BASICS OF THERMODYNAMICS BASICS OF THERMO ... - KEA

BASICS OF THERMODYNAMICSBASICS OF THERMODYNAMICSBASICS OF THERMO DYNAMICSBASICS OF THERMO DYNAMICS

Vikasana Vikasana -- Bridge Course 2012Bridge Course 2012 11

EEEnergy:Energy:1. Energy is an abstract physical1. Energy is an abstract physical

quantityquantity2. It can be measured only by 2. It can be measured only by y yy y

means of its effectmeans of its effect


HEATHEATHEATHEAT

Heat is a form of energyHeat is a form of energy


Effects of Heat:Effects of Heat:1. Expansion1. Expansion2. Rise in temperature2. Rise in temperaturepp3. Work done3. Work done


Work done:Work done:According to the law of According to the law of mechanics, energy is measured mechanics, energy is measured , gy, gyby amount of work doneby amount of work done


Th d iTh d iThermodynamics:Thermodynamics:Macroscopic science it deals with Macroscopic science it deals with bulk systembulk systemBranch of physics deals with inter Branch of physics deals with inter p yp yconversion of heat into other form conversion of heat into other form of energy (work)of energy (work)of energy (work)of energy (work)


Examples:Examples:Examples:Examples:1. When water in a container 1. When water in a container

t t b ili l t i t t b ili l t i starts boiling, plate covering starts boiling, plate covering the container starts moving up the container starts moving up and down.and down.

2. Rub your hands one against the 2. Rub your hands one against the y gy ganother for few second you will another for few second you will feel that your hands are feel that your hands are feel that your hands are feel that your hands are wormed.wormed.


Mechanical work of rubbing Mechanical work of rubbing hands is converted in to heathands is converted in to heat


Conclusion:Conclusion:It is possible to convert work in to It is possible to convert work in to heat or heat in to work.heat or heat in to work.


LORD LORD –– Kelvin Kelvin –– Named the Named the process as Thermodynamicsprocess as Thermodynamicsp yp y


In Latin thermodynamics means In Latin thermodynamics means ‘Motion of Heat’‘Motion of Heat’


Basic terms required to Basic terms required to understand thermodynamicsunderstand thermodynamicsyy


1.1. Closed system:Closed system:There is no mass transferred There is no mass transferred between the system and the between the system and the yysurroundings.surroundings.


02 . 02 . Open system:Open system:There will be both matter and There will be both matter and energy transfer across the energy transfer across the gygyboundary of the system.boundary of the system.


03. 03. Isolated system:Isolated system:There is neither matter nor There is neither matter nor energy transfer across the energy transfer across the gygyboundary of the system.boundary of the system.


04. 04. Thermodynamic system:Thermodynamic system:A certain amount of matter A certain amount of matter under investigation.under investigation.gg


05 05 S diS di05. 05. Surroundings:Surroundings:A given thermodynamic A given thermodynamic system interacts with all other system interacts with all other matter outside the system. matter outside the system. yyThe matter outside the system The matter outside the system is called the surrounding.is called the surrounding.is called the surrounding.is called the surrounding.


Th d i V i bl OR Th d i V i bl OR Thermodynamic Variables OR Thermodynamic Variables OR Thermodynamic coThermodynamic co--ordinates,ordinates,measurable quantities such as measurable quantities such as

i) pressurei) pressure ii) volume andii) volume and) p) p ))iii) temperature are called iii) temperature are called thermodynamic variables.thermodynamic variables.thermodynamic variables.thermodynamic variables.


Mechanical Equilibrium:Mechanical Equilibrium:There should be no unbalanced There should be no unbalanced forces between the various parts forces between the various parts ppof the systems or between the of the systems or between the system and the surroundingsystem and the surroundingsystem and the surroundingsystem and the surrounding


Thermal Equilibrium:Thermal Equilibrium:Thermal Equilibrium:Thermal Equilibrium:The temperature of every part of The temperature of every part of th t t b th t th t t b th t the system must be same as that the system must be same as that of surroundingsof surroundings

*A *B

TA = TC = TB = TD

*C *D


Chemical Equilibrium:Chemical Equilibrium:Chemical composition of the Chemical composition of the system stand remain fixed and system stand remain fixed and yydefinite.definite.


Thermodynamic Equilibrium:Thermodynamic Equilibrium:A thermodynamic system is said A thermodynamic system is said to be in complete equilibrium, it is to be in complete equilibrium, it is p q ,p q ,in in mechanicalmechanical, , thermalthermal and and chemical chemical equilibrium.equilibrium.chemical chemical equilibrium.equilibrium.


