Question 1

Which of the following best describes the concept of internal energy in thermodynamics?

Accepted Answer

The total energy of a system associated with the random, microscopic motions and interactions of its atoms and molecules, including translational, rotational, vibrational kinetic energy, and intermolecular potential energy.

Question 2

In Joule's paddle-wheel experiment (see $$image_1$$), what physical principle was demonstrated?

Accepted Answer

Mechanical energy can be completely converted into internal energy, establishing the mechanical equivalent of heat.

Question 3

A 0.050 kg metal ingot is heated to $$200.0\ ^\circ \mathrm{C}$$ and dropped into $$0.400 kg of $$water at $$20.0\ ^\circ \mathrm{C}. $$The final temperature is $$22.4\ ^\circ \mathrm{C}. $$Using $$c_w = 4186\ \mathrm{J/kg\cdot ^\circ C}$$, what is the specific heat of the metal? (Refer to the equations in images 2 and 3.)

Accepted Answer

$$c_x = 453\ \mathrm{J/kg\cdot ^\circ C}$$

Question 4

Which equation correctly expresses the First Law of Thermodynamics?

Accepted Answer

$$\Delta E_{\mathrm{int}} = Q + W$$

Question 5

A gas is compressed in a cylinder at constant pressure. Which equation gives the work done on the gas?

Accepted Answer

$$W = -P (V_f - V_i)$$

Question 6

In a calorimetry experiment, why is the negative sign in $$Q_{\mathrm{cold}} = -Q_{\mathrm{hot}}$$ important?

Accepted Answer

It ensures that the heat lost by the hot object is equal in magnitude and opposite in sign to the heat gained by the cold object, consistent with energy conservation.

Question 7

During which thermodynamic process is $$Q = 0$$ and $$\Delta E_{\mathrm{int}} = W$$?

Accepted Answer

Adiabatic process

Question 8

A gas undergoes an isothermal expansion from $$V_i to$$ $$V_f at $$temperature $$T. $$What is the work done on the gas?

Accepted Answer

$$W = -nRT \ln \left( \frac{V_f}{V_i} \right)$$

Question 9

Which of the following is true for an isovolumetric (isochoric) process?

Accepted Answer

No work is done, so $$\Delta E_{\mathrm{int}} = Q$$

Question 10

A system undergoes a cyclic process. Which of the following statements is correct?

Accepted Answer

The net work done on the system per cycle equals the area enclosed by the path on a PV diagram.

Question 11

Which of the following best describes the mechanism of heat transfer by conduction?

Accepted Answer

Energy is transferred through collisions between microscopic particles within a material.

Question 12

The rate of energy transfer by conduction through a slab is given by which equation?

Accepted Answer

$$\frac{Q}{t} = kA \frac{\Delta T}{d}$$

Question 13

Which of the following statements about black bodies is correct?

Accepted Answer

A black body is an ideal absorber and an ideal radiator with emissivity $$e = 1.$$

Question 14

A thermodynamic system undergoes a process in which its internal energy decreases by $$500\ \mathrm{J}$$, and $$220\ \mathrm{J} of $$work is done on the system. What is the energy transferred from it by heat?

Accepted Answer

$$-720\ \mathrm{J}$$

Question 15

Which process is characterized by no energy transfer by heat and no work done, resulting in no change in internal energy?

Accepted Answer

Adiabatic free expansion

Question 16

Which of the following is the correct expression for the rate of energy emission by thermal radiation from a surface?

Accepted Answer

$$P = \sigma $$AeT^4$$

Question 17

A $$2.0\ \mathrm{kg}$$ block of ice at $$0\ ^\circ \mathrm{C} is $$melted by adding $$668\ \mathrm{kJ} of $$energy. What is the latent heat of fusion for ice?

Accepted Answer

$$L = 334\ \mathrm{kJ/kg}$$

Question 18

Which of the following is NOT a state variable in thermodynamics?

Accepted Answer

Heat

Question 19

Which of the following statements about isothermal processes is correct?

Accepted Answer

The internal energy does not change, so $$Q = -W.$$

Question 20

Which of the following best describes convection?

Accepted Answer

Energy transfer by the bulk movement of a fluid due to differences in density.

Chapter 20: The First Law of Thermodynamics – Internal Energy, Heat, and Energy Transfer

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