This document contains definitions and explanations of key thermodynamic terms presented by a group of 7 students. It defines thermodynamics as the branch of science dealing with different forms of energy and their interconversions in physical and chemical processes. It then explains concepts such as system, extensive and intensive properties, state, equilibrium, process, heat, work, internal energy, enthalpy, entropy, Gibbs free energy, and Helmholtz free energy.

2. Thermodynamic
Terminologies

3. Group Members
 Hafiz M.Shakeel 11974
 Hamza Zaheer 11937
 Asad Bashir 11938
 Waris Ali 11950
 Ahmad Ali 11958
 M Yameen 11961
 M Altaf 11966

4. Contents
 Definition of thermodynamic
 System
 Types of system
 Extensive and Intensive Properties
 State of System
 State Function,Equlibrium
 Process
 Types of Process
 Heat and Work
 Internal Energy and change in Internal Energy
 Enthalpy and change in Enthalpy
 Entropy and change in Entropy
 Gibb’s Free Energy

5. Definition of Thermodynamics
 Thermodynamics is a Greek word which means flow of
heat in physical and chemical reactions
 Thermodynamics is a branch of science which deals with
study of different forms of energy and their
interconversions
 It deals with energy changes in physical and chemical
processes

6. System, surroundings and boundary
 System: A quantity of matter or a
region in space chosen for study.
 Surroundings: The mass or region
outside the system.
 Boundary: The real or imaginary
surface that separates the system
from its surroundings.

7. Type of system
(isolated system)
 Isolated system: neither mass
nor energy can cross the
selected boundary.
 Examples: coffee in a closed, well-
insulated thermos bottle

8. Type of system
(Closed system)
 Closed system: only
energy can cross the
selected boundary
 Examples: a tightly capped
cup of coffee

9. Type of system
(Open system)
 Open system :both
mass and energy can
cross the selected
boundary
 Example: an open cup of
coffee

10. Properties of a system
 Properties of a system is a measurable characteristic of a
system at equilibrium.
 Properties may be intensive or extensive.
 Intensive :Are independent of the amount of mass
eg: Temperature, Pressure, and Density.
 Extensive : varies directly with the mass e.g.:
mass, volume, energy, enthalpy.

11. State, Equilibrium and Process
 State: a set of properties that describes the
conditions of a system. E.g.. Mass m, Temperature
T, volume V
 State function
 It is defined as the property
whose value depends only upon
the state of the system and is
independent of the path by
which state has been reached

12. State, Equilibrium and Process
 Example: a person standing on the roof of the building has
a fixed value of potential energy and the potential of
person does not depend whether he has reached there by
stairs or lift. Ex. Potential energy, pressure, volume,
temperature, internal energy etc.
 Path function: It is defined as the property whose value
depends upon the path by which the state of the system has
been reached.
 Examples: Value of heat and work depend on path, hence
they are path functions

13.  Thermodynamics deals
with equilibrium
states.
 Equilibrium: A state of
balance.
 In an equilibrium state
there are no unbalanced
potentials (or driving
forces) within the system.
 Thermal equilibrium: If the
temperature is the same
throughout the entire
system.
State, Equilibrium and Process

14.  Mechanical
equilibrium: If there
is no change in
pressure at any point
of the system with
time.
 Phase equilibrium: If
a system involves
two phases and when
the mass of each
phase reaches an
equilibrium level and
stays there.
 Chemical
equilibrium: If the
chemical composition
of a system does not
change with time,
that is, no chemical
reactions occur.
State, Equilibrium and Process

15. State, Equilibrium and Process
 Process – change from
one equilibrium state
to another.
Process Property
held
constant
 isobaric Pressure
 Isothermal Temprature
 Isocohric Volume
 Isoentropic Entropy

16.  The prefix iso is often used to designate a process for which a
particular property remains constant.
 Isobaric process: A process during which the pressure P
remains constant.
 Pressure is Constant (ΔP = 0)
State, Equilibrium and Process

17.  Isothermal process: A
process during which the
temperature T remains
constant.
 Isochoric (or isometric)
process: A process during
which the specific volume v
remains constant
State, Equilibrium and Process

18.  Adiabatic process: a process that has no heat
transfer into or out of the system. It can be
considered to be perfectly insulated.

