Framed by the Vygotskian claim that human action is mediated by tools and signs, in particular the use of language, this study examined the words used by five teachers in six upper-secondary chemistry classrooms across sixty-nine lessons. Content analyses of verbatim transcripts produced frequency counts of words used to direct the attention of students to the processes of thinking and expressing thoughts about chemistry, that is words with a metacognitive and metalinguistic function. While there was some individual variation among teachers, this word use was generally limited in extent and simple or colloquial in expression, and the language of the enacted curriculum did not match the terminology of the official curriculum document. A series of questions about the importance of language about thinking and expressing ideas in Chemistry is raised for future consideration.