E ti f St tE ti f St tEquation of State:Equation of State:The equation relating the The equation relating the thermodynamic cothermodynamic co--ordinates is ordinates is called the equation of state.called the equation of state.qqEx:Ex:-- PV = RTPV = RT represents the represents the equation of state for a perfect gasequation of state for a perfect gasequation of state for a perfect gasequation of state for a perfect gas


Thermodynamic process:Thermodynamic process:T ki th th d i T ki th th d i Taking the thermodynamic Taking the thermodynamic system form one thermodynamic system form one thermodynamic state to another thermodynamic state to another thermodynamic state.state.Ex:Ex:-- Compression or Expansion of Compression or Expansion of

gasgasgasgas


I t l EI t l E E t E t Internal Energy:Internal Energy: Every system Every system (solid, liquid or gas) possess two (solid, liquid or gas) possess two types of energy.types of energy.

1. Potential Energy (PE)1. Potential Energy (PE)gy ( )gy ( )2. Kinetic Energy (KE)2. Kinetic Energy (KE)


* Kinetic Energy is due to motion * Kinetic Energy is due to motion f l l ith i th tf l l ith i th tof molecules with in the system.of molecules with in the system.

* Potential Energy is due to * Potential Energy is due to molecular configurations of the molecular configurations of the ggmolecules.molecules.

∴∴Total energy of the system Total energy of the system (E) = PE + KE(E) = PE + KE


(E) = PE + KE(E) = PE + KE

Internal energy of the Internal energy of the Real gasReal gasdepends on volume and depends on volume and temperature.temperature.pp


When temperature of the gas is When temperature of the gas is increased, the molecules move increased, the molecules move rapidly and randomly, there by rapidly and randomly, there by p y y, yp y y, yincreasing the K.Eincreasing the K.E


Increasing the KE in turn increases Increasing the KE in turn increases the internal energy of the gasthe internal energy of the gasgy ggy g


∴∴Internal energy can be taken as Internal energy can be taken as a measure of temperature.a measure of temperature.pp


I th d i th th I th d i th th In thermodynamics there are three In thermodynamics there are three laws:laws:1. Zeroth Law of thermodynamics1. Zeroth Law of thermodynamics2. First Law of thermodynamics, 2. First Law of thermodynamics, y ,y ,andand3. Second Law of thermodynamics3. Second Law of thermodynamics3. Second Law of thermodynamics3. Second Law of thermodynamics


Z th L f Th d iZ th L f Th d iZeroth Law of Thermodynamics:Zeroth Law of Thermodynamics:R.H FlowerR.H Flower formulated this law in formulated this law in 1931, By that time 1931, By that time II Law and Law and IIIILaw had already been formulated. Law had already been formulated. yyHence this law is called Zeroth Hence this law is called Zeroth Law. It is more basicLaw. It is more basicLaw. It is more basicLaw. It is more basic


Z th L f Th d iZ th L f Th d iZeroth Law of ThermodynamicsZeroth Law of ThermodynamicsStatement:Statement:-- If a two system A and If a two system A and B are separately in thermal B are separately in thermal equilibrium with third system C, equilibrium with third system C, q y ,q y ,then A and B are in thermal then A and B are in thermal equilibrium with each other.equilibrium with each other.equilibrium with each other.equilibrium with each other.


Explanation:Explanation:-- CTC

T TIf TIf TAA = T= TCC then A and C then A and C are in equilibrium.are in equilibrium.

ATA BTB

qqSimilarly if TSimilarly if TBB = T= Tcc then B and C are in then B and C are in equilibriumequilibriumequilibrium.equilibrium.∴∴According to zeroth law A and B According to zeroth law A and B are in thermal equilibrium with each are in thermal equilibrium with each are in thermal equilibrium with each are in thermal equilibrium with each otherother

if Tif T T T d Td T T T th th TT T TVikasana Vikasana -- Bridge Course 2012Bridge Course 2012 3434

∴∴ if Tif TAA = T= TC C and Tand TBB = T= TC , C , then then TTAA = T= TB B

Significance of zeroth Law:Significance of zeroth Law:zeroth law gives a measurable zeroth law gives a measurable quantity to decide whether two quantity to decide whether two q yq ysystems are in equilibrium or not.systems are in equilibrium or not.


