Transformations between states of matter are categorized as:

Transformations between states of matter are indeed categorized as possible because, under the right conditions, matter can easily change from one state to another. For example, when heat is added to ice (solid), it melts and transforms into water (liquid). Conversely, when water is cooled, it freezes into ice. Similar transformations occur when a liquid such as water evaporates into vapor (gas) or condenses back into liquid.

These processes are facilitated by changes in temperature and pressure, which are fundamental concepts in the study of thermodynamics. This underscores the idea that state changes are a routine part of interactions in physical chemistry and can be anticipated and studied scientifically.

Other choices like "impossible," "difficult," and "infrequent" do not capture the nature of such transformations accurately because while specific conditions may make transitions less straightforward, they remain fundamentally achievable in accordance with the laws of physics and chemistry.