12.1 notes.notebook - wisconsin lutheran high...
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12.1 notes.notebook
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Temperature and Thermal Energythermodynamics: the study of heat
caloric theory: early theory of TE
honolulu.hawaii.edu
An incorrect theory which serves as a model for scientific growth anguage retains vestiges of concept heat flows, objects soak up heat leads to confusion: we speak of it as a substance while told that it is not metaphor Lavoisier coined the term later in 1787 firmly entrenched by 1780 largely discredited by 1850 conservation of heat was a basic premise
heat lost by one object is gained by another this is true and still a basis for calorimetry
heat was thought of as a substancefluid = can flow a fluid called caloric
Properties of Caloriccould not be created nor destroyed all substances contain caloric and absorb or release it flows from hot to cold objects or substances counterbalanced attractive forces of "particles of matter" self repulsion caused it to flow from higher to lower concentration kind of like pressure in a balloon
state of matter determined by amount of caloriccaloric surrounds the particles of matter causing them to swell caloric occupied space, so gas has lots of caloric
KineticMolecular Theory1) All matter is made up of particles in constant motion with elastic collisions
(KE = KE')
2) The: >motion >KE > Temperature
bonds: electromagnetic forces
particles vibrate back and forth (KE)intermolecular bond resist vibration , therefore particles have PE (elastic/electric)overall energy is called Thermal Energy
http://hyperphysics.phyastr.gsu.edu/hbase/acloc.html
atomic clock
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http://lectureonline.cl.msu.edu/~mmp/kap10/cd283.htm
http://mc2.cchem.berkeley.edu/Java/molecules/index.html
Temperature: measures "hotness" of an object. Temperature is a measure of the average energy (KE) of the particles of an object.
https://www.youtube.com/watch?v=v12xG80KcZw
https://www.youtube.com/watch?v=dHJmOH38agY
states of water
Thermal Energy: total PE + KE associated with the random motion and arrangement of the particles of a material (Total Internal Energy)Heat: Thermal Energy that's absorbed, given up, or transferred from one body to another. Flowing of TE (thermal contact)
Temperature: physical quantity that is proportionate to the average (translational) KE of the particles in matter.
a measure of a body's ability to give up or absorb TE from another body
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Can't measure KE (motion) directly, so we measure its effect on something else.
(indirect measurement)
> temp >motion > volume
> temp >volume
> temp > electrical resistance to current
> temp > resistance
Temperature Scales
Fahrenheit based on body temperature/brine(Rankine)
Celsius based on freezing and boiling of water
Kelvin based on "absolute zero"
C = (F 32) /1.8 or 5/9(F 32) F = (C x 1.8) + 32 or 9/5C + 32K = C + 273
http://en.wikipedia.org/wiki/Absolute_zero
http://en.wikipedia.org/wiki/Fahrenheit
http://en.wikipedia.org/wiki/Celcius
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When converting between C and F180 is the magic number using boilingof water
F CC = 5/9(F 32) or (F 32) /1.8
F = 9/5C + 32 or (C x 1.8) + 32
212o F = ____o C212o F 32 = 180 180/1.8 = 100oC
C F
100o C= ____o F100o C x 1.8 = 180 180 + 32 = 212o F
100F = _________0C
280C = __________0F
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100F = _________0C
280C = __________0F
C = (F 32) /1.8C = (100F 32)/1.8C = 120C
F = (C x 1.8) + 32F = (280C x 1.8) + 32F = 820 F
820F = _________0C
380C = __________0F
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820F = _________0C
380C = __________0F
C = (F 32) /1.8C = (820F 32)/1.8C = 280C
F = (C x 1.8) + 32F = (380C x 1.8) + 32F = 1000 F
520F = _________0C
880C = __________0F
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520F = _________0C
880C = __________0F
C = (F 32) /1.8C = (520F 32)/1.8C = 110C
F = (C x 1.8) + 32F = (880C x 1.8) + 32F = 1900 F
Thermal Energy Transfer
conduction
convection
radiation
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If you put a metal bar into a flame, it gets hot quickly. Soon you can't hold it. If you put a glass bar into a candle, it won'tget too hot to hold. But if you touched the end that was in the flame, you would find that it was really hot!The process in which heat passes through a solid substance is called conduction. Metals are good conductors of heat. Non‐metals are generally bad conductors of heat. Liquids and gases are bad conductors of heat as well. A bad conductor of heat is called an insulator. Your quilt, or winter jacket, traps air which is a good insulator.
conduction
ConvectionConvection occurs only in liquids and gases. We call liquids and gases fluids. It cannot happen in solids. It needs particles to be free to move about. When a liquid is heated, the molecules at the bottom move about with bigger vibrations. They take up more space which means that the density goes down. The less dense fluid rises. It gives its energy to the fluid above, and cools down. It becomes denser and falls back to the bottom. A convection current is set up.
