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AP Chem · Unit 6 Progress Check

AP Chemistry Unit 6 Progress Check Thermodynamics walkthrough.

AP Chemistry Unit 6 is thermodynamics, and the Unit 6 Progress Check MCQ is dominated by sign conventions, calorimetry, and Hess’s law. This walkthrough covers what each question type tests, the traps that cost points, and how to work through them. Explanations only — no AP Classroom answer keys.

Updated August 2026Written by Mahmudul HasanFree · No signup

What Unit 6 covers

Unit 6 is Thermodynamics. Thermodynamics is roughly 7–9% of the AP Chemistry exam and sets up the applications unit at the end of the course.

Endothermic and exothermic
Sign conventions for q and ΔH, and what each means for the surroundings.
Calorimetry
q = mcΔT, and using a calorimeter to measure heat transfer.
Enthalpy of reaction
ΔH as a state function, and standard enthalpies of formation.
Hess’s law
Combining reactions, reversing signs, and scaling coefficients.
Bond energy
Estimating ΔH from bonds broken minus bonds formed.
Heating curves
Why temperature stays constant during a phase change.

The Progress Check MCQ: what each question type tests

These are the question patterns that recur on this Progress Check, and what each one is really asking.

Sign reasoning
Exothermic releases heat and has negative ΔH. If the surroundings warm up, the reaction is exothermic.
Calorimetry calculation
Identify m, c, and ΔT, and be careful about which substance the heat flows into.
Hess’s law manipulation
Reverse a reaction and flip the sign; double it and double ΔH.
Bond energy estimate
Bonds broken minus bonds formed. Breaking bonds always costs energy.
Heating curve interpretation
Flat segments are phase changes where energy goes to potential, not kinetic, energy.

The Progress Check FRQ

Unit 6 free response usually gives calorimetry data or a set of reactions and asks for a calculation plus an explanation. Points come from correct signs, correct use of q = mcΔT or Hess’s law, and a particle-level explanation of where the energy went.

Where students lose the most points

Sign errors
Exothermic is negative ΔH. Getting the sign backwards inverts the whole answer.
Forgetting to flip ΔH when reversing a reaction
Reversing a reaction reverses the sign, always.
Using ΔT in Celsius versus kelvin incorrectly
A temperature change is the same in both, but absolute temperatures are not — know which the problem needs.
Expecting temperature to rise during a phase change
Energy goes into breaking intermolecular forces, so temperature holds constant.
Reversing the bond-energy formula
It is bonds broken minus bonds formed, not the other way around.

How to work through this unit

Before any thermodynamics calculation, decide whether the system is releasing or absorbing energy and write the sign down first. Most Unit 6 errors are sign errors, not arithmetic ones.

Once you have finished the Progress Check, put your raw score into our AP Chemistry Calculator to see roughly where that pace puts you on the 1–5 scale, and use the AP Chemistry Review for the full exam format and study plan.

Frequently asked questions

Quick answers — written by humans, not a chatbot.

What does the AP Chemistry Unit 6 Progress Check cover?

Thermodynamics: endothermic and exothermic processes, calorimetry and q = mcΔT, enthalpy of reaction, Hess’s law, bond energy, and heating curves.

Why does temperature stay constant during a phase change?

Because the energy being added goes into overcoming intermolecular forces rather than increasing the average kinetic energy of the particles, so the temperature does not change until the phase change is complete.

How do I use Hess’s law?

Combine the given reactions so they sum to the target reaction, reversing the sign of ΔH for any reaction you flip and scaling ΔH by the same factor you scale the coefficients.

Do you publish AP Chemistry Unit 6 answer keys?

No. We publish walkthroughs of the reasoning and the traps instead of raw AP Classroom answers.

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