Q: A 55-cm stainless steel rod ($$\alpha = 1.7 \times 10$$^{-5}$$ \, ^\circ\mathrm{C}^{-1}) is $$cooled from $$20^\circ\mathrm{C} to$$ $$-196^\circ\mathrm{C}. $$What is the change in length ($$\Delta L) of $$the rod?

$$\Delta L = L \alpha \Delta T = 0.55 \times 1.7 \times 10$$^{-5}$$ \times (-216) = -0.0020 m$$

Question 1

Which of the following best describes the First Law of Thermodynamics for a closed system?

Accepted Answer

The change in internal energy is equal to the sum of heat added and work done on the system: $$\Delta E_{int} = Q + W$$

Question 2

A gas in a piston is heated at constant pressure. Which of the following statements is true about the change in enthalpy ($$\Delta H) $$compared to the change in internal energy ($$\Delta E_{int}$$)?

Accepted Answer

$$\Delta H is $$greater than $$\Delta E_{int}$$ because work is done by the gas during expansion.

Question 3

Which process involves heat transfer but not work?

Accepted Answer

Melting ice in a freezer.

Question 4

A 55-cm stainless steel rod ($$\alpha = 1.7 	imes 10$$^{-5}$$ \, ^\circ\mathrm{C}^{-1}) is $$cooled from $$20^\circ\mathrm{C} to$$ $$-196^\circ\mathrm{C}. $$What is the change in length ($$\Delta L) of $$the rod?

Accepted Answer

$$\Delta L = L \alpha \Delta T = 0.55 	imes 1.7 	imes 10$$^{-5}$$ 	imes (-216) = -0.0020 m$$

Question 5

Which of the following is the correct formula for linear thermal expansion?

Accepted Answer

$$\frac{\Delta L}{L} = \alpha \Delta T$$

Question 6

A glass of water is heated from $$20^\circ\mathrm{C} to$$ $$30^\circ\mathrm{C}. $$What is the final temperature in Kelvin?

Accepted Answer

$$303 K$$

Question 7

Which of the following best explains why gases are compressible while solids and liquids are not?

Accepted Answer

Gas molecules are far apart with much empty space between them.

Question 8

Which of the following processes involves both heat and work transfer?

Accepted Answer

A piston is placed into a cylinder of gas, increasing the temperature of the gas.

Question 9

If the temperature of a gas does not change during expansion, what can be said about the internal energy change ($$\Delta E_{int}$$)?

Accepted Answer

$$\Delta E_{int} = 0$$

Question 10

Which of the following is NOT a phase change that involves heat transfer?

Accepted Answer

Compressing a gas at constant temperature.

Question 11

A sample of gas is compressed in a piston at constant temperature. What happens to the pressure and volume?

Accepted Answer

Pressure increases as volume decreases, according to Boyle's Law: $$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 12

Which of the following is the correct expression for the work done by a gas during expansion at constant pressure?

Accepted Answer

$$W = P \Delta V$$

Question 13

Which of the following statements about solids, liquids, and gases is correct?

Accepted Answer

Liquids have molecules that are close together but can slide past each other.

Question 14

A paddle does work on water, increasing its temperature. Which form of energy transfer is primarily responsible for the temperature increase?

Accepted Answer

Work done on the system ($$W)$$

Question 15

Which of the following is the correct relationship for the change in internal energy for a process where only heat is transferred?

Accepted Answer

$$\Delta E_{int} = Q$$

Question 16

A gas is heated at constant volume. What is the work done by the gas?

Accepted Answer

$$W = 0$$

Question 17

Which of the following best describes the molecular arrangement in a solid?

Accepted Answer

Molecules are closely packed in a fixed lattice and vibrate about fixed positions.

Question 18

Which of the following is a real-world example of a process where both heat and work are transferred to a system?

Accepted Answer

Heating air in a piston while compressing it.

Question 19

A gas is compressed in a piston and its temperature increases. Which of the following statements is true?

Accepted Answer

Work is done on the gas, increasing its internal energy.

Physics 3B: Chapter 12 – Thermodynamics, Heat, and Thermal Expansion

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