The chemistry competition, which marks the 50th anniversary this year, is an important form of external evaluation of chemistry knowledge, which with its evaluation offers objective information about the quality and quantitiy of chemistry knowledge in primary school. With the evaluation of knowledge we inform the students what to learn, how to learn and what quality of knowledge we expect from them. At the same time, the teacher gets important information about the students' knowledge. The teacher has to evaluate his or her teaching through the knowledge and skills which the students assimilate. The teacher has to evaluate his own work critically and has to be prepared to improve it constantly. In the introduction, a theoretical definition of the fields of evaluation, with the emphasis on external evaluation, is given. Among the forms of external evaluation of chemistry knowledge in primary school in Slovenia belong: the National evaluation of knowledge, the International knowledge testing TIMSS and the Chemistry competition for Pregl's certificate.
In the empirical part, the results of the analysis of solved 49th national chemistry competition tests for Pregl's certificate 2015, are introduced. The contents fields which were learnt well and the ones which were solved wrong or there were mistakes or misunderstanding of tasks by the students, were established. The most common mistakes and possible reasons for them and the successfulness according to taxonomy level, are presented. The analysis showed that the knowledge of chemistry is good, but students have problems with integration of knowledge and its usage in new situations. In many cases, the reason for mistakes are in understanding of what they read, the misunderstanding of instructions and inaccuracy of students.
Based on these results we gave suggestions for improving teaching.