8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
1/56
PHYS222 LSSU Bazlur Slide 1
Chapter - 12
Temperature
and
Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
2/56
PHYS222 LSSU Bazlur Slide 2
Temperature and Heat
12.1 Common Temperature Scales
12.2 The Kelvin Temperature Scales12.3 Thermometers
12.4 Linear Thermal Expansion
12.5 Volume Thermal Expansion
12.6 Heat and Internal Energy
12.7 Heat and Temperature Change: Specific HeatCapacity
12.8 Heat and Phase Change: Latent Heat12.9 Equilibrium between Phases of Matter
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
3/56
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
4/56
PHYS222 LSSU Bazlur Slide 4
12.1 Common Temperature Scales
Temperatures are reported in degrees
Celsiusor degrees Fahrenheit.
Temperatures changed, on theother hand, are reported in Celsius
degrees or Fahrenheitdegrees:
F
5
9C1
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
5/56
PHYS222 LSSU Bazlur Slide 5
12.1 Common Temperature Scales
Example 1 Converting from a Fahrenheit to a Celsius Temperature
A healthy person has an oral temperature of 98.6o
F. What would thisreading be on the Celsius scale?
F6.66F32F98.6
degrees above ice point
C0.37F
C1F6.66
59
C0.37C0.37C0
ice point
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
6/56
PHYS222 LSSU Bazlur Slide 6
12.1 Common Temperature Scales
Example 2 Converting from a Celsius to a Fahrenheit Temperature
A time and temperature sign on a bank indicates that the outdoor
temperature is -20.0oC. Find the corresponding temperature on
the Fahrenheit scale.
F0.36C1
FC0.20 5
9
degrees below ice point
F0.4F0.36F0.32
ice point
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
7/56PHYS222 LSSU Bazlur Slide 7
12.2 The Kelvin Temperature Scale
15.273 cTT
Kelvin temperature
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
8/56PHYS222 LSSU Bazlur Slide 8
12.2 The Kelvin Temperature Scale
A con stant-volum e gas
thermometer.
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
9/56PHYS222 LSSU Bazlur Slide 9
12.2 The Kelvin Temperature Scale
abso lute zero po int = -273.15oC
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
10/56PHYS222 LSSU Bazlur Slide 10
12.3 Thermometers
Thermometers make use of the change in some physical property with temperature.
A property that changes with temperature is called a thermometr ic prop erty.
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
11/56PHYS222 LSSU Bazlur Slide 11
12.4 Linear Thermal Expansion
NORMAL SOLIDS
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
12/56PHYS222 LSSU Bazlur Slide 12
12.4 Linear Thermal Expansion
oLL
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
13/56PHYS222 LSSU Bazlur Slide 13
12.4 Linear Thermal Expansion
LINEAR THERMAL EXPANSION OF A SOLID
The length of an object changes when its temperature changes:
TLL o
coefficient of
linear expansion
Comm on Unit for the Coeffic ient of Linear Expansion: 1CC
1
12 4 Li Th l E i
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
14/56PHYS222 LSSU Bazlur Slide 14
12.4 Linear Thermal Expansion
12 4 Li Th l E i
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
15/56PHYS222 LSSU Bazlur Slide 15
12.4 Linear Thermal Expansion
Example 3 The Buckling of a Sidewalk
A concrete sidewalk is constructed between
two buildings on a day when the temperature
is 25oC. As the temperature rises to 38oC,the slabs expand, but no space is provided for
thermal expansion. Determine the distance y
in part (b) of the drawing.
12 4 Li Th l E i
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
16/56PHYS222 LSSU Bazlur Slide 16
12.4 Linear Thermal Expansion
m00047.0C13m0.3C1012 16
TLL o
m053.0m00000.3m00047.3 22 y
12 4 Li Th l E i
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
17/56PHYS222 LSSU Bazlur Slide 17
12.4 Linear Thermal Expansion
Example 4 The Stress on a Steel Beam
The beam is mounted between two
concrete supports when the temperature
is 23oC. What compressional stress
must the concrete supports apply to
each end of the beam, if they are
to keep the beam from expanding
when the temperature rises to 42oC?
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
18/56PHYS222 LSSU Bazlur Slide 18
12.4 Linear Thermal Expansion
2716211 mN107.4C19C1012mN100.2
Stress
TYL
LY
A
F
o
TLL o
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
19/56PHYS222 LSSU Bazlur Slide 19
12.4 Linear Thermal Expansion
THE BIMETALLIC STRIP
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
20/56PHYS222 LSSU Bazlur Slide 20
12.4 Linear Thermal Expansion
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
21/56PHYS222 LSSU Bazlur Slide 21
12.4 Linear Thermal Expansion
THE EXPANSION OF HOLES
Conceptual Examp le 5The Expansion of Holes
The figure shows eight square tiles that are arranged to form a square pattern
with a hold in the center. If the tiled are heated, what happens to the size of the
hole?
