In this study, it was aimed to determine 7th grade students' understanding of some chemistry concepts. For this reason, according to Turkish Science and Technology Curriculum, a valid and reliable concept test was developed related to the concepts of "measurable properties of substance, heat and temperature, pure substance and mixture, particulate nature of substance, elements and compounds, elements and symbols, and structure of atom". During development of the test, literature was reviewed and then item pool consists of multiple- choice items was formed in accordance with the teaming objectives determined by Ministry of National Education. After the test was validated by a group of chemistry educators, it was applied to 217 seventh grade students. The coefficient alpha of the last version of the test, consists of 32 items, was found as to be 0.80. The results of students' responses indicated that they commonly had misconceptions such as atoms can be seen under microscope, different elements consist of the same atoms, there is no space between particles in atoms, atoms only include nucleus. It was also found that students confused mixture and element, compound and molecule, melting and solubility, and they could not distinguish the substance that include molecules. (C) 2014 The Authors. Published by Elsevier Ltd.