Course Webpage: http://panda.unm.edu/Courses/Thomas/Phys161fa11/P161Syllabus.htm Course Grading Policy Online homework due every class. Late HW 1/3 off per day! You will want to get Mastering Physics and an iClicker Registration info on the

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Course Webpage http//panda.unm.edu/Courses/Thoma
s/Phys161fa11/P161Syllabus.htmCourse Grading
PolicyOnline homework due every class. Late
HW 1/3 off per day! You will want to get
Mastering Physics and an iClickerRegistration
info on the webpage
2
How do most humans learn physics? Assisted
Struggling. you must try until your brain
hurts, and then our Specialiste Intellectual
(SI) Matt Curry (or yrs trly) can (we hope)
help. Why is so much pain involved? Answer
Pain wires the neurons. Wednesday Bring
clickers, Know your schedule, Vote for SI
scheduling.
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Lets Begin! Chapter 17 Pedagogical
GoalsUnderstand linear thermal
expansionMemorize Apply conversions between K,
C, FUnderstand that heat is energy transferred
owing to ?TCompute calorimetric equilibrium for
ice water mixesUnderstand conduction,
convection, radiationWritten HW Due Friday Aug
26 17-44,17-104
Most objects expand on heating. Demonstration
On heating the ring, the hole A will get
bigger, as it expands B will get smaller, as the
metal around expands inward
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• ANY smooth function, over a small range, looks
  like a line
• The length of a rod, when heated, MUST BE
• L L0 ?(T-T0)L0
• ? is the coefficient of linear expansion.
• What is the coefficient of volume expansion ?

