Transcript 21-23 Temperature Part 2

P&P 13 States of Matter
• In this chapter we will combine ideas from the
last chapter on thermal physics with the various
states of matter. exploration.grc.nasa.gov/.../rocket/state.html
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Conceptual Physics class:
You are responsible for
only slides 21-33
The remaining slides are
review from Matter
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Fluids - liquids and gases
Pressure = Force = F
Area A
N Pascal or Pa
m2
Standard atmosphere = 1.01325x105Pa
10N/cm2 or 10-4N/m2
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Gas Laws
• Combined Gas Law
P1V1 = P2V2
T1
T2
1 – original values
2 – new values
P, Pressure, Pa
V, Volume, Liter, L
T, Temperature, K
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Ideal Gas Law
PV = n RT
P, pressure, Pa
V, volume, L
n, number of moles or molecules
R, universal gas constant:
8.31 Pa m3/mol K
T, temperature, K
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Pascal’s Principle
If an external pressure is applied to a
confined fluid, the pressure at every point
within the fluid increases by that amount.
F2
F1
=
A2
A1
F, force, newtons, N
A, area, m2
http://www.cord.edu/dept/physics/p128/Images/Pascal_principle.gif
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http://www.engineering.com/content/community/library/sciencelaws/pas
calslaw/images/variation_depth.jpg
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Buoyant Force
• Fbuoyant = rfluid Vg
 r, density for water, 1.00 x 103 kg/m3
• v, volume, m3
• g, gravity, 9.8 m/s2
“The buoyant force on an object is equal to
the weight of the fluid displaced by the
object, which is equal to the density of the
fluid in which the object is immersed
multiplied by the object’s volume and the
acceleration due to gravity. (page 354) 13
Archimedes’ Principle
• “An object immersed in a fluid has an
upward force on it that is equal to the
weight of the fluid displaced by the object.
The force does not depend on the weight
of the object, only on the weight of the
displaced fluid.
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http://home.earthlink.net/~divegeek/arc
himedes_files/buoyancy.gif
http://www.stormyseas.com/imag
es/buoyancy.jpg
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P=rhg
Pressure at any depth is proportional to the fluid’s weight
above that depth.
P, pressure, Pascal or N/m2
r, density, kg/m3
As depth
h, depth of object, m
increases, psi
increases.
Also fish
change with
depth.
English psi –
pounds per
square inch
SI unit: Pascal
or N/m2
http://www.flow-guard.com/flow-guard-images/breather-bag-images/underwater-well-head.jpg
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Bernoulli’s Principle
• As the velocity of a fluid increases, the
pressure exerted by that fluid decreases.
solomon.physics.sc.edu/~tedeschi/demo/demo21.html
www.centennialofflight.gov/.../bernoulli/DI9.htm
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star.tau.ac.il/QUIZ/05/Q07.05.html
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21.9 Expansion of Water
At 0°C, ice is less dense than water,
and so ice floats on water.
21.9 Expansion of Water
Almost all liquids will expand when they are heated.
Ice-cold water, however, does just the opposite!
• Water at the temperature of melting ice—0°C (or
32°F) —contracts when the temperature is
increased.
• As the water is heated and its temperature rises,
it continues to contract until it reaches a
temperature of 4°C.
• With further increase in temperature, the water
then begins to expand.
• The expansion continues all the way to the
boiling point.
21.9 Expansion of Water
The graph shows the change in volume of water with
increasing temperature.
21.9 Expansion of Water
Water molecules in their crystal form have an openstructured, six-sided arrangement. As a result, water
expands upon freezing, and ice is less dense than
water.
21.9 Expansion of Water
Melting Ice
When ice melts, some crystals remain in
the ice-water mixture, making a
microscopic slush that slightly “bloats” the
water.
• Ice water is therefore less dense than
slightly warmer water.
• With an increase in temperature, more
of the remaining ice crystals collapse.
• The melting of these crystals further
decreases the volume of the water.
21.9 Expansion of Water
The collapsing of ice crystals (left) plus
increased molecular motion with increasing
temperature (center) combine to make water
most dense at 4°C (right).
Solids
• The thermal expansion of a solid is
proportional to the temperature change
and original size, and it depends on the
material.
http://www.scienceclarified.com/images/uesc_10_img0566.jpg
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Coefficient of Linear Expansion, a
a=DL
L1 DT
change in length
orig. length, change in temp
Units: 1/oC or oC-1
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Coefficient of Volume Expansion, b
b= DV
V1 DT
Units: oC-1
change in volume
orig. volume, change in temp
Manufacturing many types of
glassware made of heat resistant
borosilicate glass or soda lime
glass using automatic press
machines or manual press.
Borosilicate Glass(Code: TE-32)
with thermal expansion coefficient
32.5X10-7/°C
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Major Applications
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Glass trays for Micro oven
Transparent roof tiles
Glass mixer jars
Glass window for automatic washing machines
Glass lens and reflector for automotive lighting
Glass globes for airport or harbor lighting
Colored lenses for railroad signals
Fly-eye lens for digital projectors
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