first law of thermodynamics · thermodynamic process. thermodynamic process process isothermal...
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Basic
ThermodynamicsLecture 6
Thermodynamic Process
Thermodynamic Process
PROPERTIES AND STATES
• A macroscopic characteristic of a system such as mass, volume, energy,
pressure, and temperature to which a numerical value can be assigned at any
given time without knowledge of the previous behavior (history) of the system
is called property.
• Properties (can be measured or calculated) of a system that completely
describes the condition of said system is called the state.
• At a given state, all the properties of a system have certain values. If the
values of these properties change, the state will change.
• The number of properties required to fix the state of a system is given by the
state postulate:
The state of a simple compressible system is
completely specified by two independent
intensive properties.
Thermodynamic Process
• Any change that a system undergoes
from one equilibrium state to
another is called a process.
• The series of states through which a
system passes during a process is
called the path of the process.
PROCESS
Thermodynamic Process
• Work of a process DEPENDS on the path.
PROCESS
Thermodynamic Process
PROCESS
Isothermal
constant temperature
DT = DU = 0 U is constant
V
p
DU = Q – W
W = Q
Thermodynamic Process
PROCESS
Isothermal
V
p
Recall that for ideal gas, when the temperature is
constant, then pv=constant, so that
Thermodynamic Process
PROCESS
Isobaric
constant pressure
DP = 0
means W = PDV = P (Vf – Vi)
V
p
DU = Q – W
Thermodynamic Process
PROCESS
Isobaric
V
p
DU = Q – W
Pada umumnya terjadi pada sistem yang
mempunyai kontak langsung dengan tekanan
atmosfer bumi yang dianggap konstan
(misal: reaksi kimia)
Thermodynamic Process
PROCESS
Isobaric
DU = Q – W
= Q – p.ΔV
= Q – Δ(pV)
Q = DU + D(pV)
Thermodynamic Process
PROCESS
Isothermal
Isobaric
Isochoric
Adiabatic
Isentropic
constant volume
DV = 0
means W = 0
DU = Q – W
DU = Q
PROCESS
Isothermal
Isobaric
Isochoric
Adiabatic
Isentropic
DU = Q – W
DU = Q
Proses ini terjadi pada sistem yang mempunyai
volume (wadah) yang kuat, tertutup dan tidak dapat
berubah
Thermodynamic Process
Thermodynamic Process
PROCESS
Isothermal
Isobaric
Isochoric
Adiabatic
Isentropic
DU = Q – W
DU = -W
No heat addition
Q = 0
Thermodynamic Process
PROCESS
Isothermal
Isobaric
Isochoric
Adiabatic
Isentropic
define a new term, H U + pV ; and called it the
enthalpy