When you place a kettle on the stove and boil water, the steam that forms is a result of a physical change. In this process, water is heated and transitions from a liquid state to a gaseous state (steam). This transformation involves an increase in temperature and energy, causing the molecules in the water to move faster and escape into the air as steam.
Importantly, this process does not alter the chemical structure of the water itself; it remains H2O whether it is in liquid form or gaseous form. A chemical change, in contrast, involves a transformation that alters the substance at a molecular level, resulting in the formation of a new substance. Therefore, since boiling water simply changes its state without changing its chemical identity, the steam formed is part of a physical change.