Question

Which is a pure substance?

air
nitrogen
apple juice
tap water

Answer 1

A pure substance is a material that has a consistent composition and defined properties throughout. Among the options given:

- **Air**: A mixture of gases, primarily nitrogen and oxygen, along with other gases.
- **Nitrogen**: A pure element and a pure substance, since it consists only of nitrogen molecules.
- **Apple juice**: A mixture that contains water, sugars, acids, and other compounds.
- **Tap water**: Generally considered a mixture because it can contain various dissolved minerals and contaminants.

Therefore, the pure substance among the options provided is **nitrogen**.