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http://panda.unm.edu/Courses/Thomas/Phys161fa10/P161Syllabus.htm
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You will want to get Mastering Physics and an iClicker
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Key Points:
Seven Midterms (Drop lowest score)
No makeup exams
Scantron but NOT multiple choice
Model Exams Posted at least 2 weeks before midterm
0.1% of missed exam points for each problem done/ clicker quiz
(up to a maximum of 50%)
Chapter 17 Young&Freedman
Some things are hot, some things are cold.
Heating (usually) causes expansion.
In thermal contact, two objects (eventually) reach the
same temperature.
Daniel Gabriel Fahrenheit (1686–1736)
Fahrenheit temperature:
The zero point was determined by placing the thermometer in
brine: a mixture of ice, water, and ammonium chloride, a salt. This
is a frigorific mixture.
96 degrees, was the level of the liquid in the thermometer when
held in the mouth or under the armpit of his wife.
Celsius used ice/water and water/steam for 0 and 100.

Gases also expand on heating.
Demo
Kelvin temperature
9
TF  TC  32
5
TK  TC  273.15
Units: K
The ‘size’ of 1K = 1°C
What is the approximate boiling temperature of
water, in K?
A] 100 K
B] 212 K
C] 273 K
D] 373 K
E] 485 K
Solids also (usually) expand on heating.
If I heat this metal annulus,
The hole will:
A] get smaller
B] get bigger
C] stay the same size
Last time:
Heat = Energy
(that is transferred because of a difference in temperature).
[The temperature difference may be VERY small!]
“Specific Heat”, c, is the amount of heat needed to raise the
temperature of a mass of material a degree (or a Kelvin)
Q=mc
“Latent heat” (of vaporization, or of fusion) is heat per mass
of material needed to boil (vaporize) or freeze (fuse).
Today: equilibration of water & ice
mechanisms of heat transfer
Mixing Ice & Water
Mechanisms of heat transfer
1. Conduction
2. Convection (flow of fluid, like air)
3. Radiation
Two square (in cross-section) glass rods
connect very large copper blocks held at
different temperatures.
Which rod conducts heat faster?
A] Rod A
B] Rod B
C] They conduct heat at the same rate
Radiation.
Hot objects emit light (glowing red hot, white hot, light bulb
filaments, etc.)
dQ
4
 AeT
dt
Room temp: infrared emission
e = emissivity, e=1 is a ‘BLACK BODY’
Very hot: white emission
VV hot: blue
We can measure (approximately) the
temperature of an object by looking at
its black body spectrum. (This
assumes that emissivity is
independent of wavelength, which is
often nearly true.)
If an object can emit EM radiation (light, or infrared or UV etc.),
then it must also absorb EM radiation.
Consider an object in a vacuum box with perfectly reflective walls at
temperature T. In thermal equilibrium, the object is emitting
radiation:
dQ
4
 AeT
dt
Since it does not change temperature, it must absorb the same
amount of radiation.
So e= emissivity = absorptivity!
Black objects heat up faster in the sun, but cool off faster at night!

The ideal gas law:
A] Works with T (temp) in celsius or Kelvin, but you
need to use a different R for each.
B] Works with T in °C, °F, or K, but you need to use
a different R for each.
C] Works with T in °C or K, but if you use °C you
need to use the “gauge pressure”, not absolute
pressure
D] Works only and exclusively with T in Kelvin.
An ideal gas at 200 K occupies 2 liters at a pressure of 1 atm.
If the gas is compressed to 1 liter of volume, what will be its
temperature?
A] 200 K
B] 400 K
C] 800 K
D] There is not enough information to determine this!
An ideal gas at 200 K occupies 2 liters at a pressure of 1 atm.
If the gas is compressed to 1 liter of volume, and the pressure
is 2 atm, what will be its temperature?
A] 200 K
B] 400 K
C] 800 K
D] There is not enough information to determine this!
20 liters of Argon are in thermal equilibrium with 20 liters of Helium.
(These are monatomic gases, Mar=40, Mhe=4.)
Which molecules have more kinetic energy, on average?
A] Argon
B] Helium
C] Both have the same
Which molecules are moving faster, on average? HELIUM
MON Aug 30
Memorize!
V2
W= Work Done BY a Gas =
 pdV
V1

When gas does work, it loses
internal energy
(unless energy is added, via
heat.)
When it does negative work, it
gains internal energy
A gas in a piston is taken from state 1 to state 2. The outside
pressure is higher than the pressure in the cylinder.
For which path does the gas do the largest positive work? A
Or choose
E] no path does
work of this sign
For which path does the gas do the most negative work?
(I.e. for which path is the most work done ON the gas)
In the isobaric process shown, Q is: +
In the isobaric process shown, W is: +
In the isobaric process shown, U is: +
A] +
B] C] 0
D] cannot determine
In the isochoric process shown, Q is: In the isochoric process shown, W is: 0
In the isochoric process shown, U is: A] +
B] C] 0
D] cannot determine
Wed Sept 1
In the isothermal process shown, Q is: +
In the isothermal process shown, W is: +
In the isothermal process shown, U is: 0
A] +
B] C] 0
D] cannot determine
Let’s do this quantitatively.
On expanding isothermally from 2L to 4L, an ideal gas does 6J of work,
as the pressure drops from 2 atm to 1 atm.
By how much must it expand to do an additional 6J of work?
A] It must expand an additional 2L, to reach 6L
B] It must double again, to 8L
C] It must increase four-fold, to 16L
D] It can do no more work, as it has reached 1 atm.
E] Cannot determine without knowing T
In the mystery path process shown, Q is: D
In the mystery path process shown, W is: D
In the mystery path process shown, U is: 0
A] larger than for an isothermal
process from A->B
B] smaller than for an isothermal
process from A->B
C] 0
D] cannot determine
How much work is done when an ideal gas is expanded
from V1 to V2 at constant pressure?
A] 0
B] nRT2
C] nRT1
D] nR(T2-T1)
E] it depends on whether is it monatomic or diatomic.
What is the difference in internal energy of the gas at
points 1’ and 2 ? A
For ONE cycle:
For the cyclic process shown, Q is: D
For the cyclic process shown, W is: D
For the cyclic process shown, U is: A
A] 0, because it’s a loop
B] p0V0
C] - p0V0
D] 2 p0V0
E] 6 p0V0
Fri sept 3
For the constant pressure ideal gas process shown,
The change in internal energy U of the gas is
A] nCv
B] nCp
C] 0
D] cannot determine
If the gas is monatomic and ideal,
for the constant pressure process shown,
the change in internal energy can also be expressed as:
A] pV
B]
1
2
pV
C]
3
2
pV
D]
5
2
pV
(use a paper & pencil)
A non-ideal gas is taken from A to B.
The gas does 3 J of work; 6 J of heat is added to the gas.
What is the internal energy of the gas at B?
A] 3 J
B] 9 J
C] 10 J
D] cannot determine,
since gas is non-ideal
E] the numbers given are
not physically possible
A non-monatomic ideal gas is taken from A to B.
The gas does 3 J of work; 6 J of heat is added to the gas.
What is the internal energy of the gas at B?
A] 3 J
B] 9 J
C] 10 J
D] cannot determine,
since gas is non-monatomic
E] the numbers given are
not physically possible