* Pure substances have a fixed chemical composition and properties. Examples include elements like gold or oxygen, and compounds like water (H₂O).

* Mixtures are combinations of two or more substances that are not chemically bonded. The components of a mixture can be separated using physical methods.

Steel is made by combining iron with other elements like carbon, manganese, chromium, etc. These elements are not chemically bonded in a fixed ratio, and the proportions can vary depending on the type of steel.

Therefore, steel is a mixture of different elements.