Name _____________________
Heat and Thermodynamics Notes
3/10/09
Beta Physics Class Notes
Heat and Thermodynamics
Chapter 14: Heat
Major Topics
Thermal energy, internal energy, heat
Specific heat, calorimetry
Heat transfer mechanisms
Conduction, convection, radiation
In Textbook
READ
Sections 14.1

14.2, 14.4

14
.9
Lab:
Newton’s Law of Cooling
Problem Set 14:
pp. 438

442 Q 26, 28; Problems 3, 9, 15, 23, 51
Chapter 15: Thermodynamics
Major Topics
Laws of Thermodynamics
Heat Engines
Applications like heat pumps, refrigerators, engines
In Textbook
READ
Sec
tions 15.1

15.2, 15.4

15.9
Presentations:
Small group PowerPoints on thermo applications
Problem Set 15:
pp. 471

4 Q 8, 15, 19, p. 473, Problems 17, 19, 24, 52
Equations and conversion factors for Heat and Thermodynamics
GPE = mgh
Q = mc∆T
K = ºC + 273.15
1 calorie = 4.186 J
Heat and Thermodynamics Class Notes
p.
2
Mechanical Equivalent of Heat
Joule's apparatus for measuring the mechanical equivalent of heat.
“In 1845, the English physicist James Joule wrote a paper on the mechanical equiv
alent of
heat for the British Association meeting in Cambridge. In this work, he reported his best

known experiment, in which the work released through the action of a "weight falling
through a height" was used to turn a paddle

wheel in an insulated barrel
of water.
In this experiment, the friction and agitation of the paddle

wheel on the body of water
caused heat to be generated which, in turn, increased the temperature of wat
er. Both the
temperature change ∆T of the water and the height of the fall ∆h of the weight mg were
recorded. Using these values, Joule was able to determine the mechanical equivalent of
heat.”
http://schools

wikipedia.org/wp/w/Work_%2528thermodynamics%252
9.htm
Mechanical Energy
A 10.0 kg weight drops 2.0 m. What is
the potential energy of the weight before
if falls?
How much work does the falling weight
do?
If the energy transfer is 100% efficient,
what is the kinetic energy of the paddle
wheel?
Heat
The barrel of water contains 20.0 g of
water, which has a specific heat of 1.0
cal/g ºC. The water temperature
increases by 2.35 ºC. How many calories
of heat were transferred to the water?
Mechanical Equivalent of Heat =
Heat and Thermodynamics Class Notes
p.
3
Im
portant terms and concepts for Chapter 14 & 15
Definition
Equation
Units
Thermal Energy
Internal Energy
Heat
Temperature
Specific Heat
Calorimetry
Heat of Fusion
Heat of Vaporization
Conduction
Convection
Radiation
What is the
difference between heat and temperature?
How does heat transfer and why?
What are the possible units of heat and energy and how are they
related?
How do you measure heat changes?
Heat and Thermodynamics Class Notes
p.
4
What happens when you add heat to a solid?
What happens
From A to B
Fro
m B to C
From C to D
From D to E
From E to F
What do you notice
about phase changes?
Label this graph
with the
numbers and letter of the
problems below, to show
what part of the graph
represents the changes you
are calculating.
http://china

heatpipe.n
et/heatpipe04/08/2008

1

31/Lat ent_Heat.htm
Questions About Heat
1.
You went to the big box store Thermo City and bought 10.0 kJ of heat, on sale.
A. If you used your heat to increase the temperature of 250 g of water at 1ºC, what final
temperature woul
d it reach?
B. How hot would a 250 g block of aluminum at 1ºC get, if you used your heat to
increase its temperature?
C.
What is the difference between water and aluminum, that accounts for the difference
in the final temperature?
2.
You retur
ned to Thermo City and bought 10.0 kJ more heat, to continue your fun.
Heat and Thermodynamics Class Notes
p.
5
A. If you used your heat to melt ice to liquid water at 0ºC, how many grams of ice could
you melt?
B
If you used your heat to vaporize liquid water to water vapor at 100ºC, ho
w many
grams of water could you vaporize?
C.
If you needed it, how could you get your 10.0 kJ of heat BACK, at the end of your
experiments in parts A and B?
http://www.thesciencedesk.com/studyguidephasechanges.htm
Heat and Thermodynamics Class Notes
p.
6
Heat Transfer Mechanisms
http://www.beodom.com/en/journal/entries/principl es

