Q: A $$2.0\ \mathrm{m}$$ long steel rail ($$\alpha = 1.2 \times 10$$^{-5}$$\ \mathrm{K}^{-1}) is $$heated from $$10\ ^\circ\mathrm{C} to$$ $$40\ ^\circ\mathrm{C}. $$What is the change in length?

$$\Delta L = 7.2 \times 10$$^{-4}$$\ \mathrm{m}$$

Question 1

Which of the following statements best describes the difference between heat capacity and specific heat?

Accepted Answer

Heat capacity is the amount of heat required to raise the temperature of a substance by $$1\ ^\circ\mathrm{C}$$, while specific heat is the amount of heat required to raise the temperature of $$1\ \mathrm{g} of a $$substance by $$1\ ^\circ\mathrm{C}.$$

Question 2

A $$0.5\ \mathrm{kg}$$ block of aluminum ($$c = 900\ \mathrm{J/kg\cdot K}) at$$ $$100\ ^\circ\mathrm{C} is $$placed in $$1.0\ \mathrm{kg} of $$water at $$20\ ^\circ\mathrm{C}. $$What is the final equilibrium temperature? (Assume no heat loss to the environment, $$c_{\mathrm{water}} = 4186\ \mathrm{J/kg\cdot K})$$

Accepted Answer

$$T_f \approx 24.7\ ^\circ\mathrm{C}$$

Question 3

Which of the following best describes why metals feel colder than wood at the same temperature?

Accepted Answer

Metals have a higher thermal conductivity, so they transfer heat away from your hand more quickly.

Question 4

A gas undergoes an isothermal expansion at temperature $$T. $$Which of the following is true about the change in internal energy $$\Delta U of $$the gas?

Accepted Answer

$$\Delta U = 0$$

Question 5

A $$2.0\ \mathrm{m}$$ long steel rail ($$\alpha = 1.2 	imes 10$$^{-5}$$\ \mathrm{K}^{-1}) is $$heated from $$10\ ^\circ\mathrm{C} to$$ $$40\ ^\circ\mathrm{C}. $$What is the change in length?

Accepted Answer

$$\Delta L = 7.2 	imes 10$$^{-4}$$\ \mathrm{m}$$

Question 6

Which of the following equations correctly represents the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 7

A $$0.10\ \mathrm{mol}$$ sample of oxygen gas is at $$300\ \mathrm{K}. $$What is the average kinetic energy per molecule?

Accepted Answer

$$E_{\mathrm{avg}} = \frac{3}{2}kT$$

Question 8

Which process involves no heat exchange with the surroundings?

Accepted Answer

Adiabatic

Question 9

A refrigerator removes $$500\ \mathrm{J} of $$heat from its interior and expels $$600\ \mathrm{J} to $$the room. What is the work input?

Accepted Answer

$$W = 100\ \mathrm{J}$$

Question 10

Which of the following is a correct statement of the Second Law of Thermodynamics?

Accepted Answer

No heat engine operating between two heat reservoirs can be more efficient than a Carnot engine.

Question 11

A $$1.0\ \mathrm{kg}$$ block of ice at $$0\ ^\circ\mathrm{C} is $$placed in $$1.0\ \mathrm{kg} of $$water at $$20\ ^\circ\mathrm{C}. $$What is the final temperature after all the ice melts? ($$L_f = 334,000\ \mathrm{J/kg}$$, $$c_{\mathrm{water}} = 4186\ \mathrm{J/kg\cdot K})$$

Accepted Answer

$$T_f \approx 0\ ^\circ\mathrm{C}$$

Question 12

Which of the following best describes entropy?

Accepted Answer

A measure of the disorder or randomness of a system.

Question 13

A $$0.5\ \mathrm{kg}$$ copper rod ($$c = 386\ \mathrm{J/kg\cdot K}) is $$heated from $$20\ ^\circ\mathrm{C} to$$ $$120\ ^\circ\mathrm{C}. $$How much heat is required?

Accepted Answer

$$Q = 19,300\ \mathrm{J}$$

Question 14

During which thermodynamic process does the pressure remain constant?

Accepted Answer

Isobaric

Question 15

A $$0.25\ \mathrm{kg}$$ sample of gas at $$300\ \mathrm{K} is $$compressed adiabatically and its temperature rises to $$400\ \mathrm{K}. $$What happens to the internal energy?

Accepted Answer

It increases.

Question 16

Which of the following is NOT a method of heat transfer?

Accepted Answer

Reflection

Question 17

A Carnot engine operates between $$T_H = 500\ \mathrm{K}$$ and $$T_C = 300\ \mathrm{K}. $$What is its maximum possible efficiency?

Accepted Answer

$$\eta = 1 - \frac{T_C}{T_H} = 0.4$$

Question 18

A $$1.0\ \mathrm{mol}$$ sample of an ideal gas is heated at constant volume from $$300\ \mathrm{K} to$$ $$600\ \mathrm{K}. $$What is the change in internal energy? ($$C_V = \frac{3}{2}R)$$

Accepted Answer

$$\Delta U = 1,247\ \mathrm{J}$$

Question 19

Which of the following best explains why sweating cools the human body?

Accepted Answer

Evaporation of sweat absorbs heat from the skin due to the latent heat of vaporization.

Question 20

A $$0.2\ \mathrm{kg}$$ sample of a solid is stretched by $$0.01\ \mathrm{m}$$ under a force of $$100\ \mathrm{N}. $$What is the Young's modulus if the original length is $$1.0\ \mathrm{m}$$ and cross-sectional area is $$1.0 	imes 10$$^{-4}$$\ \mathrm{m}^2$$?

Accepted Answer

$$Y = 1.0 	imes 10^8$\ \mathrm{N/m}^2$$

Thermodynamics and Heat: Exam Study Guide

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