Which term describes materials that may exist in different physical states?

The term that describes materials which may exist in different physical states is "substances." Substances can exist in various phases such as solid, liquid, or gas, depending on the temperature and pressure conditions. For example, water is a substance that can be found as ice (solid), liquid water, or steam (gas) under different circumstances. This ability to shift between different physical states is a key characteristic of substances.

Mixtures, on the other hand, consist of two or more different substances that are combined but not chemically bonded, and their components retain their individual properties. Compounds are specific types of substances formed when two or more elements chemically combine in a fixed ratio, and they exist in a single physical state at a given temperature and pressure. Elements consist of a single type of atom and typically correspond to their respective physical states rather than transitioning between different states. Thus, "substances" is indeed the correct term for materials that may exist in different physical states.