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RadiationRadiation passes heat on as an electromagnetic wave called infra‐red radiation. All the heat from the Sun reaches us as electromagnetic radiation. Our eyes cannot see infra red, but a digital camera can. Here is a picture of a hot plate that appears much brighter than it actually is because of the infra red radiation.
"hot" plate
E = W = Fd
KE = ½mv2
PE = mgh
Q = mcΔtthermal energy
Note the similarities to the other forms of energy!!!!... amounts ... unique properties of that form of energy ... what's changing ... mass g or c v, h, or t
"g" is unique to superior object ... [ g = Gm1/r2 ] all object attract all other objects and each has their own "g" value
"c" is unique to molecular/atomic makeup of an object ... [ c = Q/m∆t ] all object
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Specific Heat
Q = mcΔt
specific heat"thermal property of matter"
c = Q/mΔt c = J/(kg0C)TE kg 10 C
the thermal energy needed to change l kg of a substance 1 degree C
"c" is
How much TE does it take to raise 100.g of iron from 170 C to 100.o C?
iron
TE = ?mi = 100 g
0.100 kgt1 = 170Ct2 = 1000C
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How much TE does it take to raise 100.g of iron from 170 C to 100.o C?TE = ? (Q)mi = 100 g
0.100 kgt1 = 170Ct2 = 1000C
Q = mcΔtQ = mc(tf ti)Q = .100 kg[450 J/(kg0C)](100.0C 170C)Q = .100 kg[450 J/(kg0C)](100.0C 170C)Q = 3700 J
PE = mgh = (kg)m/s2(m) = N x m = J
TE = Q = mcΔt = kg[J/(kg0 C)] 0C = J
c = Q/mΔt = J/(kg0 C)some common "c" valuestext page 279 (eachtextbook will listslightly differentvalues for "c"
copper 385 J/kg0CH20 4180 J/kg0Cmetal 450 J/kg0Clead 135 J/kg0Cice 2060 J/kg0Csteam 2020 J/kg0C
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QL + Qg = 0Qlost + Qgained = 0
Law of Heat Exchange
100 g of metal at 100.0C100 g of H20 at 600C mix them together!
Temp
Time
1000C
600C
tim
tiw
tfmtfw
tf
QL
Qg
tfm = ffw = tf
Steel loses TE because
it's at a higher temperature
Water gains TE because
it's at a lower temperature remember the inelastic collision when v1' = v2' = v'
thermal equilibrium
100 g of steel at 1000C100 g of water at 600C
What is the final temperature?QL + Qg = 0mcΔts + mcΔtw = 0mc(tf ti)s + mc(tf ti)w = 0(mctfs mctis) + (mctfw mctiw) =0
mcstf mctis + mcwtf mctiw =0mcstf + mcwtf = mctis + mctiwtf(mcs + mcw) = mctis + mctiwtf = mctis + mctiw mcs + mcw tf = .1kg(450J/kgC)1000C + .1kg(4180J/kgC)600C
[.1kg(450J/kgC)] + [.1kg(4180J/kgC)]tf = 4500 J + 25100 J 463J/0Ctf = 63.90C
QL + Qg = 0mcΔts + mcΔtw = 0mc(tf ti)s + mc(tf ti)w = 0
[.1kg(450J/kgC)(63.90C 1000C)] + [.1kg(4180J/kgC)(63.90C 600C)] = 0 1625 J + 1630 J = 0 slightly off because of rounding
you mix:
is tfs = tfw ? ...YES, ∴ tfs = tfw = tfadd "mcti" 's from both sides
expand Δt's
factor out the "mc" 's
divide by "mc" 's
dist. steel
water600C
tf = 63.90C
1000C
QLs = 1625 J
Qgw = 1630 J
note the "" denotes loss of TE
and "+" denotes gain of TE
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steel
water600C
tf = 63.90C
1000C
QLs = 1625 J
Qgw = 1630 J
tis = 1000C
tiw = 600C