Teacher-student conversations are central to student learning within the science classroom. Educational literature recommends teachers aim to build a common scientific language and, through dialog, develop shared meanings with students. This study examines teacher-student conversations in the specific situation of an integrated science and engineering curriculum, involving lessons on heat transfer. The findings identify critical nuances and discourse patterns in the conversations that may pose barriers to student engagement and learning. The study illustrates the need for teachers to plan dialogic, authentic interaction with students to build shared meanings about scientific concepts in order to enhance STEM learning.