Which one of the following SI units (labels) could properly describe the product of pressure and volume?
A. newton (N)
B. joule (J)
C. watt (W)
D. horsepower $(h p)$

A student is analyzing the properties of a car's engine. She knows how much heat flows in the process and the difference in temperature between the hot and cold parts of the Carnot cycle.
a. How can she determine the change in entropy with an equation?
b. How can she determine the change in entropy graphically?
c. She calculates that $\Delta S$ is negative. Is this reasonable?

If a thermodynamic process has the property of____ then it can run forward and backward to return to its original state.

For one complete cycle plotted in the PV diagram shown, which of the following statements is correct?
A. No net work is done during the cycle.
B. Net work is done on the gas during the cycle.
C. Net work is done by the gas during the cycle.
D. The gas increases its temperature.

In the pressure-volume diagram shown, what kind of thermodynamic process is depicted?
A. a refrigerator
B. a heat engine
C. a Carnot cycle
D. an adiabatic isotherm

Helium gas can be found in a balloon, but at low temperatures it can be in other phases. Which of the following phases of matter for helium will have the highest entropy?
A. solid
B. liquid
C. semi-liquid
D. gas

An ideal Carnot heat engine is operating between temperatures $T_{\text {high }}$ and $T_{\text {low }}$, where $T_{\text {high }}$ is the highest temperature that occurs within the piston during one cycle, and $T_{\text {low }}$ is the lowest. Which of the following formulas correctly gives the efficiency that such an engine has for converting input heat to output work? (Both temperatures must be stated in kelvins.)
A. efficiency $=\left(1+T_{\text {high }}\left(T_{\text {tow }}\right) \times 100 \%\right.$
B. efficiency $=\left(1+T_{10 w} / T_{\text {nigh }}\right) \times 100 \%$
C. efficiency $=\left(1-T_{\text {high }}\left(T_{\text {low }}\right) \times 100 \%\right.$
D. efficiency $=\left(1-T_{\text {low }} / T_{\text {high }}\right) \times 100 \%$

These two $P V$ diagrams each depict one thermal cycle of a piston containing an ideal gas. The pistons are physically identical, but Piston I operates at higher pressure, on average, than Piston II. The lower-left corner of the coordinate grid represents the origin (zero pressure and volume).
a. Which piston does more (positive) work during the expansion phase $(\mathrm{I}, \mathrm{II}$, or a tie)?
b. Which piston does more (negative) work during the contraction phase (I, II, or a tie)?
c. Which piston does more (positive) work during one complete cycle (I, II, or a tie)?

Suppose that an internal combustion engine operates between an internal temperature of $2,000 \mathrm{~K}$ and an exhaust temperature of $1,000 \mathrm{~K}$. What is the engine's maximum theoretical efficiency expressed as a percentage?

What do ocean waves and sound waves have in common?

A. Both are transverse waves.

B. Both are longitudinal waves.

C. Both are electromagnetic waves.

D. Both exhibit the same particle-to-particle interaction.

E. Both are mechanical waves.

A hot rock is plucked from a fire pit and dropped into a bucket of cold water. The rock has a temperature of $80^{\circ} \mathrm{C}$, and it transfers an initial $500 \mathrm{~J}$ of themal energy to the water. Assume that the temperatures of the rock and water remain unchanged during this first instant.
a. Does the entropy of the rock increase or decrease? By how much?
b. Does the entropy of the water increase or decrease? By how much?
c. Does the total entropy of the rock+water system increase or decrease? By how much?

A bearded dragon lizard basks in the desert Sun during the day and reaches a body temperature of $40^{\circ} \mathrm{C}$. At night the air temperature quickly becomes $15^{\circ} \mathrm{C}$. During the course of the night the lizard loses $100 \mathrm{~J}$ of heat while his body temperature equilibrates to the nighttime air temperature. What is his change in entropy?

The gas within a piston expands from an initial volume of $25 \mathrm{~mL}$ to a larger volume of $125 \mathrm{~mL}$, against a constant pressure of $100,000 \mathrm{~Pa}$ (approximate atmospheric pressure at sea level). How much work does the gas in the piston perform?

Mirette put together a business model for a company that would build ideal Carnot engines that convert $100 \%$ of the input heat into energy. Would it be a good idea to invest your life savings in her company?