain different amounts of salt and water. Mixtures can be homogeneous, like a solution, or heterogeneous, like sand in water. 1 2
How to tell them apart
Ask whether there is one substance with a reproducible chemical formula or several substances retaining their identities. Evaporation can separate salt from salt water; it cannot separate hydrogen and oxygen from water without chemical change. 1 2
Where they overlap
Many mixtures include compounds, and some compounds are dissolved in other compounds. Both can look uniform to the eye. 1 2
Edge cases
Alloys and nonstoichiometric materials complicate a classroom rule that every material has a simple integer formula. A mixture’s components may interact without forming one new compound. 1 2
Why the distinction exists
The categories distinguish chemical identity from sample composition, guiding how substances are analyzed and separated. 1 2
Common misconceptions
A mixture is not necessarily visibly uneven; air and salt water are uniform mixtures. 1 2
Examples
Pure sodium chloride is a compound. Table salt containing additives is a mixture of substances. 1 2
Sources
Sources checked October 3, 2026.
- OpenStax — Phases and Classification of Matter. Elements and compounds.
- OpenStax — Molecular and Ionic Compounds. Ions and ionic compounds.