This study presents an experimental cross-thematic teaching program of Science Education and Language in the particular concept of objects’ classification according to the three states of matter. The aim of the study was the investigation of the design, application and evaluation of a cross-thematic teaching intervention, which was comprised of activities of science and language. The teaching program was evaluated according to the comparison of children’s responses to the pre- and post-test. The results revealed a great improvement in children’s understanding of ideas and knowledge related to the three states of matter as well as enrichment of vocabulary and the number of sentences. This study provides an example of cross-thematic work which incorporates learning targets from Science Education as well as Language in the Early Years.