Q: A steel bridge expands by $$1.2\ \mathrm{cm}$$ when the temperature increases by $$30\ ^\circ\mathrm{C}. If $$the original length of the bridge is $$120\ \mathrm{m}$$, what is the linear expansion coefficient $$\alpha of $$steel? Use $$\Delta L = \alpha L_0$ \Delta T.$$

$$\alpha = 3.3 \times 10$$^{-5}$$\ ^\circ\mathrm{C}^{-1}$$

Question 1

Which of the following best describes the physical meaning of temperature in the context of kinetic theory of gases?

Accepted Answer

Temperature is a measure of the average translational kinetic energy of the molecules.

Question 2

A steel bridge expands by $$1.2\ \mathrm{cm}$$ when the temperature increases by $$30\ ^\circ\mathrm{C}. If $$the original length of the bridge is $$120\ \mathrm{m}$$, what is the linear expansion coefficient $$\alpha of $$steel? Use $$\Delta L = \alpha L_0$ \Delta T.$$

Accepted Answer

$$\alpha = 3.3 	imes 10$$^{-5}$$\ ^\circ\mathrm{C}^{-1}$$

Question 3

A weather balloon contains $$2.0\ \mathrm{mol} of $$helium at $$1.0\ \mathrm{atm}$$ and $$27\ ^\circ\mathrm{C}. If $$the balloon rises to an altitude where the pressure is $$0.5\ \mathrm{atm}$$ and the temperature is $$-23\ ^\circ\mathrm{C}$$, what is the new volume of the balloon? (Assume ideal gas behavior.)

Accepted Answer

$$V_2 = 89.6$$\ \mathrm{L}$$

Question 4

Which of the following statements about Brownian motion is correct?

Accepted Answer

Brownian motion results from the random collisions of fluid molecules with suspended particles.

Question 5

A $$0.5\ \mathrm{kg}$$ block of aluminum at $$80\ ^\circ\mathrm{C} is $$placed in $$1.0\ \mathrm{kg} of $$water at $$20\ ^\circ\mathrm{C}. $$What is the final equilibrium temperature? ($$c_{\mathrm{Al}} = 900\ \mathrm{J/kg\cdot ^\circ C}$$, $$c_{\mathrm{H_2O}} = 4186\ \mathrm{J/kg\cdot ^\circ C})$$

Accepted Answer

$$T_f = 27.7\ ^\circ\mathrm{C}$$

Question 6

Which process describes the transfer of thermal energy by the bulk movement of a fluid?

Accepted Answer

Convection

Question 7

A $$0.2\ \mathrm{kg}$$ sample of ice at $$-10\ ^\circ\mathrm{C} is $$added to $$0.5\ \mathrm{kg} of $$water at $$30\ ^\circ\mathrm{C}. $$What is the final temperature of the system? ($$c_{\mathrm{ice}} = 2090\ \mathrm{J/kg\cdot ^\circ C}$$, $$c_{\mathrm{H_2O}} = 4186\ \mathrm{J/kg\cdot ^\circ C}$$, $$L_f = 3.33 	imes 10^5$\ \mathrm{J/kg})$$

Accepted Answer

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

Question 8

Which equation correctly relates the root-mean-square speed $$v_{\mathrm{rms}} of a $$gas molecule to temperature $$T$$ and molar mass $$M$$?

Accepted Answer

$$v_{\mathrm{rms}} = \sqrt{\dfrac{3RT}{M}}$$

Question 9

A $$1.0\ \mathrm{mol}$$ sample of an ideal monatomic gas undergoes an isothermal expansion at $$300\ \mathrm{K}$$ from $$10.0\ \mathrm{L} to$$ $$20.0\ \mathrm{L}. $$What is the work done by the gas? ($$R = 8.314\ \mathrm{J/mol\cdot K})$$

Accepted Answer

$$W = 172.8\ \mathrm{J}$$

Question 10

Which of the following best describes the first law of thermodynamics for a closed system?

Accepted Answer

$$\Delta E_{\mathrm{int}} = Q - W_{\mathrm{by}}$$

Question 11

A $$0.1\ \mathrm{mol}$$ sample of a diatomic ideal gas is heated at constant volume. If the temperature increases by $$50\ \mathrm{K}$$, how much energy is added to the gas? (Assume $$C_v = \dfrac{5}{2}R$$ for diatomic gases, $$R = 8.314\ \mathrm{J/mol\cdot K})$$

Accepted Answer

$$104\ \mathrm{J}$$

Question 12

Which of the following is true about the molar heat capacity at constant pressure ($$C_p) $$and at constant volume ($$C_v) $$for an ideal gas?

Accepted Answer

$$C_p = C_v + R$$

Question 13

A $$0.5\ \mathrm{mol}$$ solution of NaCl is separated from pure water by a semipermeable membrane. At $$300\ \mathrm{K}$$, what is the osmotic pressure? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$24.6\ \mathrm{atm}$$

Question 14

Which of the following is NOT a correct statement about thermal expansion?

Accepted Answer

Polymers such as rubber and plastic have negligible thermal expansion.

Question 15

A gas undergoes an adiabatic expansion. Which of the following statements is true?

Accepted Answer

No heat is exchanged with the surroundings.

Question 16

A $$2.0\ \mathrm{g}$$ sample of helium gas is at $$1.0\ \mathrm{atm}$$ and $$27\ ^\circ\mathrm{C}. $$What is the root-mean-square speed of the helium atoms? ($$M_{\mathrm{He}} = 4.0\ \mathrm{g/mol}$$, $$R = 8.314\ \mathrm{J/mol\cdot K})$$

Accepted Answer

$$v_{\mathrm{rms}} = 1360\ \mathrm{m/s}$$

Question 17

Which of the following best explains why you should not drink ocean water if stranded at sea?

Accepted Answer

Drinking ocean water causes net osmotic flow of water out of your cells, leading to dehydration.

Question 18

A $$1.0\ \mathrm{mm}$$ thick glass window ($$k = 0.8\ \mathrm{W/m\cdot K}) $$has an area of $$2.0\ \mathrm{m}^2. If $$the temperature difference across the window is $$20\ ^\circ\mathrm{C}$$, what is the rate of heat transfer through the window?

Accepted Answer

$$Q/t = 32\ \mathrm{W}$$

Thermal Physics: Temperature, Expansion, Ideal Gases, Kinetic Theory, and Thermodynamics

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