In a previous publication, Jensen's scheme for the logical structure of chemistry was employed to identify a logical structure for physical chemistry, which was further used as a tool for analyzing the organization of twenty physical chemistry textbooks. In addition, science education research was considered for the study of the psychological structure of physical chemistry. In this companion paper, the findings are presented of a semi-structured interview study with seventeen chemistry graduates, which aimed to find out their opinion about the difficulties of the various areas of physical chemistry, their disposition towards the subject, and their explanations for the difficulties identified, and in this way to study further the psychological structure of physical chemistry. A mixture of an intensive inductive and a confirmatory data analysis was carried out that revealed ideas and trends and allowed for a reliable portrait of learners to emerge by identifying similarities and differences in the data. Students unanimously found the phenomenological subjects (classical thermodynamics, electrochemistry, chemical kinetics) easier than the submicroscopic subjects of quantum chemistry and statistical thermodynamics. The reasons invoked included that the latter subjects deal with more difficult and abstract concepts, and also their highly mathematical nature. Many students found classical thermodynamics simpler than quantum chemistry, because it "has logic", includes "tangible examples", and they had encountered related topics before (especially in high school). The findings for electrochemistry and chemical kinetics were more or less similar to those for classical thermodynamics. Implications, generalizability, and limitations of the findings and prospects for further research are discussed.