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3, 9 Thermal
Physics
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Section Number
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Topic
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Descriptor
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Topic 3:
Thermal Physics (11h)
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3.1 Thermal
Concepts (3h)
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Temperature and
thermometers
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3.1.1
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State that temperature is a
property that determines the direction of thermal
energy transfer between two
bodies in thermal contact.
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Students should be
familiar with the concept of thermal equilibrium.
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3.1.2
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Explain how a temperature
scale is constructed.
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3.1.3
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State the relation between the
Kelvin and Celsius scales of temperature.
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T /K = t /
¡
C+ 273 is
sufficient.
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Heat and
internal energy
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3.1.4
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State that temperature is a
measure of the average kinetic energy of the
molecules of a
substance.
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3.1.5
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State that internal energy is
the total potential and kinetic energy of
molecules in a
substance.
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Students should know
that the kinetic energy of the molecules arises from
their
translational/rotational motion and that the potential
energy of the molecules
arises from the forces between the molecules.
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3.1.6
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Explain and distinguish
between the macroscopic concepts of temperature,
internal energy and
heat.
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Thermal energy
transfer
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3.1.7
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Describe qualitatively, the
processes of conduction, convection and
radiation.
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3.1.8
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Describe examples of
conduction, convection and radiation.
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3.2 Thermal
Properties of Matter (5h)
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Specific heat
capacity
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3.2.1
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Define and distinguish between
heat capacity and specific heat
capacity.
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3.2.2
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Explain why different
substances have different specific heat
capacities.
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This should be
understood in terms of the fact that unit masses of
different substances
contain different numbers of molecules of different
mass.
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3.2.3
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Describe methods to measure
the specific heat capacity of solids and liquids.
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The electrical
method and the method of mixtures are sufficient. The
cooling correction
is not included in the calculation. Sources of experimental
error should be
identified and ways to reduce these should be known.
Constant flow
techniques are not required.
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3.2.4
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Solve problems involving
specific heat capacities.
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Phases (states) of
matter and latent heat
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3.2.5
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Describe the solid, liquid and
gaseous states in terms of molecular structure
and motion.
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Only a simple model
is required. The speed distribution in gases should
be explained
qualitatively. Students should be aware how
microscopic structure
explains bulk behaviour.
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3.2.6
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Describe and explain the
process of phase changes in terms of molecular
behaviour.
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3.2.7
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Explain in terms of molecular
behaviour why temperature does not change
during a phase change.
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3.2.8
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Define specific latent
heat.
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3.2.9
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Describe a method for
measuring the specific latent heat of fusion and a
method for measuring the specific
latent heat of vaporization.
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Adding ice to water
in a calorimeter would be suitable for fusion and an
electrical method would
be suitable for vaporization.
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3.2.10
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Solve problems involving
specific latent heats.
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Problems may include
all three phases of a substance and specific heat
calculations.
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3.2.11
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Describe the evaporation
process in a liquid in terms of molecular
behaviour.
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Students should be
aware that evaporation takes place at all
temperatures and
results in the cooling of a liquid.
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3.2.12
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Identify factors that affect
evaporation rate.
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3.3 Ideal Gases
(3h)
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Gas
laws
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3.3.1
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State the macroscopic gas laws
relating pressure, volume and temperature.
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Students should be
aware that real gases deviate from these laws under
certain conditions and
that an ideal gas is one that follows the gas laws
for all values
of p, V and T.
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3.3.2
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Define the terms mole
and molar mass.
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Students should be
able to convert between mass and number of moles.
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3.3.3
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Define the Avogadro
constant.x
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3.3.4
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State that the equation of
state of an ideal gas is pV =
nRT.
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3.3.5
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Describe the concept of the
absolute zero and the Kelvin scale.
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3.3.6
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Solve problems using the
equation of state of an ideal gas.
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Kinetic model
of an ideal gas
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3.3.7
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Describe the kinetic model of
an ideal gas.
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Students should be
able to describe how the pressure arises from the
collisions of the
molecules with the walls of the container.
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3.3.8
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Explain the macroscopic
behaviour of an ideal gas in terms of the molecular
model.
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Only qualitative
explanations are required.
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Topic 9:
Thermal Physics (6h)
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9.1
Thermodynamic Systems and Concepts (1h)
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Note: Although there are
many thermodynamic systems, in this sub-topic
discussion will be restricted to
a fixed mass of an ideal gas.
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9.1.1
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Explain what is meant by
thermodynamic system.
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Students should
recognize the distinction between a system and its
surroundings.
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9.1.2
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Describe the concepts
heat, work and internal
energy.
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The descriptions
should include the expansion and compression of an
ideal gas as an
example.
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9.1.3
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Deduce an expression for the
work involved in a volume change of a gas at
constant pressure.
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9.2 Processes
(4h)
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The first law
of thermodynamics
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9.2.1
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State the first law of
thermodynamics.
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9.2.2
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State that the first law of
thermodynamics is a statement of the principle of
energy conservation.
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9.2.3
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Describe the isochoric
(isovolumetric), isobaric, isothermal and adiabatic
processes.
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I n each process the
heat transferred, the work done and internal energy
change should be
addressed. The ideal gas equation of state should be
applied to all
processes except the adiabatic. Students should realize that
a rapid
compression or expansion of a gas is approximately
adiabatic.
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9.2.4
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Draw and annotate
thermodynamic processes and cycles on p-V
diagrams.
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9.2.5
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Calculate the work done in a
thermodynamic cycle from a p-V diagram.
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9.2.6
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Solve problems involving state
changes of a gas.
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Heat engines
and heat pumps
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9.2.7
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Outline the concept of the
heat engine and the heat pump.
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9.2.8
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Draw and annotate schematic
diagrams of a heat engine and a heat pump.
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Energy transfer
paths should be shown.
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9.2.9
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Define the term thermal
efficiency of a heat engine.
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9.2.10
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Draw and annotate the Carnot
cycle on a p-V diagram.
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Students should be
aware that the Carnot cycle produces the maximum
possible theoretical
efficiency of a heat engine operating between two
heat reservoirs.
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9.2.11
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State Carnot's
theorem.
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9.2.12
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State an expression for the
efficiency of a Carnot engine in terms of the
temperatures of the two
reservoirs.
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Discuss the
possibility of changing the thermal efficiency by altering
the reservoir
temperatures.
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9.2.13
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Solve problems involving heat
engines and heat pumps.
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9.3 Second Law
of Thermodynamics and Entropy (1h)
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9.3.1
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State that heat can be
completely converted to work in a single process, but
that continuous conversion of
heat into work requires a cyclical process and
the rejection of some
heat.
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9.3.2
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State the Kelvin-Planck
formulation of the second law of thermodynamics
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It is sufficient for
students to acknowledge the impossibility of
constructing a heat
engine operating in a cycle that does not transfer
energy to a cold
reservoir. Teachers might like to show that if this
were possible
then it would imply that energy can be transferred
spontaneously from
a cold to a hot reservoir. This leads to the Clausius
statement of the second
law.
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9.3.3
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Analyse situations in terms of
whether they are consistent with the first
and/or second law.
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9.3.4
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State that entropy is a system
property that expresses the degree of disorder
in the system.
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9.3.5
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State the second law in terms
of entropy changes.
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A statement that the
overall entropy of the universe is increasing will
suffice.
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9.3.6
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Discuss examples of natural
processes in terms of entropy changes.
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Students should
understand that although local entropy can decrease,
any process will
increase the total entropy of the system and
surroundings.
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9.3.7
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Discuss the idea of energy
degradation in terms of the second law.
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