of

thermal

i nsulation

heat

transfer

via

conduction

convection

and

radi ation
What are the 3 mechanisms for heat transfer and how do they work?
1.
2.
3.
Heat Transfer Questions
1.
Sea breezes are oft
en encountered on sunny days at the shore of a large body
of water. Explain in light of the fact that the temperature of the land rises more
rapidly than that of the nearby water.
2.
Why is the liner of a thermos bottle silvered (Fig. 14
–
15), and why doe
s it have a
Heat and Thermodynamics Class Notes
p.
7
vacuum between its two walls?
3.
A piece of wood lying in the Sun absorbs more heat than a piece of shiny metal.
Yet the wood feels less hot than the metal when you pick it up. Explain.
http://www.aos.wisc
.edu/~aalopez/aos101/wk5.html
Heat and Thermodynamics Class Notes
p.
8
Newton’s Law of Cooling
Newton's law of cooling, states that the _________ of heat loss of a body is proportional to the
difference in ______________ between the body and its surrounding. The law will allow you to
predict the
temperature after time has elapsed.
The mathematical form of Newton’s Law of Cooling is
In your lab, you fit your data to a __________________ function.
The constant k is related to the system’s __________________, ___________________ and
___________
_________.
This graph compares the temperature change with time when you add cream to your coffee.
How can your keep your
coffee as hot as possible?
http://www.kritzinger

home.com/cooling.html
Heat and Thermodynamics Class Notes
p.
9
http://www.grc.nasa.gov/WWW
/K

12/airplane/thermo.html
What are the 3 Laws of Thermodynamics?
1.
2.
3.
Heat and Thermodynamics Notes
p.
14
Chapter 15: Heat Engine Review Questions and Problems
1.
Explain what this diagram illustrates about heat
engines. Give a specific example of the
reservoirs, the source
and loss of heat, and the
work done. What does this diagram have to do
with the 2nd Law of thermodynamics?
2.
What is the maximum efficiency of a heat engine with a high T reservoir at 401 K
and a low T reservoir at 273 K?
3.
Explain what type of devi
ce this diagram
illustrates. Give a specific example of the
reservoirs, the source and loss of heat, and the
work done.
4.
How can the above device move heat from a low to a high temperature region?
What law of thermodynamics says how this can be acco
mplished? (Hint: Find
the Clausius statement of this law, for the most complete answer).
Heat and Thermo Cl ass Notes
p.
15
Chapter 14: Heat Review Questions and Problems
1.
How much heat (in joules) is required to raise the temperature of 30.0 kg of
water from 15°C to 95°C?
2.
A water h
eater can generate
How much water can it heat from 15°C
to 50°C per hour?
3.
If you add some heat to a substance, is it possible for the temperature of the
substance to remain unchanged? Explain.
4.
An “emergency blanket” is a thin
shiny (metal coated) plastic foil. Explain how
it can help to keep an immobile person warm.
5.
Given your experience of what feels colder when you walk on it, which of the
surfaces would have the
highest thermal conductivity?
a
a
.
.
a rug
b.
a steel surface
c.
a concr
ete floor
d.
has nothing to do with thermal conductivity
6.
On his honeymoon, James Joule attempted to explore the relationships
between various forms of energy by measuring the rise of temperature of
water which had fallen down a waterfall on Mount Blanc. Wh
at maximum
temperature rise would one expect for a waterfall with a vertical drop of 20 m?
a.
0.047 C°
b.
0.053 C°
c.
0.064 C°
d.
0.071 C°
7.
Convection can occur
a.
only in solids.
b.
only in liquids.
c.
only in gases.
d.
only in liquids and gases.
e.
in solids, liquids
, and gases
.
Heat and Thermo Cl ass Notes
p.
16
I want YOU to study for the Chap. 14 & 15 test
To prepare for the test, you should
1.
Complete the 14 & 15 homework.
2.
Do all the problems in the class
notes handout.
3.
Review the Introduction to Heat
and Thermo page.
4.
Do the Reality Check questi
ons
and problems.
5.
Go over your Newton’s Law of
Cooling Lab.
6.
Review the appropriate sections of
your textbook
Terms and Concepts
Internal energy, thermal energy, heat, temperature, specific heat, mechanical
energy, latent heat, entropy
Specific Heat and Ca
lorimetry
Q = mc∆T, calculating temperature change for given amount of heat, calculating
specific heat, comparing materials with different specific heats
Energy Transformations
PE, KE, and W to heat calculations, molecular mechanism of friction, units of
heat and en
ergy and interconversion, mechanical equivalent of heat
Heat Transfer Mechanisms
Conduction, convection, and radiation mechanisms and examples
How can you reduce or increase each type of heat transfer?
Newton’s Law of Cooling
T = (T
0

T
room
)e
–
kt
+ T
room
gra
ph and equation
Calculate T at given t and t for given T
Explain meaning of k, how to change its value, 2 ways to change cooling rate
Laws of Thermodynamics
State 0
th
, 1
st
, 2
nd
, and 3
rd
and give an example that illustrates each
Calculations using 1
st
Law
Q
in
= W + Q
out
Entropy concept and 2
nd
Law
Heat Engine
Diagram with hot and cold reservoirs, work done, example engine
Calculating the efficiency using Eff = 1
–
T
c
/T
h
What is the limit of efficiency and why?
Applications of Thermodynamics
How they work:
refrigerator, air conditioner, heat pump, heat engine
Relate to 1
st
and 2
nd
Law, draw heat engine diagram
How do heat engine and refrigerator differ? How are they the same?
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