# Which of These Is a Pure Substance, Not a Mixture?

> Aluminum foil is an example of a pure substance; concrete, salt water, and face powder are mixtures, not pure substances. Texas barber exam answer.

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Last updated: 2026-08-11

**The answer is aluminum foil. It's made up of nothing but aluminum atoms, which is what makes it a pure substance.**

Salt water, concrete, and face powder are all mixtures — each one is made of more than one substance combined together, so their composition can vary. A pure substance has one consistent chemical makeup all the way through, which is exactly what a straight sheet of aluminum foil is.

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