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Mastery Learning - First Law of Thermodynamics
& Energy Balance
email: email: [email protected]@salam.uitm.edu.my
Website: http://www5.uitm.edu.my/faculties/fsg/drjj1.html
Applied Sciences Education Research Group (ASERG)
Faculty of Applied SciencesUniversiti Teknologi MARA
Voice: 019-455-1621
QuotesQuotes
"One who learns by finding out has sevenfold the skill of the one who learned by being told.“ - Arthur Gutterman
"The roots of education are bitter, but the fruit is sweet." -Aristotle
"The roots of education are bitter, but the fruit is sweet." -Aristotle
Advantages Disadvantages (easily dealt with)
Preparation
• Teachers must state objectives before designating activities
• Requires teachers to do task analysis, thereby becoming better prepared to teach the unit.
• Students progress at different pace; so students who have mastered must wait for those who haven’t or must individualize instruction.
• Must have a variety of materials for re-teaching.
•Teacher must state objectives clearly.
•Teacher must perform task analysis.
Instructional Strategy - Mastery Learning
Advantages Disadvantages Preparation
• Requires teachers to state objectives before designating activities
• Can break cycle of failure (especially important for minority and disadvantaged students)
• Must have several tests for each unit
• If only objective tests are used, can lead to memorizing and learning specifics rather than higher levels of learning
•Teacher must be alert and patient in dealing with the pace of the pupils.
Instructional Strategy - Mastery Learning
First Law of Thermodynamics & Energy Balance –
Control Mass, Open System
email: email: [email protected]@salam.uitm.edu.my
Website: http://www5.uitm.edu.my/faculties/fsg/drjj1.html
Applied Sciences Education Research Group (ASERG)
Faculty of Applied SciencesUniversiti Teknologi MARA
Voice: 019-455-1621
CHAPTER
4
The First Law of Thermodynamics
IntroductionIntroduction
1. Identify the energies causing a system’s properties to change.
2. Identify the energy changes within the system.
3. State the conservation of energy principle.
4. Write an energy balance for a general system undergoing any process.
Objectives:Objectives:
IntroductionIntroduction
5. Write the unit-mass basis and unit-time basis (or rate-form basis) energy balance for a general system undergoing any process.
6. Write the energy balance in terms of all the energies causing the change and all the energy changes within the system.
7. Write a unit-mass basis and unit-time basis (or rate-form basis) energy balance in terms of all the energies causing the change and all the energy changes within the system.
Objectives:Objectives:
IntroductionIntroduction
8. State the conditions for stationary, closed system and rewrite the energy balance and the unit-mass basis energy balance for stationary-closed systems.
9. Apply the energy conservation principle for a stationary, closed system undergoing an adiabatic process and discuss its physical interpretation.
Objectives:Objectives:
IntroductionIntroduction
10.Apply the energy conservation principle for a stationary, closed system undergoing an isochoric, isothermal, cyclic and isobaric process and discuss its physical interpretation.
11.Give the meaning for specific heat and state its significance in determining internal energy and enthalpy change for ideal gases, liquids and solids.
12.Use the energy balance for problem solving.
Objectives:Objectives:
Instructional Plan-MasteryUnit 1:Unit 1:
Objectives:Objectives:
1. Identify the energies causing the system to change.
2. Identify the energy changes within the system.
3. State the conservation of energy principle.
4. Write an energy balance for a general system undergoing any process.
Instructional Plan-MasteryUnit 2:Unit 2:
Objectives:Objectives:5. Write the unit-mass basis and unit-
time basis (or rate-form basis) energy balance for a general system undergoing any process.
6. Write the energy balance in terms of all the energies causing the change and the energy changes within the system.
7. Write a unit-mass basis and unit-time basis (or rate-form basis) energy balance in terms of all the energies causing the change and the energy changes within the system.
Instructional Plan-Diagnose
Preparatory DiagnosticsPreparatory Diagnostics
If P = 100 kPa, T = 25C , determine the phase of water, its specific volume, its specific enthalpy and its specific internal energy.
How can you boil the water? What types of energy can you give to boil it? What is the boiling or saturation temperature?
What is the phase, the specific volume and the specific internal energy when the temperature reaches 150C , at constant pressure?
Instructional Plan - Re-teach
Preparatory DiagnosticsPreparatory Diagnostics
Students’ activityStudents’ activity:: read the saturated-water,pressure property table. Obtain and u.
Students’ activity:Students’ activity: Check table for the saturation temp at 100 kPa. Then suggests 2 ways of boiling water.
Students’ activity:Students’ activity: Suggest the phase and provide reason. Then suggest method on how to find and u.
Failure to complete task: re-teach then give different example
Otherwise, proceed with the lesson’s learning outcome
3-1
Instructional Plan - Re-teachInstructional Plan - Re-teach
LemLem
OvenOven
200C200C
NasiLemak 20C
NasiLemak 20C
qinqin
H2O:Sat. Liq.
