Socio-scientific issues demonstrate the relationship between science, technology, and society by considering currently unresolved questions. The problem of plastics and their pollution is just one example with important implications for the planet. The aim of this paper is to revisit socio-scientific issues and see them as a way of developing citizens' critical thinking skills through chemistry education. In light of the problems posed by plastics, we present evidence tested with Spanish grade-8 students of how critical thinking skills can be developed through chemistry education in terms of the vision of chemistry, understanding acquisition, a holistic approach to problems, critical analysis of information, argumentation, decision making, personal autonomy, and communication. This study also presents some examples of how progress in the development of critical thinking by students has been evaluated.