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?