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.

ThoughtCo.

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 only of one type of atom, molecule, or compound. In other disciplines, the definition extends to homogeneous mixtures.

Key Takeaways: 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.

Here are 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 which are chemical elements. All elements are pure substances. Sugar, salt, and baking soda are pure substances which are compounds. Examples of pure substances which 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 which 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!