Master's Thesis from the year 2018 in the subject Didactics - Chemistry, Samar State University (College of Graduate Studies), course: MAT-Chemistry, language: English, abstract: This study investigated grade 3 and grade 6 science teachers' knowledge and scientific understanding of the particulate nature of matter of public elementary school in the City Division of Catbalogan, Samar. In this regard, the study employed descriptive research designwhich involved 36 grade 3 and 36 grade 6 teachers. Data were collected using two-tier diagnostic test. Results showed that teachers have below average knowledge and exhibited no scientific understanding of the particulate nature of matter and possess several unscientific understanding.