AP Chemistry — Unit 6: Thermodynamics
Practice questions, answers, and key terms for Unit 6, aligned to the College Board CED.
Exam weighting: Unit 6 is 7-9% of the AP Chemistry exam.
What AP Chemistry Unit 6 covers
The College Board Course and Exam Description breaks Unit 6 into 8 topics:
- 6.1 Endothermic and Exothermic Processes
- 6.2 Energy Diagrams
- 6.3 Heat Transfer and Thermal Equilibrium
- 6.4 Heat Capacity and Calorimetry
- 6.5 Enthalpy
- 6.6 Bond Enthalpies
- 6.7 Enthalpy of Formation
- 6.8 Hess's Law
AP Chemistry Unit 6 practice questions
What does it mean for a chemical reaction to be exothermic?
The system releases energy to the surroundings; ΔH is negative.
When an ionic solid dissolves in water and the solution temperature drops, what does this indicate about the dissolution process?
Dissolution is endothermic — the system absorbs thermal energy from the surroundings.
How do endothermic and exothermic processes differ in terms of energy flow between the system and surroundings?
Endothermic draws energy into the system; exothermic releases it to the surroundings. ΔH is positive for endothermic, negative for exothermic.
On an energy diagram for a chemical reaction, what does the vertical distance between reactants and products represent?
The net enthalpy change of the reaction — its ΔH. This is the net energy absorbed or released.
An energy diagram shows products at a higher energy level than reactants. What does this indicate about ΔH and energy transfer?
ΔH is positive; the reaction is endothermic, absorbing energy. The system takes in energy from the surroundings.
At the particulate level, what distinguishes the particles of a warmer object from those of a cooler object?
Particles in a warmer body have a greater average kinetic energy than particles in a cooler body.
A hot metal block is placed in cool water inside an insulated container. What is true once thermal equilibrium is reached?
Both the metal and water reach the same temperature; their average kinetic energies are equal.
What equation is used to calculate heat transferred during heating or cooling of a substance?
q = mcΔT, relating heat to mass, specific heat, and temperature change. Here q = heat, m = mass, c = specific heat, ΔT = temperature change.
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Key terms in Unit 6
These 12 terms show up in the Unit 6 cards. Each one links to its definition in the AP Chemistry key-term reference.
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