The aim of this study is to evaluate the cognitive levels of pre-service science teachers according to Bloom's Taxonomy about "density" using daily life problems. The case study design was used in the study. This study was carried out with 45 pre-service teachers. In order to identify the cognitive levels of pre-service teachers about the density subject, a cognitive level test have been used created in line with the Bloom's Taxonomy, formed with the purpose of identifying their views about daily life problems requiring higher level thinking skills. When the cognitive levels of pre-service teachers have been analysed, it has been found out that all the pre-service teachers have completed the knowledge, comprehension and application levels while 20 of them have got through analysis level. 13 of them have passed into the synthesis level which requires a higher level thinking skill while 9 of them have reached the last stage, 'evaluation'. According to the findings, in order to progress within the cognitive thinking levels while learning 'density' subject, students should overcome the mathematical deficiencies and concentrate more on daily life problems which require a higher-level thinking skill.