Chemistry is an experimental discipline that uses experimentation as one of its most important research methods. Laboratory work and other practical work are therefore also essential in chemistry lessons. Chemistry demonstrations are used by teachers as an educational approach that can increase students' interest in chemistry and motivate them to learn chemical concepts with understanding. However, if the students are actively involved in the chemistry demonstration, it can be just as effective as or even more effective than students' learning through experiments. The purpose of this research is to examine teachers' opinions about the impact of chemistry demonstrations on students' interest and chemistry knowledge. Based on a quantitative research approach, 81 primary and secondary school teachers from different regions of Slovenia participated in this study. Participating teachers completed an online questionnaire on their perceptions of the impact of chemistry demonstrations on students' interest and performance in chemistry classes and on the quality of students' knowledge of chemistry. The results show that regardless of the years of teaching experience and the frequency of performing chemistry demonstrations, the participating teachers consider such demonstrations to have a positive effect on the motivation and performance of the students in chemistry and on the quality of the students' knowledge of chemistry.