19. Types of Thermodynamics Processes
 Cyclic process: when a system in a given
initial state goes through various
processes and finally return to its initial
state, the system has undergone a cyclic
process or cycle.
 Reversible process: it is defined as a
process that, once having take place it can
be reversed. In doing so, it leaves no
change in the system or boundary.
 Irreversible process: a process that
cannot return both the system and
surrounding to their original conditions

20.  Spontaneous process
 It may also be defined as the process which can take
place by itself or initiation
 Which take place by itself
 Dissolution of salt in water
 Flow of water down a hill
 Which take place by initiation
 Combination of oxygen and hydrogen to form water
 Lighting of candle is initiated by ignition

21.  Non Spontaneous Process
 It is the process which cannot take place by itself or
initiation
 Examples:
 Flow of heat from cold body to hot body
 Flow of water up the hill
 Dissolution of sand in water

22. 5
 HEAT: is the energy transferred from one object to
another due to their temperature difference .
 It flows from high temperature point to low temperature
point.
 It is a path function.
 The magnitude of heat depends on the mass of matter
contained in a system.
 It is an extensive property.
1 cal = 4.184 Joule
HEAT (Q)

24. WORK (W)
24
 WORK:The energy transferred when an object is
moved against force.
 W = F x D
 Where: W = work in Joule F = Force in Newton D =
Distance in Meter
 Units of work are Nm=J
 It is an extensive property.
 It is a path function.

26. Some Thermodynamics Quantities
 Internal Energy
 Every system is associated with a definite amount of energy,
which is called its internal energy. It is donated by E or U
 It depends upon the various factors such as temperature,
pressure and chemical nature of the substance
 Change in Internal Energy
 The change in internal energy in a chemical reaction is the
difference in the internal energies of the products and the
reactants
 ∆E= E(products)-E(reactants)
 = Ep-Er

27.  Enthalpy(H)
 Enthalpy or heat content of a system may be defined as the
sum of the internal energy and the product of its pressure
and volume
 H =E + PV
 Change In Enthalpy
 It is the difference in the enthalpies of the products and the
reactants
 ∆H = H(products)- H(reactants)
= Hp- Hr
Some Thermodynamics Quantities

28.  Entropy
 It is a measure of the randomness or disorder
of the system
 The greater the randomness, the greater the
entropy
 Entropy of a crystalline substance is
minimum in the solid state and maximum in
the gaseous state
Some Thermodynamics Quantities

29.  Entropy
 It is represented by S
 It depends on temperature and increases with increase in
temperature
 The change in entropy is equal to heat absorbed
isothermally and reversibly during a process divided by
absolute temperature at which heat is adsorbed
 ∆ S = q rev/T
 Unit of entropy is JK-1
Some Thermodynamics Quantities

30. Entropy
 Melting of ice is an example of increasing entropy

32. Gibbs Free Energy (G)
 Energy available to do useful work at constant temperature and
pressure
 G = H – TS
 It is a state function
 The Gibbs Free Energy change for a given process is
 ∆G = ∆H - T∆S (at constant T and P)

33.  ∆G = ∆H − T ∆S
Sign of ∆H Sign of ∆S Sign of ∆G Type of
Process
negative positive negative
spontaneous at all
temperatures
positive negative positive
nonspontaneous at
all temperatures
positive positive (−) or(+)
Spontaneous if the
temperature is
high enough
negative negative (+) or(−)
Spontaneous if
the temperature
is low enough

34. Helmholtz Free Energy(A)
 Energy available to do work at constant volume and
 temperature
 A = E - TS
 It is a state function
 Helmholtz Free Energy for a given process is
 ∆A = ∆E - T∆S