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8/3/2019 AP Physics Ch 10&11 Day 1
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Chapter 10&11 Day 1
AP Physics Objectives Relate temperature to the kinetic energy of
atoms and molecules.
Describe the changes in the temperatures of two
objects reaching thermal equilibrium.
Identify the various temperature scales, and be
able to convert from one scale to another.
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Turn off cell phones!
Pick up worksheets 10-1 MathSkills and Problem 10A
Check updated grades
Pick up Chapter 7 Review packet
Read pages 357-364
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Thermal Physics
Thermal physics is the study of
Temperature
Heat
How these affect matter
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Thermal Physics, cont
Concerned with the concepts of energy transfersbetween a system and its environment and theresulting temperature variations
Historically, the development of thermodynamicsparalleled the development of atomic theory
Concerns itself with the physical and chemicaltransformations of matter in all of its forms: solid,liquid, and gas
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Heat
The process by which energy is exchanged between
objects because of temperature differences is called heat
Objects are in thermal contactif energy can be exchanged
between them
Thermal equilibrium exists when two objects in thermal
contact with each other cease to exchange energy
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Zeroth Law of Thermodynamics
If objects A and B are separately in thermal equilibrium with a third
object, C, then A and B are in thermal equilibrium with each other.
Allows a definition of temperature
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Temperature from the Zeroth
Law Two objects in thermal equilibrium with
each other are at the same temperature
Temperature is the property that determines
whether or not an object is in thermal
equilibrium with other objects
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Thermometers
Used to measure the temperature of an object or a system
Make use of physical properties that change withtemperature
Many physical properties can be used volume of a liquid
length of a solid
pressure of a gas held at constant volume
volume of a gas held at constant pressure
electric resistance of a conductor
color of a very hot object
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Thermometers, cont
A mercury thermometer isan example of a commonthermometer
The level of the mercuryrises due to thermalexpansion
Temperature can be definedby the height of the mercurycolumn
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Temperature Scales
Thermometers can be calibrated by placing
them in thermal contact with an
environment that remains at constant
temperature
Environment could be mixture of ice and water
in thermal equilibrium
Also commonly used is water and steam in
thermal equilibrium
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Celsius Scale
Temperature of an ice-water mixture is defined as 0 C
This is thefreezing pointof water
Temperature of a water-steam mixture is defined as 100 C
This is the boiling pointof water
Distance between these points is divided into 100 segments
or degrees
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Gas Thermometer
Temperature readingsare nearly independentof the gas
Pressure varies withtemperature whenmaintaining a constantvolume
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Kelvin Scale
When the pressure of a gas goes to zero, its temperature is
273.15 C
This temperature is called absolute zero
This is the zero point of the Kelvin scale
273.15 C = 0 K
To convert: TC = TK 273.15
The size of the degree in the Kelvin scale is the same as the size of
a Celsius degree
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Pressure-Temperature Graph
All gases extrapolate to
the same temperature at
zero pressure
This temperature is
absolute zero
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Modern Definition of Kelvin
Scale Defined in terms of two points
Agreed upon by International Committee on Weights and
Measures in 1954
First point is absolute zero
Second point is the triple pointof water
Triple point is the single point where water can exist as solid,
liquid, and gas
Single temperature and pressure
Occurs at 0.01 C and P = 4.58 mm Hg
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Modern Definition of Kelvin
Scale, cont The temperature of the triple point on the
Kelvin scale is 273.16 K
Therefore, the current definition of of the
Kelvin is defined as
1/273.16 of the temperature of the triple
point of water
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Some Kelvin
Temperatures Some representative
Kelvin temperatures
Note, this scale is
logarithmic
Absolute zero has
never been reached
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Fahrenheit Scales
Most common scale used in the US
Temperature of the freezing point is 32
Temperature of the boiling point is 212
180 divisions between the points
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Comparing Temperature Scales
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Converting Among Temperature
Scales
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Practice 10A, page 363
2) The temperatures of one
northeastern state range from 105F in
the summer to -25F in winter.
Express this temperature range in
degrees Celsius and in kelvins.