A compound is a pure substance made up of two or more elements.
Properties of pure substances
- A substance with a fixed chemical composition is called a pure substance, such as water, air, and nitrogen.
- A pure substance does not have to be of a single element or compound.
- A pure substance may exist in different phases. There are three principal phases solid, liquid, and gas.
- Pure substances have a sharply defined (one temperature) melting or boiling point. Impure substances have a temperature range over which they melt or boil.