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
22/56PHYS222 LSSU Bazlur Slide 22
12.4 Linear Thermal Expansion
A hole in a piece of solid material expands when heated and contracts when
cooled, just as if it were filled with the material that surrounds it.
12 4 Linear Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
23/56PHYS222 LSSU Bazlur Slide 23
12.4 Linear Thermal Expansion
Conceptu al Examp le 7 Expanding Cylinders
Each cylinder is made from a different material.
All three have the same temperature and theybarely fit inside each other.
As the cylinders are heated to the same,
but higher, temperature, cylinder C falls
off, while cylinder A becomes tightly wedged
to cylinder B.
Which cylinder is made from which material?
12 5 Volume Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
24/56PHYS222 LSSU Bazlur Slide 24
12.5 Volume Thermal Expansion
VOLUME THERMAL EXPANSION
The volume of an object changes when its temperature changes:
TVV o
coefficient of
volume expansion
Comm on Unit for the Coeffic ient of Volum e Expansion : 1CC
1
12 5 Volume Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
25/56
PHYS222 LSSU Bazlur Slide 25
12.5 Volume Thermal Expansion
Example 8 An Automobile Radiator
A small plastic container, called the coolant reservoir, catches
the radiator fluid that overflows when an automobile enginebecomes hot. The radiator is made of
copper and the coolant has an
expansion coefficient of
4.0x10-4(Co)-1. If the radiator
is filled to its 15-quart capacitywhen the engine is cold (6oC),
how much overflow will spill into the
reservoir when the coolant reaches its
operating temperature (92oC)?
12.5 Volume Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
26/56
PHYS222 LSSU Bazlur Slide 26
12.5 Volume Thermal Expansion
quarts53.0C86quarts15C1010.4 14coolant V
quarts066.0C86quarts15C1051 16radiator V
quarts0.46quarts066.0quarts53.0spill V
12.5 Volume Thermal Expansion
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
27/56
PHYS222 LSSU Bazlur Slide 27
12.5 Volume Thermal Expansion
Expansion of water.
12.6 Heat and Internal Energy
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
28/56
PHYS222 LSSU Bazlur Slide 28
6 eat a d te a e gy
DEFINITION OF HEAT
Heat is energy that flows from a higher-
temperature object to a lower-temperature
object because of a difference in temperatures.
SI Unit of Heat: joule (J)
12.6 Heat and Internal Energy
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
29/56
PHYS222 LSSU Bazlur Slide 29
gy
The heat that flows from hot to cold
originates in the internal energy of
the hot substance.
It is not correct to say that a substance
contains heat.
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
30/56
PHYS222 LSSU Bazlur Slide 30
p g p p y
SOLIDS AND LIQUIDS
HEAT SUPPLIED OR REMOVED IN CHANGING THE TEMPERATURE
OF A SUBSTANCE
The heat that must be supplied or removed to change the temperature of
a substance is
TmcQ
specific heat
capacity
Common Unit for Specific Heat Capacity: J/(kgCo)
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
31/56
PHYS222 LSSU Bazlur Slide 31
p g p p y
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
32/56
PHYS222 LSSU Bazlur Slide 32
p g p p y
Examp le 9 A Hot Jogger
In a half-hour, a 65-kg jogger can generate 8.0x105
J of heat. This heatis removed from the body by a variety of means, including the bodys own
temperature-regulating mechanisms. If the heat were not removed, how
much would the body temperature increase?
TmcQ
C5.3CkgJ3500kg65
J100.8 5
mc
QT
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
33/56
PHYS222 LSSU Bazlur Slide 33
GASES
The value of the specific heat of a gas depends on whether the pressure or
volume is held constant.
This distinction is not important for solids.
OTHER UNITS
1 kcal = 4186 joules
1 cal = 4.186 joules
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
34/56
PHYS222 LSSU Bazlur Slide 34
CALORIMETRY
If there is no heat loss to the surroundings,
the heat lost by the hotter object equals theheat gained by the cooler ones.
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
35/56
PHYS222 LSSU Bazlur Slide 35
Example 12 Measuring the Specific Heat Capacity
The calorimeter is made of 0.15 kg of aliminumand contains 0.20 kg of water. Initially, the
water and cup have the same temperature
of 18.0oC. A 0.040 kg mass of unknown
material is heated to a temperature of
97.0o
C and then added to the water.
After thermal equilibrium is reached, the
temperature of the water, the cup, and the
material is 22.0oC. Ignoring the small amount
of heat gained by the thermometer, find
the specific heat capacity of the
unknown material.
