I recently gave an exam that had a particular short answer question where I asked the students, "What type of reaction is this?". I was looking for neutralization reaction, as aqueous NaOH was reacting with aqueous HCl. However, one student identified it as a double displacement reaction, which is also correct. I only gave partial credit for this answer and I am getting pushback from the student. Should I concede the technicality and give full credit?
which is also correct
I think you've answered your own question. If it's correct, then it's correct and should be marked as correct. Why would you mark an answer you've identified as correct as anything besides correct? If it deserved partial marks, you would've said "which is kind of correct".
Unless you're also teaching your students how to read your mind, in which case only the answer you were thinking of deserves full credit, then yes, the student deserves full credit.
If "neutralization" is more specific, and conveys more information than "double displacement", you could do the following:
This is now officially a tricky question. If that was unintended, change it, and be careful in the future to not lay similar traps.
If that was intended, then you need to be clear with your students that on your exam "multiple answers may be true, but you need to pick the best, most specific, one". I'd make sure that a couple of times during lectures I would say "X is a double displacement rxn, which is a very general class, but more specifically it is a neutralization rxn..."
Like Federico Poloni, I can’t fully agree with the top answers. Correctness isn’t the only criterion answers are typically judged by: there’s also usually an expected level of completeness or specificity. As Federico says in comments, “a chemical reaction” would be completely correct, but very few teachers would give it full credit.
However, the expected level of detail must be clearly communicated to students. Usually it’s best to do this in the question itself: don’t just ask “simplify this fraction”, ask “simplify this fraction as far as possible”, or “…to reduced form”, or similar. But sometimes the expectation comes from the teaching: if a calculus class has clearly emphasised the classification of stationary points into local maxima, local minima, and inflection points, then it’s fair to ask “What type of stationary point is this?” and expect one of those three answers, and not give full credit for answers like “It is a stationary point above the x-axis.” In such a case, understanding the expected level of detail is part of the course content.
So in the OP’s case: If the class teaching has unambiguously established an expected level of precision — e.g. putting clear emphasis on a specific classification of reaction types — then it may be reasonable to give only partial credit. But the question in itself is very non-specific about the level of precision expected, so if the context hasn’t clearly established that more precision was expected, you should give full credit.
I'll go against the other answers and argue here that there are valid reasons to assign only partial credit.
I know nothing about chemistry, but from Wikipedia I gather that a neutralization reaction is a special type of double displacement reaction, and I assume that there are specific quantitative results taught in your course that apply only to neutralization reactions, so it is important to identify them and it is not just a matter of naming.
A student that has mastered the material of the course should be able to recognize a neutralization reaction, so that they can apply the relevant results and learn more about it. For another example, I wouldn't want my doctor to say "you have some kind of respiratory disease"; I would like them to be able to identify exactly which one, so that it can be treated with the more appropriate medicine.
A grade, or a question score, should be my best estimate of the mastery of the student; identifying objects that are treated in the course is part of it. This student knows some of the material taught in the course, but clearly not all to a perfect level, otherwise they would have recognized that more specific type of reaction. So partial credit describes the situation perfectly.
I taught high school chemistry, and I would say the answer depends very much on what the overall topic of the exam was. If it was clear from context what you were looking for (say, the topic was "Acids and Bases" or something similar), then yes, this student's answer is technically correct, but clearly missed the point. Partial credit might be appropriate here, or even no credit at all (depending on how far you believe they missed the point).
In another context, "a double displacement reaction" might be the most appropriate answer, for example if the topic of the exam involved the differences between single displacement and double displacement reactions.
If it was a general end-of-semester assessment or an exam on a broader range of topics, you should consider whether it was obvious from context what you were looking for, or not (I would say it's not obvious, but I didn't sit through your course, so I have no idea what you stressed and how). It might be worthwhile to think of what wrong answers a student could reasonably give to such a question, in order to determine if it's sufficiently obvious what you're looking for. In such a case it might be appropriate to give full credit for this answer, and then make the question clearer for next time.
In my junior high:
If teachers declared a rule, in this situation, "You should be precise when deciding the type of a reaction." Then teachers can regard "double displacement reaction" as wrong answer immediately.
If they haven't declared one, they will consider both "double displacement reaction" and "neutralization reaction" to be right because "neutralization reaction" belongs to "double displacement reaction" you know.
You must have noticed that in both situations, "neutralization reaction" is always a right answer. So teachers will tend to declare such rules if such situations exist.