Why are the boundaries between physics and chemistry sometimes difficult to separate?

The boundary between physics and chemistry is considered somewhat arbitrary because the two fields are deeply interconnected through their study of matter and energy. While physics traditionally focuses on the structure and behavior of individual atoms and their components, chemistry deals with the properties and reactions of molecules. Because these molecular properties are fundamentally dependent on atomic structure and energy—particularly heat—the two disciplines frequently overlap.1

This intersection is most evident in physical chemistry, a branch of science that applies the principles of physics to explain chemical interactions and transformations. Furthermore, quantum mechanics serves as a shared theoretical foundation for both fields; it accounts for atomic structure, the periodic table of elements, and the chemical behavior of matter.234

Ultimately, while chemists often prioritize the specific properties of different elements and compounds, physicists tend to investigate the general properties shared by all matter, making the distinction between the two areas a matter of focus rather than a rigid separation.1