Download Entropy - Dordt College Homepages

Episode 47 - Entropy
0:00
1:44
2:04
3:30
4:30
6:45
7:50
9:35
10:00
11:42
12:40
13:12
14:00
14:40
16:45
17:30
20:00
Credits, etc.
Intro
Four postulates, laws of thermodynamics
2nd - entropy principle
1st - energy conservation
0th - temperature
3rd - absolute zero
Deduce properties of matter
Ultimate fate of universe
Chalkey’s Billiard Room
Investigate laws of thermodynamics
Drinks with ice: beakers and experimental fluid
T = 295 K alcohol and crystalline H20 @ 273K
Ice cubes don’t melt at once: no warm ice cubes
Ice melts as heat flows into it
Why won’t it warm up?
Why approach equilibrium?
Clouds, volcano, iceberg formation, savannah, waterfall
Earth is a machine, a factory never running down, driven by energy of sun
Trade winds, ships: heat in motion sets matter into motion for both
steam engine: heat TH  TC
TH - exploding gasoline
TC - circulating cooling system
TH, TC better engine
TH = TC  equilibrium, out of gas
Molecular dynamics simulation
Reaching thermal equilibrium
Falling body bouncing: kinetic energy  thermal energy
Clouds
U+K=Q
Carnot cycle: Sodi Carnot - isotherm, adiabat
Qin at Tin ; Qout at Tout ; W done
Rudolf Clausing & William Thompson rescued Carnot’s writings
efficiency, e = 1  Qout/Qin = 1  Tout/Tin
Clausius - S = Q/T same in and out
ideal engine conserves energy and entropy
real engine Sout > Sin - entropy is created - not isothermal or adiabatic, there’s
friction
entropy flow S = Q/T
(Question: why is entropy created in a real engine?)
S  0 until everything is at equilibrium
ice melting @ T = 0C
Swater > Sice
water more disordered
ice melting - Sice > 0 (good)
S rest of universe = E/T < 0 (not good)
Suniverse > 0
strive to maximize SE/T
i.e. minimize F = ETS (free energy)
24:45 heat death of universe
25:10 Goodstein
entropy principle - flow of time
atomic collisions are time-reversal invariant (S  0 doesn’t apply)
ball bouncing - forward direction is one where successive bounces get smaller
S > 0 same as t > 0 (tautology)
no
Episode 48
Low Temperature
32:18
33:27
Goodstein—cold
changing air into liquid
state dependent on temperature & pressure
Faraday
experimented w/ states of matter
first to realize that matter can exist in 3 states, relationship of states
to pressure & temperature
states animation, phase diagram
critical point—Le Tour—ethane demonstration
evaporation & condensation
August 1950 again
evaporation animation
Da Vinci—system to cool air
Goodstein—carbon dioxide as coolant
Faraday—liquefied every known gas but oxygen, nitrogen, & hydrogen
cascade process
heat exchanger animation
Joule & Kelvin
Joule-Thomson effect animation
Linde—final step in liquefying air
liquid hydrogen
Royal Institution
Netherlands—University of Leyden
race to liquefy hydrogen
Kamerlingh Onnes vs. Dewar
Dewar won, but helium discovered just before, so hydrogen no
longer last known gas to be liquefied
Kamerlingh Onnes—first to liquefy helium @ 4 K
Goodstein—liquid air
35:56
37:55
41:12
42:28
43:41
44:13
46:22
48:00
49:12
49:59
50:49
52:15
55:48