Sat. VaporSat. Vapor
P = 100 kPa
T = 99.6 C
P = 100 kPa
T = 99.6 C
Qin
What happens toWhat happens tothe properties of the properties of the system after the the system after the energy transfer?energy transfer?
SODA5C
SODA5C
SODA5C
SODA5C
qqininqqinin
qqouou
tt
qqouou
tt 25C
Teacher Teacher ActivityActivityTeacher Teacher ActivityActivity
Energy transfer-Thermal Energy transfer-Thermal (heat)(heat)
Energy transfer-Thermal Energy transfer-Thermal (heat)(heat)
Example: A steam power cycle.Example: A steam power cycle.
SteamTurbine
Mechanical Energyto Generator
Heat Exchanger
Cooling Water
Pump
Fuel
Air
CombustionProducts
System Boundaryfor ThermodynamicAnalysis
System Boundaryfor ThermodynamicAnalysis
Qou
tQ
ou
t
Win
Win
WoutWout
QinQin
The net work output isThe net work output is kWWWW inoutoutnet ,,
DesiredDesiredoutputoutput
RequiredRequiredinputinput
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
Instructional Plan - Re-Instructional Plan - Re-teachteach
Energy Transfer – Work Done
ii
Voltage, VVoltage, V
No heat transferT increases
after some time
No heat transferT increases
after some time
H2O:SuperVapor
H2O:SuperVapor
Mechanical work:Piston moves up
Boundary work isdone by system
Mechanical work:Piston moves up
Boundary work isdone by system
Electrical work is done on systemElectrical work is done on system
H2O:Sat.
liquid
Wpw,in ,kJWpw,in ,kJ
We,in = Vit/1000, kJWe,in = Vit/1000, kJ
ViW e
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4-8
FIGURE 4-46Pipe or duct flow may involve more than one form of work at the same time.
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
System in thermal equilibrium
SystemTotal energy
E1
Can it change? How? Why?
System’s initial System’s initial total energy istotal energy is
EE11= U= U11+KE+KE11+PE+PE11 or or
ee11= u= u11+ke+ke11+pe+pe11, kJ/kg, kJ/kg
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
A change has taken place.
System,
E1
System
EE11= U= U11+KE+KE11+PE+PE11
Movable boundary position gone up
System expands
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
A change has taken place
System,
E1
SystemSystemInitiIniti
alal
FinaFinall
System’s final energy is System’s final energy is EE22=U=U22+KE+KE22+PE+PE22
EE11= U= U11+KE+KE11+PE+PE11
Movable boundary position gone up
Systemexpands
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
How to relate changes to the cause
Heat as a cause (agent) of change
SystemE1, P1, T1, V1
Toqin, or Qin
qout, or, Qout
Properties will change indicating change of
state
kW,Q in
kW,Qout
E2, P2, T2, V2
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
Work as a cause (agent) of change
SystemE1, P1, T1, V1
To
Properties will change indicating change of
state
Win, in, kJ/kg
Wout, in, kJ/kg
How to relate changes to the cause kW,W in
kW,W out
E2, P2, T2, V2
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
How to relate changes to the cause
Mass transfer as a cause (agent) of
change
SystemE1, P1, T1, V1
To
Properties will change indicating change of
state
Mass out
Mass in
kWmE ininmass ,)(,
kW,mout
kg/kJ,in kg/kJ,outE2, P2, T2, V2
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy TransferFirst Law – Energy Transfer
How to relate changes to the cause
Dynamic Energies as causes (agents)
of change
SystemE1, P1, T1, V1
To
Properties will change indicating change of
state
Mass out
Mass in
Win
Wout
Qin
Qout
E2, P2, T2, V2
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law-Conservation of Energy PrincipleFirst Law-Conservation of Energy Principle
Energy must be conserved in any Energy must be conserved in any process. Energy cannot be created process. Energy cannot be created nor destroyed. It can only change nor destroyed. It can only change
forms. Total Energy before a forms. Total Energy before a process must equal total energy process must equal total energy
after processafter process
Known as Conservation of Energy Principle
In any In any process, process,
every every bit of bit of
energy energy should should
be be accountaccounted for!!ed for!!
z =h
z =0
z =h/2
E=U+KE+PE = U+0+PE
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law-Conservation of Energy PrincipleFirst Law-Conservation of Energy Principle
Energy must be conserved in any Energy must be conserved in any process. Energy cannot be created process. Energy cannot be created nor destroyed. It can only change nor destroyed. It can only change
forms. Total Energy before a forms. Total Energy before a process must equal total energy process must equal total energy
after processafter process
Known as Conservation of Energy Principle
In any In any process, process,
every every bit of bit of
energy energy should should
be be accountaccounted for!!ed for!!
z =h
z =0
z =h/2 E=U+KE+PE
E=U+KE+PE=U+0+PE
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law-Conservation of Energy PrincipleFirst Law-Conservation of Energy Principle
Energy must be conserved in any Energy must be conserved in any process. Energy cannot be created process. Energy cannot be created nor destroyed. It can only change nor destroyed. It can only change
forms. Total Energy before a forms. Total Energy before a process must equal total energy process must equal total energy
after processafter process
Known as Conservation of Energy Principle
In any In any process, process,
every every bit of bit of
energy energy should should
be be accountaccounted for!!ed for!!
