The model of the particle nature of matter has been one of the fundaments in science and science education. This model describes matter as being composed of small hard solid entities - particles - often known as atoms and molecules, clinging to each other or moving around in empty space. However, from a scientific point of view there are problems with this model; for instance, quantum mechanics describes atoms as having both particle as well as wave properties implying that the entities are neither hard nor solid. The particle nature of matter model is also facing problems within science education. Students’ conceptions of the concept of particle appears to be limited.

In this talk I will describe how science teachers’ understanding of the model of the particle nature of matter is limited too. Eleven secondary school science teachers were interviewed about their arguments for the particle nature of matter. Although the teachers appears to have an epistemological understanding of the concept of models in science they give vague arguments for the particle nature of matter model. Particularly, they have problems justifying the model from specific experiments. The model of the particle nature of matter is discussed in the light of these interview data, but also in the light of historical arguments and verifications of the model.