摘要：One of the general problems in science education for different students at comprehensive school is understanding the nature of physical and chemical changes. Without a clear picture of the fundamental differences on sub micro level, it is not possible in the future to follow general rules of chemical reactions between substances, as well as to understand the use of different materials in everyday life. Students of the grades 9 and 11 were asked to fill in a special questionnaire, in which questions about real physical and chemical changes from students’ daily life were included. The results testify that the knowledge and understanding of the essence of chemical reactions has slightly increased in Latvia, although the general results show that understanding of the nature of phase transitions and chemical reactions is still insufficient, especially at the grade 9 levels.
