text: "pv=nrt" is a subject of chemistry or physics?   that is the "ideal gas law," which is something that you would normally see in a chemistry class.   in reality, it has applications in both fields. the fields are definitely related in important ways. long ago, chemistry and physics were very different fields; however, as more was learned about how chemical and physical changes were related, the two fields became related.  so now there are lots of things that blur the line. however, a fundamental like the ideal gas law will probably first be covered in a chemistry context.  so if you need to make a classification, then go for "chemistry." generally "laws" that govern large systems are typically found in chemistry. of course, all chemistry can be derived from fundamental physical laws. however, doing chemistry purely at a physical level would be difficult. chemistry uses special structures and relationships to encapsulate lots and lots of physics into simplifications that can be used to do useful chemistry. the ideal gas law is one such example.