Laws of Thermodynamics 1

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Laws ofThermodynamics 1

• Disusun Oleh
• Ichwan Aryono, S.Pd.

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First law of thermodynamics
First Law of thermodynamics states that
Whenever heat Q is given to a system, a portion
of heat is used to increase its internal energy
in the amount of DU, whereas the remaining leaves
the system when the system performs a work W to
its surroundings. Mathematically, the first law
of thermodynamics is formulated by Q DU W
Qgt0
W positip jika sistem melakukan usaha W negatip
jika sistem dikenai usaha Q positip Jika sistem
menerima kalor Q negatip jika sistem melepas
kalor Energi dalam DU tidak terpengaruh oleh
proses, yang dilihat adalah hanya pada keadaan
awal dan keadaan akhir
Wgt0
Wlt0
Qlt0
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The first law of thermodynamics for isothermal
process
At isothermal Process DT 0, so DU 0 The
work done by the isothermal process is
Q DU W 0 W W Q
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The first law of thermodynamics for
isobaricprocess
At isobaric process the pressure is constant DP
0 Internal energy , so
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The first law of thermodynamics for isochoric
process
At Isochoric process volume is constant, DV 0,
so the work done W PDV 0, its produce
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The first law of thermodynamics for adiabatic
process
Adiabatic process is a process without any
transfer of heat into or from the system (Q0)and
it applies
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Student Activity 1
A system absorbs 1500 J of heat from surrounding
and does work done 2200 J . Determine the
change of internal energy system, increases or
decreases ?
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Student Activity

• Mention three general variables of thermodynamics

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• What is state function ?

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• Why is the internal energy classified as a state
  function, meanwhile work and heat is not
  classified as a state function ?

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• Can we warm up of a soap without giving any
  additional amount of heat to the soup ? Explain it

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• A work can be done into a system at a constant
  pressure, heat can also be tranferred to a system
  at a constant volume. Is it possible to transfer
  heat to a system while maintaining the
  temperature of the system constant ? Explain it

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• A diatomic in a closed container has an initial
  temperature of 250oC, a pressure of 105 N/m2, and
  a volume of 5 L. The gas undergoes an isobaric
  process to a pressure of 2 x 105 N/m2. a.
  Describes the process above in a P-V diagram
• b. Find the change in its internal energy
• c. find the total work done by the gas

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Student Activity

• Mention three general variables of thermodynamics
• What is state function ?
• Why is the internal energy classified as a state
  function, meanwhile work and heat is not
  classified as a state function ?
• Can we warm up of a soap without giving any
  additional amount of heat to the soup ? Explain
  it
• A work can be done into a system at a constant
  pressure, heat can also be tranferred to a system
  at a constant volume. Is it possible to transfer
  heat to a system while maintaining the
  temperature of the system constant ? Explain it

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Student Activity 2
System absorbs 1500 J of energy from surrounding.
At the same time 2200 J work done is given to the
system. Determine the change of internal energy
of the system. Is temperature decreses or
increases ?
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Student Activity 3
Two mol of ideal gas is expans from point I to
point F with three difference way as shown in
diagram below. Calculate the work done, change of
internal energy, and calor in each way IAF, IF
and IBF, state in joule
P(atm)
A
4
I
B
F
1
V(L)
2
4
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Student Activity
P(Pa)
Four mol of ideal gas in cylinder container
change its conditional as shown in graphic P-V
beside. Determine the work done, internal energy
and calor if the gas is change from A to C thrue
(a) ABC, (b) AC
A
B
500
C
200
V(cm3)
0
800
500
300
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Quiz (work in pairs)

• Three different processes act on system.
• In process A, 42J of work are done on the system
  and 77J of heat are added to the system. Find the
  change in the systems internal energy.
• b. In process B. the system does 42 J of work
  and 77J of heat are added to the system. What is
  the change in the systems internal energy ?
• c. In process C, the systems internal energy
  decreases by 120 J while the system performs 120
  J of work on its surroundings. How much heat was
  added to the system ?

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Student Activity 6
An ideal gas is taken through the four processes
shown in figure below. The changes in internal
energy for three of these processes are as
follows DUAB 82 J, DUBC 15 J, DUDA -56
J. Find the change in internal energy for the
process from C to D
D
C
pressure
A
B
volume
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Student Activity 7
a. Find the work done by a monoatomic ideal gas
as it expands from point A to point C along the
path shown in figure below. b. If the temperature
of the gas is 220K at point A, what is its
temperature at point C ? c. How much heat has
been added to or removed from the gas during this
process ?
B
600
400
Pressure P(kPa)
A
C
200
Volume, V(m3)
0
2
4
6
8
10
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Student Activity 8

• During an adiabatic process, the temperature of
  3.52 moles of monoatomic ideal gas drops from
  485oC to 205oC. For this gas, find
• The work it does
• The heat it exchanges with its surroundings, and
• The changes in internal energy

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Student Activity 9

• An ideal gas follows the three-part process shown
  in figure below. At the completion of one full
  cycle, find
• The net work done by the system
• The net change in internal energy of the system
• The net heat absorbed by the system

A
150
Pressure P(kPa)
100
B
50
C
1
2
0
3
4
Volume, V(m3)
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Quiz

• Suppose 57.5 moles of an ideal monoatomic gas
  undergoes the series of processes shown in figure
  below.
• Calculate the temperature at the points A, B, and
  C.
• For each process, A-B, B-C, and C-A, state
  whether heat enters or leaves the system, Explain
  in each case.
• Calculate the heat exchanged with the gas during
  each of three process.

A
150
Pressure P(kPa)
100
B
50
C
1
2
0
3
4
Volume, V(m3)