Phase behavior refers to how different states of matter—such as solids, liquids, and gases—interact and change under varying conditions of temperature and pressure. It helps scientists understand how substances transition between these states, which is crucial in fields like chemistry and materials science. In many systems, phase behavior can be represented using phase diagrams, which visually depict the conditions under which different phases coexist. These diagrams are essential for studying mixtures, such as oil and water, and can inform processes in industries like petroleum and pharmaceuticals.