This is a general problem with organization and counting of abstract categories. All of my science, history, and social science courses in middle/high school we

This is a general problem with organization and counting of abstract categories. All of my science, history, and social science courses in middle/high school were pretty much garbage, and as far as I can tell that is the norm in the US (and many other places; not through special fault of the teachers, but because the curriculum/textbooks are insipid). “State of matter” is not a perfectly defined property, but only a simplified model of high-level aggregate behavior/interactions; individual particles have simpler interactions which are not categorized the same way. Scientists are happy to admit a new “state of matter” whenever they manage to observe a situation that doesn’t behave according to their previous models, and are happy to admit that the states of matter are just a simplified model, but some petty bureaucrats (like, sadly, many teachers) can’t handle this. You can similarly get into trouble arguing about how many “kingdoms” there are of eukaryotes, or how many Romance “languages” there are, or how many “continents” there are, or the difference between crops and weeds or a fetus and a person or plagiarism and research. Quizzing students on how well they can memorize and recall labels (and even worse, punishing them for knowing additional labels) is not just an incredible waste of human time and attention, but is actively harmful insofar as it disempowers students to ask and investigate their own questions and discourages them from seeking a deeper understanding of what they are learning. I really appreciate the beginning of the MIT electronics textbook https://amzn.com/1558607358 https://amzn.com/1558607358 which explicitly describes the abstractions used and their limitations, up front. Rare economics textbooks also do a decent job of this.