The aim of this diploma thesis is to present and elaborate some key experiments on the matter-particle-concept, in order to make them useable for classroom practice. This applicability was also tested in a secondary school II and surveyed and evaluated using a questionnaire.The thesis consists of three parts, namely the didactic part, the experimental part and the practical part.The didactic part includes important contents on basic concepts and the matter-particle-concept, in particular, the importance of models in chemistry lessons, the competency models, experimentation as a teaching method as well as other teaching methods. The experimental part contains hints for the planning of experiments according to the matter-particle-concept and several selected experimental examples. Finally, the practical part includes the practical usage of some selected key experiments in a secondary school II as well as the results and evaluations of the questionnaires. In the appendix of this thesis, the repertoire of key experiments, in the form of pupils and teachers' sheets, can be found.