12.7 Heat and Temperature Change: Specific Heat Capacity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
36/56
PHYS222 LSSU Bazlur Slide 36
unknownwaterAl TmcTmcTmc
CkgJ1300
C0.75kg040.0
C0.4kg20.0CkgJ4186C0.4kg15.0CkgJ1000.9 2
unknown
waterAlunknown
Tm
TmcTmcc
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
37/56
PHYS222 LSSU Bazlur Slide 37
THE PHASES OF MATTER
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
38/56
PHYS222 LSSU Bazlur Slide 38
During a phase change, the temperature of the mixture does not
change (provided the system is in thermal equilibrium).
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
39/56
PHYS222 LSSU Bazlur Slide 39
Conceptu al Example 13 Saving Energy
Suppose you are cooking spaghetti for dinner, and the instructions
say boil pasta in water for 10 minutes. To cook spaghetti in an open
pot with the least amount of energy, should you turn up the burner
to its fullest so the water vigorously boils, or should you turn down
the burner so the water barely boils?
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
40/56
PHYS222 LSSU Bazlur Slide 40
HEAT SUPPLIED OR REMOVED IN CHANGING THE PHASE
OF A SUBSTANCE
The heat that must be supplied or removed to change the phase
of a mass mof a substance is
mLQ
latent heat
SI Units of Latent Heat: J/kg
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
41/56
PHYS222 LSSU Bazlur Slide 41
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
42/56
PHYS222 LSSU Bazlur Slide 42
Example 14 Ice-cold Lemonade
Ice at 0oC is placed in a Styrofoam cup containing 0.32 kg of lemonade
at 27oC. The specific heat capacity of lemonade is virtually the same as
that of water. After the ice and lemonade reach and equilibrium
temperature, some ice still remains. Assume that mass of the cup is
so small that it absorbs a negligible amount of heat.
lemonadebylostHeat
lemonade
icebygainedHeat
iceTcmmLf
12.8 Heat and Phase Change: Latent Heat
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
43/56
PHYS222 LSSU Bazlur Slide 43
lemonade
bylostHeat
lemonade
icebygainedHeat
iceTcmmLf
kg11.0kgJ103.35C0C27kg32.0CkgJ4186
L
5
f
lemonadeice
Tcmm
12.9 Equilibrium Between Phases of Matter
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
44/56
PHYS222 LSSU Bazlur Slide 44
The pressure of vapor that coexists in equilibrium with the liquid is
called the equi l ibr ium vapor pressureof the liquid.
12.9 Equilibrium Between Phases of Matter
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
45/56
PHYS222 LSSU Bazlur Slide 45
Only when the temperature and vapor pressure correspond to a point
on the curved line do the liquid and vapor phases coexist in equilibrium.
12.9 Equilibrium Between Phases of Matter
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
46/56
PHYS222 LSSU Bazlur Slide 46
Conceptual Example 16 How to Boil Water That is
Cooling Down
Shortly after the flask is removed from the burner,
the boiling stops. A cork is then placed in the neck
of the flask to seal it. To restart the boiling, should
you pour hot or cold water over the neck of the
flask?
12.9 Equilibrium Between Phases of Matter
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
47/56
PHYS222 LSSU Bazlur Slide 47
12.9 Equilibrium Between Phases of Matter
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
48/56
PHYS222 LSSU Bazlur Slide 48
As is the case for liquid/vapor
equilibrium, a solid can be in
equilibrium with its liquid phase
only at specific conditions oftemperature and pressure.
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
49/56
PHYS222 LSSU Bazlur Slide 49
Air is a mixture of gases.
The total pressure is the sum of the part ial pressuresof the component
gases.
The partial pressure of water vapor depends on weather conditions. It
can be as low as zero or as high as the vapor pressure of water at the
given temperature.
100
retemperatuexistingatwaterofpressurevapormEquilibriu
orwater vapofpressurePartialhumidityrelativePercent
To provide an indication of how much water vapor is in the air, weather
forecasters usually give the relat ive hum idity :
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
50/56
PHYS222 LSSU Bazlur Slide 50
Example 17 Relative Humidities
One day, the partial pressure of water vapor is 2.0x103Pa. Using the
vaporization curve, determine the relative humidity if the temperature
is 32oC.
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
51/56
PHYS222 LSSU Bazlur Slide 51
100
retemperatuexistingatwaterofpressurevapormEquilibriu
orwater vapofpressurePartialhumidityrelativePercent
%42100Pa108.4
Pa100.2humidityRelative
3
3
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
52/56
PHYS222 LSSU Bazlur Slide 52
The temperature at which the relative humidity is 100% is called the dew
point.
12.10 Humidity
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
53/56
PHYS222 LSSU Bazlur Slide 53
Force
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
54/56
PHYS222 LSSU Bazlur Slide 54
A
Force
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
55/56
PHYS222 LSSU Bazlur Slide 55
A
Force
8/12/2019 Lec 02b PHYS222 Ch 12 Heat Sp07
56/56
A