What Are Examples of Pure Substances?

Definition and Examples of a Pure Substance

In chemistry, a pure substance has a homogeneous chemical composition.
In chemistry, a pure substance has a homogeneous chemical composition.

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By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on January 30, 2020

A pure substance or chemical substance is a material that has a constant composition (is homogeneous) and has consistent properties throughout the sample. A pure substance participates in a chemical reaction to form predictable products. In chemistry, a pure substance consists of only one type of atom, molecule, or compound. In other disciplines, the definition extends to homogeneous mixtures.

Pure Substance Examples

  • In chemistry, a substance is pure if it has a homogeneous chemical composition. At the nanoscale, this only applies to a substance made up of one type of atom, molecule, or compound.
  • In the more general sense, a pure substance is any homogeneous mixture. That is, it is matter that appears uniform in appearance and composition, no matter how small the sample size.
  • Examples of pure substances include iron, steel, and water. Air is a homogeneous mixture that is often considered to be a pure substance.

Examples of Pure Substances

Examples of pure substances include tin, sulfur, diamond, water, pure sugar (sucrose), table salt (sodium chloride) and baking soda (sodium bicarbonate). Crystals, in general, are pure substances.

Tin, sulfur, and diamond are examples of pure substances that are chemical elements. All elements are pure substances. Sugar, salt, and baking soda are pure substances that are compounds. Examples of pure substances that are crystals include salt, diamond, protein crystals, and copper sulfate crystals.

Depending on who you talk to, homogeneous mixtures may be considered examples of pure substances. Examples of homogeneous mixtures include vegetable oil, honey, and air. While these substances contain multiple types of molecules, their composition is consistent throughout a sample. If you add soot to air, it ceases to be a pure substance. Contaminants in water make it impure.

Heterogeneous mixtures are not pure substances. Examples of materials that are not pure substances include gravel, your computer, a mixture of salt and sugar, and a tree.

Tip for Recognizing Pure Substances

If you can write a chemical formula for a substance or if it is a pure element, it is a pure substance!

Sources

  • Hill, J. W.; Petrucci, R. H.; McCreary, T. W.; Perry, S. S. (2005). General Chemistry (4th ed.). Pearson Prentice Hall. New Jersey.
  • IUPAC (1997). "Chemical Substance." Compendium of Chemical Terminology (2nd ed.) doi:10.1351/goldbook.C01039
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Helmenstine, Anne Marie, Ph.D. "What Are Examples of Pure Substances?" ThoughtCo, Aug. 27, 2020, thoughtco.com/examples-of-pure-substances-608350. Helmenstine, Anne Marie, Ph.D. (2020, August 27). What Are Examples of Pure Substances? Retrieved from https://www.thoughtco.com/examples-of-pure-substances-608350 Helmenstine, Anne Marie, Ph.D. "What Are Examples of Pure Substances?" ThoughtCo. https://www.thoughtco.com/examples-of-pure-substances-608350 (accessed April 19, 2024).