What is it called when a chemical changes its state but not its composition?

When a chemical changes its state but not its composition, this process is identified as a physical change. During a physical change, the structure of the substance may alter—such as when ice melts into water or when steam condenses back into liquid water—but the actual chemical makeup of the substance remains the same.

For example, water can exist in three states: solid (ice), liquid (water), and gas (steam). Despite changing from one state to another, the molecular structure H2O does not change. This characteristic distinguishes physical changes from chemical changes, in which the arrangement of atoms and the chemical bonds between them are altered, resulting in new substances being formed.

Understanding this concept is crucial in Esthetics, particularly when considering the various treatments and products used in skincare that involve changing states, like in the use of waxes or gels in hair removal or the application of water-based products that may evaporate.