What happens to steel when it is heated?

When steel is heated, it undergoes a physical change where its molecules gain energy and move apart from each other. This process results in thermal expansion, causing the steel to elongate. As temperature increases, the molecular vibrations create more space between the atoms, which is why heating a metal like steel typically leads to an increase in size and volume. This phenomenon is important in various applications, including construction and firefighting, as it affects the integrity and behavior of structures during high-temperature events, such as fires. Understanding this principle is crucial for firefighters and engineers when assessing material performance in extreme conditions.