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If you want to directly measure the expansion of
the temperature sensing liquid, use a
thermometer big bulb, very narrow
tube Daniel Gabriel Fahrenheit
(16861736) 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. If you put evenly spaced marks on the
thermometer, what assumption are you making???
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Galilean Thermometer Most objects expand on
heating. Since the mass stays the same, when an
object expands, what happens to its density? A
goes up B goes down C unchanged
Glass balls of different density nearly float
in oil Each ball is labeled with the temperature
at which it just floats. Consider a ball that is
just barely floating at 70F. If you heat the GT
to 72C, what happens? A the ball floats up
(more) B the ball sinks
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Gases also expand on heating.DemoThere
appears to be an ideal behavior of gases,
approached as the density is low and for certain
compositions (e.g. neon)Graph Volume vs T for
different samplesKelvin temperature
Units K
Memorize the above. The size of 1K 1C Note
hip scientists say Kelvin, not Degrees Kelvin
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What is the approximate boiling temperature of
water, in K?A 100 KB 212 KC 273 KD
373 KE 485 K
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Heat Energy transferred because of a
difference in temperature. Heat flows
spontaneously from a hotter object to a colder
object. It never flows spontaneously from a
colder object to a hotter one. It does not flow
between objects at the same temperature. Water
in a hot pan never spontaneously freezes, even
though it could do that without violating
conservation of energy!(if it made the pan even
hotter!)Specific Heat, c, is the amount of
heat needed to raise the temperature of a gram of
material a degree (or a Kelvin)
Qmc?????differential form dQ mcdT)Latent
heat (of vaporization, or of fusion) is heat per
gram of material needed to boil (vaporize) or
freeze (fuse). QmLAdding heat does not always
increase temperature!
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Conduction heat transfer by contact w/o bulk
motion Convection heat transfer by
heat-induced fluid flow around a hot object
(recall, air is a fluid.)
Radiation all objects above 0K radiate
electromagnetic waves Black body radiation. If
you put a rock in a vacuum box (in vacuum), the
rock will radiate and the box will radiate. If
the rock is hot, it will radiate more, and that
radiation will be absorbed by the walls of the
box, making the box hotter.
Color intensity depend on T
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Radiated energy increases with T (T4) Cooler
things are redder (humans are infrared, redder
than red), hotter things are bluer. All things
radiate a little less than this theoretical
limit. (To keep balanced, they also absorb a
little less!) Memorize.
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Mixing Ice Water
You must be able to solve these problems X g of
ice at -20C Y g of water at 0 are mixed in a
thermos. What is the equilibrium composition and
temperature? X g of ice at 0C Y g of water
at 60C are mixed in a thermos. What is the
equilibrium composition and temperature?
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An easy one to start with 10 g of ice at 0C
is mixed with 30 g of water at 0C in a
thermos. What is the equilibrium temperature and
composition? A 0C, 10 g ice, 30 g water B
0C, 20 g ice, 20 g water C 0C, no ice, all
water D 0C, all ice, no water E 0F, all
ice, no water
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Heat flows from hot to cold (energy is
conserved) Decision points! 20 g ice at 0C
is mixed with 40 g water at 80C in a
thermos. Without knowing the specific heat or
latent heat (except both are positive, of
course) What is the composition at
equilibrium? A It has to be all water B it
might be all water, OR ice water (but cannot be
all ice) C it might be all ice, OR ice water
(but cannot be all water) D it has to be all
ice E we can conclude nothing
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20 g ice at 0C is mixed with 40 g water at 80C
in a thermos. The hot water will give up heat to
the cold ice. The water will get colder, and the
ice will get melted. Eventually the process
described will END. (It may be followed by a
different process!) The process described HERE
will END because All the ice melts (in which
case, we are no longer taking heat from water and
putting it into melting ice) OR The water
reaches 0C (in which case, heat transfer stops.)
Either we end up with a mix of water ice, or
all water. We cannot decide YET.
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20 g ice at 0C is mixed with 14.2 g water at
80C in a thermos. Qmelt 6680 J (heat reqd
to melt ice) Q-gt0C 4768 J (heat reqd to cool
the hot water to 0C) How much heat is actually
transferred from the hot water to the ice? A
4768 J B 6680 J C 5724 J (average of AB)
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ANNOUNCEMENT THE OFFICE OF ACCESSIBILITY
RESOURCE CENTER IS LOOKING FOR A STUDENT IN THIS
CLASS TO VOLUNTEER TO PROVIDE NOTES FOR THIS
CLASS. THE STUDENT WILL BE PAID A STIPEND FOR THE
SEMESTER.  INTERESTED STUDENT SHOULD COME BY OUR
OFFICE AT 2021 MESA VISTA HALL TO COMPLETE THE
REQUIRED HIRING PAPERWORK.  Announcement 2 HW
due next Friday Chapter 18 exercises 10, 14,
42 ANNOUNCEMENT 3. YOUR PROFESSOR DOES NOT SEEM
TO MULTIPLY WELL. LETS REVISIT 20g ice at 0C
40 g water at 80C With the correct
multiplication, what is the final
composition? A all water B a mix of water
ice
SI Problem Sessions T 3-4 W 12-2 Th
5-630 Regener 111
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For the next three weeks, we will study gases. We
will figure out what happens when you heat them,
and what happens when you compress them.
Why? Heres a question, true or false Heat
never flows from a cold object to a hot one. A
True B False While you think about this
question, dont mind me Im just going to have a
popsicle!
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Heres a question, true or false Heat never
flows from a cold object to a hot one. A
True B False
The popsicle was made by extracting heat from
cold (flavored) water and adding it into my
warmer kitchen. Heat never spontaneously flows
from a cold object to a hot one. But we can use a
freezer (or refrigerator) to move heat from cold
objects to warm.
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We will study gases to understand how to use them
as a working substance in a refrigerator.
Along the way, perhaps we can gain a better
understanding of the limits of refrigerator
performance, and the limits of engine
performance. We will discover that there is a
limit to the efficiency of each that limit
results from the fact that Heat never
spontaneously flows from a cold object to a hot
one.
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P F/A Gauge pressure pressure above ambient
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The ideal gas law works only and exclusively with
T in Kelvin.
Pressure can be measured in N/m2, or in atm. (1
atm 105 N/m2) Volume can be measured in m3,
or in liters. (1000 liters 1 m3) n is number
of moles R is the gas constant, 8.3 J/(molK)
0.082 Latm/(molK)
Remember the IJK rule, the Ideal gas law
in Jims class requires Kelvin temperature
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• An ideal gas occupies 1 liter at 32F and 1 atm
  pressure. If the volume is held fixed, at about
  what temperature will the pressure be 2 atm?
• A 64F
• B 100C
• C 273C

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• An ideal gas occupies 1 liter at 32F and 1 atm
  pressure. If the volume is doubled and the
  temperature raised to 273C, what happens to the
  pressure?
• A it is reduced to 1/4 atm
• B it is reduced to 1/2 atm
• C it stays the same
• D it increases to 2 atm
• E it increases to 4 atm

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SI Problem Sessions T 3-4 W 12-2 Th
5-630 Regener 111
Correction to SI Schedule
For a monatomic ideal gas, we can show that the
product pV 2/3 of the translational kinetic
energy of the molecules, Ktr! So nRT
(2/3)Ktr Temperature is proportional to the
kinetic energy per molecule.