z =h
z =0
z =h/2 E=U+KE+PE
E=U+KE+0
ifke 22
if zzpe
Tu TeacheTeache
r r ActivityActivity
TeacheTeacher r
ActivityActivity
First Law Energy BalanceFirst Law Energy Balance
Energy Balance
Amount of energy causing energy causing changechange must be equal to amount
of energy changeenergy change of system
Energy Entering a system
-
Energy Leaving a system
=
Change of system’s energy
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law of ThermodynamicsFirst Law of Thermodynamics
Energy Balance
Ein – Eout = Esys, kJ orein – eout = esys, kJ/kg or
Energy Entering a system
-
Energy Leaving a system
=
Change of system’s energy
kW,EEE sysoutin
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law of ThermodynamicsFirst Law of Thermodynamics
How to relate changes to the cause
Dynamic Energies as causes (agents)
of change
SystemE1, P1, T1, V1
ToE2, P2, T2, V2
Properties will change indicating change of
state
Mass out
Mass inWin
Wout
Qin
Qout
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4-1
FIGURE 4–7The energy change of a system during a process is equal to the net work and heat transfer between the system and its surroundings.
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
Instructional Plan-ActivityActive Cooperative (group) LearningActive Cooperative (group) Learning
Name the energies which are agents of change
Name the energies within a system.
Draw and label energy interacting with a system and the energy changes within a system
StudentStudentActivityActivityStudentStudentActivityActivity
Draw the energies interacting with an open system
State the general energy conservation principle
Quantitatively solve some numerical problems
Instructional Plan - AssessActive Cooperative (group) LearningActive Cooperative (group) Learning
Failure to complete task: re-teach then give different example
Otherwise, proceed with the next unit
Teacher-students Teacher-students ActivityActivity
Teacher-students Teacher-students ActivityActivity
If all ok, increase difficulty level to application, analysis, synthesis and evaluation
Instructional Plan-MasteryUnit 2:Unit 2:
Objectives:Objectives:5. Write the unit-mass basis and unit-
time basis (or rate-form basis) energy balance for a general system undergoing any process.
6. Write the energy balance in terms of all the energies causing the change and the energy changes within the system.
7. Write a unit-mass basis and unit-time basis (or rate-form basis) energy balance in terms of all the energies causing the change and the energy changes within the system.
First Law – Interaction EnergiesFirst Law – Interaction Energies
Energy Balance – The Agent
kW ; EWQE in,massininin
Ein = Qin+Win+Emass,in ,kJ
ein = qin+ in+ in, kJ/kg
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law - Interaction EnergiesFirst Law - Interaction Energies
Energy Balance – The Agent
kW ; EWQE out,massoutoutin
E out = Q out +W out +Emass,out ,kJ
eout = qout+ out+ out, kJ/kg
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law - System’s EnergyFirst Law - System’s Energy
Energy Balance – The Change
WIthinEnergy change within the system, Esys = E2-E1
Internal energy change, U = U2 – U1
kinetic energy change, KE = KE2 – KE1
potential energy change, PE = PE2 – PE1
is the sum of
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – Energy ChangeFirst Law – Energy Change
Energy Balance – The Change
WIthin
kW ,PEKEUE sys
Esys = U+KE+PE, kJ
esys = u+ke+pe, kJ/kg
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – General Energy BalanceFirst Law – General Energy Balance
Energy Balance
Ein – Eout = Esys, kJ orein – eout = esys, kJ/kg or
Energy Entering a system
-
Energy Leaving a system
=
Change of system’s energy
kW,EEE sysoutin
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
First Law – General Energy BalanceFirst Law – General Energy Balance
Energy Balance –General system
outmassoutoutinmassinin EWQEWQ ,,
Qin + Win + Emass,in – Qout – Wout - Emass,out
qin + in + in – qout – out – out
= U+ KE+ PE, kJ
= u+ ke+ pe, kJ/kg
kW ,
PEKEU
TeacheTeacher r
ActivityActivity
TeacheTeacher r
ActivityActivity
Instructional Plan-ActivityActive Cooperative (group) LearningActive Cooperative (group) Learning StudentStudent
ActivityActivityStudentStudentActivityActivity
Write an energy balance representing the net interacting energies (agents of change) and the energy changes in the system
Write an energy balance in unit mass form, representing the net interacting energies (agents of change) and the energy changes in the system
Write an energy balance in unit time form or rate form, representing the net interacting energies (agents of change) and the energy changes in the system
Instructional Plan - AssessActive Cooperative (group) LearningActive Cooperative (group) Learning
Failure to complete task: re-teach then give different example
Otherwise, proceed with the next unit
Teacher-students Teacher-students ActivityActivity
Teacher-students Teacher-students ActivityActivity
If all ok, increase difficulty level to application, analysis, synthesis and evaluation
