Conceptual Physics

Chapter 20 Problems

Conceptual Problems

C.1 A gas is enclosed in a container whose walls are made of a material that is flexible and which acts as a perfect insulator for
all practical purposes. A thermal process takes place on the gas. What would be the best model for the type of process?

i. Constant-volume

ii. Isobaric

iii. Adiabatic

iv. Isothermal

C.2 A gas is sealed in a container with rigid walls that allow heat to flow through them. A thermal process takes place on the gas.
What would be the best model for the type of process?

i. Constant-volume

ii. Isobaric

iii. Adiabatic

iv. Isothermal

Section Problems

Section 0 - Introduction

0.1 Use the simulation in the interactive problem in this section to answer the following questions. (a) What is the relationship
between the amount of heat transferred to the gas and the change in the internal energy of the gas during the first process
when the volume is fixed? (b) How do the values for the work and change in internal energy relate during the second process
when no heat flows in or out of the gas? (c) In general, how does the amount of heat transferred to the gas relate to the
change in internal energy and the work it does?
(a) The heat is i. greater than
ii. equal to
iii. less than

the change in internal energy.

(b) The work done is i. equal to

ii. the negative of

the change in internal energy.

(c) The net heat transferred is i. greater than

ii. equal to

iii. less than

the sum of the change in internal energy and the work done.

Section 1 - First law of thermodynamics

1.1 In the gym, you do a workout routine that causes you to lose 3.4×10^5 J of heat while performing 1.7×10^5 J of work. With
yourself as the system, state the following quantities for the first law of thermodynamics, with the appropriate signs: (a) Q, (b)
ǻEint, (c) W.

(a) J

(b) J

(c) J

1.2 A system performs 356 J of work on its surroundings while losing 133 J of internal energy. Determine the heat transferred to
the system during this process.
J

1.3 A sealed container of gas with a piston is well-insulated, so that no heat is transferred to it or from it. The gas performs
1700 J of work on its surroundings. What is its change in internal energy?
J

1.4 An ideal monatomic gas is held in a well-insulated container with a piston, so that no heat is transferred to it or from it. There
are 1.75 moles of gas in the container. During a process, the temperature of the gas increases from 297 K to 353 K. (a) What
is the work associated with the process? Make sure to include the correct sign. (Hint: there is an equation in the chapter on
the Kinetic Theory of Gases for the internal energy of an ideal monatomic gas that will help you solve this problem.) (b) Is
work done on the gas, or does the gas do work on its suroundings?
(a) J
(b) i. Work is done on the gas
ii. Work is done by the gas

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