Thermal Physics Questions
Thomas Russell
Question: State the first law of thermodynamics
Answer: The heat added to a closed system equals the change in the internal energy of the system plus the work done by the system OWTTE
Question: State two characteristics of an ideal gas
Answer: Any two of the following - There are no intermolecular forces between the gas particles; There is no loss of collision when the molecules collide;
Constant, rapid and random motion
Question: What is the difference between an Isothermal process and an Adiabatic process?
Answer: An Isothermal process is one in which the pressure and volume are varied and the temperature is constant in the system and an Adiabatic process
is one in which no heat leaves or enters the system and hence Q=0. OWTTE
Question: If 52J of work is done on a system and 364J of heat is added, determine the change of internal energy of the system
Answer: 416J
Question: State the second law of thermodynamics
Answer: The total entropy of any system plus that of its environment increases as a result of all natural processes OWTTE
Thermal Physics Questions
Thomas Russell
Topic 10
Thermal Physics
10.1 Thermodynamics
10.1.1 State the
Equation of state
for an ideal gas
PV=nRT
P=Pressure
V=Volume
n=Number of
moles
R=gas constant
8.31 J mol-1 K-1
T=Temperature
(K)
10.1.2 Describe
the difference
between an ideal
gas and a real gas
An ideal gas
contains no
intermolecular
forces, no kinetic
energy is
transferred
through collisions
and all particles
move constantly,
rapidly and in a
random motion
10.1.3 Describe
the concept of
absolute zero and
the Kelvin scale of
temperature
Absolute zero is
the minimum
temperature as it
occurs at 0
pressure
according to the
Charles law. The
Kelvin scale has
the same scaling
as the Celsius
scale but is
273.15° lower
10.2 Processes
10.1.4 Solve
problems using
the equation of
state of an ideal
gas
TIP: Just use this:
PV=nRT
10.2.1 Deduce an
expression for the
work involved in a
volume change of
a gas at constant
pressure
𝐹
𝑝=
𝐴
𝐹 = 𝑝𝐴
∆𝑊 = 𝐹 × ∆𝑙
∆𝑊
= 𝑝 × 𝐴 × ∆𝑙
∆𝑊 = 𝑝 × ∆𝑉
10.2.5 Draw and
annotate
thermodynamic
processes and
cycles on a P-V
diagram
10.2.2 State the
first law of
thermodynamics
The heat added
to a closed
system equals
the change in
the internal
energy of the
system plus the
work done by
the system
𝑸 = ∆𝑼 + 𝑾
10.2.6 Calculate
from a P-V
diagram the
work done in a
thermodynamic
cycle
10.2.3 Identify
the first law of
thermodynamics
as a statement
of the principle
of energy
conservation
Within the
equation, all
energy transfers
are identified
and hence no
energy is created
or destroyed
10.2.7 Solve
problems
involving state
changes of a gas
10.2.4 Describe
the isochoric,
isobaric,
isothermal and
adiabatic
changes of state
of an ideal gas
IsochoricConstant volume
IsobaricConstant
Pressure
IsothermalConstant
Temperature
Adiabatic- No
heat flow in or
out of system
Thermal Physics Questions
Thomas Russell
10.3 The second law of
thermodynamics and entropy
The Carnot engine
10.3.1 State that the second law
of thermodynamics implies that
thermal energy cannot
spontaneously transfer from a
region of low temperature to a
region of high temperature
The Kelvin-Planck statement of
the 2nd LoT states that It is
impossible for an engine working
in a cycle to transform a given
amount of heat from a reservoir
completely into work.
10.3.2 State that entropy is a
system property that
expresses the degree of
disorder in the system
Entropy is a thermodynamic
function and can be
interpreted as the amount of
order or disorder of a system.
The change in entropy is
more important than its
absolute state
If this is true, then it can be said
that the opposite is true:
10.3.3 State the second law
of thermodynamics in terms
of entropy changes
Clausius statement: It is
impossible to make a cyclic
engine whose only effect is to
transfer thermal energy from a
colder body to a hotter body
The total entropy of any
system plus that of its
environment as a result of all
natural processes
∆𝑆 =
𝑄
𝑇
10.3.4 Discuss example of
natural processes in terms
of entropy changes
Note that while local
entropy in a system may
decrease, the entropy of
the system will usually
increase by a greater factor
due to that process.
 Heat death of the
universe- Degradation of
all energy to a non-useful
form
 A piece of ice can slide
down an incline if the
friction is overcome. In
this process mechanical
energy is converted into
non-useful thermal
energy through the
friction process.
Thermal Physics Questions
Thomas Russell