When iron is heated, it doesn't form a new substance, but rather undergoes a change in state.

Here's what happens:

* Solid Iron: At room temperature, iron is a solid metal.

* Heating: As you heat iron, its temperature increases.

* Melting Point: When the iron reaches its melting point (around 1538°C or 2800°F), it transitions from a solid to a liquid state. This liquid iron is still chemically the same iron, just in a different form.

* Boiling Point: If you continue to heat the liquid iron, it will eventually reach its boiling point (around 2750°C or 4982°F) and become a gas. Again, this is still iron, just in a gaseous state.

So, the substance formed when iron is heated is still iron, but it changes its state from solid to liquid (molten iron) and then to gas (iron vapor).