This research project in the field of physics education consists of three phases: conceptual reconstruction of the topic, literature review on learning difficulties and teacher education; evaluation of primary and secondary school teachers’ teaching practices on the properties of matter and their roles in physics; and focus group interviews with nine teachers to deepen the results of previous studies. Findings from the interviews show that some teachers do not have sufficient knowledge about the properties of matter and their roles in physics. Teachers often focus on the phase or state of properties of matter, but they emphasize the need to clarify the nature and relationship between the fundamental properties of matter. Although they state that understanding the properties of matter forms the basis of science education, they cannot provide sufficient examples of how and in what way it should be taught. As a result, teachers need to improve their content knowledge about the properties of matter and be supported with active learning methods that support formal thinking.
