This paper presents preliminary findings of a research study designed to investigate some difficulties presented by technical and high school students, regarding thermodynamical concepts, that might be indicators for future studies concerning the so-called Vergnaud's operational invariants. Those invariantes which are usually implicit in students' cognitive structure might function as obstacles to concept learning. The study was carried out with 99 students from Liberato Salzano Vieira da Cunha Technical School, in Novo Hamburgo, RS, Brazil. Students' answers to a questionnaire involving thermodynamical problem-situations were analysed and some possible indicators of operational invariants were found.
thermodynamical concepts; operational invariants; conceptual fields