Fi t L f Th d iFi t L f Th d iFirst Law of ThermodynamicsFirst Law of ThermodynamicsStatement:Statement:-- Heat energy given to Heat energy given to a system is equal to the sum of the a system is equal to the sum of the increase in internal energy and increase in internal energy and gygythe external workdone by the the external workdone by the system.system.system.system.


Explanation:Explanation:Explanation:Explanation:dQ = du + dwdQ = du + dw

du du change in internal energychange in internal energydw dw work donework donedQ dQ Heat energy given to a Heat energy given to a

systemsystemsystemsystem


Si iSi iSign convension:Sign convension:* When heat is given to a system * When heat is given to a system

‘dQ’ is taken as +ve.‘dQ’ is taken as +ve.* If the heat is drawn from the * If the heat is drawn from the

system dQ is taken as system dQ is taken as ––ve.ve.


Ph diPh diPhase diagram:Phase diagram:A graphical representation of A graphical representation of variation of pressure (P) and variation of pressure (P) and temperature (T) at constant temperature (T) at constant p ( )p ( )volume (V).volume (V).


I di t di (PI di t di (P V di )V di )Indicator diagram (PIndicator diagram (P--V diagram):V diagram):The graphical representation of The graphical representation of variation of variation of PressurePressure with the with the Volume Volume of the system is called Pof the system is called P--V V yydiagram or diagram or Indicator diagramIndicator diagram


pp--v diagram or Indicator diagramv diagram or Indicator diagram

yy--axisaxis A(pA(p11vv11))

pppp

B(B( ))B(pB(p22 vv22))

Vikasana Vikasana -- Bridge Course 2012Bridge Course 2012 4141v xv x--axisaxis

Indicator diagram help us to Indicator diagram help us to determine work done by the gas or determine work done by the gas or on the gas during thermodynamic on the gas during thermodynamic g g yg g yprocessprocess


Applications of first law of Applications of first law of ThermodynamicsThermodynamicsyy


1.1. Isothermal process:Isothermal process:It is a thermodynamic It is a thermodynamic It is a thermodynamic It is a thermodynamic process that takes place at process that takes place at constant temperatureconstant temperatureconstant temperatureconstant temperature

dQ = du + dwdQ = du + dwdu = 0du = 0dQ = dwdQ = dwQQ

Ex: Ice is converted into Ex: Ice is converted into water at 0water at 0°°CC


water at 0water at 0 CC

2 2 Adi b ti Adi b ti 2. 2. Adiabatic process:Adiabatic process:Heat can neither enters the Heat can neither enters the system nor leaves the system system nor leaves the system dQ = 0dQ = 0

du = du = -- dw.dw.Ex: Bursting of cycle tyre.Ex: Bursting of cycle tyre.Ex: Bursting of cycle tyre.Ex: Bursting of cycle tyre.


3. 3. Isobaric process:Isobaric process:The thermodynamic process that The thermodynamic process that The thermodynamic process that The thermodynamic process that takes place at constant takes place at constant pressurepressurenone of the quantities du , dw and none of the quantities du , dw and dQ is zero.dQ is zero.Ex: 1) Heating water in atmospheric Ex: 1) Heating water in atmospheric pressure.pressure.pressure.pressure.

2) Conversion of ice into water.2) Conversion of ice into water.


4. 4. Isochoric process:Isochoric process:Th th d i th t Th th d i th t The thermodynamic process that The thermodynamic process that takes place at constant volumetakes place at constant volume

dw = 0dw = 0dQ = du + p.dvdQ = du + p.dvpp∴∴dQ = dudQ = du

Ex:Ex: When ice melts, the change in When ice melts, the change in Ex:Ex: When ice melts, the change in When ice melts, the change in volume is negligeble.volume is negligeble.


Reversible process:Reversible process:Th th t b t d Th th t b t d The process that can be retraced The process that can be retraced in the reverse direction, so that all in the reverse direction, so that all the changes occurring in the the changes occurring in the direct process are reversed.direct process are reversed.ppEx:Ex:-- 1. Evaporation of water1. Evaporation of water

2. Condensation of vapour2. Condensation of vapour2. Condensation of vapour2. Condensation of vapour3. Ice changing into water.3. Ice changing into water.


I ibl I ibl Irreversible process:Irreversible process:The process that cannot be The process that cannot be retraced back in the reverse retraced back in the reverse direction.direction.Ex:Ex:-- 1. Sudden expansion of gas1. Sudden expansion of gas

2. Heat produced by friction2. Heat produced by friction2. Heat produced by friction2. Heat produced by friction


Documents

BASICS OF THERMODYNAMICS BASICS OF THERMO ... - KEA