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State Symbols and the AP Exam

January 15, 2024
A  common post in the AP Chemistry Teacher Facebook group goes something like, “Are state symbols required in chemical equations?”

There’s a temptation to answer question with a blanket, “no”, since when you read the scoring standards from several recent exams you’ll see a pretty consistent, “Ignore state symbols” or, “State symbols not required”. However, that feels like only part of the picture for me. As a side note that’s not especially relevant to the specific question at hand but is related, is that such notes in the scoring standards sit awkwardly against the fact that every equation that ever appears on the exam paper itself, is accompanied by state symbols! Another example of the CB talking out of both sides of their mouth.

Much like my thoughts on the balancing of REDOX equations in acid and base, in no way does the current CED tell us that any requirement for state symbols has been completely removed from the exam. As such, I see no way on Earth, that (for example) a NIE showing the formation of a ppt. where state symbols were required, has been absolutely eliminated. Because there is still a possibility states being required at some point, I’m still going to insist on their use, even if in a relatively limited way.

I do think that if state symbols were to be required, then there is a high likelihood that three would be a direction to do so, but again, that seems entirely possible, and if it’s not been emphasized during the course the students will be in a world of hurt. I prefer an approach with students where state symbols are required, when they matter. Of course the next question becomes, “When do they matter?” For me the answer is simple. Whenever the equation is being used to illustrate a situation where a change of state is essentially the point the of reaction or states are integral to the use of the equation. In most circumstances this falls into four categories;

  • a literal change of of phase
  • the formation of precipitate
  • the formation of a gas
  • the formation of a pure liquid, usually water

The second, third and fourth in that list are crucial in terms of net ionic equations, not to mention when subsequently creating equilibrium constants, so you’d better get them correct. It’s clear to me that I think this skill is more important that the CB does, but of course their priorities continue to shift away from such fundamentals, and toward other things. I mean just think about the skill-set required to construct a net ionic equation for a double-displacement, precipitation reaction from scratch. What that used to look like on the AP exam (and therefore in AP chemistry classrooms) was something like this;

  • Use nomenclature (which included significant amounts of pure memorization of polyatomic ions) to convert the names of aqueous compounds into formulae
  • Re-arrangement of those formulae to create a full equation using the correct stoichiometry
  • Balancing of the equation
  • Application of the memorized, full set of solubility rules to identify the precipitate
  • Deconstruction of aqueous solutions using the correct stoichiometry and knowing charges
  • Identification of spectators to produce the net ionic equation

Compare that process to 2019, 3(a) which is an example of a modern NIE question that has removed around 85% of that work. It’s really quite sad. All of this is connected to the total devastation of Question #4 of course, and in that regard the horse bolted long ago.

Another unacceptable example (to me) is the omission of the necessity for state symbols in a question like 2015, 4(a). Ignoring them in part (a), strictly speaking means that 4(b) can’t be answered correctly. I would NEVER allow a student of mine to write that equation without states, and not because I’m some stickler for philosophical process, but rather because it matters! Finally, in my opinion, 2008, 5(a) is actually wrong without state symbols because the definition of first ionixation energy includes consideration of states.

Anyone who knows me well also knows that I’m not one to have an emotional connection to content that has now passed into the annals of history. I’m not driven by some philosophical need to, “teach the children great chemistry”, rather I am driven by the exam and maximizing the scores. As such, my motivation for continuing to insist on state symbols much of the time is most definitely not driven by nostalgia, rather it’s driven by the fact that as of now, my interpretation of the CED just won’t let me drop them completely despite the College Board’s continual devastation of the AP exam as an intellectual pursuit. If a sentence appears in a subsequent CED that says, “State symbols will never be required” I’ll drop them completely.


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