2. Thermal Conduction …
Ideal Gas Law…
Kinetic Molecular Theory…
Thermodynamics…

5. Heat As Energy Transfer
(c) Specific heat
of the material
(Q) Thermal
energy added
(m) Mass of
the object
(ΔT) Change in
temperature m

6. Calorimetry Conservation of thermal energy: Final Temperature: m1 m2TL
Final Temperature:

7. Latent Heat
Energy is required for a material to change phase, even though its temperature is not changing.
(m) Mass of
the object
(L) Latent heat
of the fusion or
vaporization
(Q) Thermal
energy added

8. TL A TH Dx Thermal conductivity Surface constant area Heat transferred
Change in
temperature
Time for
transfer
Thickness

9. Hint ~ ratios

10. kB = Boltzmann’s Constant = 1.38 x 10-23 J/K = R/NA
The Ideal Gas Law
PV=nRT
P = Pressure (Pa)
V = Volume (m3)
n = # of moles (mol)
R = 8.31 J/mol K
= (L.atm)/(mol.K)
If N = # of particles
T = Temp. (K) B
PV=NkBT
PV = nRT = NkBT
kB = Boltzmann’s Constant = 1.38 x J/K = R/NA

11. Consider the way pressure changes with temperature in a gas:
Gay-Lussac’s Law P α T
Pressure
Temperature
Gas 1
Gas 2
Pressure must always be greater than zero
So temperature can never go below this point:
T = ° C = Absolute Zero

12. Fluids?

13. PV=nRT PV=nRT Ideal Gas at Constant Temperature (Isothermal)
PV=constant
Boyle’s Law
constant
PiVi= PfVf or
Ideal Gas at Constant Pressure
Charles’ Law
PV=nRT
constant or

15. What about the speeds of the molecules in an ideal gas……
This molecule has an average speed
This one has a different average speed
What about the Kinetic Energy of a gas molecule? m v
KE = ½mv2
What about the average Kinetic Energy of a group of gas molecules?
KE = ½mvrms2

16. Kinetic Theory B Average KE of an ideal gas molecule
Temperature is a measure of the average molecular kinetic energy
(k = Boltzmann’s constant = 1.38 x J/K)
Kelvin temperature
So now you can relate the mass, speed, and temperature of molecules in an ideal gas: B
Temperature is simply a measure of the average Kinetic Energy of the molecules of a substance.
A single molecule has no temperature since temperature is an averaging effect.

18. Maxwell Distribution Curves

19. Why?

21. U W Q Walls can be either: Diathermal - heat can flow through
Surroundings
System U W Q
Walls can be either:
Diathermal - heat can flow through
or Adiabatic – heat can’t flow through
Car engine
Q W
Rub hands together
W Q

22. The internal energy of an ideal gas depends only on its temperature
The internal energy of an ideal gas depends only on its temperature. Therefore, the change in internal energy of a fixed amount of ideal gas (n moles) is given by:
Units: Joules (J) R = 8.31 J/mol K

23. 1st Law of Thermodynamics
The total increase in the internal energy of a system is equal to the ‘sum’ of the work done on the system or by the system and the heat added to or removed from the system.
(Conservation of Energy!)
+ve Q = system GAINS heat
-ve Q = system LOSES heat

24. Pressure, Volume ,Temperature & Work
In Thermodynamics we talk about the state of the system:
Pressure, Volume ,Temperature & Work
Work Done on a Gas F
W = F Dx
DV = A Dx
W= PA Dx
W = -P DV Dx
Area
+ve W=work done ON system
COMPRESSION OF GAS DV
-ve W=work done BY system
EXPANSION OF GAS

25. Pressure - Volume GraphT4 T3
Isotherms
(lines of constant
temperature) T2 P T1
Area under curve represents work
Pressure
Internal energy
is proportional
to temperature
Volume
T4 >T1 V

26. Isobaric (Constant Pressure)
Expansion
W = -PDV Po
W = -ve
DU increases T4 T3 T2
1st Law:
DU = Q + W T1 DV V
ΔV = +ve
T4 >T1

27. Isovolumetric or Isochoric (Constant Volume)P
W = 0
Decrease in Pressure Po Pf
DU decreases
1st Law:
Q = DU T3 T2 T1
DU = Q + W V

28. Isothermal (Constant Temperature)
Expansion P Po
so W is -ve
(ie gas is expanding) T3 Pf
DU = 0 T2
1st Law:
DU = Q+W
0 = Q+W
Q = -W = (-)(-) = +ve!
i.e. the work done is provided by Q added T1 Vo Vf V

29. Adiabatic (No Heat Exchange)P Po Pf Vo Vf
W = DU
Compression
W = +ve
DU = increases T2
1st Law:
Q = 0
DU = W T1 V

33. 2nd Law of Thermodynamics
Higher Temperature
Lower Temperature
Heat
Heat will not flow spontaneously from a lower temperature object to a higher temperature object.

34. Heat Engine – any device that uses heat to do workQH
(input heat)
Conservation of Energy:
QH = W + QC
W (Work) QC
(rejected heat)

35. 2nd Law of Thermodynamics (Entropy form)
Reversible Process – when the system and its surroundings can return to the exact states they were in before the process.
P1 , V1 , T1
P2 , V2 , T2
P1 , V1 , T1
For a Reversible Process S = 0
For an Irreversible Process S > 0
2nd Law of Thermodynamics (Entropy form)
Entropy (S)
a measure of disorder