AP Chemistry: Why Students Ace the Homework and Still Lose Points on the Test

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By Chi Young Ji, Director · AP Biology and AP Chemistry

“The homework is always right. Then the test comes back, and the score isn’t there.”

I hear this from AP Chemistry parents more than almost anything else. The student works every day. The answers check out. So the frustration is understandable: this isn’t a child who isn’t trying. Why does it fall apart only on test day?

Solving a problem and explaining it are two different things

Being able to solve a problem and being able to explain why it works are not the same skill. The second one is what understanding actually looks like.

Homework mostly mirrors the examples from class. A student can keep the example open, swap in new numbers, and arrive at the right answer. A test does something else. It presents a situation the student has never seen and asks why it behaves the way it does.

The AP Chemistry exam is built this way on purpose. According to the College Board’s Course and Exam Description, 15–24% of the free-response section and 8–12% of the multiple-choice section assess argumentation, the ability to make a claim and support it with evidence. It is not an exam a student can fully score on answers alone. That is why the students who earn a 5 are, almost without exception, the ones who study for understanding.

The people who grade the exam say the same thing. The 2025 Chief Reader Report for AP Chemistry includes this line: “Just memorizing that ‘basic salts are more soluble in acidic solution than neutral solution’ did not help the student earn this point.” A student wrote down a memorized sentence, word for word, and received no credit for it.

Which kind of student is my child?

In a consultation, the first thing I look for is one thing: can the student explain it?

You can check this at home in a few minutes. Pick one homework problem your child got right and ask:

• What is actually happening at the molecular level here?
• When do you use that formula, and why?

You don’t need to know any chemistry. You don’t need to judge whether the answer is correct. Just notice whether the explanation flows, or whether it stops at “that’s just how you solve it.”

When the explanation is there, and when it isn’t

If your child can explain, there is little to worry about. From here it’s a matter of getting familiar with the question types and practicing free-response questions under time.

If the explanation isn’t there, that is a signal to change how they study. More problems are not the answer. More problems done the same way are just more practice at memorizing. The direction has to change: go back through each concept and rebuild it from the “why.”

It takes time, and it takes real effort. It is also the work that has to be done. If it is hard to do alone, getting help is a reasonable place to start.