Pure iron is too soft for many uses.
Explain why mixing iron with other metals makes alloys which are harder than pure iron.

**Pure Iron:** In a pure metal like iron, all the atoms are the same size. They are arranged in a regular, repeating pattern, forming layers. These layers can easily slide over one another when a force is applied, which makes the pure metal relatively soft and malleable. **Alloys:** An alloy is a mixture of a metal with at least one other element (often another metal). For example, steel is an alloy of iron and carbon. The atoms of the other element(s) have a different size from the iron atoms. When introduced into the iron lattice, these different-sized atoms disrupt the regular arrangement of the layers. This distortion makes it much more difficult for the layers to slide past each other. As a result, a greater force is needed to deform the material, making the alloy harder and stronger than the pure metal.