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the perfect gasLearning the basic concept of thermodynamic
from properties of the perfect gas
febdian RUSYDI, 2015
Phases of object
PLASMA
http://diary.febdian.net/2009/06/27/wujud-zat-kelima/
The 5th phase (Nature, 2009-Jun-25)
The simplest phase to study physically.
What the perfect gas is
𝑃𝑉 = 𝑁𝑘𝑇(kinetic theory of gas)
absolute pressure
absolute volume
Number of molecules
Boltzmann constant
temperature
five basic concepts
1) System and surrounding
2) State and equation of state
3) Equilibrium: mechanical
4) Equilibrium: thermal
5) Path of phase change
1st concept:
system & surroundingboundary
surrounding
open system
closed system
isolated system
mass energy
○ ○
○
(𝑚, 𝐸)
2nd concept:
state & equation of state
Defined by a set of
physical quantities,
extensive
intensive
𝑉 = 𝑓 𝑁, 𝑃, 𝑇these quantities are related one to another.
You only need 𝑁 and another two quantities
to determine everything else.
At certain values = at certain state.
Change any value = change state.
𝑛, 𝑁,𝑚, 𝑉, …
𝑇, 𝑃,𝑉
𝑛≡ 𝑉,…
2nd concept:
state & equation of state
Defined by a set of
physical quantities,
𝑁, 𝑛,𝑚, 𝑉, …
𝑇, 𝑃,𝑉
𝑁≡ 𝑉,…
extensive
intensive
𝑉 = 𝑓 𝑁, 𝑃, 𝑇these quantities are related one to another.
You only need 𝑁 and another two quantities
to determine everything else.
At certain values = at certain state.
Change any value = change state.
System must be in equilibrium.
3rd concept:
mechanical equilibrium
𝑃A 𝑃B 𝑃0 𝑃0
timeinitial final
𝑃A > 𝑃B
Learn how barometer work!
4th concept:
thermal equilibrium
A
B
If no heat transfer from A to B, or vice versa,
then A and B are in thermal equilibrium.
If A and B are in thermal equilibrium
then A and B are in the same temperature.
0th law of thermodynamics
A
B
C
If A and B are in thermal equilibrium
and B and C are in thermal equilibrium,
then A and C are in thermal equilibrium.
If 𝑇A = 𝑇Band 𝑇B = 𝑇C,
then 𝑇A = 𝑇C.
Thermometer
concept born
from this law!
thermometer
H2O
mercury
( liq. )
C
0 100
melting
point
boiling
point
thermometer
H2O
mercury
( liq. )
C
0 100
melting
point
boiling
point
70
Temperature scale
𝐹 − 32
212 − 𝐹=
𝐶 − 0
100 − 𝐶=
𝐾 − 273.15
373.15 − 𝐾
(interpolation and extrapolation)
Fahrenheit Celsius Kelvin
value?
5th concept:
path of state change
𝑇
𝑃 initial
final
Isobaric
Isothermic
Isovolumic
Adiabatic
Reversible
Irreversible
What we have been discussed
Five basic concepts of thermodynamics from the ideal gas:
1. System, surrounding, and boundary.
2. State and equation of state.
3. Mechanical equilibrium.
4. Thermal equilibrium 0th law temperature and thermometer.
5. Path of state change.
example: ideal gas thermometerWhat we need to build a gas thermometer?
1. A substance.
2. Physical properties
3. Two reference points.
4. Interpolation to connect these two points.
example: ideal gas thermometer
𝑓(𝑇)
𝑇0 100𝑇0
PV, VT, and PT diagrams
𝑃𝑉 = const. V ∝ T P ∝ T
PVTdiagramsurface
example of PVT-surface usage
Possible states of gas
on the PVT-surface
Path of phase change
on the PVT-surface
1 2
example of PVT-surface usage
3
Phase of substance
identification.
Finally, Kelvin scale thermometer
𝑓(𝑇)
𝑇 (𝐾)273.16𝑇tp water
0.00absolute zero
